THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES GIFT OF Santa Monica Public Library LIBRARY OF COAL MINING AND ENGINEERING 2-1 Electrical World The Engineering andMining Journal Engineering Record Engineering News Railway Age Gazette American Machinist Signal Engineer American Engneer Electric Railway Journal Coal Age Metallurgical and Chemical Engineering Power COAL MINE SURVEYING BY A. T. SHURICK ASSOCIATE EDITOR, COAL AGE MINING METHODS SELECTED FROM "MINING WITHOUT TIMBER" BY ROBERT BRUCE BRINSMADE, B. S., M. E. PRACTICAL SHAFT SINKING BY FRANCIS DONALDSON, M. E. CHIEF ENGINEER, THE T. A. GILLE8PIE COMPANY McGRAW-HILL BOOK COMPANY, INC. 239 WEST 39TH STREET, NEW YORK 6 BOUVERIE STREET , LONDON, E. C. Enginecrfnt Library 2.7s COAL MINE SURVEYING BY A. T. SHURICK ASSOCIATE EDITOR, COAL AGE COPYRIGHT, 1914, BY A. T. SHURICK PREFACE It has not been attempted to make this book a "treatise" in any sense of the word. With due respect to the numerous comprehensive works on this subject it has been the experience of the author that too little consideration is given to the problems arising in the com- monplace routine of every-day work. In this respect it is believed the subject has been handled in a distinctive manner. Average practice has in every case been given preference to abnormal condi- tions involving problems in precise surveying. Space has been freely devoted to what may seem unimportant details, but which are none the less items that will do much to facilitate the work in the mines. Particular emphasis has been placed on the proper care and ad- justment of instruments regarding which there is a surprising lack of thorough knowledge among most engineers. While the modern instruments of reputable manufacturers seems to have attained the acme of perfection, the transit and level are still delicate mechanisms susceptible to many inaccuracies. Their relatively high cost, and more especially, the peculiarly hard usage to which they are sub- jected in underground work seems to justify considerable elabora- tion along this line. Believing that the best information of this kind is obtained at the point of manufacture, the instrument makers have been quoted exclusively in this portion of the work. In reviewing the manuscript for this book as it is turned over to the printer, the author feels that he has little claim to authorship. Opinions and methods described in the various technical journals and other publications have been freely quoted except where of local interest only. But in all such cases a judicious selection of accepted authorities only have been used, and the author's prerogative of wielding the blue pencil has been freely exercised. A. T. SHURICK. NEW YORK, March, 1914. CONTENTS PAGE PREFACE . . vii CHAPTER I PRINCIPLES OF SURVEYING AZIMUTHS, BEARINGS AND COURSES 'i Azimuths Bearings and Courses. LATITUDES AND DEPARTURES 2 LEVELING 8 Vertical Angle Method Direct Method by the Level. CHAPTER II SURVEYING INSTRUMENTS AND ACCESSORIES THE TRANSIT 10 The Telescope The Cross Wires The Vernier Graduations on the Horizontal Circle. THE LEVEL ' 18 The Telescope Level Bar and Telescope Wye The Tangent Clamp Screw The Leveling Head. LEVEL ROD 20 STEEL TAPES 23 PLUMB BOBS ' 24 CHAPTER III CARE OF INSTRUMENTS -IN GENERAL 26 CARE OF CENTERS AND GRADUATIONS ; . . . . 29 TELESCOPE LENS 30 LUBRICATING 31 LEVEL BUBBLES 33 Mounting Spirit Levels. REPLACING CROSS WIRES 35 ACCIDENTS AND PRECAUTIONS IN THE USE OF INSTRUMENTS 36 TRANSPORTATION OF INSTRUMENTS 39 ix X CONTENTS CHAPTER IV ADJUSTMENT OF INSTRUMENTS PAGE THE TRANSIT 42 The Bubbles To Make the Adjustment for Parallax To Make the Vertical Cross Wire Perpendicular to the Plane of the Horizontal Axis To Adjust the Vertical Wire To Determine Whether the Stand- ards are the Same Height To Adjust the Level to the Line of Colli- mation of the Horizontal Wire. THE LEVEL 45 To Make the Adjustment of the Horizontal Wire To Center the Eyepiece To Adjust the Spirit Level to the Telescope To Make the Lateral Adjustment of the Spirit Level To Make the Adjustment of the Level Bar To Adjust the Horizontal Wire so that the Line of Sight will be Parallel to the Spirit Level. CHAPTER V ORGANIZING AND EQUIPPING THE FIELD PARTY The Chief of the Party The Transitman Chainman and Backsight. 48 CHAPTER VI ENTRY SURVEYING Picking up the Starting Stations Setting Up the Transit Turning Angles Straight Line Work Chaining Taking Side Notes Making Checks Kinds of Stations Painting Stations Numbering Stations. 52 CHAPTER VII KEEPING SURVEY NOTES TRANSIT NOTES 65 LEVEL NOTES . 72 CHAPTER VIII SOME PROBLEMS IN SURVEYING Selected Problems Commonly Met in Coal Mine Surveying .... 76 COAL MINE SURVEYING CHAPTER I PRINCIPLES OF SURVEYING The art of surveying consists essentially in the relative location of different points with respect to each other. The average mining man is too prone to look upon the work of the engineer (or surveyor as he is perhaps more commonly termed in the mining regions) as something uncanny and bordering on the supernatural. He is usually regarded as an expensive luxury, or a necessary evil. No tangible evidence of his labors is notable on the tonnage sheets of the mine he is working in in fact, it is more often the case that he leaves a trail of profane "skinners" who have been delayed, in his wake. Nevertheless he has come to stay and each year finds him occupying a stronger foothold, until now one of the best criterions of an efficient management is shown in the excellence of its en- gineering practice. AZIMUTHS, BEARINGS AND COURSES To determine the location of a point it is obvious that two things are required, the direction and distance from an already known point. Directions are designated as azimuths, bearings and courses. For convenience and in order to have a worldwide standard, so that all surveys of whatever character may be readily adjusted to each other, the true north and south meridian has been adopted as the basis from which all computations referring to direction are made. Azimuths. In Fig. i, it will be noted that azimuths cover the entire range of the circle from o to 360. It is the angle which the line makes with the true meridian, measured to the right in the same direction as the hands of a watch. Thus as will be noted in the figure, line C lies 98 18' to the right of the meridian; line B, 205 30' and line A 338 21'. It is important that the student thoroughly master the principle of azimuths for the reason that they greatly simplify certain processes in surveying which are to be described later. Bearings and Courses. These are terms that are used indis- 2 COAL MINE SURVEYING criminately to designate the direction of a line in one of the four quadrants of the circle, as, northeast, northwest, southeast, and southwest. Sometimes the expression also implies distance as well as direction, as for instance the bearing 276ft. N. 46 i8'E. Bear- ings differ from azimuths in that they are measured both to the east and west of the north and south meridian and that they never exceed 90 in value. Thus in Fig. i the bearing of C equals the angle SOC, or the difference between the azimuth of SO (180) and OC (98 18') which equals 81 42'; and since the line lies between PIG. I. SKETCH SHOWING VARIOUS AZIMUTHS AND BEAKINGS. the due east and due south meridians the bearing is obviously S. 81 42' E. The bearings of the other lines in the figure are arrived at by the same process. LATITUDES AND DEPARTURES When the survey of a mine has been completed the problem then arises of making an exact and accurate reproduction of the mine workings on a small scale. In other words, building the map. There are two general methods of accomplishing this. By plotting with a protractor and by computing the latitudes and departures and plotting the survey from them. PRINCIPLES OF SURVEYING 3 Plotting by means of a protractor was at one time a popular method of working but it is now obsolete and has been practically abandoned. The possibility for error is too great by this method unless great care is exercised and even then it is not to be relied upon for any very extended work. The method is still used in laying out short or approximate surveys but it is rather dangerous for the reason that any mistakes in plotting one chord are carried through the balance of the work, and are accumulative. In latitudes and departures the northing or southing and the easting or westing of each bearing is computed by means of sines and cosines; that is the distance due north or south and due east or west (depending upon which direction the bearing is in). The algebraic sums of all the bearings in the survey are then obtained and each station plotted according to its distance due north or south and due east or west of an assumed zero point, termed the zero of coordinates. The method is probably best described by means of an example. Referring to the accompanying Table I it will be assumed that the field notes for a survey as given in the columns under "Sta.," "Azimuth" and "Distance" have been turned into the office and it is desired to traverse them and find the latitude and departure of each station. It is first necessary to reduce the azimuths to bearings, this having been already explained. The latitude and departure of each course is then found by multiplying the length of the course by the cosine and sine, re- spectively. Thus, the latitude of the first course being a northing (N) and the departure an easting (), they are found as follows: N=i45 cos 43 i8' = i45Xo.72777 = io5.53 ft. =145 sin 43 18' = 145X0.68582 = 99.44 ft. In this manner, the northing or southing and the easting or westing of each course is calculated and written in the proper column under "Singles" as shown in the table. Having found all the single latitudes and departures for all the bearings we next proceed to obtain the "Doubles." The single latitudes and departures are the distances which that particular course goes north or south and east or west, while the doubles are the total distances north or south and east or west of each point from the zero of coordinates. The doubles are obtained by simply adding or subtracting the singles, as the case may be. Referring to Fig. 2 which is a plot of the survey under considera- tion, the lines NS and WE are due north and south, and east and west, COAL MINE SURVEYING 3 CO w N ro * 10 vO ^ 00 0*O * 8 ft j Si ! i * t 8 M ' '^ t~~ *O ^ M N . 10 *O OO >0 vO s M . ^ oo *5 * * ; ; 3 !!!'.. & Tt 00 ^O O CO M Q> t- O " w H . B s p fe CO Tj- M * O "1 O * I s - O 1 : :, :& : ,2 3^^ : 5 tj 1 * : : : S : * 5^ s : H" 5 * . - 5 tf) * Tj- M -00 ' W W w s : : 5^vo S 0 ^co H' 5 it C jww^w^^^^w^ S : < 2?^i?2S >< S~? 5 . w |Tj-vOt^vO Oo" 5 ^ 5 ^ i^cocococo^coco^;^; 3 .00 >Of2toioO vooooo O i rj- 1-1 VOMOO t^-OO i O w c* PO^*IO\O r^oo OO 1 1 1 1 1 1 1 1 1 t O>-iNTj-.o>or^ooOv PRINCIPLES OF SURVEYING 5 respectively. Their intersection is the assumed zero of coordinates and is therefore the point that has neither a northing, southing, east- ing or westing. Sta. o, which is the starting point of the survey, is known from a previous survey to have a northing of 108.00 ft. and a westing of 138.00 ft. as will be observed by reference to the map. Accordingly we set down 108.00 in the northing column under the doubles and 138.00 in the westing column. From Sta. o to i, according to the single latitude and departure for this course, we go 105.53 ft. north and since the double latitude is FIG. 2. SKETCH OF A SURVEY PLOTTED BY LATITUDES AND DEPARTURES. already north this is added to it, giving a latitude of 213.53 ft- be noted on both the table and map. Similarly, the course o to i takes us 99.44 ft. east. In this case, however, our double is a westing so that we subtract instead of adding as in the previous instance. Thus we have the rule: When the single latitude or departure is in the same direction as the double it is always added and when different it is always subtracted. On the plot, Fig. 2, all of the latitudes and departures of the 6 COAL MINE SURVEYING different points have been noted. Beginning at Sta. i and following around to Sta. 4 it will be noted that the stations lie to the north of the east and west line and hence are northings as will be observed by reference to the double latitude and departures. Between Stas. 4 and 5 the traverse crosses to the south and continues there up to Sta. 9 as will be seen by reference to both the map and the table. Fol- lowing the departures around in a similar manner we find that the survey crosses from a westing to an easting between Stas. i and 2, shows another small westing at Sta. 3 and then continues an easting up to Sta. 7; between Stas. 7 and 8 it changes to a westing and remains so the remainder of the survey. It will also be noted that this is a tie survey; that is it completes a circuit and ends at the point of beginning and therefore must balance. Referring to the double latitudes and departures we find that the final coordinates for the Sta. o correspond exactly with those at the beginning, and therefore a perfect check has been obtained. It might be well to add that a survey in practice which checked perfectly would be open to suspicion as such a tie is seldom or never obtained. The following is a description of the Consolidation Coal Go's, methods of computing latitudes and departures: The first step in the office work is to reduce all slope measure- ments to horizontals. These calculations are performed in dupli- cate, one set by a table of Gurden and Naturals and the other by log- arithms and the results check one against the other. The trans- itman in the meantime transfers his data as far as possible to tra- verse sheets, copy of which is shown herewith. Usually each mine entry has an individual traverse sheet for the stations it contains. After the horizontals are copied into the notebook and checked, the courses and corresponding distances are then copied into a separate set of calculation books and the latitude and departure differences worked out by the same method employed for horizontals, and also checked. The results are copied on the traverse sheets and the total latitude and departures worked out and checked before plotting. No survey is permitted to stand until approved by the division engineer in charge. His approval is shown on the space provided for his signature at the bottom of the traverse sheet. All sheets are carefully referenced from one to another when the surveys have any connections whatever. A separate folio or binder is used to hold the sheets for each mine and they are numbered consecutively from "one up"; the sheets are of course all indexed. PRINCIPLES OF SURVEYING I | o 1 ** II M W |ll i % \ uotrog N 2 " 3 8- ^2 r?^ ^ ^2 * : i?" 8 a 1 I HI If III i a "* * g * 0, n : P : &| " 'S n ^ j ^1 ?I 1 o IM |1| !, i s ? si r i m S o <*3 - !& i o ji f !|i| - it | H .S -1 5 i< j ^ (V) O C if o i 1 Pi o I 1 W W S ? V ' en g ^3 & -41 o ^ 1 . 1 *is E5 3 33B d c3 3 8 COAL MINE SURVEYING LEVELING In addition to the location of points in a horizontal plane there is also the necessity of determining the relative elevation of different portions of the mine workings. This branch of surveying has not received so much attention as the other and in fact is often entirely neglected unless some special occasion arises where it is required. It is none the less important however and will no doubt find a more general application in time. There are two distinct methods of leveling indirectly by vertical angles and directly by the level, an instrument designed especially for this work. The vertical angle method is not in much favor on outside work and except in special cases it is seldom or never used. But in the narrow confines of a heavily pitching seam of coal the adoption of this system becomes imperative so that the coal engineer must be prepared to handle it. Vertical Angle Method. In this system the difference in elevation between any two points is arrived at by measuring the vertical angle between them by means of an ordinary transit, and the slope distance. We then have the hypotenuse of a right angled triangle and one angle given so that the vertical distance is easily computed by multiplying the sine of the angle by the distance. It should be remembered in this connection that the average transit is not usually equipped with a sufficiently accurate vertical arc to insure absolute correct results on work of this kind. In fact the arc should be as large and rigid as in the case of the horizontal plates where equally accurate results are desired. In ordering an instrument it is well to consider the geological features of the district carefully and where the measures are steeply inclined a special vertical arc should be specified. Direct Method by the Level. As already noted this is the system in most general use and the one to be given the preference where accuracy is desired and the inclinations not too abrupt. It consists essentially in carrying forward a series of horizontal planes, either up or down as the case may be, as shown in Fig. 4. When properly adjusted the level is an instrument that may be turned in any direction in a horizontal plane and will always show identically the same elevation. Thus in Fig. 4 let it be assumed that it is desired to ascertain the difference in elevation between the points A and on a hillside. The instrument is set up at any point B not too high so that the rod will not be seen, and a reading on the latter taken at A. Say this reading shows 11.58 ft.; PRINCIPLES OF SURVEYING 9 it is clear then that the instrument is this distance above the point. The rod is then moved ahead to another point at about the same elevation as the instrument and another reading taken. Assuming the reading at this point to be 0.42 ft. this indicates that the new point C is this distance below the instrument and the difference between 11.58 ft. and 0.42 ft. or 11.16 ft. above the starting point A. Moving the instrument up to D this time, the operation is repeated FIG. 4. SKETCH SHOWING LEVELING PROCESS. as follows: Assuming the rod reading on C from the new set-up at D shows 10.50 the height of the instrument above the initial point is then 11.16 plus 10.50 or 21.66 ft. Finally placing the rod on the desired point E we find this to be say 0.12 ft. below the instrument so that the difference in elevation between A and E is 21.66 minus 0.12 or 21.54 ft. And so the operation maybe extended indefinitely. CHAPTER II SURVEYING INSTRUMENTS AND ACCESSORIES In the ordinary surveying, as practised in the coal mines of this country, comparatively simple equipment suffices; in fact it might be said the simpler, the better. The principal instruments used are the transit and level, together with such accessories as leveling rods, sight rods, plumb bobs, steel tapes, etc. The average layman invariably has the compass also associated with anything in connection with surveying. As a matter of fact, the compass has been practically abandoned altogether for use in this connection, and could be dispensed with entirely with little inconvenience. However, it is of some use as an approximate check on the work with the vernier, and is still a part of nearly all transits probably more because it has become a custom and also because the space so utilized could not be applied to an advantage in any other way. THE TRANSIT The most important, and at the same time most complicated and expensive instrument used on the mine survey is the transit. Illustrations of two' popular makes of transits are shown herewith. The first, Fig. 5, is a halftone of the Kueffel & Esser instrument, while the second, Fig. 6, is a cross section through the center of a C. L. Berger transit. In both illustrations all the parts of the two instru- ments are numbered, and the names of these will be found in accom- panying tables. The transit is an instrument designed for measuring angles in both horizontal and vertical planes, although its use is more com- monly confined entirely to the former. To adequately fulfil its purpose, the instrument must be rigidly constructed, with all parts in absolute adjustment. Rapid advances in the method of manu- facturing instruments have been made in the past decade, with the result that the modern transit is a model of accuracy and conven- ience and will successfully withstand as much ill usage as may rea- sonably be expected from so delicate a machine. Beginning at the bottom and working up, it will be noted on refer- SURVEYING INSTRUMENTS AND ACCESSORIES ring to the drawing, Fig. 6, that the tripod head is shown at i with various parts of the tripod at 2, 3, 4 and 5. The tripod is entirely distinct from the instrument, but the head, i, is equipped with screw threads, as shown in the drawing, on to which the instrument foot plate screws. The foot plate, or tripod plate, is shown at 6 in Fig. 6, and 13 in Fig. 5. 1. Objective head 2. Telescope 3. Telescope axis end cap 4. Vertical circle 5. Vertical circle vernier. 6. Standard 7. Plate level 8. Horizontal limb 9. Lower clamp tan- gent screw 10. Lower clamp 11. Leveling head 12. Leveling screws 13. Tripod plate 14. Pinion head (ob- ject focusing screw) 15. Standard cap 16. Telescope clamp 17. Reticule adjust- ing screw 18. Eyepiece focus- ing screw 19. Eyepiece focus- ing lock nut 20. Eye end ring 21. Eyepiece cap 22. Telescope level support 23. Telescope level adjusting screw 24. Telescope level 23. Telescope clamp tangent screw 26. Compass cover glass ' 27. Capston head pinion 28. Vernier cover glass 29. Upper clamp tan- 13 gent screw 30. Upper clamp 31. U pper clamp collar 32. Clamp collar 33. Lower clamp screw 34. Half ball joint 35. Shifting plate 36. Leveling screw shoe FIG. 5. TYPICAL TRANSIT. The shifting plate of the instrument in Fig. 6 is shown at n. The purpose of this is to permit of the final movement necessary to get the instrument precisely over or under the point, this being ac- complished by loosening the level screws 9, so that the plate hangs relatively loose. To avoid indentations in the foot plate, by the leveling screws turning directly upon the plate, leveling screw I2 COM, MINE SURVEYING cups are provided, as shown at 10. Turning to Fig. 5, the leveling screw, and cups are shown at 12 and 36, respectively. The plumb bob suspending cup with the accompanying chain and hook are shown at 12 and 13, respectively, in Fig. 6; these are arranged so that a bob hung in the hook 13 will hang precisely under Tripod head Tripod bolt Tripod bolt nut Tripod bolt washer Tripod leg Foot plate Ball-and-socket joint Leveling head Leveling screws Leveling screw cups Shifting plate Plumb t>ob suspending cup ; Plumb bob chain and hook Repeating center Clamp collar Lower clamp Lower clamp thumb screw Lower clamp tangent screw Lower clamp spring, not shown Lower clamp piston, not shown Lower clamp cap, not shown Inner center Horizontal circle Vernier plate clamp Vernier plate clamp screw Vernier plate Vernier plate tangent bracket Vernier plate tangent screw Vernier plate tangent spring Tangent spring piston Tangent spring cap Horizontal vernier Veriner cover glass Vernier shade frame Vernier shade glass Compass cover glass Needle Needle pivot Needle lifter Needle lifter screw head Front plate level Front plate level vial Front plate level adjusting n Front plate level rocker Standard with adjusting screw Standard adjustable wye bearing Standard cap and screws Side level Side level adjusting screw Sjde level fastening screw Side level rocker Side level vial Telescope axis -71 SI: 54- Telescope barrel 55. Eyepiece mounting 56. Spiral groove screw 57. Terrestrial eyepiece 58. Eyepiece cap 59. Eyepiece ring 60. Wire recticule 61. Wire recticule adjusting screws 62. Pinion and washer, not shown 63. Pinion head 64. Pinion head screw 65. Pinion head saddle 66. Pinion head saddle screws - 67. Object slide * 68. Object head 47 69. Object glass cell -46 7' Object glass 71. Object slide dust guard 72. Sun shade L 73. Telescope clamp ' 74. Telescope clamp screw 75. Telescope clamp washer Telesco pe t l cir tangent 77. Vertical circle 78. Vertical circle guard 79. Vertical circle guard ser 80. Vertical vernier 81. Vertical vernier screws FIG. 6. CROSS SECTION OF A TRANSIT. the theoretical center line of the instrument. The ball-and-socket joint, which is something on the order of a flexible coupling, is shown at 7 in Fig. 6, and 34 in Fig. 5. This allows the upper part of the instrument to assume any necessary angle of inclination to the tripod plates, so that it will be absolutely level. The leveling head, through which the leveling screws work, is SURVEYING INSTRUMENTS AND ACCESSORIES 13 shown at ii in Fig. 5, and 8 in Fig. 6. In Fig. 5 the lower clamp for clamping the horizontal plate is shown at 33, and the tangent screw at 9, these same devices being shown at 17 and 18, respectively in Fig. 6. The upper or venier plate clamp is shown at 30, with the tangent screw at 29, in Fig. 5, the same thing being shown at 25 and 28 in the separate detail in Fig. 6. This latter detail also shows the principle upon which the slow motion screws work. It will be noticed that this is essentially a small cylinder containing a spring 29, held in place at one end by the milled head cap 31, and at the other by the tangent spring piston 30. The tendency is naturally to push the piston out so that the latter is constantly bearing against the clamp upon which it acts. Thus by turning the tangent screw 28, the cylinder is either forced in or out as the case may be. By this means, an infinitesimal movement of the vernier plate can be obtained so small that it cannot be detected by the naked eye. At 23 in Fig. 6 is shown the horizontal plate or limb which is also shown in Fig. 5 at 8. The vernier plate is shown at 26 in Fig. 6, with the vernier at 32, and the vernier glass at 33, this latter being shown in Fig. 5 at 28. The vernier shade is shown at 34 in Fig. 6, this being removed on Fig. 5. The compass needle is shown in Fig. 6 at 37, and the lifter, which brings the needle tight against the compass glass when not in use, so as to save it from unnecessary wear, is shown at 39, the screw head by which this is accomplished being shown at 40, and the glass at 36, this latter also being shown in Fig. 5 at 26. All transits are equipped with two level bubbles, placed at right angles to each other so that the instrument can be leveled in both directions. In Fig. 6, these levels are shown at 41 and 48, and their relative positions may be more adequately noted in Fig. 5, one being shown at 7, and the other about halfway up the standard 6. The standard in Fig. 6 is shown at 45, and the adjustable wye bearings for correcting the bearing adjusm en tare shown at 46, with the cap at 47; this latter is also shown in Fig. 5 at 15. In Fig. 5 the vertical circle for measuring vertical angles is shown at 4, with the vernier at 5; this is also shown in section in Fig. 6, the vertical circle itself at 77", the surrounding guard for protecting the circle, which will also be observed in Fig. 5, at 78, and the vernier with its adjusting screws at 80 and 81, respectively. The vertical circle guard is held in place by milled head screws, one of which is shown at 79. 1 4 COAL MINE SURVEYING The telescope clamp for clamping the telescope in any vertical position desired is shown at 1 6 in Fig. 5, and the tangent or slow mo- tion screw for setting same accurately in place at 25. This arrange- ment is also shown in Fig. 6, the clamp at 73, with the clamp screw at 74, and the tangent screw at 76. The telescope is shown at 2 in Fig. 5, the objective head at i, and the eyepiece cap at 21. The eyepiece focusing screw is shown at 18, the lock nut for same at 19, and the eye end ring at 20. The reticule screws for adjusting the cross wires are shown at 17. Under- neath the telescope and attached to it is the telescope level 24 which must always be leveled up with the other bubbles when setting the instrument up under a station. The telescope level support and adjusting screws are shown at 22 and 23, respectively. The telescope as shown in Fig. 6 gives greater details. The eye- piece cap is shown at 58, the mounting for the eyepiece at 55, and the spiral, groove screw at 56. The reticule for carrying the cross FIG. 7. TYPES OF "CROSS WIRES USED IN LEVELS AND TRANSITS. wires is shown at 60, and the screws for adjusting these to their proper position at 61. The barrel of the telescope is shown at 54, with the object slide just inside of it at 67. The pinion head for adjust- ing the telescope for any length of sight is shown at 63, with the pinion saddle at 65. The slide dust guard for preventing foreign matter from getting inside the telescope is shown at 71, and the object head at 68, with the object glass at 70, and the barrel for holding same at 69. The sun shade for preventing the sun from shining directly on the object glass when taking a sight is shown at 72. Cross Wires. Some of the different styles of cross wires used in the present-day instruments are shown in the accompanying illus- tration, Fig. 7. The first style on the left is an unusual type of cross hair used m wye levels, the idea of the two vertical wires being to check up the rodman in holding his rod plumb. The second illus- SURVEYING INSTRUMENTS AND ACCESSORIES 15 tration from the left represents the simplest form of cross wire used, and one that is also quite popular; it consists of only a single vertical and horizontal wire. Next to this is the stadia wire, which is iden- tical with the one just described, except that two additional hori- FIG. 5. TYPES OF VERNIERS. zontal wires have been added for making stadia measurements. The last figure on the right shows the stadia wires as just described with diagonal wires added, the idea of the latter being to help locate either the vertical or horizontal wire when working in the mine. This is a valuable addition in this respect, and one that might be used to advantage on all mine transits. 1 6 COAL MINE SURVEYING The Vernier. The vernier is a device for accurately measuring fractions of subdivisions on any kind of a scale. Verniers on transits designed for reading to i' are shown in the accompanying illustra- tion, Fig. 8. This is the typical style used on ordinary mine surveys; in fact, it might be said that it is used almost to the exclusion of any other graduation. These verniers depend upon the principle that if 29 subdivisions on the outer circle equal 30 subdivisions on the inner circle, the difference in length between a subdivision on each scale is equal to -fa of the outer subdivision; since the outer subdivisions in this case are equal to ? or 30' this value is therefore i'. With this principle once clear in the mind, reading the vernier becomes a comparatively simple problem. Thus referring to the vernier B in Fig. 8, and assuming that it is desired to know the reading on the outer circle of figures we first select the closest even degree, which in this case is obviously 332, the smallest divi- sions on the outer circle being 2 an d the next larger full degrees. It is also clear that the zero on the vernier (which is the inside scale) is something more than a | or 30' greater than 33 2, so that we have this additional quantity and all that remains to be obtained is the odd minutes. To obtain these, we look along the graduations on the vernier itself, in the same direction in which the reading is being made, that is, to the left in this case, until we find a line that ex- actly coincides with a line on the outer circle, which in this case is the fourth subdivision. This indicates that the zero on the ver- nier is -gV of the distance between the two subdivisions on the outer circle, which as was already explained equals 4'. Referring to vernier A, we find that this reads to even degrees, the zero on the outer circle exactly corresponding with the zero on the vernier. Vernier C is the same, except that this reads exactly 5. In vernier D, however, we again find a reading to odd minutes. Assuming that it is again desired to read the outer circle of figures it is readily noted that the reading is somewhat greater than 152! or 152 30'. Glancing along the inner circle from the zero to the left we find the first line to correspond at 5, which is of course, as^already explained, equal to 5', and the reading is therefore 152 35'. In the same way, we find the reading of vernier E to be 342 35'. The verniers here given are typical of those used on the average instruments. Graduations on the Horizontal Circle. The accompanying illus- tration, Fig. 9, shows two types of graduation commonly used on the SURVEYING INSTRUMENTS AND ACCESSORIES 17 mine transits. The outer one is graduated from o to 360 in both directions, that is, both to the left and right. The inner graduation is the one necessary for running continuous vernier, as will be described later, and should be on all mining transits. The gradua- tion on the outer circle is of no particular value unless it should some time prove desirable to work with the telescope reversed. FIG. Q. METHODS OF GRADUATING HORIZONTAL CIRCLES. The smaller or inner circle of graduations is perhaps the most useful for general mining practice there is. As will be noticed the outer circle of figures is graduated for the continuous vernier as already mentioned, w r hile the inner one is graduated for reading courses direct, that is the graduations run both ways from o at iS COAL MINE SURVEYING both the north and south ends terminating at 90 on both the east and west. Where it is the practice (as for instance in the engineer- ing department of the Consolidation Coal Co.) for the instrument- man to read both the azimuth and bearing of all sights, this style of graduation is essential. It is also more convenient when turning rights and lefts as is practised in railroad surveys, and is useful as well in laying out right-angle work in the mine. By referring to the accompanying illustration, Fig. 10, which repre- sents the method of lettering a compass it will be observed that the east and west marks are the reverse of what they actually are. Thus when the needle is pointing to the north, as shown in the left-hand illustration, east would be to the right where the W is and west to the left where the E is. This is done as a matter of convenience and to avoid the possibility of error in reading. Referring to the right-hand illustration in Fig. 10, let it be assumed that the line of sight being taken is in the direction indicated, the ^^ Q Pointing tO the tTUC north, as is also shown. It is clear that the line of sight is to the left or northwest, which is also the reading shown, that is, the needle falls between the N and the W indicating a northwest reading; were the lettering placed in the reverse order as is the case on most small pocket compasses, the reading would have been northeast, which would of course have been wrong. This same condition applies to vernier readings taken on the horizontal circle of a transit and explains why the graduations are arranged as they are. COM.\6C FIG. 10. METHOD OF LETTERING THE COMPASS. THE LEVEL As has already been mentioned, the level is an instrument for determining relative elevations. When properly adjusted, it turns in a horizontal plane showing exactly the same elevation in whatever direction the telescope may be pointed. SURVEYING INSTRUMENTS AND ACCESSORIES 19 The accompanying illustration, Fig. u, shows a typical Keuffel & Esser level, one of the popular makes in the market to-day. As will be observed, the different parts are numbered, the subjoined table giving the technical name for each. It will also be noted that many of the names for the different parts correspond to those already given in the description of the transit. Most of the con- cealed parts, as, for instance, the interior of the telescope, and the half-ball socket joint are the same as in the transit, and reference to the line drawing, Fig. 6, may be made for determining these. The Telescope. At i, in Fig. n, is the objective of the telescope and 7 the eyepiece tube, with the micrometer focusing screw and adjusting nut at 20 and 19 respectively. The adjusting screws for correcting any error in the cross wires are shown at 6. One of the wye yokes is shown at 2, 3 and 4, the spring lock being at 2, the spring contact at 3, and the yoke catch at 4. These yokes may be thrown back, and the telescope lifted out, as is necessary when mak- ing adjustments. At 5 is shown the rack and pinion thumb-screw for focusing the telescope. The level bubble tube by which the instrument is leveled up is shown at 12. It is first set across one opposite pair of leveling screws and leveled, and then swung across the other two, and the operation repeated until the bubble is exactly level in whatever position the telescope may be turned. The bubble is always adjusted with re- gard to the line of sight through the instrument, such adjustment being effected by means of three screws, one on the left at n and two on the right at 24 and 25. Level Bar and Telescope Wye. The level bar is shown at 13, at each end of which are the two wyes for supporting the telescope. At 9 and 10, and 22 and 23 are shown the two sets of adjusting nuts for making corrections in the elevation of the wyes. At 21 is the stop lever to prevent the telescope from revolving around in the wyes. The tangent clamp screw is shown at 26, and the collar at 14. This is useful occasionally when it is necessary to take a series of sights on a rod at some particular point, or in some certain direction. The tangent screw for slowly shifting the range of the telescope is shown at 27. The leveling head of the instrument is shown at 15, with one of the leveling screws at 16, and a leveling screw shoe at 17. This part of the instrument corresponds almost identically with that already described for the transit. At 28 is the half ball socket joint 20 COAL MINE SURVEYING which allows the horizontal line of the instrument to be at any angle with the tripod head, shown at 18. The top of the tripod is seen below. LEVEL ROD In the illustration, Fig. 12, is shown one of the modern mine level rods, a product of the Keuffel & Esser Co. This rod is a trifle FIG. II. TYPICAL WYE LEVEL USED ON MINE WORK. I. Objective 2. Spring lock lever for wye yokes 3. Spring contact 4. Wye yoke catch 5. Rack and pinion thumb- screw (focusing screw) 6. Adjusting screws for cross-wires 7. Eyepiece tube 8. Telescope wye 9. Wye adjusting nut 10. Wye adjusting nut u. Level bubble adjusting nut 12. Level bubble tube 13. Level bar 14. Tangent clamp collar 15. Leveling head 16. Leveling screw 17. Leveling screw shoe 1 8. Tripod head 19. Adjusting nut 20. Micrometer focusing screw 21. Stop-lever 22. Wye adjusting nut 23. Wye adjusting nut 24. Level bubble adjusting nut 25. Level bubble adjusting nut 26. Tangent clamp screw 27. Tangent screw 28. Half ball socket joint over 3 ft. long, overall, and can be extended to 5 ft. This is one of the most common, in fact it might be said, practically the only type of level rod used on mine work. W SURVEYING INSTRUMENTS AND ACCESSORIES 21 Referring to Fig. 12 which shows the completed rod, the target will be observed near the top, and a set screw arrangement for clamp- ing the rod in position when extended is shown at A. Near the bottom of the rod at D is a metal sleeve which is a part of the tele- scoping arrangement, being attached to the back half of the rod and sliding along the front part. The extreme bottom of the rod at F is bound with a substantial iron ferrule which provides against any important wear and con- sequent inaccuracy to this much abused part. As will be noted, the graduations on the rod extend from zero at the bottom to 3 ft. at the top, the decimal system of tenths and hundredths of course being used instead of inches. The tenths of feet are plain black figures, the even foot marks being indicated by a slightly larger figure in red. In Fig. 13 is shown an enlarged view of the target. The target is simply a circular disk with an oblong portion removed in the center. The zero of the tar- get is indicated by sharp changes in the color arrange- ment in order to bring this out prominently, the two colors most commonly used being red and white, as indicated on the half-tone by R and W respectively. To the right at C will be noted a slit and small cir- cular hole in the target which is used on under- ground work only. The rodman, by holding his light behind the target and allowing it to shine through this slit brings out a sharply defined isolated mark which the instrumentman cannot fail to readily locate. A modern helpful addition to the target is the device shown at B. This is a slow motion arrangement by which the target is more conveniently set at the exact joint. On mine work, particularly, the damp atmosphere results in a certain swelling of the wood so that the target is often stiff, and with the rodman endeavoring to hold the light with one hand and move the target an infinitesimal amount, while at the same time holding the rod plumb, the results are often trying on the patience of all concerned To obtain the reading of the target, set at any point on the rod, first note the nearest foot mark beneath the target which gives the full number of feet in the required reading. Next observe what 22 COAL MINE SURVEYING tenth mark on the rod cuts the small scale on the target, this being i in the illustration, Fig. 13. Finally, note the reading on this small scale at the before mentioned tenth mark which in this case is .07, or to be more exact about .073 if it is desired to carry the readings to thousandths. The even foot mark in this illustration obviously occurs between the 9 and the i on the rod and is therefore covered FIG. 13. DETAIL OF .TARGET ON THE MINE LEVEL ROD. by the target. Assuming this to be 2 we then have a reading of 2.173 ft. When it becomes necessary to use "long rod" the target is run up as far as it will go, which is to the 3-ft. mark (see Fig. 12) and clamped tight. The set screw A is then loosened, the rod extended to the required height and the set screw again clamped. On the back of the rod will be found another small scale the same as in the target and the reading is taken in the same way, except that it is made from the top down, instead of from the bottom up as in the first case. SURVEYING INSTRUMENTS AND ACCESSORIES 23 STEEL TAPES Unusual conditions obtain in mine surveying that accentuate the possibility of error in chaining and the difficulty in obtaining reliable results. Where the average engineer doing outside work is liable to lose his temper should a thoughtless chainman inadvertently drag the tape through mud or water, the inside man has long since ac- cepted this as a matter of course. The outside engineer is doing his work in broad daylight where the most casual attention only is required, while the inside man is working in a pitch blackness where kinks in the tapes are seldom found until too late, where it is difficult to tell if the tape swings free and truly on the line, and where the limited working room requires constant winding and unwinding of the tape. As a result of these abnormal conditions, a distinctive style of tape has been developed on mining work. This is the ribbon or flat wire tape, as shown in Fig. 14. These tapes are ordinarily | in. wide, FIG. 14. FLAT WIRE OR RIBBON TAPE USED IN MINE SURVEYING. and usually about 300 ft. long. Some engineers prefer even a lighter tape only -jV in. wide, and have them in lengths up to 500 ft., and even more on occasions. As noted in Fig. 14, the graduations on this type of tape are stamped on brass sleeves, which have been either clamped or soldered onto the tape. The figures indicating the number of feet from zero are noted, together with a line and a notch on each side at the exact point. These graduations are usually put on every 5 ft. although sometimes 3 ft. is used. The less there are, the more accurate the tape will be, and the less expensive. The $-f t. gradua- tions are therefore probably the best, particularly as the experienced man soon becomes so accustomed to this style that he can handle it as rapidly as the 3-ft. graduations. These tapes are made of the toughest flexible steel ribbon, carefully tempered, so as to withstand breaking under the hardest usage. They are graduated according to the standard of the National Bureau of Standards, and are correct at 62 F. On the ordinary mine surveying work, it is not necessary to make corrections for temperature or the tension on the tape. Another advantage of these 24 COAL MINE SURVEYING tapes is the facility with which they can be repaired. This latter contingency is one that must be anticipated and prepared for even with the well- trained corps. The following method of effecting re- pairs, selected from a number appearing in Engineering News several years ago, will be found convenient: Small pieces of copper, or tin from an old tin can, are cut into strips say f in. wide, and then cut crosswise of a size that will lap around the tape to be mended and just about meet on the flat side of the tape not the edge. These, with an ordinary candle, a piece of solder and some stick flux (both of which latter may be obtained from any electric plant), a small flat file and a pair of small nippers complete the outfit. These may all be put into a small sack and carried in the pocket, where they are always ready, and when a tape is broken it can be repaired in the field in five minutes, thus saving time and the inconvenience of using a broken tape, or going a long distance to get it repaired. One end of the tape is used as a "form" about which the clasp is bent. The tape and clasp should be brightened with the file before the clasp is bent into the proper shape. When the tape is put together, clamp the clasp tightly about it with the nippers; heat in the candle and put sufficient flux on to run under the clasp; then hold the solder on the splice until it has melted and run under and about the clasp; allow it to cool without movement of the ends of the tape and the work is done. The above " outfit" does not weigh over a pound, and is all that will be needed, thus doing away with a machine shop for doing a little tape splicing. Tapes can easily be mended in this manner so that they will hold all a man can pull. The stick flux is much more convenient than a bottle of acid and zinc, as it cannot be broken, and does the work as well as the acid. PLUMB BOBS Plumb bobs are used in mine work for giving sights, but more particularly for setting up the instrument. There is little choice in the matter of bobs, Figs. 15 and 16 showing the two principal varie- ties on the market. Fig. 15 shows the standard type of plumb bob most commonly used. It conforms to the general plan adopted since plumb bobs were first made, and has successfully maintained its leadership to the present day. Fig. 16 shows a relative new type of bob made of nickel steel instead of brass, as is the one shown in Fig. SURVEYING INSTRUMENTS AND ACCESSORIES 25 15. This new type is much preferred by many colliery engineers who claim that it offers much less resistance to the rapid air current pre- vailing in some parts of our mines, and it is much easier to work with PIG. 15 FIG. 16 under such conditions. Some also find the cylindrical form more convenient for handling as compared with the conical form of the old style bob. CHAPTER III CARE OF INSTRUMENTS Note. Abstracted from publications of the C. L. Berger Co. The first requisites in the outfit of the engineer are the engineering instruments, transit, level, rods, tapes, etc. The perfect instru- ment becomes a part of the operator, like his skillful hand and educated brain, and in like manner can be depended upon. To make such an instrument requires long experience, great skill, and the use of delicate and expensive machinery. Some of the machinery, like the automatic dividing engines, require many years of construc- tion and perfection. Before purchasing of any particular manufacturer, consult engineers of long experience and high standing, as to the merits of the instruments of different makers. A certain high quality in instruments is requisite to do good work quickly. Do not let the mat- ter of a few dollars in the difference in price influence you to purchase that for which you may soon have to apologize. Patronize a firm that has a well-established record for fair dealing and for reliable work that will give you full value for your money. The perfect instrument is so made that every part is designed with reference to every other part. Strength, weight, rigidity, and sta- bility under wind pressure, are carefully considered, as well as in the form, the material, the life and the action of the tripod, movement, centers, bearings, leveling and tangent screws, telescope slides, the power and clearness of the telescope, the sensitiveness of the levels, the accuracy of the graduations, and the simplicity of the manipula- tion. The instrument must be constructed so that it can be used in all climates and under all conditions, and when exposed to wind pressure all tremor and vibration is eliminated, and lines and angles can be laid out and measured correctly without any anxiety as regards results and nervousness therein on the part of the manipu- lator. IN GENERAL Do not allow the legs of your tripod to play loose on the tripod head; keep nuts and bolts always well tightened up against the 26 CARE OF INSTRUMENTS 27 wood. Examine the shoes from time to time, and sharpen them if necessary, also screw the shoes tight, if wear and tear loosen them. Be sure your instrument is well secured to its tripod before using it. Bring all four leveling screws to a seat before shouldering instru- ment. Let the needle down upon its pivot as gently as possible, and allow it to play only when in use; if too far out from its course, check movements of needle carefully by means of lifter. Never permit playing with the needle, especially not with knives, keys, etc. Be sure to arrest the needle after use, and screw it well up against the glass cover before shouldering the instrument. Do not clean the glass cover or the lenses with a silk handkerchief; breathe over the compass glass and reading lens if one is used, after cleaning. To clean the object glass and the lenses use a fine camel- hair brush. If dust or sticky or fatty matter cannot be removed with the brush, take an old clean piece of soft linen, and carefully wipe it off. Do not unscrew the object glass unnecessarily as this is apt to disturb the adjustment of line of collimation. The lens nearest the eye of eyepiece, as well as the front side of the object glass, need careful brushing with fine brush from time to time. If dust settles on cross hairs and becomes troublesome, unscrew the eyepiece and object glass, and gently blow through the telescope tube, cover up both ends and wait a few minutes before inserting the eyepiece and object glass. Be sure to have the object glass cell screwed well up against its shoulder, and then examine the adjust- ment for the line of collimation. Do not grease the object slide of telescope, or screws that are exposed to dust; use a stiff toothbrush to clean slides or threads if dusty. If the focussing slide seems to work too hard, everything else being right, it is generally caused by the lubricant on the pinion hardening in cold weather, and the same cause may also make the focussing slide work too freely in hot weather by softening, i.e., when not stay- ing in place when in a vertical position. Fretting of the focussing slide is usually due to the inrush of air carrying dust and grit when slide is being run out causing momentarily a rarefied space. This may be prevented by wrapping a piece of chamois skin over the barrel in shape of tubular form and fasten by means of rubber bands or sewing. In an emergency fine watch-oil may be used to grease the slide should it continue to fret, until the instrument can be sent to the maker. In case of rain during non-use, place the telescope vertical, object end up, and no water can enter the telescope. Never use emery in any form about any part of a transit or a level, 28 COAL MINE SURVEYING whether tangent screws, slides or centers. If anything must be used, a very little powdered pumice-stone mixed with fine watch- oil is all that is advisable, and after grinding, then clean thoroughly. The uninitiated are advised to do no grinding whatever. As a rule more harm than good comes to the instrument. It is only in case of emergency that such heroic treatment should be resorted to. When cleaning the slide and inside of main tube great care must be taken not to break the wires. To clean the threads of leveling or tangent screws when working hard, use a stiff toothbrush to remove all dust, then apply a little oil, and work the screw in and out with alternate