IMPROVEMENTS IN CONSTRUCTING TUNNELS, AND IN APPARATUS TO BE USED FOR SUCH OR SIMILAR PURPOSES
Year: 1849

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, SAMUEL
DUNN, of Doncaster, in the County of York, Gentleman, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Fifth day of June, in the twelfth year of Her reign, did,
for Herself, Her heirs and successors, give and grant unto me, the said
Samuel Dunn, Her especial licence, full power, sole privilege and authority,
that I, the said Samuel Dunn, my exors, adññiors, and assigns, and such others
as I, the said Samuel Dunn, my exors, adiñiors, or assigns, should at any
time agree with, and no others, from time to time and at all times during
the term of years therein mentioned, should and lawfully might make, use,
exercise, and vend, within England, Wales, the Town of Berwick-upon-
Tweed, and in all Her Majesty's Colonies and Plantations abroad, and in the
Islands of Jersey, Guernsey, Alderney, Sark, and Man, my Invention of
"IMPROVEMENTS IN CONSTRUCTING TUNNELS, AND IN APPARATUS TO BE USED FOR
SUCH OR SIMILAR PURPOSES;" in which said Letters Patent is contained a proviso
obliging me, the said Samuel Dunn, by an instrument in writing under my
hand and seal, particularly to describe and ascertain the nature of my
said Invention, and in what manner the same is to be performed, and to
cause the same to be inrolled in Her Majesty's High Court of Chancery within
six calendar months next and immediately after the date of the said in part

page_text: recited Letters Patent, as in and by the same, reference being thereunto had,
will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the said
Samuel Dunn, do hereby declare that the nature of my said Invention, and
the manner in which the same is to be performed, is particularly described
and ascertained in and by the following description thereof, reference being
had to the Drawings hereunto annexed, and to the letters and figures marked
thereon (that is to say):-
My Invention of "Improvements in Constructing Tunnels, and in Apparatus
to be used for such or similar Purposes," relates to an improved mode of con-
structing tunnels, passages, or ways under water, such as from side to side of
rivers, channels, straits, estuaries, or other similar localities. Instead of sinking
a shaft to a suitable depth and at a convenient distance from the water side,
and boring or digging away the earth in a-horizontal direction under the river
or water way, and building up a suitable structure under ground, as is usually the
case, I commence a cutting, tunnel, covered way, or trench at a convenient
distance from the water, and build the same at a proper descending angle, in
the usual or any suitable manner, until I reach the water's edge or thereabouts;
and when I commence that part of the work where the danger of the water
breaking into the tunnel may be apprehended, I adapt to the mouth of the
tunnel an apparatus, which I denominate a protecting cylinder, shield, or sub-
marine plough. This protecting cylinder, shield, or plough is made to point
towards the river or water channel, and rests on a bed that is prepared for it to
lie upon, exactly at the angle at which it is required to make the tunnel.
This protecting cylinder, shield, or plough is constructed in such a manner that
the remaining portion of the tunnel may be built up inside of it, bit by bit,
the protecting cylinder or shield being moved onward from time to time as the
tunnel inside is built up. The tunnel is constructed of strong planking,
covered on the outside with a layer of gutta percha or some other suitable
waterproof material, and the inside of the tunnel is further lined with sheets of
strong boiler plate iron, firmly bolted together, the whole being so constructed
as accurately to fit the inside of the cylindrical or elliptical part of the protect-
ing cylinder or shield, so as perfectly to prevent the entrance of any water, and
yet at the same time allow of the protecting cylinder or shield to be advanced
from time to time as the building operation inside proceeds.
Having thus briefly set forth the object and nature of my Invention, I will
now proceed to describe more in detail the means I propose for carrying the
same into effect, reference being had to the accompanying Drawings, which
represent various views of part of a tunnel constructed upon my improved

