OCT 5 1905 YV\ . \ LIBRARY OF THE UNIVERSITY OF CALIFORNIA. Class ROCK EXCAVATION METHODS AND COST ALBERT POWERS GILLETTE M. Am. Soc. C. E., M. Am. InU. M. E. E. M. School of Mines, Columbia University Late Assistant New York State Engineer NEW YORK . C. CLARK 13-21 Park Row 1904 MIMING* Copyright, 1904, By M. C. CLARK. PREFACE. The value of the mineral products of America annually exceeds $1,000,000,000. For explosives alone the sum of $20,000,000 is expended each year, and it is well within limits to say that fully twice as great a sum is paid out to drillers and blasters. When we consider the labor, the power and the powder required to mine and to quarry products in the aggregate so enormously valuable, we can not fail to be impressed with the scantiness of literature on the economics . of rock excavation. A dozen years ago, when called upon to estimate the cost of some open cut rock excavation, I was astonished to find no text book that in the least served to guide me. I subsequently learned also that most of the mat- ter to be found in the few books on blasting was either theoretic or too meagre to be of material value. What was true then has unfortunately remained true. In the preparation of this volume, it was my original in- tention to give only condensed cost data on rock excava- tion including in that term, quarrying, open cut work, trenching, tunneling, and underground excavation; but, as the writing progressed, it become more and more apparent that methods of doing work and "tricks of the trade" should occupy an important part of the book to make it at all satis- factory. I saw that my object should be not merely to fur- nish data whereby an inexperienced man might predict the cost of rock work with at least tolerable accuracy, but that it should be my aim also to indicate to the experienced man- ager how and where savings in the cost of production may be effected. Taking my own notes and records of cost as a basis, I have added so extensively to them by correspondence that the reader will find not a little on costs that has never ap- peared in print before. In addition, I have abstracted scores of pages of facts and figures from the volumes of scientific 137438 iv PREFACE. and engineering periodicals, due acknowledgement of which appears throughout the text. While the scope of the book is wider than at first sight ap- pears desirable, since it includes quarrying, open cut excava- tion, trenching, subaqueous excavation, tunneling and un- derground excavation, still it should be remembered that the main elements of cost are of much the same quality, and that the differences are principally those of quantity. Thus, it may require eight feet of drill hole per cubic yard of tun- nel excavation as compared with half a foot for open cut work. The cost of drilling per cubic yard is obviously much greater in the tunnel than in the open cut, but the methods of drilling and the cost per foot of drill hole may be prac- tically identical. There is, indeed, much in common in all classes of rock excavation in spite of many detailed differ- ences. For these reasons, and because my training and exper- ience have been both in mine and in quarry work, I have chosen for this book the broad scope indicated by its title. I am well aware of defects in the execution of my plan, but trust, however, that suggestions as to sources of information now unknown to me, and original data will be sent to me by readers who are interested in the progress of the art of economic excavation. There is probably not a man of any considerable experience who could not add his quota of valuable information, if he would ; and, on the other hand, there is not one of us who "knows it all 1 ' except the fellow who really knows very little. Men engaged in mining can learn from those whose excavation work is in the open air, and the reverse holds equally true. The mining engineer profits to-day by inventions developed under the direction of civil engineers, and thousands of civil engineers in turn are indebted to mining engineers. It is well for us not to forget that the first air drill, so useful in mining, was the develop- ment of work in a railway tunnel, and that the first railway was the development of work in a mine. New York, Sept., 1904. HALBERT P. GILLETTE. CONTENTS. PAGE CHAPTER L Rocks and Their Properties i Rock-forming Minerals . . I Hardness 2 Rock Species 3 Joints 4 Veins and Beds 5 Shale 6 Sandstone 6 Limestone 6 Granite 7 Porphyry 7 Trap 8 Weight and Voids 8 Tables of Weights of Rock 9 Measurement of Rock.... n CHAPTER II. Methods and Cost of Hand Drill- ing 13 Kinds of Hand Drills.... 13 Theory of Drilling 13 Hammer Drilling 17 One-Hand vs. Two-Hand Drilling 18 Churn Drilling 18 Cost of Hammer Drilling. 19 Cost of Churn Drilling... 22 Hand-Drill Bits 23 Sharpening Hand Drills.. 26 Sharpening Machine Drills 29 CHAPTER III. Machine Drills and Their Use... 31 Machine Drill Mechanism. 31 Sizes of Air Drills 32 Handling Drill on Tripod. 34 Use of Column or Bar. ... 40 Use of Water in Drilling. 43 Other Types of Machine Drills 45 PAGE CHAPTER IV. Steam and Compressed Air Plants. 47 Heat Energy and Horse Power 47 The Work of Compression 49 Tests of Air Consumed by Drills Si Tests of Air Consumption at the Rose Deep Mine. 55 Tables of Air Consump- tion in Catalogs 56 Steam Consumption in Terms of Air Consump- tion 58 Efficiency of Steam Pipe Line 60 Flow of Air Through Pipes 63 Fuel and Boiler Efficiency. 65 Merits of Compressed Air 68 Efficiency of the Jerome Reservoir Plant 69 Gasoline Air Compressors. 70 CHAPTER V.The Cost of Machine Drilling. ... 72 Cost Factors 72 Percentage of Lost Time. 73 Results of Drilling Con- tests 78 Rule for Estimating Feet Drilled per Shift 79 Rates of Drilling in Dif- ferent Rocks 82 Average Footage Drilled per Shift 84 Cost of Sharpening Bits. 85 Cost of Drill Repairs 86 Plant Rental 86 Cost of Installing a Com- pressor Plant 87 VI CONTENTS. PAGE Cast of a Large Com- pressor Plant 88 Cost of Operating Drills. . 89 Cost of Drilling Blast Holes with Well Drill- ers 90 Cost of Drilling with Elec- tric Drills 93 CHAPTER VI. Cost of Diamond Drilling 95 Price of Diamonds 96 Water Required 96 Price of Diamond Drills.. 97 Cost of Drilling in Vir- ginia 97 Cost of Drilling in Lehigh Valley 101 Cost on Croton Aqueduct. 102 Cost of Hand Drilling in Arizona 103 References on Costs 105 CHAPTER VII. Explo- sives 106 The Action of Gases 106 Black Powder 108 Properties of Good Pow- der 109 Dynamite and Nitroglycer- ine no Varieties of Dynamite.... in The Absorbent 114 Weight of Dynamite 115 Thawing Dynamite 116 How to Thaw Dynamite. 119 Testing Dynamite for Safety 121 Blasting Gelatin 121 Judson Powder 122 Joveite 122 CHAPTER VIII. Charg- ing and Firing 124 PAGE Kind of Explosive to Use. 124 Charging Black Powder. . 126 Charging Dynamite 127 Firing by Electricity 131 Misfires 134 Methods of Firing 136 Safety Fuse 136 Caps I3 6 Electric Detonators 139 CHAPTER IX. - Methods of Blasting 141 The Theory of Blasting. . 141 Placing Drill Holes 146 Springing Holes 147 Blasting with Powder and Dynamite Together .... 149 Large Chamber Blasts 150 Blasting Hardpan 156 Blasting Piles and Stumps 160 Ice Blasting 162 Boulder Blasting 162 CHAPTER X. Cost of Loading and Transport- ing Rock 164 Cost of Loading by Hand. 164 Cost of Handling Crushed Stone 165 Cost of Handling with Derricks 166 Cost of Loading with Steam Shovels 168 Cost of Steam Shovel Work in Iron Ore 173 Cost of Hauling in Wheel- barrows 176 Cost of Hauling in Carts and Wagons 177 Hauling qn Stone Boats.. 181 Cost of Hauling in Dump Cars . . 182 CONTENTS. Vll PAGE CHAPTER XL Quarrying Stone 184 General Considerations . . . 184 Joints 186 Plug and Feathers 187 Cost of Plug Drilling by Hand 189 Cost of Pneumatic Plug Drilling 189 The Quarry Bar 191 Broaching 192 The Gadder 192 The Channeler 193 Cost of a Quarry Derrick. 196 Knox System of Blasting. 197 Cost of Quarrying by Knox System 198 Cost of Quarrying Dimen- sion Sandstone 202 Quarrying by Water Cush- ion Blasts 203 Granite Quarrying 204 Quarrying Massive Granite 207 Cost of Quarrying Granite 208 Cost of Quarrying Sand- stone Rubble 211 Cost of Quarrying Lime- stone 212 CHAPTER XlLOpen Cut Excavation 214 General Considerations . . . 214 Excavation in Benches... 214 Spacing Holes 216 Cost of Quarrying Trap for Macadam 218 Cost of Quarrying and Crushing Limestone. . . . 220 Cost of Pit Mining, Brews- ter, N. Y 221 Cost of Excavating Gneiss 222 Cost of Excavating Sand- stone and Shale 223 PAGE Cost of Railroad Excava- tion in Tennessee 225 Cost of Blasting and Sledging Boulders 232 Summary 236 Table of Explosives and Drilling per Cu. Yd... 237 CHAPTER XIII. Meth- ods and Costs on the Chicago Drainage Canal 238 General Conditions 238 Excavating Very Tough Clay 239 Excavating Hardpan 239 Incline and Tipple 243 Cost by Lidgerwood Cable- ways 244 Cost by Hullett-McMyler Cantilever Crane 250 Cost by Hullett-McMyler Derrick 252 Cost by Geraldine Double- Boom Derrick 254 Cost by Brown Cantilever Crane 255 Cost by Car Hoists 258 Summary of Costs 261 Cost of Channeling 262 Cost of Drilling 264 Steam Shovel Output 265 CHAPTER XIV. Cost of Trenches and Subways. 267 General Considerations . . 267 Method of Charging Holes 268 Blasting Mats 269 Cost of Drilling and Blast- ing 270 Cost of N. Y. Subway Work 273 Vlll CONTENTS. PAGE CHAPTER XV. Subaque- ous Excavation 277 Cost of Excavation, De- troit River 277 Cost of Harbor Excava- tion, Oswego, N. Y.... 284 Cost of Excavating Black Tom Reef, N. Y 287 Cost of Undermining Flood Rock, N. Y 289 The Derby Tubular Drill Bit 290 Drilling and Dredging Way's Reef, N. Y 291 Cost of Excavation, Eagle Harbor, Mich 292 Cost of Excavation, Pier 14, N. Y 293 Drilling and Dredging Boulders 295 Drilling in San Francisco Harbor 296 CHAPTER XVI. -Cost of Railway Tunnels 297 The American System. . . . 297 A Device for Laying Dust with Water 299 The Gallitzin Tunnel 299 Cost of Wabash R. R. Tunnels 302 Cost of the Stampede Tun- nel 307 Cost of Mount Wood and Top Hill Tunnels 313 Cost of a Hand-Driven Tunnel on the B. & O. . 315 Cost of New Croton Tun- nel Work 318 Cascade Tunnel Data 323 Kellogg Tunnell Data 325 Pryor Gap Tunnel Data. . 326 Busk Tunnel Data 327 PAGE Sutro Tunnel Data 328 Musconetcong Tunnel Data 329 'A Tunnel through the Pali- sades, N. J 330 Methods Used in the Te- quixqueac Tunnel 331 The Simplon Tunnel 332 Cost of a Tunnel near Peekskill, N. Y 336 Cost of Lining Tunnels.. 338 CHAPTER XVII. Cost of Drifting, Shaft Sinking and Stoping 34 1 Definitions 34 1 Cost of Tunneling, Mel- ones Mine 343 Cost of Tunneling, Hogs- back Mine 345 Cost of Sinking and Stop- ing at the Utica Angels 346 Cost of Sinking and Drift- ing at the Lincoln Gold Mine 347 Cost of the Newhouse Tunnel 35o Cost of Sinking and Drift- ing at the Homestake Mine 353 Cost of Drifting and Stop- ing at Cripple Creek. . . . 356 Cost of Drifting and Stop- ing at Rossland, B. C. . 359 Cost of Development and Stoping, Centre Star Mine, B. C 361 Cost of Shaft Sinking at the Pioneer Mine 363 Cost of Two Three-Com- partment Shafts 365 Lost of Mining, Douglas Island, Alaska 366 ROCKS AND THEIR PROPERTIES. Rock-forming Minerals. All rocks are aggregates of one or more minerals or the disintegrated products of minerals. A mineral is an inorganic body having a definite chemical composition, as quartz, common salt, mica, and the like. There are about 1,000 distinct species of minerals, but for- tunately the common rock-forming minerals number less than 30; and of these 30 perhaps 15 should be recognized at sight by everyone who aims to become an expert in rock excavation. A small cabinet of the common species of minerals may be purchased for a few dollars from any of the dealers whose advertisements may be found in the mining and civil engi- neering journals. Such a cabinet when studied with the aid of a small book on mineralogy will enable one to undertake the work of rock excavation intelligently. It is often said that "a little knowledge is a dangerous thing"; but a little knowledge of fundamental principles, whether of geology or of any other of the physical sciences, is exactly the oppo- site of dangerous. A little knowledge of a few scientific facts, it is true, often leads to incorrect rules or generaliza- tion ; but a knowledge of correct rules and fundamental prin- ciples, based upon the observation and study of many facts by experts, is the kind of little knowledge that no man can afford to be without. Thus, for example, geologists classify rocks according to their origin into two great classes, (i) sedimentary or stratified, and (2) crystalline, or igneous. A contractor, who had lost many thousand dollars on some rock excavation in the northern part of New York, once told me that he attributed his loss to a lack of knowledge of 2 ROCK EXCAVATION METHODS AND COST. geology. His previous experience had been confined to the shales and sandstones of Pennsylvania. When he came to estimate the cost of excavating a granitic rock he made due allowance for its greater hardness and toughness as affecting the speed of drilling ; but he failed to consider the fact that the absence of lines of stratification in the granite would necessitate placing drill holes much closer together than in shale or sandstone. The result was that not only the cost of drilling but the cost of explosives per cubic yard of granite excavation was practically double what he had counted upon. Every mining man can cite many striking instances to show how ignorance of the elementary facts of geology and petrology have lead to serious underestimates of the cost of tunneling, shaft sinking and stoping. It is true that where an engineer, contractor or miner works all his life in one locality he becomes so expert in his knowledge of the meth- ods and cost of rock excavation that he sees little prac- tical value to himself in a knowledge of minerals, rocks or geologic principles. But when, possibly late in life, he goes to a new field of action, he is likely to lose his reputation, if not his money, through lack of a "little knowledge" of the fundamental principles of rock formation. The science which he has regarded as being too theoretical for him might have saved him had he possessed even a little of it. I therefore repeat that the man who aims to become an expert in all kinds of rock excavation, should first learn to know the common species of minerals at sight, or by means of the simple tests described in books on mineralogy. It is beyond the province of this book, however, to describe rocks and rock forming minerals. There are several excel- lent books on that subject, with one or more of which the rock excavator should be familiar. Hardness. The resistance to scratching or cutting is termed hardness. Diamond is the hardest mineral known, as it will scratch all others. Talc is one of the softest miner- als. Mineralogists use a scale of hardness as follows : ROCKS AND THEIR PROPERTIES. 3 1. Talc. 6. Feldspar. 2. Gypsum. 7. Quartz. 3. Calcite. 8. Topaz. 4. Fluorite. 9. Corundum. 5. Apatite. 10. Diamond. The sharpest point of a steel knife will not scratch quartz, but under considerable pressure will scratch feldspar. A very slight pressure on the knife will scratch talc or gypsum ; in- deed the finger nail will serve to scratch them. The test of hardness often serves to distinguish one mineral from an- other ; for instance, iron pyrites and copper pyrites are simi- lar in color, but while copper pyrites can be scratched with a knife, iron pyrites cannot. To distinguish sandstone from limestone it is often necessary merely to draw a sharp corner of the stone across a pane of glass. If a scratch is left in the glass the stone can not be pure limestone, since calcite, which has a hardness of 3, is the mineral forming limestone. Impure limestone may be a mixture of fine grains of quartz and calcite; but after a little experience in testing stones and minerals the eye will aid to such a degree in determining the species that the test of hardness becomes a very reliable one in many cases. Hardness of course affects the speed of drilling in rock, although to a less degree than toughness. A tough rock is one that will stand a hard blow without splintering. Win- dow glass is quite hard, almost as hard as tempered steel, but it is not very tough. Sandstone is hard, so far as its individual grains are concerned, but is often drilled with ease, since it usually lacks in toughness. Trap rock is both hard and tough, and makes drilling difficult, besides dulling the drill rapidly. Rock Species. Rocks may be classified as: (i) Sedi- mentary; (2) igneous, and (3) metamorphic. Sedimentary rocks have been deposited originally from suspension or solution in water; thus sand hardened into rock becomes sandstone ; clay becomes shale or slate ; gravel becomes con- 4 ROCK EXCAVATION METHODS AND COST. glomerate or pudding stone; wood fiber becomes peat or coal; shells of minute forms of sea life form limestone, or possibly lime in solution crystallizes out as does rock salt. The chief characteristic of sedimentary rocks is that they lie in beds or layers, one upon the other, often not cemented to- gether in the slightest degree; and even where they appear to be solid and massive they can usually be split into slabs by wedging. The igneous rocks have at one time been in a molten condition, and include the traps, porphyries, most granites, and all volcanic lavas, etc. Igneous rocks are often exceed- ingly tough, hard to drill, and are apt to break out in very ir- regular masses, sometimes of huge size and in other cases of too small a size to make cut stone masonry. The metamorphic rocks, may be said to be a "cross be- tween" the sedimentary and the igneous rocks, for they have been formed by chemical and physical changes in sedi- mentary rock under the influence of heat, water and pres- sure. For example, a dike of molten rock rising through a fissure in shale heats the surrounding shale to such a degree that, in the presence of confined water, the shale dissolves or melts, and, when it solidifies by subsequent cooling, a gneiss is produced. Some granites are known to have been made in this way by what is called metamorphic action. Marble is metamorphosed limestone, and quartzite is meta- morphosed sandstone. Joints. All rocks are more or less split up along vertical or nearly vertical planes termed, joints, which greatly assist in the quarrying. Joints are the results of stress, due to shrink- age of the earth's crust upon cooling. This shrinkage has produced great compression in some places and tension in others, resulting in cracking of the rock masses at more or less regular intervals. In limestone and in close grained shales the joints are often regular but so close as to be invisible until revealed by frac- ture or by weathering. In coarse grained sedimentary rocks, ROCKS AND THEIR PROPERTIES. 5 the joints are apt to be more open and irregular, running into one another or branching. In sedimentary, rocks there are generally two sets of joints running approximately at right angles, known as the dip-joints and the strike-joints. The "dip" of the rock is the angle that its bedding planes make with a horizontal plane. The "strike" is the line of intersection between an in- clined plane and a horizontal plane ; thus, if a sheet of car J- board be held at an incline in a basin of water, the line of the water surface along the face of the cardboard is the "strike/' Since a quarry is usually worked to the dip of the rock, the strike joints, or "backs," form clean cut faces in front of the workmen as they advance; while the dip joints, or "cut- ters" form the side faces of the benches in the quarry. Thus it happens that in some sedimentary stone quarries, nature has provided blocks of stone, practically loose on all six faces ; but, as a rule, the joints are so irregularly spaced as to require much plug and feathering work. Igneous rocks, while not possessing bedding planes, also have nearly vertical joints, cutting at about right angles in most cases ; but these joints are seldom so regular in spacing as in sedimentary rocks. In certain trap rocks the joints cause the rock to break out in vertical columns, often of great regularity; and in some cases the joints are so close together that upon firing the blast the rock comes down in chunks not much larger than a man's head, even where very little explosive is used ; but, on the other hand, certain traps break up in very large chunks on blasting. Veins and Beds. Iron ores and coal occur for the most part in beds that originally were nearly horizontal, since they are of sedimentary origin. They are, or at one time have been, overlaid by sedimentary rocks. Veins carrying the ores of the valuable metals are in some cases fissures or cavities that have been filled by hot waters carrying minerals in solution. These fissure veins exist in both sedimentary and in igneous rocks, but as a rule near 6 ROCK EXCAVATION METHODS AND COST. dikes or sheets of igneous rocks that were at one time in a molten state. Limestone. As its name implies, limestone is the rock from which lime is made. It is seldom pure (calcite), but usually contains more or less clay and often silica. By dis- solving some powdered limestone in nitric acid the amount of impurity may be roughly ascertained, for neither clay nor quartz is dissolved by the acid. In some cases it will be found that there is less limestone than clay in the so-called limestone. Due to the presence of impurities, few rocks vary more in compactness and appearance than does lime- stone. When pure, it is hard and crystalline; but friable, chalky deposits of limestone are not uncommon. The com- mon color is a gray, or a blue gray, passing into white. Marble is a pure metamorphosed limestone. Dolomite is a magnesian limestone in which part of the lime has been re- placed by magnesia. Sandstone. As its name implies, sandstone is sand ce- mented together. The cementing material is commonly silica or iron oxide (iron rust). When cemented by silica the rock is apt to be very tough and far more durable than when cemented by iron rust; and is consequently more diffi- cult to drill. Sandstone generally contains enough iron oxide to give it a red or brown color. White sandstone, as well as dark blue, is quite common. Sandstone often con- tains enough clay to make it difficult to classify it; in such cases it is usually very fine grained and may be mistaken for slate, especially when it splits into thin slabs. Shale. Shale is really a baked clay or mud, generally yellow, brown or black in color, and easily split into leaves. Under great pressure shale has often been converted into slate in which the pressure has forced the long particles into a position perpendicular to the line of pressure, and im- parted lines of cleavage entirely independent of the original bedding planes of the shale. Shales often contain silica and lime to a degree that makes their classification puzzling. Dry ROCKS AND THEIR PROPERTIES. 7 clay upon absorbing water swells, so that clays which have been only partly baked into shale absorb water upon ex- posure and go to pieces ; moreover, the swelling often causes great difficulty in tunnelling or shaft sinking, since the force developed by absorbing water may crush or displace the tim- bers used in lining. On the other hand well hardened shales do not swell upon exposure and, if not exposed to great changes in tempera- ture, have a long life. It often becomes a very important economic question to decide whether a tunnel through shale should be lined with concrete or masonry, and many civil engineers have made serious blunders through lack of scien- tific knowledge of the properties of the different shales. If an engineer has had experience only with half-baked shales, he is apt to line with masonry every permanent tunnel that he builds in shale, regardless of the kind of shale; while, on the other hand, an engineer whose experience has been with well baked shales may err by failing to provide lining for tunnels in half-baked shales. I could mention several instances of economic errors of this kind, but I have perhaps emphasized sufficiently the advantage possessed by the en- gineer who has a good working knowledge of rocks and of geology. Granite. Granite is composed of quartz, feldspar and mica; the quartz acting as the cement binding the whole together in a crystalline mass. When the percentage of feldspar is large the granite is said to be porphyritic. The mean specific gravity is about 2.65. Porphyry. Porphyry is an overworked name applied by miners to almost any igneous rock whose real name they do not know. Quartz-porphyry, or felsite, is composed of quartz and feldspar; when the quartz is visible as well- marked grains or crystals, the rock is generally called quartz- porphyry ; but when the quartz and feldspar are so intimately mixed as not to be readily distinguished, the term felsite is more often used. 8 ROCK EXCAVATION METHODS AND COST. Trap. Trap is another overworked name, that is com- monly applied to fine grained rocks of igneous origin. Among the trap rocks are : Diabase, diorite, basalt, etc. The trap rocks usually have irregular joints, and, while on ac- count of their toughness they may be excellent material for macadam, they are seldom fit for building purposes, except when crushed and used in concrete. The Hudson River trap, diabase, has a specific gravity of about 2.95. Weight and Voids. Civil engineers commonly measure rock excavation by the cubic yard in place before loosen- ing, whereas mining engineers generally use the ton of 2,000 pounds, as the unit of rock and ore measurement. In view of this fact it would be well were the specific gravity of the rock given by every engineer who publishes data on any particular kind of rock excavation or mining. Then, too, it often happens that broken rock is purchased by the ton even for civil engineering work, or by the cord of loosely piled rubble for architectural work, thus emphasizing the im- portance of stating not only the specific gravity but the percentage of voids. The specific gravity of any material is the quotient found by dividing its weight by the weight of an equal bulk of water. Water, therefore, has a specific gravity of I ; a cubic foot of any substance like granite, having a specific gravity of 2.65, weighs 2.65 times as much as a cubic foot of water. A cubic foot of water weighs 62.355 Ibs., or prac- tically 62.4 Ibs. ; hence a cubic foot of solid granite weighs, 2.65 X 62.4 = 165.3 lbs - When any rock is crushed or broken into fragments of tolerably uniform size it increases in bulk, and is found to have 35 per cent, to 55 per cent, voids or inter-spaces, de- pending upon the uniformity pf the fragments and their an- gularity. Rounded fragments, like pebbles, pack more closely together than sharp-edcred or angular fragments. A tumbler full of bird shot has about 36 per cent, voids, and it is pos- sible to hand-pack marbles of uniform size, so that the voMs ROCKS AND THEIR PROPERTIES. 9 are only 26 per cent. Obviously, if small fragments of stone are mixed with large fragments the voids are reduced. Pit sand ordinarily has 35 to 40 per cent, voids. Hard broken stone from a rock crusher has about 35 per cent, voids if all sizes are mixed and slightly shaken down in a box ; whereas, if it is screened into several sizes, each size has about 45 to 48 per cent, voids. A soft and friable rock-like shale breaks into fragments having a great range in size, from large chunks down to dust; and, as a consequence, such soft broken rocks have a much lower percentage of voids than the tougher rocks. The following table shows the swelling of rock upon breaking: Voids 30% 35% 40% 45% 5o% 55% No. of cu. yds. (loose incas-^ ure) made by each cu. yd. [-1.43 1.54 1.67 1.82 2.00 2.22 of solid rock. . . J Hard rock when blasted out in large chunks and thrown into cars or skips may ordinarily be assumed to have from 40 to 45 per cent, voids, hence I cu. yd. of hard solid rock or- dinarily makes 1.67 to 1.82 cu. yds. of broken, or crushed rock. Tables of Weights of Rock. Tables I. and II. will be found useful for computing the weight of solid or broken rock from the specific gravity. Thus, suppose it is desired to as- certain the weight of a solid cubic yard of granite, also the weight of a cubic yard of crushed granite having about 40 per cent, voids. In Table I. it is seen that granite has a spe- cific gravity of 2.55 to 2.86; assuming 2.7 as an average and turning to Table II., we find that a rock having a specific gravity of 2.7 weighs 4,546 Ibs. per cu. yd. solid, or 2,727 Ibs. per cu. yd. when broken up, so that 40 per cent, of the masb is voids. io ROCK EXCAVATION METHODS AND COST. TABLE I. SPECIFIC GRAVITY OF COMMON MINERALS AND ROCKS. Apatite 2.923.25 Limestone 2.352.87 Basalt 3.01 Magnetite, Fe 3 C)4 4.9 5.2 Calcite, CaCO 3 2.5 2.73 Marble 2.082.85 Cassiterite, SnO 2 6.47.1 Mica 2.753.1 Cerrusite, PbCO, 6.466.48 Mica Schist 2.5 2.9 Chalcopyrite, CuFeSz. 4.1 4.3 Olivine 3.33 3.5 Coal, anthracite 1.3 1.84 Porphyry 2.5 2.6 Coal, bituminous 1.21.5 Pyrite, FeS 2 4.835.2 Diabase 2.6 3.03 Quartz, SiO 2 2.5 2.8 Diorite 2.92 Quartzite 2.6 2.7 Dolomite,CaMg(CO 3 ) 2 2.8 2.9 Sandstone 2.0 2.78 Feldspar 2.44 2.78 Medina ... 2.4 Felsite 2.65 Ohio 2.2 Galena, PbS 7.257.77 Slaty 1.82 Garnet 3.154.31 Shale 2.4 2.8 Gneiss 2.62 2.92 Slate 2.5 2.8 Granite 2.55 2.86 Sphalerite, ZnS 3.9 4.2 Gypsum 2.3 3.28 Stibnite, Sb 2 S 3 4.5 4.6 Halite (salt), NaCl. . 2.1 2.56 Syenite 2.272.65 Hematite, Fe 2 O 3 4.5 5.3 Talc 2.562.8 Hornblende 3.05 3.47 Trap 2.6 3.0 Limonite, Fe 3 O4(OH) e 3.6 4.0 TABLE II. t C i_ s g u IT; sal '+ Q .H o,*d Weight in Lbs. per cu. yd. when '* .'Ijs" .'IjS* _Voids^are 1.0 62.355 2.0 1247 2.1 130.9 2.2 137.2 2.3 1434 2.4 1497 2-5 155-9 2.6 162.1 2.7 168.4 2.8 174.6 2.9 180.9 3.0 187.1 3-1 193-3 3-2 199-5 3-3 205.8 3.4 212.0 3-5 218.3 On the other hand, if the weight per cubic yard of the loose broken stone is known (as is often the case), and if 30% 35% 40% 45% 50% 1,684 1,178 1,094 1,010 926 842 3,367 2,357 2,187 2,020 1,852 1,684 3,536 2,475 2,298 2,121 1,945 1,768 3,704 2,593 2,408 2,222 2,037 1,852 3,872 2,711 2,517 2,323 2,130 1,936 4,041 2,828 2,626 2,424 2,222 2,020 4,209 2,946 2,736 2,525 2,315 2,105 4,377 3,064 2,845 2,626 2,408 2,189 4,546 3,182 2,955 2,727 2,500 2,273 3,300 3,064 2,828 2,593 2,357 4882 3,4i8 3,174 2,929 2,685 2,441 3,536 3,283 3,030 2,778 2,526 5',2i9 3,653 3,392 3,131 2,871 2,609 5.388 3,77i 3,502 3,232 2,963 2,694 5,556 3,889 3,6n 3,333 3,056 2,778 5,724 4,007 3,72i 3,434 3,148 2,862 5,893 4,125 3,830 3,535 3,241 2,947 ROCKS AND THEIR PROPERTIES. 11 the specific gravity has been determined by a test, then Table II. can be used to find the per cent, of voids in the broken stone. Thus, if a given sandstone has been found to have a specific gravity of 2.4, and .upon shipping in cars it has been found to weigh 2,200 Ibs. per cu. yd., measured loose in the car box, then from Table II., it is seen that about 45 per cent, of the mass of broken stone is voids. Measurement of Rock. Sedimentary rock quarried in slabs that are corded up carefully by hand may have 30 per cent., or less, voids, which makes it evident that a contractor in buying rock by the cord should be careful to specify that it be packed closely and not dumped in piles helter skelter before measurement. In buying rock by the "cord" there is another precaution to be taken, and that is to specify how many cubic feet constitute a cord. A cord of wood is 4 X 4X8= 128 cu. ft., but a u cord" of stone is commonly i X 4 X 8 = 32 cu. ft. Likewise the word perch, when used, should be clearly defined. A perch of masonry is commonly taken as being 25 cu. ft. (or nearly I cu. yd.), but the original perch was a wall 12 ins. high, 18 ins. wide and a rod (16% ft.) long, making 24^4 cu. ft. In certain localities the "perch" is taken as being only 22 cu. ft. These facts the contractor should know, for he must often deal with quarrymen who will not sell rock by the cubic yard. Rock is often purchased by the ton of 2,000 Ibs. ; but to avoid lawsuits it is wise to define the word "ton" in any writ- ten or verbal contract, for a ton means 2,240 Ibs. in some localities. If crushed stone for macadam or ballast is purchased by the cubic yard measured loose, the precaution of stating where the measurement is to be made should always be taken. I have made measurements of wagon loads of broken stone after loading from chutes at the bins, and again after travel- ing for half a mile or more. A surprising shaking down, or settlement, always takes place, ordinarily making a reduc- tion in volume of 10 per cent. 12 ROCK EXCAVATION METHODS AND COST. Rock excavation is commonly measured in place before loosening and paid for by the cubic yard of actual excava- tion ; but, in sewer work and in tunnel work, if the contractor excavates beyond certain "neat lines" shown in the blue- prints, no payment is made, unless the specifications ex- plicitly provide for payment for excavation beyond these "neat lines." In trench work, for example, a contractor often has to excavate from 6 to 18 ins. below the grade shown in the blue-print, because it costs less to do so than to work too close to the grade and afterward break off projecting knobs with a bull-point or otherwise. The same is true of shallow excavation, or skimming work, in road construction and the like. In examining specifications care should also be taken to note whether mention is made of rock slips or falls ; for it often happens that after blasting to the neat lines a huge slide of rock occurs, possibly filling the entire excavation. Who is to stand the cost of removing this slide? If it is specified that the contractor shall, then he should study the dip of the rock and its character with this question of sliding in mind. It is occasionally specified that rock for rip-rap shall be paid for by the cubic yard after deposition ; although it is a most unsatisfactory and uncertain way, for much of the rock may be lost in the mud or rolled away by the current. If the rock is delivered in scows it is a simple matter to estimate its weight by water displacement. CHAPTER II. METHODS AND COST OF HAND DRILLING. Kinds of Hand Drills. Drilling holes in rock by hand may be effected in three ways : ( I ) By a rotary drill or auger ; (2) by a churn-drill; (3) by a hammer-drill, or "jumper" drill, struck with a hammer. A rock auger operated by hand is used only in very soft rock or coal. A churn-drill, as its name implies, is raised and allowed to drop, or is hurled against the rock. For shallow holes of small diameter it is necessary to give a churn-drill additional weight, which is done by welding a ball of wrought iron to the center of the drill shank, making a ball-drill. A ball-drill is usually provided with a cutting bit at each end and is oper- ated by one man. For deep drilling, that is, for holes more than about 2^/2 or 3 ft. deep, an ordinary churn-drill is used, operated by one man for shallow work, two men for deeper work and three or even four men for very deep holes where the weight of metal becomes considerable. The Theory of Drilling. A hammer-drill, often called a "jumper," although it is not jumped, may be driven by one man, who holds the drill with one hand and strikes it with a hammer in the other hand. In this way holes up to 3 ft. in depth can ordinarily be drilled cheaper than when one man holds the drill while two men strike. But in discussing the relative economy of one-hand drilling as compared with two- hand drilling, authorities appear to have ignored the factor of depth of hole. As the hole grows deeper the advantage of a heavy hammer becomes more and more apparent ; but a heavy hammer requires a man's two arms to swing it. A large percentage of the energy of the blow is always con- 13 14 ROCK EXCAVATION METHODS AND COST. sumed in compressing the head of the drill, the shank of the drill and the hammer itself, leaving at best only a small per- centage to overcome the cohesion of the rock with the drill bit. In pile driving in soft mud about 65 per cent, of the energy of the hammer is lost in heating the pile-head, etc., leaving only 35 per cent, to overcome the friction of the mud on the pile ; and in an analogous way much of the energy of a hammer in the hands of a driller is lost. The longer the pile and the lighter the pile hammer, the greater the loss of energy and the less effective the blow ; so in drilling there comes with increased length of drill a decreased percentage of energy that reaches the bit. In fact, if the drill be made long enough, the blow of a one-hand hammer has absolutely no effect in cutting the rock, although a two-hand hammer still has effect. The churn-drill in the hands of a skilled driller is the most effective type of hand drill for vertical holes ; and a little theory is not without its practical value in seeking the reason for the effectiveness of the churn-drill. As before stated, much of the energy of the blow of a hammer is lost in the form of heat at the head of the drill. This loss does not oc- cur with the churn-drill. Moreover, the element of time in- volved in wedging off a chip of rock also appears to be an im- portant factor. When the cutting edge, or wedge, of a churn- drill first reaches the bottom of the hole, after its descent, the work of wedging off a rock chip begins. A wave of com- pression travels up several feet of steel before the last ounce of steel in the drill bar has done its work. Obviously it must take about 12 times longer for a churn-drill 6 ft. long to do its wedging work than for a hammer 6 ins. long to do its work. This comparatively gradual and steadily increasing wedging action of the churn-drill theoretically should be more effective than the more sudden action of a hammer- drill ; and, as a matter of fact, it is. It takes some skill to start a hole with a ball-drill and to keep it plumb ; but the time spent in acquiring this skill is re- METHODS AND COST OF HAND DRILLING. 15 paid many times over if quarry operations with hand-drills are to be moderately extensive. The effect of the size of the hole upon the speed of drilling appears never to have been carefully determined. One au- thority says that to double the diameter of the hole decreases the speed of drilling by one-half. Another authority thinks that doubling the diameter divides the speed by four. Ac- cording to the first authority, if a man could drill 12 ft. of i in. hole in a shift, he could drill only 6 ft. of 2-in. hole in a shift. According to the second authority, only 3 ft. of 2-in. hole could be drilled per shift. As bearing upon this point the reader is referred to some experiments with different sizes of bits used in machine-drilling tests, an abstract of which appears on page 54. In drilling by hand it is evident that the blow of a hammer is most effective when directed vertically downward, less ef- fective when directed horizontally and least effective when di- rected upward. The only careful experiments to determine the relative speeds of drilling at different angles appear to be those of Prof. Hofer. The time required to drill I inch of hole in graywacke (a slate, or grit, or conglomerate?) with a hammer-drill, with holes at different angles, was as follows : 85 down (nearly vertical) 152 sees. 60 " 188 " 52 " 241 " 27 " 282 " 2 " 257 " o (horizontal) 323 " 24 up 345 From which it appears that, at these rates, 16 ft. of vertical hole or 7^ ft. of horizontal hole would be drilled in 8 hrs. This shows one of the several reasons why rock excavation in a tunnel by hand is more expensive than open cut excava- tion ; and it indicates the importance of stating the angle of 16 ROCK EXCAVATION METHODS AND COST. the drill hole when giving data on hand drilling. Some data given by Jarolimek on drilling dolomitic limestone roughly confirm the above : 60 down 10,3 sees. 10 up 287 " 45 up 345 " As bearing upon this point of the angle at which holes are drilled some old data may be quoted from Schoen's "Der Tunnelblau" (1874). Schoen gives the comparative num- ber of cubic yards of material excaved in an open cut and in a railway tunnel, by hand work, 8-hr, shift, and using black powder : Cu. yds per man, 8 hrs. Tunnel. Open cut. Soft ground 8.5 16.2 Ground loosened with pick 5.3 7.2 * gad 3.2 6.5 Quarried rock i.i 2.6 Quarried and blasted rock 0.64 2.0 Blasted rock 0.34 1.3 In considering the effectiveness of vertical hole drilling it should be remembered that a hole which can be kept partly full of water can ordinarily be drilled faster than a dry hole, and holes that "look up" are necessarily dry, unless, as is rarely done, a jet of water is kept playing into the hole. The water in a down hole takes up and holds in suspension the fine particles of rock, leaving a clean face of rock at the bottom of the hole for the bit to work upon. One authority (Aitken) says that in quarrying trap rock the use of water in drilling reduces the time of drilling a hole by 30 per cent. In certain so'ft shales, however, up holes are drilled faster than down holes, for the dry powdered shale runs out of the up hole ; but in a down hole the shale powder makes a stiff mud with the water and cushions the blow of the bit. METHODS AND COST OF HAND DRILLING. 17 Hammer Drilling. The common weight of hammer for one-hand drilling is 4>4 Ibs. ; for two-hand or three-hand drilling, 10 Ibs. The striking face must be flat or slightly rounding, and smaller than the stock of the hammer. The hole is started on a solid and squared surface, with a short drill, for the longer the drill the less effective the blow. Light blows are struck at first. The bit is turned one-eighth of a revolution after each blow to insure keeping the hole truly circular. But in spite of this precaution most hand-drilled holes are three-cornered, or "rifled." This rifling is not very objectionable in ordinary excavation work, but in quar- rying square blocks for masonry it is decidedly objection- able because the rock tends to split in the directions of the three angles of the drill hole upon blasting. How to pre- vent this rifling will be shown in a subsequent paragraph. A leather or rubber washer is slipped over the drill and kept close to the hole to prevent splashing of the sludge into the eyes of the drillers. Water is poured into the hole, an operation which is called "tending chuck." The water holds the powdered rock in suspension, forming a sludge which must be removed from time to time. For cleaning out this sludge a scraper or "spoon" is used in shallow holes. A spoon is a ^ to ^-in. rod provided with a disc at each end, the discs being of different diameters to correspond with the size of the hole at different depths. A spiral hook, or drag-twist, is also used for wiping the hole with hay before charging with black powder. A wooden rod, split or broomed at the end is often used for cleaning out a hole. The broomed end of the rod is dipped into the sludge, and when removed from the hole is struck upon the rock to remove the sludge adhering to the broomed end. For two-hand or three-hand hammer drilling a bit of 1^4 to 1 5/2 ins. is commonly used for the starter, and the ex- treme depth of hole is ordinarily not over 6 or 8 ft. ; for, as previously shown, the effectiveness of the hammer blow falls off rapidly with increased depth. One man holding i8 ROCK EXCAVATION METHODS AND COST. the drill and two men striking (three-hand drilling) form the most effective gang for railway tunnel work, also for quarry work where men used to churn drilling are not available. One-Hand vs. Two-Hand Drilling. In the metal mines of the West skilled miners ordinarily prefer one-hand drilling when working by contract. The miner holds the drill with one hand and wields the hammer with the other. In very hard rock two-hand drilling is said by Drinker to be slightly (15 per cent.) cheaper than one-hand drilling; but in soft rock he says one-hand drilling is 20 to 30 per cent, cheaper than two-hand drilling. Where one man strikes, while the other man holds the drill, the heavier hammer used makes it possible to drill a larger and deeper hole with economy. Where there is room for one man to hold while two men strike, the economy is greater still. In American railway tunnel work two or three-hand drilling is much more com- monly seen than one-hand drilling. Reliable data showing the relative economy of one, two and three-hand drilling', using different diameters and lengths of bit, are not to be found in print, although much to be desired. Churn Drilling. For drilling vertical holes, churn drilling is cheaper than hammer drilling. The only exception to this statement is the drilling of plug and feather holes only a few inches deep ; but even then a skilful quarry man using a ball- drill will churn down a small hole with greater rapidity than a one-hand hammer driller. Almost any tyro, however, can drill plug holes with a hammer drill ; but it takes skill to start a hole with a ball-drill. For deep holes in soft rocks, like shale, a churn-drill, in the hands of two or more men, is the best hand tool in use. By building a light staging over the hole, as many as six men may operate one drill ; three men on the ground and three on the staging; but this is seldom done, except where deep soundings are being made to determine the nature of strata. For breaking up shale for steam shovel work holes 20 ft. METHODS AND COST OF HAND DRILLING. 19 deep are commonly drilled. A pit about 18 ins. deep and "3 ft. in diameter is often dug in the earth overlying the rock, and in the center of this pit the drill hole is started. When the hole is well started the men sit on the sides of the pit with their feet in the bottom. I have never been able to see the philosophy of this pit digging, for a circular wooden stool serves as well as the ground to sit on ; and, unlike the pit, it can be used over and over again. Moreover, it is an open question whether churn drillers should be permitted to sit down, for in that position their arms and shoulders do the entire work, whereas when standing their back and thigh muscles aid in lifting the drill. When more than two men are operating a drill it is practically impossible to use the back and thigh muscles; hence the efficiency of each man is greatly reduced when a third man takes hold of the drill, unless the third man stands on a scaffolding above the heads of the two men on the ground. A round drill rod 24 m - m diameter weighs 1.5 Ibs. per ft. of length; a I in. rod, 2.65 Ibs. ; a 1^4-in. rod, 4.1 Ibs. per ft., and a i l / 2 -m. rod 5.95 Ibs. per ft. It is well to bear these weights in mind when con- sidering the work of churn drilling, for it seems such a little thing to add only % in. to the diameter of drill stock, while in fact the addition adds greatly to the work of lifting the drill. Up to a certain limit, weight is desirable in drilling with a churn-drill; for the drill is not hurled, but allowed to drop freely (unless it is a ball-drill), and does its work by virtue of its weight and velocity. But for every class of rock there is a limit to the weight of a churn-drill beyond which there is an actual loss of efficiency, due to the greater number of drillers required to lift the drill. Cost of Hammer Drilling. We have seen that the diameter of the hole, the angle at which the hole is driven and the presence or absence of water in the hole all affect the cost of drilling by hand. We have also seen that the method of drill- ing with hammer-drills or with churn-drills is an important factor in the cost. Obviously the character of the rock is 20 ROCK EXCAVATION METHODS AND COST. the most important factor; but unfortunately very few re- liable records of cost of drilling in different kinds of rock are to be found. From some observations on hammer drilling, with a i l /2 in. starting bit I have found that where one man is holding the drill vertically and two men are striking, the "ate of drilling a 6- ft. hole is as follows : Ft. in Cost per ft., 10 hrs. cts. Granite 7 75 Trap (basalt) 1 1 48 Limestone 16 33 The cost is based upon a wage rate of $1.75 per Q-hr. day per man ; and does not include the cost of sharpening drills, which may be taken at 5 to 8 cts, per ft. more. I have found that a man drilling plug and feather holes in granite, each hole being 5/& in. diam. by 2y 2 in. deep, will average one hole in 5 mins., including the time of cleaning out holes, and the driller strikes about 200 blows in drilling the hole. No water is used in drilling these shallow holes, for the dust is readily and quickly cleaned out with a little wooden spoon. In 8 hrs. of steady work about 100 holes can be drilled, which is about 21 ft. of 5/ in. hole. But in plug and feather work part of the time is spent in selecting rock, driving the plugs, etc., so that 50 or 60 holes drilled and plugged and feathered is generally counted a fair day's work. I am indebted to Mr. John B. Hobson for the following data of hammer drilling in a British Columbia mine : Rock was augite diorite and firm red porphyry ; starting bit, I ^ ins. ; finishing bit, i 1 /^ ins. ; % in. steel ; holes, 6 ft. deep ; 8-lb. hammer. Two miners (one holding drill and one striking) averaged 14.8 ft. per lo-hr. shift. With wages at $2 a day the cost was nearly 28 cts. per ft. of hole. Mr. Frank Nicholson states that in mining chalcopyrite in magnesian limestone at St. Genevieve, Mo., a day's work for a striker and a holder was 12 ft. of hole drilled. The METHODS AND COST OF HAND DRILLING. 21 drills had i^-'m. starting bits, % in. octagon steel being used. Wages in 1882 were only $1.35 for miners doing this work, the shift being 10 hrs. long. It cost $6.50 per lin. ft. to drive a 4 X 6 ft. drift, using 40 per cent, dynamite. In driving the Hoosac Railway Tunnel in 1865 (see Drinker) through gneiss and tough mica schist, 2-ft. holes were drilled in the headings, using i^-in. starting bits, anu each driller averaged only 3^ ft. of hole per lo-hr. shift. From 7 to 13 bits were dulled in drilling each hole. Drilleia were paid $2.25 a day. Black powder was used in blasting, which accounts for the fact that the holes were large in di- ameter and shallow. In driving the Glasgow water works tunnels in 1856-1857 (see Simms), through very hard mica schist, drill holes 20 ins. deep and i% ins. diam. were drilled, a new bit being re- quired for each inch of hole. The time required to drill each hole is stated to have been ij^. hrs., but no statement is made as to the number of men engaged presumably two or three on each hole. Ihlseng states that Swedish iron miners each average 5 ft. of hole a day in medium rock ; single-handed drilling ; holes 2,y 2 ft. deep; but he does not give the size of bits a serious omission. On the Nesquehoning Railway Tunnel (Drinker) driven in 1870 through the conglomerates and shales of Carbon county, Pa., drillers received $2.25 and laborers $2 per 8-hr, shift. The cost of hand drilling was 56 cts. per ft. of hole, of which 6 cts. was for steel and sharpening. Machine drill- ing in this same material cost 14 cts. per ft. of hole, including repairs to drills, etc., but not including interest and depre- ciation. In excavating hard porphyry for the rock-fill dam at Otay, Cal., Mr. W. S. Russell states that a good day's work for three men drilling (one holding and two striking) was 6 to 8 ft. of hole, costing about 80 cts. per ft. of hole drilled. The holes were drilled 20 ft. deep vertically and sprung. This 22 ROCK EXCAVATION METHODS AND COST. was an unusual depth of hole for hammer drilling, and ac- counts for the high cost per foot. It shows also how un- economic is hammer drilling in deep vertical holes com- pared with churn drilling. In driving a small (3 X 4^-ft.) tunnel through tough sandstone one driller averaged 4 to 5 holes, each I y 2 ft. deep, per 8-hr, shift, using % in. bit for the starter; and, upon cleaning up, the advance was I ft. per shift for one man. Each hole was charged with half a stick of 75 per cent, dyna- mite. Cost of Churn Drilling. I am indebted to Mr. W. M. Douglass, of the firm of Douglass Bros., contractors, for the following data on drilling with churn-drills, for railroad work in western Ohio. Three drillers were used for putting down the first 18 ft. of hole in blue sandstone the first day (10 hrs.), and four men were used for putting down the last 12 ft. of hole, so that it required 70 hrs. of labor at 15 cts. per hr., or $10.50, for a 3O-ft. hole, making the cost 35 cts. per ft. In brown sandstone it required 70 to 80 hrs. labor to put down 30 ft. The drill holes were 2^4 ins. at top and 1^2 ins. at bottom. Drilling with steam drills in this same stone, holes 20 ft. deep, cost 12 cts. per ft., including everything except interest, depreciation and drill sharpening. The cost of hand drilling agrees very closely with my own records of similar work in Pennsylvania. Trautwine gives the following rates of drilling 3-ft. ver- tical holes, starting with a i^4-in. bit, one man drilling with a churn-drill, shift 10 hrs. long: Solid quartz 4 ft. in 10 hrs. Tough hornblend 6 " " " Granite or gneiss 7.5 " " " Limestone 8.5 " " " " Sandstone 9.5 " " " " It should be observed that the holes in this case are shallow (3 ft.), and the diameter (i% ins.) is large for such shallow METHODS AND COST OF HAND DRILLING. 23 holes, indicating that Trautwine's data applied to rock exca- vation where black powder was used. Hand-Drill Bits. A bit has least work to perform at its center (contrary to Drinker's statements), and this is well shown by the fact that a bit wears most rapidly on its pro- jecting ears. The rock near the center of the hole is struck oftener than anywhere else; hence it is quickly cut away; whereas the rock near the circumference of the hole is not struck so often and is more slowly cut or crushed to pieces. The ears of the bit may project considerably beyond the stock of the drill rod when the rock is soft, because they wear less rapidly and resist breaking off better than in tough, hard rock. The width of the bit may be 30 per cent, to 100 per cent, greater than the diameter of the drill rod, depend- ing upon the hardness of the rock. For one-hand hammer drilling an octagon steel rod Y^ to fa in. in diameter is commonly used ; but ^ in. to I in. steel may be said to be the limits of size used for one-hand drill- ing. In comparatively soft rock a jHi m - octagon bar may have a I in. bit, a % in. bar, a i%-in. bit; and a i^-in. bar, a 3-in. bit, the larger sizes of bits being used only in two- hand hammer drilling or churn drilling. In two-hand ham- mer drilling a 1^4 to i*/2-in. hole for a starter in medium hard rock that is to be drilled to depths of 6 or 8 ft. is com- mon ; for it must be remembered that as the hole grows deeper it grows smaller in diameter, due to the continuous wear on the ears of the bits, so that unless a reamer were used it would be impossible to have a uniform diameter of hole except in very soft rock. The least admissible diameter of hole at the bottom is about 24 in., where dynamite is used. In the days of black powder a much larger hole was necessary in order to hold enough explosive, although it cost more money to drill the hole; thus in the Hoosac Tunnel the holes were only 2 ft. deep and i^ ins. in diameter at the mouth of the hole. It is a hard rock that will wear the ears of the bit so fast as to 24 ROCK EXCAVATION METHODS AND COST. reduce the diameter of the hole ^ in. in drilling 2 ft., so that a hole 6 ft. deep need not have a diameter at the mouth more than 24 m - greater than at the bottom even in very hard rock. The chisel edge of a bit is ordinarily made not straight across, but slightly curved. Different authorities have as- signed different reasons for giving this curvature to a bit. Drinker says that in hard rock the curve must be quite flat, but in soft rock it must be very rounding; and his reason is that the wear of the bit being greatest at the center per- mits of a more rounding form for soft rock. As a matter of fact the wear is never greatest at the center of a bit, and in any case his inference is illogical. Aitken says that the bit is made rounding so as to give greater strength to the ears, and following this reason to its logical conclusion would give us a very rounding bit for very hard rock precisely the op- posite of the form recommended by Drinker. To me it seems apparent that a rounded cutting edge is especially desirable in starting a hand-drilled hole, for it insures effectiveness of the 'first few blows by concentrating the work upon a small area. Moreover, for the first few inches of the hole, a rounded cutting edge is desirable because any slight tilting of the drill will not mean the concentration of the energy of the blow upon one of the ears, which is the weakest part of the drill and most easily broken. In machine drilling this is not important, but in hand drilling it certainly cannot be overlooked. As corroborating this theory it should be noted that the short drills used for drilling plug and feather holes in granite are invariably made very rounding or convex; whereas in drilling deep holes in sandstone consisting of coarse grains poorly cemented together, a perfectly straight- edged drill is common. A rounded or convex bit cuts a cup-like bottom in the drill hole, which aids in keeping the drill centered ; and it is not improbable that the cup acts like a mortar in which the chips from the edges of the hole col- lect at the center and are more quickly pulverized. The col- lecting of chips at the center of this stone mortar gives the METHODS AND COST OF HAND DRILLING. 25 bit more work to do at its center, which is precisely what should be done in view of the fact that the outer edges would otherwise have most of the work to do. The wedge-shaped edge of a bit is made as sharp as will hold up without rapid dulling or chipping. In hard rock the bit is made thick near the edge, and with angle of nearly 90. In soft rock the bit is thin and sharp, with an angle of about 45 between the faces. To this rule there is an excep- tion, for where the rock is a sandstone of rather coarse grains poorly cemented together, a bit that has a blunt edge works fastest. This is due to the fact that the grains of poorly cemented stone are easily broken apart and then the blunt edge crushes them quickly like a pestle in a mortar.' A blunt bit is used in drilling small holes in earth, but for a different reason ; the blunt bit in earth compacts the earth and crowds it aside, 'necessitating less cleaning out of the hole. 'Fig. i. Machine Drill Bits. We have thus far considered only the plain chisel bit, which is the type commonly used in hand drilling. In machine drilling a cross (or square) bit ( + ), or an ex (X) bit, is commonly used. Occasionally a Z bit is seen. These bits possess the advantage of drilling a more truly circular hole than a chisel bit ever does. Fig. i, from an article by T. H. Proske, in the Engineering and Mining Journal May 5, 1904, shows shapes of machine drill bits used in the United States. Bit "A" is the common cros5 (_(_) bit, and bit "D" is the X-bit. The theoretical 26 ROCK EXCAVATION METHODS AND COST. advantage of the X-bit lies in the fact that its cutting edges, aa and bb, are not perpendicular to one another, as they are in the +-bit, so that they do not strike twice in the same place in making one complete revolution ; for the bit is turned y& revolution during each up stroke. Bits "E" to "H" are hand-sharpened -| bits, which usually have curved cutting edges, instead of the straight edges of machine-sharpened bits. Bit "B" is the Fitch bit, which has proved very efficient in the extremely hard jaspar of the Champion Mine, Mich- gan ; tests with a 2^-in. Rand drill, under 60 Ibs. air pres- sure, having shown an average drilling speed of 0.28 in. per min. for the -| bit, as compared with 0.66 in. per min. with the Fitch bit. Bit "C" is the Brunton bit, invented by D. W. Brunton, used by the Anaconda Copper Co., Butte, Mont., and at a number of other mines in Montana and Idaho. With this bit the drill piston must turn half way around before the cutting edges strike twice in the same place. A bit should "mud" freely, and to do this the faces form- ing the chisel edge should meet at an angle of about 80 for soft rock and 90 for hard rock. A flat chisel edge, like bit "G," or a sharp edge, like bit "H," will not mud freely. Bit "E" is the common hand-sharpened cross-bit; bit "F" is the same after one-half the originally forged cross has worn off; bit "G" shows the cross nearly worn off; bit U H" is the work of a careless blacksmith, the corners being drawn out and the center not set back. Sharpening Hand Drills. A good blacksmith is as es- sential to economic rock excavation as good hand drillers. For this reason every contractor and every mine manager having charge of drilling operations should know at sight a good blacksmith when he sees him do his work. To be able to do this it is not necessary to become a blacksmith, but simply to learn the art of drill sharpening by reading and by watching and by inquiry. One of the best foremen of rock excavation that I know is a cripple who has never done a stroke of drilling or tool sharpening himself ; but he knows METHODS AND COST OF HAND DRILLING. 27 exactly how it should be done and cannot be imposed upon by a pretender. The educated man is apt to be fearful of showing himself ignorant of practical work by inquiring into the methods of the drill sharpener. To begin with the blacksmith must have good drill steel (not tool steel) to work with. Drill steel contains 0.8 to i per cent, of carbon. If the steel loses any of this carbon by oxidation it becomes softer and dulls quickly. In heating the bit it is therefore essential : ( I ) That the heating be not too long continued, nor carried above a cherry red; (2) that the air blast be not too strong; (3) that the bit and some of the shank be well bedded in the coal or charcoal and not in a thin bed of hot cinders. If these rules are not carefully followed the steel will be "burned," which means simply that some of the steel will be oxidized and that this oxide will in turn oxidize some of the carbon of the steel. The heating should be uniform, and to secure uniformity the blacksmith turns the drill over in the fire. When the bit has become a dull cherry red it should be removed with as little delay as possible and dressed. If the corners of the bit are badly worn the chisel edge must first be upset (blunted) to give the proper width; then the drill is held on the anvil at a slope of about I ft. rise to 2 ft. horizontal, the edge of the bit being even with the edge of the anvil. In this posi- tion it is hammered, turning over at intervals, until a new cutting edge is made. A file may be used (while the bit is still hot) for the final shaping. If the drill is simply dull it is not necessary to upset it, but when taken from the fire it is tapped or brushed to remove any cinders, laid on the anvil and struck with light glancing blows until an edge has been formed. The blows should be glancing so as to draw the steel fibres toward the cutting edge, and the lighter the blows that will accomplish this result the tougher the steel becomes. The width of each bit should be carefully gaged, for noth- ing is more exasperating to the drillers than to have a care- less blacksmith send out bits irregular in width from ear to 28 ROCK EXCAVATION METHODS AND COST. ear. As above stated, each longer set of drills must have a slightly smaller bit, for all drill holes grow narrower as they grow deeper. The exact reduction in size depends upon the hardness of the rock, and is ascertained by experiment. The bit after being shaped must be reheated for tempering. The heating is done in the forge, as before, until the bit is cherry red, when it is immediately plunged into water for a moment to partly cool it, and then rubbed on a stone to remove the scale, so that the play of colors may be readily seen in a dark corner of the shop. The colors indicate ap- proximately the following temperatures : Very Pale yellow 43F Straw : 470 Brown 490 Purple 530 Full blue 560 Dark blue 600 As the drill cools the colors should advance parallel to the cutting edge if the cooling is uniform ; if otherwise, that side of the bit on which the colors are advancing most rapidly should be held in water. This plunging into the water is sometimes repeated several times before the colors move parallel with the edge of the bit. Finally, when the colors move parallel with the edge, watch the edge closely until it is straw color and plunge into water a short distance, waving it back and forth (to insure rapid cooling) until the steam ceases to form; then leave it in the quenching bath. The quenching bath should be a tub large enough to cool the drills without raising the temperature of the water sensibly. Some of the baths commonly used are brine, water, rape- seed oil, tallow and coal tar ; the brine cooling the drill fast- est and the coal tar slowest. Sharpening Machine Drills. The ordinary -f or X bit used in machine drills usually receives treatment somewhat METHODS AND COST OF HAND DRILLING. 29 different from that just described, partly due to its shape and partly due to the greater mass of metal in the bit. The Fig. 2. Fig. 3- bit is first shaped by a special set of blacksmiths' tools, shown in Fig. 2 (from Ingersoll catalogue) consisting of a "dolly," A, "sow," B; "spreader," C; "flatter," D; and "swage," E. The best blacksmith that I have had makes a "dolly" for each size of bit. To do this he heats a block of steel, and drives against it a cold drill bit of the exact shape and gage desired, thus producing what he terms a "female bit," which is afterward tempered hard. The "female bits," or dies, of different sizes are fastened to the anvil so that a hot bit which is to be shaped can be held horizontally and hammered into the die. The result is that all bits are rapid- ly made true to gage and well shaped. After shaping the bit is reheated for tempering, and at the proper temperature is placed in the cooling bath. Fig. 3 shows a cooling bath (after T. H. Proske), in which a grate or screen is placed Y^ in. below the water surface to support the bit until it is cool. A rack built around the tank, with nails 3 ins. apart, holds the drills upright. The hot steel above the water line prevents the chill from reaching up to the water line, so that only the face of the bit is hardened. The mass of metal in the bit and the fact that at each resharpening the water line is higher up on the drill (due to wear of bit) eliminate danger of cracking at the water line. When this method of 30 ROCK EXCAVATION METHODS AND COST. cooling is used the edges of the bit should be perfectly straight and not rounding. A bit immersed for a short time, and then withdrawn for annealing, is apt to be soft centered, due to the fact that the center cools more slowly than the corners. Within the last few years machines for sharpening drills have come into use in some of the large mines. I have rec- ords of the work done by two types of machine-drill sharp- eners: The "Ajax" and the "Word," which consist essen- tially of two air-driven hammers, one hammer working hori- zontally, the other working vertically. Mr. Robert A. Kin- zie informs me that the Alaska Treadwell mines use Ajax drill sharpeners, and that one machine sharpens 460 bits per shift. The first Word drill sharpeners were used at the Franklin copper mine, near Houghton, Mich., and at the Black Oak mine, Loulsbyville, Cal. Mr. W. G. Scott, super- intendent of the Black Oak mine, is quoted in the Mining and Scientific Press, April n, 1904, as follows: "The machine ran 183 days with nominal repairs. Aver- age hours run daily, 4 ; total, 732 hours. One man operated the drill, attended his own forge and made necessary re- pairs. Any man who can set up and run a machine drill can run the drill sharpener. Approximate number of drills upset and sharpened, 36,000; average, 50 drills per hour. Fuel used is less than one-half that required in hand work. One and one-half minutes are required to form and sharpen a new drill. Over 60 drills have been repointed by this ma- chine in one hour. The life of a bit sharpened by this drill is longer than when done by hand, the bits being better formed and more compact, taking a better and more even temper. The different-sized points are made with uniform- ity. By a change in the dies the machine will sharpen hand drills. Before we used this machine we employed two drill- sharpening blacksmiths and two helpers to make and sharp- en drills. The saving of the machine over hand labor in six months has been $1,738.50; saving on coal (183 days), $183; or a total saving for six months of $1,921.50." CHAPTER III. MACHINE DRILLS AND THEIR USE. Machine Drill Mechanism. To discuss the mechanical de- tails of rock-drill construction is not within the scope of this chapter, for to do so adequately would require a book in it- self. Moreover, a careful study of the line-cuts and descrip- tive matter of catalogues, supplemented by some machine- shop experience where drills are repaired, is indispensable to any one who wishes thoroughly to acquaint himself with rock-drill mechanism. I shall therefore confine myself to an enumeration of the parts and their functions, referring to Fig. 4, page 33, which is a section of one of the standard makes. 1. The cylinder. 2. Front head of the cylinder and stuffing box through which the piston works. 3. Back head of the cylinder. 4. One of the two side-rods or "through-bolts" that hold the cyl- inder heads in place. 5. Steam chest. 6. Spool valve. 7. Tappet valve which is oscillated by the shoulders on the piston. 8. The piston. Note the grooves near its ends for the cylinder rings which make an air-tight fit. 9. The chuck at the end of the piston rod for holding the shank of the drill steel. 10. The rifle bar for rotating the piston on each back stroke. 11. Key that aids in holding the shank of the drill steel. 12. The U-shaped chuck bolt with a nut at each end of the U. 13. Two pawls forced by two pawl springs to catch the teeth of the ratchet wheel. 14. The ratchet wheel which prevents the rifle bar (10) turning on the forward stroke of the piston, but allows it to turn on the back stroke. 15. The guide shell on which the cylinder is mounted. 16. The cup by which the guide shell is fastened to the tripad or column arm. 31 32 ROCK EXCAVATIONMETHODS AND COST. 17. Feed nut fastened to the cylinder. 18. Feed screw for moving the cylinder along the guide shell. 19. Crank of feed screw. Air drills of the rotary type are still in use in Europe ; but in America, which is the birthplace of the air drill, no type is in use for rock drilling but the percussive type. The drill is churned back and forth in the hole by compressed air or steam power, and after each stroke it is mechanically turned a fraction of a circle. The drill is fed forward by hand, a crank at the end of a feed-screw being used for this pur- pose. A longer drill is inserted every 2 ft. in depth of hole, for 2 ft. is the limit of feed of the ordinary feed screw used. Automatic feed devices are not commonly used on drills of ordinary sizes, but only on very large drills for submarine work. Sizes of Air Drills. The size of an air drill is denoted by the inner diameter of its air or steam cylinder; thus a 3^- in. air drill is one having a cylinder 3^ m s. diam. The smallest size, 2*4-in. drill, is called a "baby drill," or a one-man drill the latter name being given to the drill because it can be readily moved about and set up by one man. For narrow work in mines the baby drill is adapted. It is also used largely for drilling plug and feather holes, and might often be used profitably for shallow cuts and trenches. The sizes most commonly used for general con- tract work, tunneling and mining are the 3^-in. and the 3^4-in. drills. A recent report states that in 101 gold mines of the Transvaal, South Africa, 2,355 ^ r drills are in use, and of this number 1,680, or 70 per cent, are 3^4-in. drills. Where the holes are deep and the drilling hard, it is often found that the 3^g-in. drill is the size to be chosen. Thus, in shaft sinking in syenite at the Treadwell Mine, Alaska, it has been found that the number of feet drilled with the 3^-in. drill is fully 30 per cent, greater than with the 3%- in. drill. As we proceed it will become more and more ap- parent that the most economic size of drill for any particular MACHINE DRILLS AND THEIR USE. 33 34 ROCK EXCAVATION METHODS AND COST. class of work can only be determined by experiment, and that as yet no hard and fast rules can be laid down. The fol- lowing table gives approximately the principal data regard- ing air drills : Diameter of cylin- der ins. 2/4 2 L 2 34 3 l /S 3^4 3*6 Length of stroke, ins. 5 6 6*/2 iff 7% Length of drill from end of crank to end of piston, ins. 36 43 50 50 50 52 Depth of hole drill- ed without change of bit ins. 15 20 24 24 24 24 Diameter of supply inlet (standard pipe) ins. y. y. 34 i i 1 14 Approximate strokes per minute with 60 Ibs. pressure at drill 500 450 375 350 325 300 Depth of vertical hole each machine will drill easily, ft. Diameter of holes 6 8 10 14 16 20 drilled as desired from ins. 34 tO l l /2 i to iYi l*/ 2 to 2 J4 iy 2 io2y 4 1 34 to 234 i34 to 3 Diameter of octagon steel used . . ins. 34 to ^ H to i i to ij4 i l /& to ij4 1 1 A to 1 54 i %-ifa Best size of boiler to give plenty of steam at high pressure 6H. P. 8H. P. 8H. P. 9-H. P. 10 H. P. 12 H. P. Best size of supply pipe to carry steam 100 to 200 feet ins. * 34 y* i i 154 Drill unmounted with wrenches and fittings, not boxed Ibs. 128 190 265 3i5 285 390 Tripod without weights, not box- ed Ibs. 80 1 60 1 60 160 210 275 Holding down weights, not box- ed Ibs. 120 270 270 285 330 375 Drill, tripod, weights and wrenches, boxed Ibs. 415 660 820 885 952 1230 Drill unmounted with wrenches and fittings without tri- pod or column. . . Tripod and weights $I7O.OO $30.00 $200.00 $50.00 $225.00 $50.00 $250.00 $50.00 $275.00 $50.00 $295.00 $55-00 Handling a Drill on a Tripod. A drill mounted upon a tripod is the combination commonly used for surface drill- ing, and even underground on the benches of railway tun- nels and often in stoping ores. I shall discuss the handling of the tripod drill somewhat in detail, for every manager of drilling forces should know such of the details as will be MACHINE DRILLS AND THEIR USE. 35 set forth, beside many others which the recital of these de- tails may stimulate him to learn for himself by observation. The order of tripod drilling operations is as follows : 1. Have laborers clean away all earth and loose rock over the sites of proposed drill holes; for earth would clog the drill and would not give a stable support for the tripod. If the surface of the rock to be drilled is loose and shelly, have the laborers clean it away down to solid rock, for a hole can- not be started on loose, shelly rock. I have often seen the expensive drill crew delayed 15 or 20 minutes while one of the crew was occupied cleaning away shelly rock. A laborer at 15 cts. an hour will do this work as well as a drill crew at 50 cts. an hour. 2. Set the tripod over the site of the proposed hole, giving the legs a good spread to secure stability. At best there is considerable vibration when the drill is at work. A small "cat hole" is dug in the rock with a pick or a hand drill for the point of each tripod leg to set in. 3. Having "spotted" the leg points, the legs are adjusted until the saddle is about horizontal. The set screws are then tightened and the tripod leg weights put on. 4. If the machine is not already in its saddle, place it there and fasten the saddle to the cup. 5. Unloosen the nut that clamps the tripod saddle and point the drill in the line of the proposed hole. 6. The "starter," or first drill, is inserted in the chuck af- ter wiping the shank of the drill clean ; and the nuts of the chuck bolts are set by first screwing one and then the other until they are perfectly tight. Be sure that the shank of the drill is in as far as it will go before tightening the U-bolt. The starter should have a sharp bit welded to a full sized and perfectly straight drill rod. Beware of a slender drill rod with a nub bit wherever difficulty is expected in starting the hole. 7. The piston is drawn back until it strikes the cylinder head. 36 ROCK EXCAVATION METHODS AND COST, The bit is fed forward until the bit strikes the rock, and the point where it strikes is spotted. 9. The piston is shoved into the cylinder, and the bit is raised by the feed-screw. 10. The rock where the bit will strike is faced square for an area of y 2 in. or more larger than the bit ; for if the drill strikes a glancing blow it may bend the shank, and due to the vibration of the machine, it will vary y 2 in. in its align- ment. 11. The piston is moved in until it is about the center of the cylinder, and a little oil is let into the cylinder if the machine has not been used in some time, and is operated by air. 12. Turn the air or steam through the hose before coup- ling it to the drill, in order to blow out any dust or chips ; turn off the air and wipe the threads of the coupling clean. 13. Turn off the throttle valve of the machine, then couple on the hose. 14. Let the drill runner test all the nuts with his wrench ; and in tightening nuts bear down on the wrench instead of pulling up, as pulling up may shift the machine. 15. Run the bit down to within I in. of the rock, for in that position the drill automatically gives a short stroke, and a short stroke is always desirable in starting a hole. 16. Open and then close the throttle if steam is the power used, and work the piston back and forth by hand two or three times, so as to heat everything up evenly and prevent breaking of a part. Then tighten up the side rods which have been left loose to avoid breaking them by the heat ex- pansion. Tighten them evenly and no more than is neces- sary to secure a tight steam joint. 17. Open the throttle valve part way so that the drill will strike a light blow until a depth of hole has been reached that is greater than the full stroke of the drill, that is, until the bit no longer lifts above the surface of the rock. A little slowness in starting is time saved, because the danger of MACHINE DRILLS AND THEIR USE. 37 breaking the drill is avoided and a true round hole is secured. 1 8. The helper "tends chuck" by pouring in water, using a can filled from a bucket nearby. 19. When the drill has worked up to its full stroke (6 ins.) the feed-crank is turned slowly so as to keep the bit in position to strike a full blow. If the feed is too slow the piston strikes the cylinder head with a metallic sound that is unmistakable; in which case give the feed-crank a few rapid turns to prevent damage. If the feed is too fast the stroke is automatically shortened, and the rate of pene- tration of the drill is materially decreased. 20. When steam is used instead of air, more or less steam will condense in the feed pipe during the time that a drill is being moved from hole to hole. Therefore do not let oil into the cylinder until the drill has been running some time (long enough for the water to have all been blown out). The piston must be kept perfectly lubricated to avoid rapid wear. 21. When the feed-screw has reached its limit (the feed is 2 ft. in ordinary sizes), the air is turned off; the drill is raised as far as the feed screw will run, and taken out of the chuck. The hole is cleaned with a "gun" or sand pump. If the hole is shallow a stick broomed at the end may be used to remove the sludge at the bottom of the hole. These twenty-one rules of ordinary procedure may now be supplemented by a few rules for emergencies and the care of drills. i. The repeated sticking of a bit in a hole is most exas- perating to the drill runner, and the usual remedy is to strike the drill shank viciously with a sledge until the bit comes loose. It is needless to add that this remedy often kills the patient, like other heroic treatments. A moderate blow on the drill shank, near the hole, is a reasonable and often suc- cessful means of loosening a stuck bit. A blow should never be hard, and never so high up as to strike the chuck, for a bent piston or a broken chuck is likely to 'result when hard or high blows are struck. 38 ROCK EXCAVATION METHODS AND COST. 2. When a bit sticks, nine times out of ten the cause is a crooked hole ; and the remedy is a movement of the machine bodily to counteract the tendency of the hole to become crooked. If the drill sticks repeatedly, loosen up the clamp that the shell sets in and determine whether the drill is on line with the hole. If it is not, slacken off on one of the tripod legs so as to throw the drill rod against the side of the hole in the direction the hole is crooking. A lazy driller will hammer his drill ; a good driller will reline it. 3. If the bit strikes an inclined layer of rock, and particu- larly if that layer is harder than the rock above, the bit will glance off toward the "down hill" side and probably stick. The best remedy that I have found in this case is to drop a number of fragments of gas pipe, or other chips of iron, into the hole. These fragments of iron are forced into the soft rock on the lower side, and practically produce a level sur- face for the bit to strike upon. Old ^4 in., or larger, gas pipe should be cut up into bits with a cold-chisel for this purpose. If the inclined layer of hard rock is not very hard, small quartz pebbles, or the like, will serve instead of iron. 4. In any case, when a drill sticks, shorten the stroke of the drill by feeding down the feed screw, so that the air or steam may get between the piston and the front head ; and work for a time with short strokes. 