GB2202566A - Sheet piling - Google Patents

Abstract

Sheet piling (1) provided with a pair of transverse plates (2) positioned on mutually opposing faces near each pile toe to create voids behind the plates during pile penetration into the ground. A fluid material in the form of a slurry is delivered through pipes (4) attached longitudinally to the piles, to the voids so created, thereby to reduce friction at the pile/ground interface during a pile driving operation. <IMAGE>

Description

"Sheet Piling" FIELD OF THE INVENTION The present invention relates to sheet piling and to means for reducing the friction between the sheet piling and the ground during a pile driving operation.

BACKGROUND OF THE INVENTION It is common knowledge that when installing sheet piles by conventional methods, the resistance increases as the pile penetrates the ground due to the increased area of friction at the pile/soil interface.

This problem can become so severe that either heavier piles are necessary to prevent deformation during driving, or penetration becomes impossible therefore requiring re-design of the pile driving support system.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the driving friction between piles and ground during a pile driving operation, and therefore eliminate the problems referred to above.

According to one aspect of the invention there is provided a sheet pile comprising one or more thickened portions of the pile along the length of the pile for creating trailing voids in the gound as the pile penetrates the ground, and means for introducing a fluid medium into the voids during the operation thereby to reduce friction between the pile and the ground.

In a preferred form, the thickened portions are formed by mutually opposed side plates attached to the pile in order to create the subsequent voids as the pile penetrates the ground.

Advantageously, the means for introducing the fluid medium behind the transverse plate or plates and into the voids are delivery pipes attached lengthwise of the piles.

The consistency of the fluid medium delivered through the pipes may be varied to suit soil conditions. Bentonite may be used as a fluid medium in the form of a slurry.

Other features and advantages of the present invention will become apparent to the skilled reader from the following description of a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiment of the invention will be described with reference to the accompanying drawings wherein: Figure 1 is a plan view of a sheet piling system using the present invention and Figure 2 is a side view of a sheet piling system as shown in Figure 1.

BEST MODES OF CARRYING OUT THE INVENTION The sheet piling system shown in the drawings comprises a series of sheet piles 1 arranged in interlocking assembly to be driven into the ground G as in a normal pile driving operation.

Each pile 1, is provided with a thickened end portion P near its toe T and spaced a distance D therefrom.

The distance D will vary depending on design requirements.

The thickened portion P is in the form of a pair of transverse plates 2 on mutually opposing faces of the pile 1, the plate on the converse face C stopping short of the pile interlocking channels 3 as shown.

Pipes 4 are attached along the lengths of each sheet pile 1 for delivering a fluid medium above the plates 2 in relation to the direction of movement of the sheet piles 1 into the ground. The pipes 4 stop just short of the plates 2 as shown.

The number of pipes 4, the size of the plates 2, and all other physical parameters, may be varied in accordance with each job site requirement.

During a pile driving operation, the thickened portion P provided by plates 2 acts to create trailing voids in the ground as the pile is driven into the ground G.

To reduce the increasing friction between the pile faces and the ground as driving continues, a fluid medium such as a bentonite slurry is delivered through the pipes 4 which introduces the slurry into the voids behind the plates 2.

Injection of slurry material in this fashion enables the piles to penetrate the ground much more easily as compared with previous methods, since friction between the pile/ground interface is much reduced under the "lubri cawing action of the slurry, the introduction of which is made possible by reason of the presence of the voids in the receiving ground formed by the plates 2 pushing through it.

The introduction of the bentonite slurry between the sheet piling and surrounding earth provides further advantages, particularly in relation to cofferdams.

In this connection instability in a cofferdam structure can be introduced by the "piping" or "boiling" of the sub-soil around the grounded piles caused by seepage of ground water between the pile interlocks.

The bentonite slurry acting as an impervious layer, restricts this seepage in a simple yet very effective way, and eliminates the instability problem referred to above.

Bentonite is a preferred slurry but other materials capable of forming the impervious layer would be just as effective.

In the earlier part of this disclosure the slurry material, acting as a friction reducing agent, was introduced through piping into voids surrounding the piles and created by the piles themselves when being driven into the ground.

This method of slurry injection to provide the impervious layer is only a preferred method and other methods may be envisaged and contemplated.

Accordingly a method is provided for forming a structure from sheet piles comprising driving the piles into the ground, and forming an impervious layer of material between the pile interlocks and surrounding earth to prevent water seepage therebetween acting to reduce the stability of the structure.

The material forming the impervious layer may be injected continuously around the interlocks while the piles are being driven into the ground.

For this purpose voids are deliberately formed in the surrounding earth by the means discussed earlier in this disclosure, and the slurry material, in the form of bentonite slurry, injected into these voids through the agency of pipes attached lengthwise of the individual sheet piles. The slurry material therefore acts both to reduce frictional resistance as between the piles and ground as they are being driven and therefore, subsequent to installation, to provide the impervious layer acting as a resistant barrier to seepage of ground water through the pile interlocks.

Claims (8)

1. A sheet pile comprising one or more thickened portions of the pile arranged along the length of the pile for creating trailing voids in the ground as the pile penetrates the ground, and means for introducing a fluid medium into the voids during the operation thereby to reduce friction between the pile and the ground.

2. A sheet pile as claimed in claim 1 wherein said introducing means is in the form of one or more pipes attached longitu dinally of the pile.

3. A sheet pile as claimed in claim 1 or 2 wherein a said one thickened portion is formed by a transverse plate provided on mutually opposed faces of the pile and positioned near the pile toe.

4. A sheet pile as claimed in any preceding claim wherein the fluid medium is bentonite slurry.

5. A method of sheet piling comprising producing a void around the sheet piles at one or more selected positions along the piles as the piles penetrate the ground, and delivering a fluid medium to the voids thereby to reduce friction between the piles and the ground during a pile during operation.

6. A method as claimed in claim 5 wherein said fluid medium is bentonite slurry.

7. A sheet pile substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

8. A method of sheet piling substantially as hereinbefore described with reference to the accompanying drawings.