brushing to remove dirt and all oil until it moves perfectly free and smooth. Screws for the adjustment of cross hairs should not be strained any more than necessary to insure a firm seat; all straining of such screws beyond this simply impairs the accuracy of instrument and reliability of adjustment. When in the field always carry a Gossamer water-proof to put over the instrument in case of a shower or dust cloud. On reaching office, after use of instrument, dust it off generally with another fine brush; examine the centers and all other principal movements to see if they run perfectly free and easy, and oil them if necessary; also examine the adjustments. This will save expense and many hours of vexation in the field. In field use, an instrument has to be necessarily exposed to the heat of the sun, and to the action of dust and water; all of these, however, singly or combined, have a tendency to affect its accuracy and endurance. While good instruments are designed to guard against injuries resulting from exposure of this kind, yet glaring abuses, such as to allow it to stand for hours in the hot sun, etc., without a covering or shelter of some sort, may often lead to a permanent injury to its most vital parts. To preserve the finer qualities of an in- strument, viz., the telescope slide, the lenses, the edge of the gradua- tion and verniers, the centers, etc., any undue unequal expansion of the different parts should be prevented. A bag thrown over the in- strument when not in use, or any shelter that can be had, is to be recommended. While in use, an umbrella or screen held over it will insure greater permanency of its adjustments, and the results ob- tained will be more accurate and uniform than when carelessly exposed. To protect an instrument from the effects of salt water, a fine film of watch-oil rubbed over the exposed parts will often prevent the CARE OF INSTRUMENTS 29 appearance of oxyd. To remove such oxyd-spots as well as possible, apply some watch-oil and allow it to remain for a few hours, then rub dry with a soft piece of linen. To preserve the outer appearance of an instrument, never use anything for dusting except a fine camel's hair brush. To remove water and dust spots, first use the camel's hair brush, and then rub off with fine watch-oil, and wipe dry; to let the oil remain would tend to accumulate dust on the instrument. CARE OF THE CENTERS AND GRADUATIONS ,. If it is found that the centers do not revolve freely, as is often the case after exposure to extremes of temperature, take the instrument apart and proceed as follows: Take a fine camel's hair brush, and with it clean the graduation, the verniers and the inner part of the instrument, but do not rub the graduation, especially not its edge. Then take a stick of about the same taper as the inner center, wrap some wash-leather slightly soaked in fine oil around it, and clean the insides of the sockets as carefully as possible and then wrap a fresh piece without oil around the stick and clean dry. Proceed similarly with the centers and their flanges. Before applying fresh and pure watch-oil, care should be taken that not a particle of dust or other foreign matter is left, in the sock- ets, on the centers, or on the graduation. This caution having been taken, the fresh oil should be well distributed on all the bearing parts. It will be well to also examine the arm of the clamp screw of the circle and telescope axis, and if necessary clean by removing washer. After the instrument is thoroughly cleaned and oiled, the nuts and springs screwed back to a firm seat, the instrument must turn perfectly free and yield at the slightest touch of the hand. To remove dirt and oxyd that may have accumulated on the surface of a solid silver graduation, apply some fine watch-oil, and allow it to remain for a few hours; take a soft piece of old linen and slightly rub until dry, but without touching the edge of the gradua- tions. If, after cleaning, the solid silver surface should show alter- nately brighter spots, which would interfere somewhat with the accurate reading of the graduation, barely moisten the finger with vaseline and apply the same to the surface; then wipe the finger dry and lightly rub it once or twice around the graduation. Avoid touching the edges as much as possible. Such cleaning, however, must only be resorted to when absolutely necessary, and then only 3 o COAL MINE SURVEYING with the greatest care, as it is too apt to reduce the minuteness of the graduation, and spoil its fine appearance. If, after such cleaning, dirt and grease has accumulated on the inner edge of the graduation and verniers, gently wipe clean before restoring the vernier-plate to its place. Remember, also, that the centering of the graduations of the circle and verniers is a most delicate adjustment to make. These should never be unscrewed from their flanges by anybody except a maker. TELESCOPE LENSES As dust and moisture, as well as perspiration from the hands, will settle on the surface of the lenses of a telescope, it becomes necessary that they should be cleaned at times. A neglect to keep the lenses free from any film, scratches, etc., greatly impairs the clear sight through the telescope. To remove the dimness produced by such a film, proceed thus: Brush each lens carefully with a camel's hair brush, wipe gently with a clean piece of chamois leather moistened with alcohol, and wipe dry using a clean part of the chamois skin on every portion of the lens, to avoid grinding and scratching. When perfectly trans- parent brush again to remove any fiber that may adhere to the lens. The tubes in which the lenses fit should be brushed, and if damp should should be dried; this done, restore each lens to its original place as marked. To remove dampness in the main tube of the telescope, take out the eyepiece, cover the open end with cloth and leave the instrument in a dry room for some time. If an instrument has been exposed to a damp atmosphere, or water has penetrated the telescope, moisture may settle between the crown and flint glass of which the object glass is composed. If such is the case expose the instrument to the sun for a few hours, but if in the winter, leave it in a warm room some distance from the stove, the moisture will then generally evaporate. However, if not successful, unscrew the object glass from the telescope, and heat it slightly over a stove or open fire. If a film settles between these glasses nothing can be done except sending the instrument to the maker. The two glasses form one lens only and must not be disturbed, as upon their relation to each other the definition and achromaticity of the telescope depends. Much depends also on the stability, with which these lenses are mounted in their cell, as any looseness between them or the cell will affect the adjustment of line of collimation. CARE OF INSTRUMENTS 31 Of course, if at any time the object glass has been unscrewed from the telescope, this latter adjustment must again be verified before the instrument is used. When the object glass, or telescope is returned after the cleaning or cementing of its lenses, the cross-wire, spirit level, and vertical arc adjustments of the instrument will require a thorough verification before it should be used. In case the whole instrument has been sent to the maker, these adjustments are attended to by him. If the object glass has been cemented, the telescope should be watched for a year to see that there is no distortion of the image. If there is a distortion, it will indicate that the object glass has been too tightly fitted, of which fact the makers sKould be informed, as also whether after cementing the object glass the instrument retains its cross- wire adjustment the same as before. If the cross-wire adjust- ments have to be more frequently made than before the lenses were cemented, it indicates that the object glass is not tightly fitted to its cell; and if such is the case it should be returned and more tightly fitted, after a lapse of about ten or twelve months, when the cement will have sufficiently hardened to allow of a tighter fit. LUBRICATING An instrument used in a tropical or semi-tropical country, or during the warm season in a northern latitude, requires more fre- quent cleaning and oiling than in the more temperate climes and seasons; but so long as an instrument works well and the centers revolve freely, it is best not to disturb it. The centers of a transit should always be lubricated with fine watch- oil only, and after a careful cleaning; never apply fresh oil before thoroughly wiping off old grit and oil. Rendered marrow is a most excellent lubricant for instruments made of brass and the many kin- dred alloys of copper and tin. In the varying climes of our north- ern latitudes this lubricant becomes rigid in cold weather, and an instrument so treated will often become unmanageable in the field. Its application, particularly to the centers of a transit, is therefore restricted to the warmer zones. The use of watch-oil for the finer parts of an instrument, involving freedom of motion, is imperative in our latitudes. Many parts of an instrument, especially those whose metal com- positions are closely related to each other, may sometimes cause trouble if simply oiled. If they begin to fret and grind, but are other- 32 COAL MINE SURVEYING wise free from grit, etc., the judicious application of a little marrow may prove beneficial, but it should be cleaned off again as much as possible. The rack and pinion motion and the telescope clamp should always be greased with marrow, but the clamp, tangent and leveling screws, should receive as little of it as possible in the Northern States. Vaseline, not having as great a tendency to solidify under similar circumstances, may prove an excellent substitute for marrow, and may often be applied to level-centers, where watch-oil would not give the necessary rigidity in the use of the more ordinary instru- ments, but it must be renewed quite often. In the finer class of leveling instruments, the centers should be lubricated with oil only, as in transits. A great deal of annoyance is caused if the eyepiece or the object slide of the telescope move too freely in their tubes, requiring a re- focussing of the cross wires and object at every revolution of the telescope in altitude. If the eyepiece can be retained in its socket, with sufficient friction to keep it f ocussed to the cross wires, no matter how much it may wabble otherwise, this imperfection (in old instru- ments) will not lead to any inaccuracy, but if there is not sufficient friction to keep it focussed to the wires, a little rendered tallow or marrow applied to its bearing surfaces in most cases will remedy this evil. Wabbling in the object slide, however, leading to inaccuracy of collimation, or back-lash in its rack or pinion motion, can be remedied only by a maker; but if the object slide moves too freely in and out of its tube only, this may be remedied by applying a little tallow to the bearing parts of the rack and pinion, or by tightening the screw in the pinion-head. If not entirely successful, a thin disk made of parchment, or a thin leather washer, both greased with tallow, and inserted between the flanges of the pinion-head and its socket, will insure the desired result. These latter remarks apply to transit and level telescopes of the customary design. In telescopes, where the object glass is mounted permanently to the telescope tube, the eyepiece tube, containing the cross wires, becomes the slide with which to focus the object. Its motion must be in a line parallel to the optical axis. Any wabbling in this eyepiece slide would lead to inaccuracy in sighting through the telescope, hence it requires the most careful treatment on the part of the engineer. CARE OF INSTRUMENTS 33 LEVEL BUBBLES Spirit levels are very susceptible to the least change in tempera- ture, as will be readily seen by the difference in the length of its bubble in varying temperatures. Hence, to guard against inac- curacies from this source, it is necessary that the bubble should lengthen symmetrically from the center of its graduated scale (sup- posed to be put on by the maker), and that both of its ends should be read. Sufficient time must also be allowed for the bubble to settle before reading is made. The fluid ordinarily used for levels is pure alcohol, and requires, according to curvature, diameter and length of tube and length of bubble, from twenty seconds to one minute to attain its equilibrium. The composition fluid used in some levels for field instruments requires only from five to fifteen seconds of time; those filled with pure ether, a few seconds only. A great source of error in spirit levels, however, increasing with their greater sensitiveness, is occasioned by an unequal heating of the level-tube, as the bubble will always move toward the warmer spot or end, thereby imparting to the instrument an inaccurate position. This must be attributed to a changed condition in the adhesiveness of the fluid in the level-tube, and not to a change in the form of the tube itself. Therefore, to guard against inaccuracy re- sulting from sudden changes of temperature, a spirit level, while in use, should be protected from the sun, and no part of it or its mount- ing should ever be touched with bare fingers; neither should it be breathed upon, nor the face of the observer come too close to it. For this reason, in the finer instruments the mountings of some spirit- levels are cloth-finished, and if the levels are detachable they are provided with wooden handles, as the case may require, and glass covers are placed over them whenever deemed necessary. If at any time during the progress of field-work a spirit level has been improperly exposed, it is best to cover it with a cloth for from five to fifteen minutes, before proceeding with further work. Mounting Spirit Levels. To prevent any undue strain and change of curvature in spirit levels used in astronomical instruments, they are mounted by some makers in wyes and are protected from injury, or inaccuracy caused by the breath of the observer and other air currents, by a cover of glass placed over them. Such a mounting, while most suitable for such delicate levels, would, however, require 3 34 COAL MINE SURVEYING constant attention and expose a spirit level to breakage in field in- struments. To guard against this danger and to lessen the expense and weight, the spirit levels for field instruments are mounted in a brass tube; but owing to the difference existing in the expansion and contraction of glass and brass at different temperatures, a spirit-level so mounted may sometimes become loose, involving inaccuracy and unreliability of adjustment. Upon finding that the adjustment of a spirit level in an even tem- perature is not as stable as desirable, the level fastenings, tube, screws, etc., should be examined, to see if any of them are loose. If the trouble is in the screws, tighten them up; but if the spirit level can be shifted in its tube by a touch of the finger, take it apart; soften the plaster of Paris in water, and remove it with a sharp pointed stick of wood. Cautiously move the spirit level with your finger, at first only a trifle to and fro, increasing the length of stroke little by little, until it can be safely taken out without breaking. Clean thoroughly and then cut pieces of white paper, of the width of the radius of the tube, and somewhat shorter than the length of the spirit level, but longer than the opening in the brass tube, and insert these of sufficient quantity at the bottom of the brass tube, to fill up the space intervening between the glass and the brass tube. The uppermost layer of paper should, however, be so wide, as to envelop the spirit level up to the opening in the brass tube. Now insert the spirit level, taking care not to touch the glass ends that are sealed up, arid place the division or other marks, indicating where the level has been ground to a true curvature, uppermost in the brass tube. The level must be pushed in with sufficient friction to prevent slipping in the tube, yet not so tight as to cause a crack at a subsequent low temperature, as brass will contract more than glass. No part of the spirit level should touch any part of the metal tube. Now prepare some plaster of Paris with water, of the consis- tency of paste, and pour in at each end enough to fill up the space between the end-pieces and the glass, stirring it sufficiently to make a perfect contact by it and the glass and the brass, but leaving the spirit level ends exposed. Now put the level together, and adjust as described elsewhere. There are other causes, such as centers and flanges that have been bent by falls, etc., or that have been worn out unequal expansion or contraction in different temperatures of the metals employed in the construction of an instrument, or a non-symmetrical lengthening or shortening of the air-bubble at different temperatures all of CARE OF INSTRUMENTS 35 which, singly or combined, tend to impair the adjustment of spirit- levels on instruments. Being assured that the level is mounted as explained above, it is advisable not to meddle too frequently with the adjustment. Though it may appear to be out one day, it may be in perfect adjust- ment other days. It is the function of a spirit level to indicate the changes taking place in an instrument, so that the engineer may make proper allowance and apply his corrections, as the character of his work may require. The finer an instrument, the more sensitive the spirit levels must be, in order to admit of corrections to arrive at closer results. As a rule, a spirit level that does not indicate changes taking place in an instrument, is too insensitive for the character of the instrument, and in many cases entirely unfit for reasonably good work. REPLACING CROSS WIRES Remove the reticule frame and clean it of all foreign matter; put it on a sheet of white paper with tl^e cuts on its surface upper- most. Prepare a little shellac by dissolving it in the best alcohol and waiting until it is of the consistency of oil. From the spider's cocoon (those from a small black wood-spider preferred), which the engineer has prudently secured at some previous time, select two or three webs, each about 2 in. long and of the same appearance. Attach each end of these webs to a bit of paper or wood to act as weights, and immerse them in water for five or ten minutes. Remove one web from the water, and very gently pass it between the fore- finger and thumb nails, holding it vertically to remove any particles of moisture or dirt. Stretch the web carefully over two of the op- posite cuts in the reticule frame. Fasten one end by a drop of the shellac, dropped gently from a bit of pointed wood or the blade of a penknife. Wait a moment, for this drop of shellac to harden. See that the web is stretched tight across the frame, and apply another drop of the shellac to the opposite cut with its enclosed web. Wait several minutes before cutting off the two ends of the web, and then proceed in the same manner with the web which is to be placed at right angles to this one. One of the best spider-webs for this purpose is obtained from the cocoons of a species of spider found in Michigan. These threads are almost opaque, and not apt to relax their tightness if properly placed on the diaphragm, and as they retain their elasticity, they are preferable to platinum wires, which have a tendency to break, owing 3 6 COAL MINE SURVEYING to their great brittleness. The best spider- threads are those of which the spider makes its nest. These nests are yellowish-brown balls, which may be found hanging on shrubs, etc., in the late fall or early winter. The nest should be torn open and the eggs removed; if this is not done, the young spiders, when hatched, will eat the threads. The fibers next to the eggs are to be preferred on account of their fineness and darker color. As it is important to get the proper kind of spider-web, the following letter on this sub- ject from Prof. J. B. Davis, University of Michigan, Ann Arbor, Mich., is of interest: " The species of spider of which I send you cocoons is not difficult to find in Ann Arbor Lat. 42 26' N as far as my experience goes, and is numerous on Beaver Island, out in Lake Michigan about 46 N. at St. James. I have also always succeeded in hunting it in our Michigan woods, in places of concealment under bark of dead trees, in cracks and holes, about old stumps, logs, and the like. It is especially partial to painted woodwork. It roosts high the higher the gable the more numerous the cocoons; but it is also found on fences quite numerously, as I am led to think it is quiet rather than security this spider seeks. The body of the female is about three-fourths of an inch long, and nearly half an inch wide across the abdomen. The male is about the same length, but far slimmer. They are both entirely harmless. I never knew any one to get bitten by either, and many persons in my observation have had them freely crawling over their hands, face and body. They may be certainly gently handled without the least harm. They both (male and female) bear a plain escutcheon design on the back of the abdomen; female much the more beautiful in browns. Colors all brown and yellowish-brown. The cocoon is a snarl of webs, and is attached under ledges of window-sills, cornices, projections of gables, and the like partly sheltered places. The color of the threads you have is of a light corn-color, distinctly separating it from the white cotton-like cocoons so common everywhere. The threads are silky, not like cotton. Of late years I keep one or two nice cocoons where they can be reached. You know one can wrap them in a bit of paper and carry them in the pocket, or any such place, and they are always ready." ACCIDENTS AND PRECAUTIONS IN THE USE OF INSTRUMENTS It cannot be denied that instruments frequently meet with serious accidents which, with a little care on the part of the operator, could CARE OF INSTRUMENTS 37 be prevented. It certainly does not betoken proper care to leave it standing unguarded in a street, road, or pasture, or in close vicinity to blasting, or to expose it unnecessarily to the burning rays of the sun, or to dust, dampness, or rain at any time. Such carelessness must inevitably result in deterioration of the accuracy and efficiency, not to speak of the durability, of an instrument. It should be borne in mind that there are many parts of an instrument which, if once impaired, cannot be restored to their original efficiency. Tripods. Legs of tripods, if fitting too loose or too tight, and dull shoes are frequent sources of falls, and loose shoes tend to make an unsteady instrument. The test of the proper degree of the tightness of the legs is if the leg is raised to a horizontal position and left free, it should gradually sink to the ground. If it drops abruptly it is too loose; if it does not sink it is too tight. Mounting the Instrument. 'When taking an instrument from its box, it is not immaterial where and how to take hold of it. To lift it by the telescope, circles, standards, or wyes is improper, and while it may not be attended at once with any serious consequences, yet it may sometimes lead to some permanent injury, and it cer- tainly is aways fraught with danger to the permanency of the adjust- ments. In handling, it is always best to place the hand beneath the leveling base. When mounting an instrument on the screw of its tripod, 'or screw- ing any of its parts together, it is important to turn the part in the direction of unscrewing until it is perceived by a slight jar that the threads have come to the point where they enter; the motion may then be reversed, and the parts screwed together. To secure an even wear of tangent and micrometer screws, they should be used equally on all portions of their lengths. Carrying an instrument in cold weather into a warm room, without the protection of its box or bag, will cause a sudden exchange of air within the hollow spaces, and carry with it dust and other substances through the minutest openings. The vapor, also, that will thus con- dense on the metal surfaces, if it were not protected, will have a tendency to settle a film on exposed graduations, making them indistinct and difficult to read. Protection of Lenses. failure to protect the lenses of the eye- piece and object glass of a telescope, when not in actual use, from the effects of moisture, dust, etc., by the covers provided for them (eyepiece lid and cap) will result in a more frequent settling of a thin film, which, like the fatty substance left by the touch of the 38 COAL MINE SURVEYING fingers, greatly impairs the clearness of vision. That the too frequent cleaning of the lenses must in the course of time be detri- mental to their brilliant polish, and lead to a corresponding loss of transparency, so essential to the proper working of a good telescope, is apparent. Too much care cannot be taken to guard the lenses, and particularly the inner surfaces of the lenses comprising the objective, against any film that may settle on them. The ill effects of such a film are especially noticeable in high-powered telescopes of first- class geodetic and astronomical instruments. In short, it should be remembered that the slightest film, scratch, or dirt will, according to their nature and location, impair the sight through a telescope, and often render it unfit for accurate work. Glass Parts. The glass covers protecting the compass, arc, and verniers from exposure need very careful brushing and cleaning, the same as the lenses, as any scratch or film will impair their transpar- ency. If at any time the ground-glass shades should lose their pure whiteness, by either dirt or film, and will not act as illuminators of the verniers and graduation, take them out of their frames and simply wash them with soap and water. The Needle. To prevent loss of magnetism in the needle of instru- ments provided with a compass: when storing away, allow the needle to assume magnetic north and south; then, by means of the lifter, raise it from the center-point against the glass cover. If an instrument has met with a fall, bending centers and plates, etc., it should not be revolved any more, in order to preserve the graduations from still further injury, but recourse should be had at once to the nearest competent maker. Instrument Boxes. If the box or tripod should have become wet, they should be rubbed dry, and the varnish should be renewed whenever found wanting. Loose or detached resting-blocks in the instrument-box, or any looseness of the instrument in them, are very detrimental to the instrument and its adjustments. Cracks in the instrument-box, the absence of rubber cushions under it, worn-out straps and defective buckles, hinges, locks, and hooks, should never be tolerated, as the remedy is so easily applied by any mechanic. Such defects and imperfections are known to lead to injury of the instrument. Storing Instruments. The place where instruments are kept or stored away should be thoroughly dry and free from gases. The placing of fused chloride of calcium, or caustic lime, in an open vessel in the instrument-box is to be recommended where there is CARE OF INSTRUMENTS 39 dampness; and if the presence of sulphureted hydrogen is suspected, then, cotton saturated with vinegar of lead, placed in the box, will prove a preventive against the tarnishing of solid silver graduations. TRANSPORTATION or INSTRUMENTS During the progress of field work the more ordinary and portable transits and leveling instruments, etc., can generally be carried on their tripods for ease and dispatch. Nothing in the way of precise instructions, however, as to the best method of carrying an instru- ment, whether on the tripod, in the arm without the tripod, placing the hand beneath the leveling base, or in the box, can be suggested here. The nature of the ground, the surroundings, the size and weight, and the distance to be traveled over, and last but not least the fineness of the instrument, will dictate to the engineer the best means of conveying it from point to point in order to protect it from injury, and its adjustments from derangement. Carrying an instrument on its tripod without slightly clamping its principal motions, will wear out the centers. When carrying on its tripod, clamp telescope in the transit, when placed on a line with its centers and in the level when hanging down. Placing in the Box. When carrying an instrument in the box it is important that it be placed therein exactly in the position and manner designated by the maker. Therefore, upon receiving a new instrument, the first step should be to study its mode of packing, and if necessary a memorandum should be made for future guidance and pasted in the box. This will save time and vexation, as some of the boxes for field instruments must necessarily be crowded to be light and portable. Before placing an instrument with four leveling screws in its box, the foot-plate should be made parallel to the instrument proper, and then brought to a firm bearing by the leveling screws. The instru- ment must also be well screwed to the slide-board, if one is provided. Having put the instrument in the box in such a position, that no part of it will touch the sides, the principal motions are now to be checked by the clamp screws, to prevent motion and striking against the box. With instruments not standing erect in their boxes, but which are laid on their sides in resting places, padded with cloth, specially 'provided for that purpose, their principal motions must not be clamped until the instrument has been secured in a complete state of repose in these receptacles, so as to be entirely free from any strain. Care must be taken, too, that all of the detached parts of an I 40 COAL MINE SURVEYING instrument, as well as its accessories, are properly secured to their receptacles before shutting the box. Shipping. When shipping an instrument over a long distance it is commendable to fill the hollow space between it and its box with small soft cushions made of paper, or of excelsior or shavings wrapped in soft paper, .taking care not to scratch the metal surfaces, nor to bend exposed parts, nor to press against any adjusting screws. For greater safety in transportation by express, the instrument- box itself should always be packed in a pine- wood box one inch larger all around. For the ordinary size of field instrument the packing- case should be provided with a strong rope handle, which, like the strap of the instrument box, should pass over the top of the case and through holes in the sides, the knots being within the case and strongly secured. In cases where the gross weight of the entire package, as prepared for shipment in the above manner, exceeds 40 or 50 lb., then two men should handle it, and two strong rope handles, one at each end of the packing case, should be provided. In order to check jars and vibrations while en route, the loose space between the instrument box and the packing case is to be filled with dry and loose shavings. The cover bearing the directions should always be screwed on and marked in large black letters. The upper halves of the four sides also should have "care" and "keep dry" marked in large letters on them. These precautions are indispensable for safe conveyance while in the hands of inexperienced persons, as without them messengers will often carry them wrong side up. The tripod needs packing simply in a close-fitting box. If not placed in a box, it often happens that legs or shoes are broken off while en route, or that the tripod head becomes bent. Many hundreds of instruments, packed as explained above, have been shipped, travelling thousands of miles, over rough roads, on stages and on horseback; and the instances are so rare where one has become injured (and then only through gross carelessness), that this mode of packing must be regarded as the only proper one for conveying instruments of precision by express or other public carriers. Arriving at its destination, an instrument should not remain packed up with cushions, etc., any longer than necessary. The atmosphere in such boxes naturally must be close and often moist, and consequently has a tendency to produce the ill effects by moisture mentioned in preceding paragraphs. CHAPTER IV .ADJUSTMENT OF INSTRUMENTS NOTE. Abstracted from publications of the C. L. Berger Co. The mechanical and optical condition of instruments used in geodesy, and their adjustments, although satisfactory when they leave the maker's hand, are liable to become disturbed by use. It is therefore of vital importance that the person using an instrument should be perfectly familiar with its manipulations and adjustments. He should be able to test and correct the adjustments himself at any time, in order to save trouble and expense, as well as to possess a thorough knowledge of the condition of the instrument. It is evi- dent that if the character of an instrument is not properly under- stood or if the adjustments are considerably out, the benefit due to superior design and workmanship may be entirely lost. Under these circumstances an expensive instrument may be little better than one of lower grade. In the best types of modern instruments the principal parts are so arranged that they can be adjusted by the method of reversion. This method shows an existing error at double its actual amount, and renders its correction easy by taking one-half the apparent error. Thus errors of eccentricity and inaccuracy in the graduations are readily eliminated by reading opposite verniers and reversing the vernier plate 180 on the vertical center and taking the mean of the readings, and by repeating the measurement of an angle by changing the position of the limb so that the measurement will come on different parts of the graduation. The striding levels and levels mounted on a metal base are readily tested by revers- ing their position end for end. In the transit plate levels the adjustment is assured by turning the vernier plate 180. Errors of the line of collimation are detected or eliminated by reversing the telescope over the bearings, or through the standards, as the case may be. In short, an instrument, the important parts of which are not capable of reversing in one way or another, cannot be ex- amined quickly and accurately. 42 COAL MINE SURVEYING THE TRANSIT If the instrument is out of adjustment generally, the engineer will find it profitable to follow the makers in not completing each single adjustment at once, but rather bring the whole instrument to a nice adjustment by repeating the whole series. The Bubbles. After setting up, bring the two small levels each parallel to a line joining two of the opposing leveling screws. Bring both bubbles to the center of the level tubes, by means of the leveling screws. Now turn the instrument 180 in azimuth. If the small levels still have their bubbles in the center of their tubes, these levels are adjusted, and the circles are respectively as nearly horizontal and vertical as the maker intended them to be. If the bubbles, however, are not in the center of their tubes, then bring them half way back by means of the leveling screws, and the remaining half by means of the adjusting screw at the end of each of the level tubes. It may be necessary to repeat this adjustment several times, but when made, the instrument once leveled will have its small levels in the center of their tubes through an entire rotation of the circle. To Make the Adjustment for Parallax. This adjustment common to all telescopes used in surveying instruments is that of bringing the cross hairs to a sharp focus, at the same time with the object under examination. Point the telescope to the sky, and move the eyepiece until the cross hairs are sharp and distinct. Since the eye itself may have slightly accommodated itself to the eyepiece, test the adjustment by looking with the unaided eye at some distant point, and while still looking, bring the eyepiece of the telescope before the eye. If the cross hairs are sharp at the first glance, the adjustment is made. Now focus in the usual manner upon any object, bringing the cross hairs and image to a sharp focus by the rack-work alone. A point should remain bisected when the eye is moved from one side of the eyepiece to the other. To make the Vertical Cross Wire Perpendicular to the Plane of the Horizontal Axis. Bisect some point at the lower edge of the field of view of the telescope by means of the tangent screw and note whether it continues bisected by this cross line throughout its entire length when the telescope is moved in altitude. If it does not, and the point is to the right of the line in the upper part of the field, the adjustment is made by loosening the four capstan-headed screws, and rotating the reticule in the direction of a left-handed screw, ADJUSTMENT OF INSTRUMENTS 43 until the point remains bisected and then tighten all four adjusting screws. Again, bisect the point by means of the tangent screw. It should now remain bisected throughout the length of the cross wire, if not, this operation must be repeated. To Adjust the Vertical Wire. When that is to be alone adjusted in the field, it is usually done according to the following simple directions: Level up the instrument approximately and select two distant points in opposite directions, preferably in the same hori- zontal plane, such that the vertical cross line will bisect them both when the telescope is pointed upon one, and then the telescope is reversed on its horizontal axis. After bisecting the second point selected, revolve the instrument in azimuth and bisect the first point again by means of the tangent screw. Reverse the telescope on its horizontal axis again, and if the second point is now bisected the adjustment for collimation of the vertical wire is correct. If it is not bisected, move the vertical wire one-fourth of the distance between its present position and the point previously bisected. Again bisect the first point selected, reverse the telescope and find a new point precisely in the new line of sight of the telescope; these two points will now remain bisected when the instrument is pointed upon them in the manner described above, if the adjustment is correctly made. If the two points are not now both bisected, the adjustment must be repeated until this be the case. To Determine Whether the Standards are of the Same Height. Suspend a plumb bob by means of a long cord from a height say of from 30 to 40 ft. The plumb bob may swing in a bucket of water to keep it steady. (Instead of a plumb line the reflection of a church spire or edge of a tall building or any other convenient object may be viewed in a bucket of water.) Level the instrument carefully, and point upon the plumb line at its base. If the plumb line remains bisected throughout its entire length when the telescope is moved in altitude, and then the telescope reversed and again made to bisect the line throughout its length from its base upward, the adjustment is correct. Otherwise make the adjustment by means of the capstan-headed screw directly under one of the telescope wyes. Loosen the screws in the pivot caps and turn the vertical adjusting screw right handed to raise the wye bearing one-quarter of the error to be corrected. If the telescope's axis is already too high, the vertical adjusting screw should be loosened a little more than needed and then by the screws of the pivot cap the wye bearing should be lowered until it just 44 COAL MINE SURVEYING touches the vertical adjusting screw. The screws of the pivot cap must now again be loosened and the wye bearing raised by a right- hand turn of the vertical adjusting screw, as explained above, until the telescope's axis is in the correct position. If this is not done the adjustable bearing is likely to stick and not rest on the adjust- ing screw, thus causing liability to derangement. The screws in the pivot cap should then be turned down just enough to prevent loose- ness in the bearings. Instead of using a plumb line a simpler method having the advan- tage of not requiring the instrument to be leveled up carefully is as follows: Set up the instrument as near as may be convenient to a building, say about 20 ft., in order to get as high an altitude as pos- sible. Level up only approximately, clamp and bisect a point at the base by the tangent screw. Then elevate the telescope and find a well-defined object as high as possible, only using the telescope's horizontal axis. Now reverse telescope and move instrument on its vertical center, again clamp, and bi-sect the point at the base. If when the telescope is elevated it bi-sects the high object selected the adjustment is correct. If it does not, proceed as described in the above method. To Adjust the Level to the Line of Collimation of the Horizontal Wire. One method is to use a sheet of water, or where that is not available, two stakes which are driven with their surfaces in the same level plane. Level up the transit half-way between two points lying nearly in a horizontal line, and say 300 ft. apart. Drive a stake at one of these points, place the rod on it and take a reading, first bringing the bubble to the middle of its tube. Point the telescope in the opposite direction, again bring the bubble to the middle of its tube, and drive a second stake at the second point selected until the rod held upon the second stake gives the same reading as when held upon the first stake. The tops of these two stakes now lie in the same level line. Take up the transit and set it outside in line, as near as it can be focussed on the first stake and level up. Now read the rod upon the first stake with the bubble in the center and then upon the second. If the two readings agree, and the bubble is in the middle of its tube, the adjustment is correct. If the two readings do not agree, then by means of the telescope's tangent screw elevate or depress the telescope the amount required until the horizontal wire reads the same on the distant rod. Next refocus on the near rod, take a read- ing, then focus on the distant rod and see if the readings are the same, ADJUSTMENT OF INSTRUMENTS 45 if not, by means of the tangent screw again make the horizontal wire read the same as on the near rod. Repeat this operation until both rods read the same. Now with the horizontal wire bisecting the distant reading make the adjustment of the level by its capstan- headed nuts until the bubble is in the middle of its tube when the level will be parallel to the line of collimation. THE LEVEL The Telescope. After the engineer has set up the instrument and adjusted the eyepiece for parallax, as described under the engineer's transit, the horizontal cross wire had better be made to lie in the plane of the azimuthal rotation of the instrument. This may be accomplished by rotating the reticule, after loosening the capstan- headed screws, until a point remains bisected throughout the length of the wire when the telescope is moved in azimuth. In making this adjustment, the level tube is to be kept directly beneath the telescope tube. When made, the small set-screw attached to one of the wyes may be set so that by simply bringing the projecting pin from the telescope against it, the cross wires will be respectively parallel and perpendicular to the motion of the telescope in azimuth. The first collimating of the telescope may be made using an edge of some building, or any profile which is vertical. Make the vertical cross wire tangent to any such profile, and then turn the telescope halfway round in its wyes. If the vertical cross wire is still tangent to the edge selected, the vertical cross wire is collimated. To Make the Adjustment of the Horizontal Wire. Select some horizontal line, and cause the horizontal cross wire to be brought tangent to it. Again rotate the telescope halfway round in its wyes, and if the horizontal cross wire is still tangent to the edge selected, the horizontal cross wire is collimated. Having adjusted the two wires separately in this manner, select some well-defined point which the cross wires are made to bisect. Now rotate the telescope halfway round in its wyes. If the point is still bisected, the telescope is collimated. A very excellent mark to use is the intersection of the cross wires of a transit instrument using same as a collimator. To Center the Eyepiece. This is done by moving the opposite screws in the same direction until a distant object under observation is without the appearance of a rise or fall throughout an entire rota- tion of the telescope in its wyes. The telescope is now adjusted. 46 COAL MINE SURVEYING To Adjust the Spirit Level to the Telescope. Bring the level bar over two of the leveling screws, focus the telescope upon some object about 300 ft. distant, and put on the sun-shade. These precautions are necessary to a nice adjustment of the level tube. Throw open the two arms which hold the telescope down in its wyes, and care- fully level the instrument over the two level screws parallel to the telescope. Lift the telescope out of its wyes, turn it end for end and carefully replace it. If the level tube is adjusted, the level will indi- cate the same reading as before. If it does not, correct half the devia- tion by the two leveling screws and the remainder by moving the level tube vertically by means of the two adjusting nuts which secure the level tube to the telescope tube at its eyepiece end. Loosen the upper nut with an adjusting pin, and then raise or lower the lower nut as the case requires, and finally clamp that end of the level tube by bringing home the upper nut. This adjustment may require several repetitions before it is perfect. To Make the Lateral Adjustment of the Spirit Level. The level is now to be adjusted so that its axis may be parallel to the axis of the telescope. Rotate the telescope about 20 in its wyes, and note whether the level bubble has the same reading as when the bubble' was under the telescope. If it has, this adjustment is made. If it has not the same reading, move the end of the level tube nearest the object glass in a horizontal direction, when the telescope is in its proper position, by means of the two small horizontal capstan- headed screws which secure that end of the level to the telescope tube. If the level bubble goes to the object-glass end when that end is to the engineer's right hand, upon rotating the telescope level toward him, then these screws are to be turned in the direction of a left-handed screw, as the engineer sees them, and vice versa. This accomplished the vertical adjustment of the spirit level for parallel- ism with the line of collimation of the horizontal wire must now again be verified. To Make the Adjustment of the Level Bar. Level the instrument carefully over two of its leveling screws, the other two being set as nearly level as may be; turn the instrument 180 in azimuth, and if the level indicates the same inclination, the level bar is adjusted. If the level bubble indicates a change of inclination of the telescope in turning 180, correct half the amount of the change by the two level screws, and the remainder by the two capstan-headed nuts at the end of the level bar. Turn both nuts in the same direction, an equal part of a revolution, starting that nut first which is in the direction ADJUSTMENT OF INSTRUMENTS 47 of the desired movement of the level bar. Many engineers consider this adjustment of little importance, preferring to bring the level bubble in the middle of its tube at each sight by means of the leveling screws alone, rather than to give any great consideration to this adjustment, should it require to be made. To Adjust the Horizontal Wire so that the Line of Sight will be Parallel to the Spirit Level. To make the adjustment with the stakes, set up the level halfway between two points lying very nearly in a horizontal line, and say 300 ft. apart. Drive a stake at one of these points, place the rod on it and take a reading, first bringing the bubble to the middle of its tube. Point the telescope in the opposite direction, again bring the bubble to the middle of its tube, and drive a second stake at the second point selected until the rod held upon the second stake gives the same reading as when held upon the first stake. The tops of these two stakes now lie in the same level line. Take up the level and set it outside in line as near as it can be focussed on the first stake and level up. Now read the rod upon the first stake, and then upon the second. If the two readings agree, and the bubble is in the middle of its tube, the collimation is correct. If the two readings do not agree, change the horizontal wire to read the same on the distant rod by means of the capstan-headed screws near the eyepiece in the inverting telescope and furthest from the eyepiece in the erecting telescope. Refocus on the nearest rod, take a reading, then focus on the distant rod and again, by means of the capstan-headed adjusting screws, make the horizontal wire read the same. Repeat this operation until both rods read the same, with the bubble in the middle of its tube. CHAPTER V ORGANIZING AND EQUIPPING THE FIELD PARTY The mine surveying party varies widely according to the practice of the different companies and in different parts of the country. The party may be made up of anywhere from two to four or five men. Occasionally, the engineer is called upon to do general surveys with only one assistant, but this is one of the most flagrant examples of lack of economy that it is possible to conceive. However, the two- man party is not without its uses, as for instance, in doing rough room sighting and in leveling; two men are all that can ordinarily work to advantage on such work as this, and it is unnecessary to provide more. The three-man party makes a well-balanced and efficient corps. For general surveying it is the most economical and no doubt the one in most general use. It consists of the transit man, and two chainmen or backsight and foresight as they are sometimes called. With a rapid instrumentman in charge, there will be little delay in such a party as this, each man having practically about all he can do to keep up his end of the work. Occasionally, where greater speed is necessary, as well as more detail, a four- or even five-man party is used. Such a corps, how- ever, is usually split into two divisions. Thus, one section, including the chief of the party, takes the lead, establishing the stations, meas- uring the distances, and taking the neccessary side notes. The second section, which is the transit party, follows, turning the various angles, and also, as a rule, measuring the distances as a check on the work of the first party. An organization such as this has obvious advantages over the smaller party. Thus the transitman can confine his entire attention to his instrument, which will do much to eliminate the inaccuracies in this work; the possibilities for error are greatly enlarged where the transitman is obliged to divide his attention between his instru- ment and directing the work of the other members of the party; particularly is this so where his assistants are untrained. The larger party is also able to cover the work in greater detail. On the other 48 ORGANIZING AND EQUIPPING THE FIELD PARTY 49 hand, a corps of this size is liable to be unwieldly and is a rather cumbersome proposition to handle underground; it is obviously less economical than the three-man party. The five-man party is confined more particularly to the anthracite fields, where the conditions vary widely from the ordinary bituminous practice. The methods of the Lehigh Valley Coal Co. were de- scribed in the Engineering and Mining Journal as follows: A mine-surveying corps is generally composed of five men, back- sight, foresight, second-noteman, first-noteman and transitman, the latter being in charge of the party. The backsight carries a single rod, transit plumb-bob, an extra supply of bob cord and a two- quart can of oil. His duties are to help the second-noteman orient or "set up" the transit over the "spot" established by suspending the bob from the station. This is the temporary or trial set-up. The backsight then inserts his rod into the station hole suspending the bob over the transit-head point on the telescope, while the transit- man by means of the shifting plate permanently orients the transit. The foresight carries a single rod with a cast-iron bob, paint can and brush. He selects the most advantageous position for each station, both as to extension and good roof, sounding the top rock with his rod or T-drill. It is also the foresight's duty to help the second-noteman measure roof distance and record seam sections, besides giving sight to height of