5. Often the cause of sticking is in the bit itself, which may have a broken ear, or the drill rod or shank may not be exactly central with the center of the bit, due to poor blacksmith work. 6. If the rock produces a clay sludge that adheres to the bit and causes sticking,' a pipe may be put down in the hole after removing the drill, and a steam or air jet blown through it. This will effectually clean out the sludge when other means fail. Ordinarily, however, all that is necessary is to crank the drill back, pour in a cup of water, turn on about a quar- ter of the head of air and churn the stiff mud as the machine is cranked up. MACHINE DRILLS AND THEIR USE. 39 7. The softer the rock the more rapidly does the sludge accumulate. To remove the sludge as fast as it forms, a jet of water is most effective. A small pipe is kept in the hole alongside the drill rod, and water is continuously forced through the pipe, either by gravity or by steam or air pres- sure. In some rocks the increased number of feet drilled per day after a water jet is installed is astounding amount- ing often to a 40 per cent, increase. 8. When moving the drill from place to place the piston should be kept inside the cylinder, for otherwise it may be bent if the drill is allowed to fall. 9. A good mineral cylinder oil should be used in the air chest, and from there it passes into the cylinder. Feed in a small amount at frequent intervals, and on a new drill use an excess of oil for the first few days, because the moving parts of a new machine fit tight and hold very little oil at one time. 10. In cold weather, when steam is used, the stuffing box should be unscrewed to let the water out of the cylinder by inclining the drill on its side so as to drain the steam chest and back head. n. When the machine is not in use it is important to keep the valve and piston well oiled, otherwise rust will rapidly eat away the machined surfaces. 12. Keep on hand a supply of U-bolts and nuts, and have the blacksmith learn to make them, as their life is short at best. A bolt that permits a nut to work loose should be dis- carded at once, for it is the poorest kind of economy to con- tinue using it. A supply of pawls and pawl springs should also be kept in stock, for while a drill will work with one pawl (after removing the broken one), it will not work economically. Much of the poor work done by drills may be attributed to working with one" pawl. 13. In hard rock it often happens that a bit dulls so rapidly that its ears wear off more than is usual ; in which case the hole becomes smaller than usual, and, as a conse- 40 ROCK EXCAVATION METHODS AND COST. quence, the next new bit will stick on the sides of the hole before reaching the bottom. In this case insert the shank into the chuck, crank up close, turn on the air without tight- ening the nuts of the U-bolt of the chuck. This will drive the bit straight to the bottom of the hole. Pull it up, turn the bit, and in like manner drive the bit down in a new posi- tion ; repeat this operation once more and the hole will prob ably be reamed sufficiently to proceed with the regular drilling. 14. When a drill is choked in the hole and cannot be loos- ened by hammering, it is often possible to loosen it by run- ning with a loose chuck as just described, and turning the drill with the hands during the back stroke of the piston. Use of the Column or Bar. In the early days of tunneling machine drills were mounted on cars running on tracks, and this is still the practice in Europe ; but in America the drill is usually mounted on column (Fig. 5) or bar made of 3 to 5^2-in. pipe provided with one or two screw jacks at one end. In tunneling the column is usually set upright with blocks of wood between its ends and the rock, although in narrow headings it is often found preferable to set the bar horizontally just as is done of necessity in shaft sinking. The machine is mounted on an arm projecting from the column. The advantage of the column method over the car method of mounting drills is that without waiting for the blasted rock to be entirely cleaned away, the drillers can set up and get to work. A column is preferable to a tripod where it can be used, for it gives a firmer support and there is in conse- quence less liability of the hole running crooked. Moreovei in a stope where the men stand on loose rock it is very diffi- cult to get a solid footing for each of the three tripod Ieg3 without laying a substantial flooring of some kind to work upon. In mining work it is advisable to have an assortment of bars ; for one driller may require a bar 3^ ft. long for a MACHfNE DRILLS AND THEIR USE. 41 Fig. 5- 42 ROCK EXCAVATION METHODS AND COST. horizontal set up, whereas another may find a 9 ft. bar none too long for an upright set up. 1. Blocks of tough wood, reasonably free from knots, are, placed between the ends of the bar and the rock. Sawed wedges about I ft. long and of varying thickness at the butt are preferable; but blocks that are flat on the side next to the rock and rounded on the side next to the bar may be used. Most of the blocking should be placed at the jacking end of the bar if possible ; a 2-in. piece properly wedged up will serve for the other end, which, in a vertical set up, is the upper end of the bar. 2. The shoe or shoes should fit squarely on the blocking; and to this end the bar may be deflected if necessary. 3. Having placed the blocking, the jack screws are jacked up until the column is solid, after which the safety clamp is put on and its screws set up. If the set up is on the rubble filling of a stope jack up a little at a time, as the rubble settles under the vibration of drilling, and thus avoid split- ting the blocking by trying to jack up all at once. 4. The column arm is next put on the column, but its nuts are left a trifle loose, so that the arm may be swung about. 5. The saddle clamp is slipped over the arm and bolted with the clamp side up ; and the machine is set in the saddle and swung into line for drilling. 6. To swing the machine so as to drill another hole, the safety clamp is not released until the drill has been pointed in the direction of the new hole ; then it is released and clamped in the new position. 7. To dismount the machine, remove the drill steel, re- lease the safety clamp and slacken the arm bolts, so that the machine may be lowered gently by the driller as far as it will go, and the machine removed from its saddle. 8. In starting a hole on a face of hard, slanting rock lower the machine a little on the bar and drill a few inches, then raise the machine and catch the edge of the hole thus started. Use of Water in Drilling. A simple and very effec- MACHINE DRILLS AND THEIR USE. 43 live method of increasing the number of feet of hole drilled in soft rock is the use of a water jet to wash the sludge out of the hole as fast as it forms. Fig. 5 shows a drill with a small water pot, pipe and hose equipment for throwing a jet of water into the hole during the drilling. The water pot holds eight gallons and is provided with an air pipe, through which compressed air enters to force the water out through the nozzle. This air pipe is attached to the side of the drill cock. The eight gallons will last an hour or two, depending upon how steadily the machine is running ; and a boy can keep a large number of water pots supplied with , water. The nozzle may be a piece of ^-in. gas pipe drawn j? f ( down to a fine point at the end, and it should be pushed into ' the hole as the drill advances. In running an adit or drift water may be supplied by gravity from an upper level. Mr. H. P. Stow, of California, is authority for the fol- lowing data (Mining and Scientific Press) showing the ef- fectiveness of a water jet in drilling: "Three rounds were drilled by the same miner, using a 2*4-inch drill, drilling the same number of hours, size, and as near as possible the holes were of the same kind. Two of the rounds were drilled without taking down the bar, and the third was put in alongside of the other two. He drilled one round without water, one with water, bailing from a bucket, the usual method ; and the third with water under pressure in a hose. Without water he drilled 32 ft., using 38 drills; with water by bailing, 41^4 ft., using 33 drills; and with water from the hose, 52 ft., using 37 drills that is. a gain of 30 per cent, depth of holes, and 50 per cent, gain of feet per drill, with bailing over drilling dry; a gain of 62^/2 per cent, of depth of holes and 66 2-3 per cent, gain of feet per drill, using the hose over drilling dry ; and a gain of 24^2 per cent, depth of holes, and n,per cent, of feet per drill by using hose over bailing water from a bucket. All of which shows that there is not only a gain of ground drilled, but a saving of drill bits used by using water under pres- 44 ROCK EXCAVATION METHODS AND COST. sure, instead of bailing it from a bucket or not using it at all. Besides the actual gain in drilling the 'pressure-water' is a saving in getting rid of the gases in the pile of dirt and the dust formed in drilling, resulting materially in the better health of the men, freedom from powder headache and min ers' consumption, and increased rapidity of getting into the face to remove the dirt. "The accompanying illustration, Fig. 5, shows a portable outfit arranged by the Rix Compressed Air & Drill Co., San Francisco, Cal. It consists of a galvanized pot with a bail, holding eight gallons of water, and which, the manufacturer says, has been tested to 150 Ibs. per sq. in. pressure. This pot has openings for admitting air pressure on the water, for attaching the water hose, for filling and for releasing the air when filling is required. There are two small pieces of hose, one for admitting the air and one for the squirter. The air hose is attached to the side of the drill cock and lightning couplings are used. "The superintendent of the North Star mine at Grass Val- ley, Cal., writes the manufacturers : 'For clear water, we put up small barrels on each level, or in the most convenient place where there is a drip, and run the clear water into this barrel, which is also protected from dust or dirt. A faucet is placed at the bottom. A boy with a heavy galvan- ized watering pot, filled with a small nozzle, distributes the water to the tanks. A tank of water lasts for some time. It depends on how steadily the machine is running and how careful the man is about shutting off the water when not using it. It will last at least an hour or two anyway, and one boy can keep forty tanks supplied under reasonable con- ditions of water supply.' ' Concrete is exceedingly troublesome material in which to drill deep holes ; but water under pressure has been used very effectively with a wide flare bit which permitted a small copper water pipe to be inserted nearly to the bottom of the hole. The chips and dust were thus carried off by the water MACHINE DRILLS AND THEIR USE. 45 before they could wedge the bit, enabling drilling to be done for 25 cts. a ft. at a profit where previously it had been done at a loss. Other Types of Machine Drills. The Leyner drill is an American drill especially adapted for use in rock where a water jet enables a bit to cut faster. The Leyner drill has a hollow drill rod through which the compressed air forces the water which escapes through holes near the bit. A small steel water tank having a capacity of 18 gals, is said to hold enough water for a shift's drilling. The compressed ',ir is said to be the principal agent in cleaning the hole, the water laying the dust and assisting in the cleaning. The drill steel is not fastened to the drill piston, and is not churned up and down in the hole, but is struck by the piston, which also rotates the drill bit automatically. This drill, therefore, acts like a hand hammer drill, whereas the com- mon type of drill acts like a hand churn drill. The Randt rotary drill (see page 333) is a European drill which is driven by hydraulic motors, the water being under great pressure. The bit is held against the rock by hydraulic pressure and is rotated slowly, its cutting teeth chipping off the rock. For tunnel work it has proved effective, but it is not likely to be used for open cutting because of the neces- sity of forcing the bit against the rock, which would involve loading it with great weights. The pneumatic plug drill (see page 189) is simply a pneumatic hammer used for rivet- ing. It may or may not have a device for automatically rotating the bit. Being a small machine, it is efficient only for drilling shallow holes. I can find no reliable record of its use for holes more than I ft. deep. For drilling plug and feather holes, and for block holing boulders and large rocks, this type of drill is destined to have an ever-increasing use. It has already been introduced into several mines and into a large number of dimension stone quarries. Contractors will eventuallv use it for block holing big rocks in open cut excavation. 46 ROCK EXCAVATION METHODS AND COST. The Shaw Pneumatic Tool Co., of Denver, has recently put on the market a pneumatic plug drill with a light column upon which it may be mounted. The drill is held against the rock by air pressure, thus relieving the driller of the strain and jar incident to holding it in his hand. Another feature of the Shaw drill is a small hole through the drill steel, through which the exhaust air passes and forces the dust from the hole, a spray of water being used to lay the dust. Electric drills (see page 93) have been on the market for a good many years without making much headway in point of numbers in use. It is not improbable, however, that for certain classes of drilling they will eventually find a wide field of usefulness. I reserve for future editions a discus- sion of their features, trusting that users of electric drills will be kind enough to send me data of actual results under given conditions. The Automatic Gasoline Rock Drill Co., of San Francisco, has recently introduced a drill operated by gasoline. The explosion of the gasoline in the cylinder drives the piston. Provision is made for taking care of the exhaust and the heat generated by the gasoline explosions. The chief claim made for this drill is that, by its use, steam boilers and com- pressor plants are dispensed with. This is a type of drill that may prove very economic. CHAPTER IV. STEAM AND COMPRESSED AIR PLANTS. Upon the selection of a power plant for drilling, the profits of rock excavation largely depend. Whether to use com- pressed air or steam for open-cut excavation is often deter- mined purely by guess work. I have asked several engin- eers and managers of air compressing plants to explain why it is that compressed air is efficient for drilling in spite of steam engine inefficiency, and invariably the answer has been to the effect that when steam is used direct in the drills there is a great loss of energy in the heat that is constantly radiated along the steam pipe line. One manager said : "It's like trying to heat the wide, wide world with your steam pipe line as the radiator." This sounds plausible, and I doubt not is believed by many to offer a full explanation of the fact that steam operated drills are not economic in the consumption of coal; but that this reason is very far from the truth we shall see presently. Indeed, if the greatest loss of fuel energy came from heat radiated by the steam pipe line, the loss could be practically stopped by the very simple expedient of surrounding the pipes with a lagging of as- bestos, hairfelt or the like. The great loss comes from a different source entirely, as will be made clear. Heat Energy and Horse Power. The work required to raise I Ib. to a height of 33,000 ft., or to raise 33,000 Ibs. to a height of I ft. is 33,000 ft. Ibs. (foot-pounds), and if this work is done in I minute, it is I horse power (i H. P.) It has been found by experiment that if 778 ft. Ibs. of work be expended in churning up I Ib. of water, the temperature of the water will be raised i F. (F. signifies that the common Fahrenheit thermometer is used in measur- 47 48 ROCK EXCAVATION METHODS AND COST. ing the temperature). Hence I Ib. cleg.* = 778 ft. Ibs. Since I H. P. 33,000 ft. Ibs., and since 778 ft. Ibs = i Ib. deg., we see that I H. P. = 33,000 ft. Ibs. -f- 778 ft. Ibs. = 42.42 Ib. deg. per min. In a word, if 42.42 Ibs. of water are heated I degree per minute, the heat energy is exactly equivalent to I horse power. By reference to "steam tables" in any mechanical en- gineer's hand book it is found that to make I Ib. of steam at 70 Ibs. per sq. in. gage pressure requires 1,146 Ib. deg. of heat energy, if the water from which the steam is made is at a temperature of 60 F. to begin with. Now we have seen that 42.42 Ib. deg. per min. = i H. P. ; therefore since there are 60 mins. in an hour 60 X 42.42 = 2,545.2 Ib. deg. are equivalent to I horse power per hour. Dividing 2,542.2 Ib. deg. by 1,146 Ib. deg., we have 2.22 Ibs. of steam (at 70 Ibs. gage pressure from water at 60 ) as the equivalent of i H. P. That is if one horse power were exerted for an hour in churning up water, the heat developed would be equivalent to making 2.22 Ibs. of steam. Reversing the op- eration, if there were absolutely no losses of any kind, by radiation or otherwise, in the engine, 2.22 Ibs. of steam per hour would develop i H. P. ; but in practice there are many unavoidable losses in the best of steam engines. The ex- haust steam itself carries away a tremendous amount of energy that is lost. The following table shows in a striking manner how inefficient the steam engine is at best: Lbs. of Steam Kind of Engine. Theoretically Perfect (steam at 70 Ibs. gage from water at 60) . . . Compound (good) per I. H. P.f per hr. 2.22 15 to 20 Steam Efficiency. 1 00% 14.8% to 11.1% Single Condensing 23 7% Large Non-condensing (good) .... Average Size Condensing Small Non-condensing 28 30 30 to 6 s ? 8% 7-4% 7.4% to 3.4% * The expression "pound degree" abbreviated to "Ib. deg." will be used in- stead of the common but cumbersome expression, "British thermal unit" (B. T. U.). When 2 Ibs. of water are heated so as to raise its temperature 30 degrees, the heat energy imparted to the water is 2 X 30 = 60 Ib. degs., which is more in keeping with our system of indicating work in foot-pounds than to say 60 B. T. U. f I. H. P. is "indicated horse power" as measured with a steam indicator; STEAM AND COMPRESSED AIR PLANTS. 49 When we stop to consider what these figures mean, we wonder how an air compressor run by a steam engine can possibly compete with steam used direct in the drill; for if the heat efficiency of the engine that drives the compressor is only n per cent., it means that out of every 100 Ibs. of steam only n Ibs. are utilized to their fullest value, and that 89 Ibs. virtually escape into the air without doing any useful work. But even this low efficiency does not mark the end of the losses in an air-compressing plant, for the act of com- pressing the air raises its temperature, and if the temper- ature is not kept constant during the process of compres- sion a certain amount of useless work is done by the com- pressor engine. The Work of Compression. If, by means of circulating water, it were possible to prevent the temperature of air from rising during the process of compression, the efficiency of compression would be 100 per cent. ; but if the temper- ature is permitted to rise the air is expanded accordingly and exerts a back pressure upon the engine. Then as the compressed air quickly loses this high temperature in the re- ceiver and in the pipe line, it loses some of its pressure, which represents just so much wasted energy. It is customary to rate air compressors by the number of cubic feet of "free air" that the compressor will compress to a given gage pressure per minute. By "free air" is meant the ordinary air at sea level and at a temperature of 60 F. The volume of the compressed air as compared with free air is given in the fourth column of Table IV. The standard practice for large plants now is to compress the air in a low-pressure compressor, pass the air through an "inter-cooler," and then finish the compression to, say, 75 Ibs., in a high-pressure compressor. This raises the effi- ciency of compression to about 84 per cent. B. H. P. is "brake horse power" as measured with a Prony brake. The B. H. P. of an engine is from 10 to 20 per cent, less than the I. H. P., due to the fric- tion losses in the engine. 50 ROCK EXCAVATION METHODS AND COST. Table IV. gives the number of horse power required to compress air under the most favorable and under the worst possible conditions. TABLE IV. BRAKE (OR DELIVERED) HORSE-POWER REQUIRED TO COMPRESS ONE CUBIC FOOT OF FREE AIR PER MINUTE TO A GIVEN GAGE PRESSURE. (HASWELL.) HI lli 50 .1195 .0951 .2272 55 -1270 .0994 .2109 60 .1342 .1040 .1968 65 .1403 .1081 .1844 70 .1472 .1124 .1735 75 -1537 -1163 -1639 80 .1597 -1193 -1552 85 .1655 .1224 .1474 90 .1710 .1256 .1404 95 -1763 -1289 .1340 100 .1815 .1312 .1281 For the purpose of comparing compressed air with steam Table V. will be found useful : TABLE V. STEAM VOLUME AND TEMPERATURE AT GIVEN PRESSURES. Gage Pressure, Temperature, Lb. Degs. from Cu. ft. occupied by Lbs. per sq. in. Fahrenheit. Water at 32. i Ib. of Steam. 50.3 297.8 1,172.8 6.53 55-3 302.7 1,174-3 6.09 60.3 3074 1,175-7 5-71 . 65.3 3H.8 i,i77.o 5-37 70.3 316.0 1,178.3 5.07 75-3 320.0 1,179-6 4-8 1 80.3 323.9 1,180.7 4-57 85.3 327.6 1,181.8 4-36 90.3 331.1 1,182.9 4.16 95-3 334-5 1,184.0 3-98 100.3 337-8 1,185.0 3-82 Before we discuss the relative efficiency of air and steam it will be best to consider the amount of power required to operate a drill. * Adiabatic. t Isothermal. STEAM AND COMPRESSED AIR PLANTS. 51 Tests of Air Consumed by Drills. There are very few re- liable tests on record showing the actual air consumption of drills, yet data of some kind must be used by every engineer who has to determine the size of compressor plant needed to operate a given number of drills. The data given in cata- logues will not satisfy many engineers. I have, therefore, given considerable space to such records of actual tests as I could find, and to the discussion of the tests compared with catalogue data. By all odds the most satisfactory records of actual air consumption of drills are to be found in a paper by Messrs. J. B. Carper, E. Goffe and W. C. Docharty, re- cently read before the Mechanical Engineers' Association of the Witwatersrand. Some very interesting data are given of the air consumption of a number of English and American rock drills. The authors state that they endeav- ored to conduct a fair and unbiased trial of all the rock drills procurable, which represent nearly all of those on the Jo- hannesburg market. The object of the trials was to obtain the quantity of air consumed by the different makes and sizes of drills while doing the same work. The method of making the tests was as follows : All the holes were drilled in a block of red granite, 2 ft. thick, hav- ing the same density and hardness as that of Peterhead granite. The block was bedded in concrete, and the drills were mounted on a quarry bar supported by A frames firmly set in concrete. All holes were drilled vertically. There were two air receivers, 5 X 20 ft. each, having a combined capacity of 757 cu. ft. The air compressor was worked until the gage on the receivers showed a pressure of 80 Ibs. per sq. in. ; then the stop valve was shut, closing connection with the receiver. Drilling was then begun with the machine to be tested, and continued without intermission until the gage registered 70 Ibs. The machine was then stopped, and the depth and diameter of the hole carefully measured. A similar run was made from 70 to 60 Ibs., and so on down to 35 Ibs. pressure. In working out the results the capacity 52 ROCK EXCAVATION METHODS AND COST. of the receivers was calculated for every pressure (80 down to 35 Ibs.), corrected for temperature, and the air consump- tion reduced to the equivalent of free air at 70 F. and 24.8 ins. barometer. The first set of tests was upon 14 drills having 3*4-in. cylinders and using 3-in. bits. Space will not permit re- printing the tabulated results of all these tests but I have calculated the average results of the tests on 13 of the drills, eliminating one drill which behaved in a very erratic man- ner, and likewise eliminating a few individual runs which showed great departure from other performances of the same make of drill. The following table gives the average results of 13 drills having 334~ m - cylinders and using 3-in. bits: TABLE VI. Air pressure, Ibs 80-70 70-60 60-50 50-40 40-35 Cu. ft. free air per min 124 117 100 70 60 Cu. ft. free air per lin. in. of hole.. 95.3 106.4 100.0 116.4 120.0 Cu. ft. free air per cu. in. of hole. . 13.3 14.8 13.8 15.0 16.6 Lin. ins. drilled per min 1.3 i.i i.o ' 0.6 0.5 In studying this table we see that the air consumption per inch drilled is somewhat erratic, but it was much more er- ratic in individual tests. The reason for this may be ascribed in part to the lack of uniformity in the granite, in the personal equation of the driller and in the efficiency of the drill itself at different air pressures. Doubtless the tem- pering and sharpening of the bits had a marked effect also. Each drill, it should be stated, was run by men selected by the agent of the drill, so that the personal equation becomes a factor of importance. However, the personal equation of the driller is by no means of so great importance on short continuous runs like these as upon runs several hours long. In the trials each run was about 6 mins. long ; that is, a run of the drill during the drop of 10 Ibs. in air pressure con- sumed on the average about 6 mins. One thing, however, is strikingly and consistently shown in the above tabulation, namely, the rapid falling off of STEAM AND COMPRESSED AIR PLANTS. 53 inches penetrated per minute with every drop in the air pressure. With air pressure averaging 75 Ibs. we note that 1.3 ins. per min. were drilled, as against only 0.6 ins. per min. under an average pressure of 45 Ibs. The lesson that this teaches is that it does not ordinarily pay to overload an air compressor with more drills than it is designed to carry, and that it never pays to use a main pipe so small as to reduce the air pressure materially. It is interesting to note that American drills were well in the lead of competitors. The best record of all the 3^4-in. machines was made by a Rand "Slugger." Using a 3-in. bit this drill showed the following results : TABLE VII. Air pressure, Ibs 80-70 70-60 60-50 7,583 50-40 40-35 80-35 8.550 11.666 6.416 41.381 Length of run, mins. . 7.166 Cu. ft. of free air per min 91.1 84.9 76.4 52.8 46.1 69.2 Cu. ft. of free air per lin. in. of hole... . 61.5 76.9 78.0 96.7 105.3 78-3 Cu. ft. of free air per cu. in. of hole. ... 8.70 10.80 11.04 13.68 14.90 11.08 Linear inches per min. 1.48 i.io 0.98 0.54 0.44 O.88 The excellence of the performance of this drill is well shown by comparing the results of its test with those above given as the average of 13 drills of the same size. Mr. Docharty attributes the poor showing made by most of the drills to poor valve design resulting in cushioned blows ; and he suggests that perhaps a study of these tests will lead some of the manufacturers to improve their valve designs. There were only four 3-in. machines tested, and, while in some instances the results were erratic, the air consumption and speed of drilling (3-in. bits) correspond very closely with the data above given for the 13 larger drills. It should be remembered, however, that no tests were made in deep holes, for under those conditions the larger machines would doubtless show their superiority. The fact that only shallow vertical holes were drilled should not be lost sight of in con- sidering these tests. 54 ROCK EXCAVATION METHODS AND COST, One of the most valuable of the tests made was one with a 2^4-in. Rand "Slugger," using bits of different size, li has been claimed that the depth of hole drilled in a given time should vary inversely as the area of the hole, but there is little in the way of actual tests to substantiate this claim. While too much reliance should not be placed upon one or two tests, the following data tend to prove that in drilling granite the speed of drilling varies inversely as the square of the diameter of the bit. A 2%-in. "Slugger" with a 6 I /4~ir\. stroke gave the following results : TABLE VIII. Air pressure Ibs 80-71 71-67 60-52 50-44 80-44 Diam. of bit, ins 2Yi 8 2 2% 2% 2 to 2^ Length of run, mins 8.08 1.08 9.25 6.83 25.25 Ins. drilled per min 2.19 3.81 1.81 0.95 1.78 Cu. ft. free air per min... 72.5 224.2 50.2 47.3 64.0 " " " " " Hn. in. 33.0 58.8 27.7 49.7 35.8 " cu. in.. 9.88 18.72 7.83 14.03 10.45 Air pressure, Ibs 80-70 70-60 60-50 50-40 40-37 80-37 Diam. of bit, ins,... 3Vie 3Yie 333 3 to 3Y* Length of run, mins.. 8.75 8.0 10.25 13-6? 5o8 45.75 Ins. drilled per min.. 1.08 0.64 0.69 0.56 0.51 0.70 Cu. ft. free air per min 69.7 72.0 56.8 43.8 33.2 55.4 Cu. ft. free air per lin. in 64.2 112.4 81.7 77.3 64.3 78.9 Cu. ft. free air per cu. in 8.75 15.26 11.56 10.93 9.11 11.09 It will be seen that with a bit of 2 1 / 16 ins. in diam., the average speed was 1.78 lin. ins. of hole per min.; but with a bit of 3 1/32 ins. in diam., the average speed was only 0.70 lin. ins. per min. A similar series of tests with a Climax machine of the same size gave an average of i.i lin. ins. of hole per min. with a 3-in. bit, as against 1.85 lin. ins. with a 2-in. bit. So far as I know these are the only published tests of drilling done under precisely the same conditions with bits of different diameters, and it is much to be desired that further tests be made on different kinds of rock to STEAM AND COMPRESSED AIR PLANTS. 55 establish the ratio of speeds using different sized bits in the same drill. In a rock that makes sludge rapidly as for example shales, slates, and some porphyries, a drill using water under pressure for washing out the sludge will readily ex- cel drills which depend upon the "chuck-tending" of the drill helper. As illustrating this point Table IX shows that the Leyner- Water drill showed up very poorly in compari- son with other drills in these tests for air economy ; yet this same Leyner- Water drill has made some remarkable records (page 78) in competition with other drills working in softer rocks which make sludge rapidly. Apparently the agents of the drills themselves did not in every case appreciate the difference in results that occur in drilling different kinds of rock, nor do the authors of this valuable paper mention this factor as being one of importance in comparing drill efficiencies. TABLE IX. TEST OF LEYNER- WATER DRILL. (Bore, 3 ins.; stroke, 3 ins.; weight, 156 Ibs.) Air pressure, Ibs 80-70 70-60 80-70 70-60 80-60 Diam. of bit, ins 2*/ u 2 L / lt 2 l /s 2% 2 1 /i 6 -2 l / Length of run, mins.. 5V 3 6Ye 7 6*/2 25 Ins. drilled per min.. . 1.50 1.37 1.21 1.25 1.32 Cu. ft. free air per mini. 115.2 100.8 86.9 93.8 98.2 Cu. ft. free air per Hn. in 76.8 73.1 71.6 75.0 74.1 Cu. ft. free air per cu. in 23.0 21.89 20.2 21. 16 21.52 Test of Air Consumption at the Rose Deep Mine. A 6-hr, run at the Rose Deep Mine, South Africa, showed the fol- lowing results for 31 drills: The compressed air averaged 70 Ibs. per sq. in. and each 3^-in. drill consumed 81 cu. ft. of free air per minute, including all leakage of pipes (there was less leakage than is common in mines). Each drill re- quired 43 Ibs. of coal per hour, to supply this compressed air; and each pound of coal developed 3.4 H. P., per hour, 56 ROCK EXCAVATION METHODS AND COST. by the indicator on the steam engine, evaporating 6.74 Ibs. of water from 212 F. The average horse-power of the compressor engine was 12.7 I. H. P. per drill; but all the drillers were trying to make a record and accomplished in 6 hrs. an amount of drilling that ordinarily took 8 hrs. It was an efficient steam power plant, as is seen by the fact that 3.4 H. P. were developed with each pound of coal. The power plant was a vertical King-Reidler Compound Steam' Engine and Double Stage Air Compressor with two boilers of the horizontal return tubular type. The engine developed 393 I. H. P. and had a mechanical efficiency of 86 per cent. There were several sizes of machine-drills used, but they were all reduced to the 3^4-in. size as standard by the test of filling the cylinders, ports, etc., with water and ascertaining the volume of water for each drill cylinder. This showed the rating of the drills in air consumption to be as follows: Relative Air Consumption 2 l / 2 -\n. drill ' 0.445 3%-in ' i.ooo 3 5- T 6-in 1.069 32lHn 1.123 The 31 drills averaged 4.5 ft. of hole drilled per hour for the 6-hr, run; one 3>^-in drill making 52 ft. of hole in 6 hrs., drilling 4 dry holes. Comparing the consumption of 81 cu. ft. of free air per min., at 70 Ibs., with the average of 1 20 cu. ft. (at 70 Ibs.) given in Table VI, gives a fair idea of the difference between a long test using a number of drills, and a short test of one drill. For purpose of comparison I would add that a recent gov- ernment report states that 2,300 air drills are in use in South Africa, 70 per cent, of which are 3^-in. drills, and each drill requires 12 I. H. P. of steam engine to run the two- stage air compressors that supply the air. Tables of Air Consumption in Catalogues. Table X is given in the catalogue of one of the well-known drill manu- facturers, and is said to be based upon actual tests of single STEAM AND COMPRESSED AIR PLANTS. 57 drills running continuously without stops for changing bits, etc. TABLE X. CUBIC FEET OF FREE AIR PER MINUTE REQUIRED TO RUN A ONE- DRILL PLANT. B >> ^o ^ d'^' a N. Y. Air Cell (asbestos) 2 i 3.22 12.32 26 187 Cast's Air Cell (asbestos) 2 15/16 3.77 10.56 23 198 Carey's Moulded 2 i 5.77 8.64 20 192 Asbesto-sponge 2 i 7.25 8.64 . . 194 Asbestocel 2 % 5.10 9.60 22 182 Magnesia '. 2 i 3.17 40 143 Asbesto-sponge (48 lams.) 2 i 6.00 19.20 37 143 Asbestos, Navy brand... 2 i^ 3.69 18.24 35 151 Asbestos, Navy brand... 10 i^ 12.60 66.0 25 97 Magnesia 10 13/16 17.88 62.7 24 88 Asbesto-sponge felt 10 i^ 28.55 73-3 28 70 Asbesto-sponge felt 10 13/16 24.47 54-O 21 75 Bare iron pipe 2 750 According to Mr. Barrus, the number of Ib. degs. (or B. T. U.) of heat radiated through a pipe covering is in- versely proportional to the thickness of the covering raised to the y% power ; according to H. G. Stott, the heat radiated 62 ROCK EXCAVATION METHODS AND COST. is inversely proportional to the square root of the thickness of the covering. The heat losses, given in the last column of Table XIII., are for a difference of temperature of 250 F. between the steam and the outside air ; for any other dif- ference in temperature the heat loss is proportional to the ratio of the differences in temperature. The heat losses are given per square foot of the outside surface of the pipe ; but to be truly scientific they should be given per square foot of the outside surface of the pipe covering. However, for the tests of pipe covering made on a 2-in. pipe, the results show a slightly higher heat loss than would occur on larger pipes, so that the tabular data are on the side of safety. Since, according to Table V., i Ib. of steam of 75 Ibs. pres- sure contains 1,179 Mb. degs. of heat energy from water at 32, or 1,151 Ib. degs. from water at 60, we have simply to divide the loss of heat expressed in Ib. degs. by 1,150 to get the number of pounds of steam lost in a pipe line per hour. At 70 Ibs. gage pressure the loss is 750 Ib. degs. per sq. ft. of bare pipe surface ; hence 750 -f- 1,150 = 0.66 Ibs. of steam per sq. ft. per hr. Roughly speaking, therefore, an uncovered pipe loses 2-3 Ib. of steam per sq. ft. per hr. The following table gives the area in square feet of 100 ft. of pipe: TABLE XIV. r i M-i r i 4-i r i M-I J3 6 13 | 3 o **"* *3 i)* 4 " *3 4> **" 4, 3 d 0> 14 "* (_) p | *[ s & cr 45 'S* y z 22.2 75-2 6 173-3 y 27-5 3 91.7 7 198.0 I 344 3/2 104.7 8 225.2 iy 4 43-5 4 117.8 9 250.0 1/2 49-8 4/2 130.7 10 281.7 2 62.1 5 159.0 Since the heat loss in uncovered pipe is about 2-3 Ib. of STEAM AND COMPRESSED AIR PLANTS. 63 steam per hr. per sq. ft. of pipe surface, we have merely to multiply the number opposite the pipe of given size in Table XIV. by 2-3 to determine the approximate loss of steam. In a 24 -in. pipe the area is 27.5 sq. ft. per 100 lin. ft. of pipe ; hence the steam loss is 2-3 X 27.5 = 18.3 Ibs. of steam per hour. If the pipe is 150 ft. long the loss is 27^ Ibs. of steam per hour, due to radiation, at least 80 per cent, of which loss can be saved by using a pipe covering little more than an inch thick. Pipe coverings can be bought in short lengths that slip like sleeves over the pipe. For outdoor use the cover- ing should be of some flexible variety, preferably of asbestos fibre (not moulded hard with plaster), wrapped with water- proofed canvas. A fair idea of the prices may be had by in- specting Table XIII. In a compressed air pipe line there is no loss of energy by heat radiation ; hence the larger the pipe the greater its effi- ciency in conveying the air without reducing its final pres- sure at the drill. But in a steam pipe line the larger the pipe the greater the loss by heat radiation, whereas the smaller the pipe the greater the loss by friction. Hence for any given quantity of steam to be delivered per hour there is just one size of pipe that will give a minimum loss of energy, which may be calculated from the data given in this chapter. Flow of Air Through Pipes. Tables XV. to XVII. are based upon D'Arcy's formula. Table XV. gives the number of cubic feet of free air delivered per minute through a pipe loo ft. long without any loss of pressure. Table XVI. gives the factors, F., to be used for different lengths of pipe. Table XVII. gives the multipliers, M, to be used to determine the loss of pressure. The following formulas are to be used with these tables : Q : (1) Q = LXFXM FXM Q O (2) M = (A\ F ~- L X F ' L X M Q = cu. ft. of free air discharged per min. L = factor given in Table XV. 64 ROCK EXCAVATION METHODS AND COST. F = factor given in Table XVI. M= " " " " XVII. Example i. Given a 4-in. pipe, 600 ft. long, initial air pres- sure 60 Ibs., required to discharge 1,200 cu. ft. of free air per min., what will be the terminal pressure? By Table XV., under 4-in. pipe and opposite 60 Ibs., we find L = 1,535. By Table XVI., for 600 ft., F = 0.408. Hence, M = ., *~ p = 1,200 ^ LXF 1,535x0.408 Now by Table XVII., opposite 60 Ibs. pressure and under 4 Ibs. reduction, we find M = 1.89, so that the loss of pres- sure being 4 Ibs. we have a terminal pressure of 56 Ibs. Example II. Given a 6-in. pipe, 2,000 ft. long, initial pres- sure 80 Ibs., terminal pressure 70 Ibs., what will be the volume discharged? By Table XV., under 6-in. pipe and opposite 80 Ibs., we find L = 4,971. By Table XVI, for 2,000 ft. length, F = 0.224. By Table XVII., under 10 Ibs. reduction and for 80 Ibs. pressure, we find M = 2.82. Q = LXFXM = 4,971 x 0.224 x 2.82 = 3,140 cu. ft. per min. TABLE XV. GIVING FACTOR L. Nominal Diameter of Pipes in Inches. Gage, , * Lbs. i" iy 2 " 2" 2Y 2 " 3" sW 4" 5" 6" 7" 8" 10" 50 38.96 122.4 2 434 396.3 701-5 1030 1430 2558 4114 5993 8312 14910 60 41.83 131.4 261.1 425.4 752.9 1105 1535 2747 4416 6433 8920 16000 70 44.53 139.9 278.0 452.9 801.8 1176 1634 2925 4701 6848 9499 17030 80 47.08 147.9 294.0 478.8 847.6 1244 1728 3091 4971 7240 10040 18000 90 49.54 155.6 309.3 503.8 891.8 1307 1817 3253 5230 7619 10560 18940 100 51.88 163.0 324.0 527.5 933.8 1370 1904 3407 5477 7979 11050 19850 1 10 54.10 169.9 337-8 550.1 973.9 1429 1985 3552 5712 8320 11530 20690 125 57.15 179-5 356.8 581.3 1028 1510 2097 3754 6034 8789 12180 21860 150 62.10 195.1 387.8 631.7 1117 1641 2280 4080 6558 9553 13240 23760 STEAM AND COMPRESSED AIR PLANTS. 65 TABLE XVI. GIVING FACTOR F. Length, feet. Multiplier F. Length, feet. Multiplier 100 I.O 6000 0.129 200 0.707 7000 0.119 300 0-577 8000 O.I 12 400 0.500 9000 0.105 500 0.447 IOOOO 0.100 600 0.408 12,000 0.0912 750 0-365 15,000 0.0817 IOOO o 116 1250 0.283 *** JW moo 0.258 * JW 2OOO w.^^*-r O 224 2500 \J.lii+ 0.200 3000 3500 0.169 0.158 0.141 TABLE XVII. Initial Gage Pressure. Pounds. 50 60 70 80 90 R i 0.984 0.986 0.988 0.989 0.990 0.991 o.99'2 0-993 0.994 GIVING FACTOR M. eduction of the final pressure in pounds per square inch. 234 6 8 10 12 14 16 18 20 37 1.65 .87 2 22 2 48 2 67 . . . .37 1.66 .89 2.24 2.52 2.74 .38 1.67 .90 2.27 2.56 2.79 2.97 3.12 3.24 .38 1.67 .91 2.29 2.59 2.82 3.02 3.19' 3.32. 3.43 3.53 .38 1.68 .92 2.31 2.61 2.86 3.06 3.24 3.39 3.51 3.61 .39 1.68 .93 2.32 2.63 2.88 3.10 3.28 3.44 3-57 3-69 39 1-69 -93 2-33 2.64 2.90 3.13 3.32 3.48 3.63 3-75 .39 1.69 .94 2.34 2.66 2.93 3.16 3.36 3.54 3.69 3.83 .39 1.70 .95 2.36 2.69 2.97 3.21 3.42 3.61 3.77 3.92 100 no 125 150 Fuel and Steam Boiler Efficiency. Steam boilers are com- monly rated as having so and so many horse-power capacity. This is a very misleading and unsatisfactory way of rating a boiler, for the horse power of work that a boiler can do depends entirely upon the kind of engine to which the steam goes. A boiler that supplies 1,600 Ibs. of steam per hour to compound condensing engine using 16 Ibs. of steam per H. P., evidently develops 100 H. P. ; yet if this very same boiler is made to feed an ordinary single cylinder non-con- densing engine using 40 Ibs. of steam per hour, it will de- velop 1600 -r- 40 = 40 H. P. In buying a boiler, therefore. 66 ROCK EXCAVATION METHODS AND COST. be sure to secure the manufacturer's guarantee, not of its horse power, but of its steam capacity in pounds of steam per hour at a given gage pressure (say, 70 Ibs. per sq. in.), using a fuel of a kind stated in the guarantee. The Amer- ican Society of Mechanical Engineers has recommended that wherever the word horse power is used in reference to boil- ers, it shall mean 30 Ibs. of water evaporated from 100 F. to steam having a gage pressure* of 70 Ibs. per sq. in. under average firing without forcing the boiler, and by forcing the same boiler should be capable of evaporating 1-3 more steam per hour than its ordinary rating; that is, a 100 H. P. boiler (30 Ibs. steam per hr. per H. P.) should be capable of de- veloping 133 H. P. if forced. Unfortunately manufacturers usually pay no attention to this suggested rating, and .perhaps they can hardly be blamed, because if it were al- ways followed we should see at times a 100 H. P. boiler used to run a 200 H. P. compound condensing engine, while at other times the same 100 H. P. boiler would be used to run a 100 H. P. non-condensing single engine. By careful tests it is easy to ascertain how many Ib. degs. can be developed by I Ib. of any fuel burning under perfect conditions. Thus I Ib. of perfectly pure carbon will develop 15,000 Ib. degs. ;. that is, it will raise the temperature of 15,000 Ibs. of water i, or 150 Ibs. of water 100. Coal is never entirely pure carbon, but contains some ash and other materials. All mechanical engineers' handbooks contain tables of the heating value of different kinds of fuel, with which it is well to be familiar whenever there is a choice of fuels. When coal is burned under a boiler a large percentage of its heat passes up the chimney in the gases and is lost ; and in addition to this loss the boiler itself radiates heat con- stantly. The greater part of the loss occurs in the heat that * The atmosphere has a pressure of 14.7 Ibs. per sq. in., and since a steam gage shows the steam pressure above atmospheric pressure, \ve must add 14.7 to the gage pressure to get the "absolute pressure." STEAM AND COMPRESSED AIR PLANTS. 67 goes up the chimney. In large, well designed boilers, proper- ly protected by asbestos or similar covering, the coal burned will develop steam to about 85 per cent, of the full heat value of the fuel ; the efficiency of the boiler and furnace is then 85 per cent. In locomotive boilers where forced draft is used, firing not of the best and boiler exposed to moving air, the efficiency is often as low as 45 per cent. The effi- ciency of a good boiler of moderate size (100 H. P.), well housed, is ordinarily about 75 per cent. A small (20 H. P.) boiler exposed to the wind has an efficiency of 55 to 60 per cent, when not forced. If a small boiler is used to run one drill, the boiler must always have up enough steam to keep the drill running at nearly full capacity; but when the drill is stopped, during the changing of bits, moving, etc., there is a waste of steam, because the period of stoppage is not long enough to permit the fireman to make any material change in the firing and in the draft. Hence one single drill (3^ in.) must be counted upon as using about 250 Ibs. of steam per hour (see page 58). A i-in. steam pipe 200 ft. long, if not covered, will lose nearly 50 Ibs. of steam per hour by condensation (and often as much more by leakage), thus making a total steam consumption of 250 + 5 3 Ibs. per hour, due to the drill and the pipe line. If I Ib. of the coal will develop 14,000 Ib. degs., and if the small exposed boiler has an efficiency of 58 per cent., we have 14,000 X 58 per cent. = 8,120 Ib. degs., which divided by 1,150 (the Ib. degs. required to pro- duce I Ib. of steam at ordinary pressures), gives about 7 Ibs. of steam produced by i Ib. of coal. Therefore, 300 -h 7 = 43 Ibs. of coal required per hour to supply steam for the drill and pipe line. We have still to add the loss of fuel when the fire is drawn at night, as well as the loss of radi- ated heat during the starting of the fire in the morning, and leakage losses. Not less than 150 Ibs. of coal per day are thus consumed in a small boiler, bringing the total coal con- sumption up to 580 Ibs. of coal for running the one drill 68 ROCK EXCAVATION METHODS AND COST. one lo-hr. shift. Where two drills are run by steam, the consumption of coal per drill is somewhat less. Where a large number of drills are in use, all are seldom running at the same time, but at no time is the boiler entirely without some drills drawing steam from it. Under such conditions, and where the main pipe line is lagged, each drill will require about 250 Ibs. of coal per lo-hr. shift under average con- ditions. Knowing the number and size of drills, the size of steam pipes, the character of lagging around the pipes, the depth of drill holes and kind of rock, it is possible to esti- mate the coal consumption per drill with considerable ac- curacy by applying the data given in this chapter and in the next chapter. Merits of Compressed Air. A compressed air plant was recently installed at a large stone quarry where drills and channelers had formerly been run by steam direct from a large number of small boilers. When the compressed air plant was installed the coal consumption was reduced from 50 tons per day to 15 tons per day. Due to the higher and more even pressure of the air (as compared with the steam from the small boilers), fewer drills and channelers were needed, because each did more work than before. More- over, there were no delays in the morning, getting up steam, as is usually the case where a large number of small boilers are operated. This excellent and remarkable result could have been accomplished at less expense by installing a cen- tral steam boiler plant and using lagged steam pipes. The steam pipes would have required expansion joints and traps for draining off water of condensation similar to those in the air pipe system. This plant was widely advertised as proving conclusively the advantage of using compressed air instead of steam in drills. What it really proves is that a central power plant is far more economic than a large num- ber of small plants. We have seen that the efficiency of small boilers is often 45 per cent, or lower, as compared with the 85 per cent, efficiency of large boilers. We have also STEAM AND COMPRESSED AIR PLANTS. 69 seen that a small boiler supplying one or two drills must al- ways carry enough steam to keep both drills going at their full steam consumption, in spite of the fact that the drills are not working more than 40 to 70 per cent, of the time ; where- as with a large central plant the drills "average up," some running while others are not, thus greatly reducing the average daily coal consumption. Compressed air has many advantages over steam for operating drills, but a reduction in the coal bill is not one of them (in spite of the general belief to the contrary) if a fair comparison is made between a cen- tral steam plant with covered pipes and a central compressor plant. Compressed air, however, possesses several advantages distinctly its own, which may be enumerated as follows : ( I ) It does not rot the hose from the pipe to the drill, and a much cheaper hose may be used and consequently a longer hose than with steam. (2) Less oil is required to keep the drill lubricated. (3) In warm weather the exhaust air makes working around the drill comfortable. (4) A trench or quarry pit is not filled with steam, making it difficult at times to see. (5) There is no danger of injuring the drill itself by sudden expansion due to heat. (6) There are no pipes to thaw out in winter due to condensed water care- lessly allowed to collect. (7) Plug drills can be used for block holing, plug and feathering, etc. (8) The air can be used for blowing the sludge and water out of a hole before charging. (9) The air can be used for forcing a jet of water into a hole alongside of the drill-rod. (10) The ma- chine being cool is easily handled, (n) Water power may be used for compressing the air. Efficiency of the Jerome Reservoir Plant. There are few records of careful tests of the efficiency of boilers, engines and air compressors of a single plant. In Saunders's "Com- pressed Air Information," p. 193, a very complete record is given of a lo-hr. test of a plant in operation, supplying air to 14 drills, 14 derrick engines and three small pumps. The 70 ROCK EXCAVATION METHODS AND COST. test was made by George W. Vreeland and Charles M. Younglove. The plant is used in excavating the site of the Jerome Park Reservoir, N. Y. (still under construction, 1904), and consists of one Ingersoll-Sergeant Corliss cross-compound condensing air compressor plant, receiving steam from two Hogan boilers, each of 270 H. P. (nominal). The follow- ing are some of the data of the test : Steam gage, Ibs. per sq. in 1 16.5 Coal used per hour, Ibs 928 Dry steam per hour, Ibs 8,274 Efficiency of boiler 78.1% Steam per I. H. P., Ibs 17.36 Total I. H. P. of engines 468 Total D. H. P. of engines 402 Mechanical efficiency of engines 86% Thermal efficiency of compression 82% Free air per min. per I. H. P., cu. ft 6 Gage pressure of compressed air, Ibs. 67.5 Heat supplied to engine per hr., Ib. degs 9,634,246 Heat utilized by engine- per hr., Ib. degs 1,177,437 This is an average size compressor plant, capable of car- rying at least 35 drills (3>4-in.) ; and if it were loaded with 35 drills, each drill would be charged with 265 Ibs. of coal, for a lo-hr. run, or 276 Ibs. of steam per hour, or with 13.4, I. H. P. of compressor engine. Particular note should be taken of the heat efficiency of the engine, which may be cal- culated by dividing the 1,177,437 Ib. degs. by the 9,634,246 Ib. degs., the quotient being 12.3 per cent. Those who have not made a careful study of the compressed air problem would be misled by the statement that the efficiency of com- pression is 82 per cent., and would be apt to think that this was for the engine and compressor plant. In fact the true heat efficiency of this plant was 12.3 X -82 = 10.086 per cent., a trifle more than 10 per cent. which checks closely with the calculations in the fore part of this chapter. Gasoline Air Compressors. Where not more than three or four drills are to be operated, probably no power can equal STEAM AND COMPRESSED AIR PLANTS. 71 compressed air generated by gasoline. One pint of gasoline per hour per brake horse power (B. H. P.) of gasoline engine may be counted upon as the average consumption. It will require about 12 H. P. to compress air for each drill (3^4-in. size) ; hence 12 pints, or i^ gals., of gasoline will be required per hour per drill while actually drilling. Since gasoline air compressors are self regulating, when the drill is not using air very little gasoline is burned by the gasoline engine driving the compressor. If the drill is actually drill- ing two-thirds of the working shift, we may safely count upon using about I gal. of gasoline per hour of shift per drill, or 8 gals, per shift 8 hrs. long. If gasoline is worth 15 cts. per gal., delivered at the engine, one drill consumes only $1.20 worth of gasoline per shift of 8 hrs. In shaft sinking, tunnel work and the like, as will be shown later, a drill is often idle two-thirds of the shift, so that the gasoline con- sumption would be still less. A gasoline compressor possesses other very important economic advantages over a small steam-driven plant. First, there is the saving in wages of firemen; for, once started, a gasoline engine runs itself. Second, there is the saving in hauling or pumping of water and the hauling of fuel. Third, the cost of gasoline is often less than the cost of coal for operating a small plant. The Golden Wave Mine, Congress, Ariz., used a 30 H. P. gasoline driven compressor (Fair- banks-Morse) for sinking an incline, at a cost that was re- markably low. I believe this type of plant is destined to find an increasing field of usefulness. It is especially adapted for rock trench excavation in cities, for tunnel work and for open cuts where only a few drills are operated. CHAPTER V. THE COST OF MACHINE DRILLING. Cost Factors, The items that go to make up the cost of power drilling are : 1. Wages of driller and helper. 2. Proportionate part of wages of engine and boiler crew. 3. Fuel. 4. Sharpening drills, including transportation to and from shop. 5. Repairs and renewals. 6. Interest and depreciation of plant distributed over the shifts actually worked. 7. Water and oil. 8. Proportionate part of general expenses, such as salaries of superintendent, office employees, rent, etc. 9. Installation of plant, including freight, hauling, setting up, dismantling, etc. I have enumerated these items because it is a common error to overlook one or more of them; and for the same reason I will now give the factors that determine the num- ber of feet of hole drilled per shift : 1. Character of rock, including resistance to drilling, pres- ence of seams, rapidity of formation of sludge or dust, etc. 2. The percentage of time required to change bits, to shift the drill and to set up. 3. The depth of hole. 4. The size of bits, top and bottom. 5. The use of water jets for removing sludge. 6. The form and sharpness of the bits. 7. The direction of the hole, up, horizontal or down. 8. The percentage of time lost in blasting, breakdowns, sticking of bits, etc. 72 THE COST OF MACHINE DRILLING. 73 9. The pressure of the air or steam at the drill. 10. The size of the drill cylinder. In publishing records of drilling costs, every one of the foregoing factors should be given, yet it is rarely that half of them are recorded. Indeed it is the custom to state merely the kind of rock, the name of the drill, and the cost in cents per foot of hole drilled without any statement as to rates of wages, price of fuel, or in fact any of the data needed to form an intelligent estimate of the applicability of the in- formation to other work. Percentage of Lost Time. In operating machines of any kind the percentage of lost time is a factor that should re- ceive the moct careful consideration. Notwithstanding the self-evidence of this fact, I have looked in vain for published records showing the average time lost in setting up, changing bits, cleaning hole, etc. Fearing that my own records of these extremely important items might not cover a suffi- ciently wide range of conditions, I prepared blanks which I sent to a number of contractors and mine managers. I was not surprised to receive some answers to the effect that conditions were so variable as to make such records of no practical value. Now, it was precisely for the purpose of determining the range of conditions that these blanks were sent out. Indeed, no perfect picture of conditions can be given except by the filling in of just such blanks. They tell at a glance whether the rock was easy to drill or hard; whether the sludge cushioned the blow of the bit or not; whether the drill crew was lazy or not, and, in a word, just what the conditions of operation were, so far as drilling was concerned. The most serious loss of time in machine drilling is the time lost in changing bits and pumping out the hole; for, with a 2-ft. feed screw (which is the ordinary length), a new drill must be inserted for every 2 ft. of hole drilled. It takes from 4 to 16 minutes, to drill 2 ft. of hole, counting the actual time that the drill is striking, and it ordinarily 74 ROCK EXCAVATION METHODS AND COST. takes from 2 to 10 minutes to change bits and pump out the hole. I have often timed work where 9 minutes were spent in drilling, followed by 9 minutes lost in changing bits. Counting no other time losses, then, half the available time was lost in the operation of changing bits. From the writ- ten reports that I have received, I am certain that few min- ing men and fewer contractors have ever given this phase of drilling any consideration at all, although, in my judg- ment, it is often the cause of a loss where there should be a profit. In all the literature on the subject of drilling, I have been unable to find a single mention of the importance of timing drilling operations with the minute hand of the watch. Where holes are drilled to a depth of 10 ft. or more, the drill steel becomes so heavy that change of bit is an opera- tion usually requiring 3 minutes. When done properly, the driller starts to raise the drill with the feed screw and at the same instant the drill helper begins to loosen the chuck with his wrench. Without any great effort these two opera- tions are finished at the same time, requiring about I minute. The pumping out of the hole with the sludge pump can be done by the drill helper in I minute, or less, but I have frequently seen deliberate workers take 2 minutes or more. The drill helper then puts a new drill into the hole and enters its shank in the chuck ; as soon as this is done the driller should begin to feed the drill forward, and the drill helper should at once tighten the chuck; these operations taking I to 1^4 minutes. After the first few blows are struck, it is often necessary to tighten the chuck again, consuming y 2 to 24 minute, but this can be obviated by using good chuck bolts and by training the men properly. The three necessary operations (removing bit, pumping, and putting in new bit) can be done with ease in 3 to 3^ minutes. If, however, the drill helper waits till the driller has raised the drill steel be- fore he begins loosening the chuck, another minute may be unnecessarily added to the time ; and, in a similar manner, by deliberation (which is equivalent to laziness) the two THE COST OF MACHINE DRILLING, 75 men may while away 6 minutes or more unnecessarily. When shallow holes (6 ft. or less), are to be drilled, the drill steel is light and there is often little or no sludge pump- ing to be done. In such cases it is possible for the driller and his helper to change bits in i minute, or even less when they are rushing the work. So far as the changing of bits is concerned the men should be made to work with a vim. When men have to exercise their muscles incessantly for 8 or 10 hours there is reason in taking a slow, steady gait, but in machine work, muscular exercise is intermittent and should be vigorous. Next in importance to the time lost in changing bits is the time lost in shifting the machine from hole to hole. This, again, is a factor not touched upon by writers, in spite of its importance, especially in drilling shallow holes. To move a tripod from one hole to the next and set up again ready to drill, seldom consumes less than 7 minutes, even when the two men are working rapidly, when the distance to move is short, and when the rock floor is level and soft. When, however, the rock floor is irregular and hard, requiring the vigorous use of gad and pick, not only in making holes for the tripod leg points to rest in, but requiring, also, some little time in squaring up a face for the bit to strike upon, the two men may consume from 30 to 45 minutes, shifting the machine and setting up, if they work deliberately. In such cases it is advisable to have laborers workinp- ahead of the drillers preparing the face of the rock, leveling the site of the hole, removing loose rock, etc. One can see clearly what a great saving in time may thereby be effected; yet, this simple expedient is seldom adopted; but the driller and his helper are usually left to themselves in preparing the ground for each new set up. I repeat aeain that everv foreman and manager of rock excavation should use the minute hand of his watch frequently (and at times when he is not ob- served), to determine exactly how much time his men are 76 ROCK EXCAVATION METHODS AND COST. losing in changing bits and shifting. He will thus learn where his employer's money is being wasted. Where drillers are obliged to move long lengths of air or steam pipe before blasting, or where narrow trenching makes it difficult to shift the drill and causes material delay in advancing the steam pipe line, there are obviously other sources of delay which should be ascertained by careful tim- ing, with a view to reducing the delay by some additional expenditure of money if found advisable. In seamy or soft rock where the bit sticks frequently in the hole the time lost from this cause alone may be 30 per cent. Excluding the time required to change bits for the new hole, we may say that two men can ordinarily make a new set up with a tripod in 12 to 15 minutes, if they work rapidly. When the drill is mounted on a column or bar, the time re- quired to set up the column and get ready to drill ranges from 10 minutes (when the men are racing) up to 60 min- utes (when the men are loafing). Men working deliberately ordinarily take about 25 minutes. From one set up of a col- umn, however, 6 to 12 holes may be drilled, by shifting the drill along the column. The shifting itself need not take more than I to 2 minutes, but the time required in addition for changing bits and cleaning the hole will not differ ma- terially from the time above given for tripod work. Tables XVIII and XIX give typical examples of actual work in different kinds of rock and in different parts of the United States. Part of the data was taken from my own notes, but I wish here to express my thanks for most of the data to the following mining and civil engineers: Mr. B. B. Lawrence, Mining Engineer ; Mr. E. C. Means, Min- ing Engineer ; Mr. Alex. Veitch, Mining Engineer ; Mr. R. Oilman Brown, Mining Engineer; Mr. T. H. Loomis, Civil Engineer; Mr. Walter Seeley, Civil Engineer. THE COST OF MACHINE DRILLING. 77 TABLE XVIII. AVERAGE TIME DRILLING VERTICAL HOLES. (Drill mounted on a tripod.) ABC D K Drilling first 2 ft., mins 9 10^ 12 8 14 Cranking out and removing bit, mins i z l / 2 i i l A *Y> Cleaning out hole, mins 3 i i/4 i /4 Putting in new bit and cranking back, mins... i 2^ i/4 i 1^2 Drilling second 2 ft,, mins 13 ioj^ .. .. 14 Drilling last 2 ft., mins 12 10^ 11 6 Moving machine from hole to hole and setting up IS 35 12 36 Air pressure, Ibs. per sq. in 70 (?) 80 70 70 Diameter of drill cylinders, ins 3% 3/4 3 1 A 3/4 3/4 Diameter of starting bit, ins 2 l / 2 2^/2 3% 2 2^ Diameter of finishing bit, ins i$4 iH i/4 i/4 2 Depth of hole, ft 12 6 20 12 6 Kind of rock Lm. S. Gr. Sd. Tr. Length of shift, hrs 10 10 10 10 10 Ft. drilled per shift 48 96 36 NOTE. The kind of rock designated by the abbreviations is as follows: Lm., limestone; S., sandstone (hard); Gr., granite; Sd., sandstone (soft); Tr., trap (diabase J. TABLE XIX. AVERAGE TIME DRILLING HOLES IN A BREAST. (Drill mounted on a column.) L 24 2 O 2 30 30 IO 40 70 5-5 SI. 7 10 25 Note. The kind of rock designated by the abbreviations is as follows: Sp., soapstone; Sd., sandstone; Lm., limestone; Gr., granite; Py., quartz porphyry (soft in column J; hard in K) ; SI., slate. Column J applies to Rand drills using chisel bits; column K to Leyner- Water drills using X bits in a softer rock. F G H I J K Drilling first 2 ft., mins 20 10 5 10 554 3 i-3 Cranking out and removing bit, mins 2 3 ti 3 l /2 i-3 Cleaning out hole, mins 2 3 3 O Putting in new bit and cranking back, mins I 2 Y2 i 4 54 I] [ /2 Drilling second 2 ft., mins 15 9 6 IO 19 4 ; Y4 Drilling last 2 ft., mins IS 9 8 10 .. Shifting machine on column, hole to hole, mins 5 7 8 3X 5 5 Shifting column, and setting up, mins. 20 to 60 25 25 18 3i 30 Air pressure, Ibs. per sq. in 75 75 80 IOO 75 75 Diameter of drill cylinder 3/4 354 354 3/8 2 a Y-2. " " starting bit 2*4 2^/2 254 2 iH f X " " fiinishing bit 2 \y 2 i*4 1/4 I i' /4 Depth of hole , 8 12 12 6 4.6 S 5 Kind of rock Sp. Sd. L m. Gr. Py. Py. No. of holes drilled at one column set up 9 IO 12 IO 7 8 Length of shift, hrs 10 IO 10 8 8 8 Time lost at blasting, hrs i 1/4 (?) YI i } I " " mucking and timbering, hrs. 4 (?) (?) f 2 f 1 Ft. drilled per shift 60 3i 38 78 ROCK EXCAVATION METHODS AND COST. Results of a Drilling Contest. The following is an ab- stract from an article in the Mining Reporter, July 17, 1902, reprinted in the Leyner drill catalogue. Eleven Water-Ley- ner drills (model 5), seven Ingersoll drills and five Sulli- van drills (all 3-in.) were entered in a drilling contest at Idaho Springs, Col. Each drill was run by an experienced driller and helper, the different contestants bringing their own drills. A face, or breast, was prepared near the New- house Tunnel, where the rock is a "schist of more than average hardness for drill work." Each drill was to put in two Q-ft. holes, one looking up, one down, the angle not exceeding 25 from the horizontal. The finishing bit was \y% ins. diam. The air pressure was no Ibs. I have sum- marized the results of this contest as follows : Nine of the Leyner drills finished the contest, three of the Ingersoll drills and two of the Sullivan drills. Table XX. gives the average results of the drills that finished, as well as the best results of an individual drill of each of the three makes. TABLE XX. Moving Setting Drilling isttO2d Drilling Tearing Total Up. ist Hole. Hole. 2d Hole. Down. Time. H ^ en G 8 en G en en c g en tn en C en CJ en G en s t/3 C/5 3 3 w 3 S C/) 3 ell 4 IO 28 2O I oo 23 40 3 IO 60 2O 4 35 24 15 I 20 34 30 4 15 69 05 3 30 17 30 30 17 50 2 55 42 15 5 05 26 40 I 42 15 3 15 78 15 4 30 27 2O I 25 35 50 4 30 73 35 5 23 O 30 22 o 3 IO 53 40 Make of Drill. Leyner (average)... Ingersoll (average) Sullivan (average). Leyner (best) 5 Ingersoll* (best)... Sullivan (best) In studying this table it is well to note that the first hole the up hole, and the second hole was the down hole in all cases. It will be noticed that the down hole required much longer to drill than the up hole in the cases of the Inger- This drill was disqualified because the second hole was ins. short. THE COST OF MACHINE DRILLING. 79 soil and the Sullivan drills. The Leyner drill, on the con- trary, showed very little difference in speed of drilling either up or down holes ; the reason being, I think, due to the fact that the water (under pressure) that is used with the Ley- ner drift keeps the bottom of the hole clean in all cases (up or down holes), leaving no cushion of sludge for the bit to strike upon. The Ingersoll and the Sullivan drills worked to better advantage in the up, or dry holes, than in the down, or wet holes; because the water used in the wet holes was not forced in through a pipe, but merely thrown into the hole with a tin cup (as is the ordinary method of "tending chuck"), and in a rock that makes sludge rapidly, as many schists do, the sludge accumulates under the bit and cushions its blow. In an up (dry) hole, however, the chips and dust roll out of the hole as fast as formed, so that much better speed is possible in a rock that cuts rapidly, as this particu- lar "schist" evidently does. The Leyner drill is an excel- lent drill in soft rocks, and drills well also in hard rocks, but with a greater air consumption than any other make of drill, as is shown on page 55. Rule for Estimating Feet Drilled per Shift. We are now possessed of sufficient data to enable us to formulate a rule whereby the number of feet drilled per shift, under given conditions, may be predicted. I will not go into the method that I used in deducing the following rule, which is strictly correct, for the method is one of simple arithmetic. The rule is : To find the number of feet of hole drilled per shift divide the total number of working minutes in the shift by the sum of the following quantities: The number of minutes of actual drilling required to drill one foot of hole, plus the average number of minutes required to change bits divided by the length of the feed screw in feet, plus the average number of minutes required to shift the machine from hole to hole divided by the depth of the hole in feet. Suppose, for example, the shift is 10 hrs. long, that is 8o ROCK EXCAVATION METHODS AND COST. 600 mins. ; that it requires 5 mins. to drill i ft. of the rock ; that it requires 4 mins. to change bits and clean hole; that the feed screw is 2 ft. long; that the machine can be shifted from hole to hole in 16 mins. ; and that each hole is 8 ft. deep. Then according to the rule we have: The number of feet of hole per shift is 600 -f- 5 + f + V~> which is equivalent to 600 -f- 9, or 66 2-3 ft. drilled per lo-hr. shift. For those who can use simple algebraic formulas the above rule is much more compactly expressed in the follow- ing formula: S N = N = number of feet drilled per shift. S = length of working time of shift in minutes = 600 for a lo-hr. shift when no time is lost by blasts, break- downs, etc. r = number of minutes of actual drilling required to drill i ft. of the rock. m = number of minutes required to crank up, change drills, pump out hole and crank down. m = 3 to 4 mins. ordinarily. f = length of feed screw, in ft., ranging from ij^ ft- m "baby" drills to 2^ ft. in largest drills, but ordinarily 2 ft. fi = number of minutes required to shift machine from one hole to the next, including the time of chipping and starting the new hole, but not including the time of crank- ing up and cranking down. $ yS = 5 mins. for very rapid shifting of a tripod ma- chine on level rock. 5 JS 12 mins. for moderate speed of shifting a tripod machine on level rock. S j& 20 mins. for very deliberate shifting of tripod ma- chine on level rock. ,5 $ = 30 to 40 mins. for difficult set up of tripod in ir- regular rock surface. THE COST OF MACHINE DRILLING. 81 ^ /gf 25 mins. divided by the number of holes drilled from one column set up (when columns are used) plus 2 mins. D = depth of hole in ft. Even a casual study of the foregoing formula, or rule, must impress the practical man with the importance of the lost time elements in machine drilling; consequently of the value of timing the operations of changing bits and moving machines when the men do not know that they are being timed. Another feature that stands out strikingly is the reduced output of a drill working in a shallow hole. Let the reader solve a few problems, assuming first an average depth of hole of 16 ft. and finally an average depth of only 2 ft. (such as occurs often in the skimming work in road building), and he will never make the blunder of the con- tractor who bid the same price for rock excavation on the 2-ft deepening of the Erie Canal as had been bid for the 36- ft. excavation on the Chicago Canal. The best way of showing the remarkable effect that the depth of hole has upon the number of feet drilled, when the drill is mounted upon a tripod, is to apply the rule given on page 79. If we assume that the shift is 10 hrs. long; that the rate of drilling is I ft. in 5 mins. ; that it takes 4 mins. to change bits and pump out the hole at each change of bits; that the feed screw is 2 ft. long; and that it takes 15 mins. to shift from one hole to the next; by applying the rule we obtain the following results: Depth of hole, ft I 2 3 5 10 15 20 Feet drilled in 10 hrs. 27 41 50 60 70 75 80 When drillers are lazy they may readily consume 8 mins. in changing bits and pumping out the hole each time. With all conditions the same as before, excepting that 8 mins. are consumed in changing bits, we have the following results: Depth of hole, ft 12 3 5 10 15 20 Feet drilled in 10 hrs. 25 36 43 50 57 60 62 82 ROCK EXCAVATION METHODS AND COST. It will be seen that in deep hole drilling 20 per cent, de- creased efficiency results from just a little laziness in chang- ing bits, under the conditions assumed; and in softer rocks the percentage of decreased efficiency is much greater. Where the holes are shallow the time involved in shifting from one hole to the next becomes an important factor. As- suming that the conditions are the same as in the first in- stance, except that 30 mins. are consumed in shifting from one hole to the next; then we have the following results : Depth of hole, ft i 2 3 5 10 15 20 Feet drilled in 10 hrs. 16 27 35 46 60 67 70 In similar manner I might tabulate other results derived by varying the different time elements in drilling; but enough has been given to show the supreme practical im- portance of studying these details, which so many practi- cal men have apparently ignored. I leave it to the reader to apply the rule, or formula, to other cases, for the results of such personal application of the rule will stick in the memory and be of more real value than much reading of tabulated information. Rates of Drilling in Different Rocks. Unfortunately no published record exists showing rates of drilling in different kinds of rock with given air or steam pressures and given sizes of drill bits. Such scattering records as are to be found merely give the feet of hole drilled per shift. Tables XVIII. and XIX. give a fair idea of the speed of actual drilling, and from them together with other data obtained, by observation I have compiled the following table for drill- ing with 3j/6-in. machines using air or steam at 70 Ibs. pres- sure, starting bit about 2^ ins. and finishing bit about i l / 2 ins.: Time to drill I ft. Soft sandstones, limestones, etc 3 mins. Medium, ditto 4 " Hard granites, hard sandstones, etc 5 " Very hard traps, granites, etc 6 to 8 Soft rocks that sludge rapidly 8 to 10 " THE COST OF MACHINE DRILLING. 83 The foregoing data apply only to drilling where no time is lost by the sticking of the bit in the hole, and only with air pressure and bits approximately as above given. The reader should now read again the text on pages 52 to 55, noting especially the falling off in the rate of drilling ac- companying decreased air pressure. He should also study the table on page 54, relating to the effect of size of bit upon speed of drilling, remembering that all the tests there recorded relate only to shallow holes. As holes grow deeper the bit grows smaller, but at the same time the drill steel grows heavier, in consequence of which the last 2 ft. of a deep hole, with a bit only i l / 2 ins. in diam., are ordinarily drilled no faster than the first 2 ft. with a much larger bit. With a powerful drill and a water jet it is quite possible that the last 2 ft. might be drilled faster than the first 2 ft. Note especially that if a water jet is not used, drilling may actually be slower in a soft, friable rock, like shale, than in the toughest trap. This fact is well brought out in Table XIX., column "K," where the drilling of the second 2 ft. of hole consumed 19 mins. ! Yet this material was a soft porphyry that with a water jet was penetrated at the rate of 2 ft. in less than 5 mins., as shown in column "K." While the Leyner- Water drill is an excellent machine for drilling shallow holes in rock that makes sludge rapidly, its excel- lence is due primarily to the use of water under pressure. In drilling granite its speed is no greater than that of the best types of the ordinary percussion rock drill. Reverting to the subject of air or steam pressure as af- fecting the speed of drilling, it is not always easy to gage the pressure at the drill ; but I have found it a simple matter to estimate the pressure with considerable accuracy by noting the number of blows per minute struck by the drill. Using drill-steel of given weight, first test the drill for speed at a point so near the compressor or boiler that little or no loss of pressure can occur in the pipe line. Vary the pres- sure from, say, 80 down to 40 Ibs. in making the test of 84 ROCK EXCAVATION METHODS AND COST. the number of blows struck per minute, and thereafter your pencil and your watch will be a good enough pressure gage. The number of blows can be counted by keeping time with a pencil. The pencil, in the hands of the observer, is made to strike a sheet of paper every time the drill strikes the rock. Then at the end of a definite number of seconds, say 15 sees., the number of marks of the pencil point upon the paper are counted, and the number of blows per minute are computed. Once it has been ascertained how many blows a given size drill strikes per minute when working at full stroke, under varying gage pressures, the only gage needed is the pencil, and a watch ; for the pressure can be roughly ascer- tained by determining the number of blows struck per minute. This I have found to be an exceedingly useful means of ascertaining whether or not too many drills are drawing power from a given pipe line. If a given steam boiler or compressor is designed to supply 15 drills, and if it is afterward loaded up with 20 drills, the pressure at each drill will be reduced, resulting in a very decided falling off in the number of feet of hole put down daily by each drill. Average Footage Drilled per Shift, In subsequent chap- ters many records of actual work are given, but that the inexperienced reader may have a good general conception of what constitutes a day's work under ordinary conditions the following summary may be of benefit : In drilling ver- tical holes, with the drill on a tripod, the holes being from 10 to 20 ft. deep, shift 10 hrs. long, I have found that in the hard "granite" of the Adirondack Mts., N. Y., 48 ft. is a fair lo-hr. day's work. In the granites of Maine and Massa- chusetts 45 to 50 ft. is a day's work. In New York City, where the rock is mica schist, deep holes are drilled at the rate of 60 to 70 ft. per lo-hr. shift by men willing to work, but 40 to 50 is nearer the average of union drillers. In the very hard trap rock of the Hudson River 40 ft. is considered a fair day's work. In the soft red sandstone of northern THE COST OF MACHINE DRILLING. 85 New Jersey 90 ft. are readily drilled per day wherever the rock & not so seamy as to cause lost time by the sticking of the bit; in fact, I have records showing no ft. per lo-hr. shift in this rock. In the hard limestone near Rochester my records show about 70 ft. per lo-hr. shift. In the lime- stone on the Chicago Drainage Canal 70 to 80 ft. was a 10- hr. day's work. In the hard syenite of Douglass Island, in open pit work, and where it is difficult to make set-ups, 36 ft. is now the average per lo-hr. day. In the limestone near Windmill Pt, Ontario, 3^-in. drills average 75 ft. a day (holes 18 ft. deep) ; 2^-in. drills, 60 ft. a day, and "baby" drills, 37 ft. a day. The foregoing examples all apply to comparatively deep vertical holes, in open excavation. In tunnel work there is no reason why a drill should not do about the same work per shift, were there no delays in timbering, mucking, wait- ing for gases to clear, etc. Such delays, however, often re- duce the drill footage very much, as will be seen in subse- quent chapters. Cost of Sharpening Bits. In the South African gold mines each machine averages 20 drills per shift, and taking the average weight at 15 Ibs. per drill, it is evident that 600 Ibs. of drills must be carried to and from the shop for each machine per shift. Where 30 drills are at work this means the transportation of 9 tons of drills each shift an item in itself worthy of consideration. One blacksmith (with a helper) will sharpen about 140 bits a day, and under ordinary conditions will keep 5 to 7 drills supplied with sharp bits. In average rock a bit must be sharpened for every 2 ft. of hole ; in very soft rock a bit for every 4 ft., and in very hard rock a bit for every 1^/2 ft. of hole. Sharpening 140 bits by hand costs $3 for blacksmith's wages, $2 for helper and 60 cts. for charcoal, or 4 cts. per bit. Mr. Edward D. Self, Manager and Engineer San Carlos 86 ROCK EXCAVATION METHODS AND COST. Copper Co., San Jose, Mexico, writes me that 185,828 hand drills were sharpened in drilling about 65,000 ft. of hole, at a cost of 2 cts. per bit (Mexican currency) ; and that 10,- ooo machine drill bits were sharpened by hand at a cost of 3 cts. each (Mexican currency). For sharpening large numbers of bits daily, drill sharpen- ing machines are much cheaper than hand sharpening, as shown on page 30. Cost of Drill Repairs. Mr. Thomas Dennis, agent of the Adventure Consolidated Copper Co., Hancock, Mich., has kindly furnished the following data of the average monthly cost of keeping a drill in repair: Supplies for repairs $1.31 Machinist labor 8.45 Blacksmith labor . 1.60 Total repair charge per month $11-36 The number of drills in the shop at any one time is about 15 per cent, of the total number. This low cost is based upon work where a large number of drills are used and well handled by the users. I am indebted to Mr. Josiah Bond, mining engineer, for i4^ the statement that the cost of repairs averages 50 cts. per -^ drill per shift in mines where a few drills are operated awl renewal parts purchased from the manufacturers. In open cut work my experience is that 75 cts. per drill per shift is a fair allowance for renewals and repairs. In the gold mines of South Africa, where each drill works two shifts per day, the cost of drill repairs is $300 per drill per year; while the first cost of a 3^4-in. drill with bar is $185, according to a recent report of the Government Mine Inspector. Plant Rental. This term is a convenient one to use in- stead of "interest and depreciation," moreover "plant rental" is a term that clearly excludes the cost of current repairs. It is exceedingly difficult to nanie any definite percentage to be THE COST OF MACHINE DRILLING. 