GB2450339A

GB2450339A - Removing hollow piles from the ground using fluid pressure

Info

Publication number: GB2450339A
Application number: GB0711857A
Authority: GB
Inventors: Derek A Kent
Original assignee: Edmund Nuttall Ltd
Current assignee: BAM Nuttall Ltd
Priority date: 2007-06-19
Filing date: 2007-06-19
Publication date: 2008-12-24
Also published as: GB0711857D0

Abstract

Removal hollow pile from ground, the pile 1 is closed at its top end using a closure member 4 and pressurised fluid is delivered by a pressurising system 8 and a feed device 5 to the interior of the pile 1, the pressure driving the pile 1 from the ground. The pressure of the fluid can be varied with a higher pressure being first applied to loosen the pile 1 from the surrounding ground and then a lower second pressure applied to maintain movement of the pile 1 out of the ground. While the pile 1 is being driven from the ground, the weight can be taken by a crane 6.

Description

REMOVING HOLLOW PILES FROM GROUND

The present application relates the removal of hollow piles from ground.

There are many different types of piling system which are used for various structural purposes, for example for providing foundations for structures. In many cases, where it is desired to re-use or remediate a site, old piles have to be removed from ground. The present invention relates to the removal of hollow piles. These are piles, generally made of steel, which have a hollow tubular shape. They normally have a circular cross section, but other cross sections are possible.

Typically, hollow piles are removed by clamping a vibrator to the part of the pile which extends out of the ground and applying vibration at a suitable frequency to the pile.

This is intended to loosen the pile from the surrounding ground. A crane or other lifting device may then be used to lift the pile out of the ground.

However, there are many problems with this process. The vibrator equipment itself is expensive and heavy and can be noisy. The combined weight of vibrator, pile and adhered ground material may be very large, requiring a large crane, which is expensive and can, in some areas, provide problems of access for the large crane.

The present invention sets out to provide a method and apparatus for removing a hollow pile from the ground which overcome these problems. In particular, it is desired to provide a method and apparatus for removing hollow pile from the ground in which the weight of equipment attached to the pile to allow it to be removed is low.

The present inventor has realised that pressurised fluid can be pumped into hollow interior of a hollow pile to drive the pile out the ground, in the manner of a piston.

Accordingly, the present invention provides a method for removing a hollow pile from the ground, in which an end of the hollow pile is closed by the ground, comprising arranging a feed for pressurised fluid to the interior of the hollow pile, closing the hollow pile to prevent escape of pressurised fluid from the interior, and feeding pressurised fluid to the interior, to provide a force tending to remove the hollow pile from the ground which closes its end.

The present invention further provides an apparatus for removing a hollow pile from the ground, in which an end of the hollow pile is closed by the ground, the apparatus comprising means for supplying pressurised fluid to the interior of the hollow pile, means for closing the hollow pile to prevent escape of pressurised fluid from the interior, whereby, when pressurised fluid is fed to the interior, a force is generated tending to remove the hollow pile from the ground closing the end of the hollow pile.

The means for closing the hollow pile and the means for feeding pressurised fluid to the interior of the hollow pile may be relatively light pieces of equipment, as will be explained further below, so that the additional weight applied to the pile in order to remove it from the ground can be kept to a very low level.

Preferred and optional features of the invention will be described further below.

The present invention may be applied to the removal of any kind of hollow pile. It applies particularly to the removal of metal piles, for example steel piles, which may be of any cross section but are typically of circular cross section.

When such piles are driven into ground, a lower end is typically completely closed by ground material. The upper end may be open. Accordingly, in the method of the present invention, the open end must be closed. The present invention may employ a pre-constructed closing member which may be engaged in the outer end of the pile or around the outer end of the pile. The present invention may comprise the step of constructing a closing member as part of the method. The closing member may be constructed in situ. For example, a metal plate, for example a steel plate, may be welded across the end of the pile. The steel plate may be provided with a stiffening member to enable it to resist the pressure of pressurised fluid fed into the interior of the pile. The stiffening member may comprise a beam or rib attached to the closing member. In a preferred embodiment, the stiffening member comprises a body formed of building material such as concrete. The body may be formed to be contained within the hollow end of the pile. It may for example be defmed by a metal shaping body, for example formed of steel. The shaping body may be welded to the closing body.

