GB2055932A

GB2055932A - In situ pile construction

Info

Publication number: GB2055932A
Application number: GB8023589A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-07-20
Filing date: 1980-07-18
Publication date: 1981-03-11
Also published as: GB2055932B

Abstract

A hole is formed in the subsoil by allowing an elongate self-propelled soil displacing mole to descent through the subsoil, the mole drawing down with itself a tubular member to line the hole. The mole is withdrawn up through the bore of the tubular member and the lined hole filled with concrete. The mole descends within the filled lined hole to produce a pile footing, the mole is again withdrawn, and the hole is refilled with concrete and allowed to set to form an in situ cased pile with an integral footing.

Description

SPECIFICATION In situ pile construction This invention relates to in situ pile construction, and in particular to improvements in the methods of our co-pending British Patent Application No. 7916657, the disclosure of which is incorporated herein by reference.

Claim 1 of our above Application No. 7916657 recites a method of constructing a pile in situ comprising: forming a hole in the subsoil by allowing an elongate self-propelled soil displacing mole to descend through the subsoil; withdrawing the mole; filling the hole with concrete; allowing such mole to descend within the filled hole before the concrete sets to produce a pile footing and to displace concrete into the hole wall; withdrawing such mole; and refilling the hole with concrete and allowing the concrete to set to form an in situ pile with an integral footing.

In one aspect of the present invention there is provided a method of constructing a pile in situ comprising: forming a hole in the subsoil by allowing an elongate self-propelled soil displacing mole to descend through the subsoil; said mole being partially received within and drawing down with itself a tubular member of internal diameter larger than the external diameter of the mole whereby to line the hole; withdrawing the mole up through the bore of the tubular member; filling the lined hole with concrete; allowing such mole to descend within the filled lined hole before the concrete sets to produce a pile footing and to displace concrete from the bottom of the hole up outside the tubular member into the actual hole wall; withdrawing such mole; and refilling the hole with concrete and allowing the concrete to set to form an in situ cased pile with an integral footing.

The tubular member is conveniently a UPVC pipe.

In one embodiment the mole has a draw cable attached to its rear end, for example by means of an attached sleeve member secured as by threading to the rear end of the mole. The draw cable and an air line to the mole (which is pneumatically operated) are threaded through a length of UPVC pipe of internal diameter slightly larger than the outside diameter of the mole. A cable clamp is secured to the rear end of the pipe and the draw cable clamped thereto at a point such that, with a taut cable, about one-half the length or rather less of the rearward portion of the mole is received within the pipe. The mole is then introduced to the location where a pipe hole is required and operated to descend through the subsoil, thus also drawing the pipe down the hole.

At a suitable depth the cable clamp is released and the mole withdrawn by hauling it up through the bore of the tubular member, preferably bt means of the same draw cable. The tubular member remains in the hole thereby preventing any inward collapse of the walls of the hole which may tend to occur in certain subsoil conditions, for example peaty or clay subsoils. Moreover in certain subsoils, such as clay, the mole can fit an unlined hole so tightly as to tend to create a vacuum below it as it is withdrawn, thus increasing the risk of hole wall collapse. The lining of a hole by a method according to this invention avoids this difficulty.

The lined hole is subsequently filled with concrete, the mole is allowed to descend within the filled hole before the concrete sets to produce a pile footing and to displace concrete from the bottom of the hole up outside the pipe into the actual hole wall and the mole is again withdrawn.

The hole is then refilled with concrete and allowed to set to form an in situ cased pile with an integral footing. A further advantage of a cased pile is that the pipe protects the concrete from corrosion attacks by substances in the subsoil. A still further advantage over the method described in relation to Figure 4 of our prior Patent Application No.

7916657 is that it avoids the step of having to extract the tubular member 32 and expander 29.

In a modification of this embodiment successive steel extension pipes are joined end to end and to the rear of the mole as the mole descends, the extension pipes being of the same outside diameter as the mole. The extension pipes are threaded onto the draw cable and air supply line before work commences, within the tubular member. The extension pipes provide substantial internal support for the relatively weak thin-walled UPVC pipe as it is drawn down by the mole into the hole.

1. A method of constructing a pile in situ comprising: forming a hole in the subsoil by allowing an elongate self-propelled soil displacing mole to descend through the subsoil; said mole being partially received within and drawing down with itself a tubular member of internal diameter larger than the external diameter of the mole whereby to line the hole; withdrawing the mole up through the bore of the tubular member; filling the lined hole with concrete; allowing such mole to descend within the filled lined hole before the concrete sets to produce a pile footing and to displace concrete from the bottom of the hole up outside the tubular member into the actual hole wall; withdrawing such mole; and refilling the hole with concrete and allowing the concrete to set to form an in situ cased pile with an integral footing.