87 allowed for rental of a drilling plant, because the term of years during which the plant will be operated by the pur- chaser is usually a matter of guess work. Little or nothing can be borrowed from banks upon a drilling plant as the only collateral ; hence the owner of a plant is not justified in charging only the legal rate of interest for rental even if the plant were to have an everlasting life. The owner should charge for interest on the plant all that he could earn in the way of profits if he had the plant money invested otherwise in his business. The life of a plant is only a few years at best, since improvements in machinery are con- stantly taking place. Moreover "dull times" put scores of plants upon the idle list for indefinite periods of time. In view of these facts it is good business policy to charge the whole cost of a drilling plant up against the contract job for which it is purchased, if the job is a large one. For small mines and small jobs generally, it is wise to charge up 20 to 40 per cent, of the first cost of the plant for annual "rental" or "sinking fund." Divide this annual "rental" by the total number of shifts that will probably be worked dur- ing the year, to arrive at a probable rental cost per shift; and in estimating the probable working days in the year make liberal allowance for strikes, bad weather and sundry delays. In the estimates of cost that follow I purposely omit an allowance for "plant rental," because each case must be treated as a problem in itself ; nevertheless, "plant rental" is often a very important item and one that is not infre- quently forgotten entirely in making estimates of cost. Cost of Installing a Compressor Plant. The following is an itemized account of the cost of installing a small com- pressor plant. The compressor was a Rand, Class C, 24 x 3O-in., that cost $4,000. The boiler was a second-hand 150 H.-P. locomotive boiler that cost $1,000. This plant was capable of furnishing 1,300 cu. ft. of free air per min. at 80 88 ROCK EXCAVATION METHODS AND COST. Ibs. pressure, or enough to run 10 or 12 drills. Cost of in- stalling boiler: 22 days laborers, at $1.50 $33 23 " engineers, at $3 69 13 mechanics, at $4 52. 13 " " help, at $2 26 i " bricklayer, at $4 4 Total $184 Cost of installing compressor : 120 days laborers, at $1.50 $180 4 " engineers, at $3 12 22 " mechanics, at $4 88 80 " " help, at $2 1 60 50 " carpenters, at $3 150 3 " bricklayers, at $4 12 6 " teams, at $4 24 8 " foremen, at $3 24 Total $650 Cost of materials: I5M lumber for housing compressor, at $25. .$375 1,400 sq. ft. tar paper (i layer) 21 32 cu. yds. concrete, at $4 128 5M brick, at $7 35 6 bbls. cement, at $2 12 Sand I Total $572 Cost of a Large Compressor Plant. The following is the estimated cost of a compressed air plant for a western mine, the compressor being designed to carry 20 drills (3^-in. size) : 4 high pressure boilers (66-in. x 16 ft) $6,000 Housing and installing boilers 2,000 THE COST OF MACHINE DRILLING. 89 Duplex compound air compressor 16,000 Housing and installing compressor 2,000 Pipe, 1,000 ft. of 6-in., and 1,500 ft. of I in.. 1,200 Machine shop and tools 800 Total $28,000 It is usually safe to estimate on a basis of $130 to $150 per drill for the cost of a large and efficient compressor plant and pipe line, to which must be added the cost of the drill itself, which is about $250 for a 3^-in. drill mounted. Cost of Operating Drills. When operating a single (3/4" m -) drill supplied by steam from a small portable boiler, I find the cost is usually as follows for a lo-hr. shift : i drill runner $3*oo i drill helper 1.75 I fireman 2.00 660 Ibs. of coal (0.3 ton at $3) 90 Water if hauled, say 75 Hauling and sharpening 30 bits (incl. new steel) at 4 cts 1.20 Repairs to drill and hose renewals 75 Total per 10 hrs $10.35 The foregoing is merely an example, based, however, upon several different jobs ; but in each case the accessibility of a blacksmith, the nearness to water, the price of coal de- livered at the boiler, etc., must be determined before an ac- curate estimate can be made. If 4 drills, for example, are to be operated from the same boiler, the fuel bill will be somewhat reduced even if the pipes are not covered with asbestos, and of course the wages of the fireman will be dis- tributed over 4 drills. It will then pay to have a black- smith at hand. If 10 or more drills are run by steam from a central boiler, and if the main pipes are lagged, the fuel should not much exceed 300 Ibs. per drill per lo-hr. shift. By the rules previously given a fairly close estimate can be QO" ROCK EXCAVATION METHODS AND COST. made of the number of feet of hole that each drill should average. If 60 ft., for example, is to be a fair day's work in limestone or sandstone, we have $10.35 -^ 60 = 17 cts. per ft. as the cost, exclusive of superintendence, plant installa- tion and plant rental. If a central compressor or steam plant supplies power for, say, 15 drills, we may estimate the cost of operating each drill as follows : i drill runner $3.00 i drill helper 1.75 1-15 fireman at $2.25 15 1-15 compressor man at $3 20 300 Ibs. coal (water nominal) at $3 ton 45 Sharpening bits, 30 at 3 cts 90 Repairs to drill, hose, etc 75 Total for 60 ft. of hole at 12 cts $7.20 If the cost of each drill and 1-15 part of the compressor plant is $350, and 30 per cent, of this is assumed as a fair allowance for annual plant rental, we have $105 to charge up against each drill for "rental," or about 50 cts. per shift if 200 shifts are worked each year, or about i ct. per ft. of hole drilled. Cost of Drilling Blast Holes with a Well Driller. In En- gineering News I first described the use of well drillers on the Pennsylvania Railroad work for drilling blasting holes. The well drillers used were the ordinary type of portable driller, consisting of a wagon on which is mounted a 4 to 8 H.-P. engine that drives a walking beam; the walking beam raises and lowers a rope, to which is fastened the churn bit and rods that form the "business end" of the driller. A 5^-in. bit was used in this work, and even witn this large bit each drill averaged three 20- ft. holes, or 60 ft., drilled in shale per lo-hr. shift. In limestone, however, and in hard sandstone not more than 10 ft. of hole were drilled per shift. In describing the use of the well driller for this purpose I suggested that if the bits were reduced to about THE COST OF MACHINE DRILLING. 9^^kiP8Nl! 3 ins. in diam., and if the drill rods were suitably weighted, much better progress would be made in hard rock. Shortly afterward the Cyclone Drilling Machine Co., of Orrville, Ohio, put upon the market a driller especially designed for contractors doing railroad work. The Cyclone driller has a 5 H.-P. engine, uses a 3~in. bit, has drill rods that screw together and a suitable weight to give power to the blow, and the whole outfit on trucks weighs only 5,000 Ibs. Fig. 6 shows one of these drillers at work on the Wabash Rail- Fig. 6. road. For this type of driller I predict an increasingly large field, for the following reasons : ( i ) A drill will not stick in the hole, because of the powerful direct pull of the rope that operates the drill rods; (2) there is no limit to the depth of the hole, and the deeper it is (up to any limits possible in blasting) the better the drill works, due to the increased weight of the rods; (3) this type of drill con- sumes less fuel than the ordinary steam drill ; (4) the weight of bits to be carried back and forth from blacksmith shop 92 ROCK EXCAVATION METHODS AND COST. is much less than for the ordinary machine drills; (5) the driller will drill through the earth overlying the rock, so that no stripping is necessary. Mr. W. M. Douglass, of Douglass Bros., contractors, was kind enough to keep records for me showing the cost of operating one of these cyclone drillers compared with a Rand drill. The following are the data: The holes were drilled with bits to give 3 ins. diam. at the bottom of the hole. Holes were 24 ft. deep in solid brown sandstone in eastern Ohio. In 14 days, of 10 hrs. each, the driller put down 692 ft., or practically 50 ft. per day. The daily cost of operating was as follows : Drill runner $3.00 Drill helper and fireman 2.00 Pumping water 60 6 bu. (480 Ibs.) coal at 10 cts 60 Total for 50 ft. of hole $6.20 This gives a cost of 12^2 cts. per ft. of hole, not includ- ing interest and depreciation and bit sharpening. The best day's work in the brown sandstone, using all the weights, was 53 ft., but in blue sandstone, which was softer, 60 ft. were drilled per day using light weights. In the same brown sandstone cut an 8-day test was made with a 3/4~in. Rand drill for comparison. The holes were 20 ft. deep, 1^4 m s. diam. at the bottom (as against 3 ins. with the well driller), and 28 holes were drilled in the 8 days, making 70 ft. the average day's work. A 10 H.-P. boiler furnished steam. The daily cost of operating the Rand drill was : Drill runner $3-OO Drill helper 1.50 Fireman 2.00 Water 75 10 bu. (800 Ibs.) coal at 10 cts i.oo Total for 70 ft. of hole $8.25 THE COST OF MACHINE DRILLING. 93 This was equivalent to n.8 cts. per ft. of hole, not in eluding interest and depreciation and drill sharpening. It should be observed that the well driller holes were deeper (and they could have been still deeper without in- creasing the cost per foot) as well as larger in diameter than the Rand drill holes. The greater diameter saved a considerable amount of dynamite in springing the holes, since each well driller hole was sprung three times, as com- pared with four or five times for the Rand drill holes, in order to make a chamber large enough to hold the black powder. Mr. Douglass has made some interesting tests on the use of black powder and dynamite in alternate rows of holes, for which see page 149. I would suggest a further improvement in this type of driller, namely, the use of a gasoline engine instead of a steam engine. Such a change would do away with the cost of water for the boiler. It would also make it unnecessary to have a fireman. Cost of Drilling with Electric Drills. Upon this subject there is practicality nothing in print. I am indebted to Mr. J. B. Hobson, Manager Caribou Hydraulic Co., Bullion, B. C, for the following cost data: Four Gardner Electric Drill Co.'s No. 15 drills, with 2 H.-P. motors, and one "B" drill with a i^ H.-P. motor, have been used for two years by Mr. Hobson with excellent results. Each of the larger drills has averaged 13 holes, 8 ft. deep, in firm augite diorite and porphyrite, per lo-hr. shift. The starting bit is 2.y 2 ins. and the finishing bit i l / 2 ins. in diameter. The cost, per 10- hr. shift, of operating three drills has been as follows : i cord of wood $2.25 I electrical engineer 4.00 3 drillers, at $4 12.00 3 helpers, at $2 6.00 i blacksmith 4.00 i blacksmith's helper 2.00 94 ROCK EXCAVATION METHODS AND COST. 3 bu. charcoal $0.75 Oil 55 Total for 3 drills, 312 ft. drilled $31-55 The cost of drilling, including sharpening, but excluding interest and depreciation, was 10 cts. per foot of hole. See page 20 for cost of hand drilling in the same rock. In Trans. Am. Inst. Min. Eng., 1903, Mr. Frank E. Shep- ard describes the box electric drill which is manufactured by the Denver Engineering Works, Denver, Colo. The drill steel is not churned but is struck by the piston, resembling the Leyner drill in this respect. Water is forced down through a pipe which slips over the drill steel, and the sludge is washed out of the hole. In drilling a block of granite from Platte Canyon, Colo., an electric current of n am- peres at no volts was used, which is equivalent to 1.62 H. P. A hole 2)4 ins. in diameter was drilled, the first 16 ins. being drilled in 7 mins. ; then I min. was consumed in changing bits. The next 14 ins. were drilled in 5 mins., and i min. more was consumed in changing bits. The last 3^2 ins. were drilled in 4 min. The rate for the full 33)^ ins. was 2.23 ins. per minute. In tunnel work in Boulder County, Colo., one machine drilled 12)^ ft. of holes (number of holes not given), 2)4 ms - diam., in hard granite in 2 hrs. Three tunnel holes, each 5 ft. deep, were drilled in 2)4 hrs. In shaft sinking at the Ophir Mine, Anaconda, Colo., five 4-ft. holes were drilled in 3)^ hrs. In the tunnel of Imogen Basin Gold Mines Co., Ouray, Colo., four holes 5 ft. deep, were drilled in 3 hrs. in soft rock with mud slips running through the seams. CHAPTER VI. COST OF DIAMOND DRILLING. For determining the nature of bridge foundations the char- acter of proposed canal or railway excavations and for pros- pecting for mineral deposits, the diamond drill is an invalu- able machine. The bit of a diamond drill consists of a num- ber of diamonds mounted on the end of a hollow tube. This bit is rotated by hand, steam, air or electric power, while at the same time water is pumped down the hollow drill rods and passes up outside of the rods, carrying away the rock dust made by the grinding of the diamonds against the rock. The bit cuts an annular channel, leaving a core of rock inside the core barrel. When the drill has penetrated the rock a distance of 6 to 10 ft., the drill rods are raised and the act of raising them breaks off the rock core, which is brought to the surface in the core barrel and kept for examination. The diamonds are preferably black diamonds, known in the trade as "carbons"; but where the rock is soft, white diamonds, known as "borts," may be used. Sometimes both kinds are used in one bit. A bit usually has 6 to 8 carbons weighing I to I ^2 carats each. Small stones are not econom- ical because after a carbon has been worn down so that it weighs less than about ^2 carat it cannot be reset. In se- lecting carbons reject those showing a cokey structure, also those having thin, sharp edges. Carbons having straight edges with sides forming an obtuse angle of 95 to 140 are most durable. The cleavage should be tested with a pair of hand pincers. Old stones that have been used are to be pre- ferred since a poor stone will break in use, and no test is so satisfactory as the test of usage. The carbons selected for a bit should be quite uniform in size. 95 96 ROCK EXCAVATION METHODS AND COST. When diamond drilling was first introduced into this coun- try it was predicted that it would be used exclusively for drilling blast holes, and in fact diamond drills were used on the Sutro tunnel for a while, and in sinking one or two shafts by the "long hole" method, which involved drilling holes several hundred feet deep, filling them with sand, then removing the sand for about 8 ft., charging with powder, firing, and so on. The development of machine drills using steel bits and the steady rise in price of carbons have to- gether shown these early predictions to have been fathered by hope rather than by reason. The sizes of holes and cores are as follows : Hole, diam. in ins.... i^ i^4 2 2^ 3 9/16 Core, " " " .... 15/16 13/16 17/16 2 2ft Price of Diamonds. In 1873 the price of carbons per carat was $8 to $12, whereas now the price is about $50. I am in- debted to the Standard Diamond Drill Co., of Chicago, and to the Yawger-Lexow Co., of New York, for the follow- ing statements as to the average cost of carbons per carat from 1895 to 1903 : i95. 1896. 1897. 1898. 1899. 1900. 1901. 1902. $36 $50 $60 $55 $50 $45 $50 $18.50 $28 $35-50 $35-50 $36 $51.50 $48.50 $47 It will be noted that these firms do not agree very closely as to prices prior to the year 1900. The American Diamond Rock Drill Co., of New York, quoted $52 per carat for best selected carbons and $16 per carat for best selected borts in November, 1902. There is no import duty on carbons in the United States, Canada 01 Mexico. Water Required. In boring a 2-in. hole where the prog- ress is about 10 ft. per lo-hr. shift, from 100 to 125 gals, of water are required to wash out the sludge formed in drill- ing, provided the water is used but once. In cases where the water is expensive it is customary to collect the return water in a settling tank and use it over and over; and, unless a large amount of water escapes through crevices, 30 or 40 COST OF DIAMOND DRILLING. 97 gals, per shift will be consumed by evaporation and leakage. Price of Diamond Drills. A hand power drill that can be used to bore a i^-in. hole (giving a i5-i6-in. core) up to a depth of 350 ft. ; or a 2^-in. hole (giving" a 2-in. core) up to a depth of 250 ft., will cost approximately $850 f. o. b. New York or Chicago. This includes 300 ft. of pipe, 6 car- ats of carbons, all tools, etc., necessary. The machine alone weighs 330 Ibs., and can be divided into packages weighing 40 Ibs. ; but the whole outfit packed for shipment weighs 2,800 Ibs. If it is desired to run this drill by horse power, $60 additional will purchase the horse power equipment. A hand power plant capable of drilling 50 per cent, deeper than the above costs about $1,400. A steam power plant that can be used to bore a ij^-in. hole 800 ft. deep, or a 2^-in. hole (2-in. core) 500 ft. deep, costs about $2,400, including the 8 H. P. boiler on wheels ; the drill itself costing $1,100, the boiler $400; I set of car- bons (9 carats), $450, and the balance for sundries. The drill itself weighs 600 Ibs., but the full outfit packed for ship- ping weighs 10,000 Ibs. A steam power plant that can be used to bore a I ^-in. hole 1,500 feet, or a 2^-in. hole 1,000 feet, can be purchased for $4,600; of which $2,400 is for the drill, $500 for the 15 H. P. boiler on wheels, $600 for 12 carats of carbons and the bal- ance for rods and sundries. This outfit weighs 20,000 Ibs. Cost in Virginia. There is a great deal to be found in print relative to the cost of diamond drilling, but unfortu- nately the records as published are in such form as to be oi far less value than they should be. By this I mean that any record of any kind of drilling to be of great value should give : ( i ) The rate of penetrating a given kind of rock when the drill is actually cutting; (2) the speed, power and weight of the machine; (3) the time lost in raising the drill to change bits, remove cores, or the like ; (4) the time required to shift from one hole to the next; (5) the average time lost in repairs, breakdowns, etc. ; (6) the diameter and depth of 98 ROCK EXCAVATION METHODS AND COST. hole; (7) the time consumed in driving and pulling casing. No record in print contains all these factors. Strangely enough, one of the earliest printed accounts contains more of these factors than any subsequent record. I refer to an ad- mirable paper by O. J. Heinrich, in Trans. Am. Inst. Min., Eng., 1874, from which I have abstracted the following : The diamond drill crew consisted of three men, two to run the drill and one to help raise the drill rods, beside a fore- man. The shift was 12 hrs. long, and the following was the cost of operating a shift : Foreman, or boring master $2.50 Mechanic, or engineer 2.00 Assistant 1.50 Laborer . i.oo Total labor $7.00 The coal consumed was 10 Ibs. per H. P. per hr. For holes up to 1,000 ft. deep an 8 H. P. engine was used, the drill rods weighing 4,500 Ibs.; but up to a 1,500- ft. hole a 12 H. P. engine was used, with rods weighing 7,000 Ibs. The drill had a 2-in. bit, on which were mounted never less than 12 carbons, better 16. The drill rods were raised after every 10 ft. of drilling. The drilling was done in Chesterfield county, Va., prospecting for coal, in 1873. The cost of op- erating per shift is given as follows : Labor $6.50 1/3 ton coal at $3 i.oo Oil 0.50 Diamonds and repairs n.oo Interest and deprec 1.92 Total per day . . . $20.92 The price of carbons was $10 per kt. Rates of wages were also much lower then, and it should be noted that the allow- ance for interest and depreciation is too low for a plant cost- ing $7,200, as it is stated this 8 H. P. plant cost. COST OF DIAMOND DRILLING. 99 Depth of hole in earth and rock 419 850 1,142 Depth bored in rock 396 826 1,118 No. of 12-hr, shifts actually boring 13.88 44.41 59.29 " " " " raising rods 15.87 59-34 Il6 -46 incidentals 3.25 15.25 68.25 total 33.00 1 19.00 224.00 Ft. progress per hr. while boring 2.37 1.55 1.57* " " average 0.998 0.578 0.308 Cost of labor, per ft $0.36 $0.59 $1.02 Cost of fuel ($3 ton) per ft $0.53 $0.14 $0.17 Cost of all other items, incl. materials and blacksmithing $1.29 $1.43 $2.05 Interest $0.16 $0.27 $0.38 Total cost per ft $1.86 $2.43 $3.62 From the data given by Mr. Heinrich I have prepared the following formulas to be used in computing the number of hours required to drill a hole of given depth. Let T = Total number of minutes required to bore the hole, n = total depth of hole in feet. 1 = length of each coupling rod = 10 ft. in this case. t = the number of minutes required to bore i ft. of the hole. In the formation given by Heinrich t = 19 mins. per ft. of hole up to a depth of 300 ft., to which add 5 mins. per ft. for each 100 ft. of in- creased depth. r = time in minutes required to raise and lower the rods, including 2 mins. to uncouple and couple up. r = 7 mins. for hole up to 300 ft. plus 1-3 min. for each additional 100 ft. s = number of lengths of coupling rod. The time consumed in actual boring in feet is obviously nt. The time consumed in raising and lowering the drill rods is the sum of an arithmetical series in which s = the number of terms and r = the common difference ; hence the sum is l / 2 s (2r + [s i] )r, which reduces to - The [oo ROCK EXCAVATION METHODS AND COST. total time is therefore : 2 12 If 1=10 T = nt + n(l + n) r 200 ~ n 3 r T = nt + , nearly. 200 For holes of the following depths we have : ft. ft. ft. n = 400 800 1,200 t (minutes) r= 24 44 64 r (minutes) =71/3 8 2/3 10 T (minutes) = 14,300 63,000 148,800 T (hours) = 240 1,050 2,480 On Heinrich's work about 10 per cent, more time than the above was required to cover losses from delays arising from various causes. The point that is strikingly brought out by Heinrich's records is the rapid falling off in the rate of speed of drilling each foot of hole with increased depth. The cause is obvious, however, for the longer the line of drill rods the greater the friction of the rods upon the sides of the drill hole, and consequently the slower their revolution with an engine of limited horse power. The increased weight of the rods with increased depth also reduces the rate of speed with which they are hoisted by the engine ; and this is a very im- portant factor in adding to the labor and fuel cost of drilling deep holes. Heinrich's estimates of the time required to drill holes, including all 10 per cent, allowance for delays, are as follows : COST OF DIAMOND DRILLING. 101 400- ft hole, 288 hours 800 " " 960 " 1,200 " " 2,616 " It will be observed that these times check fairly well with the times obtained by applying the formula that I have given ; but it should be added that the constants in the for- mula need further verification by other observers. The ma- terial penetrated in the 800- ft. hole was : Hard silicious sandstone 210 ft. Medium " " 362 " Argillaceous sandstone and slate. 237 " Limestone 18 " Total 827 " Heinrich's estimates of time, and my own formula based thereon, assume a uniform sandstone throughout in the three holes. Had the rock been uniform throughout, the cost would have been : 400- ft. hole, at $1.26, $504 8oo-ft. " " 2.10, i, 680 i,200-ft. " " 4.00, 4,800 Cost in Lehigh Valley. Mr. L. A. Riley is authority for the following, as given in Trans. Am. Inst. Min. Eng., 1876: Two machines belonging to the Lehigh Valley Coal Co. were used. A No. 2 drill with 16 H. P. boiler and 1,000 ft. of 2-in. rod cost $3,900, which with diamonds, etc., came to $5,000; the weight being 3,500 Ibs. Carbons cost $9 per carat, and borts cost $11. Five diamonds weighing 18 carats were used per bit, drilling a 2-in. hole and bringing up a i^2-in. core. There were 24 holes, aggregating 9,902 ft., the deepest being 900 ft. The average rate of drilling these holes was 19 ft. per day per machine, at an average cost of $2.22 per ft. The rock was a very hard sandstone and conglomerate. The force on each drill was one fore- 102 ROCK EXCAVATION METHODS AND COST. man, one engineer and one fireman. The average cost per ft. of hole was : Labor $.1.15 Diamonds 66 Supplies and repairs 41 Total $2.22 The cost of the 900- ft. hole (the deepest) was $1.95 per ft., which indicates that with a powerful (16 H. P.) engine there is no such great increase in cost per ft. with increased depth as Heinrich found with an 8 H. P. engine. The 16- H. P. plant used by Riley was capable of drilling a 2,ooo-ft. hole. Note especially that both Riley and Heinrich paid less than $10 a carat for carbons and that Riley does not say what proportion of carbons to borts were used. Cost on Croton Aqueduct. Mr. J. P. Carson, in Trans. Am. Inst. Min. Eng., 1890, gives the following: Fourteen holes, total 2,084 ft., were drilled in the year 1895. Actual days worked 189 days Moving drill 15 Idle 18 Holidays and Sundays 39 Total 261 Daily Progress Cost Feet. per ft. 347 ft. Hard gneiss n to 12 $3-97 814 ft. Decomposed gneiss 23.1 to 28 1.15 572 ft. Clay, gravel and boulders 6.7 to 9 4.07 351 ft. Clay and gravel 25 2,084 ft. Average 10.2 2.91 Crew, i foreman @ $125 mo.; I assistant foreman @ $70 ; 4 men @ $65. Wages, 8.1 mos $3>7 8 5 COST OF DIAMOND DRILLING. 103 Team moving $80 66.7 tons coal ( 189 days) 360 Supplies, Diamond Drill Co 472 Foundry 291 Lumber, rope, etc 53 Interest on $6,000 plant @ 12 per cent. 8.1 mos.. . 486 Renewing diamonds 250 Diamond bit lost 300 Total, 204 days $6,077 Aver, per day $29.79 Aver, per ft $ 2.91 Note that the interest on the plant is altogether too low. Cost of Hand Diamond Drilling in Arizona. Eng. News, Jan. 18, 1900, p. 34, Mr. J. B. Lippincott gives data on dia- mond drilling at the Gila River Dam site, Arizona. The ma- chinery was in two distinct parts, (i) the hand pile driver for sinking casing pipe to bed rock; (2) the diamond drill. The hammer, made by the Pierce Well Co., 120 Liberty street, New York, is in sections, so that its weight can be varied up to 190 pounds ; it is raised by a hand winch, and tripped by nippers; maximum drop 11^2 ft. A tool-steel head is screwed into the top of the pipe and receives the blow. The pipe is 3^2, 2^ and 2 in., extra heavy, screw pipe, 5 ft. sections, with extra heavy couplings which have beveled edges. When the casing has reached bed rock, the sand inside is removed by using a chopping bit and a water jet. The bit is screwed to a ^-in. pipe through which water is pumped by a hand pump, the water passing out through holes in the bit, thus bringing the sand to the top of the cas- ing. In this manner a casing pipe 130 ft. deep can be cleaned of sand and gravel. If a boulder is struck, after the diamond drill has penetrated it, four or five sticks of dynamite are lowered and discharged, shattering the boul- der so that the casing can be driven down. The diamond drill was made by the American Diamond Rock Drill Co., New York City. One inch core bits were 104 ROCK EXCAVATION METHODS AND COST. usually employed. The drill was operated by hand power, six men being employed on this work as well as on driving the casing. The drill will penetrate 200 ft. into rock, and will make 6 to 8 ft. per day in hard rock and 10 to 15 ft. per day in soft rock; The plant complete costs $1,000, including two diamond bits worth $200 each, set with six I -carat dia- monds each. Two machines were used. The pipe cost $600 and freight, $100. Cost of operation per month, foreman $150. 6 laborers at $1.50 for 28 days, 234. i cook 45. $429 240 rations at 60 cts 144 Total labor for one month $573 Total repairs, pipe and lumber for one party for 10 months 500 Team, feed, etc 350 Moving 670 Sundry incidentals 430 Supervision 350 Total supplies, etc., for 10 mos $2,300 Total labor, 10 mos 5>73 Total $8,030 Total number of feet sunk 3> 2 54 Cost per ft $2.46 52 holes, cost per hole $154.42 Total Depths Penetrated. Earth,ft. Rock, ft. Total,ft. The Buttes 1,621.2 196.0 1,817.2 Queen Creek 357.8 55.6 413.4 Riverside . ,>. . . 729.8 40.2 770.0 Dykes 80.0 o.o 80.0 San Carlos 143.2 30.4 173.6 2,932.0 322.2 3> 2 54-2 COST OF DIAMOND DRILLING. 105 A month's time of one party was lost due to continual breaking of the casing pipe under the hammer. Note that 90 per cent, of the drilling did not involve the use of dia- monds but consisted in driving through the earth covering overlying the rock. This is characteristic, however, of test- ing dam sites. References. As stated in the fore part of this chapter, diamond drilling data are to be found in abundance. Among the most vauable of articles relating to the cost of diamond drilling are the following : In Engineering News, Apr. 2, 1903, data of drilling in South Africa ; in Engineer- ing News, July 23, 1903, is an excellent account of the cost of drilling test holes (100 ft. deep), along the line of a pro- posed canal in New York State ; in the Transactions of the Institution of Mining and Metallurgy, Apr. 23, 1903, Mr. J. N. Justice gives valuable cost data of drilling deep holes (460 to 1,627 ft.), on the coast of Africa ; in Mines and Min- erals there are several excellent articles by Lane, in the last half of the year 1899; in Engineering Magazine, March, 1896, there is a good article by Channing, an engineer who has had much experience in Michigan ; in the catalogues of American manufacturers of diamond drills much valuable information is given. CHAPTER VII. EXPLOSIVES. The Action of Gases from an Explosion. The explosives in common use in America are few in number: Black powder, several varieties of dynamite, Judson powder and Joveite. In every case an explosion is a chemical action that takes place between the elements of the explosive, liberating suddenly a great volume of gas at a high temperature. Ordi- nary air moving at a velocity of 100 miles an hour strikes objects with great disruptive force, yet a hurricane is mild indeed compared with the feeblest of explosives. Black powder, which is the weakest of the common explosives, is exploded whenever it reaches a temperature of 518 F. If its grains are small, as in rifle powder, each grain quickly burns up, yielding the full volume of gas in a short time. If its grains are larger the rapidity with which each grain is converted into gas is slower. Dynamite and Jovite are exploded not by mere heating, as with black powder, but by a hard shock delivered usually by a cap, or "detonator," or "exploder." The more severe the blow delivered by the exploding of the cap, the more quickly does the chemical action take place. In any case this chemical action is far more rapid than it is in black powder, but the greater the shock the more rapid is the lib- eration of the gases. Hence it is poor economy to use feeble caps where it is desired to tear rock into small pieces. If a quantity of dynamite is exploded under water it has 1 06 EXPLOSIVES. to? been found by actual experiment that the gases fly in all di- rections with equal velocity and in equal quantity. * Hence it is a mistake to suppose that high power explosives act only downward. They exert a pressure equal in all di- rections at the instant of explosion. Let it be kept clearly in mind that an explosion is merely the sudden creation of a great volume of gas seeking to escape with enormous ve- locity, and much of the mystery about the effects of an ex- plosion vanishes. Consider the gas as so many minute and invisible rubber balls, each possessed of weight and flying with frightful velocity, and it becomes comparatively easy to explain most of the phenomena attending an explosion. The gas as it leaves the explosive flies in all directions, but the instant it encounters an object it either rebounds from that object, or tears its way through the object, or hurls the object to one side. If the object is very heavy and sub- stantial, the particles of gas rebound from it, like rubber balls rebounding from the side of a house. Hence it often happens that the gases from dynamite, when exploded in an open place, travel along a certain path like a hurricane. They do so because they have rebounded from some im- movable objects, and have been, as it were, reflected like rays of light from a mirror. * Eng. News. March 12, 1892, "D. E. O." in a letter states that in 1878, near Sawyer City, Pa., a wagon containing 60 qts. of nitroglycerine overturned, and the nitroglycerine exploded. The writer gives a sketch to show the wedge path of the exploded gases. The writer says: "Take two 2 or 3-oz. bottles and fill with nitroglycerine, fit one with an exploder and let the exploder rest on the bottom of the bottle; place this on a sheet of boiler iron and explode. It will be found to have barely brightened the plate. Now fit No. 2 with an exploder fastened in the neck of the bottle and explode, and it will be found to have blown a hole completely through the plate." The writer contends that this experiment proves that dynamite does not exert an equal pressure in all direc- tions when exploded. The editor of Engineering- News cites the extensive ring- gage tests conducted by Gen. Henry L. Abbot "with nitroglycerine under water." A s-ft. ring carried six pressure gages, and to record pressure of dyna- mite fired at the center of the ring. The charge was placed in a tin can, placed vertically, and was fired at the top by a detonator. The ring was suspended in a vertical plane from buoys. At a depth of 35 ft., the two upper gages regis- tered 20,366 and 17,576 Ibs. per sq. in., and the two lower 15,479 and 14,671 Ibs. In a later experiment, 16,000 and 21,000 Ibs. were recorded in the upper gages; and 15,000 and 16,000 Ibs. in the lower. io8 ROCK EXCAVATION METHODS AND COST. When dynamite is exploded in a hole drilled in solid rock, the gases are created so suddenly and move with such enor- mous velocity that when they strike the sides of the drill hole, the rock is struck as if with a mighty sledge; and, if the dynamite is in sufficient quantity, the blow tears off a portion of the rock. This occurs even when the hole above the dynamite is not plugged up with earth or stone chips; but if the hole is left open obviously much of the gas es- capes and renders the blow less effective in consequence. Black powder, on the other hand, explodes more slowly so that if the hole is left open a greater proportion of the gas escapes before the last grain of powder has burned up. Hence it is absolutely essential to use great precaution in plugging the hole where black powder is to be fired. In the early days of dynamite it was commonly stated that no "tamping" above the dynamite was required, and to this day there are text books in use containing this mis- leading statement. Tamping may not be "required," in the sense that it is absolutely essential; but it is certainly required where the full value of the dynamite is to be utilized in breaking rock, instead of disturbing the air, for there is no profit in shaking up the atmosphere. Due to the fact that powder gases are elastic, and rebound from any solid surface, it follows that the shape of the drill hole has a decided effect upon the lines along which rock breaks. When holes are drilled by hand they tend to be- come three cornered; and as a result, if black powder is used, the particles of gas bouncing back and forth, as fast as they are liberated, batter the three faces of the triangle and tend to split the rock in three directions, the cracks in the rock starting at the corners, or angles of the triangle. Black Powder. The highest grade of black powder con- sists of 75 per cent, saltpeter (KNO 3 ), 15 per cent, charcoal and 10 per cent, sulphur. The charcoal for rifle powder (sporting powder) is commonly made from dogwood, but willow and alder charcoal are commonly used for blasting EXPLOSIVES. 109 powder. In some inferior powders lampblack is substituted for part of the charcoal. The saltpeter (or nitre) is often replaced by sodium nitrate (Na NO 3 ), which deteriorates in time by absorbing moisture from the air. Therefore when blasting powder containing sodium nitrate ("soda powder") is used, great care must be taken to keep it in a dry atmosphere, and it should be used very soon after it is received from the factory. Powder is sold by the "keg" of 25 Ibs., at about $1.25 a keg for soda powder and $2.10 for nitre powder. The specific gravity of individual grains of black powder ranges from 1.5 to 1.85; the average weight of loose powder, slightly shaken, being 62^ Ibs. per cu. ft., or i Ib. occupies 28 cu. ins. Properties of Good Black Powder. A good blasting powder has a uniform dark gray or slaty color. A dead black, or a bluish color, indicates either too much charcoal or the presence of moisture. When poured over a sheet of white paper it should leave no dust, for dust indicates either the presence of moisture or of fine mealy powder. The size of the grains should be quite uniform, and should have no sharp or angular corners. On pressing between the fingers there should not be a crackling sound due to sharp grains, nor should the grains crush easily! When crushed the grains should show the same uniformity of color. Light colored spots in the powder show that the saltpeter has leached out, due to the presence of moisture, which reduces the strength and reliability of the powder. If there are no white spots it may be assumed that the powder has not suffered from dampness ; so that if it is slightly damp but still uniform in color it can be dried out in the sun and will be as good as ever. A pinch of good powder ignited on a sheet of white paper burns away rapidly, leaving no residue. If black spots remain on the paper they show an excess of charcoal or poor mixing of the ingredients. Yellow spots indicate an excess of sulphur. If holes are burned in the paper they in- dicate an excess of moisture, or other imperfections. no ROCK EXCAVATION METHODS AND COST. Dynamite and Nitroglycerin. Any explosive containing nitroglycerin is commonly called dynamite. Nitroglycerin is made by mixing I to I 1-6 parts of pure glycerin with 3 parts of nitric acid and 5 parts sulphuric acid. The glyc- erin is added very slowly, with constant stirring, com- pressed air usually being used to stir the liquids. The proc- ess of manufacture is exceedingly dangerous. Nitroglycerin is an oily fluid as clear as water when perfectly pure, but it usually has a yellowish tint. Its specific gravity is 1.6, so that it weighs nearly 0.058 Ib. per cu. in., or 102 Ibs. per cu. ft. It freezes at about 38 F. (water freezes at 32), and instead of swelling as water does on freezing, it shrinks about 8 per cent, in volume. Nitroglycerin evaporates rapid- ly at 158 F. ; and even at 104 dynamite will lose 10 per cent, of its nitroglycerin in the course of a few days. Hence the necessity of keeping dynamite in a cool place in sum- mer, and in a warm, but not too warm, place in winter. In small quantities it will ignite and burn up without exploding at 356 F., but at 423 F. it explodes violently. In large quantities, heated slowly, it will explode at 356 F. If the nitroglycerin is impure it will explode at lower tem- peratures. Indeed it is possible for impurities to start a chemical decomposition which will result in a rise in tem- perature ending in spontaneous explosion. If, after the mixture of the ingredients, every trace of acid is not washed out of the nitroglycerin, there is an ever- present danger of chemical action in the nitroglycerin that may lead to an explosion upon the slightest provocation. Chemical decomposition usually liberates nitrous fumes which color the nitroglycerin green. If there is any green- ish color in dynamite it indicates that chemical action has begun and that the material is dangerous to handle. Free acid in nitroglycerin can be detected by blue litmus paper which the acid turns to red. In order to destroy deterio- rated nitroglycerin pour it into a strong solution of sal soda (sodium carbonate) and stir gently with a wooden paddle. EXPLOSIVES. in Pure nitroglycerin has been carried by a rocket to a height of i ,000 ft. and dropped without exploding upon striking the earth. Yet the purest of nitroglycerin is liable to explode by shock if it is confined in a vessel. When im- pure it will explode, even when unconfined, upon receiving a slight shock. A small quantity of nitroglycerin will burn quietly without exploding; but where a large quantity is burning the heat generated will bring the entire mass to a temperature at which an explosion will occur. On account of its sensitiveness to shock when slightly im- pure, nitroglycerin is not used for blasting to any great ex- tent nowadays. It is used in its liquid state chiefly for "shooting" oil wells, so as to open up crevices in the rock through which the oil may flow to the well. The nitroglyc- erin is poured into tin "shells," 3 to 5 ins. diam. by 5 to 20 ft. long, and lowered with a wire to the bottom of the well hole. An iron weight with a hole through its center is strung on the .wire and allowed to drop, thus exploding a cap on the cover of the "shell." Varieties of Dynamite. Dynamite consists of any ab- sorbent or porous material saturated or partly saturated with nitroglycerin. The absorbent is commonly called "dope." A good dope should have minute voids in which the nitroglycerin is held by capillary action. Since the dope acts like a cushion it renders the nitroglycerin much less sensitive to shocks. If 40 per cent, of the weight of the dynamite is nitroglycerin it is known as a "40 per cent, powder" ; if 75 per cent, it is a "75 per cent, powder." The word "powder" is commonly used instead of the word dyna- mite, and, in consequence, it often confuses the hearer or reader who is at a loss to know whether black powder or dynamite is meant. The following are some of the well-known dynamites: ii2 ROCK EXCAVATION METHODS AND COST. ATLAS POWDER (75 per cent.) Nitroglycerin 75 parts. Wood fiber 21 " Sodium nitrate 2 Magnesium carbonate 2 RENDROCK (40 per cent.) Nitroglycerin 40 parts. Potassium nitrate 40 " Wood pulp 13 " Pitch 7 " GIANT POWDER No. 2 (40 per cent.) Nitroglycerin 40 parts. I Sodium nitrate 40 " Sulphur 6 " Resin 6 " Kieselguhr 8 " STONITE (68 per cent.) Nitroglycerin 68 parts. Kieselguhr 20 " Wood meal 4 " Potassium nitrate 8 " DUALIN (40 per cent.) Nitroglycerin 40 parts. Sawdust 30 " Potassium nitrate 30 " CARBONITE (25 per cent.) Nitroglycerin 25 parts. Woodmeal 40^ " Sodium nitrate 34 " Sodium carbonate l /2 " HERCULES (40 per cent.) Nitroglycerin 40 parts. Potassium nitrate 31 " Potassium chlorate 3 1-3 " Magnesium carbonate 10 Sugar i5 2 -3 u EXPLOSIVES. 113 VIGORITE (30 per cent.) Nitroglycerin 3 parts. Potassium chlorate 49 Potassium nitrate 7 Wood pulp 9 Magnesium carbonate 5 HORSLEY POWDER (72 per cent.) Nitroglycerin 7 2 parts. Potassium chlorate 6 Nutgalls i Charcoal 21 GELIGNITE (62^ per cent.) 65 per cent, of blasting gela- I Nitroglycerin, 96 per cent, tin, containing j Collodion cotton, 4 per cent. ^| Sodium nitrate, 75 per cent. 35 per cent, of absorbent, ^ Sodium carbonate : per cent. containing j Wood pulp) ^ per cent FORCITE (49 per cent.) 50 per cent, of blasting gel- ) Nitroglycerin, 98 per cent, atin, containing \ Collodion cotton, 2 per cent. Sodium nitrate 76 per cent. 50 per cent, of absorbent, containing Sulphur, 3 per cent. Wood tar, 20 per cent. Wood pulp i per cent. JUDSON GIANT POWDER No. 2 (40 per cent.) Nitroglycerin 40 parts. Sodium nitrate . . 40 " Resin 6 " Sulphur 6 " Kieselguhr 8 VULCANITE (30 per cent.) Nitroglycerin 30 parts. Sodium nitrate Sulphur 7 Charcoal ii4 ROCK EXCAVATION METHODS AND COST. Many of the "powders" above named are made with dif- ferent percentages of nitroglycerin. A "No. I powder" or- dinarily contains 75 per cent, of nitroglycerin; and a "No. 2 powder," 40 per cent, nitroglycerin; but the manufacturers have a great variety of letters and numbers to denote the different grades of "powder." The following table indi- cates how varied is the numbering and lettering of the dif- ferent grades made by different firms: Aetna Powder, No. I 65 per cent. " No. 2XX 50 " No. 2 40 " No. 3 X 35 " " No. 4 X 25 " No. 5 15 Atlas Powder A 75 B+ 60 B 50 " C+ 45 C 40 " D+ 35 " D 30 " E+ 25 " E 20 F+ 15 " Dynamite (Nobel's) Old No. 1 75 per cent. " No. 2 40 " No. 3 25 - The Absorbent. Alfred Nobel, who invented dynamite in 1866, used porous, earthy powder, called kieselguhr, as the absorbent to hold the liquid nitroglycerin in its pores, somewhat as a sponge holds water. Kieselguhr is a diato- maceous earth which consists of the silicious remains of mi- croscopic plants called diatoms. These diatoms contain microscopic pores or cells which hold the nitroglycerin by capillary action. Of late years sodium nitrate and wood pulp have been very largely substituted for kieselguhr. EXPLOSIVES. 115 I find in the Census Report for 1900 that in the annual production of 42,900 tons of dynamite there were used: 15,800 tons of nitroglycerin, 20,000 tons of sodium nitrate, 5,000 tons of wood pulp and 240 tons of ammonium nitrate. It will be seen from this report that dynamites with an inert base or "dope" of kieselguhr, or magnesium carbonate, are no longer made in America; and that dynamites with an explosive base of the nitrate class have taken their place. It will also be seen that the nitroglycerin used averages about 38 per cent, of the weight of the dynamite as now manufac- tured. Weight of Dynamite. Dynamite is commonly packed in paper cartridges, each "stick" being about 6 to 10 ins. long and of a diameter to slip readily into the hole. The most common size of stick is 1^4 ms - diam. by 8 ins. long, weighing l / 2 to 6-10 Ib. Dynamite is shipped in cases, or boxes, holding 50 Ibs. of dynamite, and must be packed and marked in accordance with the rules prescribed by the rail- road over which it is to travel. Not every user of dynamite knows that an act of Congress (1851) provides that: "Any person or persons shipping explosives without de- livering at the time of shipment a note in writing expressing the nature and character of such merchandise shall for- feit to the United States $1,000." The old Nobel's 75 per cent, dynamite, with the kiesel- guhr "dope," weighs .054 Ibs. per cu. in. The following table gives the weight of 75 per cent, keiselguhr dynamite: Weight of Nobel's No. I dynamite (75 per cent, nitrogen and 25 per cent, kieselguhr) : Diam. Weight in Ibs. Diam. Weight in Ibs. of stick, per inch of stick, of stick, per inch of stick. I in. .042 1^4 .128 i% ins. .065 2 .168 i^ ins. 094 2*4 .212 The manufacturers of "Atlas C" inform me that a i% x 8-in. stick weighs about 0.6 Ib., and that it is one of the ii6 ROCK EXCAVATION METHODS AND COST. "tricks of the trade" to make the absorbent of such material at all grades of dynamite weigh about the same per stick iJ4 x8in.). Thawing Dynamite. The nitroglycerin in dynamite freezes at 42 to 46 F., according to the character of the "dope." When frozen it cannot be exploded by the ordinary caps used in blasting; nevertheless in its frozen state it is exceedingly sensitive to friction or to any breaking or cut- ting of the frozen cartridge. The Annual Report for 1898 of the Inspectors of Explosives of Great Britian states that in 1898 there were 81 accidents in thawing dynamite, result- ing in killing 68 men and injuring 97. Accidents from other causes were 194 in number, resulting in the killing of 52 men and the injury of 216. This shows in a striking manner how dangerous a process the thawing of dynamite is. The following are a few of the methods of thawing that are given in the report as having led to injury or death : Some cartridges being thawed on a stone in a weigh house ; thaw- ing cartridges in front of a kitchen fire ; thawing dynamite on a shovel; cartridges placed near a fire to thaw; cartridges placed in LH oven to thaw ; hot-water thawer, containing dynamite placed on a blacksmith's fire; thawing dynamite with a candle; warming dyna- mite over a blacksmith's fire; heating dynamite in a tin over a candle; rubbing cartridge in hands to complete thawing; cartridge left in pocket of trousers, which were hung before fire to dry ; thaw- ing dynamite in water over a fire; nine separate accidents from re- heating water which had been used in a dynamite thawer, averaging one killed and one injured for each accident. I have italicized this last mentioned cause of accident, be- cause in my judgment it is at the base of the great majority of all accidents from thawing dynamite. It shows that the nitroglycerin leaks out of the dynamite especially when sub- ject to heat in the presence of water. Dynamite should never be thawed by plunging the sticks into warm water. Nitroglycerin will often leak out of a stick even when the stick is dry but is subjected to heat. This I have actually seen. In driving a prospect tunnel in Idaho it was our cus- EXPLOSIVES. H7 torn to thaw dynamite in the oven of a cook-stove; but, when the thawing did not progress rapidly enough, we would hold sticks of dynamite in our hands over the top of the stove. While doing this one day I noticed that a drop of nitroglycerin had leaked through the folds of the paper cartridge and was about to fall upon the stove. In my haste to move the stick away the drop fell upon the hot stove, ex- ploding with a report like a pistol shot and cracking the stove so badly that live coals fell into the oven. The dyna- mite in the oven immediately began to burn up with- out exploding. It is perhaps needless to add that those of us who were in the cabin went out during the time that the dynamite was baking. As stated in previous paragraphs, free nitroglycerin is exceedingly sensitive to shock and heat combined, and one drop of it falling even a short distance upon any hot object will explode, and by its explosion set off any sticks of dynamite nearby. Mr. E. E. R. Tratman has cited an instance where dyna- mite sticks were placed on a canvas cover over a pot of boiling water ; nitroglycerin leaked out, and through the can- vas settled on the bottom of the pot, where it exploded, the water above it acting as a tamping. A man working for me laid some sticks of 75 per cent, dynamite upon a flat stone which he had previously heated by placing hot coals upon it. While in the act of picking up a handful of thawed sticks he was blown to atoms. With- out doubt the cause was the leaking out of a drop of nitro- glycerin which, falling upon the hot stone, exploded the re- .naining sticks. He was using this method directly con- trary to orders, because he had "thawed dynamite all his life in that way." Familiarity breeds contempt for the danger ever present in thawing dynamite, and the manager of blasting operations must not rely merely upon orders to the men not to do this or that, but must be vigilant to ob- serve whether orders are obeyed or ignored. Instant dis- ii8 ROCK EXCAVATION METHODS AND COST. charge of an employee should be the punishment for the slightest infraction of rules governing the use of explosives. Dynamite can be ignited with a match, and will usually burn up without exploding, provided that there are only a few sticks not confined in any way. This fact has had much to do with breeding contempt for the danger attending thawing. Low-grade dynamites (40 per cent, and under) are safer to thaw than high-grade dynamites, because the "dope" is not so thoroughly saturated with nitroglycerin, and for that reason is not so apt to "leak" ; but in the presence of hot water any grade of dynamite will have its nitro- glycerin displaced slowly by the water. In fact, if the manu- facturers are not careful to remove every trace of water from the nitroglycerin there is danger of "leaking." When the paper cartridges feel greasy it is due to leakage of nitroglycerin. When a whitish crust, or efflorescence, is found on the outside of a dynamite cartridge it indicates that the dynamite has been stored in a damp place, or that the "dope" originally contained an excess of moisture. In either case the crust is nitrate of soda that has dissolved out, and such dynamite is almost certain to leak nitroglycerin. It is unreliable, dangerous to handle, and should be de- stroyed at once. Greenish stains inside the cartridge indi- cate that the nitroglycerin is decomposing and is dangerous. I have laid particular stress upon the leaking of nitro- glycerin from dynamite, because it is so common a source of accident and because the fact that dynamite can be ex- ploded under water has lead many to infer that water has no deleterious effect upon it. Dynamite under water begins to part with its nitroglycerin immediately, the water slowly replacing the nitroglycerin in the "dope," and even in cold water a few hours of soaking will materially decrease the percentage of nitroglycerin. In warm water the replace- ment is much more rapid. How to Thaw Dynamite. We have seen how dangerous it is to thaw dynamite by plunging the sticks into hot water EXPLOSIVES. 119 or by allowing live steam to strike the sticks, due to the fact that the water forces the nitroglycerin out of the stick ; and we have seen how sensitive such free nitroglycerin is to slight shocks, especially when hot. We have seen how exceedingly dangerous it is to place dynamite upon a stove, or in front of an open fire, or upon the top of a steam boiler, or upon a hot stove. How, then, can dynamite be thawed with comparative safety? Green manure is an effective and safe material to use in thawing dynamite. On the Croton Dam work the follow- ing method was used: A cubical box 2,y 2 ft. on a side is set inside a box 16 ins. larger on a side, and the 8-in. space filled with manure rammed hard. These two boxes are placed in a cubical hole in the ground and 15 ins. of loosely rammed manure is packed around. The floor of this maga- zine is filled to a depth of 10 ins. with hard rammed manure, leaving a remaining space that easily holds 50 Ibs. of dyna- mite. The lid is provided with a pipe chimney 2^ ft. long, having a sliding cover for ventilation. The dynamite is piled in loosely, the lid closed and manure covered over it to a depth of 12 ins. The ventilator, as a rule, is left slightly open, and at 32 F. outside the powder will thaw in 3 to 5 hrs. ; at o F. outside it will thaw in 8 hrs. This thaw box is cheap, simple and safe. The manure on the bottom of this magazine acts as a cushion to absorb any nitroglycerin that might leak out. It is necessary to change all the manure occasionally. I am not favorably impressed with any method of thaw- ing that involves standing the sticks of dynamite on end, for that facilitates the leakage of nitroglycerin. I have seen a box of dynamite that had been stored on its end in a magazine, and the nitroglycerin had leaked from the cart- ridges saturating the wood of the box. The plan of placing a can of hot water in a small thawing magazine is one of the safest methods that can be adopted. Such a method is illustrated in Fig. 7, page 120. 120 ROCK EXCAVATION METHODS AND COST. Where a very large quantity of dynamite must be thawed daily, a small thaw-house should be built with several doors ENQ. NEWS Plan. Fig. 7. in front, and tiers of drawers that slide out should be placed immediately back of the doors, so that a man cannot enter the thaw-house itself from the front. This prevents men from loitering in the thaw-house, and possibly standing in- side to light a pipe. The dynamite is laid in the drawers (6 ins. deep x 16 x 22. ins.) on a thin bed of sawdust. In the rear of the thaw-house, back of the drawers, room is left for a small hot water radiator such as is used in house heating; i-in. pipes lead from this radiator to the hot water heater which is some distance away from the thaw-house, in a separate building entirely, so that there is no chance for the thaw-house to be set on fire. Under no condition use steam to heat the thaw-house. A temperature greater than that of boiling water (212) should not by any pos- sibility be reached inside the house. The foregoing are the only methods of thawing dyna- mite permitted by the Municipal Explosives Commission in New York City, namely, thawing with manure, and thaw- ing in a dry chamber heated by hot water entirely separate from the fire that heats the water. EXPLOSIVES. 121 Testing Dynamite for Safety. The outside of dynamite cartridges should not feel greasy, nor should there be a trace of free nitroglycerin inside the wrapper. In order to determine whether a stick is leaky, dry it on a clean sheet of brown paper in a room at 60 to 80 F. for about 12 hours. An oily discoloration on the brown paper shows that nitroglycerin has leaked out. Good dynamite will show no such discoloration of the paper. Dynamite that has been frozen and thawed a number of times often leaks, although before the freezing and thawing it did not leak at all. Hence a few sticks should be frozen and thawed three successive times and then tested for leak- iness on brown paper as above explained. Long-continued, high temperature will develop leakiness in a poor quality of dynamite. Hence a few samples should be kept at a temperature of 85 to 90 F. for six consecu- tive days and nights, and then tested for leakiness on brown paper as above explained. A whitish crust on dynamite sticks indicates that it has been damp and that the nitrate of soda or potash has leached out (effloresced) ; and that consequently the dynamite is no longer reliable, and may fail to explode in blasting, beside being dangerous to handle. If the dynamite inside the wrapper shows greenish spots it indicates decomposition of the nitroglycerin, and consequently is exceedingly dan- gerous. Blasting Gelatin. Soluble guncotton dissolved in nitro- glycerin gives a jelly-like substance of yellow color known as blasting gelatin. It has a specific gravity of 1.6 and freezes at 35 to 40 F. as compared with 42 to 46 at which dynamite freezes. It is far more dangerous than dynamite when frozen, being more sensitive to shocks in the frozen condition than when soft. It is peculiarly adapted for use in tropical climates or in summer work, since it does not absorb water and does not leak under any conditions, even after long exposure to 90 F., nor does it leak after re- 122 ROCK EXCAVATION METHODS AND COST. peated freezing and thawing. In cold weather its extreme sensitiveness when frozen makes it exceedingly dangerous. Gelatin dynamite is an explosive containing blasting gela- tin and an explosive "dope." Forcite and gelignite are the two best known gelatin dynamites. They are apt to leak and should be tested precisely as ordinary dynamite is tested for leakage by repeated freezing and thawing and by pro- longed exposure at 90 F. Judson Powder and Contractors' Powder. Judson powder consists of: Nitroglycerin 5 per cent. Sodium nitrate 64 " Sulphur 16 " Cannel coal 15 " The "contractor's powder" made by the Aetna Powder Co. is similar, but it contains 8 per cent, nitroglycerin. They are both free running black powders made honey-combed so as to hold a small percentage of nitroglycerin, and are fired with caps or exploders exactly as dynamite is fired. They are sold in 5O-lb. boxes. Joyeite. Joveite is a free-running, dry powder resem- bling corn meal in appearance. It does not freeze, nor has it ever been found to deteriorate upon exposure to heat. It is composed of nitro-napthalene, nitro-phenol and nitrate of soda. Recently the manufacturers have succeeded in mak- ing it perfectly waterproof. I have seen it charged in holes full of water and exploded without a misfire. The manu- facturers have made strong claims not only for the effective- ness of this powder in competition with dynamite, but for the far greater safety attending its use. The fact that it does not freeze alone entitles it to consideration as a "safety explosive," but it can also be fired into with rifle bullets, hammered with iron on iron, burned up by lighting it with a match, heated to the burning point with electric sparks from a powerful static electric machine, and otherwise sub- jected to the most severe tests without exploding. It will EXPLOSIVES. 123 burn up quietly when a certain temperature is reached, but it takes a strong cap, placed not further than half an inch from the stick of explosive, to explode it. I have personally subjected Joveite to these and other tests for safety, and am convinced that it is incomparably the safest, reliable ex- plosive in the market to-day. Joveite has been in extensive use for about five years, and as yet no accident has occurred in using it. I have fired an iron projectile from a mortar loaded with a weighed quantity of Joveite, and have found it superior to dynamite in hurling power, grade for grade. Joveite is manufactured in four grades, each grade being equal to the various grades of 20 per cent, to 60 per cent, dynamite. I have inhaled the gases resulting from exploding Joveite without suffering from the headache that follows such a test with dynamite; from which it would appear that it would be less objectionable than dynamite in underground work. Joveite can be poured into dry holes like Judson or black powder, but ordinarily it is charged in paper cartridges ex- actly as dynamite is charged, and fired by the same kind of caps or exploders. In its action, Joveite is a trifle "slower" than dynamite, but when the higher grades are used it breaks the rock into smaller fragments. On the great rock excavation work now in progress at the New York Central yards in New York City I find that Joveite has displaced dynamite and is doing more efficient work in the tough rock encountered there, and at less cost than dynamite. The same holds true of several of the large trap rock quarries near New York City. I am able, there- fore, to agree with Prof. Courtney De Kalb, of the School of Mining, Kingston, Ontario, who, in his excellent little "Manual of Explosives," says : "Joveite has been tested by the ablest explosive experts and has never proven unsafe or unreliable. It would seem to fulfil all the requirements of an ideal explosive." CHAPTER VIII. CHARGING AND FIRING. Kind of Explosive to Use. Whether a high power or a low power explosive is to be preferred is dependent largely upon the use to which the rock is to be put, as well as upon the strength of the rock itself. Black powder, with its comparatively slow, heaving action, is used where the ma- terial is quite friable, as in mining coal or galena, or in ex- cavating shale, hardpan and the like. It is also used in small charges placed in a row of holes where it is desired to wedge off blocks of ''dimension stone" for building purposes. Judson powder (which contains a small percentage of nitroglycerin) is considerably more powerful than black powder, and is used in open cut excavation where the rock is of medium strength. It is also used in "chamber blast- ing," where large charges of it are placed at the end of a small tunnel and a mountain of rock dislodged at one shot. In such cases it will break up very hard rock, leaving it, how- ever, in large chunks. A high power explosive like dynamite is invariably used in tunnel driving, shaft sinking and open-cut work in tough rock. Specifications usually prohibit the use of dynamite for quarrying dimension stone, because it is apt to shatter the stone. For quarrying stone to be used as rubble, especially if the stone is tough and occurs in massive layers, dynamite can usually be used without danger of injuring the stone. A 40 per cent, dynamite is commonly used in open cut work, but with tough rock it often pays to use a 50 to 75 per cent, dynamite (or the equivalent grade of Toveite) especially if the rock is to be shattered so that it will pass through a 124 CHARGING AND FIRING. 125 crusher or is to be loaded with a steam shovel. I have found it advantageous to begin blasting in open cuts by using 40 per cent, dynamite. If the rock comes out in too large chunks then to every three sticks of 40 per cent, powder I use one stick of 75 per cent.; and in successive blasts in- crease the proportion of 75 per cent, until the rock comes out in chunks of desirable size. Experiments should also be made in spacing the holes, but of this I will speak more at length later. Having found the proportion of 40 per cent, to 75 per cent, dynamite yielding the best results, it is possible to order a grade of dynamite that will contain the desired percentage of nitroglycerin. Thus, assuming that the best charge is two sticks of 40 per cent, to one stick of 75 per cent., we have : 2 X 40 per cent. = 80 i X 75 P er cent - = 75 J 55 ~^~ 3 5 2 P er cent., which is approximately the grade of powder to order. If the job is small, one can continue to use a mixture of 40 per cent, and 75 per cent, dynamite, but on large work it involves too much trouble to use two grades of powder in the same hole. Moreover, the 75 per cent, dynamite is far more dangerous to handle, particularly where it must be thawed. Managers and foremen are prone to do all their experimenting by changing the spacing of the drill holes or by changing the weight of the explosive used in the charges, instead of experimenting to determine the most effective grade of explosive to use. In tunneling, the "cut holes" are frequently charged with 75 per cent, dynamite, and the "trimming holes" with 40 per cent, dynamite. In tunneling through weak rock, like shale, 40 per cent, dynamite will be found powerful enough even for the "cut holes." Vast sums of money are daily 126 ROCK EXCAVATION METHODS AND COST. wasted in the mines and quarries of the United States through lack of systematic experimenting to determine the most economic grade of explosive and the most economic spacing of drill holes. By taking the work of blasting tem- porarily out of the hands of my foreman I have repeatedly succeeded in reducing the "powder bill" from 10 per cent, to 35 per cent., and I do not hesitate to say that a foreman who can be trusted to select the proper grade of explosive intellegently is "one in a Hundred." Charging Black Powder. After pumping out the sludge, the hole is made perfectly dry by a "wiper," using cotton waste or hay held by a spiral twist at the end of the "wiper." The other end of the "wiper" is often provided with a small spoon for scraping out the sludge at the bottom of the hole. If the hole is a small one the powder may be poured through a tin funnel with a long stem reaching to the bottom of the hole, so that none of the powder lodges upon the sides. In large, deep holes no such precautions are taken. If the hole is horizontal the powder may either be shoved in in paper bags, or a long spoon-like scoop may be used to deliver the powder to the end of the hole where it is dumped by re- volving the handle of the scoop. A safety fuse should be used (or electric cap), and its lower end should be well buried in the powder. If paper cartridges are used, the end of the fuse is shoved into the powder and the paper tied around it ; but do not pull the string so tightly as to pinch the fuse so as to break the powder thread inside it. If the hole is a wet one, a waterproof cartridge must be used. To make such a cartridge, fold a long strip of brown paper spirally around a wooden mandril, slightly smaller than the diameter of the drill hole, at its lower end, letting the edges of the paper overlap well. Before removing the paper from the mandril, dip it into melted paraffine, giving it several coats. In a very wet hole another spiral paper wrapping in the re- verse direction, well paraffined, will insure dryness. Load this cartridge with powder, attach the fuse and immerse in CHARGING AND FIRING. 127 melted paraffine (113 F.). This cartridge will be perfectly water tight, but cannot be rammed. After the drill hole is loaded a tamping of clay or sand is used to fill the hole. The kind of tamping has a very great effect in determining the force of the explosion of black powder. Clay is unquestionably better than sand and should be used for the first few inches anyway. Dry clay is first pressed down with a wooden tamp rod. Never use a metal rod and never ram the tamping at the start, for fear of an explosion. Follow with ordinary damp clay pressed firmly to place, and after a thickness of three inches of tamping is over the powder, ram by tapping the end of the tamping rod with a hammer. In holes i in. in diam. the charge will not blow out if there are 7 ins. of good tamping. In general the tamping will not blow out if it is 7 to 10 times as long as the hole is wide. Nevertheless the tamping should be carried to the surface of the rock if the greatest effect of the powder is desired. If there are any spaces between the powder and the sides of the hole, or between the powder and the tamping, the effect is to cushion the blow of the ex- plosion. In quarrying dimension stone this cushioning ef- fect is sometimes desirable, and it is purposely secured by filling several inches of the hole above the powder with hay, tow or the like, followed by several inches of clay tamped lightly, and finally by well packed tamping. This is called "expansion tamping." In firing black powder by electricity, electric exploders of low power are used. There is no advantage in using power- ful detonators, because black powder cannot be detonated, but explodes in the same way whether a match or an elec- tric spark or another explosive fires it. Charging Dynamite. The charge should fill completely the part of the hole that it occupies, and should be packed solid. Experiments show that even a slight air cushion greatly weakens the force of the explosive blow. Since the sticks of dynamite are slightly smaller in diameter than the 128 ROCK EXCAVATION METHODS AND COST. hole, the paper of the cartridges (excepting the last one) should be slit lengthwise with a knife * and after each stick is dropped or pushed into the hole, press it well home with a wooden rammer. If there is standing water in the hole do not break the paper of the cartridge, and do not ram, but use a cartridge that will just fill the hole. In wet holes it is well also to daub grease over the cartridge wher- ever water might enter through a fold in the paper. The cartridges should never be so large as to require forcing to get them to the bottom of the hole. Remember that a drill hole tapers toward the bottom. Dynamite should never be rammed, but merely pressed home ; and a steel or iron tamp- ing rod should never be used for this purpose. The last stick, or "primer," is provided with either a fuse cap or an electric detonator. If a fuse is used a common way of load- ing- is first to slip the end of the fuse into the cap, bite the end of the cap shell so as to pinch it upon its fuse ; and, if the blaster survives this part of the operation, the next step is to dig a hole in the middle of the dynamite stick with a wire nail; push the cap into the hole and pinch the plastic dynamite around it; take a half-hitch with the fuse around the dynamite cartridge and lower it or push it to place. A cap should never be crimped onto the fuse with anything but a "crimper" made for the purpose. A half-hitch in the fuse is quite apt to break the powder thread inside the fuse and thus cause a misfire. If an electric exploder is used, taking a half-hitch with the fuse wires is apt to result in breaking one of the wires away from the platinum bridge to which it is soldered, and thus causing a misfire. An expert, however, who is skilful and careful may use the half-hitch without causing misfires. The method recommended in all catalogues of manufacturers is first to open the end of the * Never cut with a knife or otherwise rupture a stick of dynamite that is frozen or partly frozen. Some authorities recommend using a copper blade instead of steel, because the steel might strike a spark if there were any grit in the cartridge. CHARGING AND FIRING. 129 "primer" cartridge by folding back the paper; then to in- sert the cap part way into the dynamite after boring a little hole in the dynamite with a wooden stick with a rounded point. The cap is left projecting about ^ in. above the dynamite, so that by no chance can the fuse set fire to the dynamite and thus reduce the force of the explosion. The ends of the paper cartridge are drawn up around the fuse or the fuse wires, and tied with a string as in Fig. 8, one end of the string being left long enough to let the "primer" down to the bottom of the drill hole. In any case the cap should fit tightly in the dynamite, for even a slight air space will serve as a cushion to reduce its force and so weaken the force of the final explosion. In wet holes, smear grease around the end of the cap. The end of the fuse should be cut square across, preferably with a "fuse cutter," and then, holding the fuse upright, slip the cap over it. It should require no effort at all to slip the cap on, for either pressing or twisting the cap on may explode it. If the fuse is too large whittle it down with a knife; if too small, wrap paper around it. Crimp the shell of the cap about ^ in. from its end with the "crimper," which is combined with the "fuse cutter." At the other end of the fuse cut a slit y 2 in. long to expose the powder core for lighting with a candle flame or torch. Dry paper may be twisted around the end to insure lighting, but it is not good practice to soak cloth or waste in oil and wrap it around the fuse. Of course the end of the fuse should not be allowed to drop into water, at least not until the fire inside has crept some distance down into the fuse. The "primer" should not be lowered into the hole by the fuse, because in this way the cap is often pulled loose leaving an air cushion that greatly reduces the force 130 ROCK EXCAVATION METHODS AND COST. of the explosion. When the "primer" has been lowered it should never be compressed or rammed; but the tamping should be placed upon it immediately. To emphasize the importance of inserting a cap and fuse in the end rather than in the side of a stick, a quotation from a paper by Mr. A. W. Warwick in Mines and Minerals will serve: "There was no> doubt in my mind, after studying the method of loading, that there was a possibility of the burn- ing fuse setting fire to the dynamite cartridge on top of the primer before exploding the cap. In order to see if this were the case or not, a piece of pipe 12 in. in length and ^ in. in diameter was obtained, a piece of fuse was passed through and a cork was forced in so as to hold the dyna- mite; a stick of dynamite was squeezed into the pipe and held in place by a plug. The fuse was fired and develop- ments were awaited at a respectful distance. Out of seven- teen experiments six resulted in an explosion. The fumes from the explosion were very acrid, dense and rather ruddy in color. The nitroglycerin was fired by heat and not by de- tonation, and the fumes had the appearance and odor of fumes generated by incomplete combustion." The best tamping is dry clay or bits of shale, and even where sand is used for the major portion of the hole it will pay to use clay balls for the first foot or so, the clay being moist enough to roll into pellets. A handful or two of sand may be poured into the hole first to cover the "primer" ; and then follow with clay. The clay pellets should be lightly compressed for the first 6 ins., and above that the tamping may be compressed with increasing force. Sand is gen- erally used for tamping above the first foot or two because it can be poured in with much greater rapidity.* Experi- menting with different kinds of tamping on any given class of work is time 'and money well spent, for it is not a fact that dynamite needs no tamping, or that water makes a good * I would suggest pouring enough water into the hole after the sand is in to dampen it, for damp sand arches better than dry sand and better resists the pressure. CHARGING AND FIRING. 131 tamping. Mr. W. L. Saunders is authority for the statement that one pound of dynamite under a water tamping will not do as much execution as one-quarter of a pound in dry blast- ing. Bear in mind that tamping is cheaper than dynamite even if several dollars a ton are paid for tamping imported by rail. While working the tamping rod with the right hand, hold the fuse or the fuse wires with the left hand so as to detect and thus avoid rubbing the fuse with the tamping rod. Some blasters use a tamping rod with a beveled end, and hold the rod so that the sharp edge of the bevel is always on the side of the hole farthest from the fuse. To know which side the sharp end is on, cut a longitudinal groove in the tamping rod. Some authorities recommend placing the "primer" at the bottom of the charge, instead of at the top ; others say that the "primer" should be placed at the middle of the hole. Dynamite explodes with such suddeness that we may well doubt whether it makes any difference at all where the primer is placed, so far as the execution is concerned. It is often advisable, in deep holes, to place the dynamite in several distinct charges separated by tamping, and in this case each charge should have its own cap and "primer"; but this is a matter quite aside from the present discussion and will be taken up later. Handling dynamite sticks with the bare hands will give a headache to anyone not used to it, because of the nitro- glycerin absorbed through the pores of the skin. The ob- vious preventative is to wear gloves. Judson powder is charged like black powder, but it is" fired by using a "primer" consisting of a stick of dynamite in which a blasting cap is imbedded. Joveite is charged and fired like dynamite. Firing by Electricity. In New York City it is now com- pulsory to fire all blasts by electricity on account of the greater safety of electric firing. Electric firing is not only safer than fuse firing, but, in open cut work especially, it is more effective, because the simultaneous explosion of 132 ROCK EXCAVATION METHODS AND COST. charges in a row of holes obviously reduces the work to be done by each charge as compared with fuse firing by which one charge explodes in advance of the neighboring charge. In tunneling, where the center cut holes must be fired in advance of the outer holes, it will probably continue to be the practice to fire by fuse, using fuses of different lengths so as to regulate the order in which the charges in the different holes will explode, but there are few places outside of tunnels and shafts where fuse firing is preferable to electric firing from any point of view ; and even in tunnel work there are many blasters who prefer electric firing. For firing by electricity the electric detonator, A (Fig. 9), is placed in the "primer," and the fuse wires, B, are car- ried up along the "primer" and tied with a cord, C, to the "primer." The fuse wires attached to each cap are fur- nished by the manufacturers in varying lengths to suit varying depths of drill holes ; but it is not necessary to have fuse wires that will reach to the mouth of the drill hole, for connecting wires may be spliced on * to the ends of the fuse wires and the 1 splice wrapped with insulating tape. ~J%^ '.Ljl^ When a splice is to be made thus, it is well to cut 3 or 4 inches off one of the fuse wires so that one splice will not come directly opposite the other ; for when this is done it is necessary to wrap insulating tape around one of the splices only, and it is not nec- essary to wrap even one splice except in damp holes. A splice is made by cutting the insulating material away for 2 or 3 ins. back of the ends of the wires to be joined, scraping the wires IB ; until they are bright, and twist- ing the clean wires together, as shown in Fig. 10. Insulating tape Fig. 9. CHARGING AND FIRING. 133 is y 2 to 34 in. wide and comes in J^-lb. rolls. It is often used to cover splices made in connecting wires when the splice comes in contact only with dry rock on dry Fig. 10. earth. Practically no electricity can leak through dry rock or earth, so that there is no necessity of insulating the splices unless the bare wire is apt to come in contact with moist earth or water. The fuse wires from each hole are con- nected right and left with the fuse wires from the neighboring holes, so as to form a continuous cir- cuit with the holes in series (Fig. n); then the end of the fuse wire of the hole on the extreme left is connected with a "leading wire" that runs to the electric Bcrff-ery battery, and in like manner the other "leading wire" from the battery is connected with the fuse wire of the hole on the extreme right. This final connection should not be made at the battery until all workmen are at a safe distance. When it is made, lift the handle of the battery and press it down, at first with moderate speed, but finishing with full force. The leading wires must be long enough so that the electric battery is 200 to 500 ft. away from the blast, and in a di- rection back of the face (in open cut work). The sun should not shine in the eyes of the blaster, for he should be able to 134 ROCK EXCAVATION METHODS AND COST. see and dodge any falling fragments of rock. It is well to wind the two leading wires together into one cable, sepa- rating them only for a short distance from the blast; then, after firing, this cable can be wound up on a reel. As the copper connecting wires are expensive, the blaster should collect all fragments of wire after each blast and wind them upon a reel to be spliced and used again. Misfires. A misfire when an electric battery is used may be due to any one of several causes: (i) A blasting cap may be defective, due to the fact that water has penetrated the cap or to the fact that the platinum bridge in the cap has become unsoldered; (2) short-circuiting may be caused by a half-hitch taken with the fuse wire around the primer (which is a poor but common practice) which may have broken the insulation so as to permit the electric current to pass from one wire to the other without passing through the cap; but in this case charges in all other holes of the series will explode; (3) a defective splice in the connecting wires may have broken the circuit ;( 4) a fuse wire may have been broken in the process of tamping; (5) the bat- tery may be overloaded. This last cause is one of the most common causes of misfiring. Any given battery will ex- plode a limited number of caps in series through a given number of feet of copper wire of given diameter. Increase the number of caps, or increase the length of wire, or de- crease the diameter of the wire, and the battery will fail to explode the caps. The copper of the leading wires should be at least twice as thick as that of the connecting wires in order to reduce the resistance to the passage of the current as far as possible. Never load a battery up to its limit, but have a good margin of surety that it will explode all the caps in the series. Saunders is authority for the statement that a weak battery may explode part of the caps and leave the rest unexploded, due to variations in the resistance of the platinum bridges in the caps. In case of a misfire no one should approach the holes for half an hour if electric CHARGING AND FIRING. 