This arrangement has the advantage that a relatively high stiffness can be provided to the closing body using relatively cheap materials. The closing member may be reusable.

The hollow pile may comprise other openings in the wall, for example bolt holes, vent holes etc. According to the invention, these should be closed as well. They may be closed by any suitable means, for example by welding a patch in place or by inserting closing material, such as cement or other material.

The feed for pressurised fluid preferably comprises a pressurising system and a feeding device. The pressurising system suitably comprises a pump. The feeding device preferably comprises a tube or hose.

The feeding device may feed into the interior of the pile through a hole in the wall of the pile, for example, a pre-existing hole or a hole specially made. Sealing means may be provided between the feeding device and edges of the hole to prevent escape of pressurised fluid.

Preferably, the closing member is designed so that it incorporates the feeding device, or a passage for the feeding device.

In a preferred embodiment, the pressurising system is located at a position which is away from the pile. In this way, the pressurising system, which may have substantial weight, can be placed at a position which is better suited to carrying its weight.

The pressurising system may be designed to provide pressurised fluid at at least two different pressures.

The inventor has realised that the pressure of the pressurised fluid which is required to debond the pile from the surrounding ground (effectively, the static friction) will be higher than the pressure required to maintain movement of the pile out of the ground once it is moving (the dynamic friction). Accordingly, the method of the present invention preferably comprises feeding pressurised fluid to the interior of the pile at a first, higher pressure and, in a second step, feeding pressurised fluid to the interior of the pile, when the pile is moving, at a second, lower pressure.

The pressurising system may be configured to operate so that the pressure of pressurised fluid is variable. Alternatively, the pressurizing system may comprise two separate pressurising devices, one of which is for delivering pressurised fluid at a first higher pressure and the other is for delivering pressurised fluid at a second, lower pressure.

Means may be provided for selectively coupling the first and second pressurising devices, to the feeding device, for example, valves.

Devices for supplying pressurised fluid at high pressure typically operate at relatively low volume flow rates. Devices for operating at lower pressure can operate at higher volume flow rates. The first pressurising device may be used to overcome the static friction, the second pressurising device being used to remove the pile at a relatively high speed, once it has been loosened from the surrounding ground.

Preferably, the pressurising device can supply pressurised fluid at a first pressure in the range 50-100 bar, preferably 60-80 bar, preferably around 70 bar. In order to overcome the static friction, a volume flow rate in the range 0.1-2.0 cubic metres per hour may be sufficient, though larger flow rates may be used.

The pressurising system is preferably capable of delivering pressurised fluid at a second pressure of at least 10 bar, more preferably at least 15 bar when the pile is moving. The second pressure is preferably in the range 10-40 bar more preferably 15-35 bar.

Preferably the pressurising system is capable of delivering pressurised fluid at a rate of at least 10 cubic metres per hour when the pile is moving, more preferably at least 15 cubic metres per hour.

The pressurising system may include a third pressurising device for operating at even lower pressure (suitably in the range 2-10 bar, more preferably 5-8 bar) and preferably operating at a higher flow rate than the first and second pressurising devices, preferably cubic metres per hour or more, for pumping fluid into the hollow interior of the pile to displace any gas which is present.

Control devices may be provided for selectively controlling the pressurising devices and their respective valves.

The pressurising system and devices may comprise any suitable safety features, for example safety release valves.

It is preferred that the pressurised fluid is a liquid. If a compressible fluid, such as a gas were used, there would be a tendency for the gas to store a relatively large amount of energy. Once the pile had been loosened from the ground, the gas would continue to expand and drive the pile from the ground at a rate which might be difficult to control.

By using a substantially incompressible fluid such as liquid a high level of control of the removal can be obtained.

Preferably, the pressurised fluid is water or water based. Water is, of course, readily available and may prevent minimal problems of disposal after use.

It is preferred that an escape valve may be provided for allowing gas contained within the hollow interior of the pile to be displaced by liquid so that there is no reservoir of compressed gas in the pile. The liquid is preferably the pressurised fluid. The escape valve may be closed when all the air has been displaced, so that pressurised fluid cannot escape from the interior of the pile. The escape valve may be opened during pile removal to allow the pressurised fluid to leave the pile as the pile is removed from the ground.

