GB2170527A

GB2170527A - Underpinning existing buildings with piles

Info

Publication number: GB2170527A
Application number: GB08602252A
Authority: GB
Inventors: Roger Alfred Bullivant
Original assignee: Roxbury Ltd
Current assignee: Roxbury Ltd
Priority date: 1985-02-02
Filing date: 1986-01-30
Publication date: 1986-08-06
Also published as: GB2170527B; GB8602252D0

Abstract

A method of supporting a building structure on cased piles comprises driving a pile casing 14 to a desired depth, cutting off the upper end of the pile 16 at a predetermined level below the lower surface of the structure 10, 12, 18, to be supported by a suitable cutting tool inserted down the casing from above, and filling the casing and the voids above it with concrete suitably reinforced, if necessary. <IMAGE>

Description

SPECIFICATION Improvements in or relating to piles The present invention concerns improvements in or relating to piles.

In one well known form of piling a hollowtubular pile casing is driven into position beneath a structure to be supported, by any suitable method, for exam ple top or bottom driving. Normally the pile is provided in a plurality of sections which, on fitment, are interconnected to provide the pile casing. In most instances a pile is driven until its tip reaches a rigid stratum or until the frictional forces on its side are sufficiently great to support the load intended to be held by the pile. This means that when using pile casing sections in predetermined lengths there is no guarantee that the uppermost pile casing section of the completed pile lies with its open top at the desired position.This desired position is just beneath the structure to be supported so that when concrete is poured into the pile casing to complete the pile, not only can the concrete fill the hole through the structure through which the pile casing has been driven but also it can extrude into the small space between the top of the pile and the base of the structure to be supported to increase the reaction between the pile top and the structure.

It is an object of the present invention to obviate or mitigate this problem.

According to the present invention there is provided a method of supporting a structure comprising driving a pile casing through a hole in a structure to be supported until the leading end of the pile casing reaches its desired position and thereafter introducing a cutter into the top of the pile casing, positioning a cutting element of said cutter at a location at or near the lower surface of the structure to be supported, actuating the cutter to part off the pile above said location so that said unwanted top portion of the pile can then be removed and introducing concrete into the pile casing and hole through the structure.

Preferably the cutting may be carried out by a rotary mechanical cutter having a cutting blade.

Alternatively the cutter may be a spark eroder, a gas flame, a hot wire cutter, an explosive cutter, or an expanding jaws cutter.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawing, which shows diagrammatically a cross-sectlon through a foundation of a building to be supported by a pile and the upper section of a pile casing of the pile for supporting the building.

A building comprises an external wall 10 carried by a concrete foundation 12. The building in this embodiment is an existing or new building which as to be supported by at least one pile 14 driven through a hole 16 which is normally cut through the foundation 12 by a rotary percussive drill at an angle close to the vertical. During the drilling of the hole 16 careful note is made of the depth of the foundation at that particular point, that is the length of the drill which has penetrated the foundation 12 when it breaks through the lower surface of the foundation.

The pile is then formed by driving steel tubular pile casing sections through the passage 16 either by a top driving technique to that the pile sections are driven one by one from alongside the wall 10 or by a bottom driving technique where a pneumatic mole is fitted to the lowermost section of the pile and drags subsequent pile sections 14 attached to it down the hole. Whatever pile driving technique is employed it is terminated when the pile casing reaches its desired position, for example when the base of the lowermost pile section abuts a base rock or alternatively when the forces of friction on the pile casings are equal to or greater than the calculated load to be supported by the pile.It will be realised that as the pile casing comprises a number of longitudinally interconnected equal length sections when it assumes its final position the top end of the uppermost section will probably not occupy the desired position, that is just below the lowermost surface 18 of the foundation 12. In the embodiment illustrated the uppermost pile casing section terminates above the upper face 20 of the foundation 12.

To ensure that the uppermost end of the final pile casing occupies the optimum desired position X illustrated in the drawing, that is just below the lower face of the foundation 12, when driving has ceased careful measurement of the length of pile casing projecting above the upper face 20 of the foundation 12 is taken and this, together with the reading taken during the drilling operation, is used to determine what length of casing has to be parted off from the end of the positioned casing so that the upper end of the final casing is at the position X. Thereafter an internal cutting machine is fitted into the interior of the pile casing and when the cutting arrangement of the machine is arranged alongside the position X it is actuated to part off the upper section 22 of the casing.The excess section 22 can then be pulled out of the passage 16 and the pile can be filled with concrete in the normal way after inserting reinforcement, if desired, further concrete being poured after the pile has been filled such that it fills also the passage 16 and those regions in the area of position X on the underside of the foundation 12 into which it can penetrate.

Various modifications can be made without departing from the scope of the invention, for example a single length of pile casing can be utilised, if appropriate, rather than a sectional pile casing. The pile casing may be formed from plastics material.

The cutting means employed for parting off the unwanted upper end of the pile casing may be mechanical means involving a rotary cutting blade, rotary spark erosion means or flame cutting means.

Especially in the case of plastics piles it may also comprise a hot wire cutter, an explosive cutter or an expanding jaw or collet cutter. The concrete can be poured at atmospheric pressure but preferably is inserted into the pile casing 14 and the passage 16 under pressure. In a further modification, the location of position X may be varied as desired, for example it may be anywhere within the passage 16.

It will be realised also that the present invention can be readily utilised when piling a new building having pile holes cut or preformed in the foundation or through the floor slab.

Claims

1. A method of supporting a structure compris- ing driving a pile casing through a hole in a structure to be supported until the leading end of the pile casing reaches its desired position and thereafter introducing a cutter into the top of the pile casing, positioning a cutting element of said cutter at a location at or near the lower surface of the structure to be supported, actuating the cutter to part off the pile above said location so that said unwanted top portion of the pile can then be removed and introducing concrete into the pile casing and hole through the structure.

2. A method as claimed in claim 1, in which the cutting may be carried out by a rotary mechanical cutter having a cutting blade.

3. A method as claimed in claim 1, in which the - cutting may be carried out by a rotary spark eroder.

4. A method as claimed in claim 1, in which the cutting may be carried out by a rotary flame cutter.

5. A method as claimed in claim 1, in which the cutting may be carried out by a hot wire cutter.

6. A method as claimed in claim 1, in which the cutting may be carried out by an explosive cutter.

7. A method as claimed in claim 1, in which the cutting may be carried out by an expanding jaw cutter.

8. A method of supporting a structure substantially as hereinbefore described with reference to the accompanying drawing.

9. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.