135 firing is used, and not for several hours if fuse firing is used. This is the rule laid down by several authorities; but it is doubtful whether it is ever followed in practice. I fail to see any good reason for waiting more than a few minutes after a misfire by electricity ; but with a fuse there is always danger that the flame may smoulder and creep slowly past some break in the powder thread and finally explode the cap. After waiting some time it may be necessary to remove part of the tamping in the hole and put down another "primer." This is a dangerous operation at best, and if black powder is used a copper or wooden (never steel) spoon should be used in removing the tamping. In any case never remove the tamping entirely, but leave the 3 or 4 ins. of the cushion tamping above the charge in place. Then place several sticks of dynamite and a "primer" on top of the first charge and fire again. The New York City rules forbid removing tamping at all, and require that a new hole shall be drilled not closer than 12 ins. to the old hole, and that in this new hole a heavy charge be loaded and fired. Whenever an ex- plosion fails to carry away the rock clear to the bottom of a drill hole it is forbidden to begin drilling in the bottom of the old drill hole, as part of the former charge may remain unexploded in the bottom of the old hole and explode under the blows of the drill. I question whether it is always safe practice to drill a new hole within a few inches of an old hole, hoping to be able to explode the charge in the old hole by a blast in the new hole. A safer practice, which I have followed in open-cut work, is to drill the new hole several feet from the old hole and to a depth that will bring the bot- tom of the new hole on a level with the top of the charge in the old hole. Then upon blasting the new hole the shat- tered rock around the old hole may be removed, the dyna- mite exposed, a cap inserted and fired. Joveite possesses a decided advantage over any other explosive in common use, when it comes to removing tamping after a misfire due to a poor cap; for there is no danger of exploding it either by 136 ROCK EXCAVATION METHODS AND COST. shock or by a spark. Care should be taken, however, to use a copper or wooden spoon in removing the last part of the tamping, for while a spark will not explode Joveite, it will set fire to it. Methods of Firing. Black powder is exploded by direct contact with any incandescent substance, such as the burning train of powder of a safety fuse; but dynamite, Judson powder and Joveite are exploded only by detonators, or "caps," as they are commonly called; the cap in turn being exploded either by a safety fuse or by an electric current. There is absolutely no advantage in using a cap to explode black powder, for it will not produce any greater effect. Black powder cannot be detonated, but always explodes slowly. Safety Fuse. William Bickford, of Cornwall, patented his justly celebrated safety fuse in 1831. It consists of a powder thread around which is spun jute yarn, which is af- terward waterproofed with coal tar. The core of powder is so tightly compressed in a thin thread that the fire travels along it slowly, the rate in a good fuse being I ft. in 1-3 to l /2 min. Single fuses have only one layer of waterproof yarn around the powder; double fuses have two layers of water- proof yarn. Tape fuses are wound with waterproof tape, overlapping. In wet holes double fuse and tape fuse are used. For blasting under water gutta-percha covered fuse is used. Caps. A cap (also called a blasting cap, a detonator, or an exploder) for exploding dynamite consists ordinarily of a mixture of mercury fulminate and potassium nitrate or chlorate placed in a small copper capsule, the open end of which is plugged with sulphur, if the cap is one made to be fired with electricity ; but if the cap is to be fired with a fuse the fulminate is covered with shellac, collodion, thin copper foil or paper, and the end of the capsule is left open to re- ceive the end of the fuse. Caps for use with a fuse are 1 1 / 2 ins. long and of 22 caliber. CHARGING AND FIRING. 137 Caps are commonly graded according to the amount of fulminate in the cap, as follows : Single strength (X.) ...'.... 3 grains of mercury fulminate Double " (XX.) 6 " " Treble " (XXX.) . ... 9 " " Quadruple" (XXXX.)..i2 " " And so on. There is, however, no set rule or law in the United States as in England governing the grading of caps. In England the manufacturers are compelled to grade their caps as fol- lows : Grade of Cap No. i No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8 Charge Fulminate grs 4.6 6.2 8.3 10 12.3 15.4 23.1 30.9 Fulminate of mercury when heated to 367 F., or when forcibly struck, explodes with great violence. The presence of a small per cent, of moisture prevents explosion; hence caps stored in a damp place deteriorate rapidly. Mr. W. J. Orsman has shown conclusively how quickly caps deteriorate in a damp place by placing a few caps in a bottle on top of some damp saw-dust. In 24 hrs. the caps had absorbed o.i per cent, moisture ; in 14 days, 0.4 per cent. ; in 22 days, 0.5 per cent. After 40 hrs. the caps failed to explode dynamite, although they would still explode themselves. Mr. A. W. Warwick has shown * how important it is to use powerful caps in exploding dynamite to get the best results. To test the strength of caps he recommends standing a cap on a sheet of lead iy 2 X i l /2 ins. X H to % in. thick, enclosing it with a pipe and exploding it. A strong cap will pulverize the cop- per shell and the particles of the shell will make fine marks in the lead, around the deep hole left where the cap stood. A weak cap will not pulverize the copper shell, but will tear it into larger pieces, which make large marks in the lead around a shallower hole where the cap stood. The stronger the cap the more powerful will be the ex- plosion of the dynamite. This is well shown by the follow- ing tests made by Mr. Warwick and published in Mines and Minerals. * Mines and Minerals, Sept. and Oct., 1902, and Feb., 1904. 138 ROCK EXCAVATION METHODS AND COST. The dynamite was tested with the "Abel block." An "Abel block" is a cylindrical piece of lead, 5 ins. diameter by 5 ins. high, with a 24-in. hole, 2 l / 2 ins. deep, in which a charge of 5 grams of dynamite is placed in the form of a small tissue paper enclosed cartridge. The cartridge with its cap is pushed home and tamped with sand that has passed a 60- mesh screen. The block is placed between two i X 6 X 6- in. iron plates and the whole held together with two iron rings, i^ X i^-in. section, and securely wedged. The fuse is fired and the resulting cavity in the lead is measured by pour- ing in water, then by deducting the volume of the original 24-in. bore hole, the increased volume due to the explosive is ascertained in cubic centimeters. To determine the theo- retical efficiency a simple proportion serves : 35 per cent, powder : 40 per cent, po'wder : : 129.3 cu. cm. : 141.2 cu. cm. Careful tests showed not to exceed 4 per cent, variation in the effectiveness of samples taken from different parts of the same commercial stick of dynamite, while even less varia- tion wa*s found in sticks taken from various parts of different boxes. This leads to the very important conclusion that mis- fires in mining or quarrying cannot be attributed to lack of uniformity of cartridges, when the dynamite is not frozen. Tests on two different makes of dynamite showed the effec- tiveness of varying percentages of nitroglycerin thus: 30 per cent, dynamite .35.3 35 per cent, dynamite 44.5 40 " " " 43-1 40 " " " 47-6 60 " 61.7 60 " " 63.3 These results show conclusively that the absorbent dope of low-grade powders adds materially to their effectiveness. Another set of experiments was made to show the relative strength of a given dynamite using different strength of caps : 3x cap. 4x cap. 5x cap. 35 per cent, dynamite 37.4 40.2 44.7 40 " 40.9 41.6 46.8 60 " " " 59.7 62.2 63.3 CHARGING AND FIRING. 139 From which we see that with 35 per cent, dynamite, the 5x cap gives 19^ per cent, increased efficiency as compared with the 3x cap; with 40 per cent, powder, 15 per cent, increased efficiency ; 60 per cent, powder, not quite 6 per cent, increased efficiency. As a further confirmation of these tests the running of three cross-cut drifts in diabase showed similar results. The drilling was done by hand hammers with %-in. drills, and 40 per cent, dynamite was used. The work was done in winter when the outside temperature was many degrees below zero. The different caps were used for one week in each of the three drifts, and the advance carefully measured. The "duty" of the dynamite was measured in cubic feet of rock loosened by a pound of dynamite, and was as follows : 3x caps. 4x caps. 5x caps. Drift No. i 19.4 23.5 22.8 " No. 2 17.6 24.2 25.1 " No. 3 18.7 22.6 23.7 Average "duty" 18.6 23.4 23.8 Cost per ft. of drift $6.34 $5-75 $5-7 2 As a result of these tests, 5x caps were used in winter and 4x caps in summer. When the 3x caps were used the dyna- mite fumes were so bad as to make it impossible for the men to work well. Caps should always be stored in a dry atmos- phere; keeping them long underground is apt to weaken them materially. Fig. 12. Electric Detonators. The electric detonator or "platinum fuse," as it is called by some makers, has a composition sim- ilar to the fuse cap described in the previous paragraph, and all that is there given regarding strength and use of caps ap- plies to the electric cap, or "fuse." Fig. 12 shows an electric 140 ROCK EXCAVATION METHODS AND COST. cap in which A is the copper shell ; B the fulminate of mer- cury ; C the insulated copper fuse wires ; D the bare ends of the fuse wires projecting through the sulphur plug, F; E the platinum wire called the "bridge" soldered to the fuse wires. This platinum "bridge" is heated red hot when the electric current passes through the wires, and thus explodes the fulminate of mercury. The fuse wires, C, are 4 ft. to 30 ft. long, depending upon the depth of the blast hole. They are insulated with cotton. The ends of these fuse wires are connected to "connecting wires" that reach from hole to hole. The sulphur plug does not make detonators entirely water- proof, for the copper of the shell expands more than the sulphur upon any rise of temperature in the air, and thus opens a slight crack through which moisture may reach the fulminate of mercury. Shoemakers' wax, warmed, then cooled until jelly like, if daubed around the end of the ex- ploder, will keep out water when using exploders in wet holes. Tallow may also be used, but is not so effective. In nine cases out of ten, failure to explode a series of holes by electricity is due to a defective exploder. The cause may be moisture that has reached the mercury fulminate while the caps were stored or after charging in the hole ; or it may be that the platinum bridge has broken from the copper fuse wires. Care should be taken never to pull hard upon the fuse wires, for fear of loosening the platinum bridge. CHAPTER IX. METHODS OF BLASTING. The Theory of Blasting. The rules commonly found in text books are based upon theories which in turn are founded upon assumptions as to conditions not often encountered in practice. One may safely look with suspicion upon any dog- matic rule as the amount of explosive to use and the spacing of blasting holes. In the first place most of the "rules for blasting" were originated by users of black powder, and are valueless when applied to high power explosives. In the second place, many of the rules apply only to single shots, and not to the simultaneous firing of many holes by elec- tricity. In the third place, practically all of the rules ignore the use to which the blasted rock is to be put. The last is perhaps the most conclusive reason why "rules for blasting," no matter how high the authority back of them, are apt to be exceedingly misleading. Rock that is quarried for dimension stone masonry re- quires close spacing of blast holes on a straight line, but these rows of holes themselves may be several feet apart. When holes are drilled close together in this way and fired simul- taneously, using very small charges of black powder in each hole, a huge block of solid rock may be wedged off without shattering it. Rock that is quarried for concrete or macadam purposes should be well shattered to save, the cost of sledging and "blockholing" into sizes that will enter the crusher. This means an entirely different spacing of the holes from di- mension stone quarrying, and it usually means the use of a high power explosive that will thoroughly shatter the rock. In the two cases just cited the rock is put to some use after it is quarried ; but in open-cut work on canals and railways the rock is frequently wasted, and is broken up only to as 141 142 ROCK EXCAVATION METHODS AND COST. small sizes as can be handled conveniently by the appli- ances available. In some cases these appliances are simply crowbars for levers and boards, for inclined planes, up which the stone may be rolled by hand into wagons. In other cases derricks that can lift only a ton or so are available; while in still other cases cableways that can handle a mass of ten tons are to be used ; or it may happen that steam shov- els are to load the stone, in which case it must be shattered to comparatively small sizes. With all these variable factors, how absurd it is to la) down any inflexible "rules for blasting," and yet we find such rules in every text book. Often, it is true, the author forewarns us that judgment must be used in applying the rules, but neglects to tell us afterward where and how to ac- quire that judgment. Indeed, by the very act of omitting to say anything further as to the exercise of judgment, the author permits us to forget that he has told us that the rules must be used with judgment. I cannot hope to be able to explain how blasting should be done in every case, but I hope to keep constantly before the reader the desirability of reasoning, instead of persuing the much easier, but in the end the more costly, practice of following "rules." The Crater Theory. Regarding the theory of blasting, much more has been put into print than is warranted by the meagre scientific experiments made by the writers. A com- monly quoted theory of the action of an explosive is one that may be termed "the crater theory." According to this theory an explosive buried in a mass of earth or rock will blow out a funnel-shaped crater whose sides are supposed to have a slope of i to i, if the surface of the earth or rock is hori- zontal, as shown in Fig. 13. The distance D B; or, to be more exact, the distance D F from the surface of the rock or earth to the center of the charge of powder, E B, is called the "line of least resistance." The volume of the funnel or crater is : V= Jl x w l 2 = I 3 (nearly) METHODS OF BLASTING. 143 Hence the general formula for the volume of rock loosened by one charge so as to form a funnel crater is : V = ml 3 According to Schoen, m = 0.4 for tough, soft rock, m = 0.9 for hard, brittle rock. This means that in tough soft rock the sides of the crater are steeper than i to I, but in hard, brittle rock they are nearly I to I. Note carefully that this theory assumes two things ; first, that only one charge of explosive is fired at a time ; second, that the rock is homogenous and has no seams or cracks. Except for chamber blasting, this theory, in my opinion, is not worth the ink it is printed with; because, in practice, shots are not fired singly nor is the rock ordinarily free from seams and joints. If the drill holes were bored vertically in rock, as in Fig. 13, and heavily charged with black powder, it might blow out the tamping and fail to rupture the rock at all. The writ- ers who have accepted the "crater theory" have, therefore, reasoned that drill holes should be drilled at an angle with the surface, along some such line as A B, instead of along the line of least resistance, D B, as shown in Fig. 13. If H K---I' H Fig. 14. this were done the length of the line of "least resistance," D B, would be about 0.7, or nearly y% the length of the drill hole A B. Hence we find the rule laid down with the ut- most dogmatism, that "the line of least resistance should never be more than three-quarters the length of the drill 144 ROCK EXCAVATION METHODS AND COST. hole." Then they go a step further and show us a drill hole in a bench, as in Fig. 14, placed back from the face so that the distance from the face is three-quarters the depth of the hole, and they tell us that this ratio should never be exceeded. With single shots, with black powder, with a rock perfectly homogeneous, we may concede that there is some reason in this rule, but as it is given in text books without any qualifi- cations or explanations at all, the rule is worthless. With dynamite I have often placed a row of holes a distance back from the face just twice as much as this rule permits; and the result has been excellent when the rock was much seamed and easily broken by holes fired simultaneously. The advocates of the crater theory of blasting recommend that the "rock coefficient" be obtained for any given kind of rock as follows : Drill a row of holes 2 ft. back from the vertical face of rock to be blasted down in benches. Let these vertical holes be 6 ft. apart and 3 ft. deep. Charge one hole with a very small charge of explosive ; charge the next hole with a greater charge ; and so on, charging each hole heavier than the last. Tamp and fire the holes separately, and select that hole which has given the best results the one that has broken rock without hurling it far. Suppose this particular hole was charged with 0.5 Ib. of dynamite, then the "rock coefficient" is : o 5 o. c ^f=ir =0 - 06 The rule is : Divide the charge of the explosive in pounds by the cube of the line of least resistance in feet to get the "rock coefficient." Then, they tell us, we have only to mul- tiply this "rock coefficient" by the cube of the line of least resistance that we intend to use in practice, to ascertain the proper charge for each hole. Thus, if we are going to drill holes so that the line of least resistance will be 8 ft., we mul- tiply 0.06 by 8 3 , or 0.06 X 8 X 8 X8, and we get 30.72 Ibs. as the proper charge per hole. I have tested this rule, and, as I had anticipated, I have found that it gives too large a METHODS OF BLASTING. 145 charge for deep holes in stratified rock with a long line of least resistance. Wherein is the "crater theory" defective? To begin with it assumes that the work the powder has to do is en- tirely dependent upon the volume, or weight, of rock to be moved ; that if 0.8 Ib. of powder will break I cu. yd. of rock in a shallow hole, the same proportion of powder will break the rock in precisely the same manner in a deep hole, re- quiring always the same fraction of a pound of powder per cu. yd. whether the holes are deep or shallow. Every ex- perienced blaster knows that this is not so. Generally the deeper the holes (and consequently the longer the line of least resistance) the less the number of pounds of powder required per cubic yard. We have, therefore, a reductio ad absurdum so far as the crater theory is concerned. More- over, when we consider the work that an explosive has to do, we find no good reason for assuming that equal weights of powder will break equal weights of rock regardless of depth of holes. The force of the powder is expended in four ways : (i) shearing the rock loose; (2) in overcoming the inertia of the rock mass; (3) in heating the rock; and (4) in im- parting motion to the surrounding air. If all the work were expended in shearing the rock, then since the volume of a crater varies as the cube of the line of least resistance, while the area of the slopes of the crater varies as the square of the line of least resistance, it is evident that the shorter the line of least resistance the greater the unit work done by the powder in shearing loose the rock. Thus a crater 2 ft. deep, having an apex angle of 90, has an area of side slopes of 35.4 sq. ft. and a volume of 8.4 cu. ^d/.7or 4.2 sq. ft. per cu. ft. A crater 8 ft. deep has an area of 567 sq. ft. and a volume of 536 cu. ft, or i. 06 sq. ft. per cu. ft. Hence the work of shearing off the rock in the 8-ft. crater is about one-fourth as much per cu. yd. as the corresponding work in the 2-ft. crater. In a well-charged blast, where the rock is merely shattered, but not heaved, the work of overcoming the inertia 146 ROCK EXCAVATION METHODS AND COST. of the rock is comparatively slight; but we do not know, and can at present not even guess, what portion of the energy of the powder is entirely lost in heating the rock and in im- parting motion to the air. For all that can now be proved to the contrary, we might assume that this percentage of lost work is a constant percentage in large and in small blasts. If so, the crater theory crumbles at once into meaningless words ; if not so, the advocates of the crater theory still have to prove that their primary assumptions are based upon rea- sons having even the semblance of scientific truth. I have a great respect for any one who formulates a theory that ac- cords with experience; but I have no respect for a theory that utterly fails to help the practical man and actually mis- leads him, as exemplified in the crater theory of blasting. Placing Drill Holes. In the days of black powder it was essential to consider carefully the position of seams and bed- ding planes in the rock so as to place the drill hole where the powder would have the least possible work to perform in shearing off the rock. Upon, the introduction of dynamite it was found that less care need be taken in placing the drill holes with regard to natural seams in the rock, excepting in quarrying dimension stone. Nevertheless, some attention should always be given to the position of planes of weak- ness, especially in stratified rock. In open-cut work, where the rock is excavated in benches, it is well to have the bot- tom of the drill hole stop just short of a plane of stratifica- tion or weakness in the rock, even if to do so necessitates drilling holes somewhat shallower than they would be drilled in rock uniformly solid. In tunneling and shaft sinking, where hand drills are used, care is always taken to locate the "cut holes" with reference to seams or planes of weakness in the rock. If the strata in a hand-driven tunnel dip down- ward toward the face, drill and fire the first holes near the roof; if the strata dip down away from the face, drill and fire the first holes near the floor. In any case drill a hand- driven hole as nearly perpendicular as possible to the planes METHODS OF BLASTING. 14? of weakness in the rock. The spacing of holes will be given in subsequent chapters. Springing Holes. In order to enlarge a drill hole so that a greater charge of powder may be placed in the hole, a few sticks of dynamite may be exploded at the bottom of the hole so as to make a chamber there. This process is variously termed "chambering," "springing," "shaking," "bullying," etc. In earth and soft rocks like shale, the dynamite used in springing the hole compresses the material at the bottom of the hole and thus enlarges the hole ; in hard rock the dyna- mite pulverizes some of the rock and hurls the powdered rock out into the air, leaving a chamber. In very soft ma- terial the first springing will make a sufficiently large cham- ber; but in hard rock repeated springing, with increasingly large charges of dynamite, becomes necessary. Thus in springing 2o-ft. holes in sandstone I have used for the first springing shot 2 sticks of 40 per cent, dynamite; for the second springing shot, 5 sticks ; for the third shot, 20 sticks. The chamber thus made was charged with 8 kegs, or 200 Ibs. of black powder. Springing can be used with great ecohomy of explosives in open-cut work where deep holes can be thus enlarged and charged with black powder or Judson powder. It is indeed surprising to note how often holes are charged with dyna- mite and fired without any attempt to test the springing method of blasting. On the other hand, I have frequently seen the springing method used under conditions not at all favorable; thus in 6- ft. holes in hard limestone, where a sewer trench was being excavated, the contractor was firing in successive shots a total of 8 or 10 sticks of dynamite for the sake of crowding a few more sticks into the bottom of the hole for the final shot. A much more economic arrange- ment of powder in sewer trenches is to distribute it in small, separate charges from the bottom to near the top of hole, and not to concentrate it at the bottom. In tunneling, on the other hand, it is always desirable to concentrate as much of 148 ROCK EXCAVATION METHODS AND COST. the charge as possible at the bottom of the hole ; and, were it not for the fumes and dust produced by springing, it would always be good practice in railway tunneling through com- paratively soft rock to spring- the holes. With water for spraying the air after each shot the objection to springing the holes would disappear. In stoping, shaft sinking and tunneling^ there is every reason for concentrating the charge as much as possible at the bottom of the hole, and no pains should be spared in experimenting with the springing method of blasting, even to the installation of a water supply system for clearing the air of dust and fumes after each springing shot. In open-cut work it is not so essential to have the charge in the bottom of the hole if dynamite or Joveite is used ; but if black powder or Judson powder is to be used a sufficient quantity cannot be charged in the hole of ordinary diameter unless the holes are placed close together. The use of the springing method enables the blaster to place the holes far apart in stratified rocks (and thus reduce the cost of drilling), and to load them with large charges of low- grade powder, thus reducing both the cost of drilling and of explosive. In springing a deep hole it is customary to tamp the springing shot with a small quantity of sand, no attempt being made to fill the hole with tamping. In shallow holes in mines and tunnels less than a stick of 75 per cent, dyna- mite, well packed, may be used for the first springing shot, lowering or shoving into the hole a small "primer" contain- ing the cap ; tamp with fine sand, and fire. After the hole has been sprung, if it is to be loaded with black powder, care should be taken not to put the powder in before the rock has cooled off. It sometimes happens that the chamber made by springing is not large enough to hold the necessary charge of powder ; in such, cases there is an advantage where Judson powder has been used, for the Jud- son powder may be ignited and will burn up without explod- ing, thus making it possible to enlarge the hole by further METHODS OF BLASTING. 149 springing. Where the rock strata are inclined at a high angle it sometimes happens that the shock of springing will cause a slip, closing up the chamber and causing a loss of the hole. Blasting with Powder and Dynamite Together. In blast- ing blue sandstone on the Wabash Railroad in eastern Ohio, Mr. W. M. Douglass, of Douglass Bros., has found that the most effective way of blasting so as to reduce the stone to small sizes easily handled by a steam shovel is to fire large charges of black powder and dynamite in alternate rows of holes. * Figs 15 and 16 show two typical blasts, Fig. 16 Line of Bcrck Break West Face *z> ^t East Face Face of Cut, East Fig. 15. Fig. 16. being the last blast fired when there were two faces. The holes were all drilled 24 ft. deep with a well driller, the bit being 3 ins. in diameter at the bottom of the hole. The holes * See page 92 for the cost of drilling in this sandstone. 150 ROCK EXCAVATION METHODS AND COST. marked "kegs" were loaded with the number of 25-lb. kegs of black powder given in the diagrams, after springing with dynamite. In springing each hole in Fig. 16, 15 sticks (ij4 x 8-in. size) were first fired, then 40 sticks, then 80 sticks and finally 130 sticks, a total of 265 sticks, or about 132 Ibs. of 40 per cent, dynamite per hole for springing. The holes marked "boxes" were loaded straight (without springing) to within 4 ft. of the top, each hole containing as many 5O-lb. boxes of 40 per cent, as indicated by the figures in the diagrams. In making a blast the dynamite and black powder were fired together, the theory being that the black powder would lift the rock, while the dynamite would shatter it. The results were excellent. The blast shown in Fig. 15 broke the rock up for 20 ft. back of the last row of holes; and, in making this blast, about 800 Ibs. of dynamite were used in springing the six holes, beside the 1,100 Ibs. of dynamite used in the blast itself ; 6,000 Ibs. of black powder were also used in this blast. The amount of rock within the boundary lines of the outer holes, to a depth of 24 ft., was about 2,100 cu. yds. ; and it was 2,700 cu. yds. within the boundary lines of the diagram back to the "line of back break." For the blast shown in Fig. 16 there were used i, 600 Ibs. of dynamite in springing the holes, 1,000 Ibs. of dynamite in the blast and 9,425 Ibs. of black powder in the blast. The amount of rock within the boundary lines of the diagram (to depth of 24 ft.) was more than 2,400 cu. yds. The rock was excavated for 2 or 3 ft. outside the boundary' lines. Large Chamber Blasts. We have seen how by springing a drill hole a small chamber can be made so as to receive a com- paratively large charge of explosive, and thus reduce the number of feet of drill hole per cubic yard of rock thrown down. This method may be carried out on a much larger scale by driving a small tunnel or sinking a shaft at the end of which chambers are prepared to receive a great charge of explosive. In this way a mountain of rock .may be broken METHODS OF BLASTING. 151 down at one shot, with a great saving in labor and powder. This method of chamber blasting is particularly economic in breaking down banks of hardpan for removal either by steam shovels or by hydraulicking. Unfortunately there is not a great deal in print relative to chamber blasting, but by search- ing I have found enough to give a good idea of the methods and an approximate idea of the size of charges used. Writ- ers without exception fail to state how much "block holing" was necessary to reduce the chamber-blasted rock to sizes that can be handled by derricks or that will pass through crushers. The following abstracts of articles on chamber blasting contain valuable information : In Engineering News, May 17, 1900, "W. M." describes "the second largest blast in the history of high explosives," fired Dec. 18, 1899, at West Beaver Creek, Col., by the Pike's Peak Power Co., for the building of a rock-fill dam requir- Fig. 17. ing 42,000 cu. yds. of rock. A granite "butte" or cone of rock was selected and a tunnel run into it 75 ft. below its apex. The tunnel was 135 ft. long, and had several bends in it, Fig. 17, so as to render blowing out of the charge im- possible. Cross drifts were run 35 ft. each way from the end of the tunnel. In these cross drifts were charged 32,000 Ibs. of black powder and 144 Ibs. of dynamite, distributed as 152 ROCK EXCAVATION METHODS AND COST. shown, and packed solid with bulkheads, b, of sacks of powder. The remaining part of the T was filled with rock and earth, except along one wall where 3,000 Ibs. of powder were placed in bags, E. Firing holes, d, 36 in number and 5 ft. deep, containing 4 Ibs. of dynamite each, with 3 electric exploders each, were connected in series, making three cir- cuits, so that in case one circuit was found to be open another would be available. The main tunnel was tamped solid with rock and earth, timber bulkheads being placed at c. The firing station was 3,000 ft. away. The explosion opened a crater 72 ft. deep and 150 ft. wide, breaking 110,000 cu. yds. of rock, or 80 per cent, of the rock above the tunnel level. A tunnel through the rim of the crater gave access to the broken rock. Mr. R. M. Jones was the engineer of the company. Mr. W. R. Russel is authority for the following data on chamber blasting for a rock-fill dam at Otay, Cal. : The rock was a porphyry, easily broken, but very hard to drill. Quarrying was begun by drilling holes by hand 12 to 20 ft. deep, but this was found to be too slow and expensive, so it was decided to run a tunnel and make one large blast. This was done by driving a 4 x 55^-ft. drift 50 ft. and then branch- ing so as to form a Y. The drift was large enough so that double-hand drilling could be used. The ends of the Y were enlarged to form powder chambers. The chamber on the right held 4,000 Ibs. of Judson powder; the one on the left held 8,000 Ibs. A 5O-lb. box of dynamite was placed in each chamber. The drift was completely packed with earth and sand. This blast threw down about 50,000 cu. yds. of rock, at a cost of 3.6 cts. per cu. yd. The cost was : 86-ft. drift $645 12,000 Ibs. Judson 960 Charging 75 Total $1,680 METHODS OF BLASTING. 153 Part of these 50,000 cu. yds. was further broken up by firing powder in the seams, making a total cost of 5 cts. per cu. yd. For the second blast a shaft was sunk to a depth of 115 ft. and about 85 ft. back from the quarry face. At a depth of 50 ft. two drifts were run in opposite directions for 25 ft., and a powder chamber was made at each end. At the bot- tom of the shaft two more drifts were run, one 35 ft., the other 30 ft. The total charge was 15 tons of powder, the greater part being in the bottom chambers. This blast was also very satisfactory. In both cases the electric wires were laid in i-in. pipes, which were covered by the sand tamp- ing, and the tamping was moistened to make it more effec- tive. After these large blasts there was never any stopping of work to fire, for the larger rocks were block holed and blasted at noon and at night. A derrick delivered the rock to a Lidgerwood cableway of 955 ft. span, capable of han- dling a lo-ton load. As high as 250 skip loads were handled in 10 hrs., the daily average being 200 loads. The time consumed in hoisting and lowering a skip was 20 per cent, of the time required to make the trip from the quarry to the dam. A large blast was fired March 3, 1898, by Carpenter Bros, to blow down an isolated mass of trap rock known as "In- dian Head," near Fort Washington on the Hudson River. Two tunnels were driven ; one near the water edge and 65 ft. deep ; the other about 60 ft. from the top and 80 ft. deep. The face was 200 ft. high. Two 25-ft. shafts were sunk from the upper tunnel, and drill holes besides. A charge of 3,000 Ibs. of dynamite was placed in one tunnel, and 4,000 Ibs. in the other ; and it was estimated that with the 7,000 Ibs. there were 350,000 tons of trap rock thrown down. Mr. O. Guttmann, in a paper read before the Inst. of C. E., gives data on chamber blasting on the Danube River. A spur of rock had a vertical face toward the river. A head- ing 3 ft. wide by 4 ft. high was driven in straight, and then 154 ROCK EXCAVATION METHODS AND COST. a chamber 6 x 6 x 6 ft. made at right angles to it. The chamber was charged and the heading closed by brick set in cement and by dry stone packing. At first carboazotine was used, consisting of 74 per cent, potassium nitrate, 12 per cent, sulphur, 8 per cent, soot and 6 per cent. bran. It was a low-grade explosive ; but, in one blast of 3.9 tons, 25,900 cu. yds. were thrown down where the breast was 60 ft. and the height 99 ft. The largest blast was in May, 1894, when 12 tons of second-grade dynamite (containing 45 per cent, blasting gelatine) in two chambers threw down 3 cu. yds. of rock for each pound of explosive, or practically the same as the carboazotine. The formula used for charging the chambers was : L = 3 (v 3 -f- 5h) q. In this L is the weight of charge in kilo- grams* ; v the line of latest resistance in meters ; h the height in meters of rock above, and q a coefficient depending on the explosive, being 0.22 for carboazotine. The term 5h may be dropped without sensible error. The formula then is almost identical with the formula: L = 4.19 r 3 c, used in harbor work at Fiume, where the ratio of height to line of least resistance was kept 3 : 2. Both these formulas give too high a charge, according to Guttmann. Mr. J. A. Wilson, in a paper before the Inst. of C. E., gives data on large blasts in New Zealand for harbor works. The stone was granite, gneiss and limestone used in large blocks. On an average i Ib. of dynamite dislodged 10 tons of stone. Separate charges were proportioned in the ratio of the cube of the least resistance, and this cube of the line of resistance was divided by 35 for dynamite, 36 for geleg- nite, 43 for gelatine dynamite, 50 for blasting gelatine and 12 for black powder. Charges of l /\. to i]/2 tons were found most effective (a 3-ton charge broke up the rock too much) ; but this kind of blasting requires a line of least resistance of less than 40 ft. One or more free ends in the quarry with a vertical face are preferable. The length of adit was made * Kilogram is equal to 2.2 Ibs, METHODS OF BLASTING. 155 nearly half the height overhead, and the chambers were a distance apart equal to 15 times the line of least resistance. In Engineering News, April 2, 1892, large blast firing at Brest, France, is briefly described. Galleries were excavated in the rock and charged with black powder, deposited in barrels covered by boards and tar paper to protect them from seepage water. The galleries were closed for a dis- tance of 13 ft. by stone laid in cement mortar, and then about 7 ft. of dry stone work followed by 7 ft. of stone masonry again. Firing was done by electricity. The amount of powder is not definitely stated, but the author speaks of 40,000 Ibs. as being the maximum blast; and in the blast described 104,000 cu. yds. were broken, not a single stone being thrown from the quarry which was in a residential district. At times the ratio was as low as i Ib. of powder to 11.7 cu. yds. of rock. The rules given below were fol- lowed : 1 i ) The distance between powder chambers should equal the thickness of rock above them. (2) The face left after a blast should be as nearly ver- tical as possible to facilitate further work. (3) With one powder chamber only, the distances from its center to the face of the quarry and to the top of the mass should be equal. The following data are given in Engineering News, Oct. 15, 1881: "A remarkable feat of railroad building has recently been undertaken from Portland to Dallas, Ore. The road will be 86 miles long. Much of the roadway must be blasted in the flinty face of lofty precipices, or drilled through no less unyielding rock. About 10 miles below Dallas is a bluff of basaltic rock rising 300 ft. from the Columbia River, along whose side the road is to pass. Men suspended by ropes 150 ft. over this wall drill and blast solid rock, their work being attended with the greatest danger. The largest blast on the line thus far has been at a point 10 miles above the Cas- 156 ROCK EXCAVATION METHODS AND COST. cades, a mass of rock 165 ft. high, 170 ft. wide and 70 ft. thick at the base, containing more than 40,600 cu. yds. being removed by the explosion of 10,000 Ibs. of Judson powder, equal in force to 20,000 Ibs. of black powder. The heaviest shot on this work was at 'J ac b's Ladder.' 1 At that point 420 cases, or 21,000 Ibs., of Judson powder moved 110,000 cu. yds. of solid rock. At 'Shell Rock' 56,000 cu. yds. of solid rock were moved with 10,000 Ibs. of Judson powder. ' In Engineering Record Aug. 10, 1895, Mr. F. A. Mahan tells of large blasts used at Genoa, Italy, in 1895. In lime- stone quarry, strata dipping 60 toward face, galleries were driven in the base at right angles to each other, and then the supporting pillars were all blown out at once, under- mining an area 100 x 300 ft., allowing the strata above to slide down. When the strata were twisted so they would not slide, shafts were sunk from the top. One charge of 11,440 Ibs. of dynamite produced a land slide of 260,000 cu. yds. of rock without damaging surrounding dwellings. A big blast in granite, at Long Cove, Me., is described briefly in the magazine, Stone (New York), 1896, p. 555, the data being as follows : A 4 x 4 shaft was sunk 64 ft., then two drifts were run, right and left, each being 27 ft. long; at the end of these drifts cross drifts 26 ft. long were driven, to receive the explosives. Four men were engaged about &y 2 mos. doing this work. Black powder was charged in waterproof canvas bags, the men working six days in complete darkness. In each of the two chambers on the west side, 1 80 kegs were charged ; and in each of the two cham- bers on the east side 185 kegs were charged, making all told 730 kegs of 25 Ibs. each, or 18,250 Ibs. Thirty-two dyna- mite sticks, each primed with a cap, were fired to explode the powder. After the explosion the ledge was 50 ft. higher than before (lo-ton boulders were hurled 100 ft. verti- cally) and it was estimated that 1,000,000 tons of granite had been loosened. This appears to be altogether too high an estimate. METHODS OF BLASTING. 157 Blasting Hardpan. Hardpan, or cemented gravel, is usually exceedingly difficult to drill because of the "hard heads" or boulders scattered through the mass, and because of the clogging of the drill by the softer material encount- ered between the boulders or cobblestones. If there are no large boulders in the hardpan, but merely a mass of small pebbles imbedded in clay, or cemented with iron rust, a well-drilling machine can be used to great advantage. The holes drilled by the well driller should be enlarged by spring- ing them with dynamite and then charged with black powder or Judson powder. Dynamite is not effective for breaking down a face of hardpan, because it gives a sudden blow that makes a chamber or pot hole and does not heave the mass of hardpan as does a slower explosive. Joveite, which strikes a blow of great power, but with less suddenness than dynamite, has been used with economy for blasting hardpan for ballast purposes at Cohocton, on the line of the D., L. & W. Railroad. The holes were driven about 7 ft. deep, horizontally into the bank (not vertically), crow- bars, post-hole diggers and spoon shovels being used in dig- ging the holes which were about 8 ins. diam. The holes were spaced about 10 ft. apart, charged with 4 Ibs. of Joveite in each hole and well tamped. This method of digging hori- zontal post holes in the face of a gravel bank is one well worthy of remembrance. On the Chicago Drainage Canal (Chapter XIII.), small tunnels about 2 or 3 ft. in diameter were run into the face of the hardpan. If a large boulder was encountered the tunnel was diverted so as to pass to one side of it. These tunnels were driven at the base of an i8-ft. face, and about 1 8 ft. center to center. The late Prof. Thomas Eggleston, of Columbia Univer- sity, is authority for the following data on bank blasting in California. While the blasting was done for the purpose of breaking up cemented gravel for hydraulicking, it is evi- 158 ROCK EXCAVATION METHODS AND COST. dent that the same methods are applicable in blasting hard- pan for steam shovel work: Bankblasting was introduced by J. F. Pierce in 1860, near Smartsville, Cal. Previously the banks had been broken down by undermining with picks, not infrequently burying the laborers. When very hard cemented strata make shaft sinking difficult, then tunnels are driven ; but when the bank is not very high, small shafts are usually sunk and enlarged in the form of a bottle at the bottom to* receive the powder. When a drift, or tunnel, is driven, the main drift has a drift at its end forming a T. The end drift is about half as long as the main drift. Sometimes a cross drift is run at the middle of the main drift, and has a length about one- third the length of the main drift. The sum of the lengths of all the cross drifts should be about equal to the length of the main drift. The drifts are made as small as the men can work in, generally 3 x 4 ft. The length of the main drift is usually I to ij^ times the height of the bank to be blasted, if the bank is a low one ; but for very high banks its length is about 24 the height of the bank. When the bank is 80 to 120 ft. high the main drift is made about as long as the bank is high. For such a drift about 600 (25 Ib.) kegs of powder are used, 400 kegs being placed in the cross drifts at the end and 200 kegs in the cross drifts at the middle. In blasting very high banks it has been found wise to run short main drifts connected with cross drifts parallel with the face of the bank ; then to charge these cross-drifts and blow out the gravel between the cross drifts and the face of the bank, thus allowing the bank above to fall and break it- self by its own weight. In bank blasting with black powder it is generally calculated that i Ib. of black powder will break 2 to 3 cu. yds. of gravel. It is always better to use too much rather than too little powder, for too little may result in the loss of the entire charge. At the Enterprise Mine 1,700 (25-lb.) kegs were fired at one time in a bank 250 ft. high. In 1875 a blast of 17,500 Ibs. of powder was fired at the METHODS OF BLASTING. 159 Paragon claim to break a bank 150 ft. high. The drifts had a total length of 325 ft., in the form of a T. The main drift was no ft. long, the cross drift on the right side was 70 ft. long and had at its end another 55-ft. drift parallel with the main drift. The cross drift on the left side was 60 ft. long, and at its end had another drift 30 ft. long. The mouth of the main drift was tamped 75 ft. from the end, and the cross drifts were tamped 10 ft. each way from the main drift, which, with the width of the drift, made 100 ft. of tamping. A large amount of open space was left in the L drifts for the expansion of the gases. The electric battery was 450 ft. from the mouth of the tunnel, and the total length of wire was 1,500 ft. The running of the drift cost $300, and the explosives cost $2,700. A blast of 50,000 Ibs. of black powder was fired at the Blue Point Gravel Mine in 1870 that lifted 150,000 cu. yds. (i Ib. to 3 cu. yds.) of gravel vertically a distance of 6 to 10 ft. The main drift (3 x 4 ft.) was 275 ft. long. On the left there were six side drifts, each 120 ft. long, the first one being 75 ft. from the mouth of the main drift. On the right there were six side drifts, each 80 ft. long. On the first drift to the right was a drift 15 ft. long parallel with the main drift. The powder was equally distributed through the drifts, and was fired by electricity from ten different points. In 1875, at the Dardenelles Mine, 36,000 Ibs. of Judson powder broke up 500,000 cu. yds. of cement gravel a ratio of i Ib. to 14 cu. yds. although Judson powder is commonly regarded by bank blasters as being twice as effective as black powder pound for pound. The face of the bank was 175 ft. high and 1,000 ft. long. Into this face five parallel drifts were run, across each of which two or more cross drifts were cut at right angles. The total length of drifts was 1,200 ft. The powder was charged in 28 lots of 1,000 to 2,500 Ibs., in each of which were placed three electric ex- ploders. 160 ROCK EXCAVATION METHODS AND COST. In 1881 at the Blue Tent Mine 43,000 Ibs. of black powder were fired under a bank 200 ft. high. In 1872, at the Harriman and Taylor claim, 3,500 Ibs. of dynamite broke down 200,000 cu. yds. of gravel, a ratio of I Ib. to 57 cu. yds. This seems to be a very high ratio, for Prof. Eggleston tells of 2,500 Ibs. of dynamite loosening 75,000 to 100,000 cu. yds., or I Ib. to 30 or 40 cu. yds., and adds that i Ib. of dynamite is as effective as 5 or 6 Ibs. of black powder, which, however, does not accord with the data of the blasts cited by him. While dynamite in small charges in drill holes is not effective for bank blasting, as I have had occasion to ascertain by test more than once, it appears to have been very effective when fired in drifts which were undoubtedly not packed solid with tamping, but in which large air spaces were left. Blasting Piles and Stumps. In Engineering News April 16, 1903, I have given data on pile blasting based upon methods that I used in removing several hundred white oak piles from the bed of the Chemung River, New York. The piles had been sawed off at low water level, when the river was "waist deep." With a ship auger a hole was bored down the heart of the pile a distance of 4 or 5 ft., and then 3 or 4 sticks ( l / 2 Ib. each) of 40 per cent, dynamite were placed in the hole, tamped with water and fired. The result was merely to splinter the oak into whipcords. After some further experimenting I found that two l / 2 Ib. sticks of 70 per cent, dynamite and one stick of 40 per cent, dynamite in each hole would cut the largest pile off below the bed of the river and hurl the top 50 to 100 ft. up into the air. Ship augers boring a hole \y 2 in. in diameter and 4^ ft. deep were used. One laborer bored 7 such holes per ic-hr. day, at a cost of 21 cts. per pile for boring; i Ib. of 70 per cent, dynamite at 20 cts. a Ib., and l / 2 Ib. of 40 per cent, at 15 cts. a Ib., made the cost of powder 28 cts. per pile. To this was added 5 ft. of fuse costing 3 cts., and a cap, I ct., making a total cost of 55 cts. per pile for boring and explosives. Two METHODS OF BLASTING. 161 men would load and fire 100 holes a day, using water tamp- ing. Once in a while a very tough pile would resist the dynamite, leaving a splintered snag. Mr. G. W. Stadly, in a letter commenting upon the method of pile blasting, gives the following: It was neces- sary to remove the piles used for falsework in a river. Rings that would just slip over a pile were made of telegraph wire. On each ring were fastened three half-sticks of 40 per cent, dynamite in separate places, and an electric cap placed in each stick. The rings were dropped over the piles to the bottom of the river, after attaching the electric wires, and, upon firing, each pile was cut off clean, without splintering. It is probable that the piles were of some soft wood like pine or spruce. Eissler states that a tree stump 30 ins. diam. was sawed off at the surface of a river, and three vertical holes (iy 2 in.) were bored with augers to depths of 4^, 8 and 8^ ft., requiring 3 hrs. for the short hole and 4^2 hrs. for each of the others. A charge of I Ib. of dynamite was fired in each hole. Stumps may be blasted out either with dynamite or with black powder. A hole is bored in the earth until the end of the hole is directly under the center of the stump. If the soil is clay, an earth auger may be used, or an iron bar may be churned or driven down with hammers. If the soil is dry sand, the hole will fill up as soon as the drill is with- drawn unless some precaution is taken. I have found a neat way to hold the sand is to saturate it with water around the bore hole. This may be done by using a gas pipe for the drill. Drive the pipe down a little way and pour water in at the top, and repeat. If holes are drilled in the sides of the pipe near its lower end the water will run out and saturate the sand, so that when the pipe is withdrawn the hole will remain open. For small stumps half a stick to a stick of 40 per cent, dynamite, well tamped, will serve. In blasting stumps 2 to 8 ft. in diameter, the hole may be sprung (unless in dry sand) by firing a small charge of dynamite, i62 ROCK EXCAVATION METHODS AND COST. and the chamber so formed loaded with black powder In this way a keg (25 Ibs.) of black powder will throw out the stump of a 6 ft. fir tree. Judson powder is very effective for large stumps. In heavy soils place the hole so that the charge of explosive will be close to the roots; but in light soils the powder should be buried deeper. Where the roots spread so as to cover a large area the charge must be placed deeper. In some stumps, such as second growth chestnut, the rotten stump of the first growth lies directly beneath the new tree ; in which case the dynamite will mere- ly scatter the old punk and not blow out the new stump. If a large flat stone is shoved under the new stump, between the roots, a stick of dynamite laid upon it and earth packed over it, the explosion will be effective. Ice Blasting. To open a channel through solid ice, bore holes through the ice with augers, and suspend dynamite charges of ^2 lb. to 5 Ibs. each from ^2 ft. to 5 ft. under the ice. Solid fresh water ice, 3 ft. thick, has been broken in a circle 60 to 70 ft. in diameter by 4 Ibs. of dynamite. Rot- ten, salt water ice, 10 ins. thick, has been broken in a circle 20 ft. diam. by y 2 lb. of dynamite exploded i^ ft. under the ice. Experiments should be made increasing the size and depth of the charge until the maximum area is broken per pound of dynamite. Charges of 1-3 lb. of dynamite have been fired within 2 ft. of piling, clearing the ice from the piles without damaging them. Ice jams above bridges can often be broken up by firing charges of 5 to 25 Ibs. of dynamite. The foregoing data on ice blasting are given in a catalogue on Atlas Powder by the Repauno Chemical Co. Boulder Blasting. There are three ways of breaking up a boulder with explosives: (i) Block-holing; (2) mud- capping; and (3) undermining. Block-holing consists in drilling a shallow hole in the boulder and exploding a small charge of high power explosive in the hole. Mud-capping consists simply in firing some dynamite on top of the boul- der, after covering it with a shovelful of earth, preferably METHODS OF BLASTING. 163 wet clay. Undermining consists in boring a hole in the earth and firing a charge of dynamite or Joveite in the hole directly beneath the boulder. Block-holing is obviously the most effective way of using the explosive, and it is surpris- ing how small a charge of 75 per cent, dynamite in a block hole will break a huge granite boulder. The cost of drilling is greatly reduced wherever pneumatic plug drills (see page 189) are used. In the Homestake Mine plug drills have largely displaced hand drills for the purpose of block-holing chunks of rock too large to sledge economically. Mud-capping is very wasteful of powder, and should only be used where a few scattering boulders are to be broken. The "mud" tamping is obviously not sufficient to enable the explosive to do its best work. Undermining is more effec- tive than mud-capping, because the boulder then acts as its own tamping; but very often the earth beneath the boulder is such that boring in it is too expensive, or it may happen that the boulder rests upon rocks. For data on the cost of blasting boulders, see page 232. CHAPTER X. COST OF LOADING AND TRANSPORTING. Cost of Loading by Hand. Where a laborer has merely to pick up and cast one-man stone into a jaw crusher, I have had men average 34 cu. yds. of loose stone handled per man per lo-hr. shift, which is equivalent to about 20 cu. yds. of solid rock. This, I believe, marks the maximum that may be done, day in and day out, by a good worker, where the stone has scarcely to be lifted off the floor to toss it into the jaws. Every stone, however, was handled and not shoved or slid into the crusher. Going to the other extreme, where conditions are not favorable, where there are more or less delays at blasting, where there is some sledging and a little track laying, and where delays in getting cars are frequent, as in railway tunneling, one man will load about 3 cu. yds. of solid rock per shift (the range being from 2 to 5 cu. yds., as given in Chapter XVI. ). On the Chicago Canal (see page 262) the average out- put per man per lo-hr. shift was about 7 cu. yds. loaded into dump cars, and this included some sledging. The average per man loading into the low skips used on the cableways, involving very little sledging, was about 10 cu. yds. of solid rock per man per lo-hr. shift. The best day's record was 16.6 cu. yds. per man loading into skips. In loading cars about 5 men out of the force of 36 loaders were kept busy sledging the rock; but with the cableways not only was it easier to roll large rocks into the skips (or "scale pans"), but very large rocks were lifted with grab hooks and chains and carried to the dump without sledging. In loading wagons with stone easily lifted by one man, the wagon having high sides, I have found that a man will readily average 10 cu. yds. solid, which is equivalent to 17 164 COST OF LOADING AND TRANSPORTING. 165 cu. yds. loose measure per day of 10 hrs. The same man will throw the stone out of the wagon twice as fast as he will load it, and this does not mean dumping the wagon, but handling each stone separately. In loading a wagon having a stone-rack, and no sides, two men, passing stone up to the driver who cords the stone on the rack, will load i cu. yd. solid stone in 13 mins. when working rapidly, but this is too high an average to be maintained steadily for a full day. A driver will unload I cu. yd. solid (or 1.7 cu. yd. loose) from such a stone-rack, by rolling the stone off, in 7 mins. if he hurries, but he may take 20 mins. if he loafs. A man will readily load a wheelbarrow with stone already sledged and ready for the crusher at the rate of 12 cu. yds. solid (or 21 cu. yds. loose) in 10 hrs. Croes is authority for the statement that on Boyd's Cor- ner Dam rough rubble stone was loaded onto wagons at the rate of 13 cu. yds. per man in 10 hrs., which is equiva- lent to 1 1^2 cts. per cu. yd., wages being 15 cts. per hr. The cut stone for this dam, during the years 1868-1869, cost about 30 cts. per cu. yd. to load on stone trucks, but in the year 1870 the cost was reduced to 13 cts. per cu. yd., wages being 15 cts. per hr., although it is not stated how this re- duction was effected. In quarrying mica schist for rough rubble in upper New York City, according to Mr. John J. Hopper the cost of loading wagons was 25 cts. per cu. yd., the rate of wages being 15 cts. per hr. In moving several hundred yards of stone for rip-rap I have had 5 laborers load, haul 500 ft. on a flat hand car and unload, at the rate of 10 cu. yds. solid measure (17 cu. yds. loose) in 9 hrs. per man. The stone was one and two-man stone, and was handled twice, once in loading and once in unloading. Cost of Handling Crushed Stone. In handling stone after it has been crushed to 2 y 2 -in. size, or smaller, a shovel is used, and the output of a man depends very largely upon 166 ROCK EXCAVATION METHODS AND COST. whether he is shoveling stone that lies upon smooth boards or whether it lies upon the ground. I have often had 6 good shovelers unload a canal boat holding 120 cu. yds. loose measure of crushed trap rock (2-in. size) in 9 hrs., but after breaking through to the floor the shoveling was compara- tively easy; this is 20 cu. yds. loose (or 12 cu. yds. solid) per man per day shoveled into skips. In shoveling from flat cars into wagons the same rate can be attained, but in shoveling from a hopper-bottom car, where there is at no time a smooth floor along which to force the shovel, an output of 14 cu. yds. loose measure (or 8 cu. yds. solid) is a fair lo-hr. day's work. In shoveling broken stone off the ground into wagons it is not safe to count upon much more than 12 cu. yds. loose measure (or 7 cu. yds. solid) per man per 10 hrs. A careful manager will, if possible, pro- vide a smooth platform, preferably faced with sheet iron, upon which to dump any stone that is to be re-handled by shovelers. Small stone, y^ in. or less in diameter, is easily penetrated by a shovel and need not be dumped upon a plat- form. A chamshell bucket operated by a locomotive crane is doubtless the most economic method of loading broken stone from cars or stock piles, where the quantity to be handled warrants the installation. Cost of Handling with a Derrick. Where crushed stone must be handled with a derrick, as in unloading boats, I have found the following- to be about the best that can be done per day : Per day. 6 shovelers, at $1.50 $9.00 1 hooker on 1.50 2 tagmen 3.00 I dumpman 1.50 i water boy i.oo I team on derrick 3.50 I foreman 3.00 120 cu. yds. (loose) at 19 cts. = $22.50 COST OF LOADING AND TRANSPORTING. 167 It commonly costs about 25 cts. per cu. yd. (loose meas- ure) to unload a boat of broken stone using skips holding 1 8 cu. ft. each, and a team on the derrick for raising them. Where any great amount of such work is to be done, how- ever, a hoisting engine and a derrick provided with a bull- wheel should be used. The following, from my note book, shows the cost of unloading flat cars containing broken stone (2-in. size), using a derrick with a bull- wheel for "slewing" the boom : 5 shovelers, at $1.50 $7-5o i dumpman 1.50 i engineman 2.50 y 2 ton coal at $3 1.50 100 cu. yds. (loose) at 13 cts. = $13.00 In this case a stiff-leg derrick, 4O-ft. boom, with a bull- wheel, operated by a double cylinder (?x 10) engine, han- dled self-righting steel buckets holding 20 cu. ft. each. Water for the engine was delivered in a pipe. The engineman was the foreman. In neither of the two cases just cited is the cost of install- ing the derrick included, nor is the interest and depreciation of plant included. It takes 6 men and a foreman one day to dismantle and move a stiff-leg derrick a short distance (100 or 200 ft.), and one more day to set it up again. This includes moving the engine and the stones used to hold the stiff legs down ; and it applies to a slow gang of workmen. A guy derrick with a 50 or 6o-ft. boom swung by a bull- wheel and a hoisting engine will often prove the cheapest device for loading cars with blasted rock. If the derrick is handling skips loaded with stone, the following is a fair average of the time elements in handling each skip load: Changing from empty to loaded skip 35 sees. Swinging (half circle) 20 168 ROCK EXCAVATION METHODS AND COST. Dumping skip 15 sees. Swing back 20 " Total 90 " If there were no delays, it would be possible to handle 400 skip loads in 10 hrs. Usually, however, the loaders will cause more or less delay, so that it is safer to count upon what they will average rather than upon what the derrick can do. One derrick cannot serve a very long face, and the number of men that can be worked to advantage in a given space is always limited; hence I repeat that with a good derrick provided with a bull-wheel the derrick can ordi- narily handle more stone than can be delivered to it by the men. The economic size of the skip load is entirely de- pendent upon the size of the hoisting engine, but a com- mon size skip measures 5 x 6 ft. x 14 ins. deep. Where much work is to be done a contractor should never try to get along with a derrick not provided with a bull-wheel for "slewing" the boom, for the wages of two tagmen would soon pay for a new outfit. Cost of Loading with Steam Shovels. A contractor who has never had experience in handling hard rock with steam shovels is almost certain to overestimate the probable out- put of a shovel loading rock. This is due very largely to the common tendency to think of all rock as being a ma- terial that differs only to a moderate degree in hardness. Then again perhaps the frequently published accounts of steam shovels used to load iron ore have had a tendency to mislead the inexperienced man. The iron ore of the Messaba Range, for example, is in reality a material that often re- quires no blasting and may be dug out of the bank with a powerful steam shovel using a small dipper. It should not be classed as a rock, but rather as a weak shale, so far as co- hesive strength is concerned. A soft shale that can be dug without blasting is just as much a rock as the toughest granite. Yet when it comes COST OF LOADING AND TRANSPORTING. 169 to loading rock with a steam shovel there is all the difference imaginable between shales and granites. Practically all printed records of shovels working in rock refer to shale, hardpan and soft iron ore. The only printed records of shovel output in tough rock that blasts out in large chunks are, so far as I know, the records kept by the engineers on one section of the Chicago Drainage Canal. I have given these records in full on page 265. Two 55-ton shovels, each working two lo-hr. shifts a day for four months, averaged 296 cu. yds. of solid rock (limestone) per shovel per shift loaded into cars, although it is stated that one day one of the shovels loaded 600 cu. yds. of rock in 10 hrs. The lime- stone on the Chicago Canal did not break up into small pieces upon blasting (a condition that is essential to eco- nomic steam shovel work in rock), but it came out in large chunks, much of which had to be lifted with chains, instead of being scooped up by the dipper. When each separate rock must be "chained out" in this way, a steam shovel is really no better than a derrick, and is, in fact, not so good. On a large contract near New York City, where the rock is a tough mica schist that breaks out in large chunks even with close spacing of holes, a 65-ton shovel with a 2^4-cu. yd. dipper averaged for several weeks about 280 cu. yds. of solid rock loaded on to cars. Part of this rock was loaded with the dipper and part was chained. Four men in the pit would fasten a chain around a large rock and throw the hook of the chain over one of the dipper teeth. The shovel would then deliver the rock to the car where a man un- hooked the chain. The time required for these four pit men to fasten the chain around a rock ranged from 1-3 min. to 2^4 mins., and on the average was about I min. The operation of swinging the dipper both ways and unhooking the rock averaged about 50 sees. Thus a rock every 2 mins. was averaged when working steadily; but delays due to shipping of chains, etc., would bring the average down to about one rock every 2^2 mins., or about 240 rocks in 10 i;o ROCK EXCAVATION METHODS AND COST. hrs. Each rock did not average much to exceed ^4 cu - yd., since the rock broke out in long flat slabs too long to enter the dipper, although much smaller in cubic contents than the dipper capacity. One of the features that should not be lost sight of in such work is the necessity of close spacing of drill holes in order to break up the rock to sizes such that at least a part of the chunks will enter the dipper. In this case the holes were spaced about 4^2 ft. apart. The fore- man of this shovel work certainly did not handle rock with the chain as fast as could have been done, for he should have provided an extra chain which the men could have been fastening to another rock while the shovel was unloading into the car. On the Jerome Park Reservoir excavation in New York City the rock is also a tough mica schist that blasts out in slabs even with heavy blasting. I am informed by Mr. R. C. Hunt, manager for Mr. John B. McDonald, contractor, that their 7o-ton shovels loaded only 300 cu. yds. of solid rock per lo-hr. shift. Mr. Hunt says: This was in the gneiss rock (mica-schist) of this vicinity. The fibrous nature of Manhattan and adjacent rocks causes it to break in such large and awkwark shapes that the shovel cannot do itself justice. I therefore abandoned the use of shovels in the rock cuts and find that I can handle the rock with derricks more economically. This statement agrees very closely with my own observa- tion of other contract work on Manhattan, as above re- corded. At the times of my visits to the Jerome Park work the holes were being drilled as follows : The face was 35 ft. high, and three rows of vertical holes were put down 25 ft., the rows of holes being 5 ft. apart and the holes in each row 7^2 ft. apart. A row of nearly horizontal holes was drilled 35 ft. below the top of the face, the holes being 5 ft. apart. All holes were loaded with dynamite and fired to- gether. The five shovels were loading on to standard gauge flat cars which were unloaded at the dump with a Lidger- wood plow and hoisting engine ; the cuts were side cuts. In thorough cut work on the Wabash Railroad, one 42- COST OF LOADING AND TRANSPORTING. 171 ton shovel loaded 240 cu. yds. of sandstone (solid measure) into dump cars in 10 hrs., as an average of a year's work ; but about 10 per cent, of the working time was lost in break- downs, etc. In shale, or any friable rock that breaks up into pieces that readily enter the dipper, the output of a steam shovel is far greater than in hard rock such as I have been citing. Through the kindness of Mr. George Nauman, assistant en- gineer, Pennsylvania Railroad, I am able to give the out- put of several shovels working more than a year, in shale near Enola, Pa. Each shovel worked two lo-hr. shifts per day, six days in the week. In cut No. I there were nearly 2,000,000 cu. yds., of which 85 per cent, was rock. Of this rock a little was very hard limestone, some was blue shale nearly as hard, and most of it was red shale, somewhat soft- er. Excluding the first two months, the average output of each shovel per month of double-shift work was nearly 31,000 cu. yds., equivalent to 15,500 cu. yds. single-shift work. There were, on an average, four shovels at work, averaging 60 tons weight per shovel. The best month's output was 47,300 cu. yds. per shovel in August, 1903, and the poorest month (after work was well started) was 20,800 cu. yds. per shovel in February, 1904, working double shifts. In cut No. 2 there were 1,130,000 cu. yds. of red shale, and while the monthly output per shovel was some- what less than in cut No. I, the digging was somewhat bet- ter. Three shovels were engaged 13 months, and each aver- aged 29,500 cu. yds. per month of double-shift work, equiva- lent to 14,750 cu. yds. of single-shift work. The average weight of each shovel was 60 tons. The best month's work was December, 1903, in which each shovel averaged 41,480 cu. yds. working double-shifts ; the poorest month was Jan- uary, 1904, in which each shovel averaged 23,850 cu. yds. The Allison dump cars used in this work have a capacity of about 4 cu. yds. struck measure ; but, although heaped, the average car holds only 2.5 cu. yds. of shale measured in 172 ROCK EXCAVATION METHODS AND COST. place. The cuts were all side cuts. I spent considerable time in studying the excavation work being done during 1903 between Pittsburg and Philadelphia. Just west of Harris- burg there were 13 steam shovels at work removing some 4,000,000 cu. yds. (mostly shale) for the new gravity yards of the Pennsylvania Railroad. For the most part the cuts were side-hill cuts, and the grades of the temporary tracks were so level that a "dinkey" readily hauled a train of 10 cars, each holding 2.5 cu. yds. of shale, place measure. Each shovel was served by from two to six trains of cars, de- pending upon the length of haul, and there were few delays in waiting for cars a vital point in securing economic re- sults. I found that the night shifts loaded about 20 per cent, less material than the day shifts. The crew serving each shovel consisted of 6 pitmen, I pit boss, I dipperman, I craveman, I fireman, 3 locomotive engineers, 3 trainmen, i switchman, 12 dumpmen and i dump boss. There were, besides, about 12 trackmen to each shovel grading new tracks, building temporary trestles, shifting track, etc. Most of the drilling of blast holes, which I have described in Chapter V., was done with well drillers. The shale broke up well upon blasting, often looking like a mass of chips. About 550 cu. yds. of shale loaded per lo-hr. shift was averaged by each 6o-ton shovel, including all delays, work- ing in side hill cuts averaging about 24 ft. deep. I am indebted to Mr. T. S. Bullock, President and General Manager, Sierra Railway Co., of California, for the follow- ing data: This company has two 43-ton Marion steam shovels with iJ/2-yd. dippers. One of these shovels worked from April i, 1903, to April i, 1904, in slate rock, all of which had to be blasted. In 300 working days of 10 hrs. each this shovel loaded 199,000 cu. yds. into small horse cars, which is equivalent to 663 cu. yds. per shift. Had large cars been used the output would probably have been 15 to 20 per cent, greater. There were days when 800 to 900 cu. yds. were loaded, and at other times there were de- COST OF LOADING AND TRANSPORTING. 173 lays in waiting for cars, when only 400 or 500 cu. yds. were loaded. This is an excellent record for a year's work. I am indebted to Mr. Daniel J. Hauer for the following information: With a 65-ton shovel, provided with a rock dipper (shallow and broad) having a capacity of 2^ cu. yds., the output for four months was 15,000 cu. yds. per month, working two lo-hr. shifts per day. The drill holes were 35 to 50 ft. deep, and the rock was granite and gneiss, somewhat disintegrated in places. The drilling was done by hand with churn drills, taking 6 men to pull a drill. The crews were as follows: 6 men, pit crew 8 men, drill crew i drill foreman 1 8 men, dump crew ' i dump foreman 6 men, extra crew i foreman. The "extra crew" at times worked on the dump or helped the drilling crew, and two men were used to run a steam drill (receiving steam from the shovel boiler) in drilling block holes. The cost of repairs to the shovel was very high. The total cost for wages (double shift work), supplies, ex- plosives, etc., was about $8,500 per month. The large num- ber of men on the dump was due to the fact that the rock was all rehandled in widening a fill. Cost of Steam Shovel Work in Iron Ore. I am indebted to Mr. Daniel King, General Manager Pinkney Mining Co., Pinkney, Tenn., for the following data : Two 43-ton shovels (i/^-yd. dippers), are worked in side cuts 25 ft. high. The ground is generally shaken up in front of the shovel, a 20- ft. hole, 12 to 16 ft. back of the face, being sprung with 2 to 5 sticks of dynamite and then shot with 2 to 4 kegs of powder. The ore, which varies from the consistency of hard pan to ordinary earth, is merely shaken up and not thrown down. The dump cars hold 77 cu. ft. level full and are generally 174 ROCK EXCAVATION METHODS AND COST. heaped full with dippers, so a car holds not less than 3 cu. yds. of loose material. Each shovel is served by two dinkey engines hauling trains of six cars. The wages paid per 10- hr. day are low, being as follows : i shovel engineer, $3 ; i craneman, $2; i fireman, $1.25; 4 pit laborers, $i each; 2 dinkey engineers, $1.75 each; i superintendent (to two shovels), $5. There are no firemen or brakemen on the trains. The grade from the shovels to 1 the dump is about 2 per cent, in favor of the load. The following was the cost of operating two shovels one month in 1903. Shovel No. i worked 171 hrs. ; No. 2 worked 161 hrs. : No. i. Excav. 5,513 carloads, wages $287.65 Transporting 5,513 carloads, 500 ft. haul (one way), wages 83.60 Drilling 272 ft. at 4 cts 10.88 Explosives 2 7-5 2 No. 2. Excav. 3,362 carloads, wages $243.01 Transporting 3,362 carloads, 1,500 ft. haul (one way), wages 60.13 Drilling 239 ft. at 4 cts 9.56 Explosives 27.80 Dumping, 8,875 carloads 142.27 Track work 267.60 Trackwork (nights) 75-^7 Blacksmith work 76.30 Repair " 1 10.23 Carpenter shop 37-7 Renewal and repair supplies J96-39 Coal for shovel No. i at $4.50 ton 77-3 " " " No. 2 " " " 72.70 Coal for 4 dinkeys 91.00 Iron 23.85 Lumber 37.39 Oil 25.27 Waste .QO Total for 8,875 carloads $1,984.92 COST OF LOADING AND TRANSPORTING. 175 When washed, these 8,875 carloads yielded 7,633 tons of ore. In 1902 during a month of 201 hrs. the two shovels dug 10,703 carloads, at the following cost: Excavating, wages $5334 J Hauling, wages 250.40 Drilling, 812 ft., at / cts 32.48 Explosives 97-37 Dumping *94-99 Blacksmith work 84.11 Carpenter " 56.40 Repair " 137.28 Track " 185.10 Extra (night) labor 73-3 Renewal and repair supplies 182.46 Fuel 247.40 Iron, $24.60 ; lumber, $29.23 53.83 Oil, $28.40 ; waste, $2.28 30.68 Total for 10,703 carloads $2,159.21 When washed these 10,703 carloads yielded 7,573 tons of ore. Wages of shovel crew are : I shovel engineer, $3 ; I crane- man, $2; i fireman, $1.25; 4 laborers at $i ; 2 dinkey en- gineers at $1.75; J/2 superintendant at $5. There were no firemen nor brakemen on the trains. Grade from shovel to dump, 2 per cent, in favor of loaded trains. The best day's work with one shovel was Jan. 30, 1903. The work was in a side-cut, 25 ft. high and cost as follows : Excavating (441 carloads), wages $12.75 Hauling (400 ft. one way), wages 3.50 Drilling 23 ft. at 4 cts 92 Explosives 1.66 Dumping 4.50 Trackwork 18.00 . Blacksmith work 3.08 176 ROCK EXCAVATION METHODS AND COST. Repair work 5.15 Carpenter work 3.00 Coal at $4.50 ton 5.45 Iron and lumber 3.00 Waste 83 Total for 441 carloads $61.84 When washed these 441 carloads yielded 450 tons of ore. For the sake of comparison the following hand work in this ore will be interesting : Loaders received 8 cts. per cu. yd. and earned $1.25 to $2 a day; common laborers received 10 cts. per hr. In a month of 235 working hours, with a haul of 800 ft. (one way), 600 ft. being a mule haul and 200 ft. by gravity, in a material not as hard as hardpan, and working to a face 16 ft. high, the cost was as follows : Digging 2,272 carloads = 4,544 cu. yds. . .$363.52 Hauling " , 800 ft. one way . . 67.89 Drilling 273 ft. at 4 cts. . . 10.92 Explosives 36-67 Dumping 32.59 Repair and trackwork 40.68 Blacksmith work 3.10 Iron, $2 ; lumber, $2.62 4.62 Oil, $2.75 ; waste, $0.18 2.93 Foreman ( i mo.) 62.50 Total for 2,272 carloads $625.42 When washed, these 2,272 carloads yielded 2,488 tons of ore. These cars were smaller than the cars hauled by the engines, and they held 2 cu. yds. of loose material. Cost by Wheelbarrows. A wheelbarrow load averages about 1 / 2B cu. yd. of solid rock. A man will load such a barrow in 2 mins., and will walk with it at a speed of 180 ft. per min. if he is lazy and to 250 ft. per min. if he is active; and he will lose % mm - each trip in dumping the COST OF LOADING AND TRANSPORTING. 177 barrow, fixing run planks, etc. Assuming a speed of 200 ft. per min. and wages 15 cts. per hour, the cost of loading, hauling and dumping is : Rule I. To a fixed cost of 18 cts. per cu. yd. of solid rock add 6% cts. per cu. yd. per 100 ft. of one-way haul from pit to dump.* Cost of Hauling in Carts and Wagons. Since a cubic yard of loose, broken stone weighs about as much as a cubic yard of earth measured in place ; and since, ordinarily, I cu. yd. of solid rock becomes 1.7 cu. yds. when broken, we may say that a team will haul about 60 per cent, as many cubic yards of solid rock per day as of earth. In other words, if the roads are such that I cu. yd. of packed (not loose) earth would make a fair wagon load for two horses, then 0.6 cu. yd. of solid rock would be a fair load. In my book on earth- work I have discussed in considerable detail the sizes of loads of earth that teams can haul, and it is only necessary to multiply the earth load as given there by 6 /io (or 60 per cent.) to find the equivalent load of solid rock. Another way to estimate loads is to use the ton of 2,000 Ibs. as the unit. Solid rock seldom weighs more than 2.2 tons per cu. yd. Over poor earth roads, with occasional steep pitches, a load of I ton is practically all that an ordinary team should be counted upon to haul, or less than l / 2 cu. yd. of solid rock. If the road is hard and level, a team will haul I cu. yd. of solid rock ; or one horse will haul l / 2 cu. yd. in a cart. If the road is a good macadam all the way, with no grades over 4 per cent., and no pulls through soft earth, a good team can haul about 1^/2 cu. yds. of solid rock, but these conditions are exceptional. In ordinary city and village work, and on level hauls over hard earth roads, assume I cu. yd. of solid rock as a load for two horses. A team travels * In this rule, and in the rules that follow, I have given not the lowest records of cost that I have, as will be seen by anyone who takes the pains to study this book well. I have preferred to give conservative estimates of cost in all the rules. It is never safe to estimate too closely before work has been actually begun; but once it is under way every cent per yard should be looked after with the greatest diligence. In a word, make your saving in your work and not in your preliminary estimate. i;8 ROCK EXCAVATION METHODS AND COST. 220 ft. per min., or 2,y 2 miles an hour, at a walk over ordi- nary earth roads, a little faster over good pavements and a little slower over soft roads, the variations from this average of 2*/2 miles an hour being seldom more than 20 per cent., making it about 2 miles an hour over poor roads to 3 miles an hour over the best macadamized roads. It is perfectly safe to say that a team can walk steadily for 8 hrs., averaging the speeds above given, going loaded and return- ing empty ; so if the shift is 10 hrs. long, and not over 2 hrs. are lost in loading and dumping, the team has 8 hrs. to travel, in which time it will cover 16 miles over poor earth roads, 24 miles over good macadamized roads and 20 miles over ordinary earth roads. If the hauls are short it may happen that so much time is lost in loading and dumping that the team has considerably less than 8 hrs. of actual walking time left. Each case must be considered by the con- tractor. As to the wagons used for hauling one and two-man stone, my own preference is for an ordinary wagon from which the box has been removed and replaced by a "stone rack." A stone rack is 3 ft. wide and 1 1 ft. long, its floor being 3-in. plank and its sides and ends nothing but 3 x 4-in. strips. This makes a "box" that is low and easily loaded, when necessary big stones being rolled up an inclined plank onto the wagon. It is also unloaded easily, large stones being simply rolled off without lifting. Where hauls are very short, and the stone all broken to one-man size, a patent dump wagon may be used advantageously ; but such a wagon always weighs much more than the common wagon with a stone rack, aside from the fact that a patent dump wagon is always harder to load. As above stated, a driver will un- load I cu. yd. solid measure (or 1.7 cu. yds. loose measure) of stone from a stone rack in 7 mins. if he is vigorous in his work. Certainly two men should never take more than 7 mins. Two men and the driver can readily load I cu. yd. onto a stone rack in 15 mins., no stone being heavier than COST OF LOADING AND TRANSPORTING. 