instrument for vertical angle, and painting the station number on the roof near the station. The second-noteman is provided with an 8- or loft, measuring pole which he uses to estimate the offsets at all ribs and intermediate points. The first-noteman acts as assistant transitman and records such notes, other than transit observations as are required. While the backsight and second-noteman are setting up the instrument, the transitman looks up his references and backsight course, and records at least some of the notes for the section connected with the previous survey. Chief of the Party. By this term is meant the man in charge of a four- or five-man corps. The first qualification of such a man is a broad underground engineering experience. It is essential that he be thoroughly familiar with idiosyncrasies of the underground workings, so that he will be able to judge promptly and accurately the best method of procedure in the face of the unprecedented obstacles which are always arising on mine work. The chief of the party leads the way, accompanied by one or two chainmen. It is preferable that one of these latter be a workman 4 5 o COAL MINE SURVEYING in that particular mine or section of the mine, so that he will be perfectly familiar with the workings and able to give the chief any information he may require. The chief proceeds with his party, establishing the stations at the most advantageous points, to insure the greatest rapidity in covering the ground. This party also usually measures the distances between stations and takes the side notes. It is possible to exercise a great deal of ingenuity in the location of the stations so as to accelerate the work, as for instance, it is clear that these should be as far apart as practicable, so as to insure the minimum number of setups of the instrument. Transitman. It is becoming difficult in modern times to obtain good, efficient and reliable men on instrument work in the mines. Underground work is naturally not attractive to the average young engineer, although when once broken in he usually prefers to be inside during extremes of weather, either hot or cold. However, the work is more or less underpaid, considering the qualifications demanded, and as a rule the engineer scarcely becomes proficient on his work till he is either advanced into the operating department or branches out into some other line. It is desirable, but by no means necessary, that the transitman be a college graduate, although, as a matter of fact, the practical man who has fought his way up by hard knocks will have a certain ad- vantage around the mines. The most essential qualifications of a good instrumentman are experience and an unlimited patience. While it is a comparatively simple matter to learn how to run a transit and read the vernier, no one can become really proficient and accurate without long experience. In fact, it might be said that there is a great deal of intuition about running an instrument on mine work. The experienced transitman is instinctively and per- haps unknowingly applying continual little checks and tests to his instrument, his work and himself, that perhaps while unimportant in themselves, when all combined, they determine the real character of the man's work. As his name implies, the transitman handles the instrument work of the party exclusively. He carries (or at least should carry) his instrument, and is responsible for its condition. Upon him and the head chainman or foresight depends the entire speed of the party; if the roof is hard so that the foresightman is delayed in getting in the new stations, the party may be obliged to wait on him, but as a rule, unless the instrumentman is very rapid, the reverse is true. In the five-man party the transitman is relieved of a great deal of ORGANIZING AND EQUIPPING THE FIELD PARTY 51 responsibility and is thus able to give the actual instrument work closer attention. But in the three-man party the necessity of direct- ing the location of the new stations, assisting with, and in fact quite often doing the chaining himself, as well as taking the side notes and providing ways and means for overcoming an unending series of unexpected contingencies, devolves on the instrumentman. They are apt to have a serious effect upon the accuracy of his work, especially if he is of an irascible disposition. Chainman and Backsight. The embryo transitman must always serve an apprenticeship on chain and sight work. He may be either an ambitious young chap around the mine, or a recent graduate from a mining school. The head chainman on the three-man party should be an active intelligent man and one who can be relied upon to hold the tape accurately. The brunt of the work usually falls upon him. He must go ahead establishing the new stations, raising intervening curtains, and exercise care and judgment in selecting the location of the stations. Unless he works rapidly the transitman will have the backsight taken before the foresight is ready. The head chain is favored, however, in many little ways, such as being "permitted" to carry the instrument occasionally, and also practise in setting it up during intervals when the party is waiting the passage of a trip or some other contingency. The rear chainman or backsight's duty consists only of following the party and giving an occasional backsight. CHAPTER VI ENTRY SURVEYING Picking up the Starting Stations. Having the party finally organized they proceed to the entry in the mine where their work is to start. The transitman or chief of the party refers to the notes of the last survey in this entry which may be either in the current book for that mine, or the one preceding. The party then proceeds in the entry to the last two stations of the previous survey, these being located by their proximity to certain rooms, cross cuts, or side entries, as shown in the side notes of the previous survey. Thus according to the side notes the next to last station may be 18 ft outside of room No. 32, and the last station 41 ft. inside of the second cross cut inside of room No. 32. The stations are further checked up by the rights and lefts according to the side notes. Occasionally where heavy timbering is being done a station may be shifted 2 or 3 ft. from its original location, and yet to all appearances be the same. Such a contingency does not happen often without effecting the distance between stations, so that checking this will usually suffice to prove that they are intact. In exceptionally bad ground, however, it is well to set up the instrument at the next to last station and turn the last angle of the previous survey to insure complete accuracy. Setting up the Transit. There are two ways of setting up the instrument on mine work, either directly under the station or by plumbing down from the station and establishing a point accurately below it and then setting up over this point. When using this latter method, it is the duty of the foresight to set the point on the floor while he is giving the sight on his station. This method is slower than setting up directly under the station and is more liable to inaccuracies; it is not to be recommended. Setting up under a station appears to the beginner as an exceed- ingly difficult, if not hopeless, task. However, a little experience with this method soon makes a man proficient at it, and, if he expects to follow mining work, he will do well to master this in the beginning. When setting up over a point, it happens quite often that in moving around and setting the transit leg, the point established on the floor is disturbed; when this occurs, it is necessary to pull the transit up 52 ENTRY SURVEYING 53 and reset the point. Sometimes, after the instrument is entirely set up, it may be thought that the point has been moved when it really has not. In addition to this, when setting up under the sta- tion, the instrumentman has both the point and the bubbles directly under observation all the time, whereas, in setting up over, he must either have two lights or take the one out of his cap and put it down to the plumb bob to see how his center is. When setting up under the station, the instrumentman first hangs his plumb bob in the station, having the point at about the height which he wishes to set the instrument The tripod plate is then brought as nearly horizontal as it is possible to judge by the eye. In doing this, it will be found that the instrument as a whole has been moved to one side from the station. This is where the difficulty arises in setting up under the station. Leveling up always displaces the point and, vice versa, in getting under the point, the instrument is thrown out of level. It is, therefore, necessarily a cut-and-try procedure. With a little experience, however, a man soon becomes remarkably adept. In setting up under the station, it is, of course, necessary that the instrument be provided with a point on the telescope exactly over the theoretical center; nearly all mining transits now have such a point. This will, of course, only be over the exact center when both the horizontal plate and telescope of the instrument are exactly level. The first time the instrument is leveled up, the telescope bubble should also be leveled at the same time, and then clamped securely in place. After that, it is only necessary to level with the lower bubbles. When the instrument has been brought within about half an inch of the exact point, the remainder can be gained by loosening the lower level screws and shifting the head bodily. The new transitman is very prone to waste time in unnecessary accuracy in setting up the instrument. On the other hand, he may be lacking in accuracy when same is essential, and it is well for him to investigate just what refinement is necessary along this line. Thus, for instance, in a sight 100 tt. long, an error in reading of i min. means a difference of .029 ft., or about f of an inch; in a sight 50 ft. long, i min. amounts to .0125 ft., or about A of an inch. With a sight 25 ft. in length, as may occasionally occur in a very crooked entry, or in taking 16 \ 7 S6ff 15 Roll WIDMHl ^" 16 462 83.90 ,24' ft'* 9 463 84.51 8 \ 10 ' 13 00 14 \ 8 82 I2\I2 26' 60 II \I2 75 & I3\IO 42 IS\IO 70 !j M 10 \ 12 55 10 \ 53 If 12 \IO 30 \I2 40 10 \I2 25 8 'IS 22 12 \IO \ 20 10 \I2 10 ia\i2 450 Feb.l.li W8 ffoss Vein 6 455 ct) Perry] & Smith 1 a b COM. AOS FIG. 22. METHOD OF TAKING SIDENOTES IN THE ANTHRACITE REGIONS. The notes in (b~), Fig. 22, indicate a roll or fault from station 455 + 53 to + 88 along left rib. Also a roll in the face dipping 16 and in a diagonal direction from right to left, and indicated as a down- throw. The transit, after set-up is satisfactory, is sighted to the backsight station, and then the new station is observed and readings recorded as shown in the accompanying table: KEEPING SURVEY NOTES 69 Remarks ' : : : aj : : si . . bfl . . ,D ;|i if-i 1] ! be ! ! rt ! ! u : HH ' ' M ' ' M TE REGIONS 8 i I flS Lj ^ j IO O tO IO H IO O }? > 5 1 1 : + + ; ;+ : T + (in : : : : p RECORDING U H c" ! ; ! ; ! J2 o H H H TS B . " " : in ' ' tn ' in o 3 1 s 1 ~- is> i~3'8 !ft I w OO ' vO vo co to to n 35 R6 L4 H < 31.20 = T+80&9I* XCL +80 V5L7+84 \96 Rm*8Rt + 92.10=$ + 142 & 153 -t >n,*9 in 10' + 153 R t.7R2L7+ 149.30 =/ + 165 & 174) c/ +174 Ri LS+192-b 6L4 face Wkg. 13-614 IZ' '45 NI24BL N 13 'E 25.01 000 614 -/Vs. 102 30 102 50 S 7730 S77E +5 Cor f( 5L4 +20 = face R5 LB Wkg. 614-328 282 31 N7729 W N78W 18224 0SO 328 -317 282 29 N773IW Tie +00l' Vol.420 RI8 i-Pts. I9230 SI 2 SOW s/s'w + 15 RIO L S+2SRI3L 5 facvWkcj *- 192 30 S 12 SOW S/3 '[is symbol for station Cow. AM FIG. 23. THE CONSOLIDATION COAL CO.'S METHOD OF KEEPING MINE-SURVEY NOTES. measured and recorded. In the third column the magnetic bearing of the line connecting the two stations is recorded; this is worked out during spare moments in the mine and is obtained by deducting 33^ 55' from 360 = s. Readings between o and 90 are direct courses; between 90 and 180 are deducted from 180; between KEEPING SURVEY NOTES 71 180 and 270 deduct 180, and between 270 and 360 are deducted from 360. The differences are the magnetic courses for correspond- ing quadrants. In the fourth column for stations 450-462 will be noted ~T~~O r This indicates that the vertical angle -f- 5 15' was read at 1.54 ft. above H. I. (hight of instrument), and the corrections are ap- plied in the office work for calculating the correct "difference in elevation." This is obtained in the following manner: The cosine of 5 15' times the tape distance 83.90 equals horizontal distance 83.55 ft-> and the sine times the tape distance equals 7.68 ft., the vertical distance, but as the angle was measured 1.54 ft. above H. I. the true distance in elevation is 7.68 1.54 = 6.14 ft. Similarly a correction of i ft. is necessary for difference in elevation for sta- tions 401-464, where the angle was measured i ft. below H. I. The sine for the distance and angle equals 5.73 ft., therefore the true difference in elevation is 5.73 + i.o = 6.73 ft. The algebraic FIG. 24. PLOTTED NOTES SHOWN IN FIG. 22. sign for these corrections represents the field operation and is the reverse of the algebraic correction. The methods of recording sidenotes vary widely in all parts of the country and even in different mines in the same district. The Consolidation Coal Co.'s method of recording sidenotes was described in Coal Age as follows: In locating the various features of the mine work, sidenotes are taken from the established line of sight. The page of survey notes shown in Fig. 23 demonstrates this more clearly. It will be noted from these records that sights, or courses, are always checked between stations in order to make sure that the stations still occupy the same positions they did when they were set and the readings taken; also to catch up the possibility of an error being made when the stations were set. The accompanying Fig. 24 shows the entry plotted from these notes. At the face the date of the survey is marked to show the position the heading occupied at that time. 7- 1 COAL MINE SURVEYING LEVEL NOTES The illustration, Fig. 25, shows the most approved method of keep- ing level notes. The notes are divided into five columns, the first being for the station numbers, the second "B. S." for the back- sight, the third "H. I." the hight of instrument, the fourth, "F. S." the foresight, and the fifth, the elevation. FIG. 25. SKETCH SHOWING THE CUSTOMARY METHOD OF RECORDING MINE LEVEL NOTES. Let it be assumed that instructions have been issued to extend the levels in the i$th South entry into the face, no special data being required, just the general elevations incident to the ordinary leveling process. The engineer refers to the notes of the last levels and finds that they were concluded on station 1517. He accordingly proceeds in the entry, locates the required station and, after assur- ing himself in every possible way that it has not been disturbed, he is ready to proceed with the new work. Before starting he carefully arranges the headings in his notebook KEEPING SURVEY NOTES 73 as shown. Too much importance cannot be laid on the necessity for careful references and cross references of all kinds. First, the "Levels in i5th South" is of course essential to show where the work is performed. Next it is well to note the personnel of the party as "Evans, instrument" and "Boggs, rod." One of the chief reasons for giving such close attention to this matter is that grave questions may at times hinge on the accuracy with which the engineer's work has been performed. In all organizations of any importance, there are always men who establish a record for accuracy and con- scientious work, and it is to be regretted that there are some just the opposite. Obviously, therefore, it is often a matter of great importance who the work was done by. After setting down the date, the engineer then proceeds f to note carefully the initial or starting point for his work, which, in this case, is station 1517, or as noted: "Reversed rod on Sta. 1517, see bk. 9, p. 1 24." This data should be carefully noted for the reason that should subsequent work show the elevation for this Sta. 1517 to be in error, it is, of course, essential that this be known in order to make the proper corrections in the succeeding work. The ele- vation of Sta. 1517 as obtained from bk. 9, p. 124 was found to be 1321.17, and this is accordingly set down in the column under ele- vation. The instrument is then set up and a reversed rod reading taken on the station. This idea of establishing "bench marks" on the mine stations in the roof varies entirely from anything practised on surface work. The reason for this is that it is exceedingly difficult to get any re- liable permanent points on the bottom which are not in danger of being disturbed. The bottom in a live mine is more or less con- stantly on the move, due to varying roof loads, and is also liable to be taken up in order to gain more head room. So it has become the ac- cepted practice to establish all permanent reference pointsin the roof. While it is customary to add all backsights to the elevation in order to obtain the height of instrument, this operation is, of course, the opposite where a reversed rod reading is used, the backsight being subtracted from the elevation instead of added. With the reversed rod reading of minus 1.13, as noted, the height of instrument there- fore becomes 1320.04. The rodman then moves as far ahead as the levelman can see him, which, in this case, is at Room 28. For convenience, and as a possible future check, he holds the rod on the point of frog of this room. The reading at this point is found to be 4.19, which indicates that the new station is that distance beneath 74 COAL MINE SURVEYING the height of the instrument, and, accordingly, the difference be- tween the two gives the new elevation 15.85. In keeping level notes, it is not the practice to carry the hundreds of feet along in either the height of instrument or elevation column, and these are accord- ingly omitted except where a change occurs as from 1300 to 1200 as is 'noted. The instrumentman now moves his instrument up ahead of the rod as far as he can see, and, taking a backsight, ob- tains a reading of 0.53, which means that his instrument is this amount above the station and the new height of instrument is, therefore, 16.38. And so the operation is continued until we come to the face of the entry, at which point another bench mark is taken on Sta. 1521 for use in making future extensions. As in the previous case, this is a reversed rod reading, so that instead of subtracting the foresight, as we ordinarily do, this is added. Now we arrive at the method of balancing the leveling notes. A little consideration of the level notes will show the reader that the difference between all the foresights added together, and all the backsights, must give the difference in elevation between the starting point and the concluding stations. But the reversed rod readings introduce complications in this method; however, since these are confined entirely to the initial and concluding stations of the survey, we may disregard them and confine our check to the intervening stations. Accordingly, adding up the backsights and omitting those having a circle (reversed rod readings), we get 2.72, and doing the same with the foresights, we obtain 25.64, the difference between these two being 22.92. Now, subtracting the difference between the second elevation from each end. that is, 1315.85 and 1292.93, we obtain a perfect check, 22.92. Leveling practice of the Consolidation Coal Co. was described in Coal Age as follows: All elevations on the inside are run by precise levels starting from benchmarks on the outside established from U. S. G. S. benchmarks. The readings are taken on the bottom of the seam every 100 ft. and in some localities closer, depending upon the irregularity of the coal. Every six months the levels are advanced to the breasts of the working places, no elevations being taken in rooms except for special purposes. Bench marks are also established ahead, usually being placed on a station or pointer in the roof and B. M. marked on the rib opposite. The method of recording inside level notes is shown in Fig. 26. KEEPING SURVEY NOTES 75 CHAPTER VIII SOME PROBLEMS IN SURVEYING The following problems have been selected from among those submitted to Coal Age in the past two years; they represent a typical assortment of the many computations that the colliery engineer is apt to encounter. Problem i. Given the data shown in Fig. 27 and it is desired to know: (a) The length of a proposed incline AB (b) The depth of a vertical shaft EC (c) The distance DC from the foot of the shaft to the mouth of the drift in the lower seam. According to the law of sines we know that: The ratio of any two sides of a triangle is equal to the ratio of the sines of the opposite angles. In the triangle ADB, designate the angles by the large letters A, D and B, respectively; then: Lower Sean FIG. 27. By the law of sines A = 20 D =18030 =150 B = 3020 = 10 AB AD sin D sin B sin 10 But since the sine of an angle is equal to the sine-of its supplement and vice versa, and AD = 100 AB _ sin 30 _ 0.5 100 ~ The length of the incline is then sin 10 0.17365 '-=287.93 76 SOME PROBLEMS IN SURVEYING 77 The depth of the vertical shaft EC is now easily calculated from the right triangle ABC; thus: BC = AB X sin A = 287.93 X sin 20 = 287.93 X 0.34202 = 98.48 //. The distance DC, from the mouth of the drift to the point where the upraise should be started, can then be calculated from the triangle ABC by subtracting 100 from the distance AC thus found, as follows: DC = AB cos 20 100 = 287.93 X 0.9397 ~~ I0 = I 7-57 ft- or, directly from the triangle DBC, thus: DC = BC = 170.57 /*. tan 30 0.57735 Problem 2. (a) If the course of a main entry is due north, what is the course of a face entry turned off to the right, at an angle of FIG. 28. PLAN OF MAIN, FACE AND BUTT ENTRIES, AND DIAGRAM SHOWING THE CORRESPONDING COURSES. 80 ? (b) What is the course of a butt entry turned off the face entry to the right, at an angle of 90? (c) What is the course of a room turned off the butt entry, at an angle of 80 to the right? (a) In Fig. 28 the general position and direction of the main en- tries, face entries, butt entries and the rooms turned off the butt entries are shown. The course of the main entries being due north and the face entries being turned to the right an angle of 80, the course of these entries will lie in the northeast quadrant, as shown on the right of the figure, and its bearing is N 80 E. (b) The butt entries being turned 90, again, to the right, the azimuth of their course is 80 + 90 = 170. Since this azimuth lies 7 8 COAL MINE SURVEYING between 90 and 180, the course of the butt entries lies in the southeast quadrant. All bearings in the southeast and southwest quadrants being estimated from the south end of the meridian, the angle of bearing, in this case, is found by subtracting the azimuth from 180. Thus, 180 170 = 10. The bearing of the butt entries is then S 10 E. (c) The rooms being turned 80 to the right of the butt entry, the azimuth of the rooms is 170+80 = 250. Since this angle lies between 180 and 270, the course of the rooms lies in the southwest quadrant, and the angle of bearing measured from the south end of the meridian is 250 180 = 70. The course of the rooms is, therefore, S 70 W. Problem 3. An approximate method of measuring across a stream by use of a transit and tape but without reference to a book of tables. First Method. Where it is possible to cross over the stream, the following method may be used, which will give approximate results: Referring to Fig. 29, set up the instrument at A and sight to a point B. Then, by means of the 3, 4, 5 method, often called the 3, 7, 12 method, set off the right angle OBT. To do this, first line in the point 0, on the line AB, with the instrument, making the distance OB 3 ft. or any multiple thereof, and place a surveying pin at O. With .B as a center and a radius of 4 ft., describe an arc; 3 c FIG. 29. METHOD OF MEASURING DISTANCE ACROSS A RIVER. and with O as a center and a radius of 5 ft., describe another arc intersecting the first at T. The angle OBT will then be a right angle. By the 3, 7, 12 method, the end of the tape is fastened at 0, and the tape is then carried around the triangle OBT and back to 0. The distance around the triangle OBTO is 12 ft. Now, holding the end and the i2-ft. mark at 0, with the 3-ft. mark at B, pull out the tape with a pin at the y-ft. mark, which will establish the point T, making the angle OBT a right angle. With the instrument at A, turn off the angle BAG equal to 5 43', SOME PROBLEMS IN SURVEYING 79 and line in the point C on the line BC. Now, since the tangent of 5 43 ' is o.i, the distance AB will be ten times the distance BC. Thus, if the distance BC equals 50 ft., AC will be 10 X 50 = 500 ft. Second Method. When it is not possible to cross to the opposite side of the stream, the following method can be used: Referring to Fig. 30, establish the line CD more or less parallel to the stream, FIG. 30. ANOTHER METHOD OF MEASURING ACROSS A STREAM. and another line EF parallel to the first, and at any distance AO from it. Now, select a well-defined point or object, B, on the opposite bank and line in the point E on the line CB, and likewise the point F on the line DB. Measure CD and EF carefully. The distance AB is then calculated as follows: If the several distances are as indicated in Fig. 30, the calculation is as follows: - r- X ioo = 200 160 X 100 = 500 ft. Problem 4. If the backsight BA (Fig. 31), is N. 40 E., 1230 ft., and the foresight BC is S. 60 E., 3042 ft; what is the length and bearing of the closing side CA ? Starting from A, the bearings and length of the courses, together with the latitudes and departures, are as follows: Bearing Distance Latitude Departure S 40 W 1230 942.188 790. 64 W S 60 E 3042 1521.00 S 2634. 37 E 2463 . 18 S 1843 . 73 E The total latitude or southing is, therefore, 2463.18 ft., and the total go COAL MINE SURVEYING net easting 1843.73 ft. In order to close this survey, the line CA must, therefore, have a northing of 2463.18 ft., and a westing of 1843-73 ft. To find the bearing of this closing course, call the angle of the bearing a ; then, 0.7485 and a = 36 49'. The bear- ing of the closing course is, therefore, N. 36 49' W. The length of the closing course is then found as follows: 2463.18 cos 3 6 49' 2463.18 = 0.80056 3076.8 //. FIG. 31 COORDINATE SYSTEM OF CALCULATING CLOSING COURSE. Problem 5. A certain seam cuts a vertical fault and the upthrow is found to PLATE OF SURVEY, SHOWING THE be g o ft. The geam beVOnd , the fault dips at the rate of 4 in. per yard. What is the length of a drift rising r\ in. per yard, that will cut the seam beyond the fault? The combined dip of the seam and rise of the drift is 4 + i-S = 5.5 in. per yard. Assuming horizontal measurements in the seam and the drift alike, the horizontal length of the drift, measured from the fault to the place where it cuts the seam, would be: 60 X 12 = 130.9 yd* 5-5 FIG. 32 Fig. 32 shows the relative posi- tion of the fault, the seam on each side of the fault, and the stone drift driven to the rise, across the strata, to connect the seam at the fault with the seam beyond. Problem 6. A method of turning off an entry at right angles without the use of a compass. SHOWING A VERTICAL UPTHROW OF 60 FT. SOME PROBLEMS IN SURVEYING Si Suspend a bob from each of the two respective points or stations A and B (Fig. 33) of the entry survey. Stretch a string carefully in line with these bobs or points. By means of this string, line in the points and P opposite the centers of the respective cross entries. Also line in the points a and b, respectively, at any convenient equal distances, on each side of 0, Then from these points a and b as centers and with any fixed radius ac, greater than aO, describe in turn the intersecting arcs which determine the point c and the line OX at right angles to AB. These yj j ^ Main Entry b Survey Line P A COM. A6E FIG. 33. SHOWING TWO METHODS OF SETTING OFF A RIGHT ANGLE WITHOUT USING A COMPASS. lines can often be laid off with chalk on the roof, but the work requires care. In a similar manner the triangle Pmn may be laid out, using the numbers 3, 4, 5 or any multiple of these more convenient, as 6, 8, 10 ft. This gives a right triangle, because 6 2 + 8 2 = io 2 and makes the line PY at right angles to AB. It is important to remember that all measurements must be made in the horizontal plane for any angle other than a right angle, which can be laid out on the pitch. MINING METHODS BY ' ROBERT BRUCE BRIXSMADE, B. S., E. M. COPYRIGHT, 1911, BY THE McGRAw-HiLL BOOK COMPANY, INC. CONTENTS CHAPTER I Explosives and Their Use in Mining CHAPTER II Principles of Blasting Ground CHAPTER III Compressed Air for Mining CHAPTER IV Principles for Controlling Excavations CHAPTER V Principles of Mine Drainage CHAPTER XVIII Principles of Mining Seams (a) Comparison of Longwall and Pillar Systems . (b) Comparison of Advancing and Retreating. (c) Mining by Roof-pressure CHAPTER XIX Advancing Longwall Systems for Seams Example 49. Spring Valley Collieries, 111 Example 50. Montour Iron Mines, Danville, Pa. . Example 51. Bull's Head Colliery, Eastern, Pa. . Example 52. Vinton Colliery, Vintondale, Pa. . . Example 53. Drummond Colliery, Westville, N. S. CHAPTER XX Pillar Systems for Seams Example 54. Advancing System Layouts Example 55. Nelms' Retreating System Example 56.; Nelms' Advancing-retreating System .... Example 57.'- Connellsville District, Western Pennsylvania. Example 58. Pittsburg District, Western Pennsylvania . . CHAPTER XXI Flushing System for Filling Seams and Recovering Pillars . . . Example 59. Anthracite District, Eastern Pennsylvania. . Example 60. Robinson Mine, Transvaal INDEX MINING METHODS CHAPTER I EXPLOSIVES AND THEIR USE IN MINING An explosion may be defined as a sudden expansion of gas. The substances which we call explosives are so unstable when exposed to a suitable flame or shock that they suddenly change into many times their original volume of gas with the evolution of heat. If the change to a gas takes place in the open, there is a flame and a whiff or a report. It is only, however, when explosives are set off in confined spaces like drill- holes that they do their chief work in mining. Consequently a blast or explosion may be said to be a rapid combustion in a confined space. Explosives have two essential constituents, namely, combustibles and oxidizers. They may be broadly divided into three classes accord- ing to the relation which the combustibles bear to the oxidizers. Class I includes the mechanical explosives, or those in which the ingredients constitute a mechanical mixture; class II includes the chemical explo- sives or those in which the ingredients are in chemical combination; class III includes the mechanico-chemical explosives which are formed of a mixture of class II and an absorber. METHODS OF FIRING EXPLOSIVES Explosives are set off by two means ignition and detonation. Because through ignition the combustion is transmitted by heat alone, it gives a slower explosion than one started by detonation which trans- mits the reaction by the rapidity of vibrant motion. By their nature class I is adapted to ignition, and classes II and III to detonation. Ignition is commonly performed by squibs, fuse or electric igniters. A squib is really a self -impelling slow match, made by filling one-half of a thin roll of paper with black powder and the other half with sulphur. For their use in blasting, a drill-hole ab, Fig. 1, is loaded with an explo- sive be and before filling the hole with the tamping cd, a needle ac is inserted into the explosive so that when it is withdrawn, a hole of a larger diameter than the squib is left through the tamping from a to c. 1 MINING WITHOUT TIMIJKIl Fio. 1. Drill-hole section. The squib is then inserted in this hole with the sulphur end out, and when lit the slow-burning sulphur allows time for the miner to escape before the powder of the squib takes fire and its reaction forces the squib along the holes to ignite the powder at c. A fuse is merely a thread of black powder wrapped with one or more thicknesses of tape. In loading the hole, Fig. 1, the fuse would be inserted in place of the needle ac. A fuse burns commonly at the rate of 2 ft. a minute. Therefore a sufficient length should be used in the hole to allow the miner to retire in safety, after splitting and lighting the outer end, before the flame reaches the explosive at c. The electric igniter consists of a shell a, Fig. 2, enclosing a charge of fulminate mixture in b and of sulphur cement in e. The copper wires c pass through / and enter 6 where they are connected by a platinum bridge at d. For ignition, the shell a is made of pasteboard and the igniter is placed within the explosive while the wires extend outside the hole to a blasting machine. The last is simply a small armature revolving between its poles and sending a current through the igniters in the circuit when its handle is shoved down. All the common electric igniters on one circuit are exploded simultaneously, but a recent inven- tion is a delay-action igniter which permits electric firing in sequence. Detonation is performed by fuse and cap or by electric caps. A blasting cap is simply a cylindrical copper cup with a small charge of fulminate mixture in its bottom, the fuse being inserted into the cup and fastened to it by crimping pincers. The cap is then inserted into one cartridge of the explosive and its attached fuse tied firmly to it by a string, in order to make a primer which is placed near or on the top of the explosive. The loaded hole will then resemble Fig. 1, the explosive being in be, the cap and primer at c, and the fuse along ca. Lighting the fuse is the same as for ignition, only the fuse now fires the cap whose explosion detonates the explosive. The electric cap resembles the electric igniter, Fig. 2, but has a copper instead of a pasteboard case a and the quantity of charge of fulminate mixture at b is increased as the sensitiveness of the explosive diminishes. The electric cap is inserted in and fastened to a primer-cartridge like Fio. 2. Electric exploder. EXPLOSIVES AND THEIR USE IN MINING fuse and cap, the electric cap being fired by a blasting battery in the same way as the electric igniter. LOADING AND TAMPING A mechanical explosive like black powder usually comes in bulk. For loading it is poured into a cartridge (the size of the hole) which is made by rolling a piece of paper around a pick handle. For damp holes the cartridge must be oiled or soaped on the outside. This paper cartridge is pressed down into the hole by a soft iron tamping bar whose tip should be an expanding copper cone grooved on the edge for the purpose of allowing the copper loading needle or fuse to pass. Tamping bars with iron tips or iron needles are highly dangerous in formations containing pyrite or other hard minerals, on which the iron might strike a spark, and their use is therefore prohibited by law in many places. A mining explosive of class II or III is handled in paper cartridges which can be ordered of a diameter to fit the hole. Before loading they are slit around lengthwise to permit of the explosive taking the shape of the hole when it is pressed down by a tamping bar which should be of wood for these explosives, instead of copper-tipped iron, on account of their being more sensitive to any shock than black powder. In coal mines, coal dust is commonly used for tamping black powder, but this is a very unsafe practice in dangerous mines, for a windy or blown-out shot will have its normal flame increased, both in length and duration, by the ignition of the tamping. The best materials for tamp- ing are a fine plastic clay or loam and ground brick or shale, and al- though sand is too porous to do well for black powder, it answers for higher explosives but must be confined in paper cartridges for use in uppers. Water is used as tamping for nitro-glycerine and high explosives in wet down-holes, but it is little better than nothing. The fact that higher explosives will break rock without any tamping has caused many miners to abandon tamping them altogether on account of the ease of recapping untamped charges in case of a misfire. Mechanical explosives must be tightly tamped, nearly to the collar of the hole, or they will blow out instead of breaking the rock, and although the tamping may be shortened with detonating explosives, as they become quicker and stronger, a short length of tamping adds to the efficiency of the highest explosives. Where only quick-acting explosives of classes II or III are at hand and it is desired to blast with the slow action of class I, the object can be partially obtained by special methods of loading. These methods provide an air cushion between the explosive and the rock and tamping by either having the stick of explosive of considerably smaller diameter than the drill hole or by having a very porous cellular tamping to sepa- rate the tight tamping from the explosive. 4 MINING WITHOUT TIMBER Before examining the various mine explosives in detail, let us consider an illustration of the method of calculating, 1 from the chemical equation of an explosive, its calorific power, its temperature, and the number of expansions and its consequent exploding pressure. Let us assume the simplest case of a mechanical mixture of hydrogen and oxygen at a temperature of C. and at sea-level pressure of 760 mm. of mercury. Then the chemical equation for complete combustion is 2H 2 + 2 = 2H 2 0. (1) the molecular weights being 4 + 32 = 36. (2) If t = thermometer temperature in degrees centigrade of the explosion; T = absolute temperature in degrees centigrade of the explosion; S = sign for summation; ^ etc. = weights in grams of various combustibles of the explosive; 2 , etc = calorific power in calories of various products of combustion of the explosive; ww l w 3 , etc. = weights in grams of various products of combustion of the explosive; sSjSj, etc. = specific heat in calories of various products of combustion of the explosive; V = volume of explosive originally; V I volume of explosive due to chemical reaction alone; V 2 = volume of explosive due to chemical reaction and resulting tempera- ture, t; P = pressure of explosive originally; P 2 = pressure of explosive finally; then we have from thermo-chemistry, _ WC + TFA + TF 2 C 2 , etc. = SWC For the given problem we have from equation (2) W = 4: grams of H gas; w = 36 grams of H 2 vapor. From thermo-chemistry we have, C = 28,780 cal. for H; s = 0.4805 cal. for H 2 O vapor; substitute in (3) and - 4X28 ' 78 -=6660C. 36X0.4805 Then, from Avogardro's law, that the molecules of equal volumes of all gases under like conditions occupy the same volume, we have from (1), 2 vols. H + l vol. O = 2 vols. H 2 O, or V l = 2/3V. (4) i See "Metallurgical Calculations," by J. W, Hichards. EXPLOSIVES AND THEIR USE IN MINING 5 From Charles' law, the volumes of gases vary directly as their abso- lute temperature we have thus !>= T V l + 273 or _ 6660 7 t< 2 ~~273~' substitute from (4) and we have - From Boyle's law, if the gas of volume 7 2 is prevented from expand- ing beyond volume 7, we have for the final pressure P 2 in the explosive chamber P, or fa = f'* (6) Substitute in (6) from (5) and, as P = 1 atmosphere = 14.7 Ibs. per sq. in., we have 16 27 P PJJ= - - -=16.2 atmospheres. or 238 Ibs. per sq. in From physics, T = t + 273, hence t = T 273 = 6660273 = 6387 C. In practice, this theoretical pressure and temperature, resulting from the explosion, would have to be multiplied by a fractional factor of efficiency to allow for imperfect combustion and loss of heat through radiation and leakage. In large charges, these losses are proportionally less than in the case of small charges. This fact, coupled with the greater likelihood of their meeting weak places in the blast's burden, accounts for the higher efficiency of the former. These theoretical calculations are especially useful in comparing the relative strength of different explosives of the same type. In France, they are used extensively in the inspection of permissible explosives to determine if their final tempera- ture is sufficiently low for use in dangerous coal mines. The practical usefulness of explosives depends upon (1) their cost of manufacture; (2) their safety and convenience as regards transportation 6 MINING WITHOUT TIMBER and storage; (3) method necessary for their loading and exploding; (4) their exploding pressure; (5) the rapidity with which they explode; (6) the length and temperature of the flame. These six factors will now be discussed seriatim. Factor (1), or the cost, is often the most impor- tant factor in commercial operations like mining, although for purposes of war it is often little considered. Factor (2) or safety, affects the desirability for all purposes, the more sensitive the explosive, the higher the freight rate by rail or boat, and if sensitive beyond a certain point, it cannot be shipped thus at all. Those explosives which, like dynamite, freeze at ordinary winter temperatures are at a disadvantage as are also those which, like black powder, are handled loose and can be easily ignited by a spark struck by a hob-nailed shoe on a floor spike. Some explosives, like imperfectly washed guncotton, are liable to explode by spontaneously generated heat, while others become dangerously sensi- tive if exposed to the sun during shipment. The desirability of explo- sives belonging to either of these last two mentioned classes is plainly discounted because of these attributes. The next factor (3) or loading and exploding, is important in connection with conditions such as prevail in dangerous coal mines (where an open light is prohibited), in subaque- ous blasting (where both explosive and exploder must be unaffected by water), or where misfires could not be corrected. Factor (4), or the pressure, is what determined the real effective breaking force of the explosion, but it is modified in practice by (5), or the rapidity of the explosion. Slow and fast explosives are comparable to presses and hammers for forging steel. The former exerts its pressure gradually until the strain exceeds the tensile strength of the material and the rock gives way along a surface of fracture. The latter gives a sharp quick blow which will shatter the surface of rock exposed to the explosive before any fracturing action is exerted on the blast's burden of rock. The slow explosive will detach the rock in large masses while the fast type may crush it to bits. Black powder is an example of the first and nitro-glycerine of the second. Explosives with all graduations of rapidity between these extremes are on the market. The fastest explo- sives are applicable where the rock is very hard to drill as, for example, in the case of certain Lake Superior hematites, or where a tremendous force must be exerted from confined spaces as in breaking the cut for development passages; also where a shattering rather than a fracturing action is needed, as in chambering the bottom of drill holes or in shooting oil wells. The slowest explosives are used in quarrying, for the purpose of detaching monoliths, or in consolidated or soft rock which can be fractured by a slow, pressing movement but only dented by a quick hammer blow. Factor (6), or the flame and temperature, is an important considera- tion for blasting in gassy or dusty coal mines. The so-called " permis- EXPLOSIVES AND THEIR USE IN MINING 7 sibles" are explosives made to fall below a minimum legal requirement as regards length and temperature of flame. When one considers that a permissible like carbonite gives, in practice, a flame height of 15.8 in. and a flame duration of 0.0003 seconds, as compared with 50.2 in. and 0.1500 seconds respectively, for black powder, we can see how much safer the permissible is to use. We will now consider the properties of the three classes of explosives: CLASS I, OR MECHANICAL EXPLOSIVES The common representatives of this class are black powder and mechanical permissible explosives. Black powder was discovered before 600 A. D. by the Chinese, and by Roger Bacon in 1270, but it was not used for mining until Martin Weigel introduced it at Freiberg in 1613. It can be made from a single combustible, charcoal, mixed with an alkaline-nitrate oxidizer, but in order to lower its ignition temperature for blasting to about 275 C., part of the charcoal is replaced by sulphur. For the cheaper blasting powders, the oxidizer is sodium nitrate which, being easily affected by dampness, is replaced in the higher grade powders by potassium nitrate. The ingredients are first ground then mixed thoroughly while moist and finally pressed in cakes, dried, broken and sized. Assuming the equation for the complete combustion of black powder to be. 3C + S + 2KN0 8 =3C0 2 + N + K 2 S. (7) We have by calculation for its percentage composition, carbon = 13. 4 sulphur =11.8 sodium nitrate = 74. 