page_text: plan, showing also the manner of constructing and adapting the shield or
protecting cylinder thereto, and the mode of advancing the same when
required.
Fig. 1 represents a longitudinal vertical section taken through a part of the
tunnel and the protecting cylinder, shield, or plough, and the apparatus
connected therewith.
Fig. 2 represents a transverse section of the shield, shewing the face of the
piston O, hereafter described, and also the hydraulic apparatus for working the
same.
Fig. 3 represents a transverse section of the tunnel and protecting shield or
cylinder.
Fig. 4 represents a horizontal section of a part of the tunnel, and the pro-
tecting cylinder or shield, taken through the middle thereof, and shewing also
the hydraulic apparatus.
Fig. 5 represents a vertical longitudinal section of the tunnel and shield,
showing a modification of the application of the hydraulic power.
Fig. 6 is a transverse section of the shield beyond the plate N.
The tunnel is constructed of two thicknesses of strong planking forming two
elliptical cylinders, and inside of these there is a casing made of stout boiler-
plate iron; the outside of the planking is covered with a coating or layer of
gutter percha, or some other suitable waterproof material, cement, or compo-
sition. I would, however, here observe, that cylinders formed of other
materials might be substituted for any of the above; and it might be desirable
to replace the gutta percha or one of the wooden cylinders or both, by one
made of wrought or cast iron, galvanized or otherwise, so as more effec-
tually to secure the tunnel from injury by anchors of vessels or other objects,
should the tunnel be constructed within reach of such instruments, or where
other circumstances might require a change of material. The planks to be
used for the purpose of forming the two cylinders represented in the Drawings
are jointed together lengthwise by a dovetail or other suitable joint. The
planks are each two and a half inches in thickness, and three feet in length,
the length of them, however, will depend upon the distance it may be proposed
to move forward the protecting cylinder or shield at every onward movement,
the planks being intended to fill up the space that the shield is to be advanced
at one operation, as will more clearly appear bye and bye. The outer cylinder
of planking is seen at B, and the inner one at D. The joints of the outer
cylinder are shewn at C, a part of the inner cylinder being cut away for the
purpose, and the joints of the inner cylinder are seen at E, a part of the inner

page_text: casing being removed to show the same. The edges of the planks may be
jointed in any suitable manner, a rabbet or overlap being cut in the edge of
cach plank for the purpose of making a secure joint, and so as that they may.
fit and present an even surface when in their places. By inspecting the Draw-
ings it will be seen that the two thicknesses of planking are arranged in such a
manner as to form break joints; (that is to say,) the joints of the cylinder B are
covered by the middle of the planks of the cylinder D, and vice versa; the two
cylinders should also be firmly attached to each other by bolts, studs, or screws,
so as to be firmly and securely united to each other. The onter cylinder B is
covered with a coating or layer of gutta percha, or some other suitable water-
proof material, as cement or composition, as shown at A; and this cylinder B
is also countersunk at intervals, so as to receive between it and the coating of
gutta percha a hoop or hoops of bar iron H, about three quarters of an inch
thick, and four and a half inches broad, bent to the shape of the cylinder, and
securely fastened at the ends, either by their being welded together, or bolted
in such way as to form stout bands at intervals, in order to prevent the planks
giving way outwards. These bands or hoops H may be so placed as to cover
the joints of the ends of the planking, care being taken to place a rim against
the ends of the planks to bring them flush with the band or hoop, so as to take
the bearing or thrust of the piston at the same time; or a band or hoop of
half the breadth may be placed temporarily at the joint, and removed, to be
replaced by one of the whole breadth after the piston has been pushed forward.
Instead of making the joints, as shewn at C and E, to fasten the ends of the
planks of the cylinders B and D, hoops or bands of iron, similar to those on the
outside of the cylinder B, may be placed inside the cylinder D, opposite
to those outside of the cylinder B, so as that bolts or spikes fastened to the
latter may pass through both series of the planking and be fastened by nuts;
or, if spikes are used, they must be clenched on the inside of the inner bands
so as to hold both bands and planks firmly together, the planks of the inner
cylinder D being countersunk to receive the bands and make all flush. The
inner surface of the cylinder D is covered with a casing made of boiler-plate
iron F, about five eighths of an inch in thickness, each plate having the same
length as the planks forming the cylinders B or D, and curved transversely, so
as to make four plates to fit exactly round the interior of the tunnel. These
plates F are jointed together, as shewn in the Drawing, by means of bolts and
nuts, flanges G being made to receive the bolts, and the interstices between the
flanges being filled with iron, cement, or other substance, so as to render them
perfectly water-tight.