179 two men can lift. Then if one man and the driver unload in 7 mins., we have 22 mins. team time lost in loading and unloading, which is equivalent to 12 cts. per cu. yd. (team and driver being worth 35 cts. an hour), 8 cts. being for lost team time loading and 4 cts. for lost time dumping. If, including rests, each laborer (exclusive of the driver), aver- ages jY-2 cu. yds. loaded in 10 hrs., and wages are 15 cts. an hour, we have 20 cts. per cu. yd. for loading. If one man, assisted by the driver of each team, does the unloading, the cost of his help need not exceed 3 cts. per cu. yd. We have, therefore, a total fixed cost of, 8 cts. lost team and driver time loading, plus 4 cts. ditto unloading, plus 20 cts. for labor loading, plus 3 cts. for helper unloading, making a total fixed cost of 35 cts. per cu. yd. of solid rock. Our rule for loading and hauling and dumping I cu. yd. of solid rock (2.2 tons) in wagons, under the above conditions, is: Rule II. To a fixed cost of 35 cts. for lost team time, and labor of loading and dumping, add 6 / 10 ct. per cu. yd. per 100 ft. of haul (one way) from quarry to dump, or 32 cts. per mile one way ; but if the roads are such that y 2 cu. yd. of solid rock (i.i tons) makes a load, to the 35 cts. fixed cost add i 2 / 10 cts. per cu. yd. per 100 ft. of one-way haul, or 64 cts. per mile. By using extra wagons, as should be done where the haul is so short that a team cannot be kept on the walk 8 hrs. ; or by using more men loading and un- loading, as should be done when the hauls are very short, the fixed cost can be reduced to 30 cts. per cu. yd. In railroad work one driver usually attends to two one- horse dump carts ; and as rock cuts are usually higher than the dump the haul is down hill, so that, considering the rough roads, big loads can be handled. By having 4 or 5 men to load each cart, there is about the same amount of lost team time per cu. yd. of rock as above assumed for loading wagons, or 8 cts. per cu. yd. ; the cost of dumping is about 2 cts., making a fixed cost for the two horses and driver of 10 cts. per cu. yd., to which add 20 cts. for loading to get i8o ROCK EXCAVATION METHODS AND COST. the total fixed cost for labor and teaming. With wages at 15 cts. per hr. for laborers and 35 cts. for a driver and two one-horse carts, the rule for loading and hauling by carts, l /4 cu. yd. of solid rock per cart, is : Rule III. To a fixed cost of 30 cts. per cu. yd. of solid rock add i 2 / 10 cts. per 100 ft. of one-way haul. Mr. Daniel Hauer states (see page 226) that he has found 1/3 cu. yd. of solid rock to be a fair average of the size of one-horse cart load on railroad work, but my own records show ^4 cu - yd- to have been an average, and I have preferred to err, if at all, on the conservative side. Where carts or wagons must be hauled up a steep, bad road, it will often pay to lay either a plank road, or to lay steel channel beams so as to form a trackway. This last method has been used with advantage where a hoisting en- gine was placed at the top of a long hill to relieve the teams of the work of hill climbing. A boy on a horse can readily drag the snatch rope back down the hill. In the far West it is customary for three or more teams to be hitched to a train of two or more wagons, and, when a steep hill is to be ascended, only one wagon is hauled up at a time. On long hauls this method could be used to advantage much oftener than it is in the East. Snatch teams are not used as often as they should be to enable large loads to be handled over bad spots in the road. Where the roads are fairly good all the year, traction engines are economic. For hauling cut stone in large blocks, "stone trucks" are used. A stone truck is a strong wagon provided with a plat- form which hangs below the hubs of the wheels, instead of above them, as in the ordinary wagon. Where large derricks are available at both ends of the haul, wagon boxes can be made so as to be lifted off by the derricks, both for loading and dumping the rock. Hauling on Stone-Boats. For moving large stones a short distance stone-boats or sleds are often used. A stone-boat is a flat platform, ordinarily about 2^2 x 4 ft., on wooden COST OF LOADING AND TRANSPORTING. 181 runners shod with iron. It possesses three advantages over a wheeled vehicle : First, it is so low that a large rock can be rolled by hand, or dragged by the team on to it; second, it cuts no ruts into wet ground, and, third, it can be dragged about in narrow places. Obviously a team cannot haul a very large load very, far on a stone-boat, but surprisingly large loads can be hauled a short distance if the team has long rests between loads. A team of horses weighing 2,400 Ibs. can exert a pull of about 1,000 Ibs. for a short time if they have a good earth foothold. The sliding friction of iron or wood on earth is about 50 per cent, the weight of the load that is being dragged ; hence a team is capable of dragging a stone-boat and load together weighing 2,000 Ibs. A team doing such heavy work could probably not average more than 2 hrs. of actual pulling per day. In stone-boat work, however, a stone weighing more than 1,100 Ibs. (y$ cu. yd. solid) is seldom handled. Where many such stones are to be hauled a considerable distance, as in boulder quarrying, I have found it an excellent plan to build "skid roads." A skid road is really a rough railroad without the rails, for it is made by partly bedding in the ground round sticks of unsawed timber, like ties for a railway track, 3 to 6 ft. apart. A stone boat with wooden runners, 8 to 12 ft. long, can be "skidded" or hauled along over these ties with surprising ease if the ties are kept well greased. Indeed, a team can thus pull a bigger load than with a wagon wherever there is not a well made road. Where growing timber is at hand a skid road may be made at less cost than grading a wagon road, and it possesses the inestimable value of being a good road even in wet weather. I have seen wagons that were dragged with difficulty through the mud when the load was less than y% cu. yd. of solid rock (550 Ibs.) ; and it often happens in the fall and spring of the year that % cu. yd. of solid rock is a big load for wagons traveling over earth roads badly rutted and muddy. In such cases a skid road can often be built to advantage. 182 ROCK EXCAVATION METHODS AND COST. Cost by Dump Cars. For a discussion of the tractive power of horses and the rolling resistance of cars, the reader is referred to my book on earthwork. On a level track a team will readily haul two dump cars loaded with 3 cu. yds. of solid rock over the ordinary narrow-gauge track with light rails. In railroad work the grade is usually in favor of the load from cut to fill, and it is safe to assume that one horse will haul two dump cars (i^-yd. body) loaded with y 2 cu. yd. solid rock in each car; with a well kept track slightly in favor of the load, but not so steep as to stall the horse returning with the empty cars, it is safe to count upon Y^ cu. yd. in each of the two cars. In a thorough cut the track is usually laid Y-fashion, the two branches of the Y being carried up close to the rock face. Two empty cars are left on one branch of the Y to be loaded while the two loaded cars are hauled away from the other branch. If the haul is short and only a few loaders are at work, only one car is hauled at a time. If the cut is wide enough, and it often is, I prefer to lay two parallel tracks and have two Y's, for in that way the loaders need not take so many steps to get a stone into a car, since there are four places at the face where cars may stand, instead of two. In estimating the cost of loading and hauling in cars, using horses or mules, assuming the rock to be broken up into sizes that one or two men can lift, it is never safe to count upon more than 7^2 cu. yds. solid rock loaded per man in 10 hrs., and often it will be wise to estimate on not more than 6 cu. yds. With wages at 15 cts. per hr., the load- ing costs 20 to 25 cts. per cu. yd. Assuming i cu. yd. of solid rock as a fair load for one horse to haul in cars ; as- suming 4 mins. lost time in changing from the empty to the loaded cars and in dumping ; assuming a speed of 200 ft. per min., and assuming wages of driver and one horse at 25 cts. per hr., we have I %o cts. per cu. yd. chargeable to lost time at pit and dump, plus J/ ct. per cu. yd. per 100 ft. of haul (measured one way). The cost of dumping is largely COST OF LOADING AND TRANSPORTING. 183 a matter of how many yards are delivered per day at the dump. However, with wages at 15 cts. an hour, the cost of dumping is seldom less than 2 cts., and it may run as high as 5 cts. per cu. yd. Assuming 5 cts. as a fair average of the combined cost of dumping and lost team time, and 20 cts. as the cost of loading by hand, we have : Rule III. For loading and hauling with dump cars, to a fixed cost of 25 cts. per cu. yd. of solid rock, add y 2 ct. per cu. yd. per 100 ft. of one-way haul. If the distance is great enough to warrant the use of a team of horses instead of one horse, the cost of hauling will be V 3 ct. per cu. yd. per 100 ft., if wages of team and driver are 35 cts. per cu. yd. I estimate the cost of track laying at $100 per mile, of wear and tear on ties at another $100, and of pulling up track at $50, making a total of $250 per mile, or $5 per 100 ft. of track. Dump cars can be estimated as costing about $50 each, 3O-lb. rails at $30 a ton and ties (6x6 ins. x 5 ft.) at 25 cts. each. CHAPTER XL QUARRYING STONE. General Considerations. In this chapter the quarrying of stone for masonry (other than concrete) will be discussed. Stone that is quarried and split with plug and feathers, or otherwise, to dimensions (ready for stone cutters to begin dressing the surface) is called dimension stone. If it is quar- ried out in rough slabs or blocks of irregular dimensions it is called rubble stone, or backing stone. In quarrying dimension stone the first step is to secure a working face in the quarry ; the next" step is usually to cut or blast a channel at each end of this face, so as to expose three free faces. Then it is possible, by wedging or blast- ing, to loosen a long block of stone which can be split into short blocks that can be handled by derricks. Where there is a good market for rubble stone, it is not customary to make end channels, but merely to shake up the rock for a short distance back of the face by light blasts, and, if it is a sedimentary rock, large irregular slabs can be barred and wedged out. These slabs can then be squared up by sledg- ing or by plug and feathering, or both. Obviously this method produces a very considerable amount of rubble stone, but it is the common method in small' dimension stone quarries. While in the first chapter attention was called to the joints that exist in stone, it is well to add certain facts to those al- ready given, for the art of quarrying is largely the art of taking advantage of joints and natural cleavage planes. Granite, which to the ordinary eye appears massive and without planes of natural cleavage, has in fact a "rift" clear- ly seen by the trained eye. Along this "rift" it may be split with comparative ease. At right angles or perpendicular to 184 QUARRYING STONE. 185 the "rift" in one direction are planes of cleavage, called the "grain," along which the stone splits with less ease; while at right angles to the "rift" in the other direction are planes of natural cleavage, called the "head," along which it is still possible to split the stone, but with less ease than along the "grain" or along the "rift." These three planes of cleavage are shown in Fig. 18. All sedimentary rocks have a "rift" which corresponds with the planes of stratification or beds ; but the trap rocks, like diabase, diorite, porphyry, etc., often have no rift at all, and are consequently unfit for use as di- mension stone, since when hammered or wedged they are apt to split, like glass, irregularly. ffift- rfl Grain H< The cost of quarrying stratified rocks, like sandstone and limestone, depends largely upon two factors: First, the thickness of the beds, and, second, the "dip" of the beds. The "dip" is the angle, or slope, that the bed makes with a horizontal plane. If the beds lie horizontally, just as when they were originally deposited in the primaeval sea, the stone is quarried out in successive layers ; and, as these layers usually vary in thickness, the quarryman, after the quarry has been well opened, can select a layer of thickness to suit the demand of any particular purchaser. If the beds dip at a steep slope into the earth, the quarryman must usually re- move thick-bedded and thin-bedded stone, all together, as he goes down ; and besides he must abandon his quarry, or resort to mining methods, before a very great depth has been reached, because it will not pay to remove the increas- ingly large amount of stripping. On the other hand, where i86 ROCK EXCAVATION METHODS AND COST. the beds dip at a high angle the quarryman can determine, by examining the exposed outcrop, what the thickness of each bed is, and can count with some certainty upon the character of each bed. Where the beds lie flat, the thin beds are usually on top, and thicker beds exist below ; but this is not always the case, and to determine the character of the deposit diamond drill cores should be obtained. If the beds of stratified rock are quite thin, the stone may be fit for flagstone, curbing, lintels, paving blocks, slope wall stone, basement masonry and the like ; but will of course be valueless for heavy, architectural masonry or for engineer- ing masonry where specifications call for thick courses. This simple fact is frequently overlooked by engineers in draw- ing masonry specifications, and they often call for thick- nesses of courses that either are not to be found in local quarries at all, or, if found, are quarried only at great ex- pense by first removing a lot of thin bedded stone overlying the thicker beds required. Times without number I have seen evidences of such ignorance of quarry products and quarrying costs that obvious as these facts seem I deem them worthy of emphasis. If the beds of stratified rock are thick- er than the courses of masonry specified, then the quarried blocks must be split at a cost that should never be overlooked by the quarryman or the contractor in estimating a fair price for his product. Thus it appears that there is a happy medium as regards the economic thickness of beds. Joints. All rocks, whether igneous or sedimentary, con- tain "joints," or seams that run through the natural beds. Often these "joints" are clearly visible, but at times the split may be so thin as to be invisible except to the expert eye. In stratified rock the "joints" as a rule are perpen- dicular to the planes of bedding, and are spaced quite regu- larly, as if a giant quarryman had struck the rock with a sledge at intervals, cracking it in vertical planes. The joints in stratified rock have, as a rule, two dominant trends, one set of joints being parallel with the "dip" ("dip or end QUARRYING STONE. 187 joints") and the other set at right angles, or parallel with the "strike" ("strike or back joints"). In granites and traps the "joints" occur at irregular in- tervals and often intersect at varying angles ;. nevertheless there are generally two sets of vertical joints intersecting approximately at right angles, and frequently there is a third set of horizontal or "bottom joints." If the joints are close together it will, of course, be impossible to quarry building blocks; though, on the other hand, the quarrying of stone to be crushed/ for concrete or macadam is greatly facilitated by numerous joints, as exemplified in the trap rocks of the Hudson River. Joints are usually quite conspicuous near the surface, due to the fact that changes of temperature have opened them, and solutions of iron salts passing through the joints have stained the rock. But wherever granite is found with numerous close joints in the surface beds, it may be inferred that similar joints exist in the lower beds even if they are invisible, and even if the blocks quar- ried from the lower beds appear solid. Merrill cites a granite quarry in which the stone at a depth of 25 ft. appeared to be perfectly solid, although above it was full of joints ; but upon polished blocks he was able to discover fine hairline joints which eventually would doubtless open up upon ex- posure. I would suggest that tests on the tensile strength of diamond drill cores would quickly prove the existence or non-existence of such joints. Where joints in granite run verically and at right angles to one another, as well as horizontally, the quarry is known as a "block quarry." Where there are practically no vertical joints, but where a series of nearly horizontal joints divides the granite into sheets or beds, the quarry is a "sheet quarry." The beds in sheet quarries are usually lenticular in shape, thin at the edges and thick in the middle. In such a quarry blocks 10 ft. thick and 309 ft. long have been loosened. Plug and Feathers. Before studying' the methods of i88 ROCK EXCAVATION METHODS AND COST. quarrying it is necessary to understand certain of the com- moner tools and machines. Among these the most impor- tant are the plug and feathers, shown in Fig. 19. These simple tools are used for splitting large blocks of stone into smaller blocks and for squaring up irregular stones. The plug is the wedge, and the feathers are merely two short pieces of half-round iron whose curved sides fit the sides of the drill hole, while their flat sides receive the thrust of Fig. 19 the plug. It is astonishing to see how thick a block of granite may be split with so small and simple a device. To split a block of granite, a row of holes about ^ or ^4 in - diam. and 2^2 to 5 ins. deep are drilled about 6 to 8 ins. apart. Then a pair of, feathers and a plug are placed in each hole, the plugs being driven home with light blows of a hammer until all are tight. Then each plug in succession is struck one or two blows, the quarryman telling by the ring of the metal under the blow whether the strain is prac- tically the same in each wedge. With plug holes only 5 ins. deep a block of granite 6 ft. thick can be split, leaving a face almost as flat as a board. For granite blocks 3 ft. thick, a hole 2.Y-2 or 3 ins. deep will suffice. Some limestones also break remarkably well with shallow plug holes, but marbles QUARRYING STONE. and sandstones as a rule require deep holes, although with some sandstones holes iJ/ ins. x 8 ins. will break a sheet 4 ft. thick, perfectly true, according to Saunders. In most sandstones, however, the holes are usually 1^4 to 2 ins. diam., and, as a general rule, of a depth equal to 2 /s the thickness of the stone. The holes are spaced 4 to 16 ins. apart. In some sandstones the plug holes must be drilled entirely through the stone to insure a true break. The plugs need not always be of the same length as the depth of the hole. Sometimes it is found desirable to alternate deep and shallow plug holes in the same row. In this case the lower half of the deep holes may be drilled with a smaller bit, so that the plugs in these holes will strain only the bottom half of the stone. For drilling plug holes there are three methods in com- mon use: (i) Drilling by hand; (2) drilling with a pneu- matic hammer, called a pneumatic plug drill; and (3) drill- ing with an ordinary rock drill mounted on a quarry bar. Since plug holes in granite are seldom more than 6 ins. deep (usually 3 ins.), either hand drilling or pneumatic plug drilling should be used ; but where deeper holes must be put down a rock drill on a quarry bar should be used. Cost of Plug Drilling by Hand. By timing a aumber of masons at work splitting granite blocks 24 to 30 ins. thick, I found that each man drilled each hole ( ^-in. diam. x 2^2 ins. deep) in a trifle less than 5 mins., by striking about 200 blows ; and it took about I min. for placing and striking each set of plug and feathers. Blocks 30 ins. long, with four plug holes, were drilled and split with the plugs and feath- ers in 24 mins., on an average. At this rate, a good work- man can drill and plug 80 holes in 8 hours. Cost of Pneumatic Plug Drilling. For drilling plug holes in granite certainly no tool is as economic as the pneumatic plug drill. Fig. 20 shows one of these drills at work on the Wachusett Dam granite quarry. It will be seen that horizontal as well as vertical holes can be drilled rapidly, igo ROCK EXCAVATION METHODS AND COST. which in itself is a distinct advantage over the quarry bar method. The plug drill shown in Fig. 20 does not rotate the bit automatically, which I consider a positive advantage since it simplifies the mechanism and reduces the wearing parts. The operator turns the bit with a wrench, which is such light work as to add little to his expenditure of energy. Fig. 20. The ordinary plug drill, according to the manufacturers, consumes 15 cu. ft. of free air per min. at 70 Ibs. pressure. At the Wachusett Dam I found that a workman averaged one hole. (Hj-in. diam. x 3 ins.) drilled in \y 2 mins., in- cluding the time of shifting from hole to hole, but not in- cluding the time of driving the plugs. About 250 plug holes QUARRYING STONE. igi are counted a fair day's work for a plug drill where the driller does not drive the plugs himself. Not only for plug hole drilling, but for block-holing, has the pneumatic drill a promising future. A portable, gaso- line-driven air compressor, such as is commonly used for running pneumatic riveters, would serve admirably for plug drilling purposes in quarries where a large compressed air plant is not already installed. The Quarry Bar. A quarry bar is a long bar mounted on four legs, and upon the bar the drill is mounted, so that the drill can be moved quickly from hole to hole along the bar, Fig. 21. or, as shown in Fig. 21, the stone in which the plug holes are being drilled can be moved on a truck. By having wheels with perforated holes (Fig. 21) the drill helper can move the truck, by means of a crow-bar, just far enough for drilling the next hole. It is stated in the Ingersoll-Ser- geant catalogue that in a granite a "Baby" drill on a quarry bar will drill a hole 3 or 4 ins. deep in y$ min., and it can be moved and started in another hole in less than y^ min., so that 100 ft. of hole are drilled in a day. The quarry bar is a device that should be used far oftener than it is; for example, wherever vertical drill holes aie spaced close together, as in shallow, open cuts, a long quarry 192 ROCK EXCAVATION METHODS AND COST. bar may be preferable to a tripod, because of the time saved in setting up. In trench work a quarry bar might, in many cases, be used to advantage with the bar spanning the trench. Broaching. In quarrying granite the quarry bar is used to some extent for broach channeling, which consists in drilling a row of holes close together like the holes in a postage stamp and then using a "broach," or chisel, to break down the rock between the holes. The wall left be- tween the holes is ^4 to 2 ins. thick, depending upon the hardness of the rock. The "broach" is, of course, not ro- tated like the ordinary drill bit. In the Ingersoll-Sergeant catalogue the following data are given as to average broach channeling work done per day by one drill on a quarry bar : In granite, 10 to 20 sq. ft.; in marble, 20 to 30; in lime- stone, 15 to 35 ; in sandstone, 20 to 40 sq. ft. Where it is necessary to excavate igneous rocks, like granite or schist, close up to large buildings whose founda- tions must not be disturbed, broach channeling is often specified. In this connection it is well to quote from Engineering Record, Feb. 7, 1903, a method of blasting close to a tall brick building without channeling. The rock excavation was 60 ft. deep, the rock being stratified in I to 4-ft. layers. A trench 10 ft. wide was taken out (lo-ft. lifts) parallel with the building. Along the face of the building a row of holes was drilled 18 ft. deep, holes being 6 to 8 ins. center to center. A second parallel row of holes was drilled 2 ft. away from the first row, the holes being 2 ft. apart and loaded lightly with 40 per cent, dynamite. The holes in the row next to the building were not charged, but the blast caused, the rock to crack along the line of these uncharged holes. The Gadder. The Ingersoll gadder is a machine shown in Fig. 22. It is simply an ordinary rock drill mounted upon a block which can be raised or lowered on an upright post. The post is pivoted at its lower end to a heavy cast-iron bed QUARRYING STONE. 193 plate mounted on wheels. The machine will drill holes in a horizontal line near the floor of the quarry, or in a ver- tical row, or in a line at any desired angle, for the post can be tilted at will. After drilling the holes, plugs and feathers are used to break off blocks as desired. Fig. 22 shows par- allel channels made with a channeler, and it shows the plug and feather holes made with the gadder. A drill is said to have a record of 350 ft. of holes in 10 hrs. in marble, only 1 / 3 min. being required to move from one 2- ft. hole and begin drilling the next. Fig. 22. Channelers. In quarrying sandstones and marbles, chan- neling machines are largely used; and, in the future, chan- nelers will be often used in rock excavation where it is de- sirable to have smooth sides. On the Chicago Canal exca- vation track channelers were used. Fig. 23 shows a Sul- livan channeler, and Fig. 24 shows a wheel pit extension, 21 ft. wide and 185 ft. deep, made with Sullivan channelers for the Cataract Construction Co. at Niagara Falls. It will be noticed that at each successive lift there is an offset or step of about 6 ins., but that by giving a slight batter to the 194 ROCK EXCAVATION METHODS AND COST. wall in each lift the trench preserves the same width at the bottom as at the top. A track channeler is a self-propelling machine that travels back and forth on a 10 to 3O-ft. section of track having a gage of 4 ft. ii ins. The channelers used on the Chicago Canal weighed about 11,000 Ibs. each. The stroke was 10 ins., and about 250 blows were struck per min., the chan- neler moving forward a fraction of an inch at each blow. The gage of the cutting bit was 2^ ins. at the start, and decreased in width by % in. each 2 ft., as in drilling. The extreme depth of a lift was 14 ft. The channels cut were perfectly vertical. Channelers are made that will cut up an Fig. 23. angle of 45 for use in quarries where the strata have a sharp dip. Channelers are also made to be mounted on quarry bars, the catalogues of makers showing a variety of types and sizes. Manufacturers state that a 25 to 30 H.-P. boiler will run a channeler having a 6 l / 2 to 7-in. cylinder, or that 300 to 350 cu. ft. of free air per min. at 80 Ibs. pressure will QUARRYING STONE. 195 be consumed. A re-heater is generally mounted in place of the boiler when compressed air is used. The following data are given in the Ingersoll-Sergeant catalogue as being conservative estimates based upon actual monthly averages. The number of square feet channeled per day : 75 sq. ft. of hard brownstone or sandstone ; 75 to 150 sq. ft. of marble ; 200 sq. ft. of soft Lake Superior browstone ; 250 sq. ft. of soft oolitic limestone. The actual Fig. 24. averages on the Chicago Drainage Canal work are given in Chapter XIII., where also are given reliable data of cost. It requires two men and about l / 2 ton of coal per day to run a channeler in fact, the cost of operating is practically the same as for a steam drill. It does not pay to use track channelers for quarrying granite, since broach channeling in granite is cheaper. For quarrying large dimension stones (granite excepted) the channeler has become an economic necessity. Its first 196 ROCK EXCAVATION METHODS AND, COST. cost should not prevent its purchase, once the quarry has been opened sufficiently to prove the marketability of the stone. A channeler will quickly save its cost in the better price received for the stone and in the saving on freight. The last item is one often overlooked, but it may be said, roughly speaking, that fully 20 per cent, of the stone quar- ried without channeling is lost in the subsequent cutting and dressing after reaching its destination. Since rough di- mension stone is paid for by its neat measurement, it is evi- dent that in the end the quarryman must foot the bill for this waste and the freight upon it. The actual cost of chan- neling when computed in cents per cubic foot of stone is really slight ; for the stone is not cut up with the channeler into merchantable blocks, like harvesting ice, but a series of parallel channels are cut across the quarry so as to loosen blocks of stone which may be 50 ft. or more in length. These long blocks are then split with plug and feathers into sizes that the derricks can handle. The smaller blocks are then either sawed up, or still further reduced in size by plug and feathering. If the channels are 9 ft. apart, each square foot of channel releases 9 cu. ft. of stone, so that if the cost of channeling is 9 cts. per sq. ft., the cost per cubic foot is i ct. In dimension stone quarries very large guy derricks are used, so that it is possible to handle blocks of stone weighing 20 tons. The following paragraph gives the cost of one of these huge derricks: ^ Cost of a Quarry Derrick. Saunders gives the following cost data in the magazine, Stone (New York), 1890, p. 95: A large quarry derrick capable of lifting 20 tons with a single line, having a 24 x 24-in. mast, 75 ft. high, and a 65- ft. boom actually cost as follows: Timber for mast $45-OO Timber for boom 28.00 Expense of delivering timber 16.50 Carpenter work on mast and boom at $2.50 a -\ day 25.00 QUARRYING STONE. Complete set of derrick irons, sheaves, etc. .$219.00 2,400 ft. best galv. i-in. iron rope for 8 guys. 237.00 Thimbles, clamps, etc 25.00 500 ft. steel hoisting rope, I y% in 240.00 Labor on dead men, 4 men, 2 days at $1.40. 11.20 Labor raising derrick, 8 men, 2 days, at $1.40 22.40 Labor fixing guys, 8 men, 2 days, at $1.40. 22.40 Total $891.50 197 Fig. 25. Fig. 26. Knox System of Blasting. In Trans. Am. Soc. C. E., 1891, Mr. William L. Saunders describes the Knox system of blasting, named after the inventor. (The patents have recently expired.) The system consists in drilling a num- ber of ordinary round holes in a row and then using a ream- ing tool to give the hole the shape shown by the heavy lines in Fig. 25. The reaming is done by hand. In medium sand- stone the holes may be 10 to 15 ft. apart, but in limestone I find that they are often placed as close together as 4 ft. The holes are charged with black powder, or with Judson ig8 ROCK EXCAVATION METHODS AND COST. powder, as shown in Fig. 26, a wad of hay being put in so as to make an air space between the powder and the tamp- ing. The blast causes the rock to split in a straight line in the direction of the pointed or wedge-shaped sides of the hole. For block-holing, where it is desired to split a block into just four pieces, a single hole is reamed as shown in Fig. 27. Saunders gives the following data: At Portland, Conn., 15 Knox holes in brown sandstone, charged with 2 Ibs. of black powcjer (No. C) in each hole, loosened a block of rock 1 10 ft. long, 20 ft. wide and 1 1 ft. thick, weighing 2,400 tons. Line of Fracture Fig. 27. This block was split off and moved out 2 ins. en masse. An- other sandstone ledge, open face and ends, was blasted with i Ib. of powder in each of 25 holes, and a block 200 ft. long, 28 ft. wide and 15 ft. deep was broken off and moved J^ in. At the mica schist quarries at Conshohoken, Pa., a blast of y 2 lb. of powder in a single hole broke a block 27 ft. long, 15 ft. wide and 6 ft. thick across the rift. Cost of Quarrying for the Buffalo Breakwater. In Engin- eering News May 16, 1901, Mr. Emile Low (in an article on the Buffalo breakwater) gives data on quarrying by the Knox system. The contractors, Hughes Bros. & Bangs, signed their contract Jan. 27, 1897, at the following prices: Gravel hearting, 13 cts. per cu. yd. ; rubble stone, 80 cts. per QUARRYING STONE. IQ9 ton of 2,000 Ibs. ; capping stone and revetment, $1.25 per ton. No work was done in the winter. Water telescopes were used in placing the revetment. Of revetment, 235 tons were placed daily, the stone weighing 6 2/3 tons each on an average, and up to a maximum of 17 tons. All scows were provided with glass gages and graduated rules for weighing the stone. A gage is made of 3-in. wrought iron standpipe, into which two brass cocks are screwed. Be- tween the cocks, which are 4^ to 7 ft. apart, depending on the draft of the scow, is placed a i-in. glass tul^e; and a wooden rule graduated to hundredths of a foot is attached alongside. Lockport limestone weighing 165 Ibs. per cu. ft. solid, and Medina sandstone weighing 152 Ibs. per cu. ft. solid were used for small rubble. T|br voids in the broken stone were 50 per cent. Most of the stone used was a limestone, quarried near Windmill Point, Ontario, and weighed 166 Ibs. per cu. ft. The stone was taken out in four ledges ; the first, 20 to 36 ins. thick ; the second, 6 to 9 ft. ; the third, 7 to 10 ft. ; the fourth, 5 ft. In opening the quarry a trench 30 ft. deep x 100 ft. wide was made as rapidly as possible, using heavy charges of dynamite. In quarrying the face was worked in four ledges. The top ledge was drilled with holes 18 ft. back from the face and 4 ft. apart, the holes going down to within 6 ins. of the bottom of the ledge. An attempt was made to start and end at a joint, so the ledge could be moved entire for 200 ft. or so. Three sizes of Ingersoll-Sergeant steam drills were used: A (2^ in.) ; C (2^ in.), and F (3^2 in.). At a depth of 18 ft. the hole was 1^4 ins. diam., losing yi-'m. every 3 ft. After the holes were drilled they were reamed to an elliptical shape (Knox hole) by a dia- mond-shaped tool driven either by hand or by steam. Black powder was charged, 3 or 4 handfuls in each hole first ; then the exploder, then a little more powder ; then a wad of grass was forced down leaving 2 or 3 ins. of air above the charge ; then a clay tamping to the top of the hole. Dry sand is 200 ROCK EXCAVATION METHODS AND COST. sometimes used instead of clay, being more quickly placed, and giving good results. Sand is also easier to clean out in case of misfire. To clean out a misfire hole, a steam hose is attached to small pipe through which steam and water are blown as the pipe descends, thus blowing out the charge. One block of stone, 180 ft. long, 18 ft. wide and 9 ft. thick, weighing 2,430 tons, was blasted off by one firing, requiring 52 holes, 8 to 9 ft. deep, 18 ft. from the face and $ l /2 ft. apart, loaded with 75 Ibs. of black powder. These 52 holes were loaded and tamped with sand in I hr., where it would have taken 2^2 to 3 hrs. with clay. The block, (1,080 cu. yds.) was moved 2 ft. by the 75 Ibs. of powder, that is, i Ib. of powder loosened 14 cu. yds. of solid rock. Another (3,375-ton) block 250 ft. long, 9 ft. thick and 18 ft. wide, was thrown out (2 to 3 ft.) with 150 Ibs. of powder in 62 holes After these large blocks were separated from the ledge, they were split up by drilling holes and using either plug and feathers or light powder charges. The plant consisted of : 2 A, 9 C and 3 F drills ; 8 derricks in the quarry and I at the loading dock; 4 5o-h.-p. boilers for derricks; 4 skeleton 2O-h.-p (8^4 x 12-in.) hoisting en- gines for 8 quarry derricks; I hoist and boiler for hauling cars up incline; I boiler for 2 steam pumps for draining quarry; I dinky locomotive; 50 cars, 3-ft. gauge; 68 skips, holding 3 to 4 tons, for carrying stone on flat cars; black- smith shop and 5 forges; machine shop; track, etc. The force during June, 1903, was as follows: Rates of Total per General : wages. lo-hr. day. I superintendent $167.00 per mo. $7.00 I time keeper 60.00 per mo. 2.25 i general foreman 85.00 per mo. 3.25 Stripping gang: i foreman 2.25 2.25 QUARRYING STONE. 201 4 laborers $1.50 $6.00 I team 3.00 3.00 Quarry : i asst. genl. foreman 3.00 3.00 8 foremen (one per derrick) . 2.25 18.00 14 machine drillers 2.00 28.00 14 machine drillers helpers. ... 1.50 21.00 4 hoist engineers (derricks) . 1.75 7.00 i hoist engineer (inclined plane) 1.75 1.75 5 firemen 1.75 8.75 50 laborers 1.50 75-o i water boy i.oo i.oo i watchman 1.75 1.75 i team 3.00 3.00 Loading dock : i foreman 2:25 2.25 i hoist engineer 1.75 1.75 i fireman 1.75 1.75 6 laborers 1.50 9.00 i watchman 1.75 1.75 Track repairs : i foreman 2.25 2.25 3 laborers 1.50 4.50 Blacksmith shop : i foreman 3.00 3.00 3 blacksmiths 2.50 7.50 3 helpers 1.75 5.25 Others : i locomotive driver 2.50 2.50 1 machinist 75-OO per mo. 3.00 2 carpenters 1.75 3.50 Total, $240.00 202 ROCK EXCAVATION METHODS AND COST. TABLE XXI. Month, 1903. May .... June .... July .... Aug Sept Total . . . Stone quar: Rubble. 16,535-9 12,771.2 11,444.4 9,426.2 5,937-0 56,114.7 ried, tons oi Capping. : 2,000 Ibs. Total. 16,535-9 15,312.6 16,718.2 14,544-9 8,868.9 71,980.5 2,541-4 5,273-8 5,n8.7 2,931-9 15,865.8 TABLE XXII. Cost of Cost per Labor only. Ton, cts. $5,127.51 5,154.65 5,438.91 5,071.92 3,283.85 24,076.84 31 34 33 35 37 33 Explosives, Ibs. Month, 1903. May July ...... AUg No. Holes per Day per Drill. A C F 12.5 10.0 8.8 13-8 9-5 9-5 13.3 94 9-4 Average Depth of Holes. A C F 2.7 1-7 5-3 5-i 8.7 7-3 Month, Days No. of holes drilled. Lin. ft. drilled. | g c 1903. Worked. A C F Total. A C F Total. Q US May 2^/2 513 896 556 1,965 1,385 4,757 4,840 10,982 1,691 302 211 July ..... 2^/2 674 2,101 674 3,449 1,177 10,771 4,927 16,875 2,683 292 226 Aug 23.7 620 1,978 658 3,256 853 10,098 4,677 15,628 2,558 117 236 TABLE XXIII. Lin. Ft. of Hole per Day per Drill. A C F 33.8 53.4 76.2 24.0 49.0 67.0 18.4 47.3 65.8 1.3 5.1 7.1 About i Ib. of black powder was used for every 7 tons of stone quarried, and I Ib. of dynamite for every 67 tons, and i ft. fuse for every $y 2 tons of stone. The cost of powder, dynamite and fuses per ton of stone was: In May, i. 3 cts.; July, 2.0 cts. ; August, 2.1 cts. The total cost of quarrying stone, loading and placing on seows was as follows : Cost per ton, cts. Labor 33 Coal 4 Explosives 2 Miscellaneous 5 Cost per cu. yd., cts. 74-3 9.0 4-5 1 1.2 Total 44 99.0 Cost of Quarrying Dimension Sandstone. In Engineering News, Nov. 2i, 1901, Mr. R. C. McCalla, Jr., gives the foJ- QUARRYING STONE. 203 lowing: In October, 1891, 200 cu. yds. of backing and 600 cu. yds. of dimension stone were quarried for Lock 2, Black Warrior River, Tuskaloosa, Ala. The stone was a fine qual- ity of blue sandstone quarried from the bed of the river at the falls, after diverting the water. The cost of qarrying these 800 cu. yds. was $1,598, or about $i per cu. yd. for the backing and $2.33 per cu. yd. for the dimension stone. In this month 434 cu. yds. of dimension stone were cut by stone cutters at a cost of $6.83 per cu. yd. The masonry wall is 390^ ft. long, 8 to 14 ft. wide, and 34 ft. high, built in courses of ashlar 18 to 24 ins. thick, and about 50 per cent, cut stone. In October two gangs of masons, using two der- ricks, laid 1,563 cu. yds. of first-class masonry at a total cost of 92^ cts per cu. yd., including the cost of screening sand, mixing mortar, operating steam hoists, unloading material at the wall and converting them into masonry. The itemized cost of the mason work was : Foreman, I mo $90.00 Masons, 202 days of 8 hrs., at $2.80 . . . 565.60 Laborers, 35^ " $1.20 ... 42.15 270^ " $1.00 ... 270.50 369^ " " " $ -80 ... 295.70 14634 " $ .60 ... 88.05 Boys, , 83^ " $ .40 ... 33.30 Wages paid in board 42.00 Fuel for hoists 18.49 Total, at 925^ cts. per cu. yd $1,445.79 Quarrying by Water Cushion Blasts. The following method of quarrying is described in Engineering Record, April 7, 1900: At Cobleskill, N. Y., limestone was quarried for the back- ing of the East River Bridge piers. Most of the backing is laid in 3-ft. courses ; the stone is remarkable for its smoothness, many beds requiring no dressing. The quarry is a solid stratum 28 ft. thick, with vertical fissures at right 204 ROCK EXCAVATION METHODS AND COST. angles to each other and up to 100 ft. apart. A row of vertical holes 3 or 4 ft. apart is drilled through the stratum from 3 to 10 ft. back of the face, depending on size of blocks required. The holes are filled three-quarters full with water, plugged, and a charge of black powder put in over the plugs and tamped. When fired, a block of solid rock 28 ft. high and perhaps 100 ft. long and 6 ft. thick, was separated and remained standing in its original position. Cross rows of vertical holes were drilled and fired similarly to the first holes, breaking the stone into blocks 10 ft. long and 28 ft. high. These blocks were thrown over and split with plug and feathers into blocks of thickness required for the courses. Granite Quarrying. In most granite quarries steam drills, derricks and hoisting engines are the only machines used. In "sheet quarries" after a trench is blasted out to open up a face, if no natural face exists, then the two ends of the face are freed by making channels. At the Crotch Island quarries, in Maine, two parallel rows of holes are drilled 3 ft. apart, the holes in each row being 8 ins. apart and as deep as the sheet of granite, which varies from 2 to 16 ft. thick. These holes are charged with 60 per cent, dynamite, two sticks at the bottom of each hole, then a plug of wood 8 ins. long on top, then a stick of dyna- mite 8 ins. long on top of the wood, then another plug of wood, and so on until within I ft. of the mouth of the hole, which is tamped. A cap is placed in the last cartridge in each hole, and the holes are fired in pairs. It is not neces- sary to put a cap in any of the lower sticks as the shock sends them all off practically together. This heavy loading results in tearing the granite into chips which are often hurled a great distance, necessitating blasting at night ; but the powdered granite left in the channel, is easily shoveled out, leaving a trench about 4^ ft. wide. Having freed the two ends, a long block of granite, the thickness of the sheet, is loosened by blasting. The granite adjoining the channels QUARRYING STONE. 205 when cut into blocks shows no sign of weakness in spite of the tremendous blow received in blasting. I am indebted to the Engineering Record for the follow- ing description of the Crotch Island quarry : A diagram of the method of working is shown in Fig. 28, not made to scale or true dimensions, but merely indi- cating the operations. 1-2-3-4 and 5 are successive strata of increasing height and from 5 to 12 ft. thick. Suppose that strata 4 is 9 ft. thick and it is desired to quarry from it stones 12 ft. long. On the required line B-H a pair of L.ewis* holes about 12 ins. apart and 9 ft. deep are made at Vertical Quarrvffr IK K K K Channel Vertical Quarry Face* 3 Vertical Quarry Face* Vertical Quarry Face* D with a compressed air drill and black powder is fired in them; they are swabbed out, recharged and retired, and so on several times until a crack has been opened from J to L. Another similar pair of Lewis holes is made in the line of the crack about 40 ft. away at E and they are similarly fired. Holes are drilled at G-H and so on, and the crack is pro- duced as far as desired, extending everywhere through to the stratum below. Holes 9 ft. deep are drilled 8 to 12 ins. Any drill holes placed close together are called Lewis holes. 206 ROCK EXCAVATION METHODS AND COST. apart in two rows 3 ft. apart from A to B, adjacent to the open seam which bounds one side of the quarry to form the channel. The pair of holes nearest A are heavily loaded with dynamite and fired as above described, then the next pair are fixed, and so on. Each blast pulverizes the granite between and close to the holes and throws the fragments so .far that these blasts are fired at night when only the two men in charge remain on the island. When the whole set of holes has been fired a channel has been formed about 3^2 ft. wide which extends through the stratum from A to B and gives a free face. The slab A-B-H-M, 12 ft. wide, 9 ft. thick, and perhaps 300 ft. long, is thus detached from the stratum, but is not moved more than the fraction of an inch from its original position. Blocks of any required width are laid off by lines (K-K-K, etc.) of small holes, which are drilled by hand, and the stone is split along them by the regular plug and feather method. ..Main Hoist Overhauling Weight-'' ^-Single Hoist Line Extension of Line Quarry Floor*. ~fc Hoisting "-'' Fig. 29. The method of removing these blocks is ingenious. Dog holes are made in each and the main line from a derrick, Fig. 29, is attached and a strain is put on by the engine, but does not move it. The crack B-H is perhaps 1/8 to 1/16 in. wide, and in it, opposite the center of the. blocks, are poured two cups of .thick black oil at points about a foot apart. QUARRYING STONE. 207 Between these points is poured a handful of black powder, which is covered with dirt, and has a fuse attached. The powder does not spread beyond the oil line, and so is con- fined in a thin sheet, filling the crack from top to bottom. When the fuse is lighted there is a light explosion which does not break the stone, but suffices to kick it out of its place and thus started, is easily pulled by the derrick line, over the smooth, steep slope of the underlying stratum to a point within reach of the derrick boom. There it is split into required sizes by plug and feathers, and the pieces are loaded by the derrick on cars, lowered down inclined track by cables to the two docks where other derricks load them on schooners for shipment. Quarrying Massive Granite. When granite does not occur in beds or sheets of moderate thickness, the method just de- scribed requires some modification. The method practiced at Mt. Airy, in North Carolina, according to Merrill, is as follows: No quarry face is used, but a hole is drilled in the massive granite perpendicular to the surface, and to a depth of 6 to 12 ft., according to the thickness of the stone desired. This hole is loaded with a light charge of powder and fired, then it is loaded with another light charge and fired, and so on until cracks appear in the granite at the sur- face at a distance of 150 to 200 ft. from the hole, caused by the lifting bodily of a lense-shaped mass of the granite by the force of the powder. The blasting is repeated until the lense-shaped mass is almost free all around, when it is left for a day or two so that the stresses produced by the changes of temperature from day to night break the mass of granite entirely free. Then this lenticular mass is split with wedges into blocks that can be removed. This is a very ingenious method and one well worthy of introduction wherever gran- ite occurs in massive form, but the most common method is as follows: The granite is blasted out in large, irregular chunks, using as small charges of powder as will effect the loosening of 208 ROCK EXCAVATION METHODS AND COST. the rock, the method being in fact similar to ordinary open cut excavation described in Chapter XII. The largest and most regular blocks are selected for splitting up with plug and feathers, and the other stones are used as far as possible for rubble or concrete. In upper New York, on the Spier Falls Dam construction, and in Massachusetts, on the Wa- chusett Dam work, I have seen this method used on a large scale. On a smaller scale I have used it myself, but in all cases the cost of the dimension stone so secured has been excessive. The Adirondacks "granite" is an exceedingly tough stone, but in spite of the greatest care I have had cut stone break in two while handling them, because of the shattering effect of the dynamite ; and black powder did not prove much more satisfactory. On both the large dams just mentioned it was found cheaper to import cut stone long distances than to use the local granite for certain parts of the cut stone work. If granite boulders occur, they can be split up with plug and feathers yielding splendid blocks. In fact the early qarrying in a granite region is apt to be boulder quarrying ; and, in consequence, quarries of massive granite that is blasted out in rough chunks and split with plugs and feathers, are often called boulder quarries. An effective way of making "boulders" is by large cham- ber blasting, where the amount of stone required warrants quarrying on such a large scale. Cost of Quarrying Granite. Cost data relating to the quarrying of granite dimension stone are extremely hard to secure. I have been able to find only one writer, Mr. J. J. R. Croes, who has published anything on the subject. Mr. Croes' records, together with mine, will at least form a basis for approximate estimates of cost of granite quarrying. My data apply to quarrying three-dimension stone in a sheet quarry on the coast of Maine. The total number of men en- gaged was, on the average: 6 enginemen, 6 steam drillers, 6 drill helpers, 3 blacksmiths, 3 helpers, 5 tool and water boys, 38 quarrymen, 47 laborers, 2 foremen and I superintendent. QUARRYING STONE. 209 This force quarried and loaded on boats about 1,400 cu. yds. of rough granite blocks. The stone was loaded by derricks onto cars, from which it was unloaded into boats ready for shipment. The following cost includes everything except interest and depreciation of plant, and development ex- penses : Cost, per cu. yd. Enginemen, at $2 a day (of 9 hrs.) $0.20 Steam drillers, at $2.00 0.20 Drill helpers, at $1.50 0.15 Blacksmiths, at $2.75 0.14 " helpers, at $1.75 0.09 Tool and water boys, at $i 0.16 Quarrymen, at $1.75 1.09 Laborers, at $1.50 1.15 Foremen, at $3 15 Superintendent, at $8 20 Coal, at $5 ton 45 Explosives 25 Other supplies 30 Total . $4-53 On the best month's work, when a larger force was being operated, the cost of all labor, superintendence and supplies, was reduced to a little below $4 per cu. yd. ; but the above, $4.50 per cu. yd., may be taken as a fair average of several months' work. To this should be added the charges for plant rental, quarry rental (if any), stripping (if any), and freight charges to destination. The freight rate by boat from Maine to New York is about $i a ton, but as rough granite blocks are always measured on their least dimen- sions, the freight charges when $i per ton amount to about $2.70 per cu. yd., of three-dimension stone in the rough. The explosives used were black powder, costing $2.25 a keg (25 Ibs.), and dynamite for channeling, costing 15 cts. a Ib. The sheet from which this granite was quarried averaged 210 ROCK EXCAVATION METHODS AND COST. about 6y 2 ft. thick, and was nearly flat. The stone was loosened in long blocks by Knox blasting with black powder, and was split up into sizes by plug and feathering; both hand drills and pneumatic plug drills being used for this purpose. The stone, as before stated, was three-dimension stone. To quarry random stone (not rubble) in this quarry cost about $3.50 per cu. yd. Cost of Quarrying Gneiss. Brief, but reliable data on the quarrying of stone for the Boyd's Corner Dam, near New York City, are given by Mr. J. J. R. Croes, in Trans. Am. Soc., C. E., 1875. The stone is a gneiss that is found in and about New York City, and containing so much mica that it is more properly called mica-schist. The face stone for the dam average 1.8 ft. rise, 3.6 ft. long and 2.7 ft. deep, and were cut to lay 24-in. joints. In quarrying the dimension stone, plug and feathers were used to split the stone to size ready for cutting. The cost of quarrying and plug and feathering 4,000 cu. yds. of dimension stone ready for cut- ting was as follows : Days ( 10-hr.) Cost per per cu. yd. cu. yd. Foreman, at $3 0.114 $0.34 Drillers, at $2 0.917 1.84 Laborers, at $1.50 0.429 0.65 Blacksmiths, at $2.50 0.102 0.25 Tool boys, at $0.50 0.108 0.05 Labor loading teams, at $1.50. . . 0.284 0.42 Total (not including explo- sives and teaming) $3-55 The work was done by contract in 1867-8. The rates of wages were not given by Mr. Croes, but Mr. John B. Mc- Donald has been kind enough to give me most of the rates of wages as nearly as he can remember. The length of haul from quarry to stone yard was about a mile, and Mr. Mc- Donald states that oxen were used. The cost of "teams" is QUARRYING STONE. 211 given by Mr. Croes as 0.62 team days per cu. yd., which indi- cates that a good deal of stone boat work was done, or else that there is an error in this item. The cost of quarrying 3,400 cu. yds. of rubble stone for this same dam was as follows : Days per Cost per cu. yd. cu. yd. Foremen, at $3 0.041 $0.12 Drillers, at $2 0.339 - 68 Laborers, at $1.50 0.140 0.21 Blacksmiths, at $2.50 0.036 0.09 Tool boy, at $0.50 0.035 0.02 Labor, loading teams, at $1.50. . 0.077 0.12 Teams, at $4 0.141 0.56 Total labor $1.80 It is presumable that both the dimension stone and the rubble stone were measured in the dam. Cost of Quarrying Sandstone. In quarrying thin bedded sandstone for dry slope walls and rubble, I have found that one quarryman will average about 2 cu. yds., per lo-hr. day. In doing this work no powder is used where the beds lie free, but if they are cemented together it is necessary to shake up the ledge with light charges of black powder. Wedges, crow-bars and hammers are the only tools needed for quarrying thin bedded stone where the beds can be separated by driving wedges in between them. The stone quar- ried thus is not very regular, except on the bed joints ; and, when it is dressed up by the mason, there is a considerable shrinkage in volume between the measurement of the stone corded on a stone rack and the stone measured in the wall. The mason uses the spalls to fill in the vertical joints, so that there is little or no real loss of stone. In quarrying several thousand cu. yds. of stone for dry slope wall masonry, I found that 2 cu. yds. of stone, measured corded on the wagon, made 1.55 cu. yds. of slope wall. Each quarryman 212 ROCK EXCAVATION METHODS AND COST. averaged 2 cu. yds. per day of stone as measured in the wall, or 2.6 cu. yds., measured corded in wagons. These quarry- men received $1.75 a day, and as practically no powder was used, the cost was 88 cts. per cu. yd. for quarrying stone measured in the wall, and this included loading onto wagons, but not hauling. Cost of Quarrying Limestone. Mr. James W. Beardsley is my authority for the following data on the cost of quarrying limestone for retaining walls on the Chicago Canal. The contractors selected parts of the canal where the limestone occurred in strata that were uniform, so that the beds of the stone quarried required no dressing. The stone was laid in courses averaging about 15 ins. thick, the better stone be- ing selected for the face of the wall. Guy derricks having a capacity of 6 to 10 tons, boom 40 to 60 ft. long, operated by a hoisting engine, were used for loading the stone. Black powder was used to shake up the- ledges, and the stone was then barred and wedged out. The cost per cu. yd. is the average of 93,500 cu. yds., measured in retaining walls. The mortar was only 13% per cent, of the wall; indicating an unusually even bedded stone that squared up well. The cost does not include general superintendence, installation of plant, plant rental, powder, material for repairs, and cost arising from delays. 4-1 Scrt C r ;> v o -a Hfo ;> a ,c Pn "o U x General foreman .... o.oi $4.75 00.2 00.2 Foreman i.oo 3.50 10.6 ' 7.8 Derrickmen 2.11 1.50 10.1 7.5 Quarrymen 8.42 1.65 42.2 31.2 Enginemen i.io 2.25 7.0 5.2 Firemen 0.04 1.75 0.2 0.2 Laborers 2.28 1.50 10.9 8.0 Water boys 0.33 0.75 0.9 0.7 QUARRYING STONE. 213 Blacksmiths 0.27 2 to 3 1.7 1.3 helpers . . 0.18 1.75 0.9 0.7 Carpenters 0.02 2.25 o.i o.o Drill runners 0.36 2.00 3.1 2.3 helpers 0.07 1.50 0.4 0.2 Watchmen 0.04 1.50 o.i o.i Teams and carts 0.29 3.50 and 2.50 3.8 2.8 Derricks -1.12 1.35 5.4 4.0 Drills 0.36 1.15 2.1 1.5 Total 16.52 (men) 99.7 73.7 This cost of 73.7 cts. per cu. yd., it should be borne in mind, is the cost of quarrying rubble stone occurring in regu- lar beds. The cost of quarrying Manhattan gneiss and sledging into sizes fit for rubble is given on page 222. CHAPTER XII. OPEN CUT EXCAVATION. General Considerations. In this chapter will be discussed all open cut rock work except trenching, and building stone quarrying. The removal of the earth "over burden," as the English call it, or the "stripping" is it is termed in America, is dis- cussed in my book on earthwork, so that no space will be given here to that factor of cost. In selecting a quarry site, of course, the character and depth of stripping should al- ways receive careful consideration, bore holes and test pits being sunk to ledge rock. Another feature that should never be overlooked is the drainage. A pit dug below the level of the lowest natural drainage channel will often make excava- tion exceedingly expensive where much water flows or seeps into it, and in winter it may drift full of snow, making work impracticable. I have opened several small quarries in the bed of streams that run nearly dry in summer, for in such places the stripping is likely to be slight. Quarries are pre- ferably located in the side of a hill where gravity drainage will be secured. Moreover, in such a location there is gen- erally no need of snatch teams or hoisting engines to haul the wagons or cars out of the pit ; whereas, in a pit below the level of the surrounding country there is a constant outlay of money for raising the excavated rock. Excavation in Benches. In deep, open cuts or pits, the rock is usually excavated in two or more benches or lifts. On the Chicago Canal, for example, the rock cut was about 36 ft. deep, and it was taken out in three 12-ft. lifts. There are two factors that determine the economic height of a lift: (i) The depth to which the drill will bore economically, and (2) the size into which the rock breaks upon blasting. 214 OPEN CUT EXCAVATION. 215 With the ordinary 3^-inch drill, about 16 to 20 ft. is the lim- iting depth of economic drilling, but with a 3^2-in. drill it is often economic to drill 24 ft. If a well drilling machine is used, it is possible to go down 100 ft. or more, and in fact, I have seen a shale bench 60 ft. high taken out where a well driller was in use. The height of the bench, however, is not dependent solely upon the economic depth of drilling. The higher the bench the farther back from the face may the row of drill holes be located; but the farther back that the drill holes are placed, the larger will be the chunks of rock thrown down upon blasting, unless the rock is exceedingly friable like shale. If, in a hard limestone, for example, the bench is 25 ft. high, and the drill holes are placed in a row only 9 ft. back of the face, the blast may blow out the bottom of the bench, and leave the top overhanging; and even if the top were to fall it would come down in very large chunks, although the bottom might be broken up to the desired size. This objection to a high bench with drill holes close to the face may be overcome by separating the charge in each hole into two or more parts, with tamping between ; and, as a matter of fact, I am surprised that this is not done oftener. We have seen in Chapter V. that it pays to drill as deep a hole as the capacity of the drill will permit in order to reduce the time lost in moving from hole to hole. It should be added that the depth of the hole should ordinarily be some multiple of 2 ft. (if the feed screw is 2 ft. long), for once a new bit is in place it should be made to drill as far as the feed will permit. This rule should be ignored where other reasons prevail ; thus, in stratified rock it is often well to stop the drill hole just short of a seam of stratification. In order to increase the height of the benches, a common expedient is to drill one or two rows of horizontal holes in the face of the bench, as well as the row of vertical holes, as shown in Fig. 32. This can ordinarily be done only where the bench is long enough to permit drillers to work on the 2i6 ROCK EXCAVATION METHODS AND COST. floor at one place while the loaders are working at another place. This is a good expedient to employ where one port- able drilling plant is used to work two or more quarries, for in this way a high bench can be blown down at one blast, instead of taking it down in two shallow benches, and thus time is saved in moving the drilling plant. It is also an ex- pedient often used in side hill cutting where a steam shovel is used for loading. Spacing Holes. A common rule is to place the row of vertical drill holes a distance back from the face equal to the depth of the drill hole, and to place the drill holes a distance apart in the row equal to their depth. Another rule is to place the row of holes back from the face a dis- tance equal to three-fourths their depth, and the same dis- tance apart in the row. In stratified rock of medium hard- ness these rules may be followed in making the first experi- ments, but they will lead to serious error if applied to dense granitic rocks. In the limestone on the Chicago Canal, not much of which steam shovels, usually 12 ft. in rows about 8 face and 8 ft. holes were per cent, dyna- way cut through holes were 20 ft. deep, 18 ft. back 14 ft. apart in the row. These holes were Fig. 30. was loaded with the holes were deep and placed ft. back of the apart. These charged with 40 mite. In a rail- sandstone the from the face and sprung" three times, and each hole charged with 200 Ibs. of black powder. In granite quarried for rubble for dam work, I have had to place the holes 4^2' to 5 ft. back of the face and the same distance apart, the holes being 12 ft. deep, about 2 Ibs. of 60 per cent, dynamite being charged in each hole. On rail- way work in the Rocky Mountains about the same spacing was found necessary in granitic rock that was to be broken up into chunks that a steam shovel could handle. In pit OPEN CUT EXCAVATION. 217 mining at the Treadwell Mine, Alaska, the holes are drilled 12 ft. deep, in rows 2^ ft. apart, the holes being 6 ft. apart in each row and staggered, as shown in Fig. 30. This re- quires drilling 1.7 ft. of hole per cu. yd. I am indebted to Mr. Robt. A. Kinzie for this information. The ore is a tough syenite, and the holes are spaced closer together than would be necessary if the crushers were large enough to re- ceive bigger chunks. In crushing ore or rock on a large scale the mining man and the contractor should bear in mind that it is poor economy to install small crushers, especially where the rock is so tough that it breaks out in large chunks ; for a small crusher means not only money lost due to drill- ing holes close together, but it usually means labor and powder expended in sledging and blockholing the rock be- fore it will enter the crusher. It is obviously impossible to lay down any hard and fast rule for the spacing of drill holes. In stratified rock that is friable, and in traps that are full of natural joints and seams, it is often possible to space the holes a distance apart some- what greater than their depth, and still break the rock to comparatively small sizes upon blasting. In tough granite, gneiss, syenite and in trap where joints are few and far between the holes may have to be spaced 3 to 8 ft. apart, regardless of their depth, for with wider spacing the blocks of stone thrown down by blasting will be too large to handle with ordinary appliances. The mica-schist, or gneiss, of Manhattan Island is a good example of rock that requires close spacing of holes regardless of depth. I have seen holes in it 20 ft. deep and only 4 ft. apart. The effect of spacing of holes upon the cost of excavation is best shown by tabulation of the feet of hole drilled per cubic yard excavated, as shown in Table XXIV. : TABLE XXIV. Distance apart of holes, ft. i 1.5 2 2.5 3 3.5 4 4.5 5 Cu- yds per ft. of hole... 0.04 0.08 0.15 0.23 0.33 0.45 0.59 0.75 0.93 M. of hole per cu. yd 27.0 12.0 6.8 4.3 3.0 2.2 1.7 1.33 1.08 Distance apart of holes, ft. 6 7 8 9 10 12 14 16 18 Cu. yds. per ft. of hole... 1.33 1.80 2.37 3.00 3.70 5.32 7.25 9.5212.05 Ft. of hole per cu. yd 0.75 0.56 0.42 0.33 0.27 0.19 0.14 o.n 0.08 218 ROCK EXCAVATION METHODS AND COST. Since in shallow excavations the holes can seldom be much farther apart than i to i l / 2 times their depth, we see that the cost of drilling per cubic yard increases very rapidly the shallower the excavation. Thus an excavation 2 ft. deep, with holes 2 ft. apart, requires 4.3 ft. of drill hole per cubic yard, as against 0.42 ft. of hole per cu. yd. in a deeper exca- vation where drill holes are 8 ft. apart. Failure to consider this fact ruined one contractor on the Erie Canal deepening, where rock excavation was only 2 ft. deep. Furthermore, as we have seen in Chapter V., the cost of drilling a foot of hole is much increased where frequent shifting of the drill tripod is necessary. Fig. 31, Plan. Fig. 32, Profile. Sometimes granites and traps, even though tough, will break up under the blast for several feet back of the last row of drill holes. Fig. 31, for example, shows a trap rock quarry in which the holes averaged 10 ft. apart and 14 ft. deep, but the rock was full of joints and broke readily, as is indicated in Fig. 32, which shows that the rock broke 3 to 4 ft. be- yond the drill holes when the dynamite exploded. Sedimen- tary rocks often break for much greater distances back of the last row of holes ; and this is especially so when the holes have been sprung and charged heavily with black powder. The higher grades of dynamite are more shattering in the immediate vicinity of the drill holes, but are not so apt to break the rock up a short distance away. Joveite of the same strength as dynamite appears to be somewhat slower, in consequence of which it shatters the rock for a greater distance from the hole. OPEN CUT EXCAVATION. 219 By observing carefully the appearance of rocks in differ- ent localities it is possible in a short time to become toler- ably proficient in the art of estimating the probable distance apart that holes must be drilled for the best effect with given charges of given kind of explosive ; and with this end in view a young man should avail himself of every opportunity of studying prevailing practice in spacing drill holes in dif- ferent localities. Cost of Quarrying Trap for Macadam. The following is. an average of the cost of quarrying in several different trap quarries, taken from my own records. The trap was hard to drill, being seamy, but in consequence of its seaminess it broke up~well when 75 per cent, dynamite was used. Holes averaged 14 ft. in depth, and three of these holes per day of 10 hrs. were drilled with a 3%-in. drill using steam from a portable boiler. The cost of operating the drill was : i driller $3.00 i helper 2.00 i fireman 2.00 *2O bits sharpened at 5 cts i.oo 1 / 3 ton soft coal 1.25 Hauling water for boiler 75 Oil and waste 25 Drill interest and maintenance 75 Boiler do i.oo Total $12.00 The wages paid were high, and the number of feet drilled low, so that the cost of drilling was nearly 30 cts. per ft. of hole. It required about 0.35 ft. of hole per cu. yd. of rock (solid measure), so that the cost was 10 cts. per cu. yd. for drilling. Common laborers, at $1.50 a day, sledged the rock to sizes that would enter a 9 x i6-in. crusher, and threw the stone back away from the quarry face ready to be loaded and hauled to the crusher. Much of the rock was already * At a custom blacksmith shop near the work. 220 ROCK EXCAVATION METHODS AND COST. broken small enough by the blast, so that a man averaged y l / 2 cu. yds. (solid) a day sledged and thrown back. The items of cost per cu. yd. (solid) were as follows: Cts. per cu. yd. (solid). Stripping 5 Drilling 10 Sledging 20 Dynamite (75 p. c.), 1 / B Ib. at 25 cts. in the hole. 5 Total 40 This is the cost per cu. yd. solid (not including loading and hauling away), but I cu. yd. solid makes about 1.7 cu. yds. when broken ; hence the cost of quarrying was about 24 cts. per cu. yd. measured after breaking. In loading this broken stone into carts one man would load about 15 cu. yds .(measured loose) per day. A man will load into wheel- barrows and wheel a distance of 100 ft., dump and return, at the rate of 10 cu. yds. (measured loose) per day. Fur- ther data on the cost of transportation will be found in Chap- ter X. It will be noted that these data apply to quarrying on a small scale, with a portable plant, in tough rock, but that the rock was seamy and the face fairly high (14 ft.), as shown in Fig. 32. Two men pumping out drill holes and carrying dynamite to two men charging consumed an hour in charging six holes with 50 Ibs. of dynamite, or at the rate of 12^2 Ibs. per man per hour, or about iJ/ cts. per Ib. of dynamite for charging, tamping and firing. Cost of Quarrying and Crushing Limestone. I have had occasion to open limestone quarries where a face only 5 or 6 ft. high could be worked without doing a great deal of strip- ping. The following was the average labor cost of quarry- ing and crushing 60 cu. yds. loose measure, or 35 cu. yds. of solid rocki per lo-hr. day, the average being that of 4,000 cu. yds. : OPEN CUT EXCAVATION. 221 Quarry. Crusher (9 x 16 ins.). i driller $2.50 I engineer $2.50 i helper 1.50 2 men feeding 3.50 i man stripping ... 1.50 6 men wheeling 9.00 4 men quarrying . . . 6.00 i bin man 1.50 i blacksmith 2.50 i general foreman . . . 3.00 Total $14.00 Total $19.50 The "four men quarrying" barred out and sledged the blasted stone to sizes that would enter the crusher ; the "six men wheeling" wheeled it in barrows about 150 ft. to the crusher, and delivered in on a platform. The dynamite used was 40 per cent, at 12 cts. per lb., and 0.4 Ib. was used per cu. yd. of crushed rock, or 0.7 lb. per cu. yd. of solid rock. One electric exploder, costing 3 cts., was used per pound of dynamite. A long ton of coal, at $2.50, and a gallon of oil, at 25 cts., were used per shift for both crusher and drill. Holes were drilled about 5 to 6 ft. apart, the face being 5 to 6 ft. high, and the drill averaged 60 ft. per shift. Sum- marizing we have : Wages of quarry crew $14.00 Wages of crusher crew I 9-5 24 Ibs. of dynamite with exploders, at 15 cts. 3.60 i ton of coal 2.50 i gallon of oil .25 Total $39.85 This is equivalent to 65 cts. per cu. yd. of crushed stone measured in the bins, which is a high cost, due to the low quarry face, and the small plant operated. Current repairs to the drill cost i ct. per cu. yd. and the crusher another i ct. ; steam hose, drill steel and sundry supplies cost another i l /2 cts. per cu. yd. of loose rock. Quarry rent was 5 cts. per cu. yd. Cost of Pit Mining, Brewster, N. Y. In the magazine, Stone (New York), 1892, page 414, Saunders gives the fol- 222 ROCK EXCAVATION METHODS AND COST. lowing data of cost of ore bank blasting in an open cut at the Croton Iron Mines. The work was done under Mr. Charles Vivian, contractor, between July 13, 1891, and Jan. 5, 1892: Total cu. yds. rock and ore 9> 2 95 Total number of drill holes . . . 238 Total feet drilled . .2,988 Average depth of hole, ft 12.50 Ft. of hole per cu. yd 0.32 Lbs. of 52 p. c. dynamite per cu. yd O-44 Cost per cu. yd. Labor of all kinds .$0.613 Explosives .081 Steam for drills 028 Repairs and supplies 015 Total , .$0.737 This cost includes blockholing and sledging the ore to 7-in. cubes, and the rock to lo-in. cubes. A baby drill was used for blockholing. Mr. Vivian writes me that his original records have been lost, so that the rates of wages cannot be ascertained, but I think it is probably safe to assume that machine drillers received about $2.75, and common laborers $1.25 to $1.50 per lo-hr. day. Cost of Excavating Gneiss. I am indebted to Mr. John J. Hopper, civil engineer and contractor, for the following data, part of which originally appeared in the magazine, Stone. The work involved the excavation of 29,295 cu. yds. of gneiss (or mica schist) at One Hundred and Twenty- seventh street, New York City. The drilling of the main holes was done with four 3^-in. Ingersoll steam drills, and two "baby drills" were used for drilling block holes. The average height of the lifts was 12 to 15 ft., and the cut ranged from 2 to 63 ft. deep. Hand drillers and sledgers re- ceived $2 per lo-hr. day ; laborers handling stone and load- ing wagons received $1.50; one of the machine drillers re- ceived $3, and the rest of the drillers received $2.75 a day. OPEN CUT EXCAVATION. 223 The baby drills were used only on the largest pieces thrown down by the blast; the ordinary sized stone from the blast was broken up by hand-drilled holes and by sledges to sizes suitable for building rubble foundation walls. A good deal of the stone was piled up during the winter until it could be sold. The drilling part of the plant cost $1,800; the boilers, derricks, hoists, etc., cost $1,080; 40 per cent, dynamite, costing 20 cts. per lb., was used. There were 18,433 nn - ft- of main holes drilled (not including block holes) in exca- vating 29,295 cu. yds. of solid rock. The total cost of the work, including the plant, cartage, sledging, etc., was $52,- 635. The itemized cost was as follows : Cts. per cu. yd. Foremen and timekeepers 8.0 Engineers and drillers 10.9 Sledgers 38.3 Derrickmen and helpers 9.6 Labor, loading, etc 24.7 Hand drillers 11.7 Blacksmith and helper 5.3 Hauling away in wagons 40.5 Explosives 9.8 Coal, coke, oil, etc 6.0 Repairs to drills i.o Repairs to boilers, derricks., etc 1.2 Total per cu. yd $1.67 Mr. Hopper informs me that in sound rock where 2O-ft. holes could be drilled, a drill would average 70 ft. in 10 hrs. ; but in shallow drilling the drills would frequently not average over 25 ft. each. Cost of Excavating Sandstone and Shale. In excavating shales and sandstones of the coal measures of Pennsylvania, Ohio, Virginia, etc., I find that holes are usually 20 to 24 ft. deep, and spaced 12 to 18 ft. apart. On an average we may say that for every cubic yard of solid rock there is V 10 lin. ft. 224 ROCK EXCAVATION METHODS AND COST. of drill hole, when cuts are very wide, covering large areas of ground; but in thorough cuts for railroads it is not safe to count upon much less than 2 / 10 ft. of drill hole per cu. yd. The holes are almost invariably sprung with 40 per cent, dynamite and then charged with black powder. As low as Vso lb. of dynamite per cu. yd. may be used for springing holes in shale, and as high as */2 lb. per cu. yd. in sandstone that is to be very heavily loaded. (See page 149). I should put the average at 1 / 20 lb. of dynamite per cu. yd. of shale, and Vio lb. per cu. yd. of sandstone. A very common charge is 8 kegs (200 Ibs.) of black powder per hole, or about I lb. per cu. yd. in side cuts, and ij^ to 2 Ibs. per cu. yd. in thorough cuts, although as high as 3 Ibs. per cu. yd. have been used in thorough cuts in sandstone where special effort was made to break up the rock to small sizes for steam shovel work. The drilling of the deep holes costs not far from 40 cts. per lin. ft. where drilling is done by hand with wages at 15 cts. an hour, and it may be as low as 12 cts. a lin. ft. if well drillers are used. Soda powder costs about 5 cts. per lb., and 40 per cent, dynamite 12 cts. per lb. We have, therefore, the following: Cts. per cu. yd. Drilling Vio ft. to 2 /io ft. at 40 cts 4.0 to 8.0 Dynamite 1 / 20 lb. to Vio lb 0.6 to 1.2 Powder, I lb. to 2 Ibs. 5.0 to 10.0 Total for loosening the rock 9.6 to 19.2 The rock is commonly loaded with steam shovels, and it is not safe to count upon more than 500 cu. yds. of shale, or 250 cu. yds. of sandstone per shovel per lo-hr. shift. The daily (lo-hr.) cost of operating a shovel will average about as follows: i foreman $4.00 i engineman 3.50 i craneman -. . . 3.00 i fireman 1.75 6 pit men 9.00 OPEN CUT EXCAVATION. 225 i locomotive driver $3- i trainman 2.00 4 dump and trackmen 6.00 i pumpman 2.50 i 1 / 3 tons coal, $4, and oil, 25c 4.25 Total $39- For plant rental and repairs from $5 to $15 a day must be added, making a total of, say, $50 a day, or a cost of 10 cts. per cu. yd. for soft shale to 20 cts. for sandstone for loading and transporting a short distance, such as 1,000 ft. Where grades are steep and distances long, two or more dinkey loco- motives will be required. The resistances of rolling friction and grades are discussed in my book on earthwork, and need not be repeated here. We see that the cost of loosening, loading and transporting shale from side cuts may be as low as about 20 cts. per cu. yd., and sandstone from thorough cuts may be as high as 40 cts. per cu. yd., wages and prices being as above given, and hand drills used for loosening. The cost of moving the plant to and from the work is not included in the above costs. Other data bearing on steam shovel work will be found in Chapters X. and XIII. It is necessary to study all the conditions of each case and to apply the data given in va- rious parts of this book. I have merely given the above as an example of shale and sandstone excavation on railway work. Cost of Railroad Excavation in Tennessee. For the fol- lowing data I am indebted to Mr. Daniel J. Hauer, C. E., an engineer and contractor experienced in railroad con- struction : "In railroad work it is difficult to keep separate records of the cost of excavating earth, loose rock and solid rock. Specifications differ as to classification of excavated mate- rials and engineers differ in their interpretation of specifi- cations, all of which must be borne in mind when studying data of railroad excavation. The costs that follow apply to 226 ROCK EXCAVATION METHODS AND COST. railroad work done in the Cumberland Mountains of Ten- nessee. Under "loose rock" were included shale, slate, coal, soft friable sandstone, cemented gravel, stratified stone in layers less than 6 ins. thick and boulders not less than 2 cu. ft. nor more than I cu. yd. in size. Solid rock included all "rock in place which rings under the hammer," except rock in layers less than 6 ins. thick. The clause relating to 6-in. layers was not enforced, but such rock and slate were classified as solid rock. The excavation was all done by hand, there being no power drills or steam shovels used. The rock was hauled to the embankments in barrows, carts and cars. Wages ranged from $1.25 to $1.50 per day; the day being 10 hrs. long in winter and n hrs. in summer; the average wage being about 1^/2 cts. per hr. Laborers were scarce and inclined to be independent. Foremen received $3 a day, or an average of 28.6 cts. per hr. Black powder cost $1.22 per keg (25 Ibs.) ; 40 per cent, dynamite, 11% cts. per Ib. ; Jud- son powder, 7^4 cts per Ib. ; double tape fuse, 42 cts. per coil of 100 ft. ; quintuple caps, 75 cts. per 100, and electrical exploders, 4 to 7 cts. each, according to lengths. The men were worked in gangs of about 10 men under one foreman, the dumpmen and cart drivers being included in this num- ber. The drivers' wages are included in the cost of "teams," there being one driver to two one-horse dump carts on short hauls, and one driver to three carts on long hauls. Two carts and a driver were paid $3 a day. When dump cars were used, two cars, one mule and a driver were counted at $2 a day. By dividing the number of loads (tal- lied by the dumpman) into the yardage given by the en- gineers in the monthly estimates, the following results were obtained : Dump cart, without tail gate .... Earth 0.6 cu. yd. " " ....Rock 0.35 " " Dump car, " " " .... Earth i.o " " " " ..Rock 0.6 " " OPEN CUT EXCAVATION. 227 Dump car, with tail gate Earth 1.25 cu. yd. " " Rock 0.7 " Tail gates were not used in carts until the haul became 1,200 ft. or more; and tail gates were not used in cars until the haul became 1,500 ft. The dump car body held iV 2 cu. yds. water measure. It is safe to count upon loads 10 to 15 per cent, less than those above given ; thus, in a train of two or three cars, without tail gates, count on y 2 cu. yd. of solid rock per carload. In short hauls, the driver takes one cart or car to the dump while the other is being loaded. All items of cost are given, except the salaries of super- intendent, time keepers, blacksmith and night watchmen; but the cost of these items was 6 per cent, of the total cost, being distributed as follows: Superintendent . $975-5 Blacksmith .