8 100^0 and for the percentage composition by volume of its resulting gas, C0 2 = 75 N =25 ~100~ The theoretical exploding temperature is 4560 C. and the pressure is 5820 atmospheres. In practice the composition is varied according to the experience of each maker. As the combustion is imperfect, poison- ous and combustible gases like carbon monoxide, hydrogen sulphide and hydrogen and unpleasant vapors, like the sulphide, sulphate, hypo- sulphite, nitrate and carbonate of potassium, are given off by the explo- sion and sometimes render breathing or the carrying of open lights in the fumes a dangerous procedure. In fact, Bunsen's experiments proved 8 MINING WITHOUT TIMBER that only one-third of the ignited gunpowder really followed the reaction of equation (7). Black powder is sold in grains which vary in size from the fine sporting gunpowder to the 2-in. balls of artillery powder. For blasting, the grains vary in diameter from one-eighth to one-half of an inch, and the rapidity of the explosion decreases with an increased diameter of grain. The grains should be of uniform size, quite dry and thoroughly tamped in the hole in order to get good results. The specific gravity of lightly shaken black powder is about the same as water. Its cheapness, non- freezing, comparative safety for shipping and handling, easy explosion by ignition and slow action are the favorable qualities of black powder which cause its wide use. For coal mines free from dangerous gases and dust, it is a better explosive than detonating permissibles whose quicker action breaks up the coal and injures the roof more. Black powder is rendered inefficient for many other purposes, however, because of its necessitating much tamping, its low power, the readiness with which it is spoiled by moisture and its long flame. Of the mechanical permissibles bobbinite has been extensively used in England. Its percentage composition is, Potassium nitrate = 65.0 Charcoal = 20 . Sulphur = 2.0 Paraffin wax= 2.5 Starch = 8.0 Water = 2.5 100.0 It is thus chemically very close to black powder excepting that it contains more charcoal and less sulphur and makes up that discrepancy by the addition of wax, starch and water. The lack of sulphur raises its ignition temperature while the wax forms a waterproof coating for the grains of powder. The starch and water absorb heat, shorten the flame and decrease the exploding temperature to under 1500 C. It is handled in compressed cartridges with wax coverings. It has a central hole to admit the fuse, for ignition by squib is not allowed in dangerous coal mines. CLASS II, OR CHEMICAL EXPLOSIVES The five common explosives of this class are guncotton, nitro-glycerine, nitro-gelatin, fulminates and picrates. They all contain nitryl (NO 2 ) and their detonation is made possible by the unstable quality of nitryl compounds. Guncotton, This was discovered by Schonbein in 1846, but it was little used until it was found that its dangerous instability was not EXPLOSIVES AND THEIR USE IN" MINING 9 inherent but due solely to the surplus acid left in its tissue by imperfect washing methods during its manufacture. The equation for making it is, C 6 H 10 5 + 3HN0 3 = C 6 H 7 6 (NO 2 ) 3 + 3H 2 0. (8) cotton + nitric acid = guncotton + water. The ingredients are allowed to stand in a cold place for some time before the washing out of the free acid is begun. The reaction on exploding is, 2C 6 H 7 5 (N0 2 ) 3 = 3C0 2 + 9C0 2 + 3 N 2 + 7H 2 0. (9) Equation (9) shows that the explosion gives no solid product like the K 2 S of equation (7) and that the percentage composition by volume of the resulting gas is, CO 2 = 13.7 CO = 40.8 N = 13.7 H 2 0=31.8 100.0 f By the method of calculation already explained, it is found that guncotton theoretically has an exploding temperature of 5340 C. and a pressure of 20,344 atmospheres. The combustible qualities of the large percentage of carbon monoxide resulting from its explosion render guncotton unfit for use in coal mines, and its poisonous qualities make it unsuitable for any underground use. For surface work, it is very powerful, smokeless, does not freeze and is not volatilized or decomposed by atmospheric temperature. It ignites between 270 and 400 F. and if unconfined will then burn quietly. When dry, it is sensitive to percussion and friction, but under water it is insen- sible to ordinary shocks. Immersed, it absorbs from 10 to 15 per cent, of water, but even then it can be exploded without drying by the use of an extraordinarily strong detonator. Its chief disadvantage above ground is its high cost and the fact that it comes in hard compressed cartridges (specific gravity about 1.2) which fit drill holes only imper- fectly and therefore lose in efficiency. For any destructive work without the use of drill holes, like demolishing walls, dams and the like, the sharp, sledge-hammer blow of its explosion renders it very efficacious. Nitro-glycerine or "Oil." This was discovered by Sabrero in 1847, but did not become commercially valuable until 1863 under the direction of Alfred Nobel. The equation for its making is, C 3 H 8 3 +3HN0 3 = C 3 H 5 3 (N0 2 )3+3H 2 0. (10) glycerine + nitric acid = nitro-glycerine + water. Strong sulphuric acid is an ingredient of the mixture, but it does not take part in the reaction, which must take place at a moderate tempera- JO MINING WITHOUT TIMBER ture to be safe. The resulting "oil" is much easier to wash than gun- cotton and consequently is cheaper. It is a yellow, sweetish liquid poisonous both to the blood and the stomach. Its specific gravity is 1.6. Its freezing-point is about 45 F. and to insure against freezing the tem- perature must be above 52 F. When frozen, it is insensible to ordinary shocks, as is also the case when it is dissolved in alcohol or ether. It is, therefore, commonly shipped either in tin cans, packed in ice, or in solution hi wood alcohol. It can be precipitated from the latter before use by an excess of water. Nitro-glycerine does not evolve nitrous fumes until 230 F. As it begins to vaporize at about 100 F., it is important in thawing it not to exceed this temperature. Thawing, therefore, is only safely done by heating the explosive over a water bath at less than 90 F., or by leaving it in a room of the same temperature for some time. The explosive ignites at only 356 F. and if then pure and free from all pressure, jar or vibration, it will burn quietly. These safe-igniting conditions, however, are difficult to obtain, for a small depth of liquid causes sufficient pressure to explode it when ignited. Thus a film of it, heated on a tin plate, burned without an explosion only if under one-fourth inch thick. The exploding temperature is 380 F. This 24 margin above the igniting temperature accounts for the numerous cases of conflagration without explosion. The reaction of the explosion is, 4C 3 H 6 3 (N0 2 ) 3 = 12C0 2 + 2 + 3N 2 + 10H 2 O. (11) From equation (11) the explosive product is gaseous and its percen- tage composition by volume is CO 2 = 46.0 0= 3.8 N = 11.8 H 2 0= 38.4 100.0 By the previous calculating method, it is found that theoretically the exploding temperature is 6730 C. and the pressure is 29,107 atmos- pheres. From the fact that its explosive product contains no carbon monoxide, "oil" can be used underground, but only when mixed with an absorber. Alone, it is too sensitive to be safe, while being liquid, if unconfined, it would leak from holes in porous rock, and if confined in canisters it will not fill the drill hole. With its great speed and strength it also tends to shatter locally any enclosing rock, except the toughest, rather than detach it. These characteristics render it inefficient for most mining work. For shooting oil wells, however, its shattering quality renders it peculiarly suitable. For this purpose, a cylindrical canister of a diam- eter to fit the well and containing from 100 to 200 Ibs. of nitro-glycerine, EXPLOSIVES AND THEIR USE IN MINING 11 is carried to the well swung from the body of a spring buggy. After filling the well with water, the canister is topped with a cap and lowered to the proper depths by a rope, along which a weight, called a " go-devil," is dropped onto the cap to cause the explosion. Nitro-gelatin. This was discovered by Nobel in 1875 and is a yellow- ish jelly of considerable toughness, but easily cut with a knife. It is made by dissolving guncotton in nitro-glycerine. Authorities differ in the proportion of guncotton, some recommending only 7 per cent. To balance all the free oxygen of the nitro-glycerine by the excess carbon of the guncotton alone, takes 87.3 per cent, of the former to 12.7 per cent. of the latter and gives the following equation: 9C 3 H 5 3 (NO 2 )3 + C 6 H 7 2 (N0 2 ) 3 =33C0 2 + 15N 2 + 26H 2 0. (12) From equation (12) the percentage composition of the solely gaseous product is, C0 2 = 44.6 N= 20.2 H 2 0=35.2 By the theoretical calculation, the exploding temperature is 7080 C. and the pressure is 27,100 atmospheres. The last figure shows nitro- gelatin to be only 7 per cent, weaker by weight than nitro-glycerine, while its somewhat higher cost is due to its guncotton ingredient. When used alone for military purposes, about 4 per cent, of camphor is dissolved in the nitro-glycerine along with the guncotton to make a product called military gelatin. The last explosive is so insensitive that it can be punctured without effect by a rifle bullet. The common nitro-gelatin is much less sensitive than No. 1 dynamite, to shock or friction, and unaffected by a short immersion in water at 158 F. and by an 8-day immersion at 113 F. It will not exude nitro-glycerine under a high pressure or any atmos- pheric temperature. Its specific gravity is 1.6 and it can be set off only by a strong detonation. It ignites at 399 F. and will then only burn when unconfined. When it freezes, which is between 35 and 40 F., it becomes more sensitive than normally owing probably to the partial freeing of the nitro-glycerine ingredient. Nitro-gelatin is now used for mining wherever the highest power explosive is needed and is especially adapted to wet or subaqueous blasting, either alone or as "gelatin" dynamite. Fulminates. Mercuric fulminate is the common commercial salt. It is made as follows from mercuric nitrate and alcohol: (13) The explosive reaction is Hg(CNO) 2 = Hg+2CO+2N. (14) 12 MINTING WITHOUT TIMBER Equation (14) shows that mercuric fulminate is a poor explosive because it produces the poisonous fumes of Hg and CO as well as unburned carbon. If a little damp, it explodes very feebly and if quite wet, not at all. However, its non-freezing quality, its quick hammer- like vibrant explosion and its uniform sensitiveness to ignition or shock cause its use as the chief ingredient of percussion-cap mixtures for deton- ating other explosives. Its exploding temperature is 305 F. Picrates. These salts are founded on picric acid, which is made by mixing carbolic and nitric acid according to the equation, C 6 H 6 0+3HN0 3 = C 6 H 3 (N0 2 ) 3 0+3H 2 0. (15) Its explosive reaction is C a H 3 (N0 2 ) 3 = H 2 O+H + 6CO + 3N. (16) Picric acid comes in yellow crystals which are soluble in hot water or al- cohol, and melt at 230 F. It is used very largely in dyeing. It is expens- ive to make and difficult to explode. Equation (16) indicates that it produces much of the poisonous carbon monoxide which shows incom- plete combustion and consequently a decreased power. Picrates are the basis of the military explosive lyddite, but the recent commercial failure of the excellent mining picrate " joveite" may discourage future attempts to adapt them to blasting. CLASS III, MECHANICO-CHEMICAL EXPLOSIVES This class will be considered under five groups: (1) guncotton; (2) nitro-glycerine; (3) nitro-gelatin; (4) fulminate; (5) nitro-benzol. Deto- nating permissibles for coal mining fall mainly under groups (2) and (5) and will be considered last. Guncotton Group. The evaporating of guncotton, after it has been dissolved in a suitable solvent such as alcohol or acetone, produces a hard, horny material which is the basis of most modern smokeless gun- powder. Its chief blasting powder, however, is tonite which is formed by adding enough barium nitrate to guncotton to just completely oxidize the gases caused by the explosion as follows: 10C G H 7 O 5 (NO 2 ) 3 + 9Ba(NO 3 ) 2 = 60CO 2 + 24N 2 +35H 2 O+9BaO. (17) The percentage composition, by volume, of the gaseous product of equation (17) is, C0 2 = 50.4 N= 20.2 H 2 O= 29.4 Tool) By calculation, the exploding temperature is 5,730 C. and the pres- sure is 13,840 atmospheres, which are fifteen-fourteenths and two-thirds, EXPLOSIVES AND THEIR USE IN MINING 13 respectively, of the corresponding figures for guncotton. As an offset to lessened powder tonite is plastic, cheaper than guncotton and 50 per cent, denser. Its harmless fumes adapt it to underground use and, like dynamite, it is packed in paper cartridges. It has been extensively used in England, where it is shipped under the same safety regulations as black powder. It is hard to ignite and when alight, it normally burns slowly without explosion. Tonite, like guncotton, is non-freezable and is detonated only by a strong cap. Potassium nitrate has been used, instead of barium nitrate, as the oxidizer, in another guncotton mixture of similar properties which is called potentite. Nitro-glycerine Group. These mixtures are called dynamites. They were introduced by Nobel to lessen the sensitiveness of nitro- glycerine and at the same time retain its other good qualities. The absorber of the "oil" is called the "dope," which may be selected to be either inert or active in the explosion. The freezing temperature of all dynamite is that of nitre-glycerine, as is also its behavior when frozen and its method for being safety thawed. Dynamite that does not leak nitro-glycerine under the conditions under which it is to be used is one of the safest explosives known. It should not be shipped, however, in rigid metallic cases, which accentuate shocks and vibrations, but in wooden boxes in paper cartridges packed in saw- dust. Thus packed, it has failed to explode when dropped on the rocks from a considerable height or when struck by heavy weights. Dynamite can be heated with less danger than nitro-glycerine. If set on fire, it will usually burn quietly unless unfavorable conditions are present. If the dynamite is in a closed box, its smoke cannot escape and consequently the pressure may be raised enough to cause an explosion. If caps or gunpowder are present, the fire will explode them and the resultant shock will detonate the dynamite, If the heat from the fire causes the "oil" to exude from the cartilages, this "oil," if under a static head, will explode when ignited, as explained above. Again, the heat from the burning dynamite may heat the adjoining unlighted cartridges to the exploding temperature of 380 F. before they get sufficiently exposed to the air to ignite. Heated gradually in the open so much of the " oil " may be evaporated that a mere whiff ensues when the exploding temperature is finally reached. In spite of all these dangerous contingencies, several instances are on record where several tons of dynamite have burned in conflagrations without exploding. If afire in cartridges, it burns slowly like sulphur, but if loose it will burn quickly like chaff. The dope first used was inert infusorial earth or kieselguhr, which will safely absorb three times its weight of nitre-glycerine. The resulting kieselguhr dynamite when strongest contains 75 per cent. " oil. " It is a pasty, plastic, unctuous, odorless mass of a yellowish color with a specific 14 MINING WITHOUT TIMBER gravity of 1.4. The effect of the dope is to cushion the "oil" so that the shock to explode it must be stronger as the percentage of dope becomes greater. It is not possible to explode kieselguhr dynamites which con- tain under 40 per cent, of "oil" and even with 60 per cent, it takes a strong cap. The disadvantage of 75 per cent, dynamite is the exudation of "oil" on a warm day or under water so that dangers may arise from having to deal with the sensitive "oil" before suspecting its presence. It is thus ordinarily unsafe to ship or use and the 60 per cent, strength is now commonly sold as No. 1. The strength of kieselguhr dynamite is almost equal to that of its contained "oil." The active-dope dynamites have no such narrow limitations as the inert types and not only may numerous absorbers be used, but the per- centage of nitro-glycerine may vary from 4 to 70 per cent. These explo- sives go under various names. The common active absorbents are such combustibles as wood meal or fiber, rosin, pitch, sugar, coal, charcoal, or sulphur, and such oxidizers as the alkaline nitrates or chlorates. The chemical composition of the oil-dope mixture should be such as to give only completely oxidized products on combustion. The strength of this type is equal to that of the "oil" plus that of the explosive dope when completely burned. In other words, black powder mixed with enough "oil" to detonate it would all burn as shown by the reaction of equation (7), thus giving several times more power than when ignited alone. The density and appearance, as well as the necessary strength, varies with the dope and the percentage of " oil. " The commercial method of rating dynamite, by its percentage of " oil," is misleading as no account is taken of the varying strength of the explosive dopes. Nitro-gelatin Group. A mixture of this group is called a gelatin dynamite. Somewhat more expensive than nitro-glycerine, it is prefer- able wherever the highest power is desired and, being unaffected by water, it is the best powder for subaqueous use. It is more plastic and less sensitive than common dynamite and therefore easier to load and safer to transport, but it requires a stronger cap for exploding. The military powder gelignite, a favorite in England and Japan, and forcite come under this group. Fulminate Group. For percussion-cap filling, mercuric fulminate is mixed with a sufficient amount of some oxidizer to insure complete combustion on exploding. Alkaline-nitrate oxidizers may be used but potassium chlorate is the favorite. The latter gives the following exploding reaction: 3Hg(CNO) 2 + 2KC10 3 = 3Hg + 2KCl+6C0 2 + 6N. (18) Equation (18) shows that potassium chlorate should form 22 per cent, by weight of the mixture, which also contains a little gum to give EXPLOSIVES AND THEIR USE IN MINING 15 coherence. Caps are designated by numbers or letters according to the amount of fulminate contained. The common series is. Hg (CNO) 2 Cap No. Grains. 1 4.5 2 6.0 3 8.0 4 10.0 5 12.0 6 15.0 6.5 19.0 7 23.0 8 30.9 The larger the cap, the more expensive, but if the cap selected is too small to insure perfect detonation of the explosive, incomplete combustion will ensue with noxious fumes and loss of power. In general, dynamite requires stronger caps as the percentage of nitro-glycerine or the temper- ature decreases. Nitro-benzol Group. Although nitro-benzol contains nitryl it does not contain sufficient oxygen to be an explosive and, when unmixed with its oxidizer, it can be shipped as an ordinary chemical. On this account, the nitro-benzol or Sprengel group is especially adapted for use in isolated places far from dynamite factories. The favorite Sprengel explosive is rackarock, which is a mixture of nitro-benzol with the chlorate or nitrate of potassium or with sodium nitrate, as an oxidizer. By mixing 77.6 per cent, of mononitro-benzol with 22.4 per cent, of sodium nitrate, we can get the following reaction on detonation: 2C 6 H 5 (N0 2 ) + 10NaNO 3 = 12CO 2 + 6N 2 + 5H 2 O +5Na 2 O. (19) From equation (19) the percentage composition, by volume, of the gaseous product is, C0 2 = 52.2 N= 26.1 H a O= 21.7 100.0 By calculation, the theoretical temperature is 5300 C. and the pressure is 13,800 atmospheres. Unlike ignited black powder, rackarock, when properly detonated, follows closely its theoretical reaction which shows harmless gases and a temperature of 79 per cent, and a pressure of 47 per cent, of the figures for nitro-glycerine. For practical use, the oxidizer of rackarock is handled alone in wax-paper cartridges and the required quantity of nitro-benzol is not poured into a cartridge until just before charging the drill hole. 16 MINING WITHOUT TIMBER Detonating Permissibles. These explosives practically all contain either nitre-glycerine, nitro-gelatin, nnitro-bezol or ammonium nitrate as the detonated ingredient and some contain two or more of them. Their exact composition is usually kept secret by the manufacturers, but they must pass the government tests for temperature and flame. These explosives are made of various strengths and require stronger caps than common dynamites. Detonation means a quick generation of a email quantity of hot gas while the ignition of black powder means the slow production of a large quantity of impure gases and vapors. A large quantity of fine, unstable salt like magnesium carbonate, of a steam- generating salt like ammonium nitrate, or of a substance with much hygroscopic moisture like wood meal, are the ingredients relied upon to cool the quick small flame of permissibles. The compositions of a few typical permissibles are as follows: Name. Nitro-benzol. NH Return Curren Brick Stoppings = Doors /" Overcasts Fia. 140. Fkst layout (Monongahela colleries) at Pitteburg, Pa. apart, of which space the pillars occupy 15 ft. It will be noticed that the room-stumps of each upper panel are left undisturbed on the advance so as to protect the return airway, but when the pillars of the lower panel are being drawn, the upper stumps are also pulled, as the receding line of roof-fracture passes them, along with the butt-entry pillars. The last pillars, however, must be left undisturbed in the advancing system along 108 MINING WITHOUT TIMBER their whole length until all the adjoining coal has been exhausted up to the boundary. The use of four main entries, by this method, allows the two outside gangways to be return-airways and the two intake-airways to be on the inside and thus, gives an ample main-airway area and a min- imum interference with transport. The room-work is in the fresh air and pillar-drawing is on the return-air side of it. The room-track is always laid along the straight rib, and in many mines the refuse between the track and the other rib fills the room nearly roof high. FIG. 141. Second layout for large output, Pittsburg. Fig. 141 shows a second layout for large output, used in the Pittsburg seam, with six main entries. There are three face entries, nominally, but four actually, as the nearest room on the butt is advanced along with them so as to give an additional airway. As shown, the rooms are only worked on the outbye side of the butts, and the first room is started from the far end of a panel and followed, at the proper distance on the retreat, by pillar-drawing. By starting work from No. 2 and the follow- ing butts at the proper time, it is possible to keep the line of roof-fracture PILLAR SYSTEMS FOR SEAMS 109 of a panel continuous, for entry-pillars and room-stumps are removed as shown from the panel-end back to the butts. The method of Fig. 141 has permitted the extraction of 70 per cent, of the pillars by machine cutters under an average cover of 200-ft. thick- ness. For this purpose machine cross-cuts, 21 ft. wide, are made in the pillars so as to leave for each a stump only 9 ft. wide to be removed by hand-pick. This cross-cutting is shown by the different cross-hatching of the figure which also illustrates the overcasts and brattices for ventila- tion, and the chutes, etc., for transport. A third method of attack by which one company mines over 2,500,000 tons yearly is shown in Fig. 142. Here the room pillars, after the room FIG. 142. Third layout, with tapering pillars, Pittsburg. has advanced 100 ft., or to the first break-through, are gradually tapered off to a point at, the room-end. This causes the roof to fall along the tapered parts of the pillars and the latter are lost, but much of the thicker pillar near the room-neck can be recovered by subsequent careful pick- work. This method gets nearly all the coal by room-work, and a total recovery of 90 per cent, is claimed by its advocates. It is more danger- ous, however, than the two previous systems, requires more timber, and squeezes are more liable to occur. Where this high Pittsburg seam is dirty, so that much gob must be stowed along the rib on the advance, it is customary on drawing the pillars to leave a vertical shell of from 12 to 18 in. of coal next to the gob to prevent any pollution of the broken coal. CHAPTER XXI FLUSHING SYSTEM FOR FILLING SEAMS AND RECOVERING PILLARS EXAMPLE 59. ANTHRACITE DISTRICT, EASTERN PA. (See also Examples 5, 51 and 59.) Parallel Seams of Various Thickness and Dip Filled with Refuse from Breakers and Dumps. The flushing system was first developed in 1885 at the Pardee No. 5 mine near Hazleton, Pa., and was later copied and extensively used in many German collieries. Three conditions made flushing a valuable innovation in the Pennsylvania anthracite region, namely, the numerous large dumps of waste available for filling, the parallel and superincumbent seams to be extracted, and the overlay of much workable coal by townsites. The gravity of the urban situation is evidenced by the report of April, .1911, made by the Scranton Com- mission. l This report states that a large part of Scranton is already undermined and that for the stability of the present dangerous area of 15 per cent, of the city and for the recovery of the coal pillars from the balance the flushing system is the only remedy. The following description in based on the author's visits to mines of the following coal companies: Philadelphia and Reading; Delaware and Hudson; Delaware, Lackawanna and Western; Plymouth; and Lehigh Valley. In mining the flat seams to the north of Wilkesbarre by the pillar system of Fig. 130 much of the waste broken with the coal can be left in the rooms; but in the seams of the southern districts where mining is done by "overhand stoping with shrinkage and chutes," as in Figs. 132 and 133, all the waste has to be hoisted. The crude coal reaching the surface is a mixture of pure coal, "slate," "slate-coal", and" bone." The "slate" corresponds to the shale and clay of the partings and beds of the bituminous regions, the "slate-coal" consists of lumps, part pure coal and part slate, and the "bone" is a coal containing too little carbon (present limit 60 per cent.) to be marketable. All crude coal is put through a dressing mill or " breaker" in which impure pieces are broken sufficiently to detach the slate and bone from the pure coal, so that all the latter may be screened for separation into commercial sizes and the former, along with the "culm" or coal dust, be sent to the waste dump or mine stopes. * "Mine Caves under Scranton," by E. T. Conner. Trans. Min. Eng., Vol. 42, p. 246. 110 FLUSHING SYSTEMS FOR FILLING SEAMS 111 112 MINING WITHOUT TIMBER The limit of size between fine coal and unmarketable "culm" has so decreased in recent years that now all the fine sizes of the breakers, as well as many old waste dumps, are being washed over shaking screens in special mills called "washeries," for their content of fine coal of commercial value. The present upper limit for "culm" is a diameter varying from 5/64 to 3/16 in., but some independent operators use also some larger sizes for flushing. This rejected fine coal, as mixed with the slate and bone tailing from the breaker and the ashes from the boiler plant, forms " slush, " the chief material now used in filling the mine stopes by the flushing system. At some mines, the larger pieces of bone are saved on a special dump as of possible future value. Fig. 143 shows the Dodson colliery at Plymouth, Pa., with the waste dump at A, the breaker at B, and the washery at C. In digging an old waste dump for passage through a washery, in order to separate the marketable coal before flushing, a system of chain conveyors as at D and H, Fig. 143, is used. The usual conveyor has a single chain and drags its steel plate scrapers, 18 in. long, 12 in. high, and set 3 ft. apart, in a trapezoidal trough made by lapping the ends of 3-ft. lengths of steel or cast-iron plate. The maximum length of a single conveyor trough is about 500 ft. It is supported within square wooden frames, E, set 8 ft. apart, and built of 4x6-in. pieces. Near the top of the frames E, run two 25-lb. steel rails to support the scrapers on their return trip. Each conveyor is run by an independent steam engine, as at F, con- nected by gearing to its head end, and its capacity of 100 to 200 tons of dry material per hour is fed in, anywhere along the trough, by hand shovels or by hydraulicing with hose. Obstacles between the dump and washery are passed by using several conveyors, set at an angle, of which only the conveyor at the feed end need be shifted as the dump dwindles. The driving engine is set on a timber frame so that it can be easily pushed into line, by screw jacks, when the conveyor is moved over by levers; both engine and conveyor are elevated on rollers before shifting. This is done by the regular attendants who consist of two men for feeding and one man at each driving engine. So much fine marketable coal can now be saved from the present breaker-tailing and from the old "culm" dumps that the final rejected waste can fill only a fraction of the space left above the gob in the under- ground rooms. The huge dumps which formed such a prominent feature of the landscape, as late as the early nineties, are rapidly dis- appearing and filling is now being won even from river beds. Thus the Plymouth Coal Co. has a plant to bring sand and fine mine waste, now settled at the bottom of the Susquehanna river, to its Dodson mine No. 12. A suction pump on a barge located across the river from the Dodson breaker delivers into a pipe which crosses the river on FLUSHING SYSTEMS FOR FILLING SEAMS 113 barges and discharges into an elevator which lifts the material to the flushing flume for the mine. As no pieces larger than 1-in. dia. and few over 1/4-in. dia. are used in flushing, the coarser pieces of bone and slate, from breaker or dump, are passed through a pulverizer usually of the Williams' or Jeffrey's type, before reaching the flume G, Fig. 143, where they mix with the fine waste from washery C. Enough water is put in the flume to transport the slush along the flat pipes above the stopes, so the liquid slush carries only about 20 per cent, of solids by weight. The descent of the slush is through wrought-iron pipes, 4 to 6 in. dia., following either a shaft or a special bore-hole into the workings, perhaps 1000 ft. beneath. Over the top of the descending pipe is placed a funnel and a screen with 1-in. holes, and at each flushing station are three gate valves, to regulate the flow into the stopes, connected by electric signals with the surface. One of these station valves regulates the flow horizontally, another cuts off the vertical column below, a*nd by a third the column can be drained up to the nearest flowing point above, in case of a stoppage. The pipes used for transport along the levels are 4 to 6 in. dia., and of either wrought-iron or wood. In upgrade levels or where the pipe is under much pressure, new iron pipes with screw or flange couplings must be used, but when these are somewhat worn they are transferred to the down- grade levels. In the latter, the iron pipe has standard couplings on tangents, but on curves it has 7-in. unthreaded nipples for couplings slipped over the pipe ends and made tight by wooden wedges. These wedged couplings enable the pipe to be rotated, when its bottom gets thin, so that it can be worn to a mere shell all around before rejection. The wooden pipe is made in Elmira, N. Y., of tenoned maple staves about 2 1/2 in. thick which are bound with spiral steel hoops and coated with tar. It comes in 2- to 8-ft. lengths, with male and female ends for slip-jointing with cement. It can be joined to cast-iron fillings by in- serting special cast-iron nipples in its ends, and its own joints can readily be made to follow easy curves. It is lighter and cheaper than iron pipe, is found to last well on downgrade levels, and is preferable for use with acid water. In one mine, the iron pipe is used on a 2-mile permanent transportation line and the wooden pipe in the neighborhood of the actual filling. Plugged cast-iron tees are placed at 100-ft. intervals along all lines in the levels, so any obstruction can be easily located and removed. When a pipe is upgrade, a special precaution is taken against clogging by pass- ing fresh water alone through it, for 15 min., before stopping the flow. Care must be taken to provide air escapes at high points of the lines in order to avoid water hammer. The openings filled by flushing are old rooms opened on the pillar system of the last chapter. A room on a dip is easiest filled, as it requires 114 MINING WITHOUT TIMBER only one dam or barrier at its lower end. One disadvantage of increasing steepness is the greater strength of dam necessary to resist the corre- spondingly higher water head. In the Dorrance mine the old rooms had been opened on the rise from double flat entries as in Fig. 130. Every ten rooms along the entry were separated by panel-pillars following the dip. For filling, the flushing pipe was laid along the airway above the rooms and its discharge placed at the head of the central room of a panel of empty rooms. The latter had been prepared for filling by erecting dams across the necks at the room-bottoms and behind the break-through brattices of the ninth room 's pillar, for the last room of the panel was to be left open as an air and manway. The brattices of the break-throughs of the intermediate rooms had been removed to permit of a free flow of filling along the panel. Room dams are made of either stone or wood. The former are thick walls of roof slate laid up with mortar of slush and straw in a similar Cross Sec. Sec. a-b FIG. 144. Dam for holding slush, Eastern Pa. form to the wall of Fig. 145 described in the next Example. The favorite dams are of wood and a typical one is shown hi Fig. 144. Round props ab, of sufficient size for the expected strain, are covered on their upper side with 2-in. plank and backed, as an extreme case, with stringers 66' and cc' with corresponding angle braces &/ and cd. If the seam-walls are strong, the hitches alone will hold the props, so that the pieces 66' and bf can be omitted, and in thin seams even cc' and cd are left out. When wetted, the seams between the planks soon close up sufficiently, but the irregular spaces around the periphery mn'b'b are caulked with straw in one mine, and in another, with a weak floor, the props are set in a low concrete wall, 12 in. wide. In one seam of the Dorrance mine on an 18-deg. slope with rooms 300 ft. long, the wooden dam of Fig. 144 is strengthened by a dry wall of roof slate, 3 to 5 ft. thick, laid above the plank ab. By slow flushing at first, this dry wall gets packed solid and keeps the plank from bulging under the heavy final pressure due to a vertical water head of 90 ft. FLUSHING SYSTEMS FOR FILLING SEAMS 115 A room in the Dodson mine in the 22-ft. Red Ash seam was worked in two slices, the first taking only 8 ft. of coal from the floor. When preparing for flushing, the upper 14-ft. slice of coal was not taken down over the neck for 24 ft. from the room's lower end, so that the subsequent wooden dam needed to be only 8 ft. high. Holes are bored into the plank of the dams near the top, if necessary, to let the overflow water escape, but a better arrangement for steep dips is a wooden drain-launder bk laid on the floor up through the dam into the room. The top m of the cover of launder bk is kept a short distance above the top of the settled slush at n by adding new cover-boards as the filling rises. The overflow water then runs over into the launder at m and descends into the gang- way ditch at g to flow to the sump; whence it is pumped to the surface, where, being acid, it is not reused unless fresh water is scarce. At the Dorrance mine where the rooms were being filled on the advance by extending the flushing pipe from one panel of ten rooms to the next, it was the practice to give each panel another dose of slush, while with- drawing the pipe, in order to close up the many spaces between the settled slush and the roof that had developed since the advance. For nearly flat seams, dams are built in the openings all around a panel of rooms, and the end of the flushing pipe shifted around inside the panel, close to the roof, so as to fill all portions equally. More or less methane is given off if the slush is exposed to air currents, but these are feebler, the smaller the spaces left between slush and roof. As another safeguard against gas, the filled panels are connected with the return airways of the active mine. In the considerable areas where a subsidence of the surface is imma- terial, the anthracite seams are best worked to the boundary, by that pillar system of the last chapter most appropriate to the given conditions; and the pillars then recovered on the retreat, allowing the roof to fall. Under the river flats where roof-falls might cause a crack up to the surface and flood the workings, one company's mines are laid out with permanent pillars of a size just sufficient to sustain the roof indefinitely, which means 16-ft. pillars and 24-ft. rooms for depths of less than 400 ft. Flushing as a preliminary to pillar-drawing is beneficial in the anthra- cite region under two conditions. First, where the workings are overlaid by virgin parallel seams, and second, where they are overlaid by townsites. Former market conditions made the thin seams unpayable, so that the proper method of exhausting overlying coal seams from the top down- ward was not applied. Now the pillars can only be recovered from the lower seams, without wrecking those above, by a preliminary filling of the adjoining rooms. Formerly, it was not thought that the pillars left under townsites would ever be worth recovering, but higher coal prices have made them valuable and filling must precede their recovery. The aforementioned Scranton commission recommends that as slush 116 MINING WITHOUT TIMBER alone has insufficient crushing resistance for thick covers, sand should be used for filling under Scranton at depths beyond 500 ft. Also that filling should begin in the lowest seam of the series and continue upward until all are filled, care being taken to have the flushed areas over one another. After all the openings in all the seams have been filled, the pillars in the top seam may be removed and replaced at once by filling. The next seam below may not be attacked and handled in like manner until the pillars above, within a large panel, are removed and the over- burden has come to rest on the new filling. In this manner several parallel seams could be robbed of pillars simultaneously, by panels retreating in vertical echelon, the robbing in the highest seam being farthest from, and that in the lowest seam nearest to the boundary. In some mines with irregular layouts and small pillars, the formation had moved considerable before flushing was inaugurated. Thus in the 22-ft. Red Ash vein of the Dodson mine at Plymouth, the overlying formation moved so freely that gangways could only be kept open by using heavy timbers and brushing the floor. While in the Black Diamond mine at Luzerne, the walls of the 6-ft. Cooper seam were distorted with frequent roof-falls, and in the 8-ft. Bennett seam the roof had bent enough to badly squeeze many of the pillars. The seams of the latter mine, which were excavated on the system of Fig. 130, dip about 10 deg. and the pillars of the flushed portion are now being robbed and replaced by slush. Where pillars are 20 ft. wide, or more, an 8-ft. heading is driven on one side of the pillar on the rise, often leaving a thin shell of coal next to the filling. Then, when the airway above is reached, the balance of the pillar is drawn on the retreat. The advance heading must be well propped, but the timber is mostly recov- ered on the retreat and, owing to the moving formation, the pillar coal is so squeezed that but little blasting is necessary. Too much roof pres- sure sometimes so crushes the coal that it falls to powder when extracted. The Dorrance mine is under a suburb of Wilkesbarre and the policy of the owner, the Lehigh Coal Company, is to refrain from taking all the pillar coal, when robbing flushed areas under cities, because an unsup- ported cover will settle down at least 10 per cent, of the coal's thickness; and with flat seams, where filling close to the roof is impractical, the sub- sidence may be 20 per cent. In fact, the surface in some cases has sub- sided less from robbing pillars in open than in filled seams; for in the former case local breaks of roof may fill up the rooms with boulders and support the cover, while robbing pillars completely in the latter case starts the whole cover to subsiding as in the longwall system. The flushed workings observed in the Dorrance mine were on a dip of 18 deg. and on a layout like Fig. 130 with rooms 20 ft. and pillars 40 ft. wide. A heading was first driven up in the pillar, to slab off 18 ft. of coal alongside the filling, and on the retreat from the room 's upper end FLUSHING SYSTEMS FOR FILLING SEAMS 117 a 24-ft. cross-cut was put through the pillar, halfway between the original 12-ft. break-throughs, 100 ft. apart. Thus after flushing the new pillar openings, the roof was left supported by a line of coal pillars 22 feet wide by 32 ft. along the dip. Under Mahonoy City, the 22-ft. Mammoth seam, dipping 55 to 60 deg., is being worked in two slices by a system like that of Fig. 131. The lower slice of 15 ft. is taken out in the room on the advance and the upper 7-ft. slice allowed to fall into the chute, by pulling the props, on the retreat. After flushing, the pillar is taken out, likewise, in two slices, by driving a heading through its center, leaving only a thin shell of coal on each side to keep out the room-filling. The entry pillars are drawn on the retreat, and all the new openings are flushed. In spite of this extraction of practically all the pillars, the surface here is stable, for with seams of steep dip, the subsidence upon the filling is not so serious as it is in the case of the flatter seams under Wilkesbarre. As already mentioned, the 22-ft. seam in the Dodson mine is also worked in two slices but with the thin slice below. The pillars here are 26 ft. and the room is 24 ft. wide. The lower slice of both room and pillar is mined on the advance and the upper slice is recovered on the retreat as described in the last paragraph, except that the layout follows Fig. 130 to suit the 12-deg. dip. EXAMPLE 60. ROBINSON GOLD MINE, RAND DISTRICT. TRANSVAAL Parallel Sloping Beds Filled with Mill Tailing In spite of the extensive areas excavated since 1885 in the conglom- erate of the Rand, but little filling has yet been done. At a few rich outcrop mines, it is true, the rooms were packed with rock to enable the pillars to be recovered. But packing is too costly a method for most of the area. As the mines reach depths exceeding 4000 ft., the former sized pillars are proving too small, and several unexpected collapses have occurred. Recently the flushing system has been tried with suc- cess at the Robinson mine, to permit of the removal of some rich pillars just under the stamp mill, in the following manner. The tailing is washed from the dump by a 1-in. water pipe into a launder, 6 in. sq., which runs to the top of a winze. Here the pulp enters a similar launder which descends along the 40- to 50-deg. dip of the seam floor to the ninth level of the mine. The stope to be filled has been dammed at the lower end by a dry wall W, see Fig. 145, strengthened by poles P, and similar partition walls are built at right angles to cut it up into longitudinal panels. The fine waste B is piled above W, and covered with old matting M from the cyanide tanks. When flushing begins, the sand settles quickly, the water filters through the matting and dams, whence it runs to the sump to be pumped to the surface. 118 MINING WITHOUT TIMBER This water is used again after a little lime has been added to neu- tralize its acidity and render any entrained colloids harmless to hinder a quick settling. To save water, the launders are kept on a minimum gradient of 10 deg. The water used is 6 to 10 per cent, of the tailing by weight. The cost of filling is given at 2.1 d per ton, but as only 100 tons of tailing are sent underground daily, this probably does not include wear of the launders. The filling sets hard in 2 or 3 days. When a stope is completely filled, it only settles 10 per cent, of its height when crushed by the formation after the pillars have been removed. The residual cyanide of the tailing leaving the mill has been destroyed by exposure on the old dumps, so that no poisonous results have so far ensued from using tailing as mine filling. In order to utilize fresh tailing, the cyanide must first be rendered innocuous. This is not Fid. 145. Dam for holding slush, TransvaaL urgent at present, because the old tailing dumps are immense. Flushing the leading vats direct into the mine, however, would save the expense of conveying the tailing to the top of the very high dumps and of redig- ging it before flushing. Hence some mines are now getting ready for direct flushing. The flushing system is now being freely used in the Rand to fill stopes not under buildings, in order to prevent the damage to the workings and the shaft pillars which is liable to ensue from pillar-drawing, especially as the mines get deeper. The rock tailing available for filling is much more resistant to crushing than the anthracite refuse of Example 59, and is strong enough for a filling at any workable depth. On the central Rand, there are two contiguous parallel beds, the Main Reef below, and the Main Reef Reader above, separated by a thin rock parting. As the Main Reef is the leaner, it has hitherto been neglected in many mines, but it is expected that the flushing system will now greatly facilitate its extraction under the worked-out stopes of the Main Reef Leader. INDEX Adits, 58-59 Advancing system, 63, 72, 70, 79, 84, 89, 94 retreating system, 04, 100, 106 Africa, 41, 63, 117 Air, compressed, 29-32 drill. See Drill. fresh. See Ventilation. Altofts Colliery, Eng., 67 Amvis, 16 Anthracite district, Pa., 43, 55, 60, 110 Appalachian beds, 63 * Bacon, Roger, 7 Barriers. See Dams. Black Diamond Mine, Pa., 1 Blasting, calculations, 18 massive rock, 20 seams, 26, 87 stratified rock, 21-24 Bobbinite, 8 Boyles law, 5 Brattices, 97-101 Breaker, coal, 110 Breast-stoping, 26, 77 Brushing. See Roof. Buggies Mine, 81, 96 Bulls Head Colliery, Pa., 79 Bureau County, 111., 117 Butte, Mont., 26, 31, 39 Calumet and Hecla Mine, Mich., 54 Caps, blasting, 2, 15 Carbonite, 16 Cars, coal, 74, 85, 93, 98 Cartridge, 3 Charles' law, 5 Chocks. See Cribs. Chutes, loading, 78, 96 Cleaning. See Coal and Sorting. Cleavage, 25, 65, 84, 103 Clod, 35 Coal breaker, 110 commission, 69, 110 cutting, hand, 09, 74, 82, 86, 100 machine, 26, 66, 87, 92, 100, 106, 109 mining, 20, 35, 41, 43, 02-70, 79-117 Cogs. See Cribs. Colliery. See Coal. Comparison systems, 119-127 Connellsville district, Pa., 102 Continental Mine, Pa., 105 Continuous-face. See Longwall. Conveyers, 84, 112 Creep, 40, 75, 101 Cribs, 75, 82, 88, 90 Cripple Creek, Colo., 28, 59 Culm, 110, 112. Dams, artificial, 55, 01 deposition, 58 natural, 56, 114, 115, 117 Danville Mines, Pa., 76 Delaware & Hudson Coal Co., Pa., 110 D. L. & W. Coal Co., Pa., 110 Development, mine, 20 Dip-working of seams, 70 Dodson Colliery, Pa., 112, 115, 117 Dowance Colliery, Pa., 114, 115, 116 Drainage, calculating, 47 massive rock, 53 Drainage, stratified rock, 52, 64, 76, 90. See also Adits, Pumps and Water. Drill, air-hammer, 21, 24 pointing, 20-27 prospecting, 64, 113 Drummond Colliery, N. S., 89 Drywalling, 70, 75, 77, 80, 82, 114, 117 Dust, 26, 64 Dynamites, 13. See also Blasting. Electric blasting, 19, 28 exploders, 2 power, 86. See also Haulage. England, 41, 67, 69, 84 European Mines, 03, 89, 110 Explosions, mine, 64, 108 Explosives, calculating, 4 chemical, 8 detonating, 2 igniting, 1 loading, 3 mechanical, 7 chemical, 12. See also Blasting, Electric, Powder. Fayal rules, 34, 41 Filling seams, 75, 78, 82, 88, 100, 109, 117 Flowage rock, 46 Flushing pipe, 113 slush, 112, 117, 118 system, 110, 117. See also Filling and Roof. Forcite, 14 Fracture. See Roof. Frick Coke Co., Pa., 106 Fulminates, 11, 14 Fuse, 2. See also Blasting. G Gas, 64, 76, 91, 115 Gelignite, 14 Geneva, N. Y., 49 Gobbing. See Filling. Grundy County, 111., 72 Gulf of Mexico, 49 Guncotton, 12 Haulage, air, 32 animal, 64, 74, 80, 93, 102 electric, 98, 102 endless rope, 81 tail rope, 93 Hausse formulse, 42 Hazen formula, 51 Hazleton, Pa., 110 Headings, driving, 20-24 Hoisting coal, 87, 93 Horn Silver Mine, Utah, 58 Hudson River tunnels, 35 Illinois, 72 Inclines. See Jigs and Slopes. Intercoolers, 30, 32 Iowa, 49 Iron Mountain Mine, Mont., 55 119 Jeddo-Basin adit, Pa., 60 Jeffrey Mfg. Co., Ohio, 87, 112 120 Jigs, haulage, 93, 90, 97 Joplin District, Mo., 26 Joveite, 12 Kirby, E. B., 58 Labor, coal mine, 63, 76, 82, 87, 99, 100 Lake-basins, 50, 57 Lake Superior, 24 La Salle County, 111., 72 Launders, 112, 117 Lausanne adit, Pa., 60 Lehigh Valley Coal Co., Pa., 43, 55, 110, 116 Leyner drill, 21 Locomotives. See Haulage. Longwall system, 63, 66, 72, 76, 84, 89 Luzerne, Pa., 116 Lyddite, 12 M Mahanoy City, Pa., 117 Maps. See Surveys. Merriman formulae, 58 Misfires, 16 Missouri, 26 Monongahela River Coal Co., Pa., 106 Montour Mines, Pa., 76 Multi-charging, 25 N Nelms, H. J., 96, 100 Newhouse adit, Colo., 60 Nitro-benzol, 15 -gelatine, 11 -glycerine, 9 Nytryl, 8 Nobel, Alfred, 9, 11, 13 INDEX o Oil well. See Wells. Oneida adit, Pa., 60 Overhand stoping, 28 Pack-walls. See Drywalling. '-system, longwall, 62, 79, pillar, 96, 100, 103 Panel- 110 Pardee Colliery, Pa., 110 Pendleton Colliery, Eng., 67 Percolation. See Water. Philadelphia & Reading Coal Co., Pa Picrates, 12 Pillar and stall. See Stall. -drawing, seams, 95, 98, 104, 105, 107, 109, 116 -placing' 43, 72 -system, seams, 62, 80, 89, 94, 96, 98, 101, 102, 106, 115 Piping, 32, 61, 113, 116 Pittsburgh seam, Pa., 102, 106 Plymouth Coal Co., Pa., 110, 112 Porter locomotives, 32 Portland Mine, Colo., 28 Potentite, 13 Powder, black, 7 permissible, 8, 16 smokeless, 12 Preheater, 31 Prop-puller, 105 Providence, Pa., 79 Pumping, 31, 50, 61, 112 R Raokarock, 18 Railroad. See Haulage, Cars, Track and Tunnels. Rainfall, 15 Receiver, air, 32 Rectang, longwall, 73 Resistance, line of least, 18 Retreating systems, seams, 63, 98, 102, 106 Richardson formula, 42 Rise-working, seams, 69 Roburite, 16 Roof-brushing 75, 76' 90 -control, flat, 33-37, 65, 77 inclined, 38, 84 -pressure, 65-71, 75, 82, 93 -subsidence, 40, 41, 46, 63,65, 75, 103, 106, 107, 109, 116, 118 Room and pillar. See Pillar. Roosevelt adit, Colo., 59 Run-off. See Water. S Scotch longwall, 72 Scranton, Pa., WO Seams, mining. See Advancing, Blasting, Coal, Longwall Panel, Pillar, Retreating Roo*. Slicing. overlaying, 43, 115, 118 recovery of, 64, 69, 94, 106, 108, 110 Shafts, 43, 64, 72 Shops, 72 Siphons, 60 Skips, 61 Slicing system, 117 Slopes, 80, 89 Slush. See Flushing. Sprengel explosives, 15 Spring Valley Collieries, 111., 72 Squeeze, 40, 64, 96, 98, 109 Squibs, 1 Stables, 95 Stall and pillar, 62, 97 Stepped-face. See Longwall. Stoping, 24-27 Subsidence. See Roof. Sunderland, Eng., 41 Support, ground. See Roof, Drywulling and Timbering. Surface support, 43, 115 Surveys, 99, 101 Tamping, 3 Timbering, seams, 75, 78, 87, 103 Tonite, 3 Top-slicing. ' See Slicing. Track, coal, 81, 93, 96, 103, 105 Transvaal, 41, 63, 117 Tunnels, blast, 27 railroad, 34, 35 U Unwatering. See Drainage. V Ventilation, seams, 63, 64, 80, 86, 91, 95, 96, 100, 101, 108 Vinton Colliery, Pa., 84 Walls. See Drywalling. Water, diversion, 58, 58A. evaporation, 49 percolation, 50 run-off, 49 supply, 47. WeiKel, Martin, 7 Wells, 10, 51 Westfalit, 16 Westville, N. S., 89 Wilkes-Barre, Pa., 110, 116, 117 Williams pulverizer, 113 Winches, 81, 82 Zones, flowage and fracture, 46 PRACTICAL SHAFT SINKING BY FRANCIS DONALDSON, M. E. COPYRIGHT, 1910, 1912, BY THE MCGRAW-HILL BOOK COMPANY, INC. PREFACE TO THE FIRST EDITION THE subject matter of this book was published as a series of articles in Mines and Minerals, during 1909 and 1910. It is reproduced, with some alterations and addi- tions, through the courtesy of Mr. Rufus J. Foster, manager, and Mr. Eugene B. Wilson, editor of Mines and Minerals. The writer also wishes to acknowledge his indebtedness to Mr. H. H. Stock, who was editor of Mines and Minerals when most of the articles came out. September, 1910. PREFACE TO SECOND EDITION SINCE the text of the first edition of "Practical Shaft Sinking" was written, cement grout has been used in several American shafts to cut off flows of water encountered in sinking, and its further use for this purpose will undoubtedly become more common. The writer, therefore, believes that a description of the methods used in grouting off flows of water in two of the city aqueduct shafts (Catskill Aqueduct Project) will make an interesting appendix. Such a de- scription is given in Appendix A. It will be noted that in one of these shafts a stratum of loose sand prevented the entire exclusion of the water by grouting alone, that a concrete lining provided with drain pipes was placed, and that the shaft was finally made entirely dry by grouting this lining. Several of the city aqueduct shafts in Brooklyn and the lower east side of Manhattan Island were sunk through great depths of water-bearing sand by the pneumatic cais- son process. A section of one of these caissons, accompanied iv PREFACE by a description of the methods used in sinking it and seal- ing it to the rock, is shown in Appendix B. One change has been made in the shaft records on page 83 to accommodate a new American record. Several foot- notes have also been added, and one or two typographical errors corrected. CONTENTS CHAPTER PAGB PREFACE jjj I SOME DEEP SHAFTS FEATURES OF CONTRACTS FOR SINKING FORM OF CONTRACT 1 II PLANT REQUIRED BOILERS, HOISTING ENGINES, HEAD-FRAME AND BUCKET AIR COMPRESSORS 16 III SINKING THROUGH SURFACE SOFT GROUND WOODEN SHEET- ING STEEL SHEETING CAISSONS OF STEEL, WOOD, OR CONCRETE , . . ' 33 IV SINKING THROUGH SOFT GROUND PNEUMATIC PROCESS SHIELD METHOD 59 V SINKING IN ROCK ARRANGEMENT OF HOLES TOOLS AND METHODS USED IN DRILLING COSTS AND SPEED ... 66 VI THE SINKING-DRUM PROCESS MAMMOTH PUMP THE FREEZ- ING PROCESS 85 VII THE KIND-CHAUDRON BORING PROCESS CEMENTATION OF WATER-BEARING FISSURES . . . . 97 VIII LIFTING WATER HORIZONTAL vs. VERTICAL PUMPS HAND- LING PUMPS IN SHAFT CORNISH PUMPS . . . . . . 107 IX SHAFT LININGS '..... 118 X CONCRETE LININGS COSTS PER LINEAR FOOT FOR RECTANGU- LAR ELLIPTICAn, AND QUADRILATERAL SHAFTS 129 APPENDIX A. GROUTING SHAFTS 4 AND 24, N.Y. CITY AQUEDUCT 140 B. .....' 