Improvements in and relating to Caissons and Sheet Piling for Pier Foundations and the like.
Year: 1896

page_text: Date of Application (in United Kingdom), 1st May, 1896
Complete Specification Left, 1st May, 1896-Accepted, 11th July, 1896
Improvements in and relating to Caissons and Sheet Piling for Pier
Foundations and the like.
I, WILLIAM DE HERTBURN WASHINGTON of 145 Broadway, in the City of
New York, State of New York, United States of America, Gentleman, do hereby
declare the nature of my invention, and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:-
The invention consists in a new method of sinking caissons, sheet piling and the
like, and in the apparatus used in carrying out the method. In particular it
consists in sinking a caisson, sheet piling and the like, by digging a well by water
jets at the lower edge of the casing, and sinking the casing into such well, while
its path of movement may be directed if necessary by varying the jet action at
various points, or by changing the downward pressure thereon.
Further in the construction of the shoe or point through which the water jets
are applied, and in the combination, construction and arrangement of the various
parts, all as more fully hereinafter described.
I have shown in Figs. 1, 2, 3, 4, 5, 6 and 7 my invention as applied to sinking
tubular caissons, and in Figs. 8, 9 and 10, as applied to sheeting or sheet piling.
Fig. 1 is a vertical section through a caisson particularly devised to carry out
my improvement.
Fig. 2 is a horizontal section of Fig. 1 on line xx.
Fig. 3 is a detached elevation of one of the sections of the cutting shoe with
which the lower end of the caisson is provided.
Fig. 4 is an enlarged section on line y y of Fig. 2.
Fig. 5 is a similar view as Fig. 4 of a modified form of construction.
Fig. 6 is a vertical, sectional view illustrating my method of sinking a caisson.
Fig. 7 shows different forms of interior bracing applied to the caisson.
Fig. 8 is an elevation showing my method and apparatus used in sinking sheet
piling.
Fig. 9 is an enlarged horizontal section through the meeting edges of two
sections of such sheet piling and
Fig. 10 is a vertical section through Fig. 8, showing the piling as being sunk,
1 will first describe my invention as applied to tubular caissons.
The caissons shown in the drawings are lap joint-steel cylinders built up in
sections, as shown in Fig. 1.
These caissons are of suitable diameter and length and as they are intended
simply to exclude the earth and water during excavation and filling they may be
built of thin steel plates with single rows of rivets.
The caisson is shod with a special cutting edge or shoe made of segments 6 of
b

page_text: hollow castings, provided with luga d, by means of which they are secured by
bolts e to the lower edge of the caisson which bears on the shoulder 2 formed on
top of the enating.
These shoes preferably have the tapering lower edge 4 and are provided with
suitable downwardly opening jets 5 communicating with the interior; these jeta
being suitable to cause fluid under pressure when emitted therefrom to cut or dig
a narrow well as hereinafter described.
The interior chamber 61 of the shoe connects by a suitable branch pipe e with
the water supply pipe f, extending to at or near the top. These shoes may be
fastened to the side of the edge of the caisson, as shown in Fig. 5, in which they
are shown detachably secured by means of clamping hooks 8, angle plates d' and
bolts c¹.
These castings & constructed and arranged as described form a complete shoe
around the lower edge of the enisson and to prevent any possible interval between
the section, the ends of the segments may be provided with inclined jet
apertures 6.
To sink such a caisson a pit is preferably dug by hand to the level of the
ground water and the caisson is placed in it by a steam derrick. A steam pump A
is set near the caisson which is adapted to deliver water at any desired pressure
into branches B, which connect the pump with the vertical supply pipes in the
caisson. Each of the branches consist of flexible tubing connected with the
vertical pipes through goose necks f¹ over the top of the caisson and each is
independently controlled by a valve C."
The caisson is preferably heavily weighted down as by piling pig iron upon a
platform P on top and differential hoists H are applied, preferably at four equi-
distant points hung from the timber frame across the top and hooked to an anchor
platform D, which is also provided with a load of pig iron E.
Now if water is admitted into the shoe the jets of water pouring out at a great
pressure will loosen and scour away the surrounding earth and create a narrow
well into which the caisson will sink. By the proper arrangement and working of
the hoists in connection with the manipulation of the valves which control the
access of water to the separate sections of the shoe the verticality of the caisson
can be readily maintained through the whole operation of sinking.
The jets may be maintained until the caisson reaches the solid foundation. The
water which is used for jetting out the well in which the caisson sinks is allowed to
rise around the sides of the caisson to the surface of the ground and carries up the
loosened earth dug out by the jet action, and at the same time serves to keep the
caisson out of contact with the sides of the well.
If it is desired to save water a pulsometer or other suitable pump E' is arranged
to collect it and pump it back into a settling tank F.
The caissons may be delivered in sections and after one section is sunk the next
one may be riveted on top and so on until the whole caisson is completed while
sinking it. This permits of building pier foundations where there is not enough
overhead room available to sink the whole caisson in one piece as would be the
case for instance, in erecting pier foundations in the cellar of an existing building
which is designed to receive additional stories.
The core of soil which remains in the interior of the caisson need not be removed
from the interior of the cylinder until the caisson reaches the solid foundation upon
which the pier is to be built. When the caissons are buried in solid stiff clay,
which often covers a rock surface the cutting edge will become effectually sealed
when the jet action ceases so that the interior can be excavated and the masonry
built dry by the air of moderate pumping. If necessary, or after excavating a
reasonable distance an air lock may be put in and the excavation completed that way.
With an irregular surface of rock other means may be resorted to, such as sheet
piling, but the simplest way which my method enables me to use is to seal up the
edges and bottom by pumping thin grout into the cutting edge and injecting it
through the jet holes into the cavities scoured out by the water.