-rrTTT^-r. 586.80 Time keeper 5 8 4- 8 5 Night watchman 457-5 Total $2,604.65 Each cut was opened up with wheelbarrows, and when the extreme haul for these became 50 ft., either dump carts or cars were substituted. The cars were operated on wooden rails, made of 2 x 4-in. scantlings, either of oak or beech. The entire cost of these tracks is included with labor, except the cost of the two by fours, which were used several times, these being only 10,000 ft. B. M., bought at a cost of $10 per M. These tracks worked well except in dry weather, when it was necessary to have a man pour water on the rails, or else the cars were frequently derailed. On sharp curves and- at switches, guard rails were used. The cost of trimming and dressing up the work is included in each case but it may be of interest to consider some fea- tures of it separately. All cuts were excavated a foot below the cross-section stakes, and then this foot was rilled back, leaving a ditch on either side of the cut wherever the plans called for one. If this back filling was made from the cut 228 ROCK EXCAVATION METHODS AND COST. no payment was made for the work ; but if it was done with material from a borrow pit, it was paid for as earth. Blue prints were furnished for this work and stakes were driven to grade, and the work was supposed to be done within 0.05 ft. This method saved the railroad company a little money in ballasting, but it added materially to the cost of dressing up for the contractor. He was allowed 6.6 cu. yds. of earth on a 10 curve (the maximum curve used) per 100 ft. of roadbed, for putting on this elevation. On lighter curves a less amount was allowed. In nearly all cases the cuts were taken out a foot below grade, and the embankments were high; yet to dress up 6,300 lineal ft. of roadbed cost $i,- 226.14, making a cost of 0.97 cts. per sq. yd., or i l /2 cts. per cu. yd. of material moved within the 6,300 ft. This cost is excessive, especially when slopes of cuts have been trimmed as work progresses, so that only the roadbed has to be dressed. Such work should have been trimmed and dressed for less than y 2 ct. per sq. yd. Table XXV. gives the yardage and the cost of excavating each cut; and Table XXVI. gives the cost per cubic yard for each class of material. It should be remembered that wages were only 13^ cts. per hour for laborers, that two mules and a driver were 30 cts. an hour. To the costs given in the tables 6 per cent, should be added for superin- tendance and general expenses. The "average haul" was measured on the profile from center of gravity of cut to center of gravity of fill. TABLE XXV. Cu. Yds. 1 I JD X w $96 O u - o Cy fr, i-j $982 V} 03 H $4O4 3 o $1,482 jd 1 2,401 II 2,281 1,644 3 r "o 6,416 II Ill $11 $266 YJ/*^*' $167 $i 610 XT' V ^T' $ 4 6 $27^ $224 $2,158 '**>' : TJ7 A 717 2 6lQ 517 2,831 1,234 7,867 IV V \p-i v_n_/ $34 *r ? v - /i \f $278 $359 H^^/ O $36 $112 $348 $521 4*)\J L ^ 1,953 347 596 502 849 2,549 VI. $10 $180 $36 $244 1,20^ 408 607 2,310 OPEN CUT EXCAVATION. 229 $185 $1,086 $196 $1,467 $1,003 $2,483 $454 $3,940 $322 $1,659 $48 $2,029 . $397 $1,924 $346 $2,667 2 $222 $883 $225 $1,330 $1,090 $4,978 $777 $6,845 $23 $327 .... $350 TABLE XXVI. Cost in Cent? per Cu. Yd. o be QJ /""^ - - rl 903 1,664 i, 1 69 3,736 176 177 6,568 6,921 815 5,960 6,775 ,043 1,504 2,934 6,481 764 969 2,089 3,822 868 1,117 11,676 13,661 400 600 i ,000 jd % ^ *TJ ^i bo I-M || tJ 3\ o <-> o o 'II II 4-> 03 Time of Year. II. 21.9 43-1 922 D Nov., Jan., Apr. to July. 12.8 25.6 ISO D Summer. 12.3 24.6 46.8 350 C Aug. to Feb. .... 26.7 50.8 2OO D Aug. 1 6.6 33.2 225 D Apr. and May. 5-5 II. 21. 1 425 D Aug. 17.0 34-0 64.0 450 D Winter and spring. 15-5 31.0 58.7 300 CandD Aug. to Dec. .... 16.5 31-8 50 W Jan. to Mar. 16.5 33-0 62.5 475 CandD Aug. to July. 12 $ 2$ O 47 ^ 2^0 Summer. 144 28.8 58.4 610 C Aug. to Aug. 21.8 43-7 .... So W 26.7 so.6 u I II Ill IV V VI VII. ... VIII. .. IX X XI XII. ... XIII. .. Average NOTE. The months given in the last column are inclusive. In the next to last column the letters denote as follows : D means by dump carts ; C, dump cars ; C and D, both dump carts and cars for about equal length of time; W, wheelbarrows. The materials encountered in these 13 cuts were as fol- lows: Case I. Shale and slate ledges across part of cut, large and small sandstone boulders, stiff clay and earth. Work was stopped in wet weather on account of slides. Case II. Disintegrated rock, sandstone boulders, fire clay and earth. Case III. Slate rock in masses, shale, sandstone boulders 230 ROCK EXCAVATION METHODS AND COST. and earth. A thorough cut first made, then borrowed from the sides. One mule pulled two cars. Case IV. This work consisted in reducing a slope that was 54 to : > making it I to I. Sandstone and rotten sand- stone; the latter pulverized on being shot. Case V. This was a borrow pit of disintegrated sandstone and average earth. Some of this sandstone should have been classified as solid rock. Case VI. Slate in masses, fire clay, fire clay shale and debris from old slides consisting of boulders and earth. One foreman handled two gangs. Case VII. This was a borrow pit, material being same as in Case VI. Case VIII. Solid gray sandstone (seamy) and a small amount of earth and loose rock at each end. Thorough cut. Case IX. This was a borrow pit and a continuation of the sandstone ledges of Case VIII. Cases X. and XI. Mountain debris, consisting of sand- stone boulders (large and small), fire clay, cemented gravel and earth, material always wet and heavy to shovel; slides were frequent in winter. Case XII. Half of this cut was solid sandstone. At the other end was slate, fire clay shale, disintegrated shale, clay and large sandstone boulders. The cut was 27 ft. deep at deepest point. In the winter the shale slid on the fire clay shale, bringing down several thousand yards of slides into the cut. For five months (December to April) the shovelers stood in mud and water above their ankles. Material would frequently run out of the cars on the way to the dump. Case XIII. This was a trench 6 ft. deep, 20 ft. wide on top, 15 ft. wide on bottom, dug to carry a creek. It is not possible in all cases to compare the cost of one cut with another, but from the figures given several deduc- tions can be made. In Cases X. and XL the materials ex- cavated were similar. There was a difference in the length of the haul, but the great difference in the cost of the work can be attributed to the time of the year that the excava- OPEN CUT EXCAVATION. 231 tions were made. One was worked entirely during the sum- mer, while the other was worked during both summer and winter. If both cuts had been made in the summer months their costs should have been approximately the same, the slight difference in cost of haul counting in favor of the cut in Case XL A valuable lesson can be learned from Cases VIII., IX. and XII. In these the greater part of the material was sandstone, being classified as solid rock. In two cases the work consisted of thorough cuts and one a side hill borrow. In VIII. the cost of explosives was a little more than $1,000, while with nearly twice the yardage in XII. the cost of the explosives was not $100 more. The difference in the cost of the teams in the two cases is readily accounted for when the lengths of the average hauls are compared. The great cost of powder in Case VIII. can to a great extent be attributed to the waste of incompetent fore- men. The majority of boulders were "mud capped" instead of being "blocked," or having the charge of dynamite placed under the rock. In all, seven different foremen worked in this cut, four of whom were discharged as incompetent ; but the damage was then done and the money in part lost. All thorough cuts were shot with Judson powder, as the rock is broken better than when black powder is used, and much "blocking" of boulders is prevented. Better results can al- ways be obtained with Judson, except where it is desired to waste, when black powder should be used. In Case VI. Jud- son powder pulverized all the solid rock, so that no "block- ing" was needed, as all the material was easily worked by hand. In Case IX., as it was very important that none of the material should be wasted, Judson powder was used, and less than $50 was spent in breaking up boulders. The cost of explosives in the entire borrow was only 4^4 cts. per cu. yd. of rock moved. In comparing all the cost items of thif case with Cases VIII. and XII. the striking difference in the cost of side hill wcrk and thorough cuts can be seen. It was found necessary to widen and lower to grade cer- tain cuts that had been left incompleted by another contrac- 232 ROCK EXCAVATION METHODS AND COST. tor. The cost of such skimming work is high, as is well shown in Table XXVII. : TABLE XXVII. Cost per Cu. Yd. t/j i * 1 , II 3 * 1 f & " 113 u u E w j ffi g H XIV 626 225 $0.098 $0.384 $0.103 $0.093 $0.001 $0.684 XV 484 ISO .I08 .488 .122 .O8l .001 .800 XVI 415 325 .095 .334 .116 .091 .024 .660 Case XIV. was a breast 10 ft. deep on the side of a cut in hard blue sandstone. Case XV. was the widening of both slopes of a cut in red sandstone and the excavation of the bottom. Case XVI. was the excavation of the bottom of a cut in blue sandstone ; at no place was the face excavation more than 5 ft. deep; i^-yd. dump cars were used. In cases XIV. to XVI. laborers received $1.50 per 10 hrs., and foremen $3 to $3.50; one driver and two mules on two carts were rated at $3.50 a day; powder was $1.20 a keg, and dynamite (40 per cent.) was 10 cts. per Ib. Cost of Blasting Boulders. I am also indebted to Mr. Hauer for the following data on the cost of blasting "loose rock" in railway cuts. So far as I know these are the only records in print on this subject. The bojulders were red sandstone and blue sandstone, the latter being the harder and tougher of the two, and were all broken to sizes that could be loaded by hand. With wages of hand drillers and sledgers at $1.50 for 10 hrs., and 40 per cent, dynamite at 10 to 13 cts. per Ib., the costs were as follows : Sledging a i2>^-cu. ft. blue sandstone boulder to small sizes took I man 5 mins. and 2 men 2 mins., at a cost of 4.9 cts. per cu. yd. Sledging a 16 cu. ft. blue sandstone boulder took i man 3 mins., or i% cts. per cu. yd. Sledging a 12-cu. ft. blue sandstone boulder took 2 men 8 mins., or 9 cts. per OPEN CUT EXCAVATION. 233 cu. yd. Sledging a 7^-cu. ft. blue sandstone boulder took I man 3 mins., or 2.7 cts. per cu. yd. Sledging a 27-01. ft. red sandstone boulder took 3 men 10 mins., or 7^2 cts. per cu. yd. Sledging a 23-cu. ft. red sandstone boulder took 3 men 5 mins., or 4.1 cts. per cu. yd. Sledging an i8-cu. ft red sandstone boulder took I man 4 mins., or i l / 2 cts. per cu. yd. The average cost of breaking up small boulders with sledges was 5 cts. per cu. yd. The cost of mud capping 17 boulders is given in the following table, in which the first four boulders were red sandstone, and the rest were blue sandstone : TABLE XXVIII. ~i< en iT 3 3 T3 v> r ) ^ r ? U w a KM e/j 1 E ^5 O i P & 1 c/5 b 3 ctf I tn U 1? i 17.0 30 $2.10 9 14.7 2 1.6 8 2O 2 18 3 I.O 8 15 2 25 4 Z A 8 10 2 27 5 I.O 1:? 15 10 2 1 48 6 1.2 8 20 2 25 7 1.4 8 25 2 25 8 o-7 j 8 1 ii 10 15 2 [ 68^ 9 0.33 8 7/2 2 52^ 10 i-3 ii 20 2 25/ ii 0-45 ii 15 2 62.2 12 o.S ii 15 2 56 13 0-5 ii 10 2 '46 14 0-5 10 7/2 2 39 15 10 1754 2 17-3 16 I.O 10 7/ 2 I9/ 17 I.O IO I2J4 2 24^ Boulders No. 5 and 8 were blasted twice. In addition to the cost of mudcapping given in the table, the following was the cost per cu. yd. of sledging boulders : No. 5, 3 cts. ; No. 6, 5 cts.; No. 7, 4 cts.; No. 10, 6 cts.; No. 15, 2 cts. The average cost of breaking up these 17 boulders by mudcap- ping was 36 cts. per cu. yd. The cost of blockholing five boulders is given in the fol- lowing table, all boulders except No. I being blue sandstone : 234 ROCK EXCAVATION METHODS AND COST. TABLE XXIX. t *8* =! f f 3 S ^ -c u s 3 C Q . fe OT - ij <3 *s i i_;i 3 &- - -M . &> en .J2 O 13 *rt '*'* S K C^fa., t/5 C G Q,f ) I"V 4_i 4_> I o; 3 .N 5 ^^ o o 1 - J ^c/}QU QO j HH 1 13 3 105 20 2 18 145 ii 2 31 40 10 2 8 60 20 3 4^/2 i l /2 52 12 2 10 76 17 4 2^ i 30 82 5 45 18 5 2 2/3 20 10 2 4 36 18 The labor item in the seventh column includes the cost of lost time in leaving the pit during the blasting. Boulders No. i and 3 were fired alone, making this labor item greater than in the other cases when several boulders were fired at one time. The cost of undermining and blasting sandstone boulders was as follows: A 5o-cu. yd. boulder was broken up by undermining it, charging with black powder, and tamping with a large quantity of sand around it, the total cost being 25 cts. per cu. yd., distributed as follows : 4 kegs of powder, at $1.64 $6.56 2^ Ibs. 40 per cent, dynamite, at 16 cts 40 Cap and fuse 04 Labor 5.50 Total $12.50 The labor force was i foreman at 30 cts. an hour, 2 labor- ers at 10 cts. an hour and I boy at 5 cts. an hour. Five other smaller boulders were undermined and blasted at costs given in the following table : TABLE XXX. Reference Size, Cu. Number. Yds. Labor, Cts. Dynamite, Cap and Total per C Cts. Fuse, Cts. Yds., Cts. I O.9 10 5 l /2 2 19.4 2 1-5 13 16^2 2 21 3 1-25 9 8 2 15.2 4 i.o 9 5 2 16 5 2.5 9 8 2 8.4 OPEN CUT EXCAVATION. 235 Boulders No. I and 2 were red sandstone, and laborers were paid 13^ cts. an hour; 40 per cent, dynamite, n cts. per Ib. Boulders No. 3, 4 and 5 were blue sandstone ; labor- ers were paid 15 cts. an hour ; dynamite, 10 cts. per Ib. Comparing the average costs of breaking up sandstone boulders by the four different methods we have: By sledging 5 cts. per cu. yd. By mudcapping 36 " " By blockholing 17 " " " " By undermining 16 " " " " In none of the casqs did the men know that they were being timed, so that the costs may be assumed as fair aver- ages. It is evident that mudcapping should be used only in steam shovel work through cuts where boulders must be broken up quickly so as not to delay the shovel. To illus- trate how expensive it is to mudcap, one more example will serve. In a cut (approach to a tunnel) 1,054 cu. yds. of solid sandstone were excavated, 36 kegs of black powder costing $51 being used. In this same cut there were 512 cu. yds. of loose rock (boulders) which were broken by mud- capping, requiring 750 Ibs. of 40 per cent, dynamite, costing $90. For moving boulders short distances to a steam shovel, to a derrick or even to the dump, a stone sled (or boat or "lizard") should be used. Where many boulders are to be moved to the dump use three sleds, and several chains for each team. Have a dump crew and a loading crew, and thus, with the extra sleds, keep the team moving. Boulders from y^ to I cu. yd. can thus be moved a short distance cheaper than by blasting and loading into wagons. By hav- ing a number of rollers at the dump, the dump crew can work the sled along on the rollers, using bars and levers, until it tilts up at the edge of the dump and discharges its load. For loading large scattered boulders into wagons use a three-leg (or tripod) derrick with a Triplex block, A "lift- 236 ROCK EXCAVATION METHODS AND COST. er" or "devil" is a simple, handy, device for loading 3 or 4 cu. ft boulders by hand. The "lifter" is simply a stretcher made of two 3-in. round poles 8 ft. long, with 2-in. plank, 2^/2 ft. long, nailed across so as to make a platform on which to carry the boulder. Several men can thus carry a j/2-cu. yd. boulder. Where a few large boulders are to be loaded upon a wagon, take off the two wheels on one side of the wagon and skid the boulders up into the wagon; then use levers to raise the wagon axles, and replace the wheels. Where many boulders are to be loaded, a derrick car may be used. A car provided with an A-frame at the front end, a hoisting engine, and light jack arms, will lift 5-ton boul- ders. Such a car will cost about $1,000 and the engine will cost another $1,000. When a steam shovel is used to load large boulders or loose rock that will not pass through the dipper, use chains. A chain should have a hook at each end, and one hook to fasten the boulder and the other to hook into a chain fastened to the dipper arm or to a chain on one of the dipper teeth. Two small boulders, l / 2 to I cu. yd. each, may be chained out at one time. For large boulders, i to 3 cu. yds., use a chain with a pair of grab hooks and keep one or more men busy drilling dog holes in the boulders for the grab hooks to bite into. With a 65-ton shovel it is possible to load a 4 cu. yd. boulder. Summary. The two cost items that the inexperienced man should seek first to inform himself upon, are : ( i ) The number of feet of hole drilled per cubic yard in different kinds of rock; and (2) the number of pounds of explosive required per cu. yd. under varying conditions. In Table XXXI. I have given a summary of these items as applying to open cut work discussed in this book ; the table does not apply to trenching, tunneling or other narrow work. Two examples are given for sandstones and two for shales, such as occur in the coal measures of Pennsylvania. In a thor- ough cut on railroad work, we have conditions that ap- OPEN CUT EXCAVATION. 237 proach trench work, requiring more feet of hole and more powder than in open side cuts ; hence the differences between Examples 5 and 6, 7, and 8. It will be observed that the large amount of drilling in Example 2 is due to the shallow- ness of the face or lift, and in Examples 9 to 12 it is due to the toughness of the rock. I shall greatly appreciate further contributions of similar data from my readers, for use in future editions. The greater the number of records, such as those in Table XXXI. the better will readers be able to judge the range and the average for each class of rock. TABLE XXXI. Per Cu. Yd. -4-T ^ ' js Q ~ W Q *&< *> O <]j rt a" 1 "' ' ''5 *^^ W Q H-] H-) O Kind of Rock. 1 12 0.40 ... 0.75 40% Limestone, Chicago Canal. 2 6 i.oo ... 0.7 40% for crushing. 3 20 0.37 50% for cement. 4 15 0.43 ... 0.26 50% (holes sprung). 5 20 o.i i.o o.i 40% Sandstone, side cut. 6 20 0.2 2.0 0.2 40% thorough cut. 7 24 0.08 0.7 0.03 40% Shale, soft, side cut. 8 24 0.20 1.5 o.io 40% hard, thorough cut. 9 1 6 1.36 ... 0.20 60% Granite, for rubble. 10 12 1.33 ... 0.60 40% Gneiss, New York City. 11 14 0.63 ... 0.50 40% 12 12 1.7 ... 0.67 40% Syenite, Treadwell mine. 13 i2 l /2 0.32 .. . 0.44 52% Magnetic iron ore. 14 14 0.35 ... 0.20 75% Trap, seamy. 15 16 i.o ... 0.70 40% " massive. CHAPTER XIII. METHODS AND COSTS ON THE CHICAGO DRAINAGE CANAL. General Conditions. The illustrations in this chapter originally appeared in Engineering News. For cost data I am particularly indebted to Mr. W. G. Potter, to Engineer- ing News and to Engineering Record. No excavation work of such magnitude as the Chicago Drainage Canal has ever been so fully described in print; and, what is more noteworthy, no such complete record of cost has ever been published before. In view of these facts, and because such a variety of machines were used in exca- vating this canal, I have thought it wise to devote one chap- ter to this great work. K 30f>'0" - H x. K ZOS'O Chicago Main Drainage Channel. Fig. 33- The rock section of the Chicago Canal is 160 ft. wide at the base, and has vertical sides 36 ft. high. The rock was excavated in three 12-ft. lifts, channeling machines being used to cut perfectly smooth walls. The excavation was classified as solid rock and "glacial drift" ; the latter includ- ing all material other than solid ledge rock. The solid rock was limestone (Niagara period), occurring in horizontal strata. The lower lift is said to have been almost twice as hard to drill and channel as the upper lift. The contractors were required to base their bids on the results obtained by borings. Mr. L. E. Cooley, the first chief engineer, in- tended to sink a number of test pits, but was overruled by the first Board of Trustees, which acted under the usual cents wise and dollars foolish policy of political "boards." 238 METHODS COSTS CHICAGO DRAINAGE CANAL. 239 The borings gave an entirely misleading idea of the char- acter of the glacial drift, and failed to indicate that much of it was an exceedingly tough hardpan of cemented gravel, and of gravel boulders mixed with clay. Several contract- ing firms were ruined by the subsequent action of the board in refusing to release them or to reclassify the material. The average contract price on the "glacial drift" excava- tion was 30 cts. per cu. yd. and 78 cts. per cu. yd. on the solid rock. There were about 26,000,000 cu. yds. of "glacial drift" and 12,300,000 cu. yds. of rock. The prices for ex- cavation included all bailing and draining. The contracts contained an excellent clause that required that the work done each month should be not less than such a proportion of the whole work as one month was of the total number of months agreed upon for completion of the work. Excavating Very Tough Clay. After removing the upper layer of prairie soil, an exceedingly tough or "indurated clay" was encountered that required blasting. Boulders were found scattered through the clay, and in some cases in such quantities as to make a regular hardpan, of which I shall speak later. On one section, 14 men were kept busy drilling and blasting for one Bucyrus shovel hav- ing an output of only 350 cu. yds. per lo-hr. shift. The shovel took out a swath 12 to 14 ft. deep, and blasting holes were put down 16 to 18 ft. deep, sprung with dyna- mite and charged with Judson powder. On another section Barnhart AA shovels averaged 520 cu. yds. per lo-hr. shift for seven months. As high as 600 cu. yds. was averaged by a Bucyrus shovel on another section, showing that the tough- ness of the material varied considerably. For data as to the shovel output and cost in this clay, the reader is referred to my book on earthwork. Excavating Hardpan. The worst hardpan encountered in this canal work is shown in Fig. 34. It consisted of boulders and stones cemented together so that a vertical face was left after blasting. The only way that this ma- 240 ROCK EXCAVATION METHODS AND COST. terial could be loosened economically was by means of large charges of dynamite fired at the rear of small tunnels, as shown. The contractors who at first bid 28 cts. on this work subsequently secured 50 cts. a cu. yd. on a re-letting. On Section 4 of the canal there were four steam shovels ; one 70- ton Osgood, one 6o-ton Bucyrus and two 45-ton Bucyrus. According to the reports of the canal engineers, for October Fig. 34- 1894, the Osgood shovel worked 27 ten-hour shifts, averag- ing 406 cu. yds. per shift. The three Bucyrus shovels aver- aged 760 cu. yds. for the 6o-ton shovel, 458 and 480 cu. yds. for the two 45-ton shovels. The general daily average for the season was 493 cu. yds. per shovel. The good record made by the smaller shovels as compared with the larger shovels was largely due to the fact that -they were given the easiest material to handle, so that no conclusions can be drawn as to relative efficiencies of the respective shovels. METHODS COSTS CHICAGO DRAINAGE CANAL. 241 This remark will also hold true of most of the data that follow. The material was loaded in 3-cu. yd. Peteler dump cars, hauled on a down grade in trains of two cars by two horses to the foot of the incline and hoisted up the incline by a Lidgerwood 12^ x i6-in. double drum engine, or by a 13 x Fig. 35. i6-in. double drum Webster, Camp and Lane engine. Fig. 35 shows one of these inclines. It was found that 750 ft. was the limit of economic haul from the shovel to the foot of each incline. Hence the glacial drift was taken out of the canal for a stretch 1,500 ft. long before moving the incline. Fig. 36 shows the track arrangement. 242 ROCK EXCAVATION METHODS AND COST. For Section 3 the track layout is shown in Fig. 37. A Mundy 6o-H. P. hoisting engine hauled two 3-01. yd. cars at a time up the incline, and a team of horses then hauled the cars to the dump. A team can haul 4 to 6 empty cars Method Glacial Drift. * of Working Rock. ^DgjSJsSzsljC Fig. 36. , *rt " Dec Jan Feb Mar The small size of skip load is due to the large size of the pieces. It will be seen from the above tabulation that from w bc- S en cii ^A (U ^ ro 6 J Pi in u 6" 6^ 82 9 37 138 333 1-30 9.5 99 9 62 197 338 1-43 9.62 70 9 28 102 293 1-33 8.37 92 10 91 I4O 345 1.50 9.86 METHODS COSTS CHICAGO DRAINAGE CANAL. 249 2 to 3 hrs. were lost through delays during each lo-hr. shift for the four cableways, or an average of nearly 40 mins. each lo-hr. shift for each cableway. Other records bear out this ratio, as on Section 7 where for one cableway the aver- age delay per lo-hr. shift was 1.08 hrs. for a 3 mos. run, and on Section 8 a similar average was 1.12 hrs. lost per shift. In these cases cableways were not working night shifts, so that the conditions were favorable. The Lidger- wood Manufacturing Co. calls attention to the fact that the delays are due to two items : ( I ) Delay for repairs to cable- way; (2) delay due to water in the pit, absence of rock ready to load, and the like. The first item, they claim, is generally about one-quarter of the entire delay, and they enumerate such items as the following: Door ring leaked during the night and boiler had to be refilled ; bolt broke in dumping device ; main cable sheave broke ; dump line broke ; dump line and hoist line tangled ; box of tower sheave broke ; button line broke. In this way nearly 13 hrs. were lost one month, while 16 hrs. more were lost waiting for stone on Section 7, where due to these delays and others the average output for the month was 403 cu. yds. per shift worked, or 476 cu. yds. per 10 hrs. actually run; and the month follow- ing the output was 462 cu. yds. per shift worked, or nearly 500 cu. yds. per 10 hrs. actually run. On Section 7 nine skips and about 35 men were worked on a face. About 1^/2 tons of coal, costing $2 per ton, and 25 cts. worth of oil were consumed per shift. According to official report the average output of one cableway for sev- eral months was 332 cu. yds. per lo-hr. shift, but the con- tractors give an average output of 394 cu. yds. per lo-hr. shift for three months (Jan., Feb., Mar., 1895), the average skip load being 1.87 cu. yds., and the average lo-hr. output of each man loading skips being 10.1 cu. yds., assuming 35 men to have been the loading force. As a matter of f.ict, they worked only 9-hr, shifts, but for sake of uniformity the output has been reduced to a lo-hr. basis. The average 250 ROCK EXCAVATION METHODS AND COST. lost time was 13 per cent, in Jan., 12 per cent, in Feb. and 6 per cent, in March. On Section 8 a row of 20 holes is drilled 8 ft. back from the face, and 8 ft. apart, each hole being loaded with 15 Ibs. of 40 per cent, dynamite, breaking 28 cu. yds. of solid rock. As a consequence of this close spacing of holes, the rock was loosened in smaller sizes, and each skip load was correspond- ingly increased. Nine skips and 40 men loading were em- ployed on each cableway. Locher, Harder & Williamson have furnished the following records for their two cable- ways for the first three months of 1895 : tfl ~ ex 3 Jan ........ 10,485 17,475 80 37* 52.5 Feb ........ 6,869 14,809 63 30* 51-9 Mar ....... 8,180 13,491 64 30^ 44.2 The January record on this section is excellent and shows what may be done where the plant is well handled and the rock well broken up, so as to reduce the delays arising from handling large rocks with grab hooks. The average skip load, it will be seen, was 1.8 cu. yds. It should also be noted that if the average force of loaders did not exceed 40 men, each man loaded nearly 11^2 cu. yds. per 9-hr, shift. Hullett-McMyler Cantilever Crane, or Conveyor. This machine resembles the Brown cantilever crane, but instead of spanning the canal it reaches only to the center. Indeed, as first made it was designed to overhang the canal bank but 10 ft., and was then used to receive its skip load from a McMyler locomotive crane running on a track in the bot- tom of the canal ; but this arrangement did not prove suffi- ciently efficient. Fig. 41 shows the general design of the Hullett-McMyler cantilever crane in its final form ; and Fig. * Jan., all g-hr. shifts; Feb., half 9-hr., half xo-hr. shifts. METHODS COSTS CHICAGO DRAINAGE CANAL. 251 252 ROCK EXCAVATION METHODS AND COST. 42 shows the arrangement of two such cranes working on opposite sides of the canal. The skip is of steel and has a capacity of 3.7 cu. yds. water measure, or i^g cu. yds. of solid rock. A 9 x 12-in. engine, working under 80 Ibs. pres- sure and with 200 revs, per min., does the hoisting. The total weight of the crane is no tons, and its cost is given at about $9,000. Fig. 42. Only two of these cranes were used on the canal (on Sec- tion 7). The daily (lo-hr.) expense of operating each was: i engineer $2.50 i fireman 1.50 Machinist service i.oo Superintendence 75 i y\ tons coal 2.50 Oil and waste 25 Repairs (?) 50 Track maintenance 1.50 Night watchman 50 Total $11.00 The two cantilever cranes handled 168,470 cu. yds. solid rock in 337 lo-hr. shifts, or 250 cu. yds. per shift per ma- chine. Hullett-McMyler Derrick. These derricks were at first placed in the bottom of the canal, but were afterward en- METHODS COSTS CHICAGO DRAINAGE CANAL. 253 larged and placed on the berm, Fig. 43. No locomotive crane had ever before been made with so long a boom. The der- rick handles a skip weighing 2,400 Ibs., making, with its full load of i^s cu. yds. solid rock, 3^ tons loaded. The ma- chine was designed to handle safely a load of 10,000 Ibs. The derrick weighs 95 tons, and its cost is given at $15,000. Fig. 43- A cranesman, a fireman, a man to trip skips, 3 laborers hook- ing and unloading skips, 25 loaders and a foreman con- stitute the crew for each derrick. The cost of operation is practically the same as for the Hullett-McMyler conveyor. In the pit 3 men were busy hooking and unhooking skips of which there were 5 or 6 to each machine. The highest daily output of which record is given was made Mar. 18, 1895, when 605 skips, or 980 cu. yds., of solid rock were conveyed in 10 hrs. by the two machines. To load this rock 254 ROCK EXCAVATION METHODS AND COST, there were 59 laborers in the pit, so that each man handled 1 6.6 cu. yds. that day. All told, these two conveyors moved 279,300 cu. yds. in 492 lo-hr. shifts, averaging 568 cu. yds. (284 cu. yds. each) per shift. Geraldine Double-Boom Derrick. Four of these derricks were used on the canal, the general appearance of each being shown in Fig. 44. The derrick revolves on a turntable, hav- ing a rack 28 ft. diam. in which two pinions mesh and are Fig. 44. rotated by two 8 x 8-in. vertical engines. The apex of the tower is 113 ft. above the track. The booms are 155 to 164 ft. long, and each boom carries two fall blocks for lifting the skips. While one boom overhangs the canal the other overhangs the spoil bank. As soon as two skips are hooked on in the pit the engineman begins to raise them, and at the same time to swing the derrick. The skips upon reaching a certain height are dumped automatically. Hoisting is then stopped, while the opposite skips, which have been lowered, are unhooked and loaded skips hooked on. Twelve skips holding 2 cu. yds. each are used. The cost of operation is : METHODS COSTS CHICAGO DRAINAGE CANAL. 255 50 laborers at $1.50 $75- 2 foremen 6.00 i engineman 2 -5 1 fireman 1-5 2 trackmen 3- 2 tons coal 4- Oil, water, watchman and supt 5.00 Total $97.00 The output of four derricks for 5 mos. ending July, 1895, was 300 cu. yds. solid rock per derrick per lo-hr. shift, which would indicate that there were many delays, since if 50 men were engaged in loading the 300 cu. yds. the average per man must have been only 6 cu. yds. The best average for any one of these derricks for one month of this time was 439 cu. yds. per lo-hr. shift. The Brown Cantilever Crane. The cantilever crane manu- factured by the Brown Hoisting & Conveying Co., of Cleve- land, Ohio, had been used for many years for handling iron ore, coal, etc., along the Great Lakes and elsewhere, so that its success on the Chicago Canal might have been regarded as a foregone conclusion. However, the output of this de- vice and its general efficiency far exceeded expectations. Al- together eleven of these cranes were used on the canal, and after the first year a monthly output of 15,000 to 16,000 cu. yds., or 600 cu. yds. per lo-hr. shift per crane, was attained ; in fact, for a week one crane handled 892 cu. yds. per 10- hr. shift, or 4,845 cu. yds. Fig. 45 shows the general de- sign of one of these cantilever cranes. The cantilever trusses have .a slope of 12^ and are 355 ft. from end to end. A carriage or trolley travels along the track on the lower chord of the truss, the hoisting power being a 10^2 x 12-in. engine and a I2O-H. P. boiler. The skip can be dumped automat- ically at any point of its 343 ft. travel. The weight of the entire machine is 150 tons, and its cost about $28,000. Each skip has a capacity of 75 cu. ft. water measure, and carries ROCK EXCAVATION METHODS AND COST. METHODS COSTS CHICAGO DRAINAGE CANAL. 257 1.5 to 1.7 cu. yds. of solid rock. The average traveling speed of the skip is 150 ft. per min., although the maximum speed is 400 ft. per min. On Section 10 the contractors, E. D. Smith & Co., have furnished the following record of output for the month of March, 1895, for one crane working in the lower lift, using 9 skips : Number of lo-hr. shifts 25 Output per shift, cu. yds 520 Number of laborers on the face 48 Output per laborer per shift, cu. yds 10.4 Av. skip load of solid rock, cu. yds 1.6 There were two foremen, one crane engineer, one fire- man, one oiler for crane and one towerman or operator ; 2 to 2 l / 2 tons of coal were burned per shift. Mr. C. L. Harrison, the division engineer, gives the output of three cranes on this section for six months of 1895 (Feb. to July inclusive) as having been 205,900 cu. yds. in 421 shifts (io-hr.), or near- ly 490 cu. yds. per crane per shift; during the month of April the average output for each of the three cranes was 542 cu. yds. On Sections n, 12 and 13 there were eight cantilever cranes operated by the manufacturers, who sublet the con- veying of the loaded rock. These cranes handled 2,084,700 cu. yds. of solid rock in 3,609 shifts (io-hr.), or very nearly 500 cu. yds. per crane per io-hr. shift. In the first 12 months (Feb., 1894, to Jan., 1895) the average output was 485 cu. yds. per crane per io-hr. shift and 10.9 cu. yds. per man loading skips. The lost time per crane per io-hr. shift for one month, of which record is given, was about 2 hrs., of which about l / 2 hr. was due to the crane and the other iy 2 hrs. to the failure of the contractors to have stone ready to load, which is probably a fair average. In Dec., 1895, these eight cranes working one 9-hr, shift a day averaged 60.5 cu. yds. per hour. For the 12 mos. each of these eight cranes averaged 23 shifts a month; in mid-winter working 9-hr. 258 ROCK EXCAVATION METHODS AND COST. shifts, and in mid-summer n-hr. shifts, although the records have all been reduced to a lo-hr. shift unit. The daily cost of operating each crane was as follows : Engineman $3-OO Fireman 2.50 Oiler 1.75 Operator 2.75 i 2-3 tons of coal at $1.75 3.00 Oil, water and waste (estimated) 50 Laying track (estimated) 50 Total $14.00 It will be seen that the conveying cost about 3 cts. per cu. yd., not including plant rental. No other method of convey- ing equaled this in point of low cost of operation, and it should also be noted that track had to be laid along only one berm of the canal ; but, on the other hand, the price charged for a cantilever crane was considerably in excess of that charged for any other machine. If $28,000 represents the price of each crane and 260,000 cu. yds. of rock were handled by each crane, obviously the contractor would be compelled to charge nearly n cts. per cu. yd. against the crane, unless he could be sure of a definite salvage price for the crane at the end of the job. Considerations of this kind are too often overlooked by engineers in estimating the unit cost of work. Cost by Car Hoists. For conveying rock in dump cars there were three methods used : No. I, the fixed incline with spur tracks ; No. 2, the natural incline with a loop track, and No. 3, the double-hoist and diagonal incline. Method No. i. This method was used on Sections 8, n, 12, 13 and 15 of the canal. A number of spur tracks were laid in the pit up to the rock face, and a number of spurs were laid on the dump, no spur being over 150 ft. long, and all connecting by switches with the main track, which led up a fixed trestle incline. This incline had a slope of 30, 40 ft. of it being in the canal prism and 85 ft. up on the berm. METHODS-COSTS CHICAGO DRAINAGE CANAL. 259 A hoisting engine was located at the head of the incline. Single cars (of which there were 8), each holding I cu. yd. solid, were loaded by hand, hauled by a mule to the foot of the incline, hoisted by the engine and hauled by a mule to the dump. The average haul (one way) from pit to dump was about 600 ft. The pit force was 40 to 45 men loading, I water boy, I mule and driver, and I foreman. The dump Fig. 46. force was I hoist engineer, I hoist runner, I mule and driver, and 4 dumpmen. The incline was torn down whenever it had to be shifted. Method No. 2. On Section 10 the upper lift was taken out by a car hoist method that differed from all others in that 260 ROCK EXCAVATION METHODS AND COST. there was only one (3-ft.) gage track on the dump, a loop in the pit and practically no trestling on the incline. The empty cars descended by gravity around the loop, as shown in Fig. 46; and one incline served two working faces. The wedge of earth and rock which was left to support the track on the incline was removed in carts after the incline had served its purpose and had been moved. The main track on the in- cline was 150 ft. long; at a distance of about 75 ft. back from the canal it branched, the two tracks coming down over the berm and meeting at the far side of the canal, forming a loop 375 ft. long. This method of track arrangement gavt a very short haul and the track was easily maintained. There were 3 trains of 4 side-dump cars each, two being loaded, while the third was at the dump; and each car held i l / 2 cu. yds. of solid rock. When a train was loaded the cable was attached and it was hauled up the incline. The pit force con- sisted of 35 loaders, I water boy, I cableman, I switchman and i foreman. The dump force was i hoist engineer and 4 or 5 laborers. ; ng ~~~ . >* {steam Drills * Method No. 3. Double Hoist and Diagonal Incline. This was the only car hoist method used for all three lifts. A double track trestle incline entered the pit diagonally not at right angles with the canal, like other inclines. The two working faces were also diagonal, making an angle of 30 with the canal, thus giving a longer loading line. The track layout is shown in Fig. 47. There were two parallel main tracks on the incline trestle, each 150 ft. long; then each track was 300 to 800 ft. long in the pit and 600 to 1,000 ft. on the bank. The average haul was about 700 ft. Two trains of 12 cars each were used on each face, so that there METHODS COSTS CHICAGO DRAINAGE CANAL. 261 was no delay in loading. There were sidings in both pit and dump. Each car held l / 2 cu. yd. of solid rock. A double- drum hoisting engine handled two cables, one for each track. The pit force working two faces consisted of 75 loaders and edgers (i sledger to 6 loaders), 3 teams, 2 water boys and - foremen. The dump force was I hoist engineer, i firemen, 3 teams and 10 dump men. Summary of Costs. The summary in Table XXXII. has been compiled by Mr. W. G. Potter. The wages for the dif- ferent classes of workmen are given elsewhere in this chap- ter, common laborers in all cases receiving $1.50 for 10 hrs work, all delays of i hr. or more being docked. The tabu- lated costs do not include shop repairs, but do include field repairs. The drilling item appears not to include the cost of drill sharpening. Plant rental is not included either a very important item where such expensive machines are used. Ex- plosives include caps and dynamite, 12 cts. per Ib. for the 40 per cent, dynamite being assumed to cover the cost of explosives. General expenses include superintendence, watchmen and incidentals. The three methods of car hoist, Nos, i, 2 and 3, have been described in the pages just pre- ceding. TABLE XXXII. COST IN CENTS PER Cu. YD. (SOLID). ! . * i t I I lilt I ! x - xS^ (J x WO Brown Cantilever ---- 3.9 4.1 8.O 3.2 i.o 3.6 14.6 o.o 38.3 Lidgerwood Cableway. 3.7 3.8 8.4 2.7 i.o 3.6 15.6 o.o 38.8 Hullett-McMyler Der- rick ............. 3.9 4.0 7.4 2.5 1.8 5.3 18.3 o.o 43.2 Hullett Conveyor ..... 4.1 3.7 8.5 3.8 1.2 6.2 21.4 o.o 48.9 Car Hoist No. i ...... 3.7 3.9 9.1 2.7 0.8 3.1 24.8 5.1 53.1 Car Hoist No. 2 ...... 3.9 3.6 8.9 3.2 0.9 1.2 22.9 2.3 47.1 Car Hoist No. 3 ...... 4.0 5.0 10.7 3.1 1.2 1.2 26.4 4.8 56.5 262 ROCK EXCAVATIONMETHODS AND COST. TABLE XXXIII. o >< ffi , ts 3 o cj ^ a Brown Cantilever Lidgerwood Cableway . . Hullett-McMyler Derrick Hullett Cantilever Hullett Conveyor Car Hoist No. I Car Hoist No. 2 Car Hoist No. 3 Double Boom Derrick... St. Paul Derrick.. 10 443,750 478 10.45 8 600,725 397 10.25 7 180,406 217 8.52 7 109,397 235 9.91 9 178,839 335 6.85 8 131,674 285 6.96 10 60,341 269 6.98 9 308,531 463 6.82 14 324,880 282 8.22 14 63,700 153 8.22 Cost of Channeling. Channelers had never been used on canal excavations before the building of the Chicago Canal. The object in using them on the canal was to secure smooth side walls that would offer little resistance to the flowing water. The limestone varied widely in hardness, the upper lift being as a rule much easier to channel than the lower lifts. There were three lifts of 12 ft. each, and the channel cut was offset 6 ins. at each lift. Naturally the lower lifts were somewhat shattered by the blasting of the upper lift, adding to the difficulty of channeling. The average weight of a channeler was 11,000 Ibs. ; it moved back and forth on a section of track 30 ft. long, striking 250 blows per min. The width of the channel cut by the bit was 2% ins. at the top, decreasing y% in. for each 2 ft. of depth. The speed of channeling was 130 to 200 sq. ft. per 10 hrs. on the upper lift, and about half as much on the second and third lifts. There were 53 Sullivan and 33 Ingersoll channelers. The following are records of efficiency : METHODS COSTS CHICAGO DRAINAGE CANAL. 263 Sullivan Channeler. No. 101. No. in. June, Jam, June, Jan., 1893. 1894. 1893. 1894- No. hours worked 205 222 209 299 Sq. ft. channeled 2,783 1,401 3,076 1,683 Av. sq. ft. per hour 18.4 6.3 14.2 5.6 Max. sq. ft. per day 30O 1 126" 357 2 96* Min. sq. ft. per day 90 i8 3 63' I2 3 1 lo-hr. day; 2 n-hr. day; 3 9-hr. day. Labor troubles in June reduced the number of shifts worked, but the work was done on the top lift under the most favorable conditions. The work done in January was under the most unfavorable conditions, on the third lift, with ice and snow, frozen water pipes, etc. ; and 5 night shifts were worked with No. in. The time (hours worked) is that for which the men were paid, and includes all time lost for repairs and delays. The labor and fuel expense of running a channeler was as follows per day : i runner $ 2 -75 i helper 1.50 i fireman 1.75 Blacksmith and teams hauling drills 70 Superintendence and machinist 1.30 1 1 /4 tons coal 2.50 Total $10.50 The Ingersoll-Sergeant Drill Co. has furnished the follow- ing record of work of 5 channelers for the month of May, 1894, working on the top lift: The average cut by each ma- chine for 27 working days was 2,279 s( l- ft- or 121 sq. ft. per day. As high as 221 sq. ft. were cut by one machine in a day, and the best of these 5 channelers averaged 148 sq. ft. a day for the month. The cost of operation was : i runner $3oo i helper 1.50 i fireman .- 1.75 264 ROCK EXCAVATION METHODS AND COST. Coal $3.00 Blacksmith, machinist 1.50 121 sq. ft. at 8.9 cts $10.75 For an excavation 160 ft. wide the cost of channeling, at this rate, was slightly less than 3 cts. per cu. yd. These figures, however, apply only to firm limestone in the top lift, and 30 to 50 per cent, should be added to this cost for the lower lifts. Seven channelers on Section 9 working 7 mos. in 1894 averaged 94 sq. ft. each for the three 12- ft. lifts. Lewis gives the cost of channeling on Section 3 as being 7 cts. a cu. yd., which would be equivalent to about 20 cts. a sq. ft. Engineering -News gives the average for the whole canal work as 8 to 10 sq. ft. an hour at a cost of 8 to 25 cts. a sq. ft., and places the average cost at about 17 cts. a sq. ft., or 6 cts. a cu. yd. of rock excavated. Mr. W. G. Potter gives the following data for Jan. i, 1894, to Feb. i, 1895, on ten sections: Section Sq. ft. iJays Cost per Sq. ft. ( 10-hr.). sq. ft. per day. No. 7 98,043 1,170 11.73 cts. 83.80 No. 8 (ist lift).. 42,000 300 7.50 " 140 No. 8 201,558 2,339 ii. 10 " 86.2 No. 9 182,167 1,992 12.16 " 91.4 NQL 10 202,192 2,638 11.81 " 76.6 Time is actual working time, all delays of i hr. or more deducted. Shop repairs are not included. Wages per 10 hrs. were: No. 7. No. 8. No. 9. No. 10. Channelerman $3-OO $3-25 $3-25 $2-75 Fireman 1-75 i-75 i-75 1-75 Laborer 1.50 1.50 1.50 1.50 Team (occasional) 3-5Q 3-5O 3-5Q 3-5 Foreman (for entire sec.) 2.75 2.75 2.75 Coal, oil and waste 1.75 2.25 2.25 1.75 Cost of Drilling. Compressed air was used on 9 out of 15 sections of the canal. The common installation was a large compressor located at the center of a section, delivering air METHODS COSTS CHICAGO DRAINAGE CANAL. 265 at 80 to 90 Ibs. pressure. An 8 or lo-in. main led to the canal berm and there branched, a 6 or 8-in. main going each way; 2-in. feed pipes, 175 to 230 ft. long, supplied three drills. The common size of drill was one with a 3^4 x 6*^- in. cylinder, and a 2-ft. feed screw; + an< ^ X-bits were used, the X-bit being better. For a 12-ft. hole the starting bit was 2 ins. diam. According to W. G. Potter the expense per drill per ic-hr. shift was about as follows: Steam. Air. Drill runner $2.00' $2.00 Drill helper 1.50 1.50 Vs fireman 50 (air) 1.50 Coal and oil 1.25 (oil) .10 Total $5.25 $5.10 On Section 9 the daily average for 6 mos. was 82 ft. of hole per drill for each of 15 Ingersoll-Sergeant drills; each hole being 12 ft. deep. Holes were spaced 6 to 12 ft. apart ; close spacing decreasing the cost of sledging,* but increasing the cost of drilling. Many grades of dynamite were tried, but finally 40 per cent, was found to be the best. The higher grades shat- tered the rock in the immediate vicinity of the holes, but threw down chunks that were too large to handle. The sticks of dynamite were 1^2 x 6 ins. in size, weighing 4 Ib. each ; and 10 to 25 sticks were charged in a hole, thus con- suming 0.6 to 1.2 Ibs. of 40 per cent, dynamite per cu. yd. Including fuse and caps the dynamite averaged about 12 cts. per Ib. Steam Shovel Output. Steam shovels were not much used for loading rock, as their average output was small. On Section 15 a 20- ft. face was worked, and 5-cu. yd. cars were loaded by two Bucyrus (55-ton) shovels with broad, shallow dippers having a capacity of 2^4 cu. yds. Cars were hauled in trains of 10, one locomotive serving each 266 ROCK EXCAVATION METHODS AND COST. shovel. The best record made by one shovel was 600 cu. yds. in 10 hrs. The combined output of these two shovels was as follows: Cu. Yds. No. of 10-hr. per Shovel Total Cu. Yds., 1895. Shifts. per Shift. Solid Measure. May 109 266 29.000 June 99 291 28,850 July 96 302 29,000 Aug 102 310 31,800 The average per shovel per month was 14,700 cu. yds., working two shifts a day. CHAPTER XIV. COST OF TRENCHES AND SUBWAYS. General Considerations. Trenching in rock is a subject upon which practically nothing has ever been written. In consequence there is probably no class of rock work that is so often mismanaged ; and, as a further consequence of the prevailing ignorance, engineers' estimates of cost are often far too low -and occasionally as far too high. In city specifi- cations for sewer trenching in rock it is customary to pay the contractor only for rock excavated within specified "neat lines." If he excavates beyond the "neat lines" he does so at his own expense. In sewer work the most common practice is to specify that payment will be made for a trench 12 ins. wider than the outside diameter of the sewer pipe, and 6 ins. deeper than, the bottom of the pipe when the pipe is laid to grade. A specification should always name a mini- mum width of trench. Some specifications allow for a side batter of 3 ins. to the foot on each side ; but unless the trench is to be deeper than can be drilled with one set up of the ma- chine drills, and requires excavation in more than one lift or bench, I see no reason for prescribing a batter to the rock sides. The most rational specification that I have seen for general use in rock trenching is as follows: "All trenches in rock excavation will be estimated 2 ft. wider than the external diameter of the pipe and 6 ins. below the sewer grade." Specifications vary so widely as to the "neat lines" that bidding prices for trench work under different engineers are very deceiving to any one who has not studied the par- ticular specifications covering the work upon which the bids were made. Different rocks vary greatly in the way the sides and bot- 267 268 ROCK EXCAVATION METHODS AND COST. torn shear off upon blasting. The sides of trenches in soft rocks can be cut off clean when the blast holes are properly loaded; but tough granites, traps, etc., leave jagged walls, generally involving excavation beyond the "neat lines" spec- ified. In excavating thin bedded, horizontally stratified rocks the drill holes seldom need to go much, if any, below the neat lines; that is, 6 ins. below the bottom of the pipe. But in excavating thick bedded and tough limestones and the like, it is generally necessary to drill 12 ins. below the bottom of the pipe. In tough granites, traps, etc., it is often necessary to drill at least 18 ins. below grade in order to leave no knobs or projections after blasting that would re- quire breaking off with bull points and sledges. Obviously the shallower the trench the greater is the importance of making due allowance for this extra drilling. If a trench is only 3 ft. deep and it is necessary to drill I ft. below grade, then 33 per cent, must be added to the cost of drill- ing to grade in order to cover the cost of the extra drilling below grade; but if the trench is 10 ft. deep, then only 10 per cent, of extra drilling is required. I have known cases where engineers have lowered the grade about 6 ins. after a long stretch of rock trench had been completed, and have required the contractors to do this 6-in. skimming at the regular price per cubic yard! As a result, it has cost the contractor several times what he received for the work. In such cases the engineers have generally been ignorant of the actual cost of trench work ; for otherwise they doubtless would have allowed an extra price. Charging the Holes. In tunneling, the explosive is most effective if placed in a pocket at the end of the drill hole. In narrow trench work, on the other hand, the explosive should be distributed all along the hole, leaving only enough length for the least possible amount of tamping. To one who gives the matter thought the reason is obvious, yet I have seen contractors actually "springing" holes in a hard limestone trench, and thus wasting much labor and powder. COST OF TRENCHES AND SUBWAYS. 269 Contractors often take out deep trenches in several benches, simply because they think it necessary to place all the charge together. As a matter of fact a trench 25 ft. deep, or as deep as the machine will drill, can be taken out in one lift. To do this the explosive is separated into several charges in the hole, tamping being placed between the charges. Where charges are separated in this manner firing should never be done with a fuse, but always with a battery. On page 204 I have described a method of charging- alternate sticks of dynamite and wood plugs, the firing of the top stick sending all the others off. In a city this method could probably not be used with safety because of the danger at- tending such heavy blasting. Use of a Blasting Mat. For preventing accidents due to flying rocks all blasts in cities should be covered either with timbers or with a blasting mat. This should be done to avoid suits for damages, regardless of city ordinances. A blasting mat is readily made by weaving together old hemp ropes, i l / 2 in diam. or larger. To make such a mat, sup- port two lengths of i-in. gas pipe parallel with one another and as many feet apart as the width of the mat is to be. Fasten one end of the rope to one end of the pipe; carry the rope across and loop it over the other pipe; bring it back around the first pipe ; and so on until a sufficient number of close parallel strands of the rope have been laid to make a mat as long as desired. Starting with another rope, weave it over and under, like the strands in a cane-seated chair, until a mat of criss-cross ropes is made. Such a mat, weighted down with a few heavy timbers, will effectually prevent small fragments from flying at the time of blast- ing. The mat and its ballast may be hurled into the air sev- eral feet, upon blasting ; but it will serve its purpose by stop- ping the small pieces of rock which are so dangerous even where light blasts are fired. The mat should be laid directly upon the rock. Such a mat will save a great deal of labor involved in laying a grillage of timbers over a trench. It 270 ROCK EXCAVATION METHODS AND COST. will also make it unnecessary for the blasters to stand far from the blast when firing. Cost of Drilling and Blasting. Next to tunneling there is no class of rock excavation requiring so much drilling per cubic yard as does trench excavation. In granites, if shallow holes are drilled by hand, the holes are frequently spaced not more than i l / 2 ft. apart. If in a very narrow trench i l /> ft. wide two holes are drilled in a row, one on each side of the trench, and if the rows are i l /2 ft. apart, we have two holes drilled in a square i l / 2 ft. on a side; that is, for every 2*4 cu. ft. of rock we must drill 2 ft. of hole, or 24 ft. of drill hole per cu. yd. If the cost of drilling is 25 cts. a foot, we have 24 X -25 = $6 per cu. yd. as the cost of drilling alone. It is seldom, however, that such narrow trenching is done. Trenches for small pipes are usually 2^2 to 3 ft. wide; two holes are then drilled in a row, and rows are usually about 3 ft. apart. A trench 3 ft. wide with two- holes in a row, and rows 3 ft. apart, requires 6 ft. of drill- ing per cubic yard. With drilling costing 50 cts. per ft., as it often does where hand drills are used in granite, the cost is then $3 per cu. yd. for drilling alone. Unless the job is too small to pay for installing a plant, hand drilling should never be used in trench work, because the drilling forms such a very large part of the cost. In a trench 6 ft. wide in hard trap rock three holes were drilled in a row, one close to each side and one in the middle, and the rows were 3 ft. apart, thus requiring 4^ ft. of drill hole per cu. yd. of excavation. The drilling was done with steam drills at a cost of 30 cts. per lin. ft., for the holes were only 4^2 ft. deep, the rock was hard, and the men slow, about 35 ft. being the day's work per drill. The contractor had to drill i^ ft. below grade in this rock to insure having no projecting knobs of rock. While it cost $1.35 per cu. yd. to drill the 3^2 ft. for which payment was made, to this must be added nearly 30 per cent., or $0.40 per cu. yd., to. cover the cost of drilling the extra I ft. for which no pay- COST OF TRENCHES AND SUBWAYS. 271 ment was received, making the total cost of drilling $1.75 per cu. yd. of pay material. About 2 Ibs. of 40 per cent, dynamite were charged in each hole, making about 2.6 Ibs. of dynamite per cu. yd. of pay material. The explosives thus added another $0.40 per cu. yd., making a total of $2.15 per cu. yd. for drilling and blasting. In the same trap rock, where the trench was 8 ft. wide and 12 ft. deep, there were three holes in a row and rows were 4 ft. apart, requiring 2.53 ft. of hole per cu. yd. of pay exca- vation, plus 0.21 ft. of hole per cu. yd. of pay material to cover the cost of drilling the last I ft. of hole below the ''neat line." Each drill averaged 45 ft. of hole in 10 hrs., and the cost was 23 cts. per ft. of hole ; hence, 2.74 X 0.23 = $0.63 per cu. yd. was the cost of drilling. About 4 Ibs. of 40 per cent, dynamite was charged in each hole, or i.i Ibs. per cu. yd. of pay material, making the total cost 80 cts. per cu. yd. for drilling and blasting. A comparison of this cost of 80 cts. with the $2.15 above given brings out strikingly the fact that each problem of trench work must be con- sidered in detail by itself. In a city where the contractor must shoot comparatively small shots in order to avoid accidents to buildings and suit^ for damages arising from "disturbing the peace," it is sel- dom possible to space the holes more than 3 or at most 4 ft. apart. In trenching in soft sandstone in Newark, N. J., where the trench was 14 ft. wide and 10 ft. deep, there were five holes in a row (the distance between holes being 3^ ft.) and rows were 4 ft. apart, making 2.4 ft. of hole per cu. yd. Each hole was charged with 4.12 Ibs. of 40 per cent, dynamite, making practically i Ib. per cu. yd. About half the dynamite is charged at the bottom of each hole, then tamping is put in, and the other half is charged up to about 2 l /2 ft. below the mouth of the hole. Each steam drill aver- aged 90 ft. of hole per 10 hrs., making the cost of drilling 10 cts. per ft. of hole, or 24 cts. per cu. yd. Including the cost of dynamite and the placing of timbers over each blast, 2 7 2 ROCK EXCAVATION METHODS AND COST. the cost of drilling and blasting was 40 cts. per cu. yd. This is probably as low a cost for breaking rock in trenching as can be counted upon under favorable conditions. In this rock there was no necessity of drilling below grade. I am indebted to Mr. F. J. Winslow for the following data on trench work in Boston, Mass. House sewer trenches are never less than 3 ft. wide, and trenches for water pipe (16 ins. or less) are 2 l /> ft. wide. The rock is granite, and the drill holes are usually 3 ft. apart. On small jobs hammer drills are used, one man holding and two striking. For a hole 10 ft. deep the starting bit is 2 l /2 ins. and the finishing bit is 1^4 ms - diam. A drilling gang of three men aver- ages 8 to 10 ft. of hole in 10 hrs., although in soft rock 20 ft. may be drilled in 10 hrs. Forceite containing 75 per cent, nitroglycerin is commonly used, */2 to 3 sticks being charged in a hole. Force account records for granite trenching show that the average cost during the past 15 years has been $3.80 per cu. yd., including excavating and piling up the rock alongside the trench. I am indebted to the Harrison Construction Co., of New- ark, N. J., for the following information: In a sandstone trench about 6 ft. wide the holes were spaced about 3 ft. apart, thus requiring 4^2 ft. of hole per cu. yd. In seamy rock, shallow holes 4 to 6 ft. deep were drilled, and from 2 to 3 sticks of 50 per cent, dynamite were charged, each stick being 1^2 x 8 ins. This is equivalent to 0.55 Ib. per cu. yd. Where the rock was solid, the holes were drilled 8 to 10 ft. deep and the dynamite charge doubled. The cost of throwing rock out of shallow trenches or of loading it into buckets to be raised by the engine of a der- rick, a locomotive crane or a cableway, is somewhat greater than the cost of handling rock in open cuts. A fair day's work for one man is 6 cu. yds. of rock loaded, when there is little sledging; but the output may be only 4 cu. yds. where there is a large amount of sledging to be done. If cableways or derricks are used for hoisting the rock, COST OF TRENCHES AND SUBWAYS. 273 bear in mind that they will be idle most of the time, for the drilling limits the output. With a given number of drills to a cableway, estimate the number of cubic yards of rock that the drills will break per day and divide this yardage into the daily cost of operating the derrick. Thus, in a trench 6 ft. wide, if the holes are 3 ft. apart, each cubic yard of rock requires 4^2 ft. of hole, and each drill will break 13 1 / 3 cu. yds. per day where 60 ft. of hole is a day's work. With four drills per cableway the daily output is 4 X 13 1 / 3 = 53 1 / 3 cu. yds. The cableway would be capable of handling sev- eral times this output were it not limited by the drilling. Notwithstanding that all this seems self evident, I have known more than one contractor to overlook the fact that the cost of handling rock from trenches is very much great- er than in open cuts where holes are farther apart and where a few drills can keep a cableway busy. In my book on earthwork I have given in detail the cost of operating a cableway on trench work, and elsewhere in this book will be found the cost of hoisting with derricks. Cost of N. Y. Subway Work. Aside from some data on the cost of subway work given in my book on earthwork, nothing, so far as I know, has ever appeared in print on the actual cost of subway excavation. By observation and through the aid of an assistant I have secured reliable data relating to every item of cost on several typical sections of the New York Rapid Transit Rv., including excavation, con- crete, steel construction, etc. ; and it is astonishing to find how high the labor cost of the work has been. The high cost may be attributed to several causes. In the first place, the contractors were compelled to employ union labor, much of which was inefficient. In the second place the foremen on this work were, as a rule, paid such small salaries that the best class of foremen were not kept. In the third place excavation and other work in crowded city streets is obviously made difficult; the sup- porting .of pipes, tracks, etc., adding greatly to the cost in certain parts of the city. In fact, in the lower part of New 274 ROCK EXCAVATION METHODS AND COST. York, where the material is all sand, I have found that 50 cts. per cu. yd. has been expended in shoring, bracing, etc. In the fourth place the light blasts required by city rules leave the tough mica schist in large chunks upon which much labor must be expended in gadding and sledging; for practically all the rock was broken to one or two-man size so that it could be hauled away in dump wagons. The work that I am about to describe involved the excava- tion of about 125,000 cu. yds. of tough mica schist in the upper part of the city, where the streets are not crowded and where there were very few pipes to be supported. The width of the excavation was 41 ft., and the depth averaged about 30 ft. One trolley track ran along the center of the street and had to be supported the entire distance. This track supporting was accomplished at comparatively slight expense by using some ten second-hand railroad bridge trusses of 66 ft. span, which were moved forward as the work progressed. Five cableways, each having an average span of 400 ft., were used for hoisting the rock in self- righting buckets, which were dumped into patent dump wagons. The average daily force employed was as follows : Rate per day. Total. 4 foremen $3-5 $14.00 80 laborers 1.50 120.00 10 drill runners 2.75 27.50 10 " helpers 1.50 15.00 2 blacksmiths 2.75 5.50 2 helpers .... 1.50 3.00 5 hoisters 3.00 15.00 I compressor man 4.00 4.00 1 fireman 2.00 2.00 2 timbermen 2.00 4.00 3 Waterboys 75 2.25 20 teams 4.50 90.00 Total per 8-hr, day $302.25 COST OF TRENCHES AND SUBWAYS. 275 The average output of this force was only 150 cu. yds. of rock per day ! Cost per Cu. Yd. Drill runners ........... $2.75 $0.174 , $0.150 Drill helpers ............ 1.50 .100 .082 Blacksmiths ............. 2.75 .032 .025 Blacksmiths' helpers .... 1.50 .018 .012 Compressorman ......... 4.00 .016 .014 Firemen ................ 2.00 .012 .014 Hoist enginemen ........ 3.00 .100 .051 Carpenters .............. 3.50 .008 .000 Timbermen ............. 2.00 .024 .000 Waterboys .............. 0.75 .012 .010 Laborers ................ 1.50 .785 .745 Foremen ................ 3.50 .102 .095 Teams (with drivers) .... 4.50 .620 .581 Total Wages ....... $2.002 $ 1.779 Cu. Yds. Excavated 125,000 7,600 To the foregoing must be added the cost of fuel, explo- sives, maintenance, interest and depreciation of plant, etc., as follows: Cost per cu. yd. Vso ton coke, at $4.50 ......... .......... $0.150 0.6 Ib. 40 p. c. dynamite, at 12^2 cts ....... -75 y> exploder, at 4 cts ..................... 0.020 Drill repairs (est'd at 50 cts. a day per drill) .034 Installing boiler and compressor ........... 014 Interest and depreciation (50 p. c.) of $7,000 boiler and compressor plant ............. 028 Ditto for $3,500 drilling plant ............. 014 Total supplies, etc ................... $-335 Add total wages ....................... 2.002 $2.337 276 ROCK EXCAVATION METHODS AND COST. To this sum should be added 3 or 4 per cent, to cover gen- eral expenses, such as office rent, bookkeeping, night watch- men, insurance on laborers, etc., which would bring the grand total to nearly $2.40 per cu. yd. of rock excavated. It will be seen by the description of the work and by the comparatively low cost of timberwork that the expense of supporting pipes and tracks was unusually low for such a city as New York. On the other hand, the cost of drilling was exceedingly high, being 28 cts. per cu. yd. for wages alone, if we include the blacksmiths' wages and half the wages of the compressorman and his fireman. The drills should be charged with about half the cost of the fuel, which adds J l / 2 cts. more per cu. yd., making 35^ cts. per cu. yd. for drilling, not including some 3^ cts. for drill repairs (estimated) and i l /> cts. for interest and depreciation. Add- ing these two items we have a total of 40 cts. per cu. yd. chargeable to drilling alone, which is exceedingly high for an open cut of this width and depth. It is a striking fact that each drill broke less than 15 cu. yds. of rock per 8-hr, day. The inefficiency of the laborers is also well shown by their output of less than 2 cu. yds. per man per 8-hr. day. It is true that they had to do a great deal of gadding, sledg- ing and hand drilling to break the rock ready to load into buckets ; but any one who saw the men at work must have been impressed with their slowness. The output of only 30 cu. yds. per day per cableway shows how the cableway out- put was limited by the drilling. The high cost of hauling is also noteworthy, for the average haul was but little more than one mile. While it was difficult to get union laborers to do a fair day's work, I think that if the contractors along the subway had in all cases employed civil or mining engineers of known experience in rock excavation, a great deal of money would have been saved. CHAPTER XV. SUBAQUEOUS EXCAVATION. Cost of Rock Excavation in the Detroit River. I am in- debted to Mr. Chas. Y. Dixon, U. S. Assistant Engineer, for the following data of cost, which were originally compiled by Mr. Harry Hodgman, and which, so far as I know, are the most detailed and complete cost records of subaqueous ex- cavation that have ever been published. In the Michigan Engineer, 1903, Mr. Hodgman gave a very complete descrip- tion of this work upon which he has been continuously en- gaged since 1895. From Mr. Hodgman's article and from Mr. Dixon's letters to me, I have compiled the following: The work was done under three contracts, as follows: At Ballards Reef, the Buffalo Dredging Co. ; at Lime Kiln Crossing, James B. Donnelly, of Buffalo, N. Y. ; and at Amherstsburg Reach, M. Sullivan, of Detroit, Mich. : At the mouth of the Detroit River it is usually necessary to drill and blast the material before it may be excavated. The drill boats in use are from 60 to 80 ft. long and from 25 to 30 ft. wide, and are held in position by four spuds, one at each corner. They are equipped with two or more Inger- soll steam drills supported on vertical frames having trucks to permit of the drills being moved horizontally along the edge of the boat. The drills are raised and lowered during the operation of drilling by hydraulic lifts. The boiler fur- nishes the steam for operating the drills, the pumps used in connection with the hydraulic lifts, the forge, the electric light plant and other machinery with which the ordinary drill 277 278 ROCK EXCAVATION METHODS AND COST. boat is equipped. The drill boat usually serves the purpose of a machine shop where repairs are made to the entire dredging plant. It is always conveniently near to all parts of the work, and ordinary repairs are quickly made, the con- tractor usually providing a great variety of tools and ma- chinery for use in cases of emergency. The drill boats are usually operated day and night. The holes (about 2*/2 ins. in diam.) are made at the corners of 5-ft. squares to a depth of about 3 ft. below the required depth, at the rate of about 5 ft. per hour per drill. The amount of explosive used is about one pound of 60 per cent, dynamite per linear foot of drill hole. The holes are charged by inserting the sticks of dynamite with the exploder and battery wires attached into the bottom of a long pipe, the battery wires leading out through a slit in the side of the pipe. This pipe is lowered into the drilled hole, the dyna- mite shoved down with a long ram rod, and the pipe with- drawn, a wire spring clamped to the dynamite stick pre- venting its coming out of the hole. The wires are then at- tached to the battery and the dynamite exploded. During this operation the drill boat is not moved, nor does the work of operating the other drills cease except at the time of firing. On two occasions, however, the charge of dynamite came out of the hole, and was exploded directly underneath the boat, causing it to sink almost immediately. This may be attributed to carelessness, however, as before exploding the dynamite the battery wires should be drawn up until taut, indicating that it is in place. A quantity of dynamite is al- ways kept conveniently near the work, but no more than one day's supply is kept at the drill boat, and this is stored in a small scow trailing off the down-stream end of the boat at a safe distance. The dredges used in excavating the material are of the type known as the dipper dredge. They vary in length from 80 to 135 ft. and in width from 30 to 40 ft., and are held in position by three spuds (36 ins, square), two at the bow and SUBAQUEOUS EXCAVATION. 279 one at the stern. The machinery for operating dredges varies greatly, the best recently-constructed dredges being equipped with machinery for raising the dredge on the forward spuds (known as pinning up) instead of by swinging the dipper as formerly. The dredge is moved forward in the cut by means of the dipper arm, and the width of the cut is usually from 15 to 20 ft. The capacity of the dredge dipper varies from 2 to 5 cu. yds. in rock work and from 4 to 7 cu. yds. for earth work. The amount of material removed by one dredge per hour varies from 20 to 100 cu. yds. in rock, and from 75 to 125 cu. yds. in earth. The best type of dredges, however, in soft earth and under favorable conditions are capable of removing from 250 to 300 cu. yds. per hour. The time delayed for repairs usually varies from one-fifth to one- third of the time actually worked. After the entire width of the area to be improved has been worked over by the dredge, cut by cut, the derrick scow fol- lows after to remove such loose pieces of rock as may have been left projecting above the required depth. The derrick scows are usually from 80 to 100 ft. long and from 20 to 25 ft. wide and they are equipped with an ordinary hoisting engine and derrick capable of lifting from 12 to 18 tons, and a complete diving outfit. When lifting the boulders, the derrick scow is pinned up and supported on two spuds, each about i ft. square. The material to be removed is found by means of an iron bar, about 30 ft. long, suspended from the side of the- scow to the required depth. Any obstruction struck by this bar as the scow is swept over the improved area is removed by the derrick by means of a chain, which is placed in position by a diver. After the area has been thus improved and cleared of ob- structions an examination is made on the part of the United States to determine if the required depth has been secured. This examination consists in sweeping the entire area with bars suspended to the required depth. These bars (about 20 ft. long) are suspended by chains from a raft (100 ft 280 ROCK EXCAVATION METHODS AND COST. long and 20 ft. wide) built of squared timbers, the raft being held in position by a rope leading to a head anchor and pulled back and forth by means of ropes leading to side anchors. Any obstruction found during this examination is removed by the derrick scow with diving outfit. During the progress of the work, as well as during this final examination, con- stant attention is paid to the water gage in order to allow for the fluctuations in the water surface. Following this examination and on the completion of the work required un- der the contract, the final survey is made, which survey con- sists in the taking of soundings at regular intervals as de- scribed above. On this final survey and on the original sur- vey depend the estimate for final payment. At Ballard's Reef the material excavated was limestone bedrock, clay, hardpan and boulders. Generally there was from one to two feet of loose material overlying the bed- rock. About 50 per cent, of the material was hardpan and clay. The material within about 75 per cent, of the area im- proved required to be drilled and blasted before removal. In this material one drill boat, equipped with three drills and working double shifts, was used to provide work for one dredge. At Lime Kiln Crossing the material was mainly limestone bedrock, with no overlying material. Within the entire area it was necessary to do drilling and blasting before dredging. In this material two drill boats (each equipped with three drills and working double shifts) were used to provide work for one dredge. At Amherstburg Reach the material was limestone bed- rock, clay and boulders. Generally there was from one to two feet of loose material overlying the bedrock. Within about 75 per cent, of this area it was necessary to do drilling and blasting before dredging. On this work two drill boats (each equipped with three drills and working double shifts) were used to provide work for two dredges continuously and for a part of one season three dredges, SUBAQUEOUS EXCAVATION. TABLE XXXIV. DREDGING DETROIT RIVER, 1900-1903. 281 Cu. yds. above 23 ft. depth (place measure) 74,143 101,072 98,332 Cu. yds., total (place measure) 135,548 121,707 209,821 Cu. yds., total (scow measure) !53,O97 168,633 Area dredged, sq. yds 225,000 61,000 225,000 Average depth dredged, pay material.... i ft. 5 ft. 1.3 ft. Average depth dredged, total exc 1.8 ft. 6 ft. 2.8 ft. Average depth of water over material 21 ft. 18 ft. 20.7 ft. Dredge hours, worked 7,248 3,945 9,021 Dredge hours, delayed 3,386 1,490 2,890 Dredge hours, total 10,634 5,435 12,91 1 Dredge months (i2-hr. days) 34 17.4 39 Cost per month $3,ooo $3,200 $3,200 'i otal cost $102,000 $55,720 $124,800 Cost per cu. yd. (place measure), pay material $1.38 $0.55 $1.27 Cost per cu. yd. (place measure), total exc $0.75 $0.46 $0.60 Average cu. yds. per hr., working time. .. . 19.0 43.0 23.3 Average cu. yds. per hr., total time 12.8 22.4 16.2 iViaximum cu. yds. per hr., soft material.. 150 250 200 TABLE XXXV. DRILLING. Worked Drill hours -I Delayed Total Number of holes drilled Number of feet drilled Ft. per hr., actual work Ft. per cu. yd., pay material.. Ft. per cu. yd., total exc Distance between holes Ballards Lime Kiln Reef. Crossing. 24,442 982 25,424 30,023 191,850 7-9 2.6 1.4 ft. 37,746 1,278 39,024 29,236 240,591 6-4 2.4 1.9 5 ft- Amherstburg Reach. 38,441 38,441 35,432 181,421 4-7 1.8 0.9 5 ft 282 ROCK EXCAVATION METHODS AND COST. Average depth of holes 6.2 ft. 8.2 ft. 5.1 ft. Average depth of pay material i.o ft. 5.0 ft. 1.3 ft. Percentage of drilling below pay depth 84.0% 37-5% 75-O% Number of pounds of 60% dynamite 110,305 222,396 263,672 Lbs. per cu. yd., pay material. 0.5 2.2 2.7 Lbs. per cu. yd., total exc.... 0.8 1.8 1.2 iotal cost of drilling $59,235 $105,245 $96,470 Per cu. yd., pay material $0.80 $1.04 $0.98 Per cu. yd., total exc $0.44 $0.865 $0.46 Per. lin. ft. drilled $0.31 $0.44 $0.53 Per drill hour $2.25 $2.69 $2.51 ITEMS OF COST. Ballards Reef. Lime Kiln Crossing. 25,424 drill hours at 39,024 drill hours at $0.80 $20,340 $0.80 $31,220 IT 0,305 Ibs. dynamite at 222,400 Ibs. dynamite at $0.15 i6,545 $0.15 33,36o 2,450 tons of coal at 3,555 tons of coal at $3-00 7,350 $3.00 10,665 Repairs (approximate).. 5,ooo Repairs (approximate). 5,ooo Miscellaneous supplies . 5,ooo Miscellaneous supplies . 5,ooo Depreciation of plant... 5,OOD Depreciation of plant... 5,ooo Tug service, 30 mos. at Total $59,235 $500 15,000 Tug service included in dredg- ing. Total $105,245 Amherstburg Reach 38,441 drill hours at 80 cts $30,750 263,372 Ibs. dynamite at 15 cts 395OO 3,740 tons of coal at $3 1 1,220 Repairs (approximate) 5,ooo Miscellaneous supplies (approximate) 5,000 Depreciation of plant (approximate) 5,ooo Total Tug service included in dredging. ,$96,470 Cost SUBAQUEOUS EXCAVATION. TABLE XXXVI. DERRICK Scows. 283 Ballards Lime Kiln Amherstburg Reef. Crossing. Reach. at $970 13.0 mos. 16.0 mos. 1 1.2 mos. at $970 at $970 $10,865 $12,610 $15,520 Tug service Tug service Tug service included in included in included in dredging. dredging. dredging. of area Cost per sq. yd. improved Cost, per cu. yd. of material removed by diver $0.0475 $573 $0.22 $2.84 $0.07 $2.04 SUMMARY OF COST. Dredging Drilling Derrick scows $102,000 59,235 10,865 $55720 105,245 12,610 $124,800 96,470 15,520 Totals $172,100 $173,575 $236,790 Cost per cu. yd. of pay material $2.32 $1.718 $2.41 Cost per cu. yd. of total excavation $1.27 $1425 $1.04 BASIS UPON WHICH ESTIMATES OF COST WERE MADE. Dredge Crew : Captain at $125 per month $125 Runner at $90 per month 90 Cranesman at $90 per month 90 Fireman at $55 per month 55 Deckhands at $40 per month 120 Scowman at $40 per month 40 Cook at $50 per month 50 Watchman at $40 per month 40 Total $610 284 ROCK EXCAVATION METHODS AND COST. Tug Crew : i Captain at $115 per month .............. $H5 i Engineman at $100 per month ............ 100 i Fireman at $55 per month ................. 55 i Deckhand at $40 per month .............. 40 Total .................................. $310 Subsistence of 14 men per month 210 tons of coal at $3 ...................... 630 Repairs and supplies per month ............ 500 Repairs at the end of season, per working month ................................. 500 Depreciation in value of plant per month of operation equals Y% of 10% of value of plant. DRILLING 3J/2 men per drill (at $2.50 per day of 11 hours) equals 80 cts. per drill per hour. DERRICK SCOW I foreman at $90 per month ................ $90 I -engineman at $85 per month .............. 85 i diver, 25 days, at $10 per day ............ 250 i diver's helper, at $75 per month ........... 75 6 deck-hands, at $50 per month ............. 300 15 tons of coal at $3 ....................... 45 Repairs and supplies per month ............ 50 Depreciation in value of plant ............. 75 Cost per month $970 Cost of Harbor Excavation, Oswego, N. Y. In Engineering News, Feb. 15, 1894, Mr. Wm. Pierson Judson gives the following data on rock excavation in the inner harbor of Oswego. N, Y. Over an area of 4,500 sq. yds. the rock had to be excavated to a depth of 15 ft. Over 70 per cent, of this area the rock had a face of i ft. or less, and over the rest the face was 2 ft. or less. The rock was gray wacke sandstone in horizontal strata i to 2 ft. thick, with seams in which the drill often jammed. The rock varied greatly in SUBAQUEOUS EXCAVATION. 285 hardness ; the drill often cutting 10 ft. with one sharpening, and at other times wearing dull in I ft. The rock excavated was 2,956 cu. yds., let to Kingston, Rogers & O'Brien at $2.75 per cu. yd., place measure. Work was begun June 30, 1893, with a very efficient plant. The drill scow was 6 l / 2 x 26 x 82 ft., the bottom being of 8-in. oak, and the sides of 6-in. pine, and after a season's work showed no ill effects from blasts fired directly under it in 12 ft. of water. Its draft was 2 l / 2 ft. A deck house 14 x 72 ft. housed boiler, engine and blacksmith shop. On one side of this house was a 6 l / 2 -ii. track carrying two drill frames each, one a separate truck that could be moved by two men operating a 5-ft. lever and ratchet engaging a 10- in. pinion on the truck shaft. Each drill frame carried a 5-in. Ingersoll drill, suspended from a 6-in. x 12-ft. hydrau- lic lift set vertically in the drill frame. The great value of this hydraulic hoist was that it could pull a drill loose in- stantly when stuck in a seam. These hydraulic hoists were operated by a duplex Blake pump with a 7^2-in. steam cyl- inder, 4^2-in. water cylinder and lo-in. stroke, working un- der 80 Ibs. steam pressure. Steam for the drills, pump and I5-H. P. hoisting engine was supplied by a 3O-H. P. boiler burning 1^2 tons of coal in a working day of 22 hrs. There were two crews of six men each, and a blacksmith and help- er with each crew. Range marks 10 ft. apart made it possible to locate a drill within i ft. of any desired spot. A 4^2-in. casing pipe was lowered and forced into the gravel overlying the rock. This pipe had a double T, 2 ft. above the bottom, to allow drill chips to escape. The pipe remained in position until the hole was drilled and charged. The drill steel is 26 ft. long, the upper 14 ft. being of i^-in. machine steel ; the next 10 ft. of i^-'m. steel, and the lower 2 ft. of 2-in. octagon steel with a 3/4" m - square cross bit tempered in a saturated solution of equal parts of sal ammoniac, salt and alum. Holes were drilled 2 to 4 ft. below grade, and spaced 5 ft. 286 ROCK EXCAVATION METHODS AND COST. apart in rows 5 ft. apart. The average depth of 1,000 holes was 5*4 ft. and the average time to drill each of these holes was i hr., although in rock free from seams a hole may be drilled in l / 2 hr., whereas in seamy rock 3 hrs. may be con- sumed. The maximum rate of penetration of the drill was I ft. in 4 mins. About 12 drills per 22 hrs. were sharpened. About 20 ft., or 240 Ibs., of 2-in. octagon steel for 6,000 ft. of holes. Dynamite (75 per cent.) in waterproof cases, 2 T / 2 x 18 ins., gave the best results. The cartridge is placed in an iron loading pipe, which hangs by a small tackle from the drill frame. When the bottom of the hole is reached, a plunger, which is within the loading pipe, is undamped and forced steadily down upon the cartridge, while the loading pipe is slowly hoisted. The plunger and loading pipe are next raised through the casing; then the casing pipe itself is raised 4 or 5 ft. from the bottom ; and in this position the charge is fired, one hole at a time, without moving the drill boat. From 2 to 6 Ibs., average 234 Ibs., of dynamite are fired in each hole. The entire time from the stopping of the drill to the firing, as just described, is 3 mins. in ordinary work, and often only i l / 2 mins. To shift the drill on its trucks 5 ft. lower the casing and start drilling a new hole takes about 2 mins. and can be done in I min. Fourteen holes 5 ft. apart can be fired from one setting of the drill boat. The rock is broken up into pieces of i to 2 cu. ft. each. Occasionally the dredge dipper brings up a rock too large to drop through the dipper. In such cases the dipper is rested on the dump scow, while a hole is drilled in the rock with a hand drill, loaded with l / 2 Ib. of dynamite, tamped with cotton waste and fired without injury to the dipper. The loading pipe, above mentioned, is worthy of descrip- tion. Its lower end is a 2^-in. pipe 3 ft. long, with a ^g-in. slot its full length. The upper end of this slotted pipe joins a i-in. pipe 22 ft. long, within which works a ^-in. plunger SUBAQUEOUS EXCAVATION. 