144 PRACTICAL SHAFT SINKING CHAPTER I SOME DEEP SHAFTS FEATURES OF CONTRACTS FOR SINKING FORM OF CONTRACT THE origin of mining is lost in the mists of antiquity, but it is certain that, since the beginning of history, metals and minerals have been sought after. The Egyptians operated gold, silver, and copper mines in Ethiopia and on the Arabian border; the Phoenicians found gold and iron in the islands of the Mediterranean and lead and silver in Spain. The earliest mines were probably surface work- ings, but the first historical mention of openings driven in the earth refers not to a drift or tunnel but to a shaft. In the Book of Job it is written of man that "He breaketh open a shaft away from where men sojourn; they are for- gotten of the foot; they hang afar from men; they swing to and fro." Pliny describes cutting hitches in a shaft: "Else- where pathless rocks are cut away and are hollowed out to furnish a rest for beams. He who cuts is suspended with ropes." Shaft sinking and tunnel operations in ancient times were confined to solid earth and rock. The Roman engi- neers drove rock tunnels that would seem long to-day; they originated the method of disintegrating rock by fire and they sunk shafts along the line of their tunnels from which to drive additional headings. Forty shafts one of them 400 ft. deep were used for the excavation of their longest tunnel. For many centuries after the Roman Era nothing com- parable to the Roman work was attempted, since the cost in labor and human life of the fire-and-water method was i 2 PRACTICAL SHAFT SINKING terrific. The invention of gunpowder was the next step, but gunpowder was apparently not used for blasting purposes until 1679, at Malpas, France. Mines in the Hartz Moun- tains and in Cornwall had been worked to great depths in the seventeenth century before the steam engine was developed, but its application to hoisting of course made possible undreamed of speed in sinking. The first practical use of steam was, incidentally, to pump water from the Cor- nish shafts. The invention of dynamite, the first commercial high explosive, in 1866, and the compressed-air drill in 1855, put rock shaft sinking on its present basis. Although from time to time special methods such as the freezing and the boring processes have been developed for special conditions, for ordinary shafts hand sinking is cheapest and best. Excepting the steam hoist, inventions have been confined to means for shattering the rock; steam shovels are some- times used in tunnels, but shaft spoil is to-day loaded by hand into buckets, as in the days of the Romans. Before the last half of the nineteenth century, soft- ground sinking was confined to material penetrable by fore- poling. Although considerable depths have been reached in this way, where the ground is bad the method is at best slow and precarious. The Germans originated the hydrau- lically forced sinking drum and the freezing process. The pneumatic process was first used by Brunei in the Thames Tunnel. Recently, concrete sinking drums or open caissons have been extensively used. The sizes and shapes of shafts are governed by the nature of the material to be hoisted through them, by the char- acter of the ground to be penetrated, and also largely by local usage. Since mine cars and skips are approximately rect- angular in plan, a rectangle is the most economical shape for a hoist shaft, giving the maximum usable area with the minimum excavation; this advantage, however, does not apply to an air shaft. The rectangular shape is also adapted to timbering, the cheapest form of lining, and is on this SOME DEEP SHAFTS 3 account standard in America. In Europe, on the . other hand, all shafts are circular or elliptical and are lined with brick or concrete masonry. This type has the disadvantage of high first cost, but a masonry lining is proof against decay and fire and explosions. In wet strata also, a circular shaft may be lined with iron tubbing and thus kept entirely dry. In large mines two openings are always advisable to secure satisfactory ventilation; in coal mines where explo- sive gases form they are absolutely necessary, and in most states are required by law. The hoist shaft may be upcast or downcast; in either case an airway is usually provided in addition to the hoist compartments. All mines worthy of the name have balanced cages requiring two hoistways; the airway makes a three-compartment shaft the most common type. In rectangular shafts, where several com- partments are needed, a long shaft one compartment wide is easier to sink and timber than a short shaft two com- partments wide; for instance, if four 7 X 10 ft. compart- ments are desired, a shaft 10 X 28 ft. is preferable to one 20 X 14 ft. In America, in the bituminous coal fields, hoist shafts are usually 13 X 26 ft. in the rock, are lined with 8 X 10 in. timber and have two 7 X 11 ft. hoistways and a 9 X 11 ft. airway. In wet mines a 5-ft. pipeway is added. The air shafts are 13 X 18 ft., with a 10 X 11 ft. airway and a 6-ft. stairway compartment. In the anthracite fields the deeper hoist shafts sometimes have four hoistways operating from several coal seams, besides air and pipe ways, and have sections 12 X 42 ft. to 14 X 56 ft. in the rock. European coal shafts are customarily 20 to 23 ft. in finished diameter. Coal shafts are almost always vertical. In ore mines different conditions prevail. Ore is less bulky than coal, is harder to mine, and can be loaded through chutes without objectionable breakage. Large shafts are therefore unnecessary and the sizes range from 7 X 9 ft. in the iron mines formerly operated at Boyertown, Pa., 4 PRACTICAL SHAFT SINKING to .9 X 24 ft. in the Michigan iron country. Ore shafts are usually sunk on the vein, and so may be found at any inclination with the vertical, but where natural conditions do not compel an inclination, a perpendicular shaft is preferable. The deepest shaft in America, No. 3 Tamarack at Tama- rack, Mich., is 5253 ft. deep and is used in mining copper. No. 5 shaft at Tamarack is 5180 ft. deep, Red Jacket shaft at Calumet, Mich., is 4900 ft. deep. These shafts are remarkable not only because they penetrate the earth for almost a mile, but also because of the remarkably powerful hoisting engines used engines which hoist a total load of 17 tons at the rate of 6000 ft. per minute. All of these shafts are vertical. In the Pennsylvania anthracite fields, where acid mine water quickly eats up pumps and piping, a number of shafts have been sunk for the purpose of hoisting water. The tanks used for hoisting fill and empty themselves auto- matically, discharging the water into a basin at the top of the shaft. Powerful hoist engines are provided. The most notable shaft of this type is owned by the D. L. & W. R. R., at Scranton, Pa. It is entirely automatic, requiring no engineer, and is operated through friction clutches by an 800-horse-power induction motor. The driving of rock shafts and tunnels is very unlike the mining of coal; a different class of workmen, different fore- men, and different tools are needed. It is seldom that a good coal-mine foreman is also a good sinker, and good sinkers, unattached, are not always easy to obtain. For these reasons it is customary for coal-mining companies to have a large part of their development work done by con- tract, and even the large anthracite corporations, who own the necessary surface equipment for sinking, prefer to have contractors do the sinking. In ore mines the foregoing does not apply; sinking shafts is part of the day's work and all the miners are rock men, but in opening a new mine the question of time is still to be considered. The loss of DISPOSAL OF SOIL 5 interest on the investment in a large property before it is developed may amount to several hundred dollars a day, and every day lost in sinking adds that much to the cost of the shaft. Even when a mining company is so situated that it can sink its shaft cheaply, a responsible contractor possessing a plant and an organization can save enough time to more than pay his profit. When it is decided to have a shaft sunk by contract, the first essential is to get trustworthy contractors to bid on the job; the second is to prepare a contract fair to both sides. While it is not well to leave loopholes whereby the contractor can escape from the plain provisions of the speci- fications, it is equally unwise to attempt to tie him down so tight in every detail that he is practically dared to find a flaw in the agreement. It is almost impossible to foresee every contingency, and an omission in a very tightly-drawn contract is harder to correct subsequently than an omission in a looser one. A complete shaft contract form may be found in several text-books, or obtained elsewhere without difficulty; a form in common use is appended to this chapter. Among the specific points that warrant attention may be mentioned the following: Disposal of Spoil. The labor cost of a shaft is of course directly affected by the nature of the dump. It is also indirectly affected by it to an even greater extent. The delays to sinking caused by a long haul and an incon- venient dump, especially in bad weather, are likely to be more serious than the cost of the additional labor required. The specifications should, therefore, state where the spoil is to be dumped, or at least where it is not to be dumped. In one case where a contract contained the usual clause, "the spoil shall be placed where the engineer shall direct, the haul not to exceed 1500 ft.," no plans were available, and in the absence of any direct prohibition by the engineer, the con- tractor started to dump spoil in the vicinity of the shaft. After three months' sinking, the engineer discovered that 6 PRACTICAL SHAFT SINKING the dump was in his way and directed that the spoil be placed elsewhere. Subsequently he compelled the contrac- tor, under the clause cited above, to move all the spoil dumped in the first three months. While in this case the engineer's order might have been successfully contested, much trouble could have been saved by proper care in drawing up the contract. Time Limit and Penalty. A time-limit clause is most properly a feature of nearly all sinking contracts, and the usual provision made to secure its enforcement is, "and in the event of the contractor failing to complete the work by this date, it is mutually agreed that he shall pay the con- tractee the sum of - - dollars for every day thereafter until the work is completed, not as a penalty, but as liqui- dated damages." In spite of this definition, the courts have often held that the actual damages must be proven and the possibility of collecting the stated damages is not assured. Since the real damages to a mining company due to delay in getting started consist of the loss of interest on the invest- ment, in every case where the company has its surface arrangements ready for work before its shafts are finished, it will gain as much per day by their completion ahead of time as it will lose by their non-completion. The writer therefore believes that where a penalty is to be collected for delay an equal premium should be paid for time saved, not only because this is fair but also because it is likely to expedite the work. An extension of time is usually, and should be, allowed the contractor on account of " unusual difficulties with water or quicksand." Acceptance. Where two shafts are sunk simultaneously under the same contract (as in opening a new coal mine), the first shaft down is usually accepted by the company upon completion. If this is not the intention it should be so stated in the contract. Risk of Water. It has been the practice in shaft con- tracts to throw the risk of encountering unusual quantities of water upon the contractor. With a fixed price per foot SUPPLIES AND MACHINERY 7 for sinking, based upon usual conditions, the contractor will lose money if he strikes water exceeding, say, 150 gallons per minute. With greater quantities his loss is often measured only by his financial resources. This puts a responsible contractor at a disadvantage, especially in a new territory, for since he has the equipment and the money needed to fight large quantities of water, he must raise his price on all shafts to insure him against an occasional heavy loss. An irresponsible contractor, on the other hand, having little to lose, can afford to bid low, and if he does strike much water abandon the job. The water risk belongs properly not to the contractor nor the mine owners in general, but to the owners of the particular mine in question ; for this reason a water clause is a feature of many recent contracts. The New York Board of Water Supply, in its. contracts for the construction of the inverted siphons on the Catskill aque- duct, calls for a price for pumping each million gallons of water 1 ft. In these jobs the time schedules are so carefully worked out that there is little likelihood of the contractor pumping water for profit, but a form of water clause more acceptable to the average mining company is one in which the contractor makes an additional price per foot for every hundred gallons per minute pumped while sinking. He is thus paid nothing if the shaft is idle and is encouraged to make progress. Supplies and Machinery. Local conditions determine whether the mining company or the contractor should furnish the supplies or machinery. The larger anthracite companies, who hold extensive properties and open new mines upon them as the need arises, own sinking engines, boilers, and other equipment; at a new shaft they erect a surface plant complete, furnish timber and coal, and expect the contractor to supply only the air compressor and drills, small tools, and labor. In the bituminous fields and in many ore regions, the mining companies usually wish to develop new property as soon as it is acquired, and, in order to concentrate their efforts upon the permanent surface 8 PRACTICAL SHAFT SINKING plant, expect the shaft contractor to furnish everything he needs. A quicker start can be made in this way. If the shaft is to be timbered, however, the timber should be furnished by the company. Oak suitable for shaft linings is rapidly becoming unobtainable; yellow pine must be brought long distances and is not likely to arrive too soon if ordered when the shaft contract is let. Aside from the question of speed, the company by supplying timber will save itself the profit that the contractor adds to cost, and also occasional vexatious squabbles as to quality. No matter how the shaft is sunk the permanent boiler plant should be made ready to operate as soon as is prac- ticable. The possibility of striking water is the greatest hazard of sinking and, if water is encountered, the first requirement is* plenty of steam. It is easier and quicker to procure and install any amount of pipe and any number of pumps than it is to build a boiler plant to run the pumps. Effective sinking pumps are so exceedingly wasteful of steam that the permanent mine boiler plant will be none too large and efficient to care for a large inflow of water; its early completion will insure against a long and costly delay. The local flow of underground water is one of the most uncertain features of geology, and whether or not water will be encountered in a given shaft can seldom be predicted with certainty. Even when borings at the site of a shaft or other shafts sunk in the vicinity indicate that water will be struck, the amount is problematical. A few general remarks may be stated as follows: Since the rainfall in mountains is high, the ground near them will have an opportunity to collect water. Geologic faults form passages whereby surface water finds its w r ay into the ground, and the fissures caused by the strain to which the rock was subjected when the fault was made act as reservoirs. A shaft on or near a fault is sure to be wet below the ground-water level of the surrounding region. Natural water courses also form in soluble rock such as sandstone and limestone, especially the latter. An example SOME DEEP SHAFTS 9 of a water course of this kind was afforded at the zinc mine at Friedensville, Pa., formerly drained by the " President," the largest Cornish pump ever built. This mine is located at the foot of a mountain. Two shafts sunk in the' Allegheny Mountains near South Fork, Pa., also encountered a water course. They were about 250 ft. apart and apparently were sunk directly on top of the water channel. What may be called the down- stream shaft was sunk first through the wet stratum; as the up-stream shaft was sunk the flow into it increased, while the flow into the down-stream shaft decreased at the same rate. Shafts near streams are likely to strike water at the sur- face of the rock, but not necessarily below it if the rock is solid. In ordinary coal measures a feeder may be expected at the seam between an upper permeable rock like sandstone, and a lower bed of impervious shale or fireclay. The uses of the diamond drill in prospecting for coal and ore are too well known to require comment, as far as the knowledge obtained of the rock is concerned. A hole near a proposed shaft will also give much information as to the ground-water conditions, even though, as has been said, the quantity cannot be determined. A diamond drill hole is not large enough to pump out, but the process may be reversed. If additional water can be pumped into a hole already full, the strata are evidently open enough to let water into a shaft. A bore hole, of course, may be pumped with a deep-well pump or air lift; it has in fact been suggested that wet ground be drained by pumping from a ring of bore holes around the shaft location, thus doing away entirely with pumps in the shaft. Prospect holes should be located at one side of the shaft, so that if a pocket of water is drilled into at a considerable depth, it will not rise into the shaft through the hole. In this way pumps and piping need not be installed until the bottom of the shaft has almost reached the level of the pocket, and the depth of the wet sinking is reduced to a minimum. 10 PRACTICAL SHAFT SINKING CONTRACT AGREEMENT FOR SHAFT SINKING This agreement made in duplicate this day of by and between the Coal Co., a corporation chartered and existing under the laws of the State of party of the first part, and the Con- tracting Co., a corporation chartered and existing under the laws of the State of , party of the second part, WITNESSETH, That for and in consideration of the cove- nants and payments hereinafter specified to be made and per- formed by the party of the first part, the said party of the second part doth hereby covenant and agree to build and complete in the most substantial and workmanlike manner, a hoisting shaft 13 X 26 ft., outside the timbers, and an air shaft 13 X 18 ft., outside the timbers, each approximately 600 ft. deep, for the Coal Co., at its property near . The work is to be done in accordance with the attached specifications and the plans furnished by the party of the first part, which are hereby made a part of this agree- ment; the party of the second part is to furnish all the labor and materials necessary, except such as are particularly noted in the specifications as being furnished by party of the first part. The said work is to be completed on or before the first day of , 19 . And the party of the first part doth promise and agree to pay the party of the second part the following prices for the several kinds of work herein specified, of which the 'following is a summary: HOIST SHAFT Excavation measured from top of natural ground to bottom of coal seam $ per vert. ft. Framing and placing all timber and lagging $ per vert. ft. Water rings complete $ each. AIR SHAFT Same as above. CONTRACT AND SPECIFICATIONS 11 The above prices contemplate a maximum of not more than 100 gallons of water per minute to be pumped from each shaft. The following extra prices will be paid in each shaft for each 100 gallons per minute in excess of this amount, as follows : Water Pumped; Additional Price Gallons per Min. Paid per Foot 100 - 200 $ 15 200 - 300 30 300 - 400 45 400 - 500 60 500 - 600 75 600 - 700 90 700 - 800 110 800 - 900 130 900 - 1000 150 If the volume of water should exceed 1,000 gallons per minute, a supplementary agreement will be made. The payment for said work shall be made in the following manner : An estimate will be made about the last day of every month of the amount of work done during the month, and 90 per cent, of the same will be paid on or before the 20th of the succeeding month, 10 per cent, of the total amount being retained until the entire completion of the work. And when all the work embraced in this contract is completed, the party of the first part shall, upon notification from the party of the second part, make a final inspection; if the work is found to be in accordance with the specifica- tions, there shall be a final estimate made of the value of said work, according to the terms of this agreement. The balance due the party of the second part shall be paid within thirty days thereafter, upon said contractor giving a release under seal to the party of the first part from all claims or demands whatsoever growing in any manner out of this agreement; and upon said contractor delivering to party of the first part full release in proper form and duly executed of all liens, claims, or demands from mechanics 12 PRACTICAL SHAFT SINKING and material men for work done on or about the shafts, or for materials furnished for the work under this contract. It is further agreed between said parties that said party of the second part shall not transfer or sublet any part of this contract to any person (except for delivery of materials) without the consent of the party of the first part, and that the party of the second part will at all times give personal attention to the superintendence of the work. It is further agreed that the work embraced in this contract shall be commenced within two (2) weeks of the date of this contract and prosecuted day and night (except Sundays) with as many men as can be worked to advantage. If, during the progress of the work, it is the opinion of the Engineer of the party of the first part that the party of the second part is not furnishing materials or appliances or labor of the right quality, or in sufficient quantity to complete the work within the time agreed on, the said Engineer may in either or both of the above-mentioned cases purchase such material and appliances or employ such labor as in his judgment may be necessary. And the said Engineer is authorized to pay such wages for labor and such prices for materials and appliances as may be found necessary or expedient, and to deduct the amount so paid from any moneys due the party of the second part from the party of the first part. It is further agreed that the Engineer shall have the authority to order any additional work or materials not called for in the plans and specifications that he may deem necessary or advisable, but in case any such extra work or materials is required, the same shall be ordered by the Engineer in writing, and the price for said extra work or materials shall mutually be agreed upon in writing before said materials are furnished or said work is done. IN WITNESS WHEREOF the parties herein have hereunto set their hands and seals, the day and date first above mentioned. CONTRACT AND SPECIFICATIONS 13 SPECIFICATIONS FOR SINKING AND LINING Two SHAFTS FOR THE COAL COMPANY, AT GENERAL Meaning of Titles. The word Contractor, when here- inafter used, shall refer to the Contracting Company as in the attached Agreement. The word Engineer shall refer to the Chief Engineer of the Coal Company, or his representative. Labor and Materials Furnished. The Contractor shall furnish all machinery, tools, labor, materials, and supplies incidental to, or in any way connected with, the sinking and timbering of the two shafts hereinafter described, with the exception of the timber which will be furnished by the Coal Company free on board cars at Location of Temporary Plant. The Contractor's hoist- ing apparatus and temporary machinery and buildings shall be so placed as not to interfere with the construction of the permanent head-frames, or the erection of the permanent plant. EXCAVATION The dimensions of the hoist shaft shall be 13 X 26 ft. and of the air shaft 13 X 18 ft., outside of lagging. The excavation shall be carried down square and plumb from top to bottom and be large enough to give room for the proper wedging of the timber. Special care must be exercised in blasting to avoid shattering the walls of the shaft, and all loose material which might endanger the timbering or the men working below must be removed. The Contractor shall keep his machinery and tools in good condition, and take every reasonable precaution to insure the safety of his men. The Contractor shall deposit all material excavated from the shafts at places directed by the Engineer, to con- form to the grades established adjacent to the shaft. Any overhaul exceeding 500 ft. shall be paid for at the rate of cents per cubic yard for each 100 ft. of overhaul. 14 PRACTICAL SHAFT SINKING The depth of the shafts shall be measured from the elevation of the original surface of the ground in the center of the shaft to the bottom of the coal seam. TIMBERING The shaft shall be timbered throughout with sound oak or yellow pine to be furnished by the Coal Company. It is to be framed accurately by the Contractor according to the Coal Company's plans and shall be placed in the shafts square, level, and to line. Wall plates, end plates, buntons, and posts shall be 8 X 10 in., and bearing or hitch timbers shall be 8 X 12 in. ; lagging shall be of 2-in. plank. The lagging shall rest on a 2 X 4 in. oak piece placed horizontally in the middle of the back of each end and wall plate and well spiked ; the space between the lagging and the rock shall be backed solid with sound slabs or other sound refuse timber. Each corner of each ring of timbers and each wall plate at both ends of every bunton shall be thoroughly braced against the side of the shaft by blocks and wedges. The sets of timber shall be 5 ft. apart vertically, center to center. At intervals of 50 ft. vertically, bearing or hitch timbers shall be placed to serve as supports to the timbering above. The hitch or bearing in the rock at each end of each timber shall be strong enough to develop the full strength of the timber;- in no case shall it be less than 8 in. in depth. The intervals of 50 ft. may in the judgment of the Engineer be varied, but no such variations shall be made by the Con- tractor without the consent of the Engineer. The timbering shall be carried above the natural ground to the level indicated by the Engineer. Special timbering shall be placed at the shaft bottom in accordance with the plans furnished. The air compartment shall be lined with 1-in. tongued and grooved yellow pine flooring, free from knots and well matched and joined on end and wall plates. The guides shall be 6 X 8 in. yellow pine surfaced on all faces, and shall CONTRACT AND SPECIFICATIONS 15 be framed as shown on plan and placed exactly plumb, and straight and true to gage from top to bottom. WATER RINGS The water rings shall be constructed before the timbering is finally placed, and shall be as shown on the plans. The bottom of each ring shall have a water-tight floor of concrete. The number and location of the water rings shall be deter- mined by the Engineer. USE OF CONTRACTOR'S PLANT The Coal Company shall have the privilege of renting the Contractor's hoisting and pumping plant after the com- pletion of the shafts for a period of two (2) weeks. It shall pay the Contractor $ per day as rental for said plant. CHAPTER II PLANT REQUIRED BOILERS, HOISTING ENGINES, HEAD- FRAME AND BUCKETS AIR COMPRESSORS PLANT IN considering the subject of shaft sinking from the mechanical side, the first and most important consideration is the proper design and arrangement of the surface plant. The underground plant comprises rock drills and pumps, and both above and below ground many tools and con- trivances are required. The items included under surface plant will be treated first and the underground contrivances taken up later in connection with the work which they perform. The elements of a modern surface plant are: Primary- power producer; hoisting apparatus; secondary-power pro- ducers; buildings, shops, etc. Primary-power Producer. Although in a few favored localities electric power may be cheaply bought and used directly, or converted into air power when needed, in nine tenths of the shafts sunk the primary power is steam. The boiler plant, in this case, is the backbone of the job; it must be put up to allow of expansion if necessary, and it must be absolutely reliable. In other forms of construction work, water, while always a source of trouble and expense, is not the implacable enemy that it is in sinking. The pumps which drain a cofferdam will also serve to empty it, and a breakdown delays the work only until repairs are made. In a wet shaft, on the other hand (particularly where the ordinary types of sinking pumps are used), an hour's lack of steam may submerge the pumps and allow the shaft to fill. It will then be necessary to get new pumps and piping and to fight the water down again from the top, and 16 PLANT REQUIRED 17 weeks or months may elapse before sinking can be re- sumed. For a wet shaft or for any shaft deeper than 250 or 300 ft., the bricked-in return-tubular boiler is the most satisfactory type. Such a boiler burns under normal firing 15 to 20 per cent, less coal than the ordinary portable boiler. The difference in the coal bill for 100 boiler horse-power, with coal at $4.50 a ton, will, therefore, in three months, amount to $300, which is about the cost of bricking in a 100 horse- power return-tubular boiler. The latter also costs less for repairs and is generally less trouble than the portable boiler. For a short job the oil well, or locomotive type, boiler is the best. The size should be not smaller than 40 horse power; 60 horse-power is better, as in the small sizes the crown sheet has such a shallow covering of water that it is easily burned. The dome should be placed on the barrel of the boiler; if over the crown sheet, the long stay bolts connecting the crown sheet and the top of the dome are likely to give trouble. By utilizing the exhaust from a compressor or hoist engine, it is possible to force the locomotive boiler to make steam greatly in excess of its rated capacity, and this fact gives it a great advantage over other types. At coal shafts the boilers should be set far enough away to make it impossible for a sudden flow of gas from the shaft to become ignited. They should always be placed so as to minimize the cost of handling coal and ashes. The ground at one end of the line of boilers should be clear of buildings or machinery, to allow of additional units being placed as required. The piping should also be arranged to permit expansion, not only of the plant as a whole, but also the temperature expansion of the pipe itself. At the open end of the line of boilers the header should terminate in a valve, so that the additional boilers can be coupled on without shutting down the plant; if so many boilers have to be added that a second header is necessary, it should be connected with the first at both ends, forming a steam loop. Stiff connections between 18 PRACTICAL SHAFT SINKING the boilers and the header are objectionable and are likely to cause leaky joints. A constant supply of feedwater must be assured. Dupli- cate feed-pumps or injectors, or a combination of the two, should be provided, and the pumps supplying water from a stream to the supply tank should also be in duplicate. A good feedwater heater will cut the coal bill surprisingly; to be accurate, 1 per cent, for every 10 degrees the feedwater is raised. Assuming the feedwater at 50 F., originally, an open heater with plenty of exhaust steam will raise its temperature to 210 and reduce the fuel consumption 16 per cent. With coal at $4.50 per ton, a heater will pay for FIG. 1. Ingersoll-Rand Two-stage Straight line Air Compressor itself in two months. An open heater as shown in Fig. 1 is more efficient than a closed heater and maintains its effi- ciency; it has no tubes to leak and become covered with scale; it saves the pure water formed by the condensed exhaust steam, and it is adapted to various systems of water purification. It must, however, be used in connection with a good separator for removing the oil from the exhaust. A satisfactory feedwater system for a plant containing several boilers may be arranged as follows: Feed all boilers from a common header. Provide regulating valves, in addition to regular check- and boiler-stop valves in con- nections between header and boilers. Supply water to header with pump large enough to feed all boilers with piston speed of 50 ft. per minute. Use hard rubber, or PLANT REQUIRED 19 metal, pump valves. Use an open heater, placing it with base 6 ft. above the pump. As a reserve provide enough injectors to feed the boilers when the pump is shut down, connecting them into the feed-header. Provide valves between each injector and header, and between pump and FIG. 2. Cochrane Feedwater Heater header. Take steam connections for injectors and pump from mam steam line. Where freezing weather is possible, bun' all outside water lines. An ample power supply for a single dry shaft is 100 boiler horse-power. For a wet shaft the power required depends on the quantity of water to be pumped. Three 20 PRACTICAL SHAFT SINKING thousand boiler horse-power has been used for three very wet shafts, only two of them being worked at simultaneously. Hoisting Apparatus. For sinking a shaft through the surface soil, a small stiff-leg derrick is usually erected. This makes excavation and timbering cheaper than if done by hand, and it does not interfere with placing the surface concrete or add weight to the ground around the shaft. A derrick with a 40-ft. boom and a 30-ft. mast, built of 12 X 12 in. timber, is large enough for sinking. It can be readily swung by two men at the end of a 10-ft. lever bolted to the mast. If any considerable depth is to be sunk, this lever should be secured by some kind of latch to prevent the derrick swinging while the bucket is in the shaft. A double-drum friction engine is best for a derrick as it enables the engineer to raise and lower the boom, and also, with the help of a winchman,to swing the derrick; 7 X 10 in. and 8i X 10 in. are convenient engine sizes. A single-drum sinking engine may be used to advantage on a derrick with a fixed boom swung by hand. The fall line sheaves should be larger than are ordinarily used for a light derrick; never less than 18 in. outside diameter, preferably 24 in. A f-in. rope will work over a 24-in. sheave without undue wear. Although a small shaft may be readily sunk with a der- rick for 200 ft., it is better to put up a head-frame when the surface timbering or masonry is completed. Sinking head- frames are often built unnecessarily large and heavy. A head-frame 40 ft. high and 8 X 12 ft. in plan is large enough for a sinking shaft. It may be built of timber, with 8 X 8 in. posts, 3 X 8 in. diagonal braces, 8 X 10 in. caps, and 10 X 12 in. sheave timbers, as shown in Fig. 3, or, if it is to be frequently moved, of steel. If built of steel, 6 X 6 X s-in. angles will form posts strong enough to handle with safety a 5-ton pump. The sheave, as a rule, should not be smaller in diameter than the engine drum, but a 48-in. wheel will give good service with 1-in. rope. Two methods are used for the disposal of the spoil hoisted by the head-frame. In the first a broad-gage PLANT REQUIRED 21 track is extended under the frame so that the rope passes between the rails; when a full bucket has been hoisted above the track, a truck carrying an empty bucket is pushed under it, the full bucket is set on the truck, and the empty one lifted. The truck is then pushed away and the bucket dumped by a gallows frame or other device. Three buckets are needed for this method so that one may be always in the bottom. Back (Open for Sftoft T/mt>eg 40' Sinking Heex/fromff. FIG. 3. Sections of Sinking Head-frame In the second and better method, tipping buckets must be used. At one side of the head-frame a chute is built, high and long enough to discharge spoil into a dump car, its upper end just clearing the bucket hanging free on the rope, Fig. 3. On the cap above the chute a "bull chain" is hung. The "head-man" stands on a platform level with the top of the chute and, when the bucket is hoisted within reach, hooks the bull chain into the bail. The bucket is lowered slightly, swings out over the chute, and is dumped. The complete operation may be performed in 30 seconds. 22 PRACTICAL SHAFT SINKING This method requires only two buckets. Three-quarter inch common chain will serve for the bull chain. Its hook should be provided with a handle. At a deep shaft, the bottom of the chute should be covered with pieces of old rail laid lengthwise, and in rock that breaks into large lumps a gate is advisable to protect the dump car. A small house is usually built for the head-man at the plat- form level. To facilitate hooking the shaft rope to the bucket, 3 or 4 ft. of chain is inserted between the rope and the hook. The chain should be welded into a closed socket babbitted to the rope, and its links should be 6 in. long so as to afford a good hand grip. Safety catches are provided' on the hook. Shaft buckets are circular in plan and contain from J to 1 cubic yard, depending on the depth of the shaft and the size of the engine. A flared bucket, Fig. 6, discharges rock more freely than a cylindrical one; a convenient size is 3 ft. 6 in. top diameter and 2 ft. 10 in. bottom by 2 ft. 9 in. high. The bail is secured to the bucket trunnions by straps and bolts, so that it may be easily removed for repairs. A wooden inner bottom is sometimes used to cushion the blows from pieces of rock. Every bucket should have two latches, and two lugs to prevent its dumping in the wrong direction. The dump car that will not be knocked to pieces by large rocks falling from the chute must be very strongly built. Its other qualifications depend on the nature of the dump. Ordinarily, where the dump is close to the shaft, and the car is pushed by hand, a 36-in. gage, all-around dump car, with wheels loose on the axle, is best. The simpler the construction the better. A cheap and easily erected head-frame, for use when the regular plant is not available, consists of a tripod made of three poles bolted together at the top. This is set up over the excavation, a snatch block is attached at the top and another at the foot of one of the legs, and small buckets are hoisted by a team of mules, pulled to one side and dumped PLANT REQUIRED 23 on a platform by hand. The buckets are made out of a half oil barrel, fitted with extra hoops and a bail. For depths of less than 500 ft., an 81 X 10 in. double- cylinder end-friction hoisting engine with a 41 -in. drum will do satisfactory work. The friction and brake levers are most convenient if set in a stand back of the drum, as is customary with larger engines. Both should have latches; on the brake lever a latch is imperative. An engine of this size will hoist a loaded bucket weighing 2500 Ibs. 350 ft. in a minute; a round trip from this depth, including dumping the bucket, can be made in two and a half minutes. At depths greater than 500 ft., the weight of the rope and the long hoist make a larger engine necessary. Rever- sible link-motion geared engines similar to that shown in Fig. 7 are generally used, the sizes varying from 10 X 12 in. to 14 X 20 in. First-motion engines are sometimes used for great depths. A 10 X 12 in. geared engine running at a speed of 400 ft. per minute has a hoisting capacity of 4500 Ibs., and will handle muck from a depth of 800 ft. The drum should be grooved so that the rope will wind regularly and not cut itself. The size of rope used for sinking runs from f in. up, but sizes greater than 1 in. are unnecessary. A 1-in. crucible cast-steel rope has a breaking strength of 34 tons; it weighs 1.58 Ibs. per foot, and there- fore, when hoisting a 3000-lb. bucket, has a factor of safety of 11 at a depth of 2000 ft. This factor is ample, and there is no use in consuming power in hoisting additional weight. Many lives depend on the brake of a sinking engine, and it should, therefore, be made large and strong beyond possibility of fracture. In the case of a band brake, the diameter of the part of the drum gripped by the band should be as great or greater than that of the drum itself, and the lever should tighten the band in the direction of the pull of the rope, the other end of the band being rigidly attached to the frame of the engine. A good brake, capable of stopping the drum every time within an inch of the mark, is not only a safeguard, but a great assistance to sinking, 24 PRACTICAL SHAFT SINKING especially in setting up the bar and machine or in handling timber. Double-drum engines, necessarily friction operated, are built for sinking purposes, one drum being used for the bucket, the other for handling pumps, piping, etc. The second drum introduces another set of gears, causing addi- tional friction and wear, even when running idle, and costs as much as a small independent engine, which is in every way preferable. A compound-geared, reversible link-motion engine, of the type used for swinging derricks, makes a good engine for handling pumps. The 7 X 8 in. size will hoist 7000 Ibs. on a single rope. The engine can be started and stopped just where desired, and there is no danger of a heavy load getting out of control. Electric hoists are now built by several firms in sizes equivalent to their standard steam engines, and operate satisfactorily with various types of motors. Gas engines have found a very limited application to hoisting, but small gasoline hoists can be bought. Signals are given the engineer by a "bell" in the engine house. It consists of a small whistle or a hammer striking a triangle, and is operated by a wire leading to a bell-crank on top of the shaft, thence to the bottom. A coil of wire is usually clamped to the horizontal arm of the bell-crank and paid out as the shaft deepens. The weight of the wire in the shaft is counterbalanced by weights hung on a third arm of the bell-crank or otherwise arranged. No. 6 gal- vanized-iron wire is good for a 500-ft. shaft; for greater depth 1-in. strand is better. The bell-crank may be con- veniently placed in the head-man's shanty. Regular stopping places for the bucket, such as the " steady," are marked by the engineer by tying cotton cord around the rope. It is to enable him to see these marks more readily that the lever stand should be placed behind the engine. After a shaft has reached a depth of about 200 ft., it becomes necessary to steady the bucket very carefully PLANT REQUIRED 25 before hoisting, to prevent its striking the timber. With a common rope the bucket also rotates rapidly on a long hoist. To avoid these effects, guides and a "billy," or " dummy," Fig 4, are installed. The billy is a light frame of wood or iron composed of two upright parts engaging the guides, and a cross-bar, through the middle of which the rope passes. It is carried by a buffer, clamped to the rope 4 or 5 ft. above the chain socket. The guides usually are terminated at the bottom of the last placed section of permanent lining, and buffer blocks stop the billy at this point, the rope running through the hole in the cross-piece as the bucket descends into the bottom. If the billy is made of wood, this hole should be lined with iron to prevent cut- ' ting. Old rubber pump valves make good buffers on the rope and on the stop- blocks. Both wooden and wire- rope guides are used for the billy, but even where the FIG. 4. "Billy" permanent guide timbers are available, rope is to be preferred. It can not only be placed more quickly and cheaply than timber, but it is safer. With timber there is a likelihood of the billy stick- ing, and then jarring loose and falling on the bucket; with wire rope this danger is avoided. At a shaft in Western Pennsylvania several years ago, the billy, after sticking on some ice on the wooden guides, fell and killed four men. The use of a billy prevents any rotation of the bucket above the bottom of the guides, but below them the rotation seems intensified. To obviate this difficulty, non-rotating ropes have been devised. One form consists of a core and two layers of 7-wire strands wound right-handed and left- handed, respectively. The wires in the strands may be wound either common or lang-lay. These ropes fulfil their purpose (in fact are specified in some recent contracts), but 26 PRACTICAL SHAFT SINKING do not wear particularly well. It is impossible to use an ordinary lang-lay rope for sinking as it will entirely untwist. Secondary-power Producers. The most important of the secondary-power producers around the sinking plant is the air compressor. As yet, electricity has been unable to compete with steam or compressed air as a motive power for rock drills or sinking pumps; for underground work air has incidental advantages over electricity in that it assists ventilation and cannot ignite explosive gases. The simple straight-line air compressor is the favorite for sinking. It is made by a number of firms; the Ingersoll- Rand Co.'s sizes range from 10-in. steam X 10i-in. air X 12-in. stroke to 24-in. steam X 24|-in. air X 30-in. stroke, with capacities of 177 and 1223 cu. ft. of free air per minute, respectively. It is more efficient mechanically than most small engines, and is wonderfully dependable with reasonable care. The 16 X 161 X 18-in. size is a convenient one for a pair of shafts; it has a capacity of 500 cu. ft. and will readily operate four drills and a small pump. A straight-line compressor with a two-stage air end, Fig. 1, is made, which, according to the statements of the manufacturers, ought to be a good investment. With a steam consumption of 45 Ibs. per indicated horse-power at half cut-off, the simple compressor has, for each indicated horse-power, a capacity of 5 cu. ft. of free air per minute compressed to 100 Ibs. With the same steam consumption the two-stage compressor will deliver 15 per cent, more air. For 500 cu. ft. free air per minute, the saving of the two- stage over the simple type will therefore amount to 15 per cent. X i X 500 cu. ft. X 45 = 675 Ibs. steam or 150 Ibs. coal per hour. With the compressor operating to capacity twenty hours per day, six days a week, the saving in three months, with coal at $4.50 per ton, would thus be $525. This is somewhat more than the difference in cost of the two machines. On tunnels and similar work, where a number of shafts and headings are to be driven along a line, it is economical PLANT REQUIRED 27 to put up a central power plant at a point where coal can be most conveniently delivered and to pipe the air to the several openings. For installations of this kind, the cross- compound condensing steam, two-stage air compressor is best. A good-sized machine of this type, fitted with Corliss valves and a well-designed inter-cooler, has a steam con- sumption of 16 to 18 Ibs. per indicated horse-power hour, and will compress 5.8 cu. ft. of air per minute per indicated horse-power. All the figures given for air-compressor power apply to 100 Ibs. receiver pressure, the machines operating at sea level. When the air is piped to a considerable distance, an after-cooler at the compressor will condense a large propor- tion of the water vapor carried, and thus prevent the for- mation of ice in the pipes and valve chests. Freezing is also prevented by the use of a reheater in the pipe where the air is to be used, which also increases the power obtain- able from cold compressed air at a small expenditure of fuel. A good reheater will receive air at 60 and deliver it at 240, thus raising the volume and the available power 25 per cent, with an insignificant coal consumption, if the air can be used before it cools. Electric light is now essential for effective night work anywhere, and is particularly useful at a sinking shaft where . the outside work must be carried on under all conditions of wind and weather, and the inside work sometimes under conditions (such as great quantities of falling water and ex- plosive gases) that make the maintenance of an open flame impossible. Very little power is needed, as two arc lights and 30 incandescents will give abundant illumination in and around any single shaft. A 5-kilowatt generator is thus large enough to light a pair of shafts, but as it may be desirable to supply light to other work near the. shafts, or to run one or two small motors, it is better to double this size. Small direct-connected units are made that are compact and easily handled but are expensive; and the care that machinery gets around construction work does not 28 PRACTICAL SHAFT SINKING warrant the use of a small and delicate high-speed engine. A cheap and satisfactory light plant is formed by an 111 kilowatt generator, belt-connected to an 8 X 12 in., hori- zontal, medium-speed, automatic engine. The vol FIG. 5. Sinking Head-frame showing Dumping Arrangement should not be higher than 220; even 110 will give quite a severe shock to a man who is soaking wet. The outside wiring calls for no especial comment. In the shaft, however, very thorough insulation is required on account of the constant fall of water. In sinking, the bottom lights must be raised before every shot, and it is PLANT REQUIRED 29 most convenient to suspend them by their own wire from a reel. The reel may be kept on top of the shaft for 400 or 500 ft. of sinking, and then moved down to reduce the weight of hanging wire. A suitable reel may be cheaply built of wood by a carpenter. The two wires should wind on sepa- rate drums on the same shaft, so that they will hang entirely clear of each other. If a wooden shaft is used, the journals may be covered with copper strips, and made to serve as collecting rings. Six 16 candle-power bulbs arranged as a cluster will light the shaft bottom. They should be set in waterproof sockets and protected against breakage by wire screens. An inverted dishpan hung above the cluster, with the wires passing through a hole in the middle, will shed falling water, and also act as a reflector. The wires must be heavily insulated where they pass through the pan. Of the auxiliary mechanisms of a sinking plant, machine tools and small fans or blowers may be advantageously motor driven. If a large fan is necessary, it is simpler and safer to drive it direct by a separate engine. A very useful machine, that may be either engine or motor driven, is a swinging cut-off saw for cutting lagging to length. Such a machine will pay for itself on a single deep shaft. Buildings. After the machinery has been selected and set up, it is necessary to house it and the men that operate it. The cheap and obvious building materials for temporary work are 1-in. boards and tar paper. They are also highly inflammable, and on that account should be used with dis- cretion when it comes to covering valuable machinery. It is surprising how completely the burning of a board shanty will wreck an engine inside it. Twenty-two gage corru- gated iron can be bought and erected nearly as cheaply as boards and paper, and should at least be used for covering the compressors and engines. In cold weather it is hard to heat a corrugated iron building, hence boards are preferable for shifting shanties, etc. The buildings needed around a sinking shaft are: Boiler 30 PRACTICAL SHAFT SINKING house; compressor and dynamo house; engine house; shift shanty; blacksmith and machine-shop; powder house; oil house; powder thawing house; office and tool house. The sizes and styles of these depend on the size of the job and the desires of the man who is running it. He may consolidate or omit some of them. In general, however, they all have different functions and should be separate. If the boilers are under the same roof as the machinery, they should' be divided from it by a tight partition to keep cinders and dirt out of the bearings. The shift shanty should be adjacent to the shaft, large enough for all the men lays and Latches on Both Sides of Bucket J"Jf 'Trunnion ftmf. /feiywS Bottom Detar/ o/ Connect ion o/ Ba/J to Trunnion. FIG. 6. Details of Sinking Bucket on the shift to change their clothes at once, and should have plenty of pegs for drying clothes, and a good stove or radiator. The powder house and the oil house should be separated from each other and the former placed some distance from the job. They should be only large enough to contain the stocks of dynamite and oil actually needed, and should be built of iron to lessen the risk of fire and lighting. Caps and exploders should never be stored with dynamite. The powder thawing house is preferably a box or closet that will hold three or four boxes of dynamite, and is heated by steam coils. It should be so constructed that loose sticks of powder cannot come in contact with the hot pipes. Thawing boxes covered with manure are sometimes used, but are not safe, as manure is liable to spontaneous com- bustion. PLANT REQUIRED 31 The blacksmith and machine shop should contain a forge fitted with bellows- or hand blower as well as a blast connection to the air line, benches with common and pipe vises, a grindstone, a small drill press, and, on a good-sized job, a pipe cutting and threading machine. The small tools should comprise blacksmith and drill-sharpening tools, pipe dies and cutters, bolt dies and taps, a ratchet drill, hacksaw, hammers, monkey and pipe wrenches, chain tongs, etc. A good assortment of miscellaneous pipe fittings and drill repairs should be kept on hand. FIG. 7. Double Spur Gear Reversible-link Motion Lidgerwood Hoist The contents of the tool room also depend on the size of the job, but a good equipment saves money in the end. The following articles are either necessary or very useful: Good assortment of round and flat blacksmith iron, assorted nuts and washers, packing for engine and compressor glands and pumps, gasket, waste, oil cans, torches, crosscut saw, crowbars, striking hammers, picks and shovels, assorted nails, manila rope and blocks, cant hooks, lever jacks, etc. The general layout of the job depends so largely on local 32 PRACTICAL SHAFT SINKING recommendations. The location of the boilers has already been discussed; if a railroad siding leads to the shaft, it is well to place the line of boilers parallel to it, so that coal can be unloaded directly into bunkers. The storage and sub- sequent handling of timber must also be considered. The temporary buildings should be so located that they will not be put into a hole by the encroachment of the dump; the position of the dump itself must be considered with relation to the drainage of the surrounding ground. The sinking engine, boilers, and machinery (as is usually specified) should not interfere with the erection of the permanent mining plant. Lastly, it may be again stated that too much attention cannot be given to the piping system all over the job as regards tightness, drainage, and insulation. Cost. The cost of a plant for a single shaft, assuming a depth of about 500 ft. and a moderate inflow of water, say 30 or 40 gallons a minute, is as follows: Sinking engine $1,000 Two 80 horse-power boilers and setting 1,800 Pipe and auxiliaries 500 150 horse-power heater 300 14-inch compressor 1,750 Three drills and steel 1,000 Shaft bar and clamps 100 Derrick 400 Head-frame 500 Two buckets 150 Rope 150 Buildings 500 Dump cars and rail 300 Electric plant, 10 kilowatts 750 Two pumps 500 Small tools 500 Total $10,200 These figures are based on the cost of new machinery, and are large enough to include the necessary accessories. The cost of erecting and dismantling such a plant will be from $1000 to $2000, depending on location, labor condi- tions, etc. CHAPTER III SINKING THROUGH SURFACE SOFT GROUND WOODEN SHEETING STEEL SHEETING CAISSONS OF STEEL, WOOD, OR CONCRETE. SINKING THROUGH SURFACE IN most localities a certain amount of soil or soft ground overlies the ledge rock. Its depth varies from nothing to hundreds or even a thousand feet, and its nature is as varied as that of the rocks which it covers. The shaft sinker is interested chiefly in its consistency, which determines whether the penetration of the surface will be the easiest or the most arduous and expensive part of his job. There is no hard and fast line of demarcation between firm ground and running ground; every degree of hardness or softness can be found from boulder clay to river silt, but ordinarily in sinking, ground is considered firm when the excavation can be carried ahead of the support, and soft when the support must be driven ahead of the excavation. In the first classification are included boulder clay, ordinary dry blue or yellow clay, cemented or clayey gravel and most loam soil; loose sand and gravel and silt come under the second. The amount of water in the ground has a very great effect on its firmness, as is shown by the caving of excava- tions after a rain storm; conversely, soft wet ground may be made comparatively firm by removing the water. The commonest application of this principle is the use of com- pressed air for driving quicksand tunnels without the use of a shield. In this case the water is forced back away from the face into the surrounding ground, and timbering opera- 34 PRACTICAL SHAFT SINKING tions can be performed readily, which would be utterly impossible if the water were allowed to flow into the bore of the tunnel. A trench in quicksand was recently driven at Gary, Ind., with very great success; here the water was drained in advance of the excavation through a number of small per- forated pipes driven into the ground and connected at the FIG. 8. Hanging Timbers in Firm Earth upper ends to the suction side of a pump. The writer knows of no case in which quicksand has been drained in advance of the excavation of a sinking shaft by driving small suction pipes into it, but in view of the success of the plan in the trench instanced above, he sees no reason why it could not be worked out for a shaft. Compressed air is extensively used for sinking bridge piers and other caissons through soft ground; the applica- tion of this process to shafts will be considered later. SINKING THROUGH SURFACE 35 Concrete masonry is now almost entirely used for per- manently supporting the sides of shafts in soft ground. The methods in use for temporary support while sinking are: Timbering; this heading includes the driving of wooden or steel sheet piling, as well as forepoling. Caissons; these may be open drums, or closed drums sunk under compressed air. Iron sinking drums and shoes, forced down hydraulically. The freezing process. The first method is applicable to comparatively easy surface conditions; the others to more difficult conditions. The last two have been developed in Europe for sinking through great depths of sand or mud, and are not extensively used in this country. The various methods will be treated in order. Timbering While sinking through ordinary surface ground the sides of the shaft are usually supported by square-framed horizontal sets of timbers with vertical lagging behind them. The distance between the sets depends upon the firmness of the ground, and varies from about 6 ft. as a maximum to nothing for "skin to skin" timbers in soft material. In square-framed sets the end and side pieces are termed "end plates" and "wall plates," respectively; the cross-struts, "buntons," and the posts which separate the sets, "punch blocks." FIRM GROUND The cheapest kind of sinking is afforded by earth that does not require blasting, yet is stiff enough to stand 'ver- tically for 4 or 5 ft. without support. In such material the usual procedure is to commence the excavation just large enough to admit the timber and lagging, and to carry the sides down vertically without support as far as it is safe to do so. The timbering is then started on the bottom and brought up to the surface of the ground. Two or more heavy bearing timbers, long enough to extend 4 or 5 ft. 36 PRACTICAL SHAFT SINKING beyond the lagging at each end, are laid across the shaft on the surface and their ends are supported by blocking them solidly against the ground, Fig. 8. The sets of timber are then hung from these bearing timbers by heavy rods, and sinking is resumed. As soon as 4 or 5 ft. of ground is removed, another set is placed on the bottom, hung with rods to the set above, and the lagging is worked in back of them in pieces just long enough to bear on both sets. The process is then repeated. Bearing timbers are usually placed over the end plates and over each row of buntons, and punch blocks are set at the corners and under the ends of all buntons.