2. A method as claimed in claim 1 wherein said tubular member is a plastics material pipe.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION In situ pile construction This invention relates to in situ pile construction, and in particular to improvements in the methods of our co-pending British Patent Application No. 7916657, the disclosure of which is incorporated herein by reference. Claim 1 of our above Application No. 7916657 recites a method of constructing a pile in situ comprising: forming a hole in the subsoil by allowing an elongate self-propelled soil displacing mole to descend through the subsoil; withdrawing the mole; filling the hole with concrete; allowing such mole to descend within the filled hole before the concrete sets to produce a pile footing and to displace concrete into the hole wall; withdrawing such mole; and refilling the hole with concrete and allowing the concrete to set to form an in situ pile with an integral footing. In one aspect of the present invention there is provided a method of constructing a pile in situ comprising: forming a hole in the subsoil by allowing an elongate self-propelled soil displacing mole to descend through the subsoil; said mole being partially received within and drawing down with itself a tubular member of internal diameter larger than the external diameter of the mole whereby to line the hole; withdrawing the mole up through the bore of the tubular member; filling the lined hole with concrete; allowing such mole to descend within the filled lined hole before the concrete sets to produce a pile footing and to displace concrete from the bottom of the hole up outside the tubular member into the actual hole wall; withdrawing such mole; and refilling the hole with concrete and allowing the concrete to set to form an in situ cased pile with an integral footing. The tubular member is conveniently a UPVC pipe. In one embodiment the mole has a draw cable attached to its rear end, for example by means of an attached sleeve member secured as by threading to the rear end of the mole. The draw cable and an air line to the mole (which is pneumatically operated) are threaded through a length of UPVC pipe of internal diameter slightly larger than the outside diameter of the mole. A cable clamp is secured to the rear end of the pipe and the draw cable clamped thereto at a point such that, with a taut cable, about one-half the length or rather less of the rearward portion of the mole is received within the pipe. The mole is then introduced to the location where a pipe hole is required and operated to descend through the subsoil, thus also drawing the pipe down the hole. At a suitable depth the cable clamp is released and the mole withdrawn by hauling it up through the bore of the tubular member, preferably bt means of the same draw cable. The tubular member remains in the hole thereby preventing any inward collapse of the walls of the hole which may tend to occur in certain subsoil conditions, for example peaty or clay subsoils. Moreover in certain subsoils, such as clay, the mole can fit an unlined hole so tightly as to tend to create a vacuum below it as it is withdrawn, thus increasing the risk of hole wall collapse. The lining of a hole by a method according to this invention avoids this difficulty. The lined hole is subsequently filled with concrete, the mole is allowed to descend within the filled hole before the concrete sets to produce a pile footing and to displace concrete from the bottom of the hole up outside the pipe into the actual hole wall and the mole is again withdrawn. The hole is then refilled with concrete and allowed to set to form an in situ cased pile with an integral footing. A further advantage of a cased pile is that the pipe protects the concrete from corrosion attacks by substances in the subsoil. A still further advantage over the method described in relation to Figure 4 of our prior Patent Application No. 7916657 is that it avoids the step of having to extract the tubular member 32 and expander 29. In a modification of this embodiment successive steel extension pipes are joined end to end and to the rear of the mole as the mole descends, the extension pipes being of the same outside diameter as the mole. The extension pipes are threaded onto the draw cable and air supply line before work commences, within the tubular member. The extension pipes provide substantial internal support for the relatively weak thin-walled UPVC pipe as it is drawn down by the mole into the hole. CLAIMS

3. A method as claimed in claim 1 or claim 2 wherein said mole has a draw cable attached to its rear end, and wherein prior to forming the hole the cable is threaded through the tubular member and clamped to the far end of the tubular member.

4. A method as claimed in claim 3 wherein said steps of withdrawing the mole are effected by means of said draw cable after releasing the draw cable from the end of the tubular member.

5. A method as claimed in any one of claims 1 to 4 in which successive steel extension pipes are joined end to end and to the rear of the mole as the mole descends, the extension pipes being of substantially the same outside diameter as the mole so as to provide internal support for said tubular member as the tubular member is drawn down by the mole into the hole.

6. An in situ cased pile when constructed in accordance with a method as claimed in any one of claims 1 to 5.