287 27 ft. long, having a 2-in. head at its lower end resting on the cartridge. The leading wires from the cartridge pass out through the slot. A clamp at the upper end of the i-in. pipe holds the plunger until ready to use. The device is all of iron and works perfectly. While the exact cost to the contractors is not known, the following estimate is based upon 1,000 cu. yds. of rock, for which 1,650 holes, aggre- gating 8,660 lin. ft., were drilled in 33 days of 22 hrs. each : 33 days' wages of drill crew, at $31 $1,023.00 4,000 Ibs. of 75 p. c. dynamite, at 17 cts.. 680.00 1,800 exploders at 3 cts 54.00 49^ net tons of soft coal, at $3 148.50 42 1 / 3 gals, cylinder oil for drills, etc., at 30 cts 12.70 55 gals, kerosene for lanterns, at 12 cts. . . 6.60 260 Ibs. octagon steel, at 15 cts 39oo 55 Ibs. machine steel, at 4 cts 2.20 General machine shop repair bill 34oo Total, 1,000 cu. yds. ,at $2 $2,000.00 To dredge 1,000 cu. yds. required about 10 days' work of 10 hrs. each, costing, say, $500, making a total cost of $2.50 per cu. yd. of rock excavation, not including plant rental. While 1,000 cu. yds. were removed above grade, for which the contractor was paid, there was probably an equal amount of loose rock left below grade, for which, of course, no payment was made. Cost of Excavating Black Tom Reef, N. Y. In Farrow's Military Encyclopedia are given some valuable data on sub- marine rock excavation, from which I have abstracted the following relating to the excavation o'f Black Tom Reef in New York Harbor. Mr. W. L. Saunders was in charge of this work and designed apparatus which marked an epoch in submarine drilling and blasting. The work was begun May 2, 1 88 1, and was completed in 344 actual working days {35 days were lost by storms and 26 in equipping scow). 288 ROCK EXCAVATION METHODS AND COST. The drilling plant consisted of three 5-in. Ingersoll drills mounted on a platform supported by spuds ; a scow anchored alongside carried the boiler that furnished steam to the drills. The longest drill steel used was 28 ft. long, and the shortest, 16 ft. ; the starting bit was 3^4 in s. ; the finishing bit, 2^2 ins.; and 9 ft. of hole were drilled on an average with each bit before sharpening. The drilling shift was 10 hrs. long, one shift a day; and 20.8 ft. of hole per drill per shift was the average drilled in the mica schist, not includ- ing the penetration of some 6 ft. of sand and gravel over- lying the rock. Mr. Saunders invented an "ejector" which is a pipe surrounding the drill steel and through which water is forced to wash away the gravel and sand. 1,736 holes were drilled, 1,629 charged and 1,542 blasted; the average depth in rock being 10.17 ft. The distance between holes was 4 ft.; the area excavated, 32,100 sq. ft., and the rock removed, 5,136 cu. yds., place measure. The dynamite was 75 per cent., of which 20,461 Ibs. were used ; exploders, 1,844; drill steel, 395 Ibs. ; connecting wire, 77 Ibs. ; coal, 200 tons at $4.14; hose, $491 ; water, $500. For each cubic yard 3.44 ft. of hole were drilled, and 3.98 Ibs. of dynamite used. The cost of the plant was : Barge and equipment $6,640 Two drill floats 9,082 Alterations, machinery, etc 5*663 Total $21,385 The cost of drilling and blasting was : Cost per cu. yd. 3.98 Ibs. 75 p. c. dynamite $1.84 1.22 oz. steel 02 Coal and water 25 Labor (payroll, $26.76 per day) 1.79 Repairs, plant 31 drills 01 ejector pipes 05 SUBAQUEOUS EXCAVATION. 289 Repairs, hose $0.09 Wire and tape Ol Total $4-37 To this must be added the $1.95 per cu. yd. paid for dredging by contract. Cost of Undermining Flood Rock. This work is described in detail in Farrow's Military Encyclopedia, and while the method of undermining is not likely to be used again for harbor deepening, there are certain features that merit at- tention. Flood Rock was a Q-acre obstruction in New York Harbor, and under the direction of Gen. John Newton it was finally removed in 1885. Two shafts were sunk and 10 x 10- ft. drifts or galleries were run at right angles to one an- other, leaving pillars of rock 15 ft. square supporting a rock roof averaging 19 ft. thick, although in places it was only 10 ft. thick. In driving the drifts very small charges of rackarock were fired, one hole at a time, to insure safety from flooding through unexpected seams in the mica schist rock. Any seams encountered were plugged with cement. In driving the 10 x lo-ft. drifts, 6 Ibs. of rackarock and 12 ft. of drill hole were required per cubic yard. The total drifting was 21,669 ft- or 80,232 cu. yds., requiring 480,000 Ibs. of explosive. The pillars and roof (270,717 cu. yds.; were drilled and charged with 1.04 Ibs. of explosive per cu. yd. of rock, requiring 0.42 ft. of drill holes per cubic yard. The final charge in the pillars and roof was 240,400 Ibs. of rackarock and 43,300 Ibs. of No. i dynamite, in 11,789 drill holes in the roof and 772 drill holes in the pillars, or a total of 113,120 ft. of drill holes. The cost of the work and ex- plosives required in preparing for the final blast was $2.69 per cu. yd. of total excavation ; and the rackarock used in the final blast cost $106,510. The loading of the final charge (283,730 Ibs.) of explosives was done by 20 men working 8 to 12 hrs. a day for 70 days. Experiments had shown that a lo-lb. charge of No. I dynamite under water would ex- 290 ROCK EXCAVATION METHODS AND COST. plode another charge in a copper cartridge 27 ft. away, so that no electric connecting wires were needed between drill holes. The rackarock was loaded in thin (.005 in.) copper cartridges, which were soldered with a solder that was melt- ed with wet steam. The main charge in each hole was rack- arock, but the last cartridge in each hole was No. I dyna- mite, which was allowed to project 6 ins. outside of the hole. Every 25 ft. apart along the drifts were placed cartridges (zy 2 x 24 ins.) of No. I dynamite packed solid in a thin copper shell ; and directly above each of these cartridges was a rigid brass cartridge (2x8 ins.) containing No. I dyna- mite packed loosely and an electric exploder. The mine was flooded with water and fired. There was no loud report and the concussion was comparatively slight. A contract was let for dredging the rock at $3.19 per cu. yd. ; but pending the award of the contract a derrick scow was used and removed 15 to 30 tons daily at a cost slightly less than the subsequent contract price. Large blocks were chained by divers. Later the contractors raised 120 tons a day, using two large grapple dredges. It is apparent from these meagre data that the rock was broken in large chunks which were dredged with great difficulty. The Derby Tubular Drill Bit. Lieut. Geo. McC. Derby (now Major of Engineers, U. S. A.) invented a drill bit that was used in drilling on the Flood Rock work, and it proved so greatly superior to the X-bits that I regard it as worthy of special description. Maj. Derby writes me that he patented the drill bit in 1885 and sold the patent rights to the Rand Drill Co., which, for reasons unknown to him, has never placed it upon the market. The drill steel was hollow, as was also the bit which was provided with six points or teeth. The bits were sharpened very much like the bits used in the plug drills made by the C. H. Shaw Pneu- matic Tool Co., of Denver, Colo. Each bit was only 2 to 6 ins. long and fastened to the end of the hollow wrought iron drill rod with a steel pin or expanding copper ring. This saved SUBAQUEOUS EXCAVATION. 291 steel and saved transporting long, heavy drill rods to and from the blacksmith shop. This bit was used with the' ordi- nary percussive air drill, and, in drilling, a small core was formed which broke up under a slight blow on the drill rod. The chips were washed out of the hole by a current of water that was forced down through the hollow drill rod. The water was introduced into the hollow drill rod, either through the rotating bar or through a sleeve surrounding the piston rod which was lengthened for this purpose ; the first method being the best. Maj. Derby informs me that the coarse chips of rock broken off by the bit are washed out whole, instead of being reduced to dust, which saves power and time in drilling a hole of given depth. This fact is well shown by the following comparative records : Experiments were conducted for several months of actual work, during which time 39,119 ft. of hole were drilled with X-bits and 39,200 ft. with the Derby tubular bit. The holes were about 9 ft. deep, and Rand "Little Giant" drills were used. As a result of this competition it was found that the tubular bit drilled 51^ per cent, faster than the X-bit, and that the diameter of the bottom of the hole was 25 per cent, greater than with the X-bit, which in itself is a decided advantage. Using a starter X-bit of 3*4 ins., the bottom of a lo-ft. hole was 2 ins. diam. ; but with the tubular bit the bottom was 2^2 ins. diam. Moreover the tubular bit made a perfectly round hole, which lessens the chances of a bit's sticking. It seems to me that the greater speed of drilling with the tubular bit was due to the use of a jet of water to wash out the chips, which also accounts for the fact that the bit does not wear so rapidly. Whatever the reason, the record of excellence of the tubular bit is well worthy of serious consideration by all who are interested in economic drilling. Drilling and Dredging Way's Reef. Way's Reef, New York Harbor, was removed in 1874. The crew was 35 men, consisting of I draftsman, 2 divers, 3 carpenters, I engineer, 8 drillers, I blaster, i blacksmith, 2 blacksmith helpers, 12 292 ROCK EXCAVATION METHODS AND COST. sailors, 2 firemen, I timekeeper and i tide gage keeper. This crew worked two shifts on the U. S. steam drilling scow. At first the starting bits were 3^ ins., but later it was found that by using a 5^-in. bit more explosive could be placed in a hole resulting in breaking the rock up much better, even with comparatively wide spacing of the holes, which is a point well worth remembering. The average depth of drill hole was 8.13 ft., but only 6 l /> ft. of hole were averaged per drill per 8-hr, shift. About 3,030 cu. yds. of mica-schist were excavated, 15,308 Ibs. of nitro- glycerin being used. The cost of dredging and dumping the rock was $4.29 per cu. yd., the dredge averaging 35 cu. yds. per day. The total cost of this excavation was $18.26 per cu. yd. The work was done by day labor for the Govern- ment, and at a time when subaqueous drilling was an art little understood. Cost of Excavation, Eagle Harbor, Mich. The following facts have been abstracted from a report by Mr. L. Y. Scher- merhorn : In 1877 a dredge was used for removing blasted rock in Eagle Harbor; 3,200 cu. yds. being dredged in 63 days (lo-hr.) to a depth of 14 ft. The dredge scow was 65 ft. long, the dredge being an "Otis" with a I cu. yd. dip- per. The rocks handled by the dredge dipper averaged less than I cu. ft. in size. Rocks of I cu. yd. or more were chained out. The rock was a trap and conglomerate, weigh- ing 169.4 Ibs. per cu. ft. ; and I cu. yd. of solid rock made 1.83 cu. yds. of loose rock in the scows. The rock dipped 30 to the north. Table XXXVII. gives the data of three seasons' work : TABLE XXXVII. "o +J *d en $ Dynamite. ol rt C s J3 0, eu O *O +3 rt o* r* CU rv UH a - - .c 1 C/3 1875.. 1876. . I877-. Total. o o 392 309 183 J_ 2,099 i,945 1,343 5.387 ~ .13 5-35 6.30 7-34 5 5-0 7-7 8-5 en en 3 656 132 88 876 6 2.36 2.67 2.26 03 Q 51 40 32 123 en "o 147 275 154 O 75 775 600 1.450 of 6 441 3,260 1,899 SUBAQUEOUS EXCAVATION. 293 Most of the drilling was done from a large platform ; but for drilling boulders a tripod platform was used, on which the drill was mounted. Drill holes were plugged with wood- en plugs, but storms and ice caused the loss of nearly two- thirds of the holes drilled the first season (1875). One-half the cost of drilling was chargeable to the first 2 ft. of the hole; that is, up to the point where the drill pipe entered the hole, protecting it from further filling up with sand. During the last season (1877) the holes were drilled 20 ft. below water surface, or about 4^2 ft. below the bottom of the intended excavation; but a greater depth would have made the dredging easier by breaking up the rock better. No. i dynamite broke the rock up well for a small area around the hole; but No. 2 broke the rock up better for a greater area. A mixed charge of No. i and No. 2 proved the most effective. The following are the data of dredg- ing : June 26 to Sept. 6, 63 days ; days worked, 47 ; average hours worked per day, I2J4 ; repairs made during good weather, 83 hrs. ; repairs made during bad weather, 46 hrs. ; rock dredged per hr., 5.55 cu. yds.; rock dredged (place measure), 3,000 cu. yds.; boulders dredged, 200 cu. yds.; large rock chained out by divers, 150 cu. yds.; average depth of solid rock excavated, 2.6 ft. ; maximum depth of rock, 5.0 ft. ; area excavated, 35,000 sq. ft. Cost of Eock Excavation, Pier 14, New York Harbor. In the Trans. Am. Soc. C. E. f Vol. XXXII., 1894, Mr. John A. Bensel describes the method and cost of excavating 1,530 cu. yds. of mica-schist near Pier 14, New York City. The excavation was carried to 35 ft. below low water, or 40 ft. below high tide. A contractor began the work at $25 per cu. yd., but finally abandoned the work. The crew con- sisted of i diver, i foreman, 2 blacksmiths and 5 deck hands ; and, drilling from a platform with one Ingersoll drill (largest size), they averaged only 13^ lin. ft. a shift. Two 18 x 2o-ft. platforms, floated out on pontoons and support- ed by 8 x 8-in. spuds 55 ft. long, were used. When stand- 294 ROCK EXCAVATION METHODS AND COST. ing on the spuds the platforms shifted up and down stream with the tides, 3^ ft. from the vertical. The platforms col- lapsed three times ; once due to swell of a passing boat ; once due to a blast ; and the third time without apparent cause. While the platforms were being repaired, a crew of 2 divers and 10 men removed 85 cu. yds. of the blasted rock, at the rate of only 3.4 cu. yds. of loose rock per shift. Then a grab-bucket dredge was tried; and averaged 18 cu. yds. of loose rock a day for a week. The contractor then aban- doned the work. The Dock Department then built a large four-drill scow of 12 x 12-in. spruce, the dimensions being 22 x 33^ ft. x 6 ft. deep. The scow and plant cost $5,000. This scow was not provided with spuds (a fatal omission), but was anchored with four pile-driver hammers of 3,000 Ibs. each. The drill rods consisted of two pieces of i^-in. octagon steel, joined by a double ended chuck to make a total length of 45 to 50 ft. From Sept. 2, 1892, to Mar. 13, 1893, drilling was carried on without interruption (presum- ably working one shift a day with four drills), and only 231 holes (2 l / 2 and 3-in.) were drilled, each averaging 7 ft. deep, which was 3 ft. below grade. Gelatin (95 per cent.) was used in blasting. In dredging, clam-shell buckets, 4 and 7 cu. yds. capacity, a grapple and a bucket dredge were tried, with little difference in results, all being very disappoint- ing. The solid rock dredged was 1,530 cu. yds., plus 450 cu. yds. of riprap, and it took 886 hrs. work of the dredge to do this work, costing $22,145 f r tne dredging alone! The amount of rock removed by the dredge was 4,805 cu. yds., measured in the scow; beside which 480 cu. yds. of rock (scow measure) were removed by divers. The total cost of this work was nearly $70,000. I think it would be hard to find a better example of money wasted in an attempt to do work by day labor instead of by contract. The failure of an inexperienced contractor evidently led the Dock De- partment into an expensive experiment. Another feature about this work that showed lack of experience was the SUBAQUEOUS EXCAVATION. 295 failure to space the holes closer together, or to drill holes larger in diameter, or both. If that had been done the dredge would have been more effective. The mica-schist of Man- hattan Island is an exceedingly tough rock, and it requires close spacing of holes for subaqueous work like this, in order to break the rock into small sizes. The Dock De- partment, however, spaced the holes 6 ft. apart on the north and south lines, and 5 ft. apart on the east and west lines, according to Mr. Bensel ; although according to the scale drawings given by him the distances were 5 ft. and 4 ft. in- stead of 6 ft. and 5 ft., as stated in the text. The result of the blasting seemed to be to stack the broken stones against each other, and not to loosen and throw up the mass. Divers described this bottom as being oftentimes like a pile of grave stones, one stone lying against another. Drilling and Dredging Boulders. The following is an ab- stract from Engineering Record, Jan. 13, 1900: At Wood's Hole, Mass., large boulders were encountered in dredging and were drilled from a platform (10 x 25 ft.) suspended from the dipper boom by a tackle at each corner. Ordi- narily the platform is held by clamps which slide on vertical clamp timbers on the bow of the dredge. If it is desired to swing the platform around one end as a center, it is clamped to one guide only, which is in the middle or at one corner. A slot to drill through runs from end to end of the platform. A 3^2-in. pipe has at one end an i8-in. ring 6 ins. deep with the annular space cast full of babbitt ; and this is set vertically in the slot of the platform. The loaded end of the pipe is set on the highest point of a boulder, and, even against the strongest tides, is held in position by its weight and by guys from the bottom to the platform. A Rand drill is placed over the pipe and its 2%-in. bit inserted in it. The Rand drill is lowered by tackle when the limit of its feed is reached. For charging the bit is replaced with a 2-in. pipe and a i-in. cartridge is inserted and fired with- 296 ROCK EXCAVATION METHODS AND COST. out moving the dredge. An ordinary day's work with a 7-yd. dipper dredge has been 126 cu. yds. of earth and 7^/2 cu. yds. of rock. Drilling in San Francisco Harbor. The following is an abstract from Engineering Record, May 26, 1900: In San Francisco Harbor ledges of metamorphic sandstone were drilled from a revolving platform. The platform, 25 x 160 ft., is made of four lines of longitudinal stringers of 3 x 12- in. timbers bolted together. These stringers rest on 8 x 10 in. floor beams that are 20 ft. c. to c., and queen-post trussed. Through the center of the platform rises a mast 2 ft. square and 68 ft. high, made of four pieces of 12 x 12-in. bolted together and dressed to a diameter of 18 ins. for the upper 15 ft. The top of the mast is guyed by four wire cables to anchors. One block of a tackle is clamped to the upper end of each guy; the other block is attached to the top of the mast, and enables the guys to be tightened or adjusted readily. Fifteen feet below the top of the mast there is fixed to it a collar with a channel in its upper surface, in which there are steel balls for the bearings of a revolving collar above, to which are attached 18 guys (i-in.), or sup- ports, one to each end of each of the nine floor beams. These guys are adjusted by long turn-buckles at the bottom. Two steam drills and one well driller a*re installed on the plat- form and operate lo-in. bits. The holes are cased with 10- in. sheet iron pipe. Steam boilers are located on a barge and deliver steam through ball and socket pipe. CHAPTER XVI. COST OF RAILWAY TUNNELS. The American System. In America there is to-day only one system of rock tunneling in common use. The Amer- ican system has four distinctive features : ( I ) An advance tunnel called a "heading" is driven in the upper part of the proposed tunnel. (2) The drill holes in the center of the heading converge in pairs, forming a V, and are fired first so as to form a wedge-shaped cut, called the "center cut." (3) The lower part of the tunnel, called the "bench," is taken out by blasting in holes drilled vertically, or nearly so. (4) Timbering, if used at all to support the roof, consists of "bents," each having upright posts supporting a segmental wooden arch, upon which rests longitudinal planking, called "lagging." Two of these four features appear unquestionably to have been invented by Americans. The center-cut system of drill- ing was first used in the celebrated Hoosac Tunnel in Mass- achusetts (begun 1858) ; and the segmental arch system of timbering, which leaves the entire area of the tunnel un- obstructed by props or supports of any kind, was first used in 1854 in the Van Nest Gap Tunnel, on the D., L. & W. R. R., in New Jersey, under Mr. James Archibald, Chief Engineer. Three rafter pieces had been used in American tunnels prior to 1854, but to Mr. Archibald belongs the credit of having increased the number so as to make a regu- lar wooden arch. This system of timbering has been suc- cessfully used even in tunneling through sand and gravel, and it is an open question whether any of the cumbersome systems used abroad need ever be used in America. Occasionally some contractor tries an experiment such as driving the "heading" at the bottom instead of at the 297 2Q8 ROCK EXCAVATION METHODS AND COST. top. After killing a few men, return is usually made to the top heading. It is exceedingly difficult, and in loose rock impossible, to prevent disastrous falls of rock from the roof where the bottom heading method is used. One contractor, an eminent member of the American Society of Civil Engineers, had his life crushed out by a fall of rock in a tunnel that he was driving in New York City by the bottom heading method. Fig. 51 shows the American system of timbering. When machine drills were first used in tunneling it was thought necessary to mount the drills on drill carriages which ran upon tracks. The delays involved in clearing away the muck (as the broken rock is called) so that the drill carriage could be run up to the face again after blast- ing, led to the invention of the column method of mounting drills. Two drills may be mounted on opposite sides of one column, and I have seen two columns with four drills used in a heading 10 ft. wide. Two drills on one column, how- ever, cannot be worked to advantage in a heading much less than 6 l /> ft. wide. With four drills at work the holes, which are usually 8 to 12 ft. deep, are drilled in a heading with great rapidity : but the time lost in waiting for smoke to clear away after blasting, and in mucking (loading the rock), usually con- sumes 50 per cent, of the total time. In railway tunneling rapid progress is usually imperative, and this is especially true where tunnels are so long that the rest of the construc- tion work will be completed ahead of the tunnel work. To overcome the delays incident to blasting and mucking, the contractor should spare no reasonable expense where rapid progress is desired ; yet one of the commonest errors is to provide no adequate means for clearing the air after blast- ing. I have described the Simplon Tunnel work in some detail, because I think that American contractors are not, as a rule, awake to the advantage of using water under pressure to lay the dust and the smoke, in addition to using COST OF RAILWAY TUNNELS. properly designed fans or blowers. Another lesson that can be learned from the Simplon Tunnel is the use of sheet iron covering laid down upon the car rails before blasting. By doing this it is possible for the muckers to clear the track quickly after a blast, so as to get muck cars up to the face without delay. A third lesson to be learned is the use of shal- low holes with very heavy charges of explosive. This causes the muck to be broken up fine and to be hurled away from the face, so that it takes the minimum of time to clear the face ready to begin drilling. I repeat that the contractor who seeks to make a record in rapid tunneling should bend every effort to provide ways and means for the rapid clear- ing of muck, gas and dust away from the face, so as to keep the drills at work as large a percentage of the time as pos- sible. A Device for Laying the Dust with Water. Where a long tunnel is to be driven it will unquestionably pay to have a water main laid alongside the air main, so as to deliver a stream of water against the face after a blast ; but in short tunnels it may not pay to do this. A device that has been used with success in England by Mr. William James is de- scribed in a paper read May 19, 1904, before the Institution of Mining and Metallurgy. As originally designed it con- sists of a length of 6-in. pipe, which is let into the 2-in. air main at the mouth of the level (in a mine). This 6-in. pipe is provided with a tap, through which it can be filled with water from a cistern just before blasting. After blasting a compressed air valve is suddenly opened, and the water is carried by the air in the form of a fine spray out of the air pipe, which is directed against the face. The result is that for 40 ft. back of the face the dust and nitrous fumes are quickly laid by the water. A ventilation pipe into which air jets are delivered quickly sucks out the CO and CO 2 gases, thus leaving a face clear of dust and gases. The Gallitzin Tunnel. This is a single-track tunnel, 3,600 ft, long, through the Alleghenies, on the line of the Penn- 300 ROCK EXCAVATION METHODS AND COST. sylvania R. R. The work was done in the years 1903 and 1904, under contract, by Mr. P. F. Brendlinger, M. Am. Soc. C. E., who was kind enough to give me every facility for studying it. The material encountered was mostly shale and some sandstone. Figs. 48 and 49 show the tunnel di- mensions and the placing of drill holes. For the most part no timbering was required. Two portal headings were Fig. Fig. 49. driven, there being no shafts. In each heading there were four air drills mounted on two columns. Headings were at first 7 ft. high and 15 ft. wide, but were gradually nar- rowed, to 10 ft. wide. Each driller was given a day's stint of four lo-ft. holes in the lo-ft. heading, although when the heading was 15 ft. wide five holes was a shift's work per drill. The heading force began work at 7 A. M V but drilling did not usually begin before 8 A. M., and was finished by 3 p. M. The holes were loaded and fired by 4 P. M. The drill- ing force on each heading consisted of 4 drillers, 4 helpers, I nipper (or tool carrier), I mucker, I timberman, i powder- man and I foreman, a total of 13 men. The night shift on the heading consisted of 14 muckers, I foreman, with 2 mules hauling the dump cars to the bench, which was never more than 1,000 ft. back of the face. At the bench the muck was dumped and loaded by a steam shovel, together with the bench muck, into cars hauled away by a dinkey COST OF RAILWAY TUNNELS. 301 locomotive. Although the holes in the heading face were 10 ft. deep, the actual advance after each blast was 9 ft. The 6 "cut holes" were fired first, then the side holes on one side, then the side holes on the other side, and finally the roof holes, making four separate shots for the 16 holes. Each hole was charged with 14 sticks of 40 per cent. Forcite gelatin, using three boxes for a charge. Each firing threw down about 23 cu. yds., hence there were 7 ft. of drill hole and 6 l / 2 Ibs. of Forcite per cu. yd. of heading. The muck was broken into small fragments by the blast. Each muck- er averaged less than 2 cu. yds. loaded per shift. The aver- age progress was 50 ft. of heading a week at each end of the tunnel, working as described. Fig. 50. The bench was taken out in two lifts, as shown in Fig. 49. Two or three drills on tripods first drill holes to widen out the heading. In the top bench four vertical holes are driven 7 ft. deep, and two diagonal holes, about 7 ft. back of the face. The bottom bench holes are placed 12 to 14 302 ROCK EXCAVATION-METHODS AMD COST, ft. back of the face. The four vertical holes in the top bench are "sprung" by firing I to i l / 2 sticks in each hole, and then loaded with 5 to 8 sticks per hole. The holes in the bottom bench were "sprung" twice ; first with two sticks per hole, then with 10 to 14 sticks, and finally loaded with 40 to 60 sticks in each hole. About 1,000 Ibs. of Forcite were used per month in both ends of the tunnel. The steam shovel was run with compressed air, and was used in this single-track tunnel with economy. The tunnel was lined with rubble bench walls and a concrete arch, as shown in Fig. 50. Space forbids going into greater detail. Fig. 51- Wabash R. R. Tunnels. I am indebted to Mr. T. H. Loomis, Div. Eng. P., T. & W. R. R. (Wabash system) for much of the following data kindly furnished by him when I went over the line in 1903 studying the methods and cost of excavation. Eight double-track tunnels were underway, the cross-section of each being as shown in Fig. 51. The material encountered was shale, sandstone, fire clay and occasional seams of coal characteristic of eastern Ohio and western Pennsylvania. The section above the wall plates (*. e., the longitudinal timbers on top of the posts) requires an excavation of 15 cu. yds. per lin. ft. The clear width between wall plates is 3454 ft. The segmental arch COST OF RAILWAY TUNNELS. 303 timbers are 12 x 12 ins., lagged with 4-in. plank, the arch ribs being 3 to 4 ft. c. to c. The favorite method of attack, as shown in Fig. 52, was by what I will term the twin-head- ing method ; two 7 x 8 f t. headings being driven as shown, and afterward enlarged. The floor of these headings is i2 l / 2 ft. above subgrade, thus leaving a 12^-ft. bench, A C D E, to be taken out. One machine drill is operated in each head- fire Clay- +r pr-j A[ i -i- Fig. 53- ing (two could be worked) for the drilling is easy. The rivalry between the two drilling gangs in these twin head- ings appeared to me to be one of the best features of this method of attack. It is certain that no hitherto published data show as low a cost per cubic yard for tunnel work as the data which I secured on this work. The weekly prog- ress was not rapid, but, as all the tunnels were comparative- ly short, there was no necessity of going to great expense, in securing rapid progress a fact that tunnel contractors should bear in mind. Steam drills were used in some of the short tunnels. The following is the actual cost of excavat- ing and timbering the section of a tunnel above the wall plates (15 cu. yds. per lin. ft), using air drills, for a dis- tance of 100 lin. ft. : Labor $2,527.45 2,000 Ibs. 40 p. c. dynamite at 12 cts 260.00 470 gals, kerosene oil, at 12 cts 56.40 1,875 g a l s - gasoline, at 12 cts 225.00 3,000 bu. coal for compressor, at 9 cts 270.00 Machine and lub. oils 62.50 Blacksmith shop : 150.00 304 ROCK EXCAVATION METHODS AND COST. 41,649 ft. B. M. timber, at $23 $957-93 Total cost of 100 lin. ft $4,509.28 Cost per lin. ft. above wall plates 45.09 Cost per cu. yd., including timber 3.06 Cost per cu. yd., excluding timber 2.60 The material in this case was sandstone. On another tunnel the section above the wall plates was excavated by hand at a cost $40.90 per lin. ft., or $2.73 per cu. yd., for a distance of no ft., the material being hard fire clay in the upper half and shale in the lower half of the section excavated, making easier excavation than in the sandstone. The force engaged in hand drilling, by the twin- heading method, was: Wages per 10-hr, shift. i general foreman $4 i foreman 3 1 blacksmith 3 2 carpenters, at $3 6 10 miners, at $2 20 10 muckers, at $1.50 15 i team 4 Total per shift (zo-hr.) $55 While these men took out the whole section above the wall plates (15 cu. yds. per lin. ft.) for $2.73 per cu. yd. for labor and explosives (not including cost of timber), working in shale and fire clay, they excavated a 7 x 8-ft. heading in sandstone for $3.75 per cu. yd., distributed as follows : Per lo-hr. shift. Labor on 7 x 8 heading $18.00 Dynamite 3.84 Repairs 90 Light 32 Total per shift $23.06 COST OF RAILWAY TUNNELS. 305 Each shift excavated 6.2 cu. yds. of this 7 x 8.-ft. heading, making the cost $375 per cu. yd., as above stated, equiva- lent to an advance of 3 ft. per shift. No night shifts were being worked on the eight tunnels, and the progress per week in shale was 25 ft. when work- ing by hand and excavating 15 cu. yds. per lin. ft.; and 50 ft. a week working with machine drills. In hard sandstone the weekly progress was about 15 ft. by hand and 30 ft. with machine drills, in all cases working only one xo-hr. shift in the 24-hr, day. The following is the actual cost of timbering on one job : Per M. Georgia pine f. o. b. cars $23.60 Hauling 6 miles 3.00 Cost of framing 5.00 Cost of erecting 3.00 Total per 1,000 ft. B. M $34-6o The carpenters received $3 per lo-hr. day, and laborers erecting received $1.50. The cost of framing and erecting, including supervision, was $8 per M., which was about $2 more than it should have cost had there been more workers and fewer bosses. Over the rough roads each team hauled about 1,000 ft. B. M. per load and made one trip of 6 miles each way in a day. The cost of "packing" (i. e., placing small stones) above the lagging was 80 cts. per cu. yd. We now come to what I have said are the lowest records of tunneling cost yet made public: Tunnel heading in sandstone, double track full section above the wall plate grade (15 cu. yds. per lin. ft.) : Cu. yd. Drilling $0.60 Explosives 40 Mucking 85 Total $1.85 306 ROCK EXCAVATION METHODS AND COST, Tunnel bench in same tunnel: Cu. yd. Drilling $0.40 Explosives 20 Mucking 22 Total $0.82 The sandstone was very hard, breaking in large blocks, which have to be drilled and shot before mucking. A steam shovel is used in the bench, and material of heading is car- ried about 400 ft. and dumped over the breast of bench, whence steam shovel loads it along with bench material. In another tunnel, in a formation of practically level strata of slate, limestone (thin) and fire clay (a stone hard as limestone to drill, but disintegrating in the air) the cost was as follows: Heading full double-track sections all above walll plates : Cu. yd. Drilling $0.48 Explosives , 30 Mucking 80 Total $1.58 Bench same tunnel full section : Cu. yd. Drilling $0.30 Explosives 20 Mucking 18 $0.68 In the case of another tunnel in coal formation with a 5~ft. vein of coal running all through on the wall plate grade; steam drills used in rock, and steam coal augers in the coal, with steam shovel for mucking, the costs were as follows :. COST OP RAILWAY TUNNELS, Headings per cubic yard double track: Labor $0.966 Explosives and materials 090 Total $1.056 Bench same tunnel and formation: Cu. yd. Labor $0.38 Explosives and materials 04 Total , $0.42 This last may seem too low, but it was in all probability the cheapest material a tunnel is- ever built in, and the organiza- tion was so good that it was worked with extreme economy. A core of about 2 cu. yds. per lin. ft. was left in the middle of the heading (between the twin headings) and taken out along with the bench. The Stampede Tunnel. In Engineering News, Oct. 3, 1891, Mr. Charles W. Hobart gives data on the Stampede or Cascade Tunnel of the Northern Pacific R. R. Bids were opened in New York Jan. 21, 1886, for a 2-mile tunnel to be completed in 28 mos. Of the 12 bids, that of Mr. Nelson Bennett was lowest and was accepted. A forfeit of $100,000 and 10 per cent, of the contract price for failure to complete within the time was required. Mr. Bennett telegraphed his general manager to gather men and clear a road to get the machinery on the ground. The plant was purchased for $100,000 in New York and shipped. It consisted of 5 en- gines, 2 water wheels, 5 air compressors, 5 boilers of 70- H.-P. each, 4 fans, 2 electric arc light plants, 2 miles of 6-in. wrought iron, 2 miles of water pipe, 2 machine shop outfits, 36 air drills, 2 locomotives, 60 dump cars, 2 saw mills and other necessaries. This plant had to be transported on wagons and sleds from Yakima, Wash., a distance of 82 miles to the east portal of the tunnel and 87 miles to the west portal. The first wagon loads started Feb. I, and the 308 ROCK EXCAVATION METHODS AND COST. first boiler Feb. 22. By June 19 the plant for the east portal, and by July 15 the plant for the west portal had reached its destination. On Feb. 13 hand drilling was begun on the east portal and 411 ft. of tunnel had been driven when the machines began June 19. On March 15 hand drilling start- ed at the west end and by Sept. i, when the machines start- ed, 488 ft. had been driven. The last 15 miles of the haul- ing before reaching the mountains was in mud, so that wagons were hauled by block and tackle, planks being laid down in front of the wheels and taken up as fast as the wagons passed. About one mile a day was covered in this way. When the mountains were reached sleds were im- provised and hauled by block and tackle with teams. Wagons lightly loaded with provisions traveled 12 miles a day. The cost of clearing the way and getting the machinery and materials on the work was $125,000, * and 6 mos. time was required. The tunnel was to be 9,950 ft. long, 16^ x 22 ft. in the clear ; 900 ft. had been driven by hand, leaving 9,050 ft. to be driven in 22 mos. An 8-ft. heading was driven along the top of the tunnel and was kept 30 ft. ahead of the bench. The tunnel was timbered as work progressed. The average number of men employed, after the machinery was installed, was 350. They worked lo-hr. shifts, receiving $2.50 to $5 a day. Con- tractor boarded men at 75 cts. a day. A bonus of 25 cts. a day was paid each laborer for every foot gained during the month over the necessary average of 13.6 ft. a day in both headings combined, and each driller received a bonus of 50 cts. per day per ft. gained. Every day of the year was worked, requiring two shifts of 75 men each, beside the en- gineers, firemen, carpenters, machinists, etc., making a monthly payroll of $30,000. The best month's progress was April, 1888, when a total advance of 540 ft. was made in the two headings, or 9 ft. a day per heading. The average progress for 21 2 / 3 mos., with power drills, was 413 ft. per NOTE. Wages were $2.50 for laborers, which is an unusually high price. COST OF RAILWAY TUNNELS. 309 month for the two headings. On May 3, 1888, the headings met, and on May 14 the excavation was completed, 7 days before the time limit. The track was laid in two days more and on May 22 the first regular train passed through the tunnel. The total explosives used were 309,625 Ibs., as follows : No. of 5o-lb. boxes. Giant No. i, 60 per cent 4O324 Giant No. 2, 45 per cent 2,123^ Hercules No. I, 60 per cent 1,609^ Hercules No. 2, 45 per cent 1,781 24 Nitro glycerin No. 2 232 Forcite No. 2 . 4i/^ Total No. of 50-lb. boxes 6,192 The average price of all explosives was $10 a box, or 20 cts. per Ib. The total number of men killed in the two years was 13. The following data were furnished by Mr. An- drew Gibson, Asst. Engr. The American center-cut system of blasting was used ; 20 to 23 holes, 12 ft. deep, being drilled in the heading, and about 18 holes in the bench. Each drill, in medium hard rock, would make 6 or 7 holes in 5 hrs., although at times in an exceedingly hard layer 15 hrs. would be required. About 400 Ibs. of dynamite were used at each blast in each of the headings and benches. This would break 8 to 12 lin. ft. of tunnel, although in very hard rock at times only half this progress was made. The rock is basaltic, * with a dip of 5 to the west. It required immediate tim- bering, which delayed the drillers and muckers about 25 per cent, of the time. During the period of hand drilling there were 17 men, with about 23 muckers, employed in each head- ing, and 4 lin. ft. of tunnel in 24 hrs. were averaged. Dur- ing the period of air drilling, 10 drills were used, 5 in each end, and the progress was 6.9 ft. in 24 hrs. per heading, or 207 ft. per mo. of 30 days. While the contract size of the tunnel was i6 l / 2 ft. wide, and 22 ft. from subgrade to face * Elsewhere it is stated that the rock was shale. 310 ROCK EXCAVATION METHODS AND COST. of arch, the timbered sections had to be excavated 19^ ft. wide by 24 ft. high, thus requiring 15.7 cu. yds. of excava- tion per lin. ft. where timbering was used, as against 12.36 cu. yds. where no timber was used. Timbers were 12 x 12 ins., except the 8 x 12-in. sills. Five segments were used in the arch, lagged with 4 x 6-in. pieces. Bents were spaced 2 to 4 ft. Water gave no trouble. Mules were used for hauling up to the first half mile ; then small locomotives, which hauled 8 to 12 cars. A "go- devil" or platform on wheels was used to great advantage in loading cars. The men wheeled the rock on plank runways from the heading to the "go-devil," dumping directly into cars below; and the muckers on the heading never inter- fered with those on the bench. It was also a great con- venience in timbering. Before blasting the drills were load- ed upon the "go-devil," and it was pushed back some dis- tance from the face. Endless belt conveyors for removing muck to the "go-devil" were contemplated, but they were never used, as with the large force of men at work they would have been in the way. The swelling of the shale on exposure often reduced a 12-in. timber to 4 ins. ; hence it was necessary to line the tunnel with masonry. Concrete side walls and a brick arch were used for lining. The concrete mortar was brought in on cars and run back of the forms through spouts, without shoveling ; then the broken rock was shoveled into the mor- tar from a flat car. The total cost of the tunnel to the N. P. R. R. under Mr. Bennett's contract (which di'd not include masonry lining) was $118 per lin. ft. Mr. Bennett *s brother was the super- intendent of the work. The actual cost of tunneling the west end during the month of Nov., 1887, was $75-75 P er ft. for the 258 ft. driven, distributed as follows: Labor. Supt., y 2 mo., at $500 $250.00 " i mo., at $250 250.00 Master mechanic, y 2 m COST OF RAILWAY TUNNELS. 311 Engineers, 4 x 30 = 120 days at $4 $480.00 Machine repairers, 3 x 30 = 90 days at $3.50 .... 315.00 Firemen 4x30=120 " " 2.50.... 300.00 Blacksmiths 2 x 30 = 60 " " 4.00 .... 240.00 helpers 2x30= 60 " " 2.50.... 150.00 Carpenters 396 days at $3.00 i, 188.00 Foremen 160 " " 4.50 720.00 Drillmen 294 " " 3.50 1,029.00 Chuckmen 293 " " 3.00 579-O Muckers 1,138 " " 2.75 3,129.50 Nippers 60 " " 2.50 150.00 Dumpmen 60 " " 2.50 150.00 Car drivers 60 " " 2.50 150.00 Time keeper 30 " " 2.50. 75-OO Lampmen 60 " " 2.50 150.00 Laborers 662 " " 2.50 . . 1,655.00 Bonus for daily progress over 6 ft 800.00 Total labor for 258 ft. at $45.90 per ft $11,835.50 Material. 78,000 ft. B. M. timber, at $10 $780.00 800 Ibs. wrt. iron, at 6 cts 48.00 64^2 cords wood, at $3 J 93-5O 240 tons coal, at $4 960.00 900 caps, at i ct 9.00 14,400 ft. fuse, at i ct 144.00 13,800 Ibs. dynamite, at 16 cts 2,208.00 Total materials for 258 ft., at $16.80 per ft $4,342.50 Plant. 6 per cent, of $50,000 plant, I mo $250.00 1 /28 of 75 p. c. depreciation * of $50,000 plant 1,339.28 10 p. c. on all above to cover all possible omissions. 11,776.72 Total plant charges for 258 ft. at $13.05 $3,366.00 * Note that a liberal hut not unusual allowance is made for plant depreciation,, ^ ThJs 10 per cent, practically cove.rs_ tb,e. cQst qf installing th,e plant. 312 ROCK EXCAVATION METHODS AND COST. Summary of cost per ft. Labor $45.90 Material 16.80 Plant 13.05 Total $75.75 During this month the entire length was lined with timber, the rock being a soft basaltic rock that drills well but goes to pieces rapidly on exposure. There were no accidents or delays. On the east end during this same month, with an equal force, the progress was 246 ft., at a cost of $72.70 per ft. It will be noted that wages were high. It will also be noted that the cost of hauling and installing the plant is not in- cluded, although a liberal allowance is made for plant de- preciation and in the 10 per cent, added to cover omissions. The contractor received for his month's work on the west end of the tunnel : 258- ft. tunnel, standard section, at $78 $20,124 862 cu. yds. extra excav., at $4.50 3,879 78,000 ft. B. M. lining, at $35 2,730 258 ft. of tunnel, timbered, at $103.62 $26,733 The best month's record in driving a heading was 274 ft., but, as before stated, the average progress with the air drills was 207 ft. per mo. per heading, although in the month of Nov., 1887, 258 ft. were progressed on the west end, which was 25 per cent, better than the average progress. Assuming that 15.7 cu. yds. were excavated per lin. ft. of tunnel, the total excavation at the west end for November was 4,052 cu. yds. It is probable that the 862 cu. yds. extra excavation, above given, are included in this estimate, because the "stand- ard section" differed from the timbered section by 3.3 cu. yds. per lin. ft., and in 258 ft. this would amount to 852 cu. yds. On this assumption (of 4,052 cu. yds.) the labor cost $2.92 per cu. yd.; the materials, $1.07 per cu. yd.; and the COST OF RAILWAY TUNNELS. 313 plant, $0.83 per cu. yd. ; total, $4.82 per cu. yd. for the best month's work. Mount Wood and Top Mill Tunnels. Mr. W. J. Yoder, in the Journal of the Western Society of Engineers, 1897, gives the following data: The tunnels (built in 1888-1889) are within the northern city limits of Wheeling, W. Va., and the material penetrated was for the most part shale of the coal measures. The shale disintegrates rapidly upon ex- posure and must be supported. The block or American system of timbering was used for lining, and was kept never more than 50 ft. back of the face. All drilling was done by hand, and the position of drill holes is shown by sketches in the article. A top heading 10 x 34 ft. was driven, and then widened; the bench was taken out in two lifts. The first or cut holes in the heading were drilled so as to blast out a long horizontal wedge of rock near the roof; these holes being 5 to 6 ft. deep. Then a lower row of 5-ft. lift holes was fired. Finally the bottom of the heading was taken out like a bench by a row of vertical holes and a row of horizontal holes. In all 33 holes were fired in the heading, aggregating 160 lin. ft., and requiring 60 Ibs. of 40 per cent. Forcite to load them. The effect of the firing was to make an advance of 2^2 ft., displacing 25 cu. yds. The heading gang consisted of i foreman, 14 drillers, 12 muckers and I nipper. About 25 lin. ft. of drilling was considered a day's (10 hrs.) work for 2 men. The muck was wheeled in iron barrows to a traveler and dumped down chutes into cars. The heading gang timbered and placed the packing above the arch; two lo-hr. shifts per week being needed for this work, leaving 10 shifts per week for advancing the head- ing. The timbering is fully described ; 660 ft. B. M. of white oak were used per lin. ft. of tunnel. The bench holes were 8 ft. deep, churn drills being used except for the corner holes and for blockholing. The bench force consisted of I fore- man, 6 drillers, 18 muckers, 2 mule drivers, 3 dump men and i nipper. The average haul was about 800 ft. 314 ROCK EXCAVATION METHODS AND COST. The maximum monthly progress (working two lo-hr. shifts) in a heading on the Mount Wood Tunnel was 130 lin. ft., the average monthly progress being 84 ft. The maxi- mum monthly progress on the bench was 125^ ft., the aver- age being 97 ft. The average excavation was 10.2 cu. yds, per lin. ft. of heading and enlargement, and 18 cu. yds. per lin. ft. of bench. The total excavation in both tunnels was 49,670 cu. yds., and the excavation in approaches was 25,751 cu. yds. The number of men employed was 350. The heading men were composed of two-thirds Negroes and one-third Aus- trians. The foremen were Irish. The best drillers were Negroes. No work was done Sundays or Saturday nights. The scale of wages (lo-hr. shift) was as follows: Heading Gang. i foreman at $4.00 14 drillers " 1.75 10 muckers 1.50 i nipper " 1.25 Bench Gang. 1 foreman at $3.00 6 drillers " 1.75 16 muckers " 1.50 2 men (lagging) " 1.50 1 nipper " 1.25 2 drivers " 1.50 3 dumpmen " 1.50 2 mules Miscellaneous, i carpenter at $2.50 4 sawyers " 1.75 i trackman " 2.50 3 blacksmiths " 3.00 i walking boss " 4.00 i timekeeper " 2.25 i engineer and fireman " 2.50 i electrician " 2.50 COST OF RAILWAY TUNNELS. 315 Cost of Labor per Lin. Ft. of Tunnel. Labor excavating (heading, $22.79; bench, $20.95) . .$4374 Hauling and dumping 5-^5 Labor timbering 4.19 " framing timber 77 Blacksmithing i.oo Track repairs 21 Labor electric lighting 88 Superintendance and accounts 2.00 Total labor $58-44 Cost per cu. yd 2.06 The above does not include the cost of timber, oil, fuel, wear of tools or explosives. About I Ib. of 40 per cent. Forcite was used per cu. yd. of tunnel excavation, or 28 Ibs. per lin. ft. The labor cost was $2.34 per cu. yd. of heading, and $1.10 per cu. yd. of bench excavation, making an aver- age of $1.55 per cu. yd., not including the items of timber- ing, etc. The labor cost of erecting arch and packing back of it was $3.19 per lin. ft. of tunnel; or $7.80 per 1,000 ft. B. M. The labor cost of erecting plumb posts and side lag- ging and packing same was $2.33 per lin. ft. ; or $4.27 per i ,000 ft. B. M. The contractors were Paige, Carey & Co., of New York, whose superintendent was Mr. Frank Moran. Tunnel Driven by Hand on the B. & 0. In Engineering News, April 5, 1894, Mr. J. G. G. Kerry gives description and cost of a short tunnel built in 1891 on the W. Va. & P. R. R., a feeder of the B. & O. system. The tunnel is on a Y$ per cent, grade falling to the south, with a length of 624 ft., in a soft blue clay shale, nearly dry and showing little stratification. This shale disintegrates rapidly on exposure. The width was 23 ft., height from floor to spring line 13 ft. ; semi-circular arch of 11^2 ft. radius. The area of the head- ing was 208 sq. ft. ; bench, 299 sq. ft. ; total, 507 sq. ft. Work was all done by hand. The heading gang consisted of I foreman, 8 miners, 6 muckers and I nipper. Common labor 3i6 ROCK EXCAVATION METHODS AND COST. ers were paid $1.45 and miners $1.75 per ic-hr. day. Three sets of holes (2 wet and I dry) were drilled in the heading; each set consisting of 4 holes about 4 ft. deep ; and 24 ft. of hole was considered a good day's work for two miners. Each hole was loaded with 4 to 6 sticks ( 1 / 3 Ib. per stick) of dynamite; and the average advance from a blast was 2 l / 2 ft. A scaffold car, or go-devil, was used in handling the muck. It was provided with a derrick and also used for handling timbers, lagging and packing. The bench gang consisted of I foreman, 8 drillers, 10 muckers and I nipper. The bench was shot down in 4- ft. holds or lifts, two half-depth blasts being made for each hold. Each blast consisted of four holes, two being center holes, and two nearly vertical under the wall plate. The charge was 10 sticks to an outside hole and 15 sticks to a center hole. Muck was taken out in i cu. yd. dump cars in trains of two. Stone flat cars with platforms flush with top of wheels were used for handling large rocks. The bench was kept two wall plate lengths behind the heading, making the same progress, 2^2 ft. per shift. The actual excavation was at the rate of 5 ft. per shift, but the time consumed in pointing down projections, timbering and packing being equal to the time spent in excavation, reduced the average progress to 2 l / 2 ft. per shift. The work was done by con- tract, and it cost the company at contract prices as follows : 11,726 cu. yds. of excavation at $2.85 $33,419 742 " " "packing " 1.75 1,298 256 " " " fallen rock " 1.25 320 303,000 ft. B. M. " 30.00 9,090 Total 624 lin. ft. of tunnel at $70.70 $44,127 The actual cost to the contractor was about $35,000. The method of handling and placing the segmental arch timbering is described in detail. The timbering consisted of a 7-segment arch of 12 x 12-in. white oak resting on 12 x 14- in. wall plates on top of the posts. The i6-ft. wall plates COST OF RAILWAY TUNNELS. 317 were jointed by halving for a foot at each end, so that the forward end always showed the lower half of the joint. The arches were 8 ft. c. to c. The segments of the arches were erected on temporary centers made of 2-in. plank. These centers were erected in two parts and joined at the crown by bolts; a long dog-hook, fastened to the center, was driven into the preceding arch to hold it in place laterally. The arch timbers were wedged solidly against the roof, and the centers withdrawn. The lagging was close laid, all voids being packed with broken sandstone. Each end of the tunnel was lined with masonry for 50 ft., the centers used in this lining being 25 ft. long and mounted on rollers. During use the centers were supported on wedges, which upon being struck lowered the center enough to clear the rock-faced voussoirs. A hole was left in the crown of the arch-center lagging so that the voussoirs could pass through. Above this a piece or two of the tunnel lag- ging was removed, and an iron bar placed on the timber arches. A set of blocks was hung from this iron bar, and used to raise the voussoir stone. Gas pipe rollers were put under the stone to roll it to place on the center lagging. The stone was then canted up, and a rope slung around it, six men then sliding it to place. The contract prices were $9 per cu. yd. for portal masonry, $8 for side walls and $14 for arch sheeting. The cost at contract prices per lin. ft. of that part of the tunnel which was lined (excluding portals, fallen material, etc.) was: Excavation $53-55 Packing 2.08 Timbering 14.75 Side walls 20.56 Arch 21.42 Packing 2.08 Total per lin. ft $i 14.44. 318 ROCK EXCAVATION METHODS AND COST. New Croton Tunnel. In Trans. Am. Inst. Min. Eng., Sept., 1890, Mr. J. P. Carson gives the following data: Work was begun in 1885 on the New Croton Aqueduct Tunnel, which was nearly as large as a single track railway tunnel. The following were the areas of the excavation : As shown Actual on plans. excavation. Area above the spring line .... 73 sq. ft. 105 sq. ft. Area below " " " ....131 " " 178 " " Total area 204 " " 283 " " The tunnel was lined with masonry so as to have an in- side width at the spring line of 14 ft. and a height of 14 ft. The contract price was $7 per cu. yd. of excavation, or $52.88 per lin. ft. A top heading 8 x 16 ft. to 9 x 17 ft. was run by the American center cut system of drilling. Several shafts were sunk and the tunnel driven from them. Sinking shaft I3A a distance of no ft. in wet, soft material cost $416 per ft. Cars holding I cu. yd. of broken stone, or y*. cu. yd. of solid stone, were hauled in trains of 2 or 3 cars by one mule. Experiments were tried to determine the rela- tive advantage of driving the heading and bench separately as compared with driving them as is usual, at the same time, and about 60 ft. apart. It was found that in mica-schist when the heading and bench were driven together the aver- age progress of completed tunnel excavation was 30 ft. a week from one face. The average weekly progress of com- pleted tunnel excavation was only 20.4 ft. per week when the heading was first driven through to the next shaft, and then followed by the bench, which was driven through separately. Out of 76,490 ft. of tunneling 23 per cent, was driven by working the heading and the bench separately, causing a very material delay in completing the tunnel. Average Weekly Progress in Division 3. Mica-schist* Total No. of Weeks. 4.27 Lin. Ft. per Week. -^0.0* Area. Sq. Ft. 28^ *r"v * Heading and bench driven at the same time. COST OF RAILWAY TV I Limestone* 95 /^ VNELS. 22.4* 9.8* 4.25* 1.40* 319 283 361 490 508 Decomposed rock* 152 Sand and boulders* . . 62 x / 3 Soft ground, clay, sand, mica* 128 Mica-schistf . .47.of 165 105 105 Limestone*}* :.33.8f Decomposed rock*j* . .2^.t;t Mica-schist*j; . . s6.o 178 178 196 Limestone"J! . .27.O Decomposed rocki , .I2.lt It is interesting, to note that although faster heading prog- ress was secured by driving the heading clear through be- fore beginning the bench, the progress was not enough fast- er to make up for the delay in waiting to begin the bench ; so that in mica-schist the average progress per week of head- ing and bench was (47 + 36) -"- 2 = 41^ ft., and as they were worked separately the final average of completed tun- nel was 41^2 -T- 2 = 20.7 ft. per week. The men decided to break the record for a week's run in the South heading from Shaft 15, beginning at a point 3,200 ft. from foot of shaft. The heading was 9 x 17 ft. in gneiss. Plant: I duplex Rand compressor, class "B," rated at 1,325 cu. ft. per min., at 80 Ibs. pressure ; 4 and 5-in. air pipe ; loss of pressure by friction in 3,400 ft. of pipe was 15 Ibs.; 3 slugger drills ; one lo-hr. shift per day : 7 to 9:30 A. M. Mucking 2^2 hrs. 9:30 A. M. to 4:30 P. M. Drilling 6 4 '3 to 5 Charging */ 2 " 5 to 6 Firing i Total 10 * Heading and bench driven at the same time. t Heading driven alone. j Bench driven alone after completing heading. 320 ROCK EXCAVATION METHODS AND COST. Distance of heading run in a week, 102 ft. (best previous, 90 ft.) ; area, 145.5 S( l- ft- 5 total, 550 cu. yds. ; 25 per cent, of the muck left in tunnel 8 center-cut holes, 10 ft. each 80 ft. 12 side " " 8 " " 96 " Total ft. drilled per shift 176 Total ft. drilled 2,288, or 4.16 ft. of hole per cu. yd. Total powder, 2,200 Ibs., 4 Ibs. per cu. yd., or 8.46 Ibs. per hole; 13 blasts fired with average advance of 7.86 ft. Crew : I heading boss at $3.25 ; 3 drillers at $2.50; 3 helpers at $1.75 ; i nipper at $i ; I powder man at $i ; I muck boss at $2.50; 9 muckers at $1.50; 3 drivers and mules at $2.25; i trackman at $1.50; 2 sumpmen at 75 cts. Outside labor: 2 bellmen at 75 cts. ; 2 topmen at 75 cts. Power, etc. : i engineer at $15 a week; I engine driver, $9; i fireman, $12.25; i elec- trician, half week, $6; I machinist (half week), $7; I car- penter (half week), $7.50; i blacksmith, $15; i blacksmith helper, $10; i time keeper, $14; i general foreman, $35. Record Run South Headi-ng. Cu. yd. Drill crew $0.42 Muck crew 50 Transporting 31 Outside labor 09 Enginemen, etc 18 General foreman .06 Total labor $1.56 5 tons coal at $5 (7 days), $175; Oil and candles, $12.50; steel, $5 35 2,200 Ibs. rackarock at i6 l / 2 cts 65 Total $2.56 Interest on plant .37* $2.93 Too low. COST OF RAILWAY TUNNELS. 321 The record week's run on North Heading, Shaft 16 (head- ing 9 x 1 6 ft.), with plant same as above, but better over- hauled, was as follows: Work was pushed to the utmost for 7 days in mica-schist ; lo-hr. shifts. In 10 previous weeks the average had been 46.9 ft. per week. This week's record was 127 ft.; area, 125.6 sq. ft.; 591 cu. yds.; 15 to 20 per cent, of muck left in tunnel. Distance from compressor, 3,965 ft. ; loss of pressure, 20 Ibs. ; 2 Rattler drills. 8 center-cut holes, 8^ ft. each 68 ft. 10 side " " 8 " " . . 80 " Total 148 " Total: 1 8 shots; 324 holes; 2,664 ft- drilled; or 4.33 ft. per cu. yd. ; 2,050 Ibs. 60 per cent, powder ; or 3.46 Ibs. per cu. yd. ; or 6.33 Ibs. per hole ; advance, 7.05 ft. per shot. Mucking 2.3 hrs. Drilling 5.5 " Charging 0.5 Firing i.i " Clearing of smoke 0.6 " Other Examples of Rapid Heading Work. Lin. ft. per No. of Size of 3. day (lohrs.) Drills. Heading 10.52 4 14x14 10.21 4 ft / 11.75 2 8x 16 10.05 3 " 12. l6 3 " 15.07* 3 9x17 Days. 22 26 54 60 7 60 7.81 9x16 7 18.14* 2 9x16 Rapid bench work: In 84 days, with 2 drills, averaged 6.85 lin. ft. per day ; 3,360 cu. yds. ; 4 holes averaging 9 ft. * Above given in detail. 322 ROCK EXCAVATION METHODS AND COST. deep per blast; 4,788 ft. drilled; 1.4 ft. per cu. yd.; 7,500 Ibs. powder, or 2.23 per cu. yd. ; bench worked at both ends. The above are record costs. The following are average costs, and are double the costs on the record runs : Heading, area 105 sq. ft. Cu. yd. Inside labor $3-34 Outside labor 94 Coal (3 tons day) 67 Powder at i6 l / 2 50 Interest on plant 37* $5.82 By driving two headings at one time, outside labor cut in two saving ................. 50 Average cost of bench excavation : Area, 167.4 sq. ft. ; 577 lin. ft. in 48 days (two lo-hr. shifts per day) ; 3,578 cu. yds. ; I drill boss, $70 per mo. ; i muck boss, $70 per mo. ; I drill runner, $2.50; i drill helper, $2; 15 muckers at $1.50; I driver and mule, $2.25; i trackman, $1.50; 2 dumpmen at $1.50; i bellman, $1.75 ; i sumpman, $1.75 ; i topman, $1.50 ; outside labor as above given. Cu. yd. Drilling and blasting (532 holes, 9 ft.) . . . .$0.28 Mucking (3,360 cu. yds.) ................. 75 Transporting ............................ 20 Outside labor at shaft ..................... 17 Extra " " " ..................... 05 Enginemen, etc .......................... 17 Machinist, blacksmith and helper ........... 09 Coal (3 tons, at $5 ; oil and candles, at $2 per day) ............................. .23 Powder (7,300 Ibs. J. L. Aqueduct at i6y 2 cts.), etc ............................... 38 * Too low an estimate. COST OF RAILWAY TUNNELS. 323 Interest on plant $-37* Total cost per cu. yd. of bench $2.69 Cost of driving, heading and bench together: 30 lin. ft.; area, 283 sq. ft. ; 314 cu. yds. : Cu. yd. Inside labor on heading 120 c. y. at $3.34 ) <* " " bench 194 c. y. at $1.23 f ' Outside labor 78 Coal, etc 62 Powder (3 Ibs. per c. y. of heading; 2.3 Ibs. per c. y. of bench, at 16^2 cts.) 44 Total for single heading and bench $ The Cascade Tunnel. This* tunnel is described in En- gineering News, Jan. 10, 1901, by Mr. John F. Stevens, Chief Engineer, Great Northern Railway. The tunnel is 13,813 ft. long through the Cascade Mts. on the line of the Great Northern Ry. The width in the clear is 16 ft., and the height from top of rail to bottom of arch is 21% ft. It was begun, from two headings, Aug. 20, 1897, and completed Oct. 13, 1900. A top heading, 10 x 20 ft., was driven from each end ; and the bench was taken out in two lifts. The average monthly progress was 175 ft. at each heading, or 5.76 ft. per day of 24 hours. The best year's work was from June i, 1899, to J une i, 1900, in which time 5,575 ft. were driven from the two headings, the monthly average being 232 ft. per heading. The best month's progress was 527 ft. from two headings ; the best week's progress was 143 ft. from two headings ; the best month's progress from a single head- ing (East) was 301 ft. The rock was medium hard granite, very seamy and very wet. Although hard to drill and blast, the granite disintegrated so rapidly that a temporary timber lining was necessary throughout, and it was afterward re- placed with concrete. * Too low. t Deduct $0.70 reduced fixed charges when two headings are run. 324 ROCK EXCAVATION METHODS AND COST. The work was all done by day labor, no contracts being let. Three 8-hr, shifts were worked. There were 600 to 800 men employed, and they were not very efficient. Four columns in a heading carried 6 drills ($%-m. size). From 24 to 28 holes were drilled 12 ft. in the heading, and fired in three rounds by electricity. Including the bench work there were 14 drills used at each end of the tunnel. Rock from the heading and top bench was wheeled in bar- rows out onto the "jumbo," or "go devil," and dumped through into cars below. A compressed air hoist on the "jumbo" served to lift large rock and to shift the "jumbo" back before firing. Eight electric motor cars were used to haul the muck, etc. One motor hauled 16 to 20 dump cars of i cu. yd. each up the 1.7 per cent, grade to the east portal, at 10 miles an hour. The rails were 5<>lb. rails laid to a gage of 2 ft. Large power houses were built at each portal. The east power house contained one Ingersoll-Sergeant duplex com- pressor, 1 8 x 24 ins. ; one straight line compressor, 18 x 24 ins. ; one Rand duplex compressor, 20 x 36 ins. ; one Buckeye high-speed engine, 12 x 16 ins. ; one Chandler & Taylor high-speed engine, 13 x 14 ins.; six I5O-H.-P. boilers; pumps, dynamos, fans and water heaters. Compressed air was delivered through 6-in. mains to the drills, at an initial pressure of 100 Ibs. The tunnel was lined with concrete from end to end, the temporary timber lining being removed. The concrete is nowhere less than 2 ft., and in places it is 3^ ft. thick; spawls and broken stone were packed above the concrete where necessary. To place the concrete without interfering with the muck trains, a platform 500 ft. long was erected, and the cars loaded with concrete were hauled up an incline by a compressed air hoist. The concrete was dumped on the platform and shoveled into the forms. While this was going on another 5oo-ft. platform was being built in ad- vance. Side walls were built in alternate sections 8 to 12 ft. COST OF RAILWAY TUNNELS. 325 long, the weight of the timber arches being thus transferred to the walls. The concrete arch centers were made in 12-ft. lengths, of which there were ten in each end of the tunnel. When the concrete had set the 12-ft. arch center was lowered with screw jacks onto "dollies," pushed forward 12 ft. and jacked up again. Concrete was mixed, I cement, 3 sand and 5 parts rock. About 95,000 barrels of Portland cement were used in lining the tunnel, an average of 7 bbls. per lin. ft. of tunnel. Work of lining was begun in Dec., 1899, and fin- ished Nov., 1900; more than 1,000 ft. of lining having been placed in Oct., 1900, in the west end, although the general average was about 600 ft. of lining per month from each end. The tunnel was opened for operation Dec. 20, 1900. Mr. Willard Beahan, in a letter to Engineering News, Feb. 28, 1901, adds some interesting facts about the part of the tunnel driven through soft ground, at the start, where only 0.8 ft. per day was averaged. He also says that it was a serious mistake to have driven the heading in rock by hand 300 ft. in advance of the bench while waiting for the power plant to arrive, for the long heading overtaxed the transportation so that work on the heading had to be stopped until the bench was brought up. The use of four drill columns he regards as novel, and adds that there was plenty of room in which to work six drills, and that it was not nec- essary to shift any of the columns in drilling a set of holes. The Kellogg Tunnel. Mr. U. B. Hough, in Engineering News, April 25, 1901, describes a novel method of mucking used in running a large tunnel in the Bunker Hill and Sul- livan mines, at Kellogg, Idaho. The entire length of the tunnel will be 9,000 ft., of which 8,400 ft. had been driven at the time of writing. The rock is quartzite and after blasting is loaded by a No. I drag-scraper, which is hauled up an incline by a hoisting engine, and dumped through a door into the car. Two scraper loads usually fill a i-cu.-yd. car, and never more than three loads. After the first car is loaded, the second car is pulled forward under the door. 326 ROCK EXCAVATION METHODS AND COST. Five men constitute the mucking gang, one operating the hoist, one attending the cars and three loading and attending the scraper. The time required to remove 40 to 50 cu. yds. of waste is 2 to 2^/2 hrs. (not stated whether the yardage is solid or loose measure). The incline, or "mucker," is moved by jacking it up (on four screw jacks) off the floor until the weight is on the moving car ; it is pushed back until advance rails are laid, then it is pushed forward and lowered to the floor again. The hoist is moved in a similar manner by running a moving car under it. Five men consume only 20 mins. in moving both hoist and mucker. The mucker has been in use 15 mos., and is in fair condition. Two drills mounted on one bar are worked in the heading, which is kept 10 to 20 ft. in advance of the bench. A four-ton elec- tric motor hauls a train of 15 loaded cars. Smoke is re- moved through a 22-in. pipe (No. 18 iron) by a No. 9 Sturtevant exhaust fan. This fan. will remove all smoke in 15 or 20 mins. through 8,000 ft. of pipe. The longitudinal pipe seams are all riveted and soldered; and the joints are wrapped with sheeting and painted with tar. In the month of October, 1898, an advance of 354 ft. was made, but the general average has been 7.5 ft. per day, working three 8- hr. shifts. One-third of the tunnel has been timbered. The Pryor Gap Tunnel. Mr. F. T. Darrow describes this tunnel in Engineering News, July 3, 1902. The tunnel is single track, on the line of the "Burlington" in Montana, 38 miles south of Billings. It is 500 ft. long, on a curve, through solid dolomitic limestone. The tunnel section out- side of the timbering runs 18 cu. yds. per lin. ft., and was taken out by a top heading and two benches, each about 9 ft. high. The work was done by contract, actual tunnel work beginning December, 1900. A I6-H.-P. upright boiler fur- nished steam to two 3M$-in. drills in the heading and one drill on the bench. The steam was carried in 2-in. and \y 2 - in. wrought pipe covered with jointed jacketing; and at a distance of 400 ft. from the boiler no difficulty was found COST OF RAILWAY TUNNELS. 327 in running the drills. Two lo-hr. shifts were worked daily, or 13 shifts a week; and, when running well, the advance was 50 ft. a week from one heading. The heading gang consisted of I foreman, 2 drillers, 2 helpers, 6 or 7 muckers, i powderman, beside the fireman and teamster outside. The bench force was about the same, excepting that there was only one driller and helper. In heading work each machine was mounted on a separate column ; and a set of 14 holes 6 ft. deep was put in and fired in four rounds, using 60 per cent, dynamite. The south heading was run in 300 ft., and then stopped, and the bench brought up, the heading gang moving to the bench at the north end, which up to that time had been run without bench excavation. The work was completed May 15. Forty pounds of 60 per cent. Giant and 10 Ibs. of black powder were used per lin. ft., the black powder being used only in the bench. Timbering was put in after the completion of the excavation while the tunnel was in operation. The particular feature of this work is the simplicity of the plant and the effectiveness of the small gang of men. The Busk Tunnel. The following data are given in En- gineering News, Sept. 27, 1894: The Busk Tunnel Ry. Co. built a tunnel 9,395 ft. long on the Colorado Midland R. R. through the Rocky Mts., 11.7 miles S. W. of Leadville. The contract was let to Keefe & Co., and work was begun Sept. 15, 1890. After all but 921 ft. had been driven the work was turned over to the railway company and finished under the direction of their chief engineer, Mr. B. H. Bryant. The tunnel is single track, 15 x 21 ft., with 10.2 cu. yds. per lin. ft. excavation in rock and 13.8 cu. yds. where tim- bered. The heading was 7 ft. high and the full width of the tunnel. The first 8 holes, 8 ft. deep, were drilled in two rows from top to bottom, holes being about 2 ft. apart at surface and converging toward the center. The firing of these holes made a V-shaped opening. A second set of holes was drilled parallel to the sides of the tunnel, and when 328 ROCK EXCAVATION METHODS AND COST. fired the remaining rock was blown into the V-shaped open- ing. The bench was excavated in the same way. The prog- ress was as follows : Driving the 2 headings 1,118 days. Av. daily progress 8.4 ft. Av. daily progress, best month 10.9 " Best month's (28 days) progress, one heading 202.5 " The rock was granite, and in places it disintegrated on exposure, requiring timbering; in other places it was so full of seams as to require timbering ; so that 78 per cent, of the tunnel was timbered. The contractor was paid for the tunnel as follows : 9,393 2/3 ft- of tunnel at $62.50 $587,10375 32,575 cu. yds. enlargement for timbering at $2.50 81,437.50 Cost of timber, 2,723,000 ft. B. M. at $30 81,690.00 Labor timbering at $12 per M . 32,676.00 Total 9,393 2/3 ft. at $82.30 $782,907.50 The plant at the Invanhoe end consisted of three 100- H.-P. boilers, two 20 x 24-in. Ingersoll compressors, one 20 x 24-in. Norwalk compressor, one IO-H.-P. engine to drive electric light dynamo, one 2O-H.-P. engine to drive a No. 6 Blake blower, 14-in. air pipe, two pumps with 14-in. steam cylinders and lo-in. stroke, six 3^ -in. Ingersoll drills (4 in the heading and 2 on the bench), a small traction engine running on a 2O-in. gauge track hauling nine 3~yd. dump cars. Coke was used as fuel for the traction engine, so that the smoke did not inconvenience the tunnel workmen. Sutro Tunnel. Drinker gives in considerable detail the work done in driving the heading of this drainage tunnel in Nevada. The work was begun in 1869 by hand, and in 1874 Burleigh drills were introduced. The heading was 8 x 10 ft., with cut holes 7^ ft. deep and 4^ ft. apart. It is stated that 6 Burleigh drills were operated, but if so they must have been unusually crowded. There were 12 men oper- COST OF RAILWAY TUNNELS. 329 ating these drills on each shift, and these same men were required to do their own mucking besides. Subsequently 4 Ingersoll drills replaced the 6 Burleighs. The rock was a hard trachite and greenstone. In 1875, working three 8-hr, shifts, the average progress of the heading was 72 ft. a week, or 3.4 ft. per 8-hr, shift ; and the best month's advance was 350 ft. During the last 8 mos. of the year 1875 the ac ^" vance was 2,561 ft., which required 9,882 holes (2 to 2 l / 2 - in.) averaging 6.77 ft. per hole, making a total of 66,951 ft. of hole to excavate about 7,680 cu. yds., or 8.7 ft. of hole per cu. yd.; and 16,700 carloads were moved. The powder was No. i giant and the amount used was 2.62 Ibs. per hole, or 3 1 / 3 Ibs. per cu. yd. There were 470 drills sharpened per week, although 1,100 drills were sharpened one week when in very hard rock. There were 105 men employed in and about the tunnel, working in three shifts. In 1877 the best month's advance was 388 ft., which was certainly an ex- cellent record. Musconetcong Tunnel. Drinker describes the work on this tunnel in his book, also in Trans. Am. Inst. Min. Eng., 1875. The tunnel is 12 miles from Easton, Pa., on the Le- high Valley R. R., and was begun in 1872. The material penetrated was 3,731 ft. of very hard syenite gneiss, 460 ft. of limestone and 770 ft. of earth. One shaft was sunk. Top headings 8 x 26 ft. were first started by hand with a progress of 40 to 60 ft. per month. Ingersoll drills were subsequently installed and were operated on two carriages, each supporting three drills. The cutholes were 10^ ft. deep and started 9 ft. apart; the other holes were 12 ft. deep, starting 2^ ins. diam. and ending up iy 2 ins. diam. The 12 cut holes, drilled in pairs, were loaded with 25 Ibs. of No. I dynamite and 50 Ibs. of No. 2, and fired by elec- tricity. No. 2 was used entirely in the squaring up holes. The total charge in the heading was 25 Ibs. of No. I and 245 Ibs. of No. 2, resulting in advance of 10 ft. for 408 ft. of drill holes. About 6 ft. of hole were drilled per cu. yd., and 330 ROCK EXC Ay AT ION METHODS AND COST. about 4 Ibs. of No. 2 and 0.4 Ib. of No. I were used per cu. yd. To drill these 408 ft. of holes required four 8-hr, shifts of six drills on each shift, so that each drill averaged only 17 ft. of hole per 8-hr, shift! The crew on each shift con- sisted of the following men, and I have assumed wages to be as given : 6 drillers, at $3.00 $18.00 6 helpers 2.00 12.00 6 muckers " 1.50 9.00 i nipper " 1.50 1.50 i boss " 3.50 3.50 Total per shift $44.00 The bench was 12 ft. high and a row of four 12-ft. ver- tical holes was drilled 9 ft. back from the face; then two more 12-ft. vertical holes were drilled close up to the sides of the tunnel and 4^ ft. back of the face ; then four bottom, horizontal holes, 10 ft. deep, were drilled into the face close to the floor of the tunnel. These 10 holes were charged with 107 Ibs. of No. 2, and a 9-ft. advance was made by each firing. The bench was kept 500 ft. back of the face, and the bench crew consisted of 3 drillers, 3 helpers, 14 muckers, i nipper and i boss for each shift. The total amount of explosives used in excavating 82,000 cu. yds. of heading and bench combined was 0.34 Ibs. No. I plus 1.71 Ibs. of No. 2 per cu. yd. of tunnel excavation, I exploder and 3 ft. of connecting wire per cu. yd. The plant consisted of 30 drills, 4 compressors, 9 boilers, 2 machine shops, i l / 2 miles of 6-in. air and water pipe, 2 hoisting engines and boilers, pumps, etc. The coal and sup- plies were hauled one mile over rough roads with 4-horse teams, and there were 24 teams. In three years there were 27,000 tons of coal used. The force all told was about 1,000 men. A Tunnel Through the Palisades, N. J. In Engineering News, March 30, 1893, a brief description is given of a tun- COST OF RAILWAY TUNNELS. 33* nel through the Palisades in N. J., about 2 miles north of the Weehawken Tunnel of the West Shore (see Eng. Neivs, June 17, 1882). This tunnel, which was being built by the Hudson R. R. & Terminal Co., was begun Aug. I, 1892, and is 5,070 ft. long, through trap rock. In solid rock the section is 27 ft. wide by 21 ft. high, the roof being an ellipse with a 9~ft. rise. The tunnel is driven by a top head- ing 7x18 ft., 24 holes 8 ft. long being drilled in the face ; 8 center-cut holes and two rounds of 8 holes each are fired in three blasts. Rand and Ingersoll drills with 2^2-in. starting bits are used, and 30 ft. for each drill in a lo-hr. shift is considered good work. The dynamite is 60 per cent. A derrick car is used in mucking the benches which break out heavy; this car lifts the body of a mucking car from the track along- side and places the body close up to the bench to be filled. By this means large stones can be rolled into the car body. Wheelbarrow loads from the heading are dumped from staging into these car bodies. The derrick car also handles heavy stones. The Tequixqueac Tunnel. In Engineering Record, Feb. 29, 1896, an abstract is given of an article in Engineering on the Tequixqueac Tunnel, for drainage of City of Mexico. The tunnel is 6% miles long in sandstone; circular cross- section, 14 ft. diam. inside brick lining. The shaft-sinking method is outlined. Water was present in large quantities. Tunnel headings were 6^4 ft. high, 5 ft. wide at bottom and 4 ft. at top, inside timbers, with a water ditch 3 ft. deep. Six holes 6^2 ft. deep were drilled in the face and loaded with 6 Ibs. of Nobel dynamite. Dynamite cartridges were dipped in grease. Drills were put into the holes to keep the charge down. Each blast threw down 8 cu. yds. of rock upon timber platform. Cars held 12 cu. ft., on 2-ft. gage, 12-lb. rails on iron ties, in 2o-ft. lengths. No. I Root blow- er, 6-in. outlet, forced air through 6-in. spiral pipe to within 10 ft. of face, which was always sufficient for 2,100 ft. from 332 ROCK EXCAVATION METHODS AND COST, shaft. Men worked under sub-contractor in 4-hr, shifts, then rested 4 hrs. ; then worked 4 hrs. more, changing fore- men every shift, which proved a splendid arrangement. There were 60 men on a heading shift thus : 2 timbermen, 4 drillers, 2 mucking debris, 22 loading cars and running them (2 pushing a car), 2 plate layers, 4 men timbering, I ven- tilator man, 10 men digging water channel with bars, i oiling and greasing, 2 hookers on, 2 dumpmen, overseers, foremen and timekeepers. Each contractor was required to make a minimum progress in driving heading of 26 ft. in 24 hrs. As an actual fact, one heading was driven 43^ ft. in 24 hrs., and 728 ft. were driven in a month ! So far as I know this record has never been equaled. It is stated that the organization of the forces was perfect, and that the working of 4-hr, shifts was a pronounced advantage, as the men worked with great energy even in very wet head- ings. It will be noted that each hand driller averaged not less than 13 ft. of hole (two 6^-ft. holes) in 8 hrs. It is not clear how 22 men could have been employed in so nar- row a heading loading cars and tramming; certainly their yardage output per man was nothing remarkable, except for its lowness. The Simplon Tunnel. Americans may well study the methods by which this tunnel has been driven ; for to have maintained a rate of speed practically double the rate usu- ally made in good ground in this country is, of itself, suffi- cient to rivet the attention. In Engineering News, Aug. 30, 1900, is printed a valuable paper on this tunnel, by Mr. C. B. Fox, from which the following data have been abstracted : The Simplon Tunnel pierces the Alps between Italy and Switzerland, and its length when completed will be 64,725 ft, or nearly n miles. It will be completed in 1904. One full' sized railway tunnel (No. i) is being driven, and the heading of what will eventually be another tunnel (No. 2) is also being driven parallel with the main tunnel ; the two headings being 56 ft. apart c. to c. The' headings are bottom COST OF RAILWAY TUNNELS. 