The pressurised fluid may provide the entire driving force necessary to remove the pile from the ground. However, it may comprise a component of the force required to remove the pile, the remainder of the force being provided by another device, for example a crane or a jack. If the pressurised fluid provides enough force to remove the file from the ground, a control device may be provided for supporting the pile while it is being removed from the ground and when it has been removed from the ground, to prevent falling over and causing damage. The support structure may comprise a temporary structure, such as scaffolding. Preferably, however, it comprises a crane which provides a simple and flexible system for guiding the pile.

If an escape valve is provided, it is normally closed while pressurised fluid is fed into the interior of the pile. At a point when the pile is about to be removed from the ground, for example when the weight of the pile is taken by lifting means such as a crane, the valve may be opened to allow pressurised fluid to exit the interior of the pile or to allow air to enter into the interior of the pile so that the pressurised fluid can start to flow out the bottom. This can allow a controlled release of pressurising fluid from the interior of the pile at the point at which it is about to be removed from the ground, thereby preventing sudden load changes due to the weight of matenal contained in the pile.

It has been found that the present invention can be used to remove raked piles which enter the ground at an angle to the vertical.

It is found that the use of pressurised liquid has an additional cleaning effect, tending to clean ground material from the inside of the hollow pile.

According to the present invention, further lifting means may be employed, for example a vibrator to assist with loosening of the pile from the ground.

The present invention has the advantage that it can be operated at relatively low noise level. A smaller crane and smaller vibrator may be used than are normally used to remove piles from the ground. Removal is found to be faster than conventional methods.

In an optional, fmal step, the pile can be prepared for reuse. For example closures applied to the pile to prevent escape of pressurised fluid can be removed. Further cleaning may be carried out.

The present invention will be further described by way of example only with reference to the following drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic representation of an apparatus according to the present invention.

Figure 2 is a schematic cross sectional view, at enlarged scale, of the upper part of the hollow pile shown in figure 1.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic view of an apparatus according to the present invention.

A hollow, circular section steel pile 1 is shown driven into ground (shown, stippled, at 2). A structure 3, which may represent adjacent firm ground, a jetty or other working platform may be constructed or already located near the pile 1.

In a first, preparation step, the pile 1 has been closed using a closure member 4 which will be described further below in relation to figure 2. A feeding device 5 for pressurised water has been arranged whereby pressurised water can be fed into the interior of the hollow pile. A crane 6 is provided, which is arranged for lifting the pile 1 by lifting means 7. A pressurizing system 8 for pressurised water is provided on the structure 3.

It can be seen that the supply of pressurised water 8 comprises a first pressurising device 9, which is configured to act at a higher pressure, for example 70 bar. There is a second pressurismg device, 10, designed to operate at a pressure around 28 bar. The devices 9 and 10 are each connected to the feeding device 5 (which may comprise a pipe or hose) via valves, 11 and 12 respectively. Water for pressurisation, is supplied at 13. There may be a third pressurising device 9a connected to the feeding device, for feeding pressurised fluid at a low pressure around 5- 8 bar.

The pressurising devices are, in each case, pumps of suitable rating, for example displacement pumps or centrifugal pumps may be used for the second and third pressurising devices. A displacement pump is suitable for the first pressurising device.

As shown in Figure 2, the end of the hollow pile 1 is closed by the closure member 4 which comprises a flat steel plate 14. The flat steel plate 14 is reinforced by welding it onto a steel ring 15 which is subsequently inverted and filled with concrete naterial 16 and closed by another plate 17. The entire structure is then butt-welded in position at the periphery 18 of the plate 14. The welds must be capable of containing pressurised fluid at a low level of leakage.

Lifting points 19 have been provided, for example by welding in position, for engaging the lifting means 7 of the crane. A pressurised connection comprising a short section of tube 20 is provided for forming a sealed engagement with the feeding device 5 whereby pressurised water can be fed to the interior of the hollow pile. An additional short section of tube 21 has been welded onto the pile, leading from the pile to atmosphere via a valve 22. This is to allow the removal of air from the pile while the pressurised fluid is being pumped into the interior of the pile. It may also be used to allow the pressurising fluid to exit the pile or to allow air into the pile to displace the pressurising fluid. This may be useful when the pile is about to be removed from the ground, for example using the crane, to allow a controlled exit of pressurising fluid from the interior of the pile. The lower end of the pile is closed by the ground 2 In use, once the apparatus has been set up as shown in figure 1, the low pressure pressurising device 9a feeds pressurized water into the interior of the pile to displace any air located in the pile. Then, the high-pressure pressurizing device 9 is used to supply water at a pressure of around of 70 bar through the feeding means 5 into the interior of the hollow pile 1. As a result, the force tends to drive the pile I upwards.