page_text: I will here observe, that both the order of these cylinders and the material of
which they are made, as well as the size of them, might be changed or modified
to suit the kind of matter through which the tunnel would require to be built,
and the shocks or injuries to which it might be exposed.
The moveable protecting cylinder or shield, in which the tunnel is built or
formed, is shewn at I, I, which represents a strong outer casing, made of cast
or wrought iron, or other suitable material. This protecting cylinder or shield
surrounds and incloses the end of the tunnel, and fits so closely and accurately
round the outer surface thereof as effectually to prevent water from entering
therein, being provided also near its extremity L with a collar of leather i,
similar to what is used for the collar of hydraulic presses. The cylindrical or
elliptical part of the protecting cylinder or shield, or that part which extends
from K to L, should be about seventeen feet in length; but this length may
be varied to suit circumstances, and the outer or projecting part M. should be
formed something like a plough, presenting a pointed and an angular edge to
the matter it would have to pass through, but its profile might either present
a curved or straight line from the extreme point to the part inarked K, as well
as the form represented in the Drawing. The sides of this front or projecting
part are splayed off, as indicated by the dotted curve in Fig. 1. The edge
and point should also be coated with steel. This front or projecting part is
provided on the inside with longitudinal strengthening pieces, shewn at g, g, in
Fig. 4, and by dotted lines at 9, 9, in Fig. 2; they are made of wrought or
cast iron, and divide the front part of the shield into several divisions or com-
partments communicating with each other by holes made in the division plates
for that purpose. These division plates are securely fastened to the under and
upper part of the shield, and to the elliptical division plate N, which divides
this part of the shield from that on the other side of it in the direction of the
tunnel. This division plate N is firmly secured to the inside of the protecting
cylinder or shield in such manner as effectually to prevent any fluid or other
matter passing from one side of it to the other, except through the pipe or
passage to be spoken of hereafter. In order to give additional strength to the
front part of the shield, so as to enable it to withstand the pressure of matter
above and about it, I propose to fill the spaces between the division plates g, g,
with compressed air, to be forced into them by means of a common condensing
air pump, to be placed at any convenient place within the tunnel, or outside
near the entrance thereof. A connecting pipe a, leading from and attached
to this pump, would convey the compressed air from it to the divisions or
compartments beyond the plate N. This pipe a passes through a stuffing box

page_text: b on the piston O, and has its open end securely fastened to the plate N on
the side next to the division plates 9, g, so that air forced into this pipe by the
action of the pump would be carried by it into the compartments at the back
of the plate N. It is intended to give such a degree of compression to the air
in the compartments as would, by the clastic force of the air, counterbalance
the external pressure on the outer surface of the front of the shield; (that is
to say,) the expansive force of the compressed air within this part of the shield
would neutralize the effect of the pressure without, the air being compressed
to such a degree as to produce this result, so that to whatevever degree this
external pressure might amount, the air within should be compressed so as to
give it elastic force enough to counterbalance it, or as much more as might be
deemed advisable. A moveable elliptical piston O is made to fit the interior
of the protecting cylinder or shield with nicety, being furnished with leather,
bempen, or metallic packing at P, P, and being provided with strengthening
ribs c, c.
It will be understood that the interior of the cylinder I,, from the
piston O to the plate N (when the piston is at its greatest distance from this
plate), must be accurately bored, so as to allow the piston to work properly
therein. The space Q between the piston O and plate N is filled with water
or other fluid through a pipe X, by a pump S mounted on a carriage or
waggon T, which runs on a railway or planking laid down inside the tunnel.
The water to fill the space is kept in a tubular reservoir U, jointed or
attached to the waggon T. This pipe is to be of such a length and diameter
as to contain as much water as would be sufficient to fill the space
the piston O and the plate N, when these are as far apart as it is intended to
force forward the protecting cylinder or shield at one operation, this distance
being represented in the Drawing as three feet; consequently, the water would
serve as a gauge indicating the distance the plate N had been forced forward
from the piston O. If the tunnel be built on a descent, it would be advisable
to mount the front part of the waggon T and reservoir U on higher wheels
than the hinder part, and the reverse when the tunnel is built with an ascent,
in order to keep the reservoir upon a level. Instead of filling the space Q
with water to effect the separation of the piston O and plate N, this space
might be filled with compressed air by causing the pump S to force air instead
of water through the pipe X, which it would do if the water was allowed to
run out of the reservoir U and waggon T; in this case the spaces between the
divisions g, g, might be used as magazines for storing compressed air over and
above what was required to counterbalance the effect of the external pressure,
which compressed air might always be maintained at a density sufficient to be
between

page_text: capable, when admitted (by means of a pipe provided with a cock for that
purpose) into the space between the piston O and plate N, to effect their
separation by forcing the protecting cylinder forward to the required distance.
Other fluids might be employed with like effect. I would here remark that
the pump S, whether used for forcing water or other fluid into the space Q,
might be placed further back in the tunnel or carried outside the entrance
thereof, in which case it could be worked by steam or other power, as might
be deemed most convenient and suitable; the connecting pipe X being
lengthened according to the distance of the pump from the piston O, and the
length thereof increased as this piston and the shield receded further from the
pump. Now, let us suppose that a section of the tunnel has just been com-
pleted, and that it is necessary to move forward the protecting cylinder or
shield to give room for another section to be built up; the space Q would
then be empty, or nearly so, and the piston O close to the plate N. The
pump S is then set to work, and the water or other fluid is drawn into the
barrel S and forced up the pipe X into the space between the piston O and
plate N. By this means the piston O is forced against the end of the planking
and iron casing of the fimishing part of the tunnel, and as it cannot advance
any further, and water is still being forced into the space Q, it follows that the
plate N must yield and be forced forward, and carry with it the protecting
cylinder or shield, and when the whole of the water from the reservoir U is
pumped into the space Q, the plate N, and, consequently, the whole shield, will
have been forced forward three feet, the sand or mud in front and above the
shield or front part of it having been pushed away by the plough to leave room
for the whole apparatus to advance. That part of the interior of the pro-
tecting cylinder or shield I, I, which is accessible is to be well greased each
time it has been advanced, and the piston O has been pushed forward against
the plate N, so as to allow it to slip more easily over the casing of gutta
percha or other material of which this outer casing may be formed. In the
pipe X is a three-way cock d, which, on being turned in one direction, allows
the water or other fluid to pass from the pump S to the space Q, and in the
other shuts off the communication from the pump and allows the fluid to pass
from the space Q into the waggon T through the small branch pipe k, so that
when the plate N has been moved forward the required distance, the cock dis
turned to allow the fluid to descend into the waggon T, the piston O being
pushed forward towards the plate N, so as to force all the water or other fluid
in the space through the pipe X into the waggon T and reservoir U. The
piston O might either be pushed forward by hand or by means of a screw, the
frame of which could be made to bear against the flanges of the inner casing

page_text: F, as will be easily understood. The piston O being pushed forward against
the plate N, a clear space between the face of the piston and the ends of the
cylinders forming the completed part of the tunnel will then be left for
building up a fresh portion of it as before; and when this has been completed
the shield is again forced forward by the same means; and these operations
are continued until the whole structure under water is completed. The
piston O and plate N are to have manholes at any convenient part, so as to
allow workmen to pass beyond them when requisite to examine or repair any
of the parts which cannot otherwise be got at. It will be seen that the ends
of the planks forming the two cylinders do not coincide while the building
operation proceeds, as the two thicknesses of planking advance alternately, it
will therefore be necessary before the piston is made to bear against them to
make use of temporary filling pièces Z of half the length of the planks, and
make the ends of both the plank cylinders Hush, in order to withstand the
pressure of the piston O when the water or other fluid is being forced into the
space G. The plates of iron casing F are also only to be placed temporarily
in their places until the piston has been moved forward, after which they
must be removed to complete the planking, and when this done they can be
permanently fixed. The temporary filling pieces Z are to be removed after.
the piston has been advanced, and the building up of the tunnel is to be con-
tinued with planks of the proper length, the temporary ones being laid asido
until again required, as will be the case every time the shield is moved forward.
But the necessity of using those temporary filling pieces, and of placing the
plates F provisionally, may be obviated by having rims e supported by brackets
f, as shown on one side of the horizontal section Fig. 4, projecting from the
face of the piston O as far as the joints of the cylinder D might be distant
from those of A and B, and from that of the casing F. These projecting
rims must be so formed that when the border or edge of the piston O bore
against the ends of the cylinders A and B, one part of the rim would bear
upon the ends of the cylinder D, and the other part would bear upon or
against the end of the casing F. These rims with their brackets might be
made to take off and put on as occasion required. On one side of the hori-
zontal section, Fig. 4, is shown the projecting rim e and bracket f, and on
the other, the ends of all the cylinders are brought flush by the temporary
filling pieces Z and the casing F; they are thus represented in order more
distinctly to show the two modes. Either or both of the cylinders formed of
planking may be made by placing the planks vertically instead of longitudi-
nally, in which case planks of greater length bent to the shape of the tunnel
could be placed side by side, and properly jointed where the edges or ends