page_text: When excavating of the core begins the sides of the caisson are braced to resist.
deformation by exterior pressure by the assistance of triangular frames wedged
tight. In smaller cylinders three bevel-ended struts G with interposed oak wedges
makes a suitable frame which is put as low down as practicable. Then the men
dig out under it as far as possible and set another frame a few feet below it and so
on, passing the excavated ground up through the center of the caisson. Instead of
excavating by hand however, the sand pump or dredge might be used.
For larger caissons two sets of triangular braces may be used or auxiliary
braces H, or solid plank segments 1 may be provided in the exterior space on each
side of the triangular frame, all as shown in Fig. 7.
Except where loose sand is encountered the core remaining in the caisson after
sinking is but little affected and where quicksand is present the difficulty hereto-
fore encountered in the old method by the constant inflow of the sand is entirely
avoided as the tendency of the quicksand to flow is so slow that by the rapid work
of my method the bottom can be reached, the rock cleaned, dressed a little if
necessary and closed up by concrete before it penetrates the interior.
When the excavation is completed the rock bottom is cleaned, and the bed of
cement concrete a few feet in thickness is placed thereon by building up in layers
as in the usual manner. Upon this concrete the pier is built the full size of the
caisson up to the top thereof, either solid or hollow.
It will be seen that in my method the caissons are intended to act simply as
shields and their function is accomplished as soon as the masonry inside them is
completed and their endurance therefore is immaterial, therefore they may be
built less strong and consequently cheaper than heretofore.
If the character of the soil should offer greater resistance at one point than at
another of course the jetting out would advance more rapidly at the point of lesser
resistance and. consequently cause. the. caisson to incline. By shutting off the
water from such segment or segments which are in advance and if necessary by
hauling up the weight D (by means of the hauling rope H) on the side where
increased action is needed, the action of the jets is temporarily localized' upon the
spot which has the greater resistance until the caisson straightens itself up again.
Ordinary obstructions such as roots or stones are easily cut through by the cutting
edge, or are pushed aside by it.
Where circumstances admit, the modified construction of the shoe shown in
Fig. 5 may be used and after completion of the sinking of the caisson it may be
removed and used again.
Although I have described my inve...on as applied for building pier foundations,
I have done so merely for the purpose of illustrating it as its scope is much
broader and those skilled in the art will readily perceive its application to other
engineering problems, as in constructing coffer dams, light houses, bridges, air
shafts, tunnels and the like, or for constructing cisterns, storage tanks, deep
wells etc.
My method and apparatus opens the way to sink caissons to much greater depth
than has been practicable heretofore, as in my method the skin friction of the
caisson, that is its frictional contact with the ground is done away with as the
water is directed upwardly both inside and outside and forms a quasi lubricant
between the ground and the walls of the caisson. In sinking to such great depth
where the upward flow of water might be liable to become obstructed, or if on
account of loose soil it might find other outlets, supplementary jets could be readily
attached around the walls of the caisson, inside or outside or both, at suitable
intervals in sinking. Thus after sinking about fifty feet a shoe of the character
shown in Fig. 5 can be fastened to the inside and a similar one (beveled reversely)
to the outside and the sinking proceeded with by the additional use of the
supplementary jets if required.
My method may be used in sinking caissons in water as well as on dry land, and
the sand pump may be used to clean out the soil within the caisson down to "hard
pan" either during the process of sinking or after it is completed, while it is still

page_text: filled with water and by using concrete as the material for filling its interior the
bracing of the caisson would not be required.
The caissons of course may be cylindrical, rectangular or of any other desired
cross-section, and may be built of wood, cast iron, steel or any other available
material and provided with a shoe adapted to it or formed integrally with it, and
the strength of the caisson may be made such as to support the load directly upon
it without recourse to an inside pier. The use of compressed air or steam as an
.available substitute for water for jetting out the soil obviously suggests itself.
In sinking sheet-piling, as shown in Figs. 8, 9, and 10, the shoe as described is
applied to the lower edge of a sheeting section Z, and sunk in the manner
described, the well being simply straight instead of annular.
The next section Z' is then sunk at its edge, being guided thereon in any suitable
manuer, such as by forming a guide groove between the plates W, secured on each
-side of the edge of the section first sunk.
The weighting of these piling sections may be done as described for the caisson,
or the weights may be supported on saddles W₁ as shown in Fig. 8.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :
1. The herein described method of sinking caissons.
.2. The apparatus herein described for use in sinking caissons.
Dated this 4th day of April 1806
WILLIAM DE HERTBURN WASHINGTON.
Haseltine, Lake & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.