When the pressure inside the hollow pile reaches a certain level, the pile can be loosened from the ground and starts to rise. At this stage, the high pressure pressurising device 9 is switched off and the lower pressure pressurising device 10 is switched on to supply pressurised water at a lower pressure (45 bar) which is sufficient to drive the pile against the dynamic friction of the ground 2 but at a greater flow rate, allowing the pile to be removed more quickly than if the high pressure were used on its own. The crane 6 is simultaneously used to guide the upward motion of the pile 1, though it does not necessarily need to apply any lifting load to the pile 1 at least during the early stages.

When the pile 1 has nearly been removed from the ground, the crane 6 takes a greater proportion of the weight, in order to ensure safe guiding of the pile 1. When the pile has been removed completely from the ground, supply of pressurised water is switched off and the crane can be used to manoeuvre the pile onto the structure 3.

Example

A hollow circular tubular section pile of diameter 864mm, with an 11mm wall thickness was removed from strata comprising l-8m of soft river alluvium overlying London clay.

The pile had been driven into the London clay for a distance of about 9m.

The pile was engaged with a three-ton weight vibrator and a crane having a lifting capacity at the pile of only 14 tonnes. was provided to lift the pile plus vibrator.

The end of the pile was closed using a steel sheet of circular section reinforced by a cast concrete plug inside a steel ring sealed with a 6mm plate. The 20mm plate was butt-welded to the top of the pile.

A high-pressure hose rated up to 80 Bar was engaged with the interior of the pile, through a pressure connection which is welded in position. A low-pressure pump operating in the range 5-8 Bar at 50 cubic metres per hour was provided. A medium pressure pump operating in the range 23-28 Bar at 20 cubic metres per hour was provided. A high-pressure pump operating at 70 Bar at 0.7 cubic metres per hour was provided. All three were connected to the high-pressure hose via suitable valves.

In a first step, the low-pressure pump was used to fill the pile with water. Then the high-pressure pump was used to apply pressurised water at a pressure of around 45 Bar.

Simultaneously, the vibrator was operated. The pile subsequentLy loosened from the ground, whereupon pressure inside the interior dropped to less than 25 Bar. The medium pressure pump was then used to extract the pile. The crane was used to guide the pile out of the ground and to take the weight of the pile upon leaving the ground. At this point, the pump was switched off. The water started to flow out of the pile and the empty pile was lifted to a storage position. The pressure hose was then removed from the pile.

It was found that the pile could be successfully lifted from the ground. It was found that the interior of the pile comprised a small annulus of stiff clay remaining. This subsequently dried out and, due to contraction, shrank away from the interior of the wall, leaving a clean interior. The entire removal operation for a pile can be carried out in about half a day.

The weight of the pile was 10 tons.

The present invention has been described above by way of example only and modifications can be made within the present invention. The present invention extends to any equivalents of the features described herein or any generalisation of any such features or any combination such features any generalisation of such combinations.

Claims

CLAIMS: I. A method for removing a hollow pile from the ground, in

which an end of the hollow pile is closed by the ground, comprising arranging feed of pressurised fluid to the interior of the hollow pile, closing the hollow pile to prevent escape of pressurised fluid from the interior and feeding pressurised fluid to the interior, to provide a force tending to remove the hollow pile from the ground which closes its end.
2. A method according to claim 1 in which the end which is not closed by ground is closed by a closing member.
3. A method according to claim 2, wherein the closing member comprises a metal plate.
4. A method according to claim 3 or 4, wherein the closing member comprises a reinforced metal plate.
5. A method according to any preceding claim, wherein the pressurised fluid is provided at at least two different pressures.
6. A method according to claim 5, wherein pressurised fluid is supplied at a first, higher pressure, to loosen the pile from surrounding ground and, