Improvements in Tunnelling and Tunnelling Apparatus.
Year: 1896

page_text: Date of Application, 9th Jan., 1896
Complete Specification Left, 8th Oct., 1896-Accepted, 5th Dec., 1896
Improvements in Tunnelling and Tunnelling Apparatus.
I, HARLEY HUGH DALRYMPLE-HAY, of 20 Victoria Street, Westminster, in
the County of Middlesex, Civil Engineer, do hereby declare the nature of this
invention to be as follows:-
The object of my invention is more especially to facilitate tunuelling in ballast
and loose strata.
I employ, as is now often done, a shield of cylindrical form with a cutting edge
in front and a diaphragm in which however there is a doorway closing the shield
across.
When tunnelling under or close to important buildings, sewers, gas and water
pipes &c. it is important to do so with as little subsidence as possible. The method
usually adopted when constructing iron tunnels is to excavate in front of the shield,
and timber the face and roof, and having made this secure, to move the shield
forward and erect a ring of tunnel under cover of the shield at its tail end.
Compressed air is used where necessary to exclude water.
Now according to my invention I provide a hood to form a roof above, and in
front of the shield so as to avoid timbering and in front of the hood at its cutting
edge I place well tempered clay so that it is possible to force the hood into it.
The hood may be regarded as a prolongation of the upper part of the shield, it
forms an arch, extending say 60 degrees on either side of the centre line of the roof.
The hood is attached to the shield by brackets and it may for so far as it extends
replace the cutting edge of the shield.
The method of use is as follows:-The apparatus being in place, preparation is
made for the advance of the hood by scooping out a pocket a few inches in width
and not very deep in front of and above the cutting edge of the hood say at the
highest point. Immediately this hole or pocket is produced it is filled with
tempered clay; the object being to keep the loose material in place and if
working under air pressure to prevent the escape of air from the tunnel into
the loose material. When one pocket has been formed and filled another is
made alongside of it, and so on, pocket after pocket being made and filled until
in the end a long groove is formed and every part of the cutting edge of the hood
has in front of and above it the clay which the groove contains. When all is
ready the shield together with the hood are forced forward by the rams, the clay
yielding easily to the advance of the hood. It will be seen that under cover of
the hood timbering is not required to support the roof; hence a considerable
money saving and besides the work is better done and with less risk of
settlements.
Dated this 8th day of January 1896.
HARLEY H. DALRYMPLE-HAY.

page_text: I, HARLEY HUGH DALRYMPLE-HAY, of 20 Victoria Street, Westminster, in
the County of Middlesex, Civil Engineer, do hereby declare the nature of this
invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:-
The object of my invention is more especially to facilitate tunnelling in ballast
and loose strata.
I employ, as is now often done, a shield of cylindrical form with a cutting edge
in front and a diaphragm in which however there is a doorway closing the shield
across.
When tunnelling under or close to important buildings, sewers, gas and water
pipes &c. it is important to do so with as little subsidence as possible. The
method usually adopted when constructing iron tunnels is to excavate in front
of the shield and timber the face and roof, and having made this secure, to
move the shield forward and erect a ring of tunnel under cover of the shield at
its tail end. Compressed air is used where necessary to exclude water.
Now according to my invention I provide a hood to form a roof at the front of
the shield so as to avoid timbering. In front of the hood at its cutting edge
I place well tempered clay so that it is possible to force the hood into it. The
hood may be regarded as a prolongation of the upper part of the shield, it forms
an arch, extending on either side of the centre line of the roof. The hood may
for so far as it extends replace the cutting edge of the shield.
The method of use is as follows:-The apparatus being in place, preparation is
made for the advance of the hood by scooping out a pocket a few inches in width
and not very deep in front of and above the cutting edge of the hood say at the
highest point. Immediately this hole or pocket is produced it is filled with
tempered clay; the object being to keep the loose material in place and if
working under air pressure to prevent the escape of air from the tunnel into
the loose material. When one pocket has been formed and filled another is made
alongside of it, and so on, pocket after pocket being made aud filled until in the
end a long groove is formed and every part of the cutting edge of the hood has in
front of and above it the clay which the groove contains. When all is ready
the shield together with the hood are forced forward by the rams, the clay
yielding easily to the advance of the hood. It will be seen that under cover
of the hood timbering is not required to support the roof; hence a considerable
money saving and besides the work is better done and with less risk of
settlements.
The annexed drawing shows tunnelling apparatus in accordance with my
invention. Figure 1 is a front elevation and Figure 2 is a longitudinal section.
The shield here shown is adapted for tunnelling in ballast, a material which
allows both water and air to permeate through it freely. The hood with which
this shield is provided is formed integral with it but a shield of the ordinary
description may in like manner have a hood fixed upon it. A is a strong ring
girder having in the central space a diaphragm B and a doorway C. D is the
hood fixed upon the exterior of the ring girder and projecting in advance of it for
the greater part of its circumference but at the lower part the hood projects
only just so far as to provide a cutting edge E in the ordinary position. The
leading edge of the hood also has a cutting edge D'. The hood is strengthened at
the upper part by a lining plate and also by means of brackets to prevent it yielding
inwards to the pressure to which it may be exposed. To the hinder part of the

page_text: ring girder A a stout casing or cylinder F is fixed and this forms the tail of the
shield as is usual. Within it are arranged the hydraulic cylinders G G for forcing
the shield forward. They abut upon the ring girder and their rams thrust against
the permanent lining sections H H of the tunnel. At. I is one of the holes
excavated by the workmen in advance of the cutting edge of the hood and at.
once filled with clay as before stated. The hood as will be seen forms an advanced
roof under shelter of which the workmen are able to excavate and form there holes
in advance of the excavation of the lower part and the crown and side walls of the
excavation are supported by it without need for any timbering. On the shield
being thrust forward after the claying operation is completed, the edge of the hood
penetrates readily into the soft material and the clay fills all the crevices outside
the shield thereby serving not only to prevent any movement of the soil but also
to render it airtight preventing loss of air if the work is carried on with air under
pressure as will usually be the case. The small space which is left as the tail F of
the shield passes forward over the lining rings H of the tunnel is at once filled in
by injecting grout in a well known manner.
The hood may extend round a larger or smaller portion of the circumference of
the shield but the upper part is principally of importance. In my
In my Provisional
Specification I suggested that the hood should extend 60 degrees on either side of
the central line, but I now prefer that it should extend over a greater portion of
the circumference as the drawing shows. The face of the work is supported by
timbering, in the usual manner and is shored up from the lining H of the tunnel
by raking shores passing through the doorway C. None of the timber employed
in constructing tunnels according to my invention is left in the work which is not
only a saving of expense but risk of settlement from the perishing of the timber is
avoided.
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. A shield substantially as described furnished with a hood projecting from its
upper part in advance of the lower part.
2. The method of tunnelling or making tunnels substantially as described
consisting in excavating under cover of a shield, holes in advance of the cutting
edge, and in filling these holes with clay and advancing the shield so that the edge
penetrates into this soft impermeable material.
Dated this 2nd day of October 1896.
HARLEY H. DALRYMPLE-HAY.