page_text: meet. These planks would form so many rings or hoops. jointed together at
the edges by a rabbet, and at their ends or point of meeting by a dovetail
joint, care being taken that the vertical joints are to 'be so placed as to form
break joints with those of the other cylinder. When this mode of construct-
ing either or both of the cylinders formed of planking was adopted, the tem-
porary filling pieces before alluded to would require to be of such size only
as to make up the difference between the end of one cylinder and that of the
other, so as to bring the ends of both flush, in order to receive the bearing of.
the piston, as before described, these temporary filling pieces to be removed
after the piston has been advanced. The mode of supplying the hydraulic
power may also be varied, as shown in Fig. 5, which represents the longitu-
dinal vertical section of the shield, but with a different plan of applying the
liydraulic power. An ordinary hydraulic press, or the cylinder thereof, Y,
'might be placed horizontally in the space between the plate N and the front
part of the shield M, as shewn at Fig. 5, and securely attached to the divi-
sions 9, 9, the centre one being cut away in such a manner as to admit the
cylinder Y of the press, the plate N being firmly attached to the open end
of the cylinder of the press, and having an opening in it to allow the ram W
of the press to pass through, being also further provided with a leather
collar on the side next the cylinder, to prevent the water from escaping
therefrom. The head of the ram should be securely attached to the centre
of the piston O of the shield, so that the pressure of the water in the cylinder
exerted against the extremity of the ram would be transmitted by it to the
piston O, and from it to the ends of the cylinders forming the tunnel, the
same effects would thereby ensue, and would force the shield forward and
effect the separation required between the ends of the tunnel and the piston O;
the latter, after the removal of the hydraulic pressure, is pushed back against
the plate N, and the ram of the press is forced back into the cylinder by the
same operation. A pipe from the pump S passes through the piston O and
plate N, and conveys the water into the extremity of the cylinder of the
press. By this arrangement it would not be necessary for the piston O to be
furnished with packing. The other parts of the apparatus being the same
'as in the former arrangement, it is not necessary to exhibit them in the
Drawing.
5. I would here observe, that my improved plan of constructing tunnels, as
above described, is more particularly applicable to the beds of rivers, channels,
straits, estuaries, or other places where the bottom consists of sand, mud, or
other clayey, or gravelly, or yielding substance, which can be upheaved or
displaced by means of the protecting cylinder, shield, or plough. The tunnel