333 headings. Cross-headings connect the two, every 660 ft. The material is all carried to the portals, there being no shafts. The cross-section of tunnel No. i is 13.6 ft. at the formation level, increasing to 16.4 ft., with a total height of 18 ft. above the rails, giving an area of 250 sq. ft. The tunnel is lined throughout. Tunnel No. 2, which is being left as a heading, is 6.6 ft. high x 10.2 ft. wide, and is lined only where necessary. Cross-headings every 660 ft., mak- ing an angle of 56 with the axis of the main tunnel con- nect the two tunnels. The two parallel headings, each 59 sq. ft. in area, are driven by machines, the work being carried on day and night 7 days in the week. No. I is then enlarged to full size by hand drilling (one holding and one striking). No timbering is required in the north heading. Steel centers are used for placing the masonary arches. On the south headings a softer rock is encountered, requiring timbering. The excavated material is hauled, on a track having 2.6-ft. gage in 2-yd. cars drawn by a small locomo- tive designed with a very large boiler to avoid firing in the tunnel a feature worthy of note. The drilling machines are of the Brandt rotary type that cuts a core. A small four-wheeled truck carries a horizontal beam, the shorter arm of which supports the horizontal bar on which the drills are mounted, the longer arm being coun- terweighted. The bar is braced against the sides of the tun- nel much as an ordinary column is held, except that, instead of screw jacks, a plunger operated by water pressure is used. Three or four machines are mounted on the bar. The drill is rotated by water, acting under pressure in two pis- tons, from which screw gearing conveys the motion to the drill rod. The total loss of power by friction is not over 30 per cent. The drill makes only 5 to 10 revolutions per min., according to the nature of the rock. The water for running each drill is 240 gals, per min. delivered under the enormous pressure of 1,470 Ibs. per sq. in. The water en- ters the tunnel in wrought iron pipes, 3^ ins. inside diam. 334 ROCK EXCAVATION METHODS AND COST. and 3 /i6 m - thick, made in lengths of 26 ft. In 3,750 ft. of tunnel the loss of pressure due to friction in the pipes is 147 Ibs. per sq. in. The drill itself is a hollow pipe of tough steel, 21/4. ins. outside diam., provided with 3 or 4 sharp teeth, and it virtually chips or saws its way into the rock without pulverizing it as does a diamond drill. The ma- chine has a feed of 2 ft. 2 ins., and when the drill reaches the end of the feed, it is pulled out, unscrewed and an ex- tension tube is screwed on, the whole operation taking only 15 to 25 sees. (Note: This is a remarkably short time compared with the ordinary percussion drill.) The water after passing through the motors passes down through the drill tube and serves to wash out the chips and keep the bit cool. A hydraulic piston advances the machine and gives a pressure of 10 tons on the bit. The holes drilled are com- paratively shallow, 4 ft. 7 ins. and 2^ ins. diam. Three machine drills put down 10 to 12 of these holes in gneiss in 2J/2 hrs., or at the rate of 15 to 18 ft. per hour per drill; thus enabling an advance of 18 to 19^ ft. to be made in heading (59 sq. ft.) every 24 hrs. The record thus far made for a month's work is 682 ft. in the north heading, for December, 1903. During the last three months of 1899 the work done was as follows : In the north headings there were three ma- chines in tunnel No. I and two in the parallel heading of No. 2. The total distance driven in these two headings was 2,985 ft. in 89 days (24-hr.), or an average of 16.8 ft. per heading per day. The average cross-section of each head- ing was 57 sq. ft., so that a total of 6,409 cu. yds. was ex- cavated. This required 507 attacks and 3,066 holes having a total depth of 26,600 ft., 14,700 re-sharpenings of the bits and 44,000 Ibs. of dynamite. This is equivalent to 4.16 ft. of hole and nearly 7 Ibs. of dynamite per cu. yd. The aver- age period of a drilling attack was 2 hrs. 45 mins., while charging, firing and mucking took 6 hrs. 35 mins. There were 648 men and 29 horses on inside work, and 541 men on outside work. COST OF RAILWAY TUNNELS. 335 On the south headings, where the rock is much harder, there were three machines in each of the two parallel head- ings. The total length excavated, with a cross-section of 62 sq. ft., was 2,880 ft., or 6,700 cu. yds. in 91 days, or 15.8 ft. advance in each heading every 24 hrs. This required 758 attacks, 7,940 holes with a total depth of 33,000 ft. and 56,000 Ibs. of dynamite. Thus in hard gneiss nearly 5 ft. of hole, and 8^ Ibs. of dynamite, were required per cu. yd., and each bit drilled 6 l / 2 ins. before re-sharpening. There were 496 men and 16 horses working in 8-hr, shifts on the inside work, and 346 men on outside work. The organization of the work is as follows: Two men operate each drill, one feeding the bit forward, the other changing bits. There are three of these drill gangs in a heading, with one foreman and two men in reserve. Three or four holes are drilled in the center to a depth of 3^4 ft- and 7 or 8 holes are drilled around the outside of the face to a depth of 4.6 ft. The fuses of the center holes are brought together and cut off shorter than the others. The drill carriage is run back; a steel flooring is laid for a distance of 30 ft. back of the face and covered with debris to prevent damage to it by flying rocks. The blast is fired, and imme- diately afterward a valve is opened letting five jets of water play upon the rock to lay the dust. A truck is brought up, and four men clear a passage in front, two using picks and two using shovels, while on each side and behind are as many muckers as space will permit. The stone is thrown to both sides and into the car, shoveling being greatly facilitated by the steel flooring. The steel plates are taken up when cleared, and the car pushed forward. Finally the drill car- riage is run forward, as soon as a way has been cleared, and the muck at the sides is removed at leisure during the drill- ing. The time consumed in an attack is : Bringing up and adjusting drills .... 1 / 3 hr. Drilling 1 24 to 2 hrs. Charging and firing /4 hr. 336 ROCK EXCAVATION METHODS AND COST. Clearing away muck 2 hrs. Total 4^ to $y 2 hrs. This attack usually results in advance of 3^4 ft., or 18 ft. in 24 hrs. A mechanical plow has been tried for clearing away the muck ; water jets have also been tried, but thus far without success. Air is forced in at the portal, which is kept closed by doors, but to carry away the smoke rapidly an 8-in. pipe (480 ft long) is lead up to within 45 ft. of the heading face, and air is driven through by a water jet. Each face receives 800 cu. ft. of fresh air per min. One jet of water ( 1 / 16 in. diam.) from the high pressure main supplies 1,000 cu. ft. per min. at the end of 480 ft. of 8-in. pipe. See Engineering News, May 27, 1897, for cross-section and plan. See also Aug. 13, 20, 27, 1903, for operating details. Tunnel Near Peekskill, N". Y. The following data are given in Engineering News, Dec. 17, 1903, by Mr. Geo. W. Lee, engineer for Sundstrom & Stratton, the contractors who built the double-track tunnel described. The tunnel is only 275 ft. long, and is on the line of the New York Central R. R., 2,y 2 miles north of Peekskill. The yardage as shown on the plans was 7,028 cu. yds., but as the rock lay in strata dipping at an angle of 45, it broke out on the uphill side so as to leave large pockets, in 'consequence of which the contractor took out 10 per cent, more rock than he was paid for. Owing to the seamy condition of the rock, and the proximity of the tunnel to the main line traffic, very light charges of dynamite were used, which increased the cost and delayed the progress. Rand steam drills, 3-in., were used. A heading 8 x 10 ft. was run and the bench was kept close behind. Rock from the heading was removed in small narrow gage cars; rock from the bench was loaded into standard gage cars by derrick cars. The following was the cost of the tunnel excavation : COST OF RAILWAY TUNNELS. 337 Equipment (less present value), supplies and re- pairs $2,893.52 Dynamite and exploders 1,604.58 Coal 57o.8o Oil, waste, etc. . 92.80 Lumber for houses and shops 129.88 Miscellaneous 92. 10 Labor 22,212.86 Total ................................ $27,596.54 Average cost per cu. yd. paid for ............. 3.93 " " " " taken out ............ 3.54 The tunnel was lined with 1 :2 14 concrete ; 692 cu. yds. in the bench walls; 932 cu. yds. in the arch; the portal head walls were of 1 13 :6 concrete, 324 cu. yds. The cost of the concrete was as follows for the 1,948 cu. yds.: Cement at $1.63 per bbl ..................... $5.755-5 Sand at 75 cts. per cu. yd .................... 662.94 Crushed stone at 80 cts. per cu. yd ............. 1,303.20 Lumber : Mixing platforms and runways ........ $336.89 Ribs, including hand sawing ........... 234.10 Backing boards ...................... 134-44 Lagging ............................ 341.04 Sheathing .......................... 268.49 Plates, sills, studs and braces .......... 182.75 Coal ...................................... 1 18.73 Oil ...................................... 16.12 Hardware, nails, spikes, etc ................... 224.39 Tools ................ ...... ............... 181.10 Freight on stone, cement, etc ................. 3,089.86 Labor, including supt., foreman, etc ............ 8,036.31 Total, $10.72 per cu. yd $20,885.86 338 ROCK EXCAVATION METHODS AND COST. In the approaches to the tunnel and in widening cuts south of the tunnel 45,698 cu. yds. of rock were removed. On account of proximity to traffic, blasting could be done only at limited periods, which made the cost of excavation high. Rock was loaded on flat cars with stiff leg derricks provided with bull wheels. The cost was as follows: Equipment (less present value), supplies and re- pairs $11,673.60 Dynamite and exploders 6,588.82 Coal 2,490.13 Oil, waste, etc 37-59 Lumber for buildings 634.22 Miscellaneous 373. 19 Labor 69,550.66 Total $91,681.21 Average cost per cu. yd. paid for 2.24 " " " " taken out 2.01 Cost of Lining Tunnels. (The data on the tunnel near Peekskill, just described, should be consulted for data on concrete lining.) Drinker gives the following data on the lining of Carr's Tunnel (825 ft.) on the Pennsylvania R. R. in 1868-1869. Brickwoik: 609,000 brick in the arch (5 per cent, broken and lost) ; 10.44 bushels of neat cement (no sand used in the mortar) laid 1,000 bricks, the mortar form- ing 30 per cent, of the brick masonry ; the arch was 25 ins. thick, 245/2-ft. span and 9- ft. rise : Cost per M. Bricks f. o. b $8.80 Loss in handling 51 Unloading and delivering 1.92 Laying 5.84 Cement 5.10 $22.17 COST OF RAILWAY TUNNELS. 339 Bricklayers received 40 cts. per hr. ; helpers, 17^ cts. per hr. ; carpenters, 27^ cts. per hr. ; laborers, 17 cts. per hr. Stonework: 1,730 perches (25 cu. ft.) of rough masonry for side walls, presumably sandstone; 187 perches of ring stone ; 25 perches wasted in dressing. The bench walls were 4 ft. wide at the bottom, 3 ft. at the top and 13 ft. high : Cost per perch. Quarrying (1,730 perches) $4.80 Cutting (1,730 perches) 4.36 Hauling (1,942 perches) 1.06 Handling and laying (1,917 perches) 2.80 Cement, 1.65 bu. per perch (8 1 / 6 per cent, of the masonry 81 Total $13.83 Stone cutters and masons received 35 cts. per hr. ; quarry- men, 17^ cts.; laborers, 17 cts. The stone side walls were laid in 8 courses averaging 2 ft. thick each; hence there were 52,800 sq. ft. of beds cut; and estimating each stone 3 ft. long and dressed for 1^/2 ft. back of the face on joints, there were 14,300 sq. ft. of joints; making a total of 67,100 sq. ft. of cutting which cost 11.2 cts. per sq. ft. This is said to have been too high a cost, if the measurements were correct. Arch centering cost $1,400, to which was added $600 for moving the centering forward from time to time; making $2.40 per lin. ft. of tunnel, to which must be added $0.70 per ft. for scaffolding. In Engineering News, Oct. 25, 1894, is given an abstract of a paper read before the Montana Society of C. E.'s, by Mr. H. C. Relf, on the lining- of the Mullan Tunnel on the Northern Pacific Ry. with masonry to replace timber. The tunnel is 3,850 ft. long, 20 miles west of Helena. Falls of rock and fires in the tunnel had caused numerous delays. The original timbering consisted of sets 4 ft. c. to c. of 12 x 340 ROCK EXCAVATION METHODS AND COST. 12-in. timbers, with 4-in. lagging. The size was 16 x 20 ft. in the clear. Concrete side walls (3<>in.) and four-ring brick arch were built in place of the old timbering. A 7- ft. section was first prepared by removing one post and supporting the arch by struts. Two temporary posts were set up and fastened by hook bolts; and a lagging was placed back of them to make forms to hold the concrete. Several of these 7~ft. sections were prepared at a time, each two being sepa- rated by a 5-ft. section of the old timbering. The mortar car delivered Portland cement mortar (i to 3) through a chute, making an 8-in. layer of mortar into which broken stone was shoveled until all the mortar was taken up by the stone voids. In 10 to 14 days the walls were hard enough to support the arches which were then allowed to rest on the walls, and the posts of the remaining 5-ft. sections were removed, and concrete placed as before. About 4 parts of mortar were used to 5 parts of broken stone, which is a very rich concrete. The average progress per working day was 30 ft. of side wall, or 45 cu. yds. ; and the average cost, in- cluding removal of old timber, train service, engineering, superintendence and interest on plant, was $8 per cu. yd. of concrete wall. From 3 to 9 ft. of brick arch were put in at a time, depending upon the nature of the ground. To re- move the old timber arch, one of the segments was partly sawed through, and a small charge of dynamite exploded in it; the debris being caught on a platform car, from which it was removed to another car and conveyed away. The center was then placed, and the cement car used to mix mor- tar on. Brick were 2.y 2 x 2^ x 9 ins., four ringings, mak- ing a 2O-in. arch and giving 1.62 cu. yds. per lin. ft. of tunnel. The bricks were laid in rowlock bond. Two gangs of 3 bricklayers and 6 helpers each, laid 12 lin. ft., or 19.4 cu. yds., of brick arch per day. The brick work cost $17 per cu. yd., making the total cost of tunnel lining $50 per lin. ft. The work was still in progress at the time of writing. CHAPTER XVII. COST OF DRIFTING, SHAFT SINKING AND STOP1NG. Definitions : Adit, a small tunnel driven from the surface into a hill. Breast, the face or working end of an adit, drift or stope. Cross-cut, a small, underground, horizontal opening driv- en across the trend of the vein or formation. Development, or Dead Work, the shafts, drifts, cross-cuts and other openings made preparatory to stoping the ore. Drift, a small, underground opening that follows the di- rection of the vein or lode. Incline, a shaft-like opening extending downward from the surface at an angle of less than 90. Level, a horizontal opening in a mine connecting with a shaft or incline. Levels are usually 100 ft. apart, occasion- ally 150 ft. Raise, or Upraise, an opening driven up from one level to another. Shaft, a vertical opening extending from the surface, and used as an entrance and exit. Stoping, mining the mass of ore between levels. Winze, a small opening connecting one level with another, as for ventilation. General Considerations. The reader is supposed to be tolerably familiar with one or more - books on mining, such as Ihlseng's, or Foster's, but a few remarks may help to a clearer understanding of the reasons why underground work is so much more expensive than open-cut work. As we have seen in the last chapter, wherever a narrow face in a tunnel is exposed to attack by blasting, the explosive has a great deal of work to do per unit of excavation, because of the great area per unit that must be sheared off. To place the larger amount of explosive required means either the 342 ROCK EXCAVATION METHODS AND COST. drilling of drill holes having a large diameter, or the drilling of holes close together. Miners in the days of hand drilling were obviously compelled to choose the latter method ; and, even since the introduction of dynamite and power drills, the practice has continued to be close spacing. I am not at all sure, however, that this is the best practice ; and I look to see more powerful drills used in the future for drilling holes of greater diameter, spacing the holes farther apart. The advantage of this method has been proved in subaque- ous excavation, and there is every reason for believing that larger holes will prove more economic in underground work. In underground work, since derricks cannot be used, it is necessary to break up the rock to sizes that will require little or no sledging, mudcapping or blockholing, before loading by hand into cars. This means likewise either close spacing of drill holes, or drill holes of large diameter. We see, therefore, that in any case more work in drilling and more explosives are required to break rock underground than in open cuts. In addition to these greater costs are the costs of timbering, or filling, of pumoinp". of lighting, of hoisting, of greater delays after blasting, of ventilation, etc. Finally, the miners' unions have gradually raised rates of wages to a point that makes comparison of open-cut work with underground work impossible, if the dollar is the unit of comparison. Shaft sinking is well known to be more expensive than tunneling, ton for ton, or yard for yard ; and it is impossible to sink a shaft with anything like as great rapidity as a tun- nel of equal size can be driven. The chief reason for the slowness of shaft sinking lies in the fact that the greater part of the muck must be removed after each blast before drilling can begin ; whereas in a tunnel the drillers can be- gin while the muckers are still at work. Timbering a shaft also delays excavation and hoisting to a far greater degree than tunnel timbering. It is harder to ventilate a shaft, and obviously harder to drain a shaft than a tunnel. The fixed expense of a hoisting plant and engineer is out of all pro- COST OF DRIFTING, SHAFT SINKING, STOPING. 343 portion to the small amount of material hoisted daily. All these factors, and certain others of less importance, make shaft sinking slower and more expensive than tunneling. The number and size of drill holes and the amount of ex- plosives are practically the same in shafts and tunnels of equal areas. As the depth of the shaft increases, there comes a time when work is retarded by the speed and capacity of the hoisting plant. The best record of speed of shaft sink- ing for moderate depths is that given by Mr. Edward J. Way, in the Trans. Am. Inst. Min. Eng., Feb., 1904. A shaft, 6 x 21 ft., was sunk 858 ft. in five months; during the last month, May, 1903, the record was 213^ ft. In all there were 4,032 holes drilled to an average depth of 7 ft. 2 ins. ; 418 cases of gelatine, 2,475 co ^ s f ^ use 86 boxes of detonators and 207 boxes of candles were used. This work was done in South Africa, and the costs are given, but un- fortunately Mr. May does not give the organization of the force nor the rates of wages. The following examples of cost will give a fair idea of the range ; but I trust that some of my readers will be kind enough to send me other detailed examples, stating condi- tions, so that future editions of this work may be of greater value both to the experienced as well as the inexperienced mining man. Cost of Tunneling Melones Mine. In Trans. Am. Inst. Min. Eng., 1898, Mr. W. C. Ralston gives data of cost of driving an adit at the Melones Mine, Calveras Co., Cal., in 1898. The work consisted in extending a tunnel that was already 1,080 ft. long. The tunnel was 7 x 8 ft. in the clear; grade, l / 4 per cent.; 12-lb. rails; 22-in. gage; ties, 4x6 ins., 3 ft. c. to c. ; walking plank, 2 x 20 ins. An Ingersoll- Sergeant compressor, class "B," driven by a 5-ft. Pelton water wheel, delivered air to an 8-in. pipe at a pressure of 200 Ibs. When water was scarce a Nagle engine, 12 x 16, was used. A No. 4^ Baker blower, run as an exhaust, sucked air through a n-in. pipe. In 255 days only 2 were lost. The average progress was 344 ROCK EXCAVATION METHODS AND COST. 10.22 ft. per day, or 306.9 ft. per month, working from one face. The best run for two consecutive weeks was 184 ft., or 92 ft. per week. The rock was firm greenstone (diabase) , brown slate and talc schists filled with quartz stringers. Only nine sets of timbers were used. The work was rushed, and no especial effort was made to economize. Three 8-hr, shifts of 7 men each (4 drillers and 3 muckers) were worked. Two 12-hr, shifts were worked, each with a team and driver and an engineman. One lo-hr. shift was worked with a blacksmith and helper, a mechanic and an outside- man. Total, 29 men. Two Ingersoll drills, 3^-in., were used, and the repairs on them were only $91 for over 2,600 ft. of tunnel. MELONES MINE (1898). Actual cost (exclusive of management) of 2,608.5 ft. of tunnel. Cost per Lin. Ft. Labor (29 men) $19,501.46 $7.47 Powder, 2,000 Ibs. No. i Hercules @ 16.6 cts... j Powder, 25,500 Ibs. No. 2 Hercules (40%) [3,405.65 1.30 11.9 cts ' Fuse, 74,000 ft. @ 51.7 cts. per 100 Caps, 200 boxes @ 60 cts. per 100 C Wood, 333^ cords @ $5 1,667.50 .63 Water, 15 cts. per inch 828.50 .32 Coal, 11,591 Ibs. Cumberland @ $15 179-43 -06 Foot plank, ties, and 9 sets of timbers, 8,466 ft. B. M. @ $20 per M 169.32 .06 Candles, 3,040 Ibs. @ 7 l / 2 cts 262.04 .10 Steel rails, 21,555 Ibs.', i l A and 2^/4 cts 567.62 .22 Air pipe, n-in., 18 cts. and 30 cts \ Air pipe, 3-in., 22 cts | 1,042.45 .45 Water pipe, 2-in., ii*4 cts ) Horse feed : hay, i l / 2 cts. ; barley, .019 ct 267.16 .10 Steel, drill parts, oil and tools, etc ' 316.92 .12 Total $28,708.25 $11.02 N. B. The air and water pipes used in running different cross cuts were not left in place, but were moved as needed. Of the 21 miners, six received $3 a day, the rest $2.50 a day, and carmen $2 a day. Powder was used liberally to pulverize the ore. COST OF DRIFTING, SHAFT SINKING, STOPING. 345 Cost of Tunneling, Hogsback Mine. At the Hogsback Mine, Placer Co., Cal., the force was 21 men divided into 3 8-hr, shifts of 5 men each; two 12-hr, shifts of an en- gineer, driver and horse on each shift ; and two ic-hr. shifts of blacksmith. The average hardness was the same as at the Melones Mine, but the blocky nature of the ground per- mitted more effective blasting, and only half as many holes were drilled. HOGSBACK MINE (1888). Actual cost (exclusive of management) of 1,559.6 ft. of tunnel. 7 X 8 ft. Cost per Ft. Labor $12,131.49 $7.77 Powder, 10,021 Ibs. No. 2 @ 14)^ cts 1,478.10 .90 Fuse, 23,045 ft. @ 54^ cts., caps @ 80 cts 165.59 .10 Wood, 522 cords @ $2.75 1,435-5^ -92 Charcoal, 1,580 bu. @ 20 cts 316.00 .20 Candles, 1,755 Ibs. @ 13*4 cts 23253 .14 Gang plank and ties, 7,624 ft. B. M. @ $22.50. . 171.54 .10 Timbers, 21 sets @ $1.80 37-8o .02 Steel rails, etc. (i6-lb.), 20,048 Ibs. @ 4 cts.. 801.92 .51 Air and water pipes, 3-in. @ 29^/2 cts. ; i-in. @ &/4 cts 761.43 .48 Horse feed: hay, 3 cts.; barley, 3 cts. per Ib. . 349-6o .22 Steel, drill parts, oil, tools, etc 916.33 .58 Total $18,797.83 $11.94 N. B. Each man received $3 a day. COMPARISON OF BEST WEEK'S RECORD IN EACH MINE. Melones. Hogsback. No. of men 31 20 No. of holes drilled, 5 ft. each 291* 150! Holes reblasted 6 n Time used in drilling 45 hrs.* 26 hrs.f Average time drilling per shift 2^ hrs. ij4 hrs. Powder, Ibs 925 344 Candles, Ibs 77 72 Wood consumed, cords None. 21 * 6.47 ft. of hole per hr. of actual drilling. t 5.77 ft. of hole per lir. of actual drilling. 346 ROCK EXCAVATION METHODS AND COST. Rock extracted per shift, cars 23.19 21.8 Rock extracted for week, 3 shifts, 7 days. 487 cars. 458 Progress for week, ft 92 73.6 Cu. yds. solid rock (7X8) 191 149 Previously reported 2,310 404 Labor expenses for week $55175 $43575 Observe that a 7 x 8-ft. tunnel has 2.08 cu. yds. solid rock per running ft., and taking the average runs at the two mines we have: Per Cu. Yd. Rock in Place. Melones. Hogsback. Powder, No. 2, 40% Hercules 5^ Ibs. 3% Ibs. ruse i3 l /2 ft. 7 ft. Labor (exclusive of management) .... $3.60 $37 Ft. of hole 7-6 5 Observe that each car held about 4 / 10 cu. yd. solid rock at Melones and 1 / 3 cu. yd. at Hogsback. Cost of Sinking and Sloping at the Utica Angels. In Trans. California Miners' Assoc., 1899, Mr. J. H. Collier, Jr., gives the following data on mining at the Utica Angels, Calaveras county, Cal. : The mine is in a mineralized zone of crushed diabase more or less altered to schist, being in the celebrated "Mother Lode." The ore is a nearly vertical quartz vein carrying free gold and pyrites. The method of timbering and stowing or filling is used, no opening over 16 ft. high being left. Waste from prospect cross-cuts is used for stowing. In stoping two lo-hr. shifts of 50 men per shift, supply a 6o-stamp mill with 300 tons of ore per day. The cost of labor in stoping is as follows per shift : 12 miners, at $3 $36.00 12 helpers, at $2.50 30.00 15 shovelers, at $2.50 37-5 6 men tramming, at $2.50 JS- 00 5 timbermen, at $3 I5-OO Total labor stoping 150 tons $133.50 The ore is loaded for hoisting into skips from chutes. COST OF DRIFTING, SHAFT SINKING, STOPING. 347 In shaft sinking, after removing the surface soil, men begin with churn drills, having a 2-in. bit to start with, and tapering to i% ins. at a depth of 6 or 7 ft. After reaching solid rock four air drills are used, two at each end of the shaft on bars about 3 ft. above the bottom. Eight rows of holes are drilled across the short way of the shaft, three holes to a row, 6 to 7 ft. deep ; six holes making the V-cut. Each hole is charged with 6 to 9 sticks (i^g x 8 ins.) of 40 per cent, dynamite, and the firing is done with a battery. The force consists of 6 machine men and 6 helpers, divided in three 8-hr, shifts; 2 enginemen on 12-hr, shifts; 2 ma- chine men with 2 helpers and 3 timber men, who work only when machines run. Each man receives $3 per shift. A three-compartment shaft (7 x 16 ft. outside of timbers), compartments 4 1 / 3 x 5 ft. each, was sunk 825 ft. in 7 months. The timber sets are 5 ft. apart and 2-in. lining is used. The author gives a good description of framing and placing the timbers. Drifts are timbered with two 7-ft. legs set 6 ft. apart at the bottom and a 5-ft. cap on the top. Machine drills put in three horizontal rows of holes, four holes in a row, the center holes forming a vertical V-cut. In talc and mica- schist the drill clogs badly on down holes. In one case a 7-ft. dry (up) hole was drilled in y 2 hr., whereas it took 2 hrs. to drill a 7 ft. down (wet) hole. A jet of water under pressure enables the drills to cut much faster on down holes. Cost of Sinking and Drifting at the Lincoln Gold Mine. The cost of sinking the Lincoln shaft at Sutter Creek, Amador county, Cal., is given in detail in the fifth annual report of Mr. E. C. Voorheis, Superintendent of the Lincoln Gold Mine Development Co. Mr. Voorheis has given me certain additional data not contained in the regular report, as follows : In shaft sinking the men work 8-hr, shifts, but in drifting 10-hr, shifts. The average depth of each drill hole in shaft sinking is about 6 ft., but in drifting 5 ft. The drilling was done by power, using the "Baby" giant drill manufactured 348 ROCK EXCAVATION METHODS AND COST. by the Compressed Air Machinery Co., of San Francisco. The powder used was Herclues, 40 per cent, nitroglycerin, and the fuel for steaming was crude oil delivered at the mine at $1.50 per bbl., of 42 gallons. The work of sinking the Lincoln shaft was completed May 24, 1902, sinking from a level of 1,260 down to the 2,ooo-ft. level, a distance of 740 ft. The size of the excavation is 8 x 17 ft. Material en- countered in sinking, greenstone and hard black slate. The labor cost of sinking and putting in timbers was as follows : It required 3,864 blasting holes drilled in the bot- tom of the shaft, or 5.2 per foot of shaft, which took : 2,956 days' labor at $2.75 per 8-hr, day $7,129.00 i day foreman, 350 days, at $4 1,400.00 i night foreman, 282 days, at $3.25 916.50 Total labor cost of sinking 740 ft. and putting in fimbers $9,445.50 Labor cost per ft. of sinking 740- ft. shaft. .$12.76 12,450 Ibs. Hercules powder used, costing 1,307.25 Cost of powder per ft. of shaft 1.77 Amt. of powder per ft. of shaft, 16.8 Ibs. 35,800 ft. of fuse used, costing 125.30 Cost of fuse per foot of shaft 17 Amt. fuse per ft. of shaft, 48.4 ft. 46 boxes of Lion caps were used, costing. . 46.00 Cost of caps per ft. of shaft 06 2,400 Ibs. of candles used, costing 288.00 Cost of candles per ft. of shaft 39 Amt. candles used per ft. of shaft, 3.2 Ibs. 148 sets of timbers, requiring 207,200 ft. of lumber; average cost, $18 per M 3,729.60 Cost of lumber per ft. of shaft 5.04 Amt. lumber per ft. of shaft, 280 ft. Total cost, labor, lumber, light, etc. . . $14,941.65 Cost per ft. for labor, lumber, light, etc.$2O.i9 COST OF DRIFTING, SHAFT SINKING, STOPING. 349 Total cost, labor for engineers, black- smiths, framing timbers, skip tenders . . $6,224.00 Cost of top expense per ft. of shaft $8.41 Total cost for fuel for sinking 740 ft 5*893.50 Cost of fuel per ft. in sinking 740 ft 7.96 Total cost of sinking shaft, including all expenses except office expense.. $27,059.15 Total cost per ft. of shaft $36.56 During the time the shaft was being sunk 60,025 tons of water were hoisted, or 14,406,200 gallons. 9,456 tons of waste were hoisted from the bottom of the shaft to the sur- face, which added to the water would make a total of 69,481 tons hoisted to the surface during the time the shaft was being sunk. On July i cross-cutting for the vein channel was begun, starting from the north side of the shaft and gradually turning to the west, until a point at right angles to the foot wall of the shaft, which is at right angles to the formation of the ground, was reached. This cross-cut has been ex- tended in a westerly direction 642 ft. At a point 187 ft. west of the foot wall of the shaft the cross-cut passed through a fissure of soft black slate, 40 to 60 ft. wide, car- rying a good deal of water on the hanging wall side and some stringers of quartz, which was supposed to be the channel that carried the ore bodies on the upper levels. We drove north on the foot-wall side of this fissure 233 ft. and south 250 ft., making in all 483 ft. driven on the channel. At the end of each drift we cross-cut both east and west 12% ft. each way, which is room enough to run cross-cuts with the diamond drill. The following is a detailed statement of the cost of run- ning 1,175 ft- of drifts and cross-cuts on the 1,950- ft. level. Most of the rock was hard greenstone ; average size of tun- nel, 5 x 8 ft. : 350 ROCK EXCAVATION METHODS AND COST. 1,428 days' labor, * $3,772.50 1 68 days for day foreman at $4 672.00 134 days for night foreman at $3.25 435-5 Total labor cost for drifting and cross- cutting 1,175 ft $4,880.00 Average labor cost per ft $4-153 11,150 Ibs. of powder used, costing 1,226.50 Average cost of powder per ft '1-043 26,500 ft. of fuse used, costing 79-5 Average cost of fuse per ft 068 35 boxes of Lion caps used, costing 35- Average cost of caps per ft 03 800 Ibs. of candles used, costing 96.00 Average cost per ft. for candles 082 Total cost per ft $5-376" Total cost $6,317.00 3,258 blasting holes were drilled. Average number of holes drilled per ft., 2.77. The average amount of powder used for each blasting hole was 3.42 Ibs. of 40 per cent. Hercules. Average amount of fuse per ft., 22 ft. ; average number of caps per ft., 3; average amount of candles per ft., 0.68 Ib. Cost of the Newhouse Tunnel. In the Engineering and Mining Journal, April 19, 1902, Mr. H. Foster Bain gives the following: The Newhouse tunnel starts at Idaho Springs, Col., at an altitude of 7,543 ft. It is a 12 x 12-ft. excavation now 12,861 ft. long, and eventally will be 5 miles long. In Feb., 1902, the average progress was 9.2 ft. per day from one face, or 267.6 ft. for the month. The rock never breaks beyond the holes ; it is a granite-gneiss and schist dipping away from the face. Twenty holes, 10 ft. deep, are drilled, 8 cut holes, I plunger hole at the upper center of the cut, 3 back holes along the roof, looking up. and 4 side holes on each side looking a little out and up. Miners at $2.75 per lo-hr. day and car-men at $2.50. COST OF DRIFTING, SHAFT SINKING, STOPING. 351 Three Leyner- Water drills are used; two 3-in. sluggers on two columns drilling the side and cut holes, and one Model 5 drill mounted on a bar drilling the plunger hole and the back holes. The drill crew consists of 5 men, who work from 7 A. M. to about 5 P. M. ; they do not stop drilling at noon. At I p. M. a powder gang of 5 men comes on and attends to track laying, timbering, putting in water box, etc., until the drilling is done. They lay the permanent track, which is kept 250 ft. from the face; the temporary mucking track being run up the drilling platform. The tracks are i8-in. gage, 35-lb. rails, on 4 x 8-in. x 8-ft. ties. The water box is i x 2 ft., made of 2-in. stuff and is car- ried under the track. The powder gang tears down the drills, covers the floor with ^-in. steel plates in sections 6 ft. square for 40 ft. back of the face, and then fires the cut holes by electricity; this takes 40 mins. The cut is fired 2 to 5 times with 60 per cent, gelatin powder, 8 to 9 sticks being used for the first round. In all about 100 Ibs. are used in the cut holes. The side and back holes are fired with 40 per cent, powder, 50 to 70 Ibs. being used. The holes are not tamped, and the blasting takes 2^2 to 3^ hrs. During the blasting compressed air is delivered to the face through a 4-in. pipe, and drives the smoke back to a .iQ-in. exhaust pipe laid between the rails on top of the water box. After blasting, the gang cleans up the track ready for the muckers and loads the first train of cars. At 10 P. M. a mucking gang of 6 men goes on ; the boss picks down, and three men shovel while two rest. The cars (3 x 3^ x 5 ft.) hold 35 cu. ft., and 45 to 60 cars are filled per night. Mules have been used for tramming, but a 16- H. P. Baldwin-Westinghouse electric locomotive has ju c t been installed. In all there are 32 men employed on com- pany work, including blacksmiths. The power plant includes three 8o-H. P. boilers, of which two are in use at one time ; two 16 x i6-in. two-stage Nor- walk compressors ; one 22 x 24-in. two-stage compressor ; 352 ROCK EXCAVATION METHODS AND COST. one No. 7 Root blower driven by a 5<>H. P. Atlas engine; 3O-H. P. engine driving the 2O-kilowatt, 5OO-volt dynamo. For drilling the air is used at 160 Ibs. pressure, having been gradually worked up from no Ibs. Each of the drill crew receives $3 a day plus $i on an average for bonus. The total bonus is $6 per ft. for all over 1 60 ft. per month, or about $500, and is money well ex- pended, the men working long hours and hard rather than lose a round. The detailed cost per foot is shown by the following ab- stract from the manager's report for the year ending Aug. 31, 1900: Labor : Drill crews and foremen ................. $3-Oi Trammers, blasters and drivers ........... 4.34 Blacksmith shop ........................ 1.03 Engineers ..... ........................ 1.15 Explosives .............................. 4.55 Oil and waste ..................... . ..... 12 Coal .................................. 3.91 Mules, feeding and shoeing ............... 32 Drill repairs ............................. 82 Premiums ............................. 1.87 Tools .................................. 33 Timber ................................ 16 Track and material ...................... 1.84 Track labor and repairs ................. 2.07 Engineering and surveying ............... 22 Salaries and office expenses .............. 1.97 Miscellaneous Legal expense ..................... $0.07 Insurance ......................... 1 1 Taxes ............................ 12 Minor items ........................ 73 $28.74 COST OF DRIFTING, SHAFT SINKING, STOPING. 353 Total, $79,478 for driving 2,959^ feet or $28.80 per foot. The previous year this cost was $27.74 and the actual break- ing cost was $19.68. The increase was due to the increased cost of supplies and the greater expense of working in a larger tunnel. Cost of Sinking and Drifting at the Homestake Mine. In Mining and Scientific Press, Feb. 13 to Mar. 12, 1904, Mr. Bruce C. Yates- gives data on the methods and costs of min- ing work in the Homestake Mine, Lead, S. D. 54- Fig. 54 shows the location of drill holes in shaft sinking. The rock is a hard carbonaceous slate dipping at an angle of 60 to 90 from the horizontal, which makes blasting the cut quite difficult. When sinking is resumed in any of the shafts, a 25-H. P. engine, operated by reheated compressed air, is installed on the lowest level. Miners in the shaft usu- ally work under contract. At the Ellison shaft, which has three compartmnts, two of which are 5 x 10 ft., and the third 6 x 10 ft. in the clear, the force employed on each shift is: 4 miners (contractors), i engineman, i lander, i timberman and i carpenter working 2^ shifts framing one set of timbers which provide for 6 ft. of shaft. The actual 354 ROCK EXCAVATION METHODS AND COST. time in placing one set of timbers is 8 hrs., but the timber- men are kept busy one shift in each 24 hrs. running timber from the saw mill and putting in extra bracing. The length of a shift is 10 hrs., but, as the men are lowered twice each shift on company time, the actual working time is about 9 hrs. The cost of labor in sinking i ft. is : 4 miners, 2 shifts, at $4 $32.00 i timberman, I " " 4 4.00 i engineman, 2 ' 4 8.00 i lander, 2 " " 3 6.00 Total labor cost per ft $50.00 To this must be added the cost of timber sets (12 x 12-in. timbers), as follows: Timber for i set, 1,500 ft. B. M $26.85 Framing i set 10.00 4 miners, one shift, $4 16.00 i lander " 3 3.00 i timberman 4 4.00 i engineman 4 .< 4.00 Total cost per set $63.85 Cost per ft. of shaft, $10.64. The costs of the lining, of explosives and of power are not included in the foregoing. There are three sizes of drifts '.6x7 ft. for prospect drifts ; 7 x 8 ft. for single-track working drifts ; 12 x 8 ft. for double-track working drifts. Figs. 55 and 56 show two methods of locating holes in single track drifts ; holes are 6 ft. deep, and the advance is 5 ft. Two machines are used for drilling, preferably mounted on a horizontal bar. The bar set up is preferred to the column set up, because the machines can be set up immediately after blasting, and be- cause the sides of the drift are carried along much more COST OF DRIFTING, SHAFT SINKING, STOP ING. 355 evenly. The following shows the cost of driving 5 ft. of 7 x 8-ft. drift : i miner drilling, 2 shifts, at $3.50 $7.00 i helper " 2 " " 3.00 6.00 i miner blasting, i " " 3.50 3.50 i helper i 3.00 3.00 i shoveler 2 3.00 6.00 Explosives, 40 p. c. dyn., cap and fuse 10.75 Blacksmith, repairs of drill and mch. shop. . . 4.85 Total cost of 5 ft $41.10 Cost per ft 8.23 Cost per ton 1.47 l ^^m^m^i w t Fig. 55- Fig. 56. The above does not include track laying or putting in air pipe. There is no timbering in drifts. Dynamite costs about 12 cts. per Ib. The drills used are 3 or 3^ ins. When two drills are worked, one helper serves two drills, and the progress is nearly doubled. The cars have a capacity of 20 cu. ft. each, and hold 10 cu. ft. of solid rock, weighing i ton. Hauling is done with horses at a cost of 0.3 ct. per ton per 1,000 ft. The cost of driving a double-track 8 x 12 ft., drift, re- 356 ROCK EXCAVATION METHODS AND COST. quiring 20 holes 6 ft. deep, giving an advance of 5 ft., is as follows : i miner drilling, 3 shifts, at $3.50 $10.50 i helper 3 " " 3.00 9.00 i miner blasting, i " " 3.50 3.50 i helper " i " " 3.00 3.00 i shoveler 3 " " 3.00 9.00 Explosives, caps and fuse 16.90 Blacksmith, repairs and mch. shop 6.50 Total cost of driving 5 ft $58.40 Cost per ft 11.68 Cost per ton 1.22 Cross cuts and drifts in ore are from 1 8 to 24 ft. wide and 10 to 12 ft. high. In making a "raise," 6x6 ft., one machine driller and helper will make 100 ft. of raise in 60 shifts, provided they are not required to "car" the rock; the location of holes is similar to that in drifting. Cost of Drifting and Sloping at Cripple Creek. In The Engineering and Mining Journal, Nov. 21, 1903, Mr. J. R. Finlay gives the following data: At the larger mines of Cripple Creek the cost of mining the total product of ore and waste is from $2.50 to $3.50 per ton, which includes all the expenses of the company. The above cost includes sort- ing the ore. The ore occurs in small veins, the largest and best of which are in granite. In one of the large mines the work done during one month was as follows: 18,910 tons were mined from 40 different stopes, but including the de- velopment work (drifts, cross-cuts, etc.) 24,931 tons were mined at a cost of $2.55 per ton, and this was reduced by sorting to 7,093 tons of shipping ore, making the cost $8.96 per shipping ton. Wages average $3.40 for 8 hrs. ; coal, $4.60 per ton ; timber, $20 per M. Part of the rock is ordi- nary, unaltered granite, not excessively hard, but not soft; COST OF DRIFTING, SHAFT SINKING, STOPING. 357 and part is equally hard porphyry. The costs in detail were as follows: c/5 c ' c/r g < O M-I rj fj- en qj H 'C 'J3 ^ r o i_ Q ^ o> (^ wT N L |tf ?I oo -S g fe J o S !> Machine men and helpers and hand miners $0.34 $1.86 $2.01 $3.16 Trammers, shovelers, pipe and track men, etc 0.41 1.03 1.04 0.98 Timbermen 0.23 1.19 Total underground labor... $0.98 $2.89 $3.05 $5-33 Cost of machines, compressed air, drill sharpening, repairs, etc.. 0.15 0.97 1.05 1.66 General tramming cost, repairs on cars, oil, supplies, etc 0.03 0.07 0.09 0.06 Explosives 0.13 1.43 1.66 1.42 Lumber and timber 0.28 152 Hoisting and tramming on sur- face 0.23 0.46 0.53 0.40 General expense, bosses, assaying, surveying, office, etc 0.23 0.58 0.67 0.45 Supplies, miscellaneous 0.04 .... .... .... Total cost $2.07 $6.40 $7.05 $10.84 In Mining and Scientific Press, Feb. 13, 1904, an abstract is given of the annual report of Mr. F. M. Kurie, assistant general manager of the Portland Gold Mining Co., Cripple Creek, Col. The report gives the following tables of costs for development work and stoping for the year 1903, which is the lowest in the history of the company : Per foot. 19,808 Ft. Drifts 1,451 Ft. Raises Stoping Breaking and Crosscuts. and Winzes. per ton. Machinemen and miners. ... $1.969 $3-458 $0.369 358 ROCK EXCAVATION METHODS AND COST. Shovelers ... $0.038 $0.193 $0.218 Air and air drills. 1.049 2.02 .179 Explosives 1.444 $4.50 1.617 $7.288 i. 39 $0.905 Tramming Trammers 966 . 883 . 1 75 Pipe and track- men 124 .069 .008 * General tramming expense 098 i . 188 .103 1.055 -34 - 2I 7 Timbering Timbermen 029 1.503 .215 Lumber and tim- bers 017 .046 -947 2.45 .310 .525 Hoisting .583 .604 .254 General expense ... .70 .735 .291 Total average cost $7.017 $12.132 $2.192 In discussing the most economic methods of drifting and stoping in the Cripple Creek mines, Mr. Victor G. Hills gives the following data : Small drills are better for drift- ing, as well as stoping; they are not so fast, but take less power. A small compressor runs five 2-in. drills where formerly it ran only two 3^-in. drills. Moreover the baby drill is run by one man without a helper. A one-man, or baby drill, uses J^-in. steel for "starters" and % in. for long drills, handling a drill 8 ft. long, although holes are usually 4 or 5 ft. deep, seldom over 6 ft. The baby drill is mounted on a bar. One driller clears the way, sets up, etc., and aver- ages 39 ft. per 8-hr, shift in highly indurated andesite brec- cia (hardness, 6 to 7; sp. gr., 2.4 to 2.7). Machine men re- ceive $4, miners $3 for 8 hrs. at Cripple Creek. A man driving a 4 x 7- ft. cross-cut puts in 9 to 12 holes for a shift. Records by the month, without allowance for sickness, holidays, breakdowns, etc., show a progress 4.3 to 4.7 ft. per day of two shifts. A man frequently makes 3 ft. a day for several days. In making an upraise 4 x 8 ft. a man averages 2 ft. a day, doing his own temporary timber- COST OF DRIFTING, SHAFT SINKING, STOPING. 359 ing; regular timber men following 10 to 15 ft. behind, pro- viding a safe storing place. In sinking a shaft 8.2 x 17.1 ft., depth, 1,000 ft., with no water to pump, two baby drills sank 5 ft. every 2 days ; the machine men working only 12 hrs. in every 48 hrs., 12 hrs. being required to muck and timber; 5 muckers worked one shift to remove waste. This is an excellent record. Confirming the foregoing data relative to the economy of small one-man drills, a paper by Mr. B. L. Thane in Trans. Am. Inst. Min. Eng., 1899, may be cited. Baby drills mounted on tripods were used in stoping a quartz vein I to 3 ft. thick. A platform of lagging was laid on the muck to support the tripod. Holes should not be drilled more than 3 to 6 ft. deep to avoid sticking or binding. Upon striking a "slip" shorten the stroke, loosen bolts and let drill shift without stopping. A driller and a helper averaged 40 ft. of hole between 9 A. M. and 4:30 p. M., breaking twice as much rock as when using hand drills. In drilling shallow holes it is especially desirable to re- duce the lost time as much as possible. To save time in changing drill bits one authority recommends riveting the two nuts on the U-bolts. Cut a key seat in the upper end, and insert a wedge having a small lug. Put in this wedge with the tapering side toward the end of the chuck so that every blow of drill tends to tighten it. Two blows of a hammer will loosen the wedge so that the drill can be re- moved. Cost of Drifting and Stoping at Rossland, B, C. In a paper entitled 'The Operation of the 'Hole Contract System' in the Center Star and War Eagle Mines, Rossland, B. C.," by Carl R. Davis, E. M., read before the American Institute of Mining Engineers the following data were given : The mines in question contained a vein material that was exceedingly variable in hardness and in width of deposit, so much so that it was not practicable to measure the progress of a gang of miners by the linear foot of heading 360 ROCK EXCAVATION METHODS AND COST. or stope. An attempt was made to keep account of the progress of each gang by counting the car loads of ore sent out, but this had to be abandoned because of the imprac- ticability of keeping separate the ore broken by each gang, since the ore broken by several gangs of men was drawn off through the same loading chute in the mine. Finally Mr. Davis, having observed that the number of feet of hole drilled (by two miners) with a power drill did not vary 5 per cent, from month to month (although it varied greatly from day to day), decided to introduce a system of paying the miners according to the number of feet of hole drilled each day. The drillers worked in two 8-hour shifts, two men to a shift, the four miners thus forming a contract gang. Verbal contracts were made each month with each gang as to price per foot drilled. No charge was made for repairs to tools. A blasting crew of a few picked men worked from I A. M. to 7 A. M. while no other miners were at work, thus avoiding delays due to smoke accumulations. Under the old wage system the miners received $3.50 a day, while under the new "hole contract system" they earn $4 to $4.25 a day, and the cost of stoping out ore is about 48 cts. per ton now, as compared with 86 cts. under the old wage system! The following tables give details of cost: Comparative Cost of Stoping Ore. f System Contract Wage (49,849 tons) (13,818 tons) per ton. per ton. Drilling $0.356 Blasting 021 f $O75 Explosives .100 .115 Total per ton $0.477 $0.865 COST OF DRIFTING, SHAFT SINKING, STOPING. 361 Cost of Driving Headings. Per lin. ft. Drillin s $5-36 i $8 6 Blasting .68 f Explosives 2.75 2.78 Total per lin. ft $8.79 $11.14 Four miners in drifting and cross-cutting average per month of 30 days a progress of 97.5 lin. ft. under the contract system, as against 50.8 lin. ft. under the wage system. Twelve men (3 shifts) shaft sinking averaged per month 58 lin. ft. under the contract system, as against 27.2 lin. ft. under the wage system. It will be seen that the introduction of the contract system almost exactly doubled the efficiency of the men, whether they worked at stoping, drifting or sinking, while at the same time their daily pay was increased about 20 per cent. The figures are eloquent enough without further com- ments on the advantages of the contract system both to the miners and to the mine operators. Cost of Development and Stoping, Centre Star Mine, B. C. The following data have been abstracted from the recent reports of Mr. Edmund B. Kirby, Gen. Mgr. Centre Star Mine, Rossland, B. C. The main shaft sinking was done in 1901 ; the rest of the work was done in 1903. : Development Work. Main Small Raising. Drifting. Stop- Shaft. Shaft. ing. Total advance, feet 337 79. 186. 2,903.5 Ore stoped, tons .... 84,453. Cost Cost Cost Cost Cost per ft. per ft. per ft. per ft. per ton. 1. Drilling $12.95 $6.10 $7.31 $4-53 $0.405 2. Blasting 4.89 2.48 2.40 1.08 .03 3. Explosives 3.91 3.13 3.72 2.72 .145 4. General mine supplies. .2.35 .51 .64 .43 .04 5. Mine lighting Candles .62 .26 .19 .14 .015 6. " electric .72 .30 .22 .13 .01 362 ROCK EXCAVATION METHODS AND COST. 7. Smithing $1.09 $1.00 $1.14 $0.72 $0.065 8. Tramming and shovel- ing direct 19.66 5.51 .65 1.21 .24 9. Tramming and shovel- ingapportioned ..1.54 .64 .35 .42 .085 10. Timbering labor 9.60 1.81 3.08 .02 .19 11. material ... 3.16 .33 .57 .01 .11 12. Machine drill fittings and repairs 1.15 .86 .94 .60 .055 13. General mine labor.... 7.81 1.57 1.18 .84 .09 14. Hoisting underground. 14.28 4-79 .... 15. main shaft.. 2.19 1.48 .89 .94 .19 16. Compressed air 2.03 1.74 2.08 1.07 .12 17. Mine ventilation 2.29 .23 .17 .13 .015 18. Pumping 1.71 1.09 .34 , .035 19. Assaying 01 .55 .47 .14 .03 20. Surveying 59 .20 .17 .11 .01 21. General expense 9.41 3.57 2.71 1.51 .185 Total $99.16 $38.77 $29.97 $T7-09 $2.065 The raises and drifts are evidently large in size. The scale of wages is : Shift boss $5.00 Machinists $4.00 Shaft men 4.00 Blacksmiths 4.00 Machine men 3.50 Blacksmiths' helpers 3.00 Timber men $3.00 to 3.50 Hoisting engineers, $3.00 to 4.00 Shovellers and car men.. 2.50 Powder and tool boys.... 2.50 Carpenters 3.50 Surface laborers 2.50 The surface men work ten-hour shifts, except carpenters, who work nine. On May ist, 1899, the Provincial Eight- Hour Law went into effect ; its effect is to limit underground work to eight hours. At first, at the War Eagle Mine, this was applied by putting on three shifts in 24 hours, which reduced the actual working time of the men to 7^ hours, as half an hour was allowed for lunch. This was a wasteful arrangement, as in spite of the blowers for forcing out the smoke after blasting, such huge charges as were used to break the rock sometimes rendered a stope unapproachable for several hours. An air drill was necessarily often idle also, to permit the machine men to load, blast and then clear the muck away sufficiently to set up again. COST OF DRIFTING, SHAFT SINKING, STOPING. 363 In the spring of 1900 the three-shift system was aban- doned in favor of the two-shift, arranged thus: The first shift started at 7 A. M. and worked, with an hours' intermis- sion, till 4 P. M. ; the second shift started at 4 P. M. and, with an hour for supper at 6 P. M., finished at I A. M. From i A. M. to 7 A. M. a special blasting gang loaded and fired all the ground drilled for breaking. By this method the work- ing faces were freed from smoke before the machine men started work at 7 A. M. Cost of Shaft Sinking at the Pioneer Mines. At a recent meeting of the Lake Superior Mining Institute, Mr. Frank Drake read a paper, giving in detail the cost of lining a shaft with steel as compared with a timber lining. With steel at 2 cts. per lb., the cost of lining a three-compartment shaft with steel, was: Per ft. of shaft. Steel in sets $4.50 Labor, drilling and riveting $1.29 Iron bearers, chairs and hangers 0.64 Wood lagging 2.12 Total $8.55 With timber costing $14 per M, the estimated cost of lin- ing the same shaft was : Per ft. of shaft. 155 ft. B. M., at $14 $2.17 Iron and bolts 43 Labor framing sets 32 150 ft. B. M. 2-in. lagging, at $14 2.10 Labor, cutting lagging 27 Bearers and hangers 28 Total $5.57 Mr. Drake gives the cost of shaft sinking in two shafts sunk at the same time in the same material, "Ely green- stone," but, unfortunately, one shaft was sunk by day labor, while the other was sunk by contract, which makes compari- 364 ROCK EXCAVATION METHODS AND COST. son of little value. It will be seen that "B" shaft required about 23 per cent, less excavation than No. 2 shaft, due en- tirely to the saving in space effected by using steel. C U 3 f 4- OlictlL "B." -No. 2 . Pioneer Mine. Savoy Mine. Dip 70 83^ Material of sets Steel Wood Material of lagging Part wire rope Wood and part wood Size of Timbers of sets 10 x 12 ins. Compartments (2)6 x 6 ft. and (2)6 x 6 ft. and (1)5x6 ft. (1)42-3x6 ft. Outside shaft dimensions 6 l /t x 18 ft. 7 2-3 x 20 ft. Outside area 117 sq. ft. 153 sq. ft. Rock excavated per ft. of shaft 4 1-3 cu. yd. 5 2-3 cu. yd. Progress per working day 1.43 ft. 1.54 ft. Items of Cost per Foot "B" shaft No. 2 shaft (steel). (wood). 1. Contract price of excavation $15-95 2. Company labor account of excavation... 5-74 $22.60 3. Labor account of lining 2.03 1.45 4. Shop and team labor 1.74 2.03 5. Explosives 1.86 1.98 Timber and lath for sets 5-26 Mining timber 1.87 -63 Iron and steel 1.52 1.15 Steel rail 4-70 i.io Wire rope for lining 37 Total, influenced by kind of lining $35-78 Other items not influenced by kind of lining : 6. Miscellaneous labor regularly employed* $10.71 Pipe and fittings 1.17 Miscellaneous supplies 4.68 Fuel 4-30 Air 2.89 Temporary surface buildings and head frame . 28 7- 8. 9- 10. ii. 58 Grand total $59-8o $52.92 * Engineers, firemen, landers, etc. N. B. Fuel and air items were roughly estimated, and are subject to muc uncertainty. COST OF DRIFTING, SHAFT SINKING, STOPING. 365 Here we have a comparison of cost very favorable to the steel-lined shaft, but it must constantly be borne in mind that the steel-lined shaft was sunk by contract labor and the wood-lined shaft by company labor. The "B" shaft of the Pioneer Mine, Ely, Minn., is 862 ft. deep, and dips at an angle of 70. The explosive used in both shafts was 40 per cent, dynamite at 10^ cts. per Ib. Coal cost $4 a ton. Ma- chine men received $2.20 and helpers, $2.00 a day. Cost of Two Three-Compartment Shafts. I am indebted to Mr. Robert A. Kenzie for the following data on the cost of a three-compartment, vertical shaft, at the Helena-Frisco Mine, Frisco, Idaho: COST PER FT. OF SHAFT. Labor. Supplies. Sinking $28.69 Timbering $4.64 Timbering 5.20 Wedges 33 Shaft bearers 24 Guides 08 Hoisting 71 Powder 2.82 Pumping 44 Fuse 66 Compressor engrs 24 Caps 06 Firing .41 Fuel 4.92 Station tending 03 Lights 65 Tool sharpening 1.13 Tools 56 Blacksmithing 46 Hanging irons 58 General expense 55 Pump fittings 42 . Drill fittings 46 Total for labor $43.10 Lubricants 26 Total for supplies. .. .$16.42 This shaft was sunk from the 6oo-ft. level to the 1, 600- ft. level, 1,000 ft., in 516 days, at a cost of $59.52 per ft. for labor, materials and supplies. The 200 ft. between the 600 ft. and the 800 ft. level, were sunk in 81 days, at a cost of $49.68 per ft. for labor, and $16.71 for supplies. Unfortu- nately at the time of going to press I have not received the rate of wages and prices paid. In the School of Mines Quarterly, 1904, Mr. R. A. Parker gives the following data on the sinking of a shaft at the Hamilton-Ludington Mine, Iron Mountain, Mich. The 366 ROCK EXCAVATION METHODS AND COST. shaft is 7 x 21 J4 ft. in the clear; 9^ x 24 ft. being the aver- age area excavated, and is 1,400 ft. deep in a uniform dolo- mite that drills and breaks readily. Two shifts were worked requiring a total of 37 men, including surface men. The best month's progress was 90 ft. The center cut holes were 9 ft. deep; the second set, 3 ft. back, 8 ft. deep and more nearly vertical; the third set, 3 ft. back of the second, 7 ft. deep, and the remaining holes squared up. The total number of holes was 32. The advance at each blast was 5 ft., 200 Ibs. of 45 per cent, dynamite being used in a blast, the cut holes charged one-third heavier than the others. Cost of Mining, Douglas Island, Alaska. For the follow- ing data I am indebted to Mr. Robert A. Kinzie, Asst. Supt. Treadwell Mines, and to an excellent paper by him in the Trans. Am. Inst. Min. Eng., 1903. The ore is a mineralized syenite having a specific gravity of 2.61 at the Ready Bullion Mine, 2.64 at the Mexican Mine, and 2.67 at the Treadwell and 7oo-Foot Mines. The country rock is a slate. No timbering is used in the stopes, where the ore is shot down in large, thin slabs, so that the fall will break it as much as possible. In stoping, the drill holes average 8 ft. deep; a (3^ to 3^-in.) drill averaging 28.7 ft. of hole per lo-hr. shift, breaking down 35 tons of ore with a consumption of 12^ Ibs. of 40 per cent, dynamite. The cost of breaking the ore after it has been blasted is a large item of expense, as one man takes one day to sledge and bulldoze 35 tons of ore, using 0.85 Ib. of 70 per cent, dynamite for bulldozing each ton of rock. A stope is usually 7 ft. high, 150 to 300 ft. long, and of variable width ; the floor of a stope slopes from the parallel lines of chutes at an angle of 30 . Drifts and cross-cuts are usually 7 x 10 ft. in the clear, and raises are 6 x 8 ft. in the clear, no timber being used. The rock has no seams or slips to break to, making it difficult to break to the bottom of holes. In drifting, 6 cut holes, 6 ft. deep, converging toward a point, are drilled ; 4 relievers. - COST OF DRIFTING, SHAFT SINKING, STOPING. 367 5 ft. deep, are next drilled with a slight rake toward the center; finally, 12 trimmers, 5 ft. deep, are drilled around the floor, sides, and top of the drift. The cut holes are blasted with 70 per cent, dynamite ; the rest with 40 per cent. The price of the 40 per cent, powder is about 14% cts. per Ib. At each level a station is cut the width of the shaft, 50 ft. long, and 8 ft. high ; beneath the floor of each station an ore bin is cut out so as to give a storage capacity of 500 to 1,500 tons of ore. The ore is trammed from bins at the bottom of stopes to the storage bins at the shaft, drawn off into skips and hoisted to the surface. Tramming is done by hand, by horses and by the tail rope system. About 58 per cent, of the total ore excavated is taken from open pits, the largest of which has now reached a depth of 450 ft., and has a maximum length of 1,700 ft. and a width of 420 ft. When a pit is opened, a raise is put up from the nearest level to the surface, and all the ore ex- cavated in the pit is shot down this raise into a chute from which it is trammed to a bin at the shaft, and hoisted in skips. The spacing of the holes in this pit work is given on page 216. The duty of drills and of explosives in the different class of work is as follows : Per drill pei lo-hr. shift. ^ B g B $Z Ft. of drill Tons of ore o3 A ? Open Pits Stopes . . , hole .... 37.4 ^o.o broken 69.7 35-7 11.7 94 fa a 0-54 345 2.00 0.23 1.40 1.50 1.40 Drifts ... .... 36.8 Raises ... . ^2.4 Shaftsf . . . , 32.8 * This includes only the dynamite used in drill holes, and does not include dynamite used in bull-dozing, "t Three of the shafts are three-compartment, and one is four-compartment. 368 ROCK EXCAVATION METHODS AND COST. The cost operating each drill per lo-hr. shift is as follows: Labor $7.58 Drill sharpening, repairs, power, etc 2.42 Total $9.00 The cost of power is low, for about 80 per cent, of the year water power is used to run to the compressors. On the other hand wages are fairly high, being as follows per ic-hr. shift: Machine drillers, $2.50 to $3 with board and lodging, helpers, $2.25 " . " Mine laborers, $2.00 Blacksmiths, $4.00 Tool-sharpeners $3.50 The Treadwell group of mines is justly celebrated for the fact that gold ore having a value of less than $2 a ton is mined and milled at a profit. The following table gives the itemized cost of mining a ton of ore at each of three mines, the output being that of 12 months, 1901-2. The low cost of the Treadwell mine is due not only to the fact that larger quantities of ore were handled, but to the fact that most of the pit mined ore was taken from the Tread- well. In considering the following data, it should be re- membered that the ore deposit is massive, that there is no timbering, and very little pumping. The cost, low as it is, could have been still further reduced had crushers been in- stalled capable of receiving rocks 18 x 36 ins. in size, thus reducing the cost of bulldozing. COST OF ORE PER TON. . . C c en ' cfl O C G C ;- O O P ~ $ rt in M 10 CM W 01 m >> Tool sharpening, labor $0.0191 $0.0322 $0.0400 " supplies 0048 .0057 .0107 COST OF DRIFTING, SHAFT SINKING, STOPING. 369 Machine drilling, labor $0.2280 $0.2720 $0.2521 " merchandise 0050 .0058 .0015 " steel 0192 .0209 .0159 Compressed air, labor 0032 .0031 .0029 " steam 0293 .0572 .0882 " supplies 0082 . 0245 . 0064 Explosives, fuse 0030 . 0028 . 0027 caps 0018 .0012 .0012 70% dynamite 0079 .0175 .0154 40% dynamite 0656 .0822 .0709 labor on primers 0042 .0056 .0063 Rock breaking, labor 1643 .2137 .1439 supplies 0037 .0037 .0041 fuse 0070 .0067 .0064 caps 0042 .0029 . 0029 70% dynamite 1233 .0916 .0874 labor on powder 0099 .0132 .0148 Tramming, labor 0262 .0185 .0325 horses 0042 . 0023 supplies 0055 .0066 .0005 Hoisting, labor 0170 0.448 .0194 supplies 0023 .0014 .0048 steam power 0293 .0572 .0882 Illuminants 0085 .0149 .0104 Supplies, iron and foundry 0201 .0350 .0578 Repairs 0080 .0102 .0057 Assaying 0015 .0027 .0024 Personal 0039 General . 0017 .0029 Total $0.8399 $1-0590 $0.9954 INDEX. PAGE Abel block 138 Absorbent 114 Adit 341 (See also Drift; Tunnel) Air: Flow in pipes 63, 64, 65 Table of H. P. to compress.. 50 Merits of compressed 68 Work of compressing 49 Compressor, cost 87, 88 Gasoline ; o Tests 59, 69 Air Drill. /See Drill.) Hoist 243 Asbestos 60 "Baby drill" (see Drill, baby) Backs 5 Bank blasting 158 Battery, electric 133 Belt conveyor 310 Bench 214, 297 Bent 297 Bit. (See Drill-bit.) Black powder. (See Powder.) Blacksmithing. (See Drill bit-sharp- ening.) Blasting 1 24, 141 Bank 158 Boulders. (See Boulders.) Close to Buildings 192 Gravel 157 Hardpan 157, 239 Ice 162 In seams' 206 Knox system 197, 199, 210 Piles 160 Stumps . . 160 Subaqueous 278 With powder and dynamite to- gether 169 With water cushion 204 Blasting- gelatiin f2i Blasting-mat 269 PAGE Blasts, large chamber 150 Block-holing 162 Block quarry 187 Boiler, efficiency 65 Borts 95 Boulders, blasting ..162, 233, 235, 366 Dredging 295 Sledging 232 Breast 34i Brick tunnel lining 338, 340 Broaching 192 Broken stone, voids 9 Loading 165 (See also Loading.) Buffalo breakwater 198 Bucket, clamshell 166 Bull-dozing. (See Mud-capping.) Bull-points ^68 Bullying. (See Drill-hole, spring- ing.) Cableways 153, 164, 244, 248, 273 Canal, Chicago aj8 Cantilever crane 250, 255, 257 Caps 128, 136, 137 Carbons 95 Cars, hauling in 165, 171, 182, 226, 241, 244, 355 Car-hoists 258 Carts, hauling in 177, 180, 226 Cat holes 35 Center-cut 297 Chamber blasts 150 Chambering. (See Drill-hole sprftig- ing.) Channeling 105, 193, 261 to 264 Charging explosives ...124, 269, 286 Chicago canal 238 Churn-drill. (See Drilling, hand.) Chuck 31 Chuck tending 17, 37 Clamshell bucket 166 Clay excavation 239 Coal. (See Fuel.) 372 INDEX. PAGE Column for drill 40 Compressed air. (See Air.) Concrete. (See Tunnel lining.) Drilling 44 Contractors powder 122 Conveyor belt 310 Crane. (See Cantilever crane; Locomotive crane.) Crater theory 142 Crimper 1 28 Cross-cutting. .341, 349, 356 to .558 Crushed stone. (See Broken stone; see Crushing.) Crushing 217, 220 Cut-holes 297, 301 Cutters 5 Depreciation 86 Derby bit 290 Derrick 166, 180, 196, 206 Double boom 254 Hullett-McMyler 252 Derrick-car 231, 236 Derrick-scow 279, 283, 284 Detonators 132, 139 Development work 241 Devil -236 Diamond drilling 95 to 97 Dimension stone 184 "Dinkey" locomotive 174 Dip 5, 185 "Dolly" 29 "Dope" in Dredging 278, 281, 286, 287, 290, 292, 204 Dressing. (See Trimming.) Drifting. ... 139, 152, 158, 289, 341, 349, 354, 357, 358, 361, 366, 367 Drill, air required ....51, 55, 56, 57 "Baby" 191, 222, 223, 358, 359 Bar mounting 40, 354 Brandt rotary -. . .45, 333 Care of 37 Coal consumption. (See Fuel.) PACK Column 40 Depreciation 86 Diamond 95 to g~ Electric 46, 93 Gasoline 46 Hand 13 Handling a 34 H. P 56 Leyner 45, 55, 83, 351 Mechanism 31 Price of 34, 86 Repairs 86, 221, 223, 311, 344, 362 Rand 53, 54 Sizes of 32, 56 Steam consumption 58, 67 Table of data 34 Tests 52, 78 Well 90, 215 (See also Drill-bit; Drill-holes; and Drilling.) Drill-bit, Brunton 26 Derby 290 Fitch 26 Hand drills 15, 17, 23 to 25 Sharpening, 26 to 30, 85, 201, 209, 211, 213, 219, 223, 274, 285, 286, 311, 314, 322, 329, 334, 362, 365, 368 Tubular 290 Wear of 24, 329, 347 Drill-holes, cost of charging. . . . 220 Depth of economic 215 Size of 15, 23 Spacing, 144, 146, 215, 216, 250, 286 Springing 147, 216, 268, 302 Drill-platform 288, 293, 296 Drill-scow 278, 285, 29'2, 294 Drilling, churn. (See Drilling, hand.) Contest 52, 78 Contract system 360 Cost of hand. (See Drilling, hand work * INDEX. 373 PAGE Cost of machine. .21, 72, 92, 94 213, 219, 222, 223, 247, 248, 261, 265, 270, 275, 368 Effect of air pressure, 52, 55, 83, 352 Direction of hole... 15, 16, 347 Shallow holes 81, 223 Size of hole 54, 342 Sludge 16 Footage, 52, 79, 84, 193, 202, 223, 300, 319, 321, 331, 334, 345, 366, 367 Hand work, 15 to 22, (&^) 272, 313, 316, 332 Plug-holes, 20, 45, 163, 187, 189 Rates in different rocks 82 Rule for estimating footage.. 79 Drilling, subaqueous, 281, 285, 287, 288, 292, 294, 295 Table of average time 77 feet per cubic yard, 217, 237 Time to change bits 73, 359 Shift drills 75 Use of water in, 16, 38, 42, 55, 83, 291, 347 (See also Drill.) Dump car. (See Car.) Dynamite 106, no, in, 114 Accidents n 7 Charging 124, 127 Effect on stone 124 Fumes 130 Grade to use 125, 365 Leaking 118 Testing 121, 138 Thawing 116, 118 Weight 115 Earth excavation 157, 228, 239 Electric battery 131, 133 Detonator. (See Detonator.) Drilling 46, 93 Engine. (See Steam Engine.) Excavation, Chicago canal 261 PAGE Classification 226 Clay 239, 306 Earth 228 Gneiss 222 Hardpan 157, 239 Loose rock 228 Open-cut, 16, 214, 261, 275, 338 Sandstone 223, 225 Shale 224 Subaqueous 131, 277 Table of drilling and explos- sives 237 Expansion tamping 127 Exploders. (See Caps, Detonators.) Explosives 106, 237 Kind to use 124 (See Dynamite, Joveite, Judson, Powder, etc.) Feathers. (See Plug and Feathers.) Feed-screw 32 Fire clay 306 Firing 131, 136 (See Blasting.) Fitch bit 26 Flatter 29 Forceite 113 Free-air 49 Fuel, 65, 67, 70, 89, 90, 92, 209, 221, 223, 322, 323, 349 Fuse 136 Fuse-cutter 129 Gadder 192 Gas. (See Ventilation; see Explo- sives.) Gasoline drill 46 Gelatin 121 Giant powder 112 Go-devil 310, 316, 324 Grain 185 Granite 7, 204, 207 Gravel, blasting 157 Hardpan, blasting 157, 239 Hauling. (See Cars, Carts, Wagons.) 374 INDEX. PAGE "Head" 185 Heading 297 Heat energy 47 Hoist 243, 258, 285 Hole. (See Drill-hole.) Horse-power 47, 48, 66 Hydraulic hoist 285 Ice blasting 162 Igneous rocks 4 Inclines 241 to 244, 341 Insulating tape 132 Interest and depreciation 86 Iron ore mining 168, 173, 221 Joints in rock 4, 184, 186 Joveite 106, 122, 131, 135, 218 Judson powder. ... 106, 122, 124, 131 Jumbo 324 Knox holes 197, 199, 210 Lagging 297 Level 341 Lewis hole 205 Lift 214 Limestone 6 Line of least resistance 142 Lining. (See Tunnel lining.) Lizard ^35 Loading rock, by drag scraper 325 By hand, 164, 220, 254, 255, 257, 262, 321, 322 By steam shovel. (See Steam Shovel.) Locomotives 1 74 Locomotive-crane 250, 253 Machine drills. (See Drill.) Masonry, 186, 203, 211, 212, 317, 329 (See also Tunnel lining.) Mat 269 Measuring rock 1 1 Metamorphic rock 4 Minerals, rock-forming i Mining, pit 217, 221, 367 (See Stoping.) Misfires I34) 200 PAGE Muck 298 Mucker 326 Mud 26 Mud-capping 162, 233, 235, 366 Neat lines 12, 267 Nipper 300 Nitroglycerin no One-man drill. (See Drill, "Baby.") Open-cut. (See Excavation.) Over burden 214 Packing 305 Pile blasting 160 Pipe. (See Air; Steam Pipe.) Plank road 180 Plant rental 86 Steam and air 47 Plug and feathers 20, 187 Plug-drills 45, 163, 189 Pneumatic plug-drill. (See Plug- drill.) Porphyry 7 Pound-degree 48 Powder 106, ic8, 109 Charging 124, 269, 286 Weight 109 Primer 128 Quarry bar 191 Quarrying 16, 184, 339 Boulder 208 Gneiss 210 Granite 204, 207 Limestone 212, 220 Sandstone 203, 211 Trap 218, 219 (See Excavation.) Rackarock 289 Railway tunnel. (See Tunnel.) Raising 341, 357, 358, 361, 367 Rapid transit subway 273 Re-heater 195 RentaJ, plant 86 Rift 184 Rigger 246 INDEX. 375 PAGE Rip-rap 12 Road, plank 180 Rock coefficient 144 Denned 226 Drill. (See Drill.) Species 3 Safety fuse 136 Sandstone 6, 203, 2 1 1 Scaffold car. (See "Go-devil.") Scale-pan. (See Skip.) Scows, measuring in 199 Sedimentary rock 3 Shaft sinking, 156, 318, 341, 342, 343, 347, 353, 359, 361, 363, 365, '567 Shaking. (See Drill-holes, spring- ing.) Shale 6, 224, 310, 313 Sharpening. (See Drill-bit, sharpen- ing.) Sheet quarry 187 Shoveling. (See Loading Rock; Steam Shovel,) Sinking. (See Shaft Sinking.) Skid road 181 Skip 164, 246, 252 Sled. (See Stone boat.) Sledging 220, 223, 233 Slides 12, 230 Sludge 17, 38 Snatch team iKo Specific gravity 8, 10 Soda powder. (See Powder.) Spoon J7 Spreader 29 Springing drill-holes. (See Drill-holes, springing.) Steam Boiler, efficiency 65 Steam Drill. (See Drill.) Steam Engine, efficiency 48 Steam pipe, area of 62 Covering 61, 326 Efficiency 60 Steam, table 50 PAGE Steam shovel, fuel for 174 Tunnel work 300, 306 Work, 1 68, 216, 224, 236, 239, 240, 242, 266 Steel trackway 180 Weight of 19 Stone-boats 180, 235, 308 Stone cutting, cost 339 Dimension 184 Racks 178 Trucks 180 Sloping, 341, 346, 356, 357, 360, 361, 366, 367 Strike 5 Stripping 214 Stump blasting 160 Subaqueous excavation 131, 277 Subway, N. Y 273 Swage ~9 Tamping 108, 126, 130 Cushion 135 Expansion 127 Water U* Tape U2 Thawing dynamite 1 16, 118 Timbering 305, 3*3, 3*6, 326 Tipple 243 Ton ii Track channeler. (See Channeling.) Track, layout 182 Trackway, steel 180 Traction engine 180, 328 Trap 8, 218, 219 Trenching 206, 230, 267, 270 Trimming slopes 228 Tunnel, American 297 Blasting in 132 Busk 327 Carr's 338 Cascade 307, 323 Croton 318 Gallitzin 299 Glasgow 21 376 INDEX. PAGE Hogsback mine 345 Hoosac 21, 23, 297 Kellogg 325 Melones mine 343 Mount Wood 3 1 3 Mullan 339 Musconetcong 329 Nesquehoning 21 New Croton 318 Newhouse 350 Peekskill 336 Pryor Gap 326 Simplon 298, 332 Stampede 307 Sutro 328 Tequixqueac 331 Top Mill 313 Wabash 302 (See also Drifting.) PAGE Tunnels, lining, 297, 305, 310, 317, 324, 328, 337, 338, 340 Steel centers for lining 333 Use of traction engine in 328 Ventilating, 299, 326, 328, 331, 336, 343. 3Si, 352 Twin-headings 303 U-bolt 31 Upraise. (See Raising.) Ventilation. (See Tunnels, ventiiat- ing.) Voids 8, 9 Wagons, hauling in 177, 179 Wall-plates 300, 302 Water telescope 199 Weight of rock 8, 10 Well-drillers, cost by 90, 215 Wheelbarrows, cost by 176 Wiper 126 ADVERTISEMENTS. INGERSOLL=SERGEANT ROCK DRILLS AND ADR COMPRESSORS For every condition of {Tunneling Excavating Coal Cutters Pneumatic Tools iJNGERSOLL-SERGEANI DRILL CO, 26 Cortlandt Street Cleveland, O. Boston. Mas*. Chicago, 111. NEW YORK Philadelphia, Pa. St. Louis, Mo. Pittsburg. Pa. ADVERTISEMENTS. COM- PRESSORS 'ROCK DRILLS RAND DRILLS " Drilled good round hole. No stop from drill stick- ing." ' Most satisfactory runs. Rotation pood. Holes per- fectly round. No stops from drills sticking and no hitch of any kind." "Thoroughly good run. No stop." ''Machine taken direct from box and put on bar. Rather stiff at starting. Rotation good and hole round." OTHER MAKES " Stroke very erratic. The machine occasionally mak- ing a stroke without strik- ing a blow." "Rotation bad and hole rifled. Considerable lessen- ing of speed of machine." " Stoppage due to mechan- ical defects. Backhead loose; bolts bent when tightening up. Machine was not tried below 60 Ibs." Which do you want ? RAND DRILL (Q. EXTRACT FROM REPORT OF TEST of Rock Drills Recently Held at City & Suburban Q. M. Co. m Johannesburg, South Africa EXTRACTS FROM REPORT 128 BROADWSY ADVERTISEMENTS. iii THE "PIERCE" CORE DRILLS Are the Best and Cheapest for Making: Test Borings in Earth or Hardest Rock MANUFACTURED EXCLUSIVELY BY PIERCE WELL ENGINEERING & SUPPLY CO, J36 Liberty Street, New York, U. S. A, Cable Address, 'Phone, "Artesianos," New York. 4662 Conlandt CHARLES D. PIERCE. Manager Member of The American Society of Mechanical Engineers CONSULTING ENGINEER AD VICE ON ALL QUESTIONS or ARTESIAN WEH.L.S, WATER SUPPLY. TEST BORINGS, PLANS, SPECIFICATIONS AND REPORTS Manufacturers of Everything required to Drill and Complete ARTESIAN OIL AND GAS WELLS The "Pierce" Core Drills take out Solid Dry Cores in Earth or Rock as good as Diamond Drills and at one- tenth the Cost. USED FOB Rock Drilling, Quarrying, Blast Roles, Mining, Shaft Sinking. Machine in Operation, Driving Pipe. These are Combined Earth Boring and Rock Drilling Machines; are operated by two men ; can make a Test Boring in Earth 40 feet deep in one or two hours, or 100 feet in four to sis hours. These Hand Power Machines have a capacity of 100 to 300 feet, or mor*\ Miners use them in placer mining, making bor- ings for gold, silver and other minerals, in sand and gravel formations ; also in the beds of rivers. Extensively used by the U. S. Gk>v't Engineers in the Depart- ment of Geological Survey; at Military Posts in the Dr.itod States, Puerto Rico, U. S. Naval Coal rotations in Liberia, Africa, the U. S. Arsenal at Cavite, Philip, pines. 24 were used by the Nicaragua Canal Commission in making 20OO Test Borings for the Nicaragua Canal. Thpy are now being used by the Isthmian Canal Commission. Also extensively used by the Cuban, Canadian, British and other Governments. Extensively used by engineers and contractors for the construction of Tubular Wells furnishing 500 1O.OOO to 5,000,000 gallons of water per day, for cities, towns and for irrigation. The " Pierce" Core Drills, Test Boring: and Mineral Prospect- ing Machines, can be set up ready for work in 15 minutes ; can be taken apart and carried on pack animals or shoulders of men, the heaviest parts weighing not over 65 pounds. Send for Catalogue, 200 illustrations, stating fully what is desired. iv ADVERTISEMENTS. Mailed free with others on Elevating Convening Ipowcr transmit* ting Screening Cruebfng Coal TKHa0b= ing Mauling /fining fl&acbfnen? Catalogue 67 A is devoied to Conveyors. THE SIMPLICITY OF CONSTRUCTION OF IRocfc IDrUls INSUEES GREATEST DURABILITY LOWEST COST OF MAINTENANCE Drill Catalogue No. 76 THE JEFFREY MFG. CO. PITTSBURG COLUMBUS, O., U. S. A. NEW YORK DENVER CHICAGO CHARLESTON, W. VA. ADVERTISEMENTS. IRobtns Belt Convenors HAVE BEEN USED FOR OVER IO YEARS IN HANDLING ROCK AND ORE THEY ARE THE FIRST AND BEST The life of a belt is from 4 to 8 vears according to the service. Many of our belts have handled over one million tons of rock before wearing out. ROBINS CONVEYING BELT CO. PARK ROW BUILDING, NEW YORK vi ADVERTISEMENTS. RIDGWAY TWO-BELT CONVEYORS OUTCLASS ANYTHING ON THE MARKET INVESTIGATE Ridgway Belt Conveyor Co 29 Broadway, New York, U. S. A. Contractor's plant fto %et Two Marion Style A Steam Shovels Standard R.R* gauge \y^. cubic yards dippers Rebuilt and improved since last used and are in perfect condition. Experienced crews ready to go with shovels if desired. Also Hoisting Engines, Horse Power Derricks, Pile Drivers, Steam Pumps, Steam Drills, Stone Crusher, Brick Roller, Four-wheeled, Two-horse \ 3 /i cubic yards Dump Carts, Watson Wagons, Street Sprinklers, Wheeled Scrapers, Erie Canal Scows and other plant Any part of this plant -when not in use is in the market to let at very reasonable terms. At present all of it is ready for immediate shipment. TROY PUBLIC WORKS COMPANY R. W. SHERMAN, President, Utica, N. Y. ADVERTISEMENTS. vii ESTA BUSHED I6S7 A.LESCHEN 5 SONS ROPE GO, 92O-93S N. FIRST ST.; ST. LOU IS, MO. BRANCH OFFICES^ NEW YORK" CHICAGO" DENVER WIRE ROPE MINES, QUARRIES, ELEVATORS/ \HAULAGE OUTFITS. viii ADVERTISEMENTS. LIDGERWOOD HOISTING ENGINES OVER 23,000 IN USE Standard Lidgerwood Hoisting Engine. STEAM AND ELECTRIC HOISTS CABLEWAYS Hoisting and Conveying Devices ESPECIALLY ADAPTED FOR ROCK EXCAVATION, MINING, QUARRYING, ETC. SEND FOB LATEST CATALOGUE LIDGERWOOD MFG. CO, 96 Liberty Street, NEW YORK ADVERTISEMENTS. ix ftbe Engineering IRecorb The Leading Publication Devoted to General Engineering A Necessity to all Active Engineers and Contractors. Devotes Especial Attention to all Phases of Building- and Contracting. The Weekly CONTRACTING NEWS published by this paper is the most thorough and best verified in existence. ONLY THREE DOLLARS PER ANNUM SAMPLE COPY FREE THE ENGINEERING RECORD JJ4 LIBERTY STREET, NEW YORK x ADVERTISEMENTS. M. L. WYATT & COMPANY SALISBURY, N. C. Granite, Limestone, Marble GRANITE MILLSTONES A SPECIALTY MINING AND TIMBER LAND BOUGHT AND SOLD CALIFORNIA CAP COMPANY 4J8 CALIFORNIA STREET, SAN FRANCISCO MANUFACTURERS OF ^Detonators, Blastino Caps anb Electrical The CALIFORNIA CAP is universally recognized to be the most efficient and most reliable, as well as the safest. All powder companies recommend it. If your dealer does not carry it, communicate with us. Do not be induced to try another brand ; no other can compare with it. xi ADVERTISEMENTS. 2)nllin0 flfoacbines For MAKING LARGE AND DEEP BLAST HOLES. Pulverizing Material ahead of Steam Shovels in heavy Railroad Cuts, Street Grading, Canals, Etc. EXPLORING SUBWAYS AND TUNNELS. Drilling and Casing Air Holes, and Pumping Shafts for Mines and Tunnels. Making Soundings for Bridge Piers, and Under- Rivar Tunnels. Usable on Flatboats Making Holes for Hy- draulic Elevators, Etc. Machines are moved from hole to hole by their own p>wer without taking down the mast. By their use the powder is bunched at the bottom of the excavation. SEND FOR OUR SPECIAL CIRCULAR. We cover the whole field. Catalog No. 1 describes Water- Well Machines. Catalog No. 2, Mineral and Placer io'd Prospectors. Catalog N-. 3, Portable Oil-Well RitJS. Ea--h catalog contains a valuable rti-cussion of the line of work to which it relates, and the best methods of doing it. Catalog* free. The Keystone Driller Co., Beaver Falls, Pa., U. S. A. 3>allett Plug 3) rills The prominent features of our latest type are: Moderate first cost Economy in use of air. Least possible recoil or vibration and the rendering of repairs inexpensive when necessary. The barrel of this drill is provided with an inner removable lining, so that when after long service they becom^ worn, this lining can be removed and a new one pressed in a r . H slight expense, practically renewing the tool and prolonging its life indefinitely. THOS. H. DALLETT CO. York St. and Sedgely A ve., Philadelphia, P?. Chicago, Cleveland, Cincinnati, San Francisco, Boston, Pittsburg, Barre, Vt. xii ADVERTISEMENTS. THE Economy Blast Mole %oaber 704 feet of drilling: ; $37.00 in Powder is the saving we made in a single shot by the use of the " Economy." This Loader saves Dollars in Powder, Time and Worry. Write to-day for our Booklet, "The Economy Blast Loading System." COPE & CORNELIUS ORRVILLE, OHIO ADVERTISEMENTS. xiii BLAST HOLE DRILLS Cyclone Drilling Machines Built and Equipped with special outfit of tools to meet every requirement of the Contractor. To drill blast holes in any and all formations with safety, at the minimum of cost and the maximum of speed. The First Practical Drill for drilling- 3-inch holes. SEND FOR OUR CONTRACTORS' CATALOGUE The Cyclone Drilling Machine Co< ORRVILLE, OHIO xiv ADVERTISEMENTS. THE LARGEST MANUFACTURERS OF Explosives IN THE WORLD Dynamite Fumeless Gelatine Black Powder (For Blasting) WRITE FOB CATALOGUE ON EXPLOSIVES E L DUPONT COMPANY WILMINGTON, DELAWARE The Watt Mining Car Wheel Co. BARNESVILLE, OHIO flIMne ant> re Cars of Ever? Inscription SPECIAL CARS FOR ROCK WORK ' WRITE US FOR ESTIMATES A D VER TI SEMEN TS. xv JOVEITE FEATURES: 1. Strongf as dynamite grade for grade. 2. Comes in sticks ; is loaded and fired like dynamite. 3. Is a dry, free-running- powder, and does not freeze. 4. In six years of use not an accident has oc- cured to a user. 5. Neither heat nor cold affects it; equally good in the torrid, the frigid or the temperate zone. The Explosives Mfg, Co, 320 BROADWAY, NEW YORK xvi ADVERTISEMENTS. JOHN WILEY & SONS' Scientific publications Baker* A Treatise on Roads and Pavements 8vo, viii+6f 5 pages, 171 figures, 68 tables. Cloth, $5.00. Baker* A Treatise on Masonry Construction 8vo, about 600 pages, 160 figures and 6 folding plates. Cloth, $5.00. Drinker* Tunneling, Explosive Compounds, and Rock Drills 4to, x+1,175 pages. Profiles, Maps, and over 1,000 illustrations. Half morocco, $25.00 net. Eissler* The Modern High Explosives 8vo, xi+395 pages, 129 figures. Cloth, $4.00. Mutton* The Mechanical Engineering of Power Plants 8vo, xxviii+725 pages, 510 figures. Cloth, $5.00. Ihlseng* A Manual of Mining 8vo, xxii+563 pages, 262 figures. Cloth, $4.00. Kent. The Mechanical Engineers 9 Pockct=Book 16mo. xxxii +1,113 pages, illustrated. Morocco, $5.00. Merrill. Stones for Building and Decoration 8vo, x+557 pages, one double-page and 32 full-page plates, and 24 figures in text. Cloth. $5.00. Molitor Beard. Manual for Resident Engineers Contain- ing General Information on Construction 16mo, iv+118 pages. Cloth, $1.00. Richards. Compressed Air 12mo. v+203 pages, illustrated. Cloth, $1.50. Taylor Thompson. A Treatise on Concrete* Plain and Reinforced 8vo, many illustrations, 400 to 500 pages. Keady October 15, 1904. Walke. Lectures on Explosives 8vo, xvi+435 pages. Cloth, $4.00 net. Webb. Railroad Construction 16mo, xvi+675 pages, 216 figures. 10 plates. Morocco. $5.00. Descriptive Circulars and Catalogues on Application 43 AND 45 EAST 19th STREET, NEW YORK CITY ADVERTISEMENTS. xvii 70 TON BUCYRUS STEAM SHOVEL Especially Designed for Rock Excavation, THE BUCYRUS COMPANY SOUTH MILWAUKEE, WIS. Manufacturers of STEAM SHOVELS DREDGERS OF EVERY TYPE PLACER DREDGING MACHINERY RAILROAD WRECKING CRANES and RAILROAD PILE DRIVERS Catalogues on application xviii ADVERTISEMENTS. BOOKS HALBERT R GILLETTE "Rock Excavation Methods and Cost" Cloth, 5x7^ in., 384 pages, illustrated, - $3.00 "Earthwork and Its Cost" Cloth, 5x7^ in., 256 pages, illustrated, - $2.00 "Economics of Road Construction" Cloth, 6x9 in., 40 pages, illustrated, - - $J.OO DESCRIPTIVE CIRCULARS ON APPLICATION TO Publisher and Bookseller M. C CLARK, 13-21 Park Row - - NEW YORK UNIVERSITY OF CALIFORNIA LIBRARY BERKELEY Return to desk from which borrowed. below. UN 1 2 1952 LD 21-100m-ll,'49(B7146sl6)476 YB 24060