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Transportation
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A NEW PLAN OF TUNNELLING, calculated for
opening a Roadway under the Thames.
By M. J. BRUNEL, Esq. C.E. F.R.S.
To discover convenient and efficacious means for opening a spacious sub-
terraneous communication between the shores of a great river, without oc-
casioning any obstruction to the navigation, has long been a desideratum
of considerable importance with the public, and in the estimation of scientific
engineers. The difficulties which have opposed themselves to every attempt
that has been hitherto made to execute a Tunnel under the bed of a river,
have been so many and so formidable as to have prevented its successful
termination in those instances where the attempts have been made.
To propose therefore the formation of a Tunnel after the abandonment
of these several attempts, may appear somewhat presumptuous: on inquir-
ing, however, into the causes of failure, it will be found that the chief dif-
ficulty, to be overcome, lies in the inefficiency of the means hitherto employ-
ed for forming the excavation upon a large scale.
In the case of the drift-way made under the Thames at Rotherhithe in
1809, the water presented no obstacle for 930 feet; and when a great body
of quicksand gave way and filled the drift, the miners soon overcame this
obstruction, and were able to proceed until they were stopped by a second
irruption, which, in a few minutes, filled it. Nothing comes more satisfac-
torily in support of the system that is adopted here, than the result of the
operations that were carried, under that circumstance, to an extent of 101 I
feet, and within 130 feet from the opposite shore.
It is to be remarked that at the second irruption, on examining the bed of
the river, a hole was discovered 4 feet diameter, 9 feet deep, with the sides
perpendicular;-a proof that the body of quicksand was not extensive ; but
what is most remarkable, is, that this hole could be stopped merely by
throwing from above, clay partly in bags and other materials: and after
pumping the water out under a head of 25 feet of loose ground and 30 feet
of water, the miners resumed the work, and proceeded a little further;
but finding the hole at the first irruption increased, and the filling over the
second very much sunk, the undertaking was abandoned.
2
A x* * ** *
tº 3
º & * $ f Jºr 'a $3.
The character of the plan before us consists in the mode of effecting theº
excavation, by removing no more earth than is to be replaced by the body of .
the Tunnel, retaining thereby the surrounding ground in its natural state of
density and solidity.
In order so to effect an excavation 34 feet in breadth by 18 feet
6inches in height, the author of this plan proposes to have the body
of the Tunnel preceded by a strong framing of corresponding
dimensions, as represented in the accompanying drawings, and in
the model proposed to be submitted for inspection. The object
of this framing is to support the ground, not only in front of the
Tunnel, but at the same time to protect the work of excavation
in all directions. The body of the Tunnel, which is to be con-
structed in brick, is intended to be fitted close to the ground; and
in proportion as the framing is moved forward, so the brick work
is made to keep pace with it. But as this framing could not be
forced forward all in one body, on account of the friction of its
external sides against the surrounding earth, it is composed of
eleven perpendicular frames which admit of being moved singly
and independently of each other, in proportion as the ground is
worked away in front. These several frames are provided with
such mechanism as may be necessary to move them forward as well
as to secure them against the brick-work, when they are stationary.
It is to be observed, that six alternate frames are stationary, while
the five intermediate ones are left free for the purpose of being
moved forward, when required; these, in their turn, are made
stationary for relieving the six alternate ones, and so on. Thus
the progressive movement of the framing can be effected.
In order that a sufficient number of hands may be employed
together, and with perfect security, each perpendicular frame is
divided into three small chambers, which may properly be deno-
minated cells. By this disposition, 33 men may be brought to
operate together with mechanical uniformity, and quite inde-
pendent of each other. These cells, which are open at the back,
present in front against the ground a complete shield composed
of small boards, which admit of being removed and replaced
singly at pleasure.
It is in these cells that the work of excavation is carried on.
There each individual is to operate on the surface opposed to
him, as a workman would cut out a recess in a wall for the
purpose of letting in a piece of framing, with this difference only,
that instead of working upon the whole surface, he takes out one
of the small boards at a time, cuts the ground to the depth of a
few inches, and replaces the board before he proceed to the next.
When he has thus gained from 3 to 6 inches over the whole
3
surface, (an operation which it is expected may be made in all
the cells nearly in the same time,) the frames are moved
forward, and so much of the brick-work added to the body of
the Tunnel. Thus intrenched and secure, 33 men may be made
to carry on an excavation which is 630 feet superficial area, in
regular order and uniform quantities, with as much facility and
safety as if one drift only of 19 feet square was to be opened by
OIle Iſlaſh.
The drift carried under the Thames in 1809, which was about
the size of these cells, and was excavated likewise by only one
man, proceeded at the rate of from 4 to 10 feet per day. In the
plan now proposed, it is not intended the progress should ex-
ceed 3 feet per day, because the work should proceed with me-
chanical uniformity in all the points together.
With regard to the line of operation, if we examine the nature
of the ground we have to go through, we observe under the third
stratum, which has been found to resist infiltrations, that the sub-
strata to the depth of 86 feet are of a nature that present no ob-
stacle to the progress of a Tunnel; we are informed that no
water was met there. It is therefore through these substrata
that it is proposed to penetrate, and to carry the line that is to
cross the deep and navigable part of the river, leaving over the
crown of the Tunnel a head of earth of from 12 to 17 feet in
thickness quite undisturbed.
Admitting that in descending to or in ascending from that line
we should come to a body of quicksand, such as that which was
found within about 200 feet from the shore, it is then we should
find in the combinations of the framing, before described, the
means that are necessary for effecting, upon a large scale, what
is practised, on a very small one, by miners when they meet with
similar obstacles. Indeed, were it not for the means of security
that are resorted to on many occasions, mines would inevitably
be overwhelmed and lost.
Notwithstanding we may encounter obstacles that may retard
the daily progress, it is with satisfaction we contemplate that
every step we take tends to the performance and ultimate com-
letion of the object; and if we consider that the body of the
#. must exceed the length of Waterloo Bridge, it must be
admitted that, if, instead of two years, three were necessary to
complete the undertaking, it would still prove to be the most
economical plan practicable for opening a land communication
across a navigable river.
No notice is taken here of the mode of constructing the de-
scents or approaches into the Tunnel; because whatever form or
direction it may be found necessary to adopt, it is obvious
4
no difficulties oppose themselves to the accomplishment of that
part of the work, the expense of which is however taken into
account in the estimate.
Nature of the Ground under the Bed of the River at Rotherhithe
at a short Distance below the Place now proposed for opening
a Roadway.
No. Feet. Inches.
1. Stratum consisting of brown clay - †-e 9 O -
2. Loose gravel with a large quantity of water - 26 8
3. Blue alluvial earth inclining to clay - sº 3 0
4. Loam asº <º sº sº sº sº 5
5. Blue alluvial earth inclining to clay mixed with
shells tº- e- sº sº- wº 3 9
3. Calcareous rock, in which are imbedded gravel
stones, and so hard as to resist the pick-axe,
and to be broken only by wedges dº 6
7. Light-coloured muddy shale, in which are im -
bedded pyrites and calcareous stones - 4 6 º'
S. Green sand with gravel and a little water - O 6
9. Green sand * * * * sº - 8 4
68 4
*...* It is proposed to raise a Capital of £ by transferable shares of £100 each
for carrying the above project into effect,
*
Printed by Richard Taylor,
Shoe-lane, London.

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