- 10 X 12 in. timber sets, spaced 4 ft. center to center and braced so that the longest span will not exceed 12 ft., will safely support firm earth for a depth of 60 or 70 ft. The weight of the timbers is partly carried by the friction of the earth against the lagging, and the hanging bolts are not subjected to great stress; they may sometimes be en- tirely omitted. A ledge of earth is in this case left under the bottom set, and the middle of the shaft excavated; inclined posts are then wedged between the shaft bottom and the timbers and the ledge removed. It is generally safer to use 1| or IJ-in. hanging bolts, however. Exca- vations of this character can be done for a total labor cost, including the placing of timber, of $1.50 to $2 per cubic yard. As the softness of the ground increases, the distance between sets -is decreased. Sometimes the lagging is omitted and the lower set worked in immediately under the one above. The consideration of this plan properly belongs under soft- ground work. SOFT GROUND Wooden Sheeting. When ground is so soft that it will not stand vertically at all, it becomes necessary to support it in advance of the excavation. The commonest method of doing this in any kind of pit is to enclose the area to be dug out with a coffer of sheet piling, driven by hand or power, Fig. 9, and to brace the inside of the coffer as the SINKING THROUGH SURFACE material is removed. In starting a shaft, two sets of timber, one 5 ft. or so above the other, are set up as a guide frame, and the sheeting driven around them. The top soil is usually firm enough to enable these sets to be placed below the surface, but this is not, of course, essential. If the sets are placed above the surface, outside waling pieces are bolted through the sheeting at the top set in order to hold the top of the sheeting in line. So// FIG. 9. Successive Courses of Sheeting In dry sand or other loose ground that does not contain much water, the sheeting is driven as the excavation pro- gresses, and the points of the piles are kept only slightly below the bottom. Two-inch planks in 12 to 16 ft. lengths are commonly used in this case and are driven by hand with heavy wooden mauls. The heads should have beveled edges to prevent splitting, Fig. 10, and for hard driving, or with soft wood, a plate-iron cap may be used to advantage. By thus protecting their heads, the planks can be driven to their full length; a second course of sheeting is then driven inside the timbering of the first course, and so on until the required depth is reached. The economical limit for this 38 PRACTICAL SHAFT SINKING method, however, is about 50 ft., as it necessitates starting the shaft much larger than the minimum required size; some additional allowance must be made on every course for possible distortion and for inward bending of the sheeting at the points. Let us assume 50 ft. of surface, 10 X 10 in. timber, and 2-in. lagging, and a shaft 12 X 24 ft. with a 4-ft. concrete curb wall. Four courses of sheeting will be required, the last 20 ft. 4 in. X 32 ft. 4 in. outside, its wall plates to be buried in the concrete. Allowing 6 in. all around each time for distortion or squeezing, the third set will be 23 ft. 4 in. X 35 ft. 4 in., the second 26 ft. 4 in. X FIG. 10 FIG. 11 38 ft. 4 in., and the first 29 ft. 4 in. X 41 ft. 4 in. The total excavation will thus be 40 per cent. .in excess of that theoreti- cally required for the curb wall. Any additional depth necessitating another course of sheeting will increase the percentage of useless excavation, and will require a larger quantity of heavy timber. When many light sheet piles are to be driven, the work can be done more cheaply with some form of power driver than with mauls. A driver like an enlarged rock drill, Fig. 12, has been devised for this purpose, and a common drill fitted with a hammer instead of a bit will drive light sheeting satisfactorily. Either machine is suspended with blocks and falls from a trolley or tripod over the line of sheeting. SINKING THROUGH SURFACE 39 Steel Sheeting. In quicksand or other wet running ground, sheeting must have joints that are almost water- tight, and as it is impossible to drive common plank close enough to make a satisfactory coffer in such material with- out caulking, some form of interlocking piling should be used. Formerly tongued and grooved, splined, or Wakefield piling, Fig. 11, were the only forms available, but now they FIG. 12. Sheet-pile Driver have been superseded for difficult work by the interlocking steel sheet pile. A slight obstruction will cause wooden piling to separate at the bottom, whereas it is almost im- possible to pull the steel piles apart. Steel piles, moreover, can be more easily driven, will penetrate most obstructions, and can be readily pulled and redriven. There are a dozen types on the market, each with its advocates, but the sim- plest shapes are those rolled by the Carnegie Steel Co., (a) Fig. 13, and by the Lackawanna Steel Co., (6) Fig. 13. 40 PRACTICAL SHAFT SINKING Both are strong and satisfactory and, though not water- tight when first driven, will soon become so in most ground. An additional advantage that steel piles possess is that they can be obtained in lengths up to 60 ft. and can be completely driven before excavation is started. When the ground is very bad, they should be made to reach rock so as to prevent material from flowing under their points. In one case a hole 36 X 27 ft. 6 in. in plan and 27 ft. deep was needed for a furnace pit; the material was soft quicksand and rock lay at an unknown depth. Steel sheet piling 48 ft. long was obtained and successfully driven entirely around the pit and followed down 4 ft. below the surface. The first 20 ft. of sand was easily removed, but as the depth increased, sand began to flow in under the piling and gradually bent their points inward, throwing a terrific strain on the lowest set of timber. A complete wreck was finally prevented by filling the hole with sacks of concrete which sank into the sand and supported the lower end of the piling. This en- abled the desired depth to be reached, but it would have been practically impossible to reach rock if the hole had been intended for a shaft. Steel piles and heavy wooden sheet piles must, of course, be driven by machinery. While a discussion of pile driving would be out of place in an article on shafts, it may be said that, in the writer's opinion, a steam hammer is preferable to a drop hammer for sheet piling, whether used in regular or suspended leads. Sometimes a water jet is necessary; with a jet piles can be easily sunk by the weight of the ham- mer through sands into which they cannot be driven at all. The chief trouble in driving a steel-pile coffer is in making a good closure. Sometimes the last pile exactly fills the gap, but more often a lap joint is made which is caulked with hay or junk. With care a good joint can be made in this way. Steel piling in short lengths is used for cutting off thin strata of quicksand encountered some distance below the surface. In this case the piles are locked together all SINKING THROUGH SURFACE 41 the way around and each is driven only 2 or 3 ft. at a time until all reach the rock. Steel piling can be driven through logs, strata of cemented gravel, etc., but in ground containing large hard boulders some other method must be used. At a quicksand shaft in Michigan, boulders were encountered, but steel piles were driven until they had apparently reached the desired depth. The coffer, however, could not be excavated, as the sand in some way flowed in as fast as it was removed. Com- pressed air was finally applied, and when the points of the piles were reached, they were found to be torn apart by the boulders. Several piles, bent through a full half circle, were pointing up the shaft. (a) FIG. 13. Sheet Steel Piling Forepoling. Forepoling was formerly used for shafts in soft ground of any nature, and depths of 100 ft. have been reached in the worst kind of material. Under such condi- tions forepoling is very slow and expensive, and although it has been largely, if not entirely, superseded by the steel sheet pile or caisson methods, some discussion of it is of interest. Forepoling is still widely used for soft-ground tunnels. In starting a shaft which is to be forepoled through difficult ground, strong trusses are used for bearing timbers and the ring timbers are suspended from them by heavy bolts. The trusses span the shaft, Fig. 14, and their ends are supported by broad cribs or piers set well back from the edge of the shaft. They are built strong enough to carry the weight of all the surface timbering and also of the head-frame, if one is used. After the head-frame, or derrick, is ready, digging is started and the sides of the shaft are supported by short piles or poling boards driven on a 42 PRACTICAL SHAFT SINKING slant so that they bear against .the outer face of the bottom set of timbers and the inner face of the one above. The poling boards are made twice as long as the distance between the sets (or longer), so when one course is driven home, enough ground can be dug out to enable another set of timbers to be placed. The worse the ground, the longer must the poling boards be made to prevent it flowing under them. The most troublesome places are the corners where the boards are divergent, and the spaces back of the buntons where a board is necessarily omitted. These openings are closed by short transverse boards placed as the excavation proceeds. After a depth of about 40 ft. has been reached, the pressure of running ground becomes so great that single sets of timber, spaced so the poling boards can be driven between them, will not support it. Two or more timbers must then be placed "skin to skin" to form the wall and end plates, and as the depth increases the spacing of these compound sets must be reduced until the poling boards have to be driven nearly horizontal, and therefore fail to prevent the ground from rising in the shaft. This is where troubles with the forepoling method really begin. Every inrush of material causes a settlement of the ground around the shaft, throws the shaft itself out of line, and puts very great stresses on the timbers and the hanging bolts. In some cases heavy timbers driven with a ram have been used for poling boards. They were thus driven deep enough, and the successive courses were separated suffi- ciently, to permit very heavy ring timbers. Among the other plans that have been devised to keep the bottom down may be mentioned : Drainage of the ground ahead of the excavation by means of a perforated iron drum, jacked down and used as a sump for pump suctions. A short stoppage of the pumps will allow the ground to become saturated again and start a run, and besides it is very hard to keep pumps running steadily with sandy water. SINKING THROUGH SURFACE 43 Drainage of the ground by means of a timbered sump combined with a system of floor boards similar to the breast boards used in soft ground tunnels. This method is very slow and laborious. Sinking quantities of hay and brush into the ground around the shaft by loading them with pig iron. This stiffens the ground to some extent and tends to prevent runs. It is a help with any style of timbering in quicksand, and may even be necessary in sinking a caisson. Caissons. In the last ten years many American engi- neers have adopted the sinking drum or open caisson for penetrating soft ground. A hollow cylinder of masonry is constructed on the surface with its axis vertical and its walls tapered outward at the bottom to a cutting edge. The outer surfaces of the walls should be smooth and verti- cal, and the cutting edge should be slightly larger than the rest of the cylinder. After the masonry has hardened the earth is excavated on the inside, and the caisson sinks of its own weight. It is kept plumb by digging out under the high side. When the top reaches ground level, another section is added and this continues until the cutting edge reaches rock. This method has long been employed in Germany, the caissons being constructed of brick or stone; in this country timber caissons have occasionally been used. The low tensile strength of brick or stone and the difficulty of sinking wood in bad ground made these materials unsatis- factory. Concrete, combining weight with strength, is almost ideal, and as it is not only better than timber and brick, but also cheaper, it has displaced them both for building caissons. Rectangular Caissons. Caissons are ordinarily circu- lar, but sometimes are made rectangular of reinforced concrete. A noteworthy example of this type is a shaft recently sunk for the D., L. & W. R. R., on the flats opposite Wilkesbarre, Pa. This shaft, 48 ft. 10 in. X 14 ft. in the clear, was sunk through very wet quicksand to a depth of 70 ft., in four months, including the time lost in sealing the 44 PRACTICAL SHAFT SINKING caisson to the rock. It thus affords a decided contrast to the Pettibone shaft near by, which, sunk by forepoling, took eight years. Cost figures are unobtainable but seem unnec- essary. The walls of the D., L. & W. caisson are 5 ft. 4 in. thick at the bottom, 2 ft. 8 in. at the top, and are plumb on the outside. Two reenforced cross-walls serve as buntons and also support the side walls. Several rectangular caissons have been sunk along the Monongahela River in the flats above Brownsville, Pa. The ground is not very bad, but contains enough soft clay and quicksand to make timbering very difficult. Two of these were coal shafts and were sunk through 50 ft. of sur- face in two months in the winter of 1908-09. Circular Caissons. A circular caisson was sunk in the autumn of 1908 for Shaft No. 2 on the Rondout Siphon of the Catskill Aqueduct. The surface was about 60 ft. thick, of which 6 ft. was sandy loam. The balance was a wet material that resembled blue clay when dried out, but which in the ground was completely saturated. It flowed slowly like cold molasses, and was very sticky. Overlying the rock and entirely surrounded by the muck were quantities of hard boulders of all sizes, which had to be blasted from under the cutting edge of the caisson. The combination made as difficult ground to sink through as can well be conceived. The shaft desired was a three-compartment shaft, 10 X 22 ft. outside the timbers, with two hoistways. The caisson was made 21 ft. inside diameter, Fig. 15, giving ample room for the hoistways and a ladderway; the area for air is of course in excess of that afforded by the rectangular shaft. This caisson was built and sunk to rock in two months, and a description of the method used for it will give a good idea of the process in general : It was decided that a caisson with 30-in. walls would be strong enough and heavy enough to sink to rock, and a steel shoe or cutting edge 26 ft. in outside diameter was obtained. This shoe was formed of two \ X 20 in. plates riveted SINKING THROUGH SURFACE 45 together at the bottom and flared at the top to include the lower part of the concrete wall. It was anchored to the concrete by about eighty f in. X 8 ft. countersunk-head bolts. Short Horijonfal Boa/zfc fo c/dse corner^ FIG. 14. Forepoling The shaft site w r as leveled, the shoe assembled upon short planks laid on the ground, and forms for the concrete were started. The forms were built of vertical 2-in. lagging in 4-ft. lengths, supported inside and out by rings of 4 X 3 in. angles tied together by f -in. rods. Five feet of 1:2:5 con- crete was placed and allowed to set for a week to obviate the possibility of settlement cracks above the cutting edge; 10 ft. more was then placed and, as soon as it had hardened sufficiently to permit of the forms being removed, sinking was commenced. The mud was loaded into shaft buckets 46 PRACTICAL SHAFT SINKING by men standing upon plank rafts and was hoisted with a derrick. Sometimes the mud had to be bailed with water buckets, but usually shovels could be used. When the top of the first 15 ft. of concrete reached the ground level, 10 ft. more were added and excavation com- menced again. Thus far the cutting edge had been very little in advance of the excavation, but at this point the cais- son suddenly dropped 7 ft. and the mud inside rose 12 ft. The cutting edge was seen no more until it had almost reached rock. After the drop 20 ft. of concrete were added before excavation was started. Before this had been sunk to ground level, a stratum of very soft mud was encountered which ran in under the shoe and caused the surface to cave on the side next the derrick. The caisson gradually leaned toward the caving ground until it was nearly 2 ft. out of plumb. Sinking was then stopped, 10 ft. of concrete added, a trench dug through the 6 ft. of surface clay on the high side of the caisson, and the dirt banked against the caisson over the cave-in. When sinking was started the caisson began to right itself. It soon stopped moving, how- ever, and the cutting edge was found to be resting on large boulders which had to be broken with dynamite. In the meantime the mud ran in almost as fast as it could be hoisted out, and the caving continued. When the cutting edge was within about 6 ft. of rock, the caisson literally stuck in the mud and refused to move even when the boulders were blasted out all around. A heavy timber platform was then built on top of the concrete and loaded with 200 tons of clay. As the caisson still stuck, the sur- rounding mud was agitated by blowing compressed air into it through U-in. pipes which had previously been built into the wall; a l|-in. pipe was also used as a jet and worked down to its full length on the outside. This was done over and over again all the way around. After a few hours the drum started to sink and reached rock without further trouble. The trouble in this case was due to the great stickiness SINKING THROUGH SURFACE 47 of the mud. An additional thickness of 6 in. in the walls would have probably caused the caisson to sink without delay. As it was, only forty-eight days elapsed from the erection of the shoe to the commencement of rock excava- tion, an average progress of 1.2 ft. per day. ' i , p 1 .!': i ' j : T j i i --/"Vert icaf Reinforcement -80-jxd'o" Anchor Pods. . (2-s"x0~ P/ate '&><*< F///er ' 1 Tly 4 / 1 /-'-p E 1 FIG. 1.5. Circular Concrete Caisson Fig. 16 shows the shoe and the lower part of the form, Fig. 17 shows the derrick, mixer, and general layout, and Fig. 18 shows the dump composed of mud spread out over an acre or more of ground. All caissons should have some vertical reenforcement, so that if the upper part sticks the lower part cannot drop away from it. The absence of this has caused several wrecks. 48 PRACTICAL SHAFT SINKING Steel shoes are only necessary in ground containing boulders. A concrete cutting edge properly reenforced is strong enough to penetrate sand or clay with safety. A number of points must be considered in deciding whether to use a rectangular or a circular caisson in a given shaft. The circular shape is easier to build and sink, and, owing to arch action, thinner walls can be used. No horizon- tal reenforcement or cross-braces are needed, and therefore FIG. 16. Shoe, Lower Part of Form, and Reinforcement, Rondout Caisson a grab bucket can be used to advantage. The rectangu- lar shape, on the other hand, requires less excavation, and the walls of any caisson must be made thicker than are needed for strength to give weight for sinking. In general it is probable that the circular shape is better for a one- or two-compartment shaft, and for a three-compartment shaft in very bad ground; the rectangular for a three-compart- ment shaft in ordinary soft ground. For long shafts, a rectangular caisson is a necessity. An allowance should always be made for a possible tilt from the vertical that may amount to from 18 in. to 2 ft., SINKING THROUGH SURFACE 49 either by battering or stepping the walls on the inside, or by making the caisson larger than the neat size required. In a rectangular caisson the side walls should be braced with temporary struts while sinking, and the permanent buntons or cross-walls placed after it has reached its final bearing on the rock; it may otherwise be impossible to line the guides up plumb. The relative costs of piling, forepoling, and caisson are influenced by local conditions and by the type of shaft desired. For instance, a permanent shaft, such as the D., L. & W. shaft at Wilkesbarre, must have a masonry FIG. 17. - Derrick and Head Works Rondout Caisson lining through the surface anyhow, and it is therefore not fair to charge against the excavation the cost of the concrete in the caisson. In a temporary shaft, on the other hand, the excess of the cost of the caisson over the cost of a timber lining must be charged against the excavation. The writer believes, nevertheless, that wherever the ground is not firm enough to support itself for one set in advance of the timber lining, a caisson is safest and cheapest in the long run. A possible exception may be made to this statement in the case of a moderate depth of very wet ground where the work is done by a contractor who owns the equipment for driving 'steel piles and can recover them after the masonry lining is completed and use them on other work. 50 PRACTICAL SHAFT SINKING The costs given below should be fairly representative for the different methods of work : 1. Shaft excavated 14 X 20 ft. through 6 ft. of soil and 14 ft. of quicksand, not very wet. Sides supported by 2-in. oak sheeting driven by mauls and braced by five sets of 10 X 12 in. timber. FIG. 18. Dump, Rondout Caisson, Showing Flowing Nature of Material Per Foot Per Cubic Yard Labor $27.25 $2.57 Lumber, 6600 feet B. M. at $30 9.90 .93 Erection of derrick, etc 3.00 .29 Superintendence 3.00 .29 Sundry 2.00 .18 Coal and pumping 5.00 .47 Total $50.15 $4.73 2. Shaft excavated 12 X 20 ft. 3 in. through 45 ft, of clay and gravel. Sides supported by sets of 10 X 10 in. pine timber spaced 4f-ft. centers and hung from top. 1^-in. lagging: Per Foot Per Cubic Yard Labor $19.50 $2.17 Lumber, 240 feet per foot at $25 6.00 .66 Bolts, 15 pounds per foot at $0.03 45 .05 Erection of head-frame, etc 2.00 .22 Superintendence 2.00 .22 Power 1.50 .17 Sundry 1.00 .11 Total . .. $32.45 $3.60 SINKING THROUGH SURFACE 51 3. Shaft excavated 15 X 37 ft. through 21 ft. of dry sand. Sides supported by interlocking steel sheet piling driven with steam hammer and braced with sets of 8 x 10 in. timber : Labor Costs Only Per Foot Per Cubic Yard Driving sheeting $ 6.55 $ .32 Removing sheeting 1.85 .09 Timbering 2.05 .10 Excavation 8.20 .40 Total $18.65 $ .91 The cost of superintendence, sundries, and plant rental would amount to about $10 per ft. or .50 per yard at a low estimate, and the cost of the steel sheet piling, if charged entirely to this job, would amount to $110 per ft., or $5.30 per yard. 4. Caisson 26 ft. outside diameter, 21 ft. inside diameter, sunk through 56 ft. semi-liquid mud and boulders: Per Cubic Yard Per Foot Excavation [ Materials $ 27.00 $1.35 Concrete { Labor . 7.00 .35 [ Forms and shoe ,*' 23.00 1.15 Sinking caisson ; 38.00 1.90 Plant erection .",.. 3.00 .15 Superintendence ..*... 5.00 .25 Sundry ...... 5.00 .25 Coal and power 6.00 .30 Total $114.00 $5.70 SEALING THE CAISSON TO ROCK After the cutting edge of a caisson has reached rock, it is still necessary to construct a seal to permanently exclude sand and water. Often a stratum of stiff clay or disin- tegrated shale is found under the soft material and imme- diately over the rock. If this occurs the cutting edge will sink into it, automatically shutting out water until a concrete wall is built; if not, the making of the seal will be very troublesome. 52 PRACTICAL SHAFT SINKING Running mud may be checked long enough to allow it to harden by caulking under the shoe with blocks of wood and old sacks. Streams of water and quicksand require a wedging curb of some kind. The English method of sealing tubbing to rock can be applied; this may be done, Fig. 19, by cutting out the rock under the shoe until the cutting edge attains a fair bearing all around, then driving numerous wooden wedges into the crack until the w r ater is blocked back. Another plan, Fig. 20, is to lead the water to the center of the shaft through pipes set opposite the main #;& FIG. 19 FIG. 20 feeders. A brick or concrete wall is then built from the rock to the caisson, surrounding the pipes and forcing all the water through them. When this masonry has set hard enough to stand the water pressure, the pipes are plugged. Several small pipes should also be built into the wall so that grout can be pumped back of it to take up small leaks. With either method great care is necessary, in commencing the rock excavation, to avoid opening up a new leak. Sometimes the quantity of water may be so great that it cannot be shut off as described. If it is anticipated that the ground will be very wet, provision should be made in the design of the caisson for the use of compressed air as described below. This provision was made in the SINKING THROUGH SURFACE f>3 FIG. 21. Steel Shoe for D., L. & W. Caisson FIG. 22. Shoe and Form for Bottom of D., L. & W. Caisson 54 PRACTICAL SHAFT SINKING D., L. & W. caisson referred to above, although air was not used. The following notes on D., L. & W. caisson, taken from the Engineering News for September 28, 1908, are of interest. In sinking the shaft, after the surface had been removed with plows and scrapers and the bottom of the excavation FIG. 23. Showing Reenforcement for D., L. & W. Concrete Caisson made perfectly level, a steel shoe, shown in Fig. 21, was placed on the bottom of the excavation. This was made of f-in. plate, was 24 in. wide, 32 in. high, and reenforced, as shown, with riveted angles. The shelf which formed the base for the concrete was placed 8 in. above the toe of the vertical plate. The outside dimensions of the cutting shoe were 28 X 59 ft. 5 in. The outside form for the concrete was built up flush with the outside edge of the shoe. The SINKING THROUGH SURFACE 55 inside form at the bottom was inclined as shown in Fig. 22, being given a batter until the wall was 7 ft. thick on the sides and 5 ft. on the ends, when vertical forms were put in place. The concrete was reenforced with tie-rods, as shown in Fig. 23, and the walls were decreased in thickness in steps, as shown in Fig. 25, until they reached a uniform thickness of 2 ft. 8 in. at the top. When a height of 20 ft. of the concrete was reached, the bottom forms were removed FIG. 24. D., L. & W. Caisson Ready for Sinking and the concrete caisson then carefully leveled preparatory to sinking. In order to provide for the contingency of having to resort to compressed air in sinking in case the inflow of water proved too great to be handled by pumps, arrangements were made to put in an air deck in case of necessity. Sinking was carried on day and night, and the excavating gang consisted of a foreman and sixteen men to each shift. The materials were hoisted in buckets by means of derricks, as shown in Fig. 24. Just as the caisson reached the rock which was being cleaned off preparatory to putting in the seal, the river rose and the shaft was PRACTICAL SHAFT SINKING Longitudinal Section. FIG. 25. Plan and Sections of D. Crofts Section. L. & W. Caisson Walls SINKING THROUGH SURFACE 57 flooded. It was found impossible to pump it out and the shaft was allowed to fill, to remain full until the river had subsided. When the caisson had sunk to the level of the rock, it was found that a temporary seal would have to be put in place during the construction of the permanent seal. This temporary seal was made of yellow pine blocks, 12 x 12 in. in size, and wedges a, Fig. 26. Six-inch bleeder pipes were left to drain off the water while the seal was being FIG. 26 put in place. The pipes were closed after the temporary seal had been completed. To provide a place for the permanent seal it was necessary to take out rock for a depth of 20 ft., so as to build a wall to carry the caisson. During the blasting of this rock great care had to be taken to prevent jarring out the temporary seal. As the rock was being excavated a grout was forced back of the temporary blocking by means of a grout pump with an air pressure of 80 Ibs. In order to give a firm footing for the concrete wall the 58 PRACTICAL SHAFT SINKING rock was recessed so as to form a toe for the wall, and in order to give good contact between the underpinning wall and the caisson, the lower edge of the caisson was roughened. Fig. 26 shows the method of making the permanent seal between the caisson and the concrete foundation. The concrete c was put in place as soon as possible after the rock excavation had been completed, and was of the form shown. Next the ring of concrete d was placed, and grout was then pumped into the pipes after the concrete c and d had set. The final wedge of concrete e was laid after the concrete lower down had set and everything below had been made thoroughly tight, the edge between e and d being caulked after the pipe had been grouted; g is broken stone packed in between a brick dam and the wooden seal; the brick dam is intended to lead the water to the pipes 6. CHAPTER IV SINKING THROUGH SOFT GROUND PNEUMATIC PROCESS SHIELD METHOD. SOFT GROUND FOR sinking through soft ground containing more water than can be pumped, the three methods referred to in Chapter III have been developed in this country and abroad. They may be described as follows: THE PNEUMATIC PROCESS The pneumatic caisson is an application of the principle of the diving bell that has been widely used for founding deep piers. It is also used for soft-ground shafts, particu- larly construction shafts from which tunnels are to be driven under compressed air. A caisson is constructed similar to the open caissons already described, except that an air- tight deck is built over the entire opening 8 or 10 ft. above the cutting edge, Fig. 26. The deck is made strong enough to resist an air pressure equivalent to the hydrostatic head at tne depth which the caisson is expected to reach. One or more openings in the deck are provided, fitted with air locks which retain air pressure but permit the entrance of men and the removal of spoil. The caisson is constructed above the surface and sunk by excavating under the cutting edge as in the open type. The air pressure is raised as the caisson sinks and is always kept slightly in excess of the water pressure at the cutting edge. Water is absolutely excluded no matter how wet and soft the material the work is done in the dry. In this way shafts can be sunk through river silt and flowing quick- sands that cannot be handled in the open. 59 60 PRACTICAL SHAFT SINKING The cost of excavation under compressed air is in general much higher than that of open work. In the first place grab buckets cannot be hoisted through an air lock, so hand digging is necessary; second, a special class of high- priced laborers must be employed whose wages increase with the depth, while the length of the shifts must be reduced; third, the air locks applicable to caissons are costly to build, and as their construction is covered by patents controlled by one or two corporations, they are quite costly to rent; fourth, the masonry of the caissons must be made very heavy to overcome the upward pressure of the air. Some grounds, however, can be " blown" out of the caisson and very little digging is necessary; in this case excavation is cheap. The limit for pneumatic sinking in loose ground is, in general, 100 ft. below water level, as men cannot stand a pressure greater than that corresponding to this depth. The deck in a shaft caisson must be removable, and is, therefore, made of timber or steel, fitted into a recess left in the wall. Two openings should be provided, one in the middle for the excavation^ lock and another for the man lock. American locks are now standardized to fit a 36-in. circular opening. Small openings must also be made in the deck for the air connections and the "blow pipe." A man lock consists of a steel cylinder, about 4 ft. in diameter and 8 ft. long, with flanged head. Eighteen-inch openings in the head are fitted with doors which swing downwards in opening, and close against a rubber gasket. A small hole in each head, closed by a stop-cock inside the lock, permits the entrance of compressed air from the caisson and its escape to the atmosphere. The lower door and stop-cock being closed, the upper door is opened and several men enter the lock. The upper door is then closed from outside, and a lock-tender standing inside the lock closes the upper and opens the lower stop-cock. When the pressure in the lock has become equal to that in the caisson, he opens the lower door and the men climb down a SINKING THROUGH SOFT GROUND 61 ladder to the bottom. In letting men out the process is reversed. The locking through of men is the most precarious part of compressed-air work. Too quick an application of pres- sure causes "blocking of the ears" intolerable pain in the ears and head due to unequal pressure on the two sides of the ear drum and too quick a reduction of pressure Hoist Rope.- Stuffing Box. 2 Air Outlet. Doors. FIG. 27. Pneumatic Caisson may cause the "bends" caisson workers' paralysis always dangerous and sometimes fatal. For pressures below 20 Ibs., men accustomed to the work can be locked through safely in two or three minutes and can work eight- hour shifts; at higher pressures the locking time must be increased and the length of the shifts decreased. With 45 Ibs. of air, forty-five-minute shifts are worked and twenty-five minutes must be taken in locking through. 62 PRACTICAL SHAFT SINKING The principle of the excavation lock is the same as that of the man lock, but the doors and valves are all controlled from outside. The patented " straight-through" lock is the best type, in fact the only satisfactory type for caisson work. Several forms are made, all of which require the bucket to be hoisted on a single rope. In the ''pot-lid" lock the rope passes through a stuffing-box in the middle of the upper door, which is literally a lid fastened to the lock by six heavy bolts hinged to the lock and engaging slots in the edge of the door. The door is carried by a buffer at the lower end of the rope. When a bucket is lowered into the lock, the upper door is also lowered on to its seat. The lock-tender, who stands outside, raises the hinge bolts into their slots and tightens the nuts before opening the lower door. In consequence of the continual tightening and loosening of the bolts this lock is rather slow in operation, but it is very simple. Other forms of the straight-through lock have the upper door in two halves which close upon a stuffing-box on the rope. In this way only the stuffing-box is lifted instead of the entire door, and the operation is much quicker. In one type the doors are operated by high-pressure air cylinders. The air pumped into the caisson by the compressors escapes by forcing its way out through the ground close under the cutting edge. As it is often necessary to excavate several feet below the cutting edge to sink the caisson, some provision must be made to remove the water that collects in the depression. This can of course be done with a pump driven by high-pressure air, but it is also possible to blow the water out directly. A 4 to 6 in. pipe, closed by a stop- cock at the lower end, is led through the deck and out over the top of the caisson, and a suction hose reaching the sump is attached to the lower side of the stop-cock. An opening, closed by a small valve or a wooden plug, is made in the pipe above the stop-cock. When the stop-cock is open the air pressure lifts the water into the pipe; the small SINKING THROUGH SOFT GROUND 63 valve is opened at the same time and a quantity of air flows in and mixes with the stream of water, decreasing its specific gravity until the weight of the whole column of water is less than the air pressure. The water is then driven com- pletely out of the caisson. By replacing the valve with a small high-pressure air connection it has been possible to raise water out of a caisson 70 ft. deep with 13 Ibs. of air. Fine sand and silt containing much water can be blown out through the pipe, and caissons have been sunk without hoisting a bucket of dirt. The use of compressed air makes it very much easier to seal the caisson to rock. There is of course no trouble about keeping the water out ; the difficulty is to prevent the air from blowing the grout out of the concrete, leaving it porous. One plan is to lay a strip of heavy duck over the crack, nailing one edge to the caisson and the other to the rock. Concrete is then laid on top of this duck. Some kinds of very wet ground possess considerable viscosity. In these the pneumatic process can be worked to a greater depth than is theoretically possible by reducing the pressure and blowing out the mud and water that flow in under the cutting edge. One example of this has been cited where water was raised 70 ft. with 13 Ibs. of air; in England recently several piers were founded at a depth of 130 ft. below water level with 45 Ibs. of air pressure. Under such conditions the difference between the hydrostatic pressure and the air pressure is accounted for by internal friction of the water and the ground. It is probable also that the actual hydrostatic head is Deduced by the ah* bubbles which escape under the cutting edge into the sur- rounding ground. THE SHIELD METHOD Shields, similar in principle to those so extensively used for subaqueous soft-ground tunnels, have also been applied to soft-ground shafts, Fig. 28. A shoe is constructed with a cutting edge slightly larger than the outside of the com- 64 PRACTICAL SHAFT SINKING pleted shaft lining; a vertical lap plate or shield is attached to the outer perimeter of the shoe, and a number of screw (or hydraulic) jacks are set on top of the shoe and inside the shield plate. The frame of the shoe is sometimes made of wood, but steel is preferable. The shield is made of i to f-in. plate iron and extends from 18 in. to 3 ft. above ! Cross Bunfons FIG. 28.* Shield Method of Sinking the top of the shoe proper. The method of operation is as follows: As soon as the shaft is started, bearing timbers or trusses are constructed to hang the lining from as previously described in connection with forepoling. The shoe is assembled in place with jacks screwed down, and the shaft lining is completed from the surface to the heads of the * Figs. 28, 34, 36, 37, and 47 are reproduced from the copyrighted instruc- tion papers and bound volumes of the International Correspondence Schools by special permission of the International Textbook Company. SINKING THROUGH SOFT GROUND 65 jacks. Excavation is then started and the shoe sinks until enough distance is gained to allow another course of lining to be placed beneath the completed section and inside the shield. If the jacks are used to force the shoe down, they must be withdrawn before the course of lining can be placed. The upper edge of the shield must always be kept above the lower edge of the completed lining, and to insure this in bad ground it is necessary to hang the shoe from the bearing timbers with chains and ratchet jacks. Sometimes shoes are made so that the opening can be completely closed with steel plates to prevent an inrush of sand. Tunnels driven with shields are circular and lined with rings of cast-iron segments 2 ft. wide. Many European shafts are lined this way, but the American shafts to which the shield method has been applied are rectangular and lined with "skin-to-skin" timbers or plank laid flat. The chief disadvantage of a shield, even at a moderate depth, is its liability to hang up on a boulder on one side while the other side settles, thus wedging itself and throwing the shaft out of line. This tendency can be largely overcome by the proper suspension of the shield, but the depth which can be reached is limited when the ground is soft and wet enough to exert fluid pressure. At 100 ft. below ground- water level, for example, the pressure of wet quicksand will at least be 45 Ibs. per square inch, sufficient to force enough sand and water to flood the shaft through a very small opening. It is impossible to jack a closed shoe down, displacing the ground under it. CHAPTER V SINKING IN ROCK ARRANGEMENT OF HOLES TOOLS AND METHODS USED IN DRILLING COSTS AND SPEED DYNAMITE and the power drill have made solid rock the easiest material through which to sink a shaft, and prac- tically all American mining shafts are in rock for the greater part of their depth. As has been said before, hand sinking is the cheapest and quickest method; although a boring process has been developed, it is only applied where such immense quantities of water are encountered that hand sinking is impossible. Outside of the boring process, the improvements in rock sinking have all related to breaking the rock and hoisting it. No practicable mechanical excavator or loader has yet been devised. Grab buckets that work well in soft ground are failures in blasted rock. A steam shovel, useful in a tunnel, is of course out of the question in the bottom of a sinking shaft. Drilling and Blasting. The universal method of shaft sinking in rock is to drill a number of holes in the bottom, charge them with dynamite and shoot them, and to load the broken rock by hand into shaft buckets which are then hoisted out. When all the loose rock has been removed the process is repeated. As it is very difficult to drill holes through loose rock, the broken material must be all removed before the next round of holes is started. This creates an additional difficulty for the mechanical digger, for while a grab might be made to remove most of the loose rock after a blast, hand work would still have to be resorted to to get the bottom ready for drilling. Shafts are drilled on the ''center-cut" principle. Eight SINKING IN ROCK 67 or ten holes are drilled on a slant, separated at the top but converging, thus forming a wedge known as the "sump." "Reliever," or bench, holes are drilled back of the sump holes, each row being more nearly vertical; the end or out- side holes point slightly away from the vertical and toward the wall line of the shaft. The sump is first shot and the broken rock removed or "mucked" out, forming a cavity into which the bench rounds can be successively shot. All muck should be removed before each succeeding round is shot. FIG. 29. Shaft (a) Two systems of drilling and mucking exist. In the first the holes for the entire cut sump and benches are drilled at one time, the sump is shot, and then the benches as required. In the second the sump only is drilled and shot, and the benches are drilled while the sump is being mucked. The first plan is particularly applicable to small shafts and to circular shafts; a rectangular or elliptical shape is needed to give room for simultaneous drilling and mucking. Fumeless, or gelatine, dynamite should in all cases be used for underground work. The fumes from ordinary glycerine dynamite make it imposssible for the men to get back to work promptly after a shot. The strength of the dynamite used depends on the character of the rock, but PRACTICAL SHAFT SINKING 40 and 60 per cent, gelatine are the most common strengths used. The number and depth of the holes and the quantities of powder loaded vary so greatly with the size of the shaft and the nature of the rock that no general rules can be stated. The systems actually used at several shafts were as follows: (a) Shaft 13 X 26 ft., through Western Pennsylvania coal measures: Shale, slate, and limestone; horizontal stratification; holes as in Fig. 29; 40 per cent, gelatine: Number Depth Inclination with Vertical Loaded with Sump 8 Feet 10 Degrees 35 Pounds 4 Relievers 8 8 25 3 Benches End Total charge 8 8 8 8 10 back 2^ 2 96 Average gain per cut, 6 feet. Average gain per week of 19 shifts, 24 feet (no timber). Mucking and drilling simultaneous; 2 drills used on 1 bar. (6) Shaft 14 X 48 ft., through anthracite measures: Red sandstone; stratification horizontal; holes as in Fig. 30; 40 per cent, gelatine: Number Depth Inclination Loaded with Sump Relievers Benches End ' Total charge per round 8 8 24 8 Feet 10 8 8 8 Degrees 35 25 lOtoO 10 back Pounds 5 4 3 3 168 Average gain per cut, 6 feet. Average gain per week of 18 shifts, 16 feet. Mucking and drilling simultaneous; 2 drills used on 1 bar. (c) Shaft 10 X 22 ft., through quartz conglomerate (Shawangunk grit) ; horizontal stratification, but very few bedding planes; holes as in Fig. 31; 60 per cent, gelatine: SINKING IN ROCK Number Depth Inclination Loaded with Sump 8 Feet 10 Degre 35 Pounds 3-i Sump 4 8 o Ql Relievers Benches End , Total charge per round 8 8 8 9 8 8 25 10 back 21 2 2 94 Average gain per cut, 5 feet. Average gain per week of 20 shifts, 22 feet. Mucking and drilling simultaneous; 5 drills used on 2 bars. The four additional sump holes shown were used on account of extra hardness of the rock. (d) Shaft elliptical, 19 ft. 4 in. X 33 ft., through West Virginia coal measures: Hard gray sandstone; 40 per cent, gelatine; holes as in Fig. 32; horizontal stratification: Number Depth Inclination Loaded with Feet Degrees Pounds Sump 10 12 35 5 Relievers 8 10 25 4 Benches 14 10 10 4 End 6 10 10 back 3 Total charge per round 156 Average gain per cut, 8 feet. Average gain per week of 20 shifts, 18 feet. Mucking and drilling simultaneous; 3 drills used on 1 long bar, 1 short bar. (e) Shaft circular, 17 ft. diameter, through Hamilton and Marcellus shales: Rock distorted; stratification irregular; holes as in Fig. 33, but about 45 degrees; 60 per cent, gelatine: Number Depth Inclination Loaded with Feet Degrees Pounds Sump 6 8 35 2| 8 6 20 u Rib 16 6 10 back 1 Total charge per round 43 Average gain per cut, 5 feet. Average gain per week of 19 shifts, 33 feet. All drilling on one shift, mucking on two shifts; 5 drills used on 5 tripods. 70 PRACTICAL SHAFT SINKING Drilling Tools. Hand drilling, once universal, has been entirely superseded in the United State by compressed-air drilling, and it is in fact difficult to obtain hammer men. FIG. 31. Shaft (c) In other countries where labor is cheap, drilling is still done by hand. In the commonest method, a drill or " jumper" FIG. 32. Shaft (d) FIG. 33. Shaft (e) of 1-in. steel is turned by one man and struck by one or two others with 8-lb., double-faced hammers, Fig. 34a. Americans and Europeans use a 30-in. stiff handle; the Southern negro prefers to "drive steel" with a slightly longer SINKING IN ROCK 71 handle whittled down until it bends like a whip. Jumpers are given a single cutting edge, usually curved, Fig. 40. Two men should strike each steel wherever practicable, as they can obviously drill twice as fast as a single striker at three-fourths the cost. As much depends on the man that turns the steel as on the striker, for considerable skill is needed to produce a round, straight hole. Three good men can drill If -in. holes in hard sandstone at the rate of 2 ft. per hour. FIG. 34a FIG. 34 In the Tyrol a system of single-handed drilling has been developed. The driller turns a light steel with one hand and wields a 4-lb. hammer, Fig. 346, with the other. A skil- ful man can thus drill 3-ft. holes quite rapidly, but the holes are too small for regular shaft sinking. For slate, churn drills, Fig. 38, are often used. The drill consists of a straight bar, 6 to 12 ft. long, with a bit at each end. An iron weight is sometimes welded around or forged into the drill 2 ft. from one end, thus increasing the weight 72 PRACTICAL SHAFT SINKING of the drill without increasing its length or diameter. The drill is handled by two or three men. When the weighted drill is used, the hole is started with the short end, and when it has reached a depth of 2 ft. the drill is reversed. FIG. 35 The reciprocating, compressed air drill is the most widely used machine for drilling rock. It was first put into prac- tical use by Mr. Fowle, of Boston, in the construction of the Hoosac tunnel, and since then has steadily grown in popularity. It is turned out by the thousands by the SINKING IN ROCK 73 Ingersoll-Rand Co., the Sullivan Machinery Co., the McKiernan Drill Co., and others, and although each maker has certain features of his own, especially in the valve arrangement, the general design is standardized and the general features are shown in Fig. 36. Piston and rod are turned out of a single billet of special steel, and to the end of the rod the drill steel is rigidly attached by a U-bolt chuck. The cylinder is made of cast-iron and slides longi- tudinally in a guide frame (or shell) clamped to the drill mounting. As the drill cuts into the rock, the cylinder is fed forward by a square-thread screw mounted on the frame. The piston is rotated mechanically by a "rifle bar" and ratchet so that the cutting edge of the bit will not strike two successive blows in the same spot. This rotative effect is necessary to drill a round hole. The machine commonly used for shaft sinking has a 3|-in. cylinder and a 6|-in. stroke, weighs 280 Ibs., and will drill down holes in hard rock at the rate of about 7 ft. per hour, including time lost in changing steels. The length of feed is 24 in., hence the drills must be changed every 2 ft. The starter is 2 ft. long beyond the shank (the portion of the drill grasped by the chuck), and the following steels are 4 ft., 6 ft., 8 ft., etc., respectively. (See Fig. 39.) Drill steels are usually sharpened with a + bit, although X bits and straight I bits are sometimes used. Where a large number of drills are in operation a sharpening machine may be used to advantage. Two types of valve motion can be obtained. In the first, the valve which controls the piston is thrown by a tappet struck by the piston itself; the Rand " Little Giant" is an example of this. In the second, a piston valve is used which is thrown by a difference in air pressure on the two ends. The Sullivan "Slugger" is a drill of this type. The Sergeant drill is a compromise, having an auxiliary valve, driven by contact with the piston, which governs the air pressure on the ends of the main piston valve. The Slugger type strikes a hard, uncushioned blow and is adapted to 74 PRACTICAL SHAFT SINK INC, SINKING IN ROCK 75 use in hard rock with compressed air. Wet steam will not operate the valve readily, and the drill is slow if wet steam is used. The tappet drill, on the other hand, having a posi- tive valve motion will do good work on wet steam. Its blow is slightly cushioned. The auxiliary-valve drill strikes a hard blow, will run by steam, and in addition has the advantage of a variable stroke. This feature makes it easier to start a hole. A good many types of air-hammer drill have been recently developed, and have replaced the reciprocating types for light work. In these the drill steel is struck by a reciprocating hammer and has very little motion of its own. The drill steel is hollow, and the powdered rock is blown out of the hole by a portion of the exhaust air led to the cutting face through the hole in the steel. The Water Leyner drill, Fig. 35, which is now built to compete with the larger sizes of reciprocating drills, works on the hammer principle. In this the cuttings are removed by a stream of water pumped through the hollow steel to the cutting face; a portion of the exhaust air is allowed to mix with the water. This drill has made some remarkable records in hard rock tunnels in the West. A great advan- tage of the drill is that no dust is created in drilling up-holes in tunnels, making this work very much more healthy for the drill runners. In rectangular shafts, drills are mounted on " shaft bars," or single screw columns, Fig. 37. The drill itself is held by a clamp, which, when its bolts are loosened, can be slid along or revolved around the bar, at the same time per- mitting the drill to be swung sidewise to any angle. When the clamp bolts are tightened the drill is rigidly held in posi- tion. The bar is set horizontally across the shaft, wooden blocking being used to form a good bearing between its ends and the walls of the shaft. Two and sometimes three drills are mounted on each bar. "Column arms," used for off- setting the drill, do not work satisfactorily with a shaft bar, and besides are unnecessary in a rectangular shaft. 