GB2404410A

GB2404410A - Membrane lined piles

Info

Publication number: GB2404410A
Application number: GB0409515A
Authority: GB
Inventors: Arwel Williams
Original assignee: Pennine Holdings Ltd
Current assignee: Pennine Holdings Ltd
Priority date: 2003-07-26
Filing date: 2004-04-29
Publication date: 2005-02-02
Also published as: GB0409515D0; GB0317572D0

Abstract

A method of constructing piles / columns (18) involves inserting a tubular tool (15) into the ground (10) to a predetermined depth. A sock (17) of a material impervious to a potentially contaminant ground substance is introduced into the tool (15) and filled with concrete (18). The tool (15) is subsequently withdrawn leaving the sock (17) and the concrete column in place. Closable flaps (16) or a disposable tip at the leading end of the tool (15) permit its removal from around the pile (18).

Description

1 2404410

MEMBRANE-LINED SUBTERRANEAN COLUMNS

THIS INVENTION concerns a method of constructing subterranean ground improving columns such that, in situ, they shall be protected from ground contamination.

In many instances where ground improving or strengthening columns are to be introduced, sometimes to a depth of 10 metres or so they may encounter, at a certain depth, ground substances which could migrate into the column material thus contaminating and compromising the integrity thereof.

In other instances, the depth of such a column may be such that its lower region would encounter an aquifer which again could cause deterioration of the lower end of the column thus weakening the same.

An object of the present invention is to provide a method of constructing a subterranean ground improving column such that contamination or deterioration is avoided.

According to the present invention there is provided a method of constructing a subterranean ground improving column, comprising the steps of inserting a tubular tool into the ground to a predetermined depth, introducing into the tool a sock of a material impervious to a potentially contaminant ground substance, filling the sock with a ground improving material, and withdrawing the tubular tool to leave the column, enveloped by the sock, in place.

The sock may be introduced into the tool after insertion of the tool.

The tubular tool may be introduced into the ground by applying downwards pressure, and vibration or rotation, or it may be driven vertically into the ground to the desired depth by repeated impact.

The tubular tool may have closable flaps at its leading end which are opened to allow the tool to be withdrawn.

The tubular tool may have a disposable tip at its leading end, the tip being allowed to detach itself as the tool is withdrawn from the ground.

The tubular tool may be vibrated during withdrawal thus to assist in compacting the material and preventing coincident withdrawal of the column.

The ground improving material may be a granular material.

The granular material may be sand andlor gravel.

The ground improving material may be concrete.

The ground improving material may be a mixture of bentonite and clay.

Further according to the invention, there is provided a ground improving column constructed by the aforesaid method.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a diagrammatic cross sectional subterranean view showing a ground improving column constructed in accordance with the invention, prior to withdrawal of a tubular tool previously inserted into the ground prior to establishment of the column; and Fig. 2 is a similar view showing the column in place after withdrawal of the tool.

Referring now to the drawings, in a typical situation the ground may comprise several layers including an upper layer 10, a contaminated layer 11, a lower layer 12 and an aquifer or other ground water forming a layer 13.

In a typical location it may be required to construct a subterranean ground improving column to a depth of 10 metres from the ground surface 14.

In accordance with the invention a tubular tool 15, preferably of steel, which may have closable flaps 16 in its lower most region is driven vertically with or without vibration, or angered into the ground to the desired depth. Before or after the tool is inserted into the ground it is lined with a sock 17 having a closed lower end and of a material such as polypropylene or polyethylene, and of a depth somewhat greater than that of the tool 15.

With the tool and sock fully inserted, the sock is filled with a ground improving material 18 such as a granular material which may be sand and/or gravel, or concrete, or a mixture of bentanite and clay. Such materials serve to strengthen the ground for subsequent construction of structures above ground level.

After filling of the sock 17, the tool 15 is then withdrawn leaving the column, enveloped by the sock, in place as a finished column.

During withdrawal of the tool 15 the closable flaps 16 are opened or in the case of a tool having a disposable tip, the tip is simply allowed to detach itself from the tubular wall of the tool.

During withdrawal of the tool the wall thereof may be vibrated to assist withdrawal and avoid any tendency for the column to rise coincidentally, and also to assist compaction of the column material 18.

Fig. 2 illustrates the finished column and it can be seen that the column material 18 is isolated from the contaminant layer and any underground water.

The wall of the tool 15 is preferably of steel but in some cases where the ground is particularly soft, a tool of rigid plastics may be used.

The material of the sock 17 will be selected to be impervious to whatever contaminant materials are known to exist below ground.

Although the sock 17 is preferably of a flexible material, alternatively it may be a semi rigid-walled containment thus to be more readily insertable into the tool 15 after it has been introduced into the ground.

In the case of particularly hard ground materials it might be necessary to make an initial narrow-diameter bore in advance of introduction of the tool 15.

Claims

1. A method of constructing a subterranean ground improving column comprising the steps of inserting a tubular tool into the ground to a predetermined depth, introducing into the tool a sock of a material impervious to a potentially contaminant ground substance, filling the sock with a ground improving material, and withdrawing the tubular tool to leave the column, enveloped by the sock, in place.

2. A method according to claim 1 wherein the sock is introduced into the tool after insertion of the tool.

3. A method according to claim 1 or claim 2 wherein the tool is introduced into the ground by applying downward pressure, and vibration or rotation.

4. A method according to claim 1 or claim 2 wherein the tool is driven vertically into the ground to the desired depth, by rotation.

5. A method according to any one of claims 1 to 4 wherein the tool has closable flaps at its leading end which are opened to allow the tool to be withdrawn.

6. A method according to any one of claims 1 to 4 wherein the tool has a disposable tip at its leading end, the tip being allowed to detach itself as the tool is withdrawn from the ground.

7. A method according to any preceding claim wherein the tool is vibrated during withdrawal thus to assist in compacting the material and preventing coincident withdrawal of the column.

8. A method according to any preceding claim wherein the ground improving material is a granular material.

9. A method according to claim 8 wherein the granular material is sand and/or gravel.

10. A method according to any one of claims 1 to 7 wherein the ground improving material is concrete.

A method according to any one of claims 1 to 7 wherein the ground improving material is a mixture of bentonite and clay.

12. A ground improving column constructed by the method of any one of claims 1 to 1 1.