page_text: may be constructed either upon the bed of the river, channel, strait, or
estuary, in which case 'the water only would have to be displaced; or it may be
partly built in the bed thereof, or along the shores, or wholly under the same,
at such a convenient depth or distance from the water as circumstances may
determine. If built entirely or mainly on the bed of the river, strait, or
channel to be crossed, care should be taken to form the cylinders of material
sufficiently heavy, or to line the inner casing thereof with matter of sufficient
weight to give to the whole space occupied by the tunnel a greater specific
gravity than water, so that the tunnel should have no tendency to rise or
move out of its place. When built in and entirely under the material forming
the bed of the river, strait, &c., the force of the hydraulic pressure, or that
of any other fluid employed, would require to be increased in proportion to
the resistance of the superincumbent or surrounding matter through which
the shield and tunnel would have to pass, and this increase of force of
hydraulic pressure could be obtained by increasing the length of the lever
used to work the pump S, and by increasing the number of hands, or the
power used to work the same, until sufficient pressure is obtained to overcome
the resistance offered to the progress of the protecting cylinder or shield.
The necessary amount of force to be employed must of course depend upon
the circumstances of cach particular case; it would therefore be useless to
give any rule or examples beyond what has been stated, as it is entirely the
business of the engineer to determine these details. It may, however, be
proper to state, that it will be necessary to proportion the thickness or strength
of the piston O and plate N, or any other parts of the apparatus, to the pressure
they would have to sustain. I may also here remark, that as the dimensions
or proportions of the tunnel and the protecting cylinder or shield might
require to be increased or changed to suit the kind of traffic required to pass
through the tunnel when completed, such increase or change might readily
be adopted, as the surfaces on which the hydraulic or other fluid pressure
acts increase in proportion to the increase of the size or dimensions of the
tunnel and shield, consequently the increased power required to force forward
the shield would be met by a corresponding increase of surface on which the
power acts to overcome the increase of the resistance offered to the advance of
the shield. The shield being placed at a given angle when the work commences,
it may be necessary
when so much of the tunnel has been completed as to
reach the lowest point to which it is intended to go, to give to the shield and
tunnel an ascending angle, so that they may come to or near the surface
when required. For this purpose the planking at the bottom is left thinner
and that at the top is made thicker, so that a line drawn through the centre.

page_text: and extended would no longer present a descending angle as respects the
surface line of the water, but an ascending one when the requisite direction
is obtained; the planking would continue to be of equal thickness at the top
and at the bottom of the ellipsis forming the tunnel. It is also my intention
to make use of the diving bell to assist when required in giving a new
or another direction to the protecting cylinder or shield, and also in order to
ascertain the nature of the ground about and in front of the shield, or to
remove any obstruction that might present itself in the progress of the work, as
the wreck of a vessel or other obstacle. The diving bell, after being lowered down
in the water and placed above the shield, might be made to communicate there-
with and the interior of the tunnel by means of a tube or pipe proceeding from
the bell, and attached to the front part of the shield at any convenient point,
which tube extending on one side into the diving bell and on the other into.
the shield or tunnel, might be made to supply the bell with air. The tube
is to be provided with cocks or valves, so as to shut off the communication
with the shield or tunnel whenever it might be necessary to do so; the
tube projecting into the bell to be so attached to the shield as to be capable
of being easily detached, and the orifice closed in such a way as to prevent
any thing getting into the shield by its removal. I however claim no exclu-
sive right to the use of the diving bell, except in so far as it might be used
in conjunction with my improved apparatus for constructing tunnels.
Having now described my Invention, and the means of carrying the
same into effect, I would observe, in conclusion, that I do not mean to con-
fine myself to the plans shown and described for forcing forward the shield,
as this operation may doubtless be effected by other mechanical power,
although I prefer to make use of hydraulic power as the most convenient
and applicable to the circumstances of the case. That which I consider
to be new, and therefore wish to claim as my Invention, is the mode
herein shewn of building or constructing tunnels by means of a moveable
water-tight protecting cylinder or shield, with its accessories, and apparatus
for forcing the same forward, the essential feature of the arrangement
being, that such water-tight protecting cylinder or shield with the plough-
shaped part in front, may be moved or forced forward from time to time
through earth or water by hydraulic power,, or any suitable mechanical
means, so as to cause the front part of the shield to upheave and force
forward or on one side any superincumbent or surrounding sand, mud, earth,
water, or other matter that may offer resistance to its progress, and by thus
removing the opposing mud, water, or other matters, obtain room or space

page_text: within the protecting shield to build or construct a continuation of the tunnel,
without the liability or risk of danger from the entrance of the water.
In witness whereof, I, the said Samuel Dunn, have hereunto set my
hand and seal, this Twenty-sixth day of November, in the year of our
Lord One thousand eight hundred and forty-nine.
Taken and acknowledged by Samuel
Dunn (party hereto) at Paris, in
France, in the Republic of France,
the Twenty-sixth day of November,
One thousand eight hundred and
SAMUEL (L.s.) DUNN.