76 PRACTICAL SHAFT SINKING In circular shafts it is difficult to cover the area to be drilled with a straight bar, and in the writer's opinion it is best to mount the drills on tripods, Fig. 34. The tripod, while it possesses all the adjustability of other forms of mounting, is less rigid and more cumbersome. To do good work all loose rock should be removed and the legs set on solid rock. This feature, however, is not objectionable in a shaft where mucking and drilling are not carried on simul- taneously. Before blasting, the drills and mountings must of course be hoisted out of the shaft. In England, a drilling frame for use in circular shafts has been patented. This consists of a ring from which six bars, on which the drills are mounted, project radially. The ring is supported by legs and held rigid by jack-screws in the ends of the six bars. The chief advantage of this frame is that it is unnecessary to detach all the drills before blasting; the whole can be hoisted off the bottom and hung in the shaft without hindering the SINKING IN ROCK 77 78 * PRACTICAL SHAFT SINKING passage of the bucket which passes up and down through the ring. Another advantage of the frame is that the manifold is attached to it, the drills being connected to the manifold by short pieces of hose. It is thus necessary to have only one main air hose hanging in the shaft instead of a small hose for each machine. The best grade of canvas and rubber hose should be used for the drills, wire wound for air, and marlin wound for steam. " Steam hose" should be ordered always for use with steam, as "air hose" will not stand heat. A sec- tion of 1-in. hose 50 ft. long is used for operating each drill. Operation. Shaft sinking is usually carried on twenty- four hours a day. The inside work is done by three shifts of men working eight hours each, the outside by three 8-hour or two 12-hour shifts. The 12-hour outside shift is customary in the coal fields; elsewhere, the 8-hour shift for every one is prevalent. Shifts are usually changed at 7 A.M. and 3 and 11 P.M., sometimes an hour later. The men are given twenty minutes for lunch in the middle of each shift. Wages vary with the locality, but in general men are paid better for drilling and mucking in a shaft than in any other kind of rock excavation. On account of the high wages paid in America machine drilling is universal, and the shifts are limited to the number of men that can be worked to the best advantage. Speed is not attempted at the expense of efficiency. In South Africa, on the other hand, Kaffir labor is cheap, hand drilling is usual, and as many men are worked as the shafts will hold. The great depth of the shafts on the Rand makes the highest possible speed desirable, even at an increased cost. In both countries speed is increased without an increase of cost by the payment of a bonus to the sinkers as a reward for additional progress. The size of the shifts for any given shaft depends upon the number of drills required and upon the experience and ability of the sinkers obtainable. With first-class men, SINKING IN ROCK 79 the men on each shift at the 13 X 26 ft. shaft referred to before as (a) would be as follows: Inside men, 8 hours: One shift boss, at $3; two drillers, at $2.75; two helpers, at $2.50; six muckers, at $2.25. Outside men, 12 hours: One engineer; one head tender; three car men on dump; one fireman; one compressor man. General outside, 10 hours: One foreman; one mechanic; two carpenters (on timber) ; one blacksmith and helper. The 17-ft. circular shaft (e) would require: Drilling shift: One shift boss; five drillers; five helpers; one extra man. Mucking shifts: One shift boss; nine muckers. Outside same as shaft (a). In South African shafts, which are usually about 9 X 26 ft., when drilling is done by hand, each shift consists of one white shift boss and about 35 Kaffir laborers who drill or muck as may be required. Thorough organization is essential to progress and economy. Each man must know his place and take it without losing time in getting started. Any condition that prevents systematic work is fatal to economy. For instance an inflow of water, sufficient to cause a loss of time after every blast while the bottom is being pumped dry, will lessen the rate of sinking far more than can be calculated by adding together the actual delays. Ventilation. Foul air and powder smoke in the shaft bottom hinder work almost as much as water. As a rule vertical shafts ventilate themselves surprisingly well to a depth of 400 to 500 ft., but at greater depths and sometimes at much lesser depths, artificial ventilation must be resorted to. The cheapest method, where the natural draft needs only a slight assistance, is an "air box," or wooden pipe carried up one compartment of the shaft; into this box is turned a jet of air or steam or the exhaust of the pump, if one is used. The box is built of 1 X 12 in. boards. Another way to help natural ventilation in a rectangular shaft is to 80 PRACTICAL SHAFT SINKING divide the shaft into two compartments with a brattice attached to a row of bun tons; one compartment will then establish itself as an upcast, the other as a downcast. If all steam pipes to pumps are kept in one compartment this action is certain to occur. In any case steam pipes should be kept together in one end of the shaft. In deep shafts positive ventilation is best assured by the use of a fan or blower discharging into a large air pipe carried down the shaft and lengthened from time to time as the shaft deepens. A 15-in. standard volume blower, engine- or motor-driven, is sufficient to ventilate a shaft to any ordinary depth. The pipe may be made of boards, canvas, or light, galvanized sheet iron. The latter, although more expensive than wood or canvas, is air-tight and is not liable to injury from concussion. Progress. Progress in shaft sinking is influenced by so many different conditions quality of rock, size and shape of the shaft, presence or absence of water, efficiency of labor and plant that it is very hard to make any general statements concerning it. The best progress records are made in deep rectangular shafts on the Rand, in Transvaal, South Africa. These shafts, as has been said before, have a section about 9 X 26 ft. hi the rock; work is carried on by three 8-hour shifts 7 days a week; two compartments are used for hoisting, and every man that can be worked is put into the shaft. Kaffir labor is not only cheap, but the Kaffir will work under conditions of crowding to which a white man will not submit. The records made in several South African shafts are given in Table 1 : the average progress is seen to be about 135 ft. per month, and the maximum 213.5 ft. The progress in this country under normal conditions ranges from 60 to 80 ft. for rectangular timbered shafts, although very much higher speeds are sometimes reported. The soft shale in the coal fields of the Middle Western states is easy to drill and shoot. Good records are made in Kansas and Southern Illinois. An account of a shaft near Atchison, SINKING IN ROCK 81 Kan., published in the Engineering and Mining Journal for July 26, 1902, states that the daily progress in soft shale was 7 ft. No monthly figures were given. A good record was recently made on a 17-ft. circular shaft in the " Hudson River shale" (dark blue sandstone and sandy slate) on the New York Aqueduct. The system of drilling and muck- ing used at this shaft is described above under (e) ; .the rock was quite hard but broke readily. The average progress made here is shown in the tabulation of American shafts, Table 2. The best month's work is 177 ft. No work was done on Sundays. The writer believes this to be a record for American shafts.* The rate of progress in the European circular shafts lies between the American and the African rate. The rock penetrated is in general softer than that found in this country. Tables 1 and 2 give the dimensions of a number of shafts and the progress made in them. Wherever obtainable, the nature of the rock penetrated and the cost per fo'ot is given. The figures were obtained from various articles in the technical papers, from the proceedings of various mining institutes, and from the writer's own records; some of the South African data were taken from the "Deep Level Mines of the Rand," by G. A. Denny, 1902. Cost. Cost figures cover a wider range than progress figures and are harder to get. The cheapest shaft on record is the one near Atchison, referred to above, the cost of which, as stated, was $7 per foot. This cost stands alone in its glory as the tabulated figures show. Mr. Henry Rawie published in Mines and Minerals an itemized statement of the. costs of a shaft sunk in West Virginia, in 1906. These ran as follows: * Since the above was written, the Breakneck Shaft. on the New York Aqueduct was sunk 183 ft. in a month. The rock was hard granite. The system used was the same as at No. 1 Moodna, but six 3f drills on tripods were used on the drilling shift. One mucking shift only was worked on Sunday; no drilling shift. 82 PRACTICAL SHAFT SINKING HOIST SHAFT, 14 FT. X 22 FT., 180 FT. DEEP Per Foot Labor, sinking and timbering $24.70 Plant 5.55 Superintendence Explosives 3.88 Coal 2.55 Timber 6.67 Miscellaneous 5.55 $48.90 The sinking costs of a pair of shafts sunk in Western Pennsylvania a year later were as follows : HOIST SHAFT, 13 FT. X 26 FT., 422 FT. DEEP Per Foot Labor, sinking $51.00 Plant 2.40 Superintendence 4.35 Explosives 2.75 Coal 5.50 Oil 60 Freight 50 Miscellaneous 7.90 Total -.... $75.00 AIR SHAFT, 13 FT. X 22 FT., 383 FT. DEEP Per Foot Labor, sinking $57.50 Plant 2.40 Superintendence 4.90 Explosives 3.00 Coal 6.05 Oil 60 Freight 50 Miscellaneous 7.14 Total $82.09 Water per minute: Hoist shaft, 50 gallons; air shaft, 120 gallons. Costs have risen greatly in the last decade, since no sub- stantial improvements in methods or machinery have been made to offset the increase in wages. Contract prices are SINKING IN ROCK 83 qioqqqqqqt^q sssi eo .H ^ ^ ^ ^ 3 2232332232 OOOOOOOOi-tOO XXXXXXXXX I a; a> a> a) liill c " if! o. L qt>;c co icqqqqqq d os S ** J o ^ CQ >H O t^ CD OO'^Ot^-O^'C OCOOOO "H T^ ^ ^ u X X X X 'jl X X x X .1 I OSCOOas^TtiOJ C^ < i JH .^^ * gou ;soo^^^ g ri 22 o O O '0^1^^^ S tf liii oSco^^^ 84 PRACTICAL SHAFT SINKING not generally obtainable, as most shafts are put down by private corporations, but prices high enough to include a good profit to the contractor eight to ten years ago would not cover his costs to-day. Twenty-five shafts ranging in depth from 350 to over 1000 ft. are required for the portion of the New York Aque- duct now under construction. All but two of these have been let by contract, and the bid prices are public prop- erty. The bids, however, are unbalanced in every case, and do not give a fair idea of shaft prices. They range from $175 to $350 per foot. CHAPTER VI THE SINKING-DRUM PROCESS. MAMMOTH PUMP. THE FREEZING PROCESS Sinking-drum Process. For sinking through the very great depths of water-bearing sand and clay that exist in some of the German mining districts, a method has been developed that does not require any hand work in the shaft bottom until the lining is completed to rock. The shafts are necessarily circular and are lined with cast-iron tubbing. A heavy masonry caisson, with an inside diameter, somewhat greater than that of the finished shaft desired, is first con- structed and sunk for 50 or 60 ft., as described in a previous chapter. If the ground beneath the cutting edge is sufficiently firm, it is leveled off and a foundation ring of masonry built under the tapered part of the wall. If not, a concrete floor is laid over the bottom (under water if necessary) and the caisson is pumped out. A heavy iron ring projecting inside the face of the wall all around is built into the masonry foundation ring or into a groove cut in the wall above the concrete floor. A second ring, placed near the top of the caisson, is connected to the first with heavy iron rods, and the space between the rings and around the rods is filled with masonry, forming an inner tube. The upper ring pro- jects inside this inner tube and serves as a base for a circle of powerful hydraulic jacks acting downward. A very strong cast-steel shoe or cutting edge with an outside diameter slightly less than the inside diameter of the tube is then assembled on the shaft bottom, and rings of cast-iron tubbing bolted together are built up from the top of the shoe to the heads of the jacks. If a concrete floor has been laid it is broken up with a huge churn drill, excavation 85 86 PRACTICAL SHAFT SINKING is started with a grab bucket or some other mechanical digger, and the shoe and tubbing commence to sink of their own weight. The inner masonry lining acts as a guide for the iron sinking drum, and must therefore be built with its axis exactly vertical, correcting any deviation that may have occurred in sinking the caisson. The rubbing surface is usually formed by I-beams built into the masonry. When motion ceases, the jacks are brought into play and the drum is forced down, additional rings of tubbing being built up under the heads of the jacks. When the first drum can be forced no farther, the bottom of the shaft is plugged with concrete, the water is pumped out, and a second sinking drum built up inside the first. The concrete is broken up as before, the jacks shifted so as to engage the top of the inner drum, and sinking is resumed. As many as four drums have been used, reaching in one place a depth of 508 ft. The three methods used for excavation under water inside the drum are: The Grab Bucket. The action of a clam-shell or orange-peel bucket is too well known to require explanation. Either bucket will handle coarse sand, gravel, and boulders to advantage, but will not retain fine wet sand through a long hoist, and will not dig tough clay. The Sack Borer. This is a gigantic auger with the rigid stem extending up the center of the shaft, Fig. 41. The stem is constructed of heavy flanged pipes bolted together, and is terminated at the upper end by a splined section which serves as the shaft of a large horizontal worm-wheel. A hoisting rope, leading to a powerful engine and attached to a swivel at the top of the splined section, suspends the borer. The stem is turned by an engine acting through the worm-gear and its worm, and is lowered gradually by the hoisting rope. When the top of the splined section reaches the worm-gear, it is disconnected from the stem proper and raised, and another section of standard pipe is added beneath it. Cross-arms, fitted with rollers at their ends, are attached THE SINKING-DRUM PROCESS 87 to the stem at intervals; the rollers bear against the sides of the completed shaft and prevent the stem from buckling. The material cut by the borer is collected in two heavy FIG. 41. Sack Borer canvas sacks fastened to the backs of the cutters. Formerly they were rigidly attached, and the whole apparatus was hoisted every time the sacks were filled. Now, however, the sacks are mounted on frames sliding on two pairs of 88 PRACTICAL SHAFT SINKING guides attached to the cross-arms on the stem, and are hoisted by light, independent engines. The sack borer is adapted to clay and sand. The Mammoth Pump. This is an application of the air lift, used in conjunction with a percussion borer or large churn drill, Fig. 43. A discharge pipe A, open at both ends, is carried down along the boring rod from the surface and is terminated just above the point of the borer. A com- pressed-air pipe B is also carried down the rod and connected into the discharge or suction pipe A near the bottom. The FIQ. 42. Construction of Sinking Drum for Hydraulic Flushing Process borer being in operation, the air is turned on and a stream of water, mud, and sand is lifted through the discharge pipe. The pump will handle practically any material that will enter the discharge pipe. The chief difficulty with the sinking drum has been the thickness of iron required to withstand the earth pressure at great depth, and uncertain strains caused by boulders under the cutting edge. The internal flanges on the tubbing cannot be made very wide without interfering with the free passage of boring tools in the shaft, hence the strength of the lining depends on its thickness alone. This has reached 3 in., and at that thickness collapse has occurred in several THE MAMMOTH PUMP FIG. 43. Compound Drum and Mammoth Pump and Borer A, Suction Pipe and Overflow of Muddy Water; B, Compressed Air; C, Masonry Caisson; D, Shoe, Acting on Anchoring Ring; E, Anchor Rods. 90 PRACTICAL SHAFT SINKING cases. Further increase is not practicable on account of the weight of the segments and the difficulty of handling them. The cost would also be excessive. The compound sinking drum (patented in Germany by Mr. Pattberg) is a decided improvement. In this, occa- sional rings of tubbing are provided with broad internal flanges, and the space between these is filled with concrete or brick, leaving the interior of the shaft perfectly smooth. The masonry not only strengthens the tubbing, but also adds weight where it will do the most good, and expedites sinking. The friction and adhesion between the ground and the drum have been lessened by hydraulic flushing. For this, the shoe and three or four rings of tubbing immediately above it are made slightly larger than the rest of the lining. In the upper side of the shoulder thus formed, water passages are provided which are connected to a pressure pump. While sinking, the pump is operated and the drum is par- tially surrounded by a film of water. This expedient has been very successful. (See Fig. 42.) The sinking drum is sealed to the solid measures by forc- ing the cutting edge into them by the full power of the jacks. If necessary the shaft can be bored into the rock by the Kind-Chaudron method, as will be explained later. The entire process will probably be made clearer by a short description of an actual piece of work. Shaft 5, of the Rheinpreussen Colliery, Homburg-am- Rhein, Germany, was expected to penetrate nearly 500 ft. of quicksand and mud. Sinking was started with a brick caisson C, Fig. 43, 29.2 ft. inside diameter, with walls about 3.5 ft. thick. This reached a depth of 65 ft. Nine feet of concrete was placed on the bottom under water and the shaft pumped out. The anchor ring D, anchor rods E, and pres- sure ring, designed for a maximum pressure of 3000 tons, were erected and a brick inner lining built around the rods, reducing the diameter of the shaft to 25.68 ft. A compound drum F, with an outside diameterof 25.52 THE FREEZING PROCESS 91 ft., and a diameter inside the broad flanges and the brick lining of 21.32 ft., was now built and sinking was started with a percussion borer and mammoth pump. The concrete was bored through in four days, and an average advance of about 5 ft. a day was made in the soft ground. The progress was, in fact, limited by the rate at which tubbing and walling could be built up under the heads of the jacks. It was possible to force the compound drum to a depth of 245 ft. The shaft was then filled for 60 ft. with sand and gravel instead of concrete, was pumped out, and an inner iron drum, 3^ in. thick and 19.35 ft. in inside diameter, was built up to the jacks. This drum stuck at a depth of 315 ft., 60 ft. of gravel was again filled into the shaft, and a third drum, 17.38 ft. in inside diameter, was built up to the jacks. This was forced to a depth of 343 ft., where the cutting edge stuck in clay solid enough to permit the shaft to be pumped out. A fourth drum, 15.3 ft. in inside diameter, was then built, which reached the solid coal measures at a depth of 508 ft. Shaft 4 was sunk simultaneously, with exactly similar drums. The third drum reached a depth of 433 ft. before the shaft could be pumped out. The completion of both shafts to the rock took three years. The Freezing Process. The great depth to which frost penetrates the ground in Siberia and other cold countries enables shafts to be sunk through soft ground to consider- able depths during the winter months. Continued freezing gives the sides all the support that is necessary until rock is reached and a permanent lining built up. It occurred to F. H. Poetsch in 1883 that this condi- tion could be imitated artificially. His method is to bore a number of holes around and somewhat outside of the periphery of the proposed shaft, and to case them through the soft strata to the rock. A freezing plant is erected at the shaft head, and the brine or freezing solution is circulated down interior pipes and up through the bore-hole casings until the surrounding ground is frozen to a solid mass. The 92 PRACTICAL SHAFT SINKING holes are bored 'about 3 ft. apart; the form of the frozen ground is consequently cylindrical. At first the cylinder is hollow, but as the freezing continues, it gradually becomes solid ice. Excavation is then commenced, the frozen ma- terial being loosened with picks or light charges of explo- sives. In Europe 70 or 80 shafts have been sunk by the freezing process, the thickness of the soft ground in some cases reaching 300 ft. Most of these shafts are in France, Bel- gium, or Germany; a few have been frozen in England by continental contractors. In the United States the process has so far found a very limited application. One shaft in Michigan was frozen through about 100 ft. of quicksand, and an unsuccessful attempt was made to freeze a shaft in Pennsylvania. A number of European shafts started by the freezing method have been completely lost through some accident. Notwithstanding this, the method is being improved and greater and greater depths are attempted and reached. Water-bearing rock strata are successfully frozen. A shaft in Belgium has been sunk by freezing through 700 ft. of soft ground and wet rock. A detailed description of the freezing process, written by Mr. Sidney F. Walker, may be found in the August, 1909 issue of Mines and Minerals. The chief difficulties met with in freezing, especially in deep freezing, are deviation of the bore holes, salts in solu- tion in the ground water, bursting freezing pipes, and the tendency of ice to flow under pressure. The first trouble can be met by measuring the drift of the holes, and by boring additional holes when the divergence of those already bored is too great. Salt solutions are of course very hard to freeze, and their presence in the ground necessitates a much longer freezing period than would otherwise be necessary. A burst pipe allows the freezing solution itself to flow into the ground, forming a soft spot that it is almost impossible to freeze at all. The obvious way to prevent this is to use very strong THE FREEZING PROCESS 93 tested pipe, and it is now found advisable net to circulate the freezing solution through the bore hole casing itself, but to insert an inner and outer freezing tube and to withdraw the casing. The flowage of ice cannot be prevented and limits the depth for which the freezing process is feasible. Hard freezing checks this tendency. A freezing period long enough to thoroughly solidify the ground is the first essential for successful sinking. The smallest crack or seam which will admit a few drops of water will soon enlarge itself until a disastrous break-through occurs. It is also necessary, from time to time as the shaft is excavated, to support the sides with some form of sus- pended lining. The Anhalt Government Salt Mine, at Leopolds-Hall, Stassfurt, is an example of a successful application of the freezing process. Drilling was commenced early in 1899 and 26 holes about 5 in. in outside diameter were drilled on a 26.25 ft. circle and cased to a depth of 325 ft. The drilling was difficult, and was not completed until June, 1900. By this time the freezing plant (which consists at most shafts of two 75 horse-power ammonia compressors) was ready and it was started June 22. Sinking was commenced on September 2, and on September 19, at a depth of 30 ft., a small leak which existed in the middle of the bottom broke through and flooded the shaft. Freezing was then continued until the end of November, and sinking was again started. By the end of February, 1901, 202 ft. had been sunk, and the shaft was then lined with iron tubbing. The space between the tubbing and the rock was filled with concrete mixed with a solution of calcined soda. Periods of sinking and lining then alternated, until on July 4, the shaft was lined complete to the bottom of the frozen wall. The total time required for a depth of 325 ft. was therefore two and one-half years, an average progress of 11 ft. per month. The Chapin Mine Co., Iron Mountain, Mich., decided to sink a shaft in the center of a small valley crossing its prop- erty. Attempts to sink by ordinary methods having failed, 94 PRACTICAL SHAFT SINKING in 1887 a contract was let to the Poetsch-Sooy smith Freezing Co. to sink the shaft by the freezing process. At the site of the shaft the rock was covered by 95 ft. of quicksand, gravel, and boulders. The sand had some clay mixed with it, contained 1 per cent, of water, and would flow almost like water. The installation of the freezing pipes was performed by the Chapin Mine Co. itself, and was finished in the summer of 1888. Twenty-six 10-in. bore holes, spaced evenly on 29-ft. circle, were driven and cased to rock, great difficulty being experienced in keeping them vertical on account of the boulders. Eight-inch freezing pipes f in. thick, flush inside and out and closed at the bottom, were lowered into the holes and the casings were then withdrawn. Inner tubes 1 in. in diameter were lowered into the freezing tubes, their lower ends being kept 8 in. above the bottom. The upper ends of the tubes were connected, as shown in Fig. 44, to the brine pipes of a 50-ton-per-day capacity Linde freezing plant operated by a 55 horse-power engine, driven by compressed air. Two hundred cubic feet of brine consisting of a 25 per cent, solution of calcium chloride was used for the freezing fluid, the entire quantity making a circuit every thirty-three minutes. Excavation and timbering were started fifteen days after freezing was begun and were continued for seventy-eight days, when rock was reached in one end of the shaft. During this period two and a half days were lost by the interrup- tion of the air supply to the engine. Some water had been finding its way up through the unfrozen core in the middle of the shaft; the quantity now increased and sand began to come in with it. The shaft was at once filled with water and an additional freezing pipe put down. Four months and a half after freezing was begun the shaft was sunk 7 or 8 ft. into the rock. At this point enough water found its way through the fissures in the rock to thaw out the sand at the rock surface, and it was necessary to again flood the shaft. Before this was done, however, a coil of pipe was THE FREEZING PROCESS 95 suspended at the rock surface and connected to the freezing machine. This successfully stopped the leak, but six weeks more were lost. The shaft was sealed to rock, and the ice machine shut down on June 6, 1889, after running just two hundred days. ' The shaft was sunk rectangular 15 ft. 6 in. X 16 ft. 6 in. FIG. 44. Connections of Top of Freezing Tube, Chapin Shaft in plan, and was lined with 16 X 16 in. timber sets spaced about 4-ft. centers on top, and skin to skin at the bottom. The frozen sand was blasted out with lime, black powder, and finally dynamite. In 1889 the Mt. Lookout Coal Co. started to sink two shafts near Wyoming, Pa. The test holes showed 32 ft. of dry gravel and 70 ft. of quicksand over the rock. While the first shaft was being sunk by the pneumatic process, an 96 PRACTICAL SHAFT SINKING attempt was made to sink the second by the freezing process. Bore holes were put down from 5 to 7 ft. apart in a circle around the proposed shaft, and cased through the surface and 5 ft. into the rock. A freezing mixture was then cir- culated in the pipe for seven weeks,' at which time the caisson of the first shaft reached rock. It was then dis- covered that the rock, instead of being solid as supposed, was fissured for 18 ft. below the surface. As a large inflow of water occurred in the fissures, the company decided that it would be impossible to successfully seal off the water in the second shaft with the freezing tubes only 5 ft. in the rock, and the attempt was abandoned. The shaft was then sunk by the pneumatic process, and although some time had elapsed between the abandonment of the freezing and the sinking of the caisson, the ground was found to be still frozen hard. The writer wishes to acknowledge his indebtedness to Mr. J. Riemer, from whose book, " Shaft Sinking in Difficult Cases,"* he got many facts about the sinking drum and freezing processes in general, and a description of the European applications. The descriptions of the American freezings were abstracted from the Transactions American Society Civil Engineers for June, 1904. * " Shaft Sinking in Difficult Cases," by J. Riemer, translated from the German by J. W. Brough. J. B. Lippincott & Co., Philadelphia, 1907. CHAPTER VII THE KIND-CHAUDRON BORING PROCESS. CEMENTATION OF WATER-BEARING FISSURES SINKING in wet rock may be accomplished in two ways: mechanically, by breaking and removing the rock under water; by hand, by closing the seams in the rock, thus pre- venting the inflow of water, or by lifting the water as fast as it flows in. The first plan can be carried out in one way only the boring process. The second is accomplished by the freezing process, already described, and by direct cementation of the fissures of the rock: water is most frequently lifted by sinking pumps suspended in the shaft, although the old Cornish "spear-rod" pump is still sometimes used for large quantities of water. A system of water hoisting has also been developed. The Boring Process. The Kind-Chaudron boring process has previously been referred to as a process devised for sinking through rock measures containing such quanti- ties of water that hand sinking is impossible. It is exclu- sively a European method, and so far no shafts have been bored in this country. The process was originated by M. Kind, a well borer, in 1849. Between that date and 1854 he attempted to sink three shafts in Moselle and in West- phalia, but failed owing to the inadequacy of wooden tubbing. The scheme was then taken up by M. J. Chaudron, a Belgian engineer in France, and was improved by him to such an extent that his name is now always associated with that of Kind. Subsequent improvements of value have been made by Riemer and others, and have been patented in Europe; at present the firm of Haniel & 97 98 PRACTICAL SHAFT SINKING Lueg, of Dusseldorf, controls many of these patents and is best equipped for boring shafts. Kind's original plan was to bore the shaft in one opera- tion. The difficulty of collecting the broken rock made it advisable to bore in two stages, and a small hole, having a diameter one-third to one-half that of the finished shaft, is now bored in advance. The muck in this is removed by a special bucket with flap valves in the bottom, so arranged that as the bucket is lowered the muck will enter. When the bucket is raised the valves close. The small shaft serves as a guide for the large boring tool, as well as for a collector for muck, and it is usually bored about 100 ft. ahead of the large boring. The cutting edges of the large borer slope down toward the center; the borings, therefore, slide into the small shaft. The large tool thus has always a clean surface to work on. Boring is usually adopted as a last resort. In regions where large flows of underground water are expected, the shaft is sunk by hand until the water-bearing strata are reached and is then cleared for boring. Care must be taken to keep the shaft free from timbers, permanently fastened pumps, and pipes, etc., so that when it is flooded all impedi- ments to boring can be hoisted out. If this is not done, it will be necessary to cover the bottom of the shaft with a thick layer of concrete, deposited under water with a grab bucket, in order to permit the shaft to be pumped out and cleared. When boring is started, it is carried through the water- bearing strata and some distance into the impervious ground beneath. The shaft is then lined with rings of cast- iron tubbing; the placing of this tubbing is the most ingenious feature of the boring process. (See Fig. 45.) After the shaft has been cleaned out and the boring tools removed, a heavy platform is built over the shaft and upon it the "moss box" is erected. This consists of two rings of heavy tubbing, forming a large stuffing-box which is filled with moss, and is so designed that an upward pres- THE KIND-CHAUDRON BORING PROCESS 99 sure on the lower ring will force the moss out against the sides of the shaft. The moss is covered with wire netting to keep it in place, and the diameter of the whole is slightly less than that of the shaft. On top of the moss box is bolted a ring, fitted with a heavy arched bulkhead that closes the FIG. 45. Tubbing and Moss Box shaft. The whole structure is then lifted by heavy jack- screws and, after the platform is removed, is lowered into the shaft. It is then hung from beams placed across the shaft, the jackscrews are disconnected and withdrawn, another ring of tubbing placed on the beams, and the jackscrews reconnected. The beams are taken out and the 100 PRACTICAL SHAFT SINKING ring is lowered into place and bolted up. The process is then repeated. Since each ring of tubbing weighs less than the water it displaces, after enough have been added the whole column of tubbing will float. The hanging rods are then dispensed with and, as each ring is bolted on, the tubbing is sunk by admitting water. This is continued until the moss box reaches the bottom of the shaft. The whole column is then allowed to fill with water, and, all buoyancy being re- moved, the entire weight of the tubbing serves to crush the moss outward against the sides of the shaft. A water-tight joint is thus made at the bottom. The space between the tubbing and the sides of the shaft is then filled with concrete, and, after this has set long enough to thoroughly harden, the shaft is pumped out and the bulkhead removed. The concrete is usually placed with small flat buckets lowered with ropes. The boring tools, borers or " trepans," Fig. 46, are made of cast steel provided with inserted teeth, and weigh about 10 tons for the small and 20 tons for the large tool. They are suspended by heavy timber rods from a walking beam operated by a single large, vertical steam cylinder. Between the walking beam and the rods a chain connection is pro- vided, by means of which the borers can be lowered as the hole deepens. At the "bore master's" platform on top of the shaft there is a swivel connection and a long lever for rotating the borer slightly between blows. The head-house is a tall structure with two wings in which are stored the various tools. All are hung from small trucks which can be readily run out over the shaft. Two hoist engines and cables are provided, one for the bucket and the other for the borers and tools. Considerable difficulty is encountered in boring through fissured ground and through strata of soft material. In the first case the teeth of the borers are liable to breakage; in the second, large masses of material fall out of the sides of the shaft, sometimes burying the borer. A special tool has CEMENTATION OF WATER-BEARING FISSURES 101 been devised for fishing out broken teeth, large pieces of rock, etc. A falling in of material is prevented by sheet- iron cylinders, lowered from the top and suspended by flat ropes. These cylinders have no hydrostatic pressure to resist, hence need not be heavy. They are built of f-in. plate, in lengths up to 60 ft. FIG. 46. Cross-section of Boring Tower It has not been found practicable to use segmental tubbing rings for lining bored shafts, owing to the difficulty of making the vertical joints water-tight. The maximum diameter at present, therefore, is limited by the size of the single ring which can be transported about 14 ft. diameter. The boring is made 18 in. to 3 ft. larger, depending upon the character of the ground. Ordinarily the small borer is about 8 ft. across, and the large one 15^ ft. for 14-ft. tub- bing, but if much bad ground is expected and the use of 102 PRACTICAL SHAFT SINKING several sheet-iron cylinders is contemplated, the large borer is made 16| ft. or 17 ft. across to start with. The speed made in boring shafts has varied so greatly that it is hard to give definite figures. Under favorable conditions the small tool will advance 20 in. per day, and the large one 7 or 8 in. If to the time required for actual boring is added that taken for lowering sheet-iron cylinders and tubbing, it will be seen that an average progress of 8 to 10 ft. per month is all that can be expected. The costs of the boring process are, in consequence, exceedingly high, but for the very difficult sinking conditions obtaining in some parts of Europe it is the only process that is unfailingly successful.* Direct Cementation. The injection of cement grout under pressure into fissured rock has been attempted only recently. Immediately around the proposed shaft a num- ber of holes are drilled through the fissured rock into the solid measures beneath, and grout is forced into them until all crevices are filled. It is then allowed to set, and, if the work has been properly done, sinking can be continued in the dry. The water-bearing fissures can best be located by using core drills rather than percussion drills in boring the holes. If only one crevice exists, the grout will flow directly- into it; if, however, the rock is fissured for some distance, while grout is flowing into the upper cracks, the hole beneath them may become blocked before the lower cracks are filled. In this case the water will not be completely shut off. Up to the present time the blocking of the fissures in any considerable depth of rock has only been accomplished by successive cementations. This was done in the two cases described below. The writer believes, however, that if the holes are bored entirely through the wet rock, a method can be devised for filling the cracks from the bottom up. A plan that might be worked out would be to case the holes *For detailed infomation on this process see: " Shaft Sinking in Difficult Cases," by J. Riemer. CEMENTATION OF WATER-BEARING FISSURES 103 with flush-joint pipes to the bottom, then to gradually withdraw the pipes as the grout is pumped in. The grout- ing apparatus would have to be so arranged as to permit quick disconnection and reconnection upon the removal of each length of pipe, to avoid the possibility of the grout setting in the pipe while the flow is interrupted. The following account of the cementation of a shaft sunk by the Mining Society of Lens is an abstract from an account published by C. Dinoire in Volume XXXI of the Transactions of the Institute of Mining Engineers (English) : The Mining Society of Lens decided in October, 1904, to sink two shafts, one by the freezing method and one by hand. The water encountered in the second exceeded the expectations to such an extent that it could not be pumped and the feeders had to be stopped by direct cementation. This shaft was sunk to a depth of 166 ft. before an inflow of 2200 gallons per minute made cementation necessary. The pumps were worked very hard to hold the water down as low as possible, and two lines of 2-in. pipe, extending from the surface to the bottom of the shaft, were installed. As some of the water came in through a nearly vertical fissure in the shaft bottom, and some through a horizontal seam, one of the pipes was driven into the fissures for 9 ft. and the other was terminated opposite to the seam, Fig. 46. Four 8-in. bore holes, 197 ft. deep, were then put down out- side the shaft area. They were spaced evenly 13 ft. from the circumference of the shaft. At a depth of 190 ft. they passed through a bed of very seamy rock. A hand pump was put on each of these holes in order to pump out all sand and mud caused by boring. Three hundred and sixty sacks of cement mixed as a thin grout were then run into the pipe which terminated opposite the horizontal seam. This took seven hours; the grout mixer was then connected to the other pipe to give the grout in the bottom of the shaft a chance to set. Two hundred and ninety sacks were run into this pipe in three hours, when the lower end became blocked. Ninety sacks 104 PRACTICAL SHAFT SINKING were then run into the first pipe, completely filling it, after which the bore holes were filled. This required 475 sacks. The pumps on the bore holes were worked continuously while the pipes were being grouted. The grout was allowed to set for nineteen days before the water was pumped out of the shaft. It was then found that the leak was completely closed and a 2|-ft. layer of FIG. 47. Location of Pipes and Fissures in Lens Shaft grout had formed on the bottom. The rest of the grout, amounting to 282 cu. ft., had run into the fissures. The bed of grout was sunk through very carefully, and the shaft deepened to 170 ft. and lined to the bottom. At 185 ft. a second inflow was encountered, the water breaking in through the vertical fissure referred to above. Two more grout pipes were inserted, their lower ends being driven 3 and 6 ft. into the fissure. Nine hundred sacks of cement CEMENTATION OF WATER-BEARING FISSURES 105 were run into the longer pipe in nine hours, when the lower ends of both pipes became closed. After twenty-eight days the water was pumped out and sinking was resumed. The large fissure was found to be this time thoroughly cemented, and further sinking and lining was carried on without particular difficulty. It was found in the first cementation, where the mixer discharged directly into 2-in. pipes, that considerable air was carried down with the grout. This hindered the flow very greatly, so that in the second cementation the grout pipes were made lj in. diameter above water and 2f in. under water, a high narrow tank was connected with the top of the grout pipe, and a valve was provided to regulate the flow from the tank, which was kept full. The mixer discharged into the tank through a trough, with gratings for removing air. The more important conclusions reached were: 1. Fissures in rock can be cemented through pipes or bore holes. 2. Sand, marl, boulders, clay, and slime cannot be cemented. 3. Thin beds presenting continuous openings can be cemented by pumping from bore holes outside the shaft. Direct cementation has also been applied at the Anzin and the Bethune collieries in Europe. Direct cementation has only been attempted in America in one instance. No. 4 shaft on the Rondout siphon of the Catskill Aqueduct encountered a flow of water of 750 gallons per minute at a depth of 270 ft. The shaft is rect- angular with three compartments, measures only 8 ft. 4 in. X 20 ft. 4 in. in the clear, and thus affords very little oppor- tunity for handling large pumps. In addition to this fact the water was strongly charged with sulphureted hydrogen gas, which acted very painfully upon the eyes of the sinkers. After no progress had been made for several weeks, it was decided to try grouting. Most of the water came directly out of the bottom. The water level was held within 106 PRACTICAL SHAFT SINKING about 5 ft. of the bottom and a number of holes from 10 to 18 ft. deep were drilled with rock drills. Two-inch pipes were connected to these holes, and about 1500 sacks of cement, mixed as neat grout, were forced into them. This reduced the flow of water in the bottom from 525 to about 50 gallons per minute. In order to block the fissures below the shaft bottom, a diamond drill was set up on a platform at the top of the shaft, and six holes were drilled, each about 95 ft. deep. A column of 3-in. pipe extending from the top to the bottom of the shaft served in each case as a guide for the drill rod. These holes passed entirely through the water-bearing rock, which consisted of a badly fissured sandstone, and penetrated an impervious stratum of grit beneath. Two-inch grout pipes were now connected to these diamond-drill holes and 183 sacks of cement were forced into them. This entirely cut off the water in the bottom. It was found upon pumping out the water that all the upper fissures were completely filled. When sinking was resumed, however, it was further found that the drill holes had become blocked before the lower fissures were completely filled, and the water, therefore, was not altogether shut off. After the cementation it was, nevertheless, possible to handle the water with pumps and sink about 10 ft. a week in the ordinary way. In filling all the holes the grout pipes were carried to the top of the shaft. The grout was mixed and fed into a tank attached to the top of each pipe. When no more grout would flow by gravity, the opening in the tank was closed, and air pressure applied on top of the liquid grout. The pressure ranged from 80 Ibs. to a maximum of 300 Ibs. per square inch, which last was obtained by means of a special air compressor. NOTE. For further information about methods of grouting see Ap- pendix A. CHAPTER VIII LIFTING WATER. HORIZONTAL vs. VERTICAL PUMPS. HANDLING PUMPS IN SHAFT. CORNISH PUMPS MODERATE quantities of water are ordinarily raised from the bottom of a sinking shaft by one or more pumps, suspended or supported in the shaft just above the bottom, and lowered from time to time as the shaft is deepened. The usual motive power is steam or compressed air; electric pumps are being developed, but so far have not been suc- cessful. The work that a sinking pump is called upon to do is exceedingly arduous. It must first of all be reliable; it must run on gritty water or a mixture of water and air, or sometimes on air alone for a while without injury. The valves, packing, and wearing parts must be readily acces- sible. It must occupy a minimum space in the shaft, and at the same time be strong and heavy enough to endure collisions with the sides in hoisting and lowering, and blows from flying fragments of rock. Any one in this country who has tried to sink a wet shaft is more or less familiar with the features of the leading American sinking pumps. Of these the Cameron is the best known, and the Cameron pattern, Fig. 48, now manufac- tured by a number of firms, certainly comes nearest to filling the requirements. This is built in both vertical and hori- zontal piston and outside-packed plunger styles, and is marked by the absence of outside valve gear, by the thick- ness and strength of the castings, and by the accessibility of the water valves and packing. The manufacturers as a rule recommend the vertical pump for sinking, but the writer's experience has taught 107 108 PRACTICAL SHAFT SINKING him otherwise. When there is only a slight inflow of water, a small vertical pump with hose connections is certainly very easy to hang in the shaft; on the other hand, a hori- zontal pump, with a capacity of 150 gallons per minute FIG. 48. Vertical Sinking Pump or less, will work perfectly when hung with a bridle. Where there is a considerable flow of water, and where the shaft is large enough to accommodate a horizontal pump or pumps of the required capacity, this is the type to use. Where the LIFTING WATER 109 shaft is so small that there is not room in it for enough horizontal pumps to take care of the water, a vertical pump is of course a necessity. The writer's reasons for preferring the horizontal pump are: 1. The horizontal pump is lighter than a vertical of the same capacity. 2. In the larger sizes the horizontal pump is much more accessible, since a man can walk around it and work at any part of it on a level platform. It is necessary to climb 6 or 8 ft. to get from the water end to the steam end of a big vertical pump. 3. By providing a proper bridle, the horizontal pump can be hooked on to and lifted as easily as the vertical. 4. For a pump discharging over 300 gallons per minute, the recoil at every stroke is so severe that hose or other flexible connections will not stand when the pump is hung freely. This applies to the American style of vertical sinking pump, where the center line of neither suction nor discharge coincides with the center of suspension, as well as to a hori- zontal pump. In both cases it is necessary to furnish rigid support, and it is as easy to set two hitch timbers in a hori- zontal plane for a horizontal pump as it is to set them in a vertical plane for a vertical pump. In sinking several shafts in which the flow of water in the bottom varied from 800 to 1500 gallons per minute, the writer has obtained the best results by working along the following lines: Provide an absolutely reliable boiler plant of ample capacity. Sinking pumps are frightfully uneconomical, requiring from 200 to 250 Ibs. of steam per actual horse- power hour; a shaft in which 1000 gallons per minute must , ,. f . , onn ,. . AU . . 1000 X 84 X 300 ft. be lifted 300 ft. will, therefore, require 33,000 200 X = 505 horse-power of boilers for pumping alone. OvJ Put in a water ring, Fig. 49, and a stationary pump 110 PRACTICAL SHAFT SINKING wherever it is possible to reduce the water in the bottom by so doing. When the water-bearing stratum has been sunk through, open up a "lodgment" or reservoir in one end of the shaft and install a compound pump. For handling water in the bottom provide at least 50 per cent, extra pumping capacity; say, four 350-gallon FIG. 49. Section of Water Ring for Timbered Shaft pumps for 900 gallons per minute, two in each end of the shaft. Set bearing timbers, Fig. 50, as close to the bottom as is safe, and lower pumps alternately 10 ft. at a time, keeping 10-ft. and 20-ft. flanged lengths of steam, exhaust, and water pipes ready to put on. If each new set of timbers is placed 10 ft. from the bottom of the shaft, the maximum suction lift at any time will thus be 20 ft. Make swinging joints on all pipe lines at the pumps, to take care of vibra- tion and expansion and of variations in the spacing of the LIFTING WATER 111 hitch timbers. Do not attempt to lift pumps when blasting; remove suction hose only and shoot carefully. Provide an independent column pipe for each pump, and keep the pipes in the hoistway. Main steam and exhaust lines should be kept in one end of the shaft for the greater part of their length in order to create an upward current of FIG. 50. Arrangement of Pumps for Sinking air in that end and assist ventilation. Handle pumps with independent engine, arranged to hoist from any compart- ment. Clamp pipes to timber every three lengths. Too much care cannot be taken to obtain tight joints in all pipes, to fasten them securely to the timbers, to keep the pumps in good repair and plenty of spare parts (valves, 112 PRACTICAL SHAFT SINKING stems, packing, etc.) on hand, and to keep the follower bolts and nuts tight. It is advisable to fasten these securely with cotter pins, or by drilling through the heads and wiring them together. Pumps will run satisfactorily on compressed air if the air is reheated sufficiently to prevent freezing. As a rule, the cost of the air plant makes it imperative to use steam on the pumps. Both steam pipes and exhaust pipes should be lagged with some water-proof covering. At best, many delays will occur when water is handled. For a shaft making 800 to 900 gallons per minute, 15 to 20 ft. per month is good progress; the labor cost may easily reach $150 to -1200 per foot. Sinking with insufficient machinery is impossible. In this country water is usually regarded as an unfor- tunate accident, and when encountered is met by begrudged additions to the plant. As a result much time and money are wasted. In Europe, on the other hand, the mining dis- tricts have been more fully explored and developed, and the position of water-bearing strata is known. Preparations are made in advance for handling large quantities of water. The shafts are circular and are lined in sections as the sink- ing proceeds with brick or water-tight iron tubbing; their large diameter and freedom from cross-braces make it pos- sible to use more powerful pumps. An actual measured flow of from 2000 to 2500 gallons per minute in the shaft bottom is as much as has been successfully taken care of in America. In the two English cases cited below two to three times this much water was pumped. In the Transactions of the Federated Institute of Mining Engineers, Volume III, page 513, Mr. W. H. Chambers describes the sinking of two shafts at Conisboro, Yorkshire. Eight 30 ft. X 7 ft. 6 in. Lancashire boilers were installed, and sinking was then commenced in both shafts simultaneously. The water was handled by pulsometers to a depth of 156 ft., when an inflow of water occurred that made it necessary to put in very much more powerful pumps. LIFTING WATER 113 The sinking pumps, Fig. 51, were made by Baily & Co., of Salford, and were designed to run suspended in the shaft without other support than two suspension ropes which also carried all pipe lines. A telescopic suction pipe is provided instead of suction hose, and the axes of both suction and dis- charge pipes coincide with the axis of suspension. All vibrations caused by the strokes of the pump are, therefore, vertical and cause no dangerous sideways motion in the pipe lines. The pump itself " consists of three hollow plungers; the upper pair are stationary and over them slide barrels which are connected to the steam piston. The third barrel is secured, together with the pair of stationary plungers, to the steam cylinder by means of connecting rods." The pump is thus what is here known as the differential plun- ger type. Two discharge pipes are led from the top of the upper stationary plungers alongside the steam cylinder, and are joined above it by a tee from which the column pipe rises. The two suspension ropes are led over pulleys at the shafthead to the drum of a hoisting (or capstan) engine, and the pump and all piping are hoisted and lowered together. A telescopic joint is put on the steam pipe at the shaft head, the discharge pipe is turned sideways over a trough, and the exhaust pipe stands straight up. The arrangement of pump and pipes in the shaft is shown in Fig. 52 and the method of supporting the pipes is shown in horizontal section in Fig. 52a. Six pumps of this type, each with a capacity of 50,000 to 70,000 Imperial gallons per hour at 35 strokes per minute, were needed to sink the shafts to a depth of 300 ft. In this depth the maximum quantity of water discharged from both shafts amounted to 6600 gallons per minute, although the tubbing was carried along with the sinking. Two more- pumps were then obtained, and the eight were arranged to lift the water in two stages, as 300 ft. was the maximum lift of each pump. The water was finally shut off at a depth of 395 ft. in one shaft and 369 ft. in the other. LIFTING WATER 115 Mr. Chambers describes the operation of the pumps as follows : "As the sinking progressed, after the suction pipe was FIG. 52 FIG. 52a drawn out to its full extent, the pump with the columns of pipe was lowered by running the ropes off the capstan, and exhaust and water pipes were built as required on top; the 116 PRACTICAL SHAFT SINKING steam pipe, after being drawn its full length out of the stuffing-box, was pushed back and another length inserted. "A stop valve and a lubricator were placed in the fixed steam pipe on the surface. A lad was in charge to regulate the supply of steam .as required, he being in communication with the sinkers in the shaft by means of a signal bell. The speed of the pumps was thus controlled and lubrication effected without any one being in the shaft for these pur- poses." Perhaps the most remarkable achievement in the line of wet-shaft sinking that was ever accomplished was the sink- ing at the Horden colliery in Southeast Durhamshire. This work is described at length in a very interesting paper by Mr. J. J. Prest, the engineer in charge. The paper is published in the Proceedings of the Institution of Civil Engineers, Volume CLXXIII, Part 3. At this colliery three shafts were sunk, two of them simultaneously; the third was put down to the level at which the greatest flow of water occurred, and there stopped until the other two reached the coal measures. Mr. Prest, after careful consideration, determined to use the old-style Cornish pump and installed a very remarkable plant, comprising over 3000 boiler horse-power and no less than four sets of 30-in. bore by 6-ft. stroke pumps. Each set consisted of a pair of pump cylinders hung so as to balance each other, and capable of being arranged as a high-and a low-lift set. The pumps were driven by the permanent hoisting engines, provided with an extra jack-shaft and gearing. The maximum quantity of water handled simultaneously from all three shafts amounted to 9230 Imperial gallons per minute, and the maximum from one shaft to 6310 gallons per minute, this quantity being pumped from a depth of 300 ft. The shafts reached an average depth of about 540 ft. before the coal measures were reached and it was finally possible to tub back the water. A system has been developed in England for hoisting water from a sinking shaft without the use of any high- LIFTING WATER 117 pressure pumps. It is known as the Tomson water-winding process. Mr. Tomson puts in his permanent hoisting engine, places guides in the shaft as the sinking proceeds, and uses large tanks for lifting the water. The tanks are filled by low-pressure pumps driven by compressed air and attached to the tanks. This system has been very success- ful in some instances, but has not been used where the quan- tities of water were as great as those at Conisboro or Horden. CHAPTER IX SHAFT LININGS SHAFTS are usually lined; either in order to exclude water, or to support the sides and prevent the falling of fragments of rock. The most common lining material in fact until recently almost the only lining material used for American mine shafts is timber, ordinarily framed in square sets and lagged with plank. Such a lining cannot be made water- tight and acts only as a support or shield. Wooden caissons and coffers used in bad surface ground are of course built to exclude water, but this construction is not feasible at considerable depths. European shafts are usually lined with brick walls, built upon cast-iron curb rings set into the sides of the shaft at intervals. The circular and elliptical sections universal in Europe are in fact accounted for by the necessity for arch action in a brick lining. The walls are not designed to absolutely exclude water, but to lead it to water rings at the curbs and prevent it from dripping in the shaft. A brick lining is fire-proof and durable. Where it is desired to block back large feeders of water, cast-iron tubbing is used. This has already been referred to in connection with the Boring Process. Two styles of it are used in Europe, known respectively as English and Ger- man tubbing; the writer knows of no case where it has been used for a mining shaft in this country, but miles of suba- queous tunnel around New York City are lined with bolted cast-iron segments. In the last decade, concrete has come to the front as a material for lining shafts. It is gradually being realized 118 SHAFT LININGS 119 that, when properly handled, concrete can be made as water tight as iron; it is stronger than brick and as durable, and is cheaper than either iron or brick. The first shaft in America to be entirely lined with concrete was sunk by the U. S. Coal and Coke Co. at Tug River, West Virginia, in 1903. Since then this construction has been adopted for a dozen shafts or more/ Of the various kinds of shaft lining, timber is the easiest to place and in America is still the cheapest in first cost. This advantage, however, diminishes every year; good tim- ber is scarce and dear to-day, and ten or fifteen years hence the life of a timber lining will be scarcer and dearer. A timbered shaft in a mine whose life is expected to exceed the life of the original timber is thus a very doubtful investment. Considerations of safety present a stronger argument against the use of timber in coal mine shafts. A severe explosion in the mine will wreck the lining and fill .the shaft with twisted timber, thus cutting off all hope of escape or rescue from the men imprisoned below. This danger has long been avoided in Europe by the use of walled shafts, and before many years public sentiment in America will demand that it be avoided here. A Pennsylvania law now on the statute books prohibits the use of wood in permanent tipples or breakers within 200 ft. of the shaft head; why should not this law be logically extended to cover timber in the shafts itself? In ore shafts and construction shafts the same objection to timber does not apply, although the possibility of fire must be considered. This is not often a serious danger as the timbers are usually so wet that nothing short of an explosion could ignite them. A system of reinforced con- crete " timbers" which has been proposed and patented is intended to retain the advantages of a rectangular tim- bered shaft, and at the same time provide a fire-proof lining that is easily placed. It has never been used. Timbering. Buntons. In rock that is hard enough to stand without support and is not affected by frost and 120 PRACTICAL SHAFT SINKING moisture, the cheapest construction is an unlined rectan- gular shaft with several vertical rows of buntons to which the guides and ladders are fastened. These buntons cor- respond to the buntons and end plates of a square-framed set of timbers, and are set into pockets cut in the rock. - Compartment .8"*/o'/?i.ntj Umbers *5 fbr Guides ^ DetacL of corner Other Method:, of securing FIG. 53. Timber Sketches They must be set correctly in parallel vertical planes, and should be level and in line horizontally, but absolute accuracy in this respect is not essential. The pockets are known as "hitches," the "box hitch" is cut square; the "drop hitch" is cut with the top sloping back so that after one end of the bunton is placed in the box hitch the other SHAFT LININGS 121 may be dropped into place. The buntons are usually set on 5-ft. centers vertically, so that workmen standing on a platform on one row of timbers can cut the hitches for the next row without scaffolding. (See Fig. 54.) After the buntons are placed in the hitches they are secured and held in line by oak wedges driven in tight. The hitches are cut just enough larger than the timber to allow for wedging. The depth depends upon the rock; specifications usually call for 12 to 18-in. hitches, but, as a matter of fact, in any rock hard enough to stand without support a 4-in. hitch will break the timber. FIG. 54. Shaft Timbered with Buntons Only Hitches are usually cut by hand with hammer and bull point, but pneumatic hammers can be used to advantage in hard rock. When working by hand a pair of men (ham- mersman and holder) should finish a pair of hitches in an eight-hour shift. The labor cost per timber is thus about $5 net, or $7 including headmen, engineers, etc. Ring Timber. The commonest form of timber lining, and the one that is used in all large shafts, consists of hori- zontal square-framed sets, spaced 4 to 6 ft. centers and lagged with 2 to 3 in. plank. (See Fig. 53.) In a previous chapter, the terms bunton, end plate, wall plate, and punch block were defined as the cross struts, end timbers, side timbers, and posts, respectively, in a square- framed set of timber. Each set consists of two wall plates 122 PRACTICAL SHAFT SINKING and two end plates halved at the corners, and one or more buntons, butted against the inner faces of the wall plates to serve as struts. The buntons also divide the shafts into the requisite number of compartments and afford support for guides, etc. The sets are separated by posts or punch blocks placed at the corners and at the end of the buntons. Lagging plank are set vertical and close together. They are usually placed back of the timber, and are held by cord wood or slabs packed into the space between them and the rock. This packing also acts as a support for the sides of the excavation. To prevent plank from falling in case of displacement of the packing, they should be well spiked to the timbers top and bottom. The best construction is effected by spiking 2 X 2 in. strips horizontally in the middle of the outer faces of the wall and the end plates; the lagging boards are then cut two inches short of the center to center spacing of the sets, and are inserted between the strips. In hard rock packing is not necessary, but lagging is usually needed to prevent water from splashing into the shaft and to lead it to the rings. In this case, the lagging boards are placed between the timber sets and are held by strips nailed to the top and bottom faces of the timbers. Sometimes these strips are beveled so as to lead water to the back side. When a shaft has been sunk without support as far as the condition of the sides will permit say 50 to 100 ft. a set of hitch timbers (dead logs or bearing timbers) is placed as a foundation, and the timbering is built up through the unlined section. The hitch timbers are set into hitches cut in the rock as described above, and must be perfectly level and in line. Since they are to carry a great weight the hitches must be deep enough to afford a bearing equal in strength to the timber. The hitch timbers are often made deeper than the ring timbers; 8 X 12 in. hitch timbers, for instance, for 8 X 10 in. ring timbers. A heavy floor is built over the hitch timbers between the first set of timber and the wall, to carry the packing. (See Fig. 58.) SHAFT LININGS 123 Each set of timbers must be securely blocked and wedged in the corners and opposite the edge of the buntons. The lagging and packing are then finished before the timbers for the next set are lowered. The workmen stand on planks laid across the buntons and raised as each set is completed. In order to avoid splicing, the wall plates for the two or three closing sets (joining to completed timbering above) must be lowered into the shaft, laid upon the timbers already placed, and then raised horizontally. FIG. 55. Brick Shaft Lining Corner joints should be framed so as to develop the full strength of the timbers. Punch blocks and buntons are usually notched into the wall plates, being thus secured laterally; the punch blocks are allowed to extend out under the ends of the buntons to provide vertical support. In addition, keystoned shape notches are often cut in the wall plates, into which the ends of the buntons are fitted. The cost of placing ring timbers of this type varies from $20 to $30 per M. ft. B.M. In small shafts, the lagging plank are often placed hori- zontally and spiked together, and are notched into each other at the corners. This gives all the support that is required in a small square shaft or well; in a compartment 124 PRACTICAL SHAFT SINKING shaft, pairs of vertical timbers serving both as posts and girders are placed against the side, and buntons are set between them. Vertical nailing strips are also put in the corners. (See Fig. 58a.) Brick. The thickness of a brick lining varies from 9 to 18 in., depending on the size of the shaft and the nature of the rock. A 13-in. wall is the usual thickness for a 16-ft. shaft. The wall is built in sections 50 to 100 ft. long, each of which is founded on a curb of wood or iron built in seg- ments and set into a groove in the side of the shaft. This groove is cut by hand, the bottom being made perfectly level, and the curb is carefully wedged into shape exactly concentric with the shaft. If much water leaks into the shaft in the section that is to be lined, the curb is made of iron and the space behind it is filled with wooden blocks and wedges driven in tight, as will be described in detail later. A water ring is cast on the inside of the curb, and drainage pipes leading through the lining to the ring are provided. (See Fig. 55.) The work of setting the curb and building the wall is done on a suspended scaffold which is raised as required by a special engine at the surface. The wall is built very rapidly as several masons can work without interference six masons, if kept supplied with brick and mortar, can easily build 6 to 8 ft. of wall per shift. In deep shafts recently sunk in England, the work has been so arranged that sinking and lining are carried on simultaneously. Two buckets are used, one of which hangs in the center of the shaft, and passes through a hole in the walling scaffold. The other hangs sufficiently off center to clear the sinking bucket, and is used for supplying ma- terial to the masons. The ropes which suspend the scaffold also serve as guides for the buckets. This method is only feasible for large shafts. The brick should be made of good clay, burned hard enough to withstand the action of water. Mortar is made of quick-setting Portland or hydraulic cement and is used SHAFT LINING 125 as sparingly as possible. The space back of the wall is filled with concrete, tamped clay, or cinders. Iron Tubbing. Both English and German tubbing consists of cast-iron segments and is built up in rings. The Wedge i - 3 j jT}H I u u u FIG. 56. English Tubbing Segment 15 to Circumference English segments, however, have rough edges and no bolts and are made water-tight by wedging the cracks with wood, whereas the German have machined edges provided with flanges and are bolted together. Lead gaskets are used to make a tight joint. English segments are about 2 ft. and German about 5 ft. high. -Bolt Hole FIG. 57. German Tubbing Segment 8 to Circumference The process of setting a wedging curb and building up English tubbing in wet rock is described by Mr. J. J. Prest as follows: 126 PRACTICAL SHAFT SINKING "The shaft was sunk about 9 or 10 ft. into the imperme- able stratum, of the full diameter of, say, 23 ft., and then decreased abruptly to the finished size of the shaft, say 20 ft., and the sinking was continued a further distance of 6 or 8 ft. The cradle (walling scaffold) was then lowered FIG. 58a. Timber Sketches into the pit bottom and a temporary wood water-ring was fixed on dowels about 9 or 10 ft. above the site selected for the bed of the wedging curb. The whole of the water running from the sides of the shaft was then collected in this temporary water-ring and allowed to run off in canvas hogges or trunks at two or three different positions to the pumps. SHAFT LINING 127 "The cradle having been fixed in position, the sinkers proceeded to level the surface of the rock bed with mat- tocks, and when this was accomplished to the satisfaction of the engineer, a wedging curb, three segments of which were fitted with valves to pass gas or air accumulated behind the tubbing, was laid on the bare rock, seasoned red-wood sheeting f in. thick was placed between all end joints, and the spaces between the back of the curb and the rock were filled with dry-wood gluts to bring the inside of the curb up to the finished diameter of the shaft. Afterwards well- seasoned tapered dry-wood wedges were driven into the wood packing between the back of the curb and the strata until steel chisel points refused to enter. Then a layer of f-in. horizontal sheeting was placed on the top of the wedg- ing curb, and the 2-ft. foundation course of tubbing was put on, breaking joints with the curb, f-in. red- wood sheeting being placed between the end and horizontal joints, and the course was brought up to the correct radius of the shaft by means of wood packing. Next one or two courses of plain tubbing were put on, the fourth course usually containing three or more special segments (technically termed 'valve- segments'), cast with holes 4 to 6 in. in diameter in the center, with the object of permitting the water to pass from the back to the front side of the tubbing, and so to the pumps, when the temporary wood water-ring was removed. "The next operation was to wedge lightly the vertical joints of the three or four courses of tubbing, and to run the whole up solid with good cement grout. The temporary water-ring was then removed, and additional courses of ordinary tubbing were built on, to a total height of about 60 ft. The joints were now lightly wedged, commencing from the top with the vertical joints, and from the bottom with the horizontal seams, using red-wood wedges. Addi- tional courses of segments of suitable height being used to close up to the wedging curb above, the vertical and horizontal seams were again twice wedged alternately as before, and the small center holes in each segment were 128 PRACTICAL SHAFT SINKING plugged. Finally the large holes in the valve segments passing the feeders were plugged simultaneously with long tapered plugs of wood, the excess being sawn off flush with the front side of the orifice, the cast-iron caps were bolted on to the flanges and the shafts was rendered dry if the work had been well carried out." German tubbing is started from a wedging curb and is bolted together as built up. When the rock itself is treacher- ous as well as wet, under-hanging tubbing is sometimes employed. In this case a wedging curb, faced on the bottom and provided with bolt holes, is set just above the shaft bottom. The segments are lowered to the bottom, and are grasped one at a time with a special pair of tongs and raised to the under side of the curb. Each segment is then sus- pended by two bolts with long threads and the tongs are removed. The lead gasket is inserted; the segment is raised to place by screwing up the nuts on the long bolts, and is then bolted up tight. The process is repeated as soon as the shaft has been deepened sufficiently. After each ring has been bolted up, the opening at the bottom between it and the rock is closed with plates and wedges, and the space behind is filled with cement grout poured in through holes in the segments. CHAPTER X CONCKETE LININGS. COSTS PER LINEAR FOOT FOR RECT- ANGULAR, ELLIPTICAL, AND QUADRILATERAL SHAFTS Two types of concreted shafts are to be considered: the circular or elliptical, with unsupported lining; and the rectangular, with reinforced concrete lining supported by steel beams, concrete buntons, or walls. In both, the con- crete is placed directly against the rock walls and an inner form only is required. From a construction standpoint the types are equally feasible, and the choice depends upon the cost. In several cases known to the writer a com- promise has been effected by shaping the shaft as a quadri- lateral with sides formed of circular arcs. For a single compartment air shaft the circular shape is in every way the most desirable, not only because the circular shaft is cheaper to sink than a square shaft of equal area, but also because a circular ring of plain concrete is the strongest lining possible with a given amount of material. In the case of a shaft with two or more compartments, the selection of the most economical shape requires some calculation. At first sight it would seem that a simple rectangular shaft, surrounded by a concrete wall only thick enough to be as strong as the usual timber lining, would be a satisfactory, as well as a cheap, shape, but this is not the case. A concrete lining, even when provided with weep holes, must resist some hydrostatic pressure; a timber lining has none to resist. Furthermore, permanent weep holes are most undesirable; the concrete should exclude the water entirely, and hence must be designed to bear very great pressure at considerable depth. Just what amount the theoretical pressure is reduced by the adhesion of the 129 130 PRACTICAL SHAFT SINKING concrete to the shaft walls and by the blocking of the fissures with grout cannot be calculated. In solid rock, where the FIG. 59. Rectangular Concrete Lined Shaft water enters in well-defined springs, the proper grouting of the springs will relieve the lining of all pressure. In very TABLE 1. QUANTITIES AND COSTS OF RECTANGULAR SHAFT Depth in feet 20 50 100 150 200 Total thickness of lining in inches 14 21 28 34 39 Quantities per linear foot: Concrete to neat line in cu. yds. 3.90 5.70 7.60 9.30 10.70 Concrete, actual in cu. yds 5.80 7.70 9.70 11.50 13.00 Excavation to neat line in cu. . yds 12.80 14.60 16.50 18.20 19.70 Excavation, actual in cu. yds. . . . 14.70 16.60 18.60 20.40 22:00 Weight reinforcing steel in pounds 256 443 650 845 1,030 Costs per linear foot: Forms $ 25.00 $ 25.00 $ 25.00 $ 25.00 $ 25.00 Concrete at $5 cu. yd 29.00 38.50 48.50 57.50 65.00 Excavation (see note *) 49.60 53.20 57.00 60.40 63.40 Reinforcing steel at $.02 Ib 5.10 8.90 13.0 16.90 20.60 Total $108.70 $125.60 $143.50 $159.80 $174.00 seamy rock, on the other hand, the lining may have to bear parctically the full hydrostatic pressure. In order to compare the costs of the different shapes, let * NOTE. Cost of excavation figured on basis of $4 per cubic yard for section containing 12 yards per linear foot; additional excavation at $2 per cubic yard. Thus, cost of 16 cubic-yard section = 12 X $4 + 4 X $2 = $56. These unit costs are for purposes of comparison only and should not be used for estimating. CONCRETE LININGS 131 us consider in detail three designs for a shaft with two 7 X 10 ft. hoist ways and an airway with an area of 100 FIG. 60. Elliptical Concrete Lined Shaft sq. ft. As the whole area of a hoist shaft is ordinarily used for the passage of air, the size of the air compartment TABLE 2. QUANTITIES AND COSTS OF ELLIPTICAL SHAFT ( to Depth in feet, ( 100 150 200 250 300 400 Thickness of lining in inches, ends 12 12 12 12 12 12 Thickness of lining in inches, sides 12 18 24 29 34 42 Quantities per linear foot: Concrete to neat line, cu. yds 2.60 3.40 4.30 5.00 5.70 6.80 Concrete, actual in cu. yds. 4.40 5.20 6.10 6.80 7.50 8.60 Excavation to neat line in cu. yds 15.20 16.00 16.90 17.60 18.30 19.40 Excavation, actual in cu. yds 17.00 17.80 18.70 19.40 20.10 21.20 Costs per linear foot : Forms $15.00 $15.00 $15.00 $15.00 $15.00 $15.00 Concrete at $5 cu. yd. ... 22.00 26.00 30.50 34.00 37.50 43.00 Excavation (see note*) . . . 54.40 56.00 57.80 59.20 60.60 62.80 Total $91.40 $97.00 $103.30 $108.20 $113.10 $120.80 may be reduced if the rest of the shaft is enlarged; the air- way must, however, be large enough to contain pipes and 132 PRACTICAL SHAFT SINKING ladders and to provide in addition an ample passage for air if the hoistways are temporarily closed. FIG. 61. Quadrilateral Shaft Let us assume a minimum thickness of 12 in. of concrete for a water-tight lining; also that in each case the lining TABLE 3. QUANTITIES AND COSTS OF QUADRILATERAL SHAFT Depth in feet Thickness of lining in fOto 1 100 150 200 250 300 400 inches 12 19 26 32 39 52 Quantities per linear foot : Concrete to neat line in cu. yds 2.70 4.40 6.20 7.90 9.90 13.90 Concrete, actual in cu. yds 4.50 6.30 8.20 10.00 12.10 16.20 Excavation to neat line in cu. yds 14.90 16.60 18.40 20.10 22.10 26.10 Excavation, actual in cu. yds 16.70 18.50 20.40 22.20 24.30 28.40 Costs per linear foot: Forms $15.00 $15.00 $15.00 $15.00 $15.00 $15.00 Concrete at $5 cu. yd. . 22.50 31.50 41.00 50.00 60.50 81.00 Excavation (see note*) . . 53.80 57.20 60.80 64.20 68.20 76.20 Total $91.30 $103.70 $116.80 $129.20 $143.70 $172.20 carries the entire hydrostatic pressure; then the specifica- tions for the three forms of shafts will be as follows: Rectangular Shaft. Fig. 59. Two hoistways, 7 X 10 ft.; CONCRETE LININGS 133 one airway, 10 X 10 ft. Ten-inch concrete dividing walls in place of buntons. Extreme inside dimensions, 10 X 25 ft. 8 in. Area airway, 100-sq. ft.; total clear area, 240 sq. ft. Thickness of lining at any point made equal to depth of simple beam of 10-ft. span required to sustain hydrostatic pressure at that point. Resisting moment and weight of reinforcement calculated by Johnson's formula, factor of safety 3. (Ultimate tensile strength of steel, 65,000 Ibs. per square inch, compressive strength of concrete in beam, 2500 per square inch.) Reinforcing steel set 3 in. inside of face of wall. Cost of forms, Table 1, includes cost of forms for dividing walls, and is therefore greater than the cost in the elliptical shafts. Excess of actual over theoretical quantity of excavation is estimated as 15 per cent, for 28-ft. shaft. This excess increases with the length of the shaft only, as the ends are drilled to line. Elliptical Shaft. Fig. 60. Extreme inside dimensions, 16 X 27 ft. Area of airway, 78 sq. ft. Total clear area, allowing for 10-in. buntons, 304 sq. ft. Strength of lining calculated on the assumption that the stress in the elliptical cylinder at any point is equal to that caused in a circular cylinder, with a radius equal to the radius of curvature of the ellipse at the given point, by the same hydrostatic pressure acting upon it. The lining is therefore made thicker at the sides than at the ends. To prove this proposition, assume the lining to be con- structed of a number of small portions, each the arc of a circle. The stress in each portion caused by the hydro- static pressure of the film of water between it and the rock is directly proportional to the radius, and the thickness of each section should therefore be made proportional to the radius. Considering any portion, as a-b, Fig. 62, the skew- back toward the side of the ellipse is formed entirely by the adjoining portion, while the skewback toward the end is formed partly by the adjoining portion and partly by the 134 PRACTICAL SHAFT SINKING rock. If the number of circular portions is indefinitely increased, the unbalanced end thrust of each will be taken up by the irregularities of the rock. Ultimate compressive strength of concrete, 3000 Ibs. per square inch; factor of safety, 3. Excess of actual over theoretical excavation assumed as 12 per cent, for smallest section. As the length of the shaft does not vary, this excess is constant. Quadrilateral Shaft. Fig. 55. Inside dimensions, 16 X 24 ft. 8 in. Radius of ends and sides, 23 ft. Area of airway, 94 sq. ft. Total clear area, allowing for 10-in. buntons, 294 sq. ft. FIG. 62 For calculating stresses, sides and ends are considered as portions of a 46-ft. circular cylinder. Ultimate compres- sive strength of concrete, 3000 Ibs. per square inch ; factor of safety, 3. Excess of actual over theoretical quantity of excavation assumed to be 12 per cent, for minimum length and to increase with the length. Methods of Working. The easiest way to concrete a shaft is to finish sinking, then start at the bottom and build up. Unfortunately this is feasible only for comparatively shallow shafts in hard dry rocks, and, ordinarily, successive lengths of lining must be placed as the shaft deepens, to protect the sides and cut off feeders of water. CONCRETE LININGS 135 When the shaft has been sunk as far as seems safe or desirable, hitches are cut in the sides, a set of bearing timbers is placed and a heavy plank floor laid upon them to support the concrete. In order to avoid injury to the concrete when sinking is resumed, the platform should be built 15 or 20 ft. above the shaft bottom. It is cheapest to cut the hitches near the bottom when the shaft is at the proper depth and then to sink three or four cuts further; scaffolding is thus made unnecessary as it is easy to place timbers in hitches already prepared. In a rectangular or elliptical shaft transverse bearing timbers are placed; in a circular shaft four timbers placed in the form of a square make the best platform. In any case an opening should be left in the bucket way so that the bottom is accessible. Forms are started from the platform and are built in rings 5 to 10 ft. high. When each ring of forms is completed a temporary floor is laid on top of it. Concrete mixed at the top of the shaft is lowered in shaft buckets and dumped on the floor, whence it is shoveled behind the forms. To prevent loss of concrete the floor must be laid with tight joints, and this is most easily accomplished by making it in sections as large as can be lowered into the shaft. An- other plan is to dump the concrete from the bucket into the forms direct through a movable chute; the necessity for laying the tight floor is thus obviated. A |-yd. batch mixer (such as the Smith or Ransome) gives the best results. One-half yard of wet concrete is about all an ordinary shaft bucket will hold without spilling. The use of a batch mixer makes it possible to use only one bucket without losing time, as a batch is being lowered and dumped while the next is being mixed. The mixer should if possible be set below the ground level (see Fig. 63) to avoid elevating the materials. Below the mixer a plat- form is placed for supporting the bucket while it is being filled. This platform should be 3 ft. wide and so situated that a bucket hanging free on the rope will clear it 10 or 12 in., and should be provided with a hand rail except for 136 PRACTICAL SHAFT SINKING 4 ft. immediately in front of the mixer. When concreting, two men stand on the platform, one on either side ; the empty bucket is hoisted slightly above the platform level, is grasped FIG. 63. Lowering and Placing Concrete by the two men and swung in under the discharge chute of the mixer, and is then lowered. When filled it is hoisted slightly, swings out over the shaft and is steadied by the men on the platform before being lowered. CONCRETE LININGS 137 By working as outlined above with a good organization it is easy to place 12 or 15 one-half yard batches per hour, and a shaft lining containing as much as 6 yds. of concrete per linear foot can thus be placed at the rate of more than a foot an hour about as fast as timber. It is the time required to construct the foundation platform, to set the forms, and to connect a new section of lining to the one above it that makes the process slow. Foundation platforms must be built and closures must be made; time can be saved only by reducing the number. Plenty of forms should therefore be provided, and the sec- tions made as long as possible. The design of forms, both as regards strength and finish and facility of erection, demands careful consideration. Forms. The writer has had experience with three types of forms. The first, consisting of wooden slabs, was used for lining a 17 X 33 ft. elliptical shaft at Tug River, W. Va. (Engineering News, November 7, 1904). The slabs were made of 2-in. vertical lagging planks nailed top and bottom to double 2 X 12 in. centers. They were 5 ft. high, and 8 slabs made up a complete ring. These forms made a satisfactory wall, but were heavy and were greatly damaged by moving. Eight to ten hours were required to set one ring; the work was divided into two shifts, one setting forms and one concreting, so the progress made was only 5 ft. per day. The second type, consisting of steel slabs, was used on several waterway shafts on the Catskill Aqueduct. These shafts are circular, about 14 ft. 6 in. in finished diameter, and a perfectly smooth surface is required. The slabs are 5 ft. high and are made four to a ring. Forty feet of forms were provided for each shaft. Two rings were erected at a time, the concrete being tamped and spaded with long- handled tools, and when new it was possible to erect and fill two rings in twelve hours. With use the forms become more difficult to set: the progress, including platforms and closures, averaged 10 ft. per day. A pair of wooden key 138 PRACTICAL SHAFT SINKING blocks is provided at opposite joints in each ring. These are chopped out to release the forms. After a section of lining is finished, the steel slabs are usually left in place until the next section is ready and then moved down, a ring at a time. If the section to be concreted is longer than the available forms, a working platform may be suspended below the forms with ropes and the slabs taken off at the bottom and moved up. The slabs should always be cleaned and oiled before being used again. The third type consists of angle-iron rings spaced 4-ft. centers and lagged with vertical 2-in. plank. Wooden nailing strips are bolted to the angles. These forms, although they make a surface inferior to the steel forms, are cheaper and easier to place. One ring at a time is set and filled, and by working continuously four or five can be completed in twenty-four hours. These forms are removed, taken to the surface and cleaned after each section of lining is finished. Placing. Concrete should be mixed wet, even though considerable water is present in the shaft, and should be thoroughly spaded next the forms. Springs of any volume appearing in a section that is to be lined should be taken care of in advance of the lining : this can be done by drilling a hole into the water-bearing seam, inserting a pipe long enough to carry the water out into the shaft, and caulking around the pipe. All springs should be piped through the forms into the shaft before concrete is placed, Fig. 63a, for if this precaution is neglected a very slight inflow may accumulate enough head to disrupt the green concrete and cave in the forms. The writer has known this to actually happen and has had to dig out about 80 sq. ft. of lining dis- placed in this way by the water from one tiny spring. Grouting.* The drainage pipes should be provided at the inner ends with sleeves set flush with the face of the wall. If the concrete has been properly placed and too much water has not been encountered, the shaft can be made dry by plugging the sleeves. If, however, the concrete is .porous, * See Appendix A. CONCRETE LININGS 139 it may be necessary to force grout through the pipes until all crevices are filled. The grout is mixed very thin, and can be pumped in with a high-pressure pump or expelled from a tank and driven into the pipe by the use of high-pres- sure compressed air. Concrete can be made absolutely water-tight in this way if enough grout pipes are provided. In closing, the writer wishes to express his gratitude to Mr. Evan Edwards, of Scranton, whose knowledge of prac- tical shaft sinking has been of the greatest assistance in the preparation of this book. APPENDIX A GROUTING SHAFTS 4 AND 24, NEW YORK CITY AQUEDUCT SHAFT 4 SHAFT 4 is concrete-lined circular shaft sunk through the Fordham Gneiss near Jerome Park Reservoir. The depth to tunnel invert is 242 ft.; the finished diameter of the concrete lining is 14' 0", and the effective average thick- ness of the lining in normal rock is 13". Sinking progressed without incident on the "one drilling and two mucking shift" plan until a depth of 149 feet was reached; in the first round drilled below this depth clear water was found in four of the thirty holes. The rock was solid and each hole was plugged with a wooden plug wrapped in sacking as soon as the bottom was reached. It was thought that the water might be only a pocket, so after a proper pump had been placed one of the plugs was removed. Pumping was continued for two weeks, during which time the upper part of the shaft was lined and appliances for grouting obtained. As the flow was not appreciably diminished, it was then decided to grout the water-bearing crevice through the drill holes. The grout mixer, which was of the air stirring type standard on the aqueduct, was lowered to the shaft bottom and coupled to the air line, and was then connected succes- sively to the various wet holes. In order to make connec- tions, pieces of 2-inch pipe 3 feet long with standard threads at one end were given a gradual taper at the other; as soon as a plug was drawn from a hole the tapered end of the pipe was wrapped with sacking and driven in tight, and a 2-inch stop cock screwed on. The mixer was attached to the holes by a heavy hose. The first series of holes was 140 APPENDIX A 141 grouted in one shift; the next day more holes were drilled and more clear water met with, and grouting was resumed that night. After 12 hours the holes refused to take any more grout, and operations were discontinued for 24 hours. Regular sinking was then resumed and no more water was met for a week. About 200 sacks of neat cement were used in blocking this fissure. At a depth of 181 feet the water was again found in the sump holes, and grouting was once more necessary. This time the water was heavily charged with sand and pieces of disintegrated rock; the rock around the collars of the drill holes was seamy and it was harder both to make good connections and to force grout into the holes after the con- nectiong were made. Grouting was nevertheless persisted in and in three weeks 130 holes from 10 to 20 feet deep were drilled in the shaft bottom, and over 50 cubic yards of grout (mostly neat cement) was forced into the fissures at pres- sures up to 240 pounds per square inch. Almost every hole drilled met some water, and the usual procedure was to drill five or six holes, grout them, lay off a shift or two to permit the grout to set, and then to drill five or six more holes. The depth at which water was met gradually in- creased, and it was therefore possible to sink four feet during the three weeks of grouting. The leakage over the shaft bottom, however, gradually increased to 85 gallons a minute. At the end of this period the shaft bottom was so thoroughly perforated that ''there was no sound rock left to drill into and, after an unsuccessful attempt to stop the leakage with a concrete blanket, sinking was resumed. It was found in passing through that the disintegrated area was a band varying from 1 to 5 feet in width, circling the shaft, 10 feet higher on the east than on the west side and twisted and folded in every direction. Below this was solid and perfectly sound rock. The sand was compacted so thoroughly by the pressure 142 APPENDIX A to which it had been subjected that it showed no tendency to wash out, and the flow into the shaft did not appreciably increase. After excavating 10 feet below into the solid rock, the shaft was concreted; a special section with a minimum of 24 inches of concrete was placed for 20 feet, extending into the solid rock above and below. Reinforcing steel, con- sisting of 1-inch rods, 24 inches apart, vertically and hori- zontally, was placed 18 inches from the face to prevent cracking. The disintegrated area was first lined with thin sheet iron and the water was led through the forms before concreting. The space back of this sheet iron was packed with rock. Five days after concreting the holes were plugged, and the gauge showed 77 pounds per square inch pressure back of the lining. The leakage through the concrete after the holes were plugged was only one or two gallons per minute. When the concrete had set for a month this leakage was entirely cut off by grouting the holes. SHAFT 24 Shaft 24 is of the same general construction as Shaft 4 and penetrates blocky and seamy granodiorite for its entire depth in the rock, Elevation-76 to Elevation-269. At intervals horizontal seams were encountered generally \ inch to | inch thick which were filled with finely crushed rock that allowed water to flow into the shaft, usually in only one point of the seam. As the seams were encountered holes were drilled into them 2 or 3 feet deep wherever there was any leakage and when the shaft was concreted these holes were fitted with grout pipes and were grouted. No great quantity of water was met with until at Elevation-221, while drilling a round, a flow of 240 gallons a minute was struck, all the water coming out of one hole. This water was under the full hydrostatic pressure due to the head and flooded the shaft. After about a week's delay, in which APPENDIX A 143 time large pumps were obtained, the shaft was emptied. Grouting was then commenced, using the same general methods as were used at Shaft 4. In all, 10 holes were drilled and 75 cubic yards of neat cement grouting was pumped in under pressures up to 400 pounds per square inch. The leakage into the shaft was reduced by this grouting to about 25 gallons per minute. APPENDIX B SEVERAL of the shafts of the City Aqueduct on the lower east side of Manhattan Island and in Brooklyn were sunk through great depths of water-bearing sand by the pneu- matic caisson method. The caissons are of two sizes, 15 feet 4 inches and 18 feet in diameter, and 2 feet and 3 feet thick respectively, and are heavily reinforced with vertical and horizontal rods. At the bottom of each a heavy steel shoe is imbedded to form a cutting edge. The vertical reinforc- ing rods are attached to the shoe. The roof of the working chamber is formed by a heavy reinforced concrete deck with two openings, to which the air shafts for the man lock and for the material lock are connected. Each shaft chamber was first excavated and timbered square to about the ground water level, and the caisson was then started from the bottom of the chamber and built up to the full height before sinking. Steel forms were used throughout. The deepest caisson projected over 60 feet above the ground before sinking was started. Excavated material was handled by a stiff-leg derrick. The caisson was loaded with pig iron, and the space between the shafting and the concrete filled with excavated sand for additional weight. Sinking proceeded rapidly in three shifts, at one of the shafts rock being reached through 55 feet of sand in five days. The most difficult part of the operation is the sealing of the caisson into the rock, so that the air can be safely taken off. To accomplish this the ledge is leveled off and the rock excavated for several feet, the caisson meanwhile being supported on timber posts. The rock is then thor- oughly cleaned with high pressure air, a one-to-two mortar collar is built around the shaft | of an inch back of the 144 APPENDIX B 145 outer edge of the shoe, and the posts are then shot out, allowing the caisson to sink through the collar into its final CITY TUNNEL Compressed Air Caiss. Appendix B position. The space between the collar and the caisson is then grouted through pipes previously set in the collar. INDEX After-cooler, 27. Air-box ventilator, 79. Air compressor, Corliss, 27. straight-line, 26. two-stage, 26. Air-drills, 2, 72-75. hose, 78. lift, 88. - lock, 60. Anhalt Government Salt Mine, freez- ing, 93. Anzin colliery cementation, 105. Bearing timbers, 41. Bell, 24. Bench, 67. Bethune colliery cementation, 105. Billy, 25. Bits, drill, 70, 73. Blacksmith-shop tools, 31. Blasting, 66, 68, 69. Blowers, 29, 80. Blow pipe, 62. Boilers, 17. Bore holes, 9, 92-94. Borers, percussion, 88. sack, 86. Boring process, 97-102. progress, 102. tools, 100, 101. Brakes, 23. Brick lining, 124. Buckets, 21, 22. Buildings, 29. Bull chain, 21. Buntons, 35, 119, 121. Caissons, 43-63 circular, 44. open, 43-58. Caissons, pneumatic, 59-63. rectangular, 43. Calumet shaft, 4. Carnegie steel sheet piling, 39. Central power plant, 27. Cementation, 102-106. Chambers, W. H., 112. Chapin Mine Company freezing, 93 Chaudron, M. J., 97. Churn drill, 71. Chute, 21. Circular concrete lined shaft, 129. Column, 75. arm, 75. Compound sinking drum, 90. Compressors, air, 26. Concrete, 43, 129-139. forms, 137, 138. mixer, 135. placing, 138. shaft linings, 129-139. timbers, 119. Conisboro sinking, 112. Contract, features of, 5, 6. form of, 10-12. Contract prices, 84. Corliss air compressor, 27. Cost of concrete lining, 130-132. plant, 32. sinking in rock, 81-83. sinking through surface, 49-51. timber, 121, 123. Curb for brick lining, 124. D. L. & W. caisson, 43, 54-58. Derrick, 20. Direct cementation, 102-106. Drainage of rock water, 138. surface water, 34, 42, 43. Drill, air, 2, 72-75. ' 147 148 INDEX Drill, diamond, 9. hand, 70, 71. Drill holes, depth and inclination, 68, 69. Drill mountings, 75, 76. steel, 70, 73. Drilling frame, 76. Dummy, 25. Dump car, 21, 22. Dynamite, 2, 67. thawing, 30. Electric hoist, 4, 24. light, 27, 29. Elliptical shaft, 131, 133. End plate, 35, 121. Engines, hoist, 20, 23, 24. Excavating lock, 62. Excavation under air, 60. Explosives, 2. Fan, 29, 80. Feed-pump, 18. Feedwater heater, 18. Fire and water excavating, 1. Firm earth, 35, 36. Fore poling, 41. Forms, concrete, 137, 138. Freezing period, 93. Freezing process, 35, 91-96. Gas engine, 24. Gelatin, 67. Generator, 27. Grab bucket, 86. Grout, 105, 138. mixer, 105. tank, 106. Guides, 25. Gunpowder, 2. Hand drill, 70,71. Hanging bolts, 36. Haniel & Lueg, 97. Hammers, 71. Hay, 43. Head-frame, 20-22. Historical mention, 1. Hitches, 120. Hitch timbers, 119, 122. Hoisting apparatus, 20. engines, 20, 23, 24. Horden sinking, 116. Hooks, 22. Hose, 78. Hydraulic jacks, 85. Injector, 18. Kind, 97. Kind-Chaudron boring process, 97- 102. Lackawanna steel sheet piling, 39. Lagging, 36, 122. Lens cementation, 103. Leyner drill, 75. Lifting water, 107-117. Lining for shafts, 118-139. Little giant drill, 73. Locking through, 61. Mammoth pump, 88. Man-lock, 60. Mixer, concrete, 135. grout, 105. Moss box, 98. Mt. Lookout freezing, 95. Non-rotating rope, 25. Operation of concreting shaft, 134- 136. pneumatic caisson, 62. sinking shaft, 78. Packing, 122. Pile driving, 40. Pile hammer, 40. Piping, 17, 18, 110. Plant, contractor's, 15. cost of, 32. location of, 32. for sinking, 16-32. Pneumatic process, 34, 59-63. limit of, 60, 63. INDEX 149 Pneumatic caisson, 59. Poetsch, 91. Poling boards, 42. Powder house, 30. Primary power, 16. Progress, sinking caisson, 47. sinking in rock, 80, 81, 83. Prospect holes, 9. Pulsometer, 112. Punch blocks, 35, 121. Pumps, sinking, 107, 113. Pumping, 107-117. Quadrilateral shaft, 132, 134. Quicksand, 34, 60, 65. Rectangular shaft, 2, 130, 132. Reheater, 27. Reenforcement, 44, 133. Relievers, 67. Rheinpreussen colliery sinking, 90. Riemer, J., 96. Ring timbers, 121. Risk of water, 6. Rondout caisson, 44. cementation, 105. Rope, 23, 25. Sack borer, 86, 87. Safety hook, 22. Saw, 29. Sealing caisson to rock, 51, 63. Seals, details of, 52, 57. Secondary power, 26. Sergeant drill, 73. Sheet piles, 37, 38. Shafts, depths of, 4. sizes and shapes of, 2, 3. Shaft bar, 75. Shaft linings, 118-139. "Shaft sinking in difficult cases," 96. Shield method, 63-65. Shifts, 78. Shoes, 45, 48, 63, 85. Sinking-drum process, 85-91. Sinking pumps, 107, 113. in rock, 66-84. in surface, 33-65. Skin to skin timber, 42. Slugger drill, 73. Soft ground, 36-65. Specifications, 13-15. Speed of sinking caisson, 47. in rock, 81, 83. Spoil, 5. Steam hammer, 40. Steam hose, 78. Steel sheet piles, 39. Straight-line air compressors, 26. "Straight through" air lock, 62. Sump, 67. Supplies, 7, 31. Surface ground, 33-65. Tamarack shaft, 4. Thawing dynamite, 30. Timber, supply of, 8. Timbering firm earth, 35. rock, 119-124. soft ground, 36-42. Time limit, 6. Tool room, 31. Tools for sinking, 31. Tomson system, 117. Tripods, 76. Tubbing, English, 125. for boring process, 99. German, 128. Underground water, 8. Underhanging tubbing, 128. Ventilation, 79. Wages, 79. Wall plate, 35, 121. Water clause, 6, 11. Water hoist, 4, 117. Water in surface, 33. Water Leyner drill, 75. Water, pumping of, 107-116. Water rings, 15, 109. winding, 117. Wedges, 123, 127. Wedging curb, 127. Wet sinking at Conisboro, 112. Horden, 116. TN Shurick - Coal mine surveying ; MAY I 9 19! from which Itwasborrowed. Engineer!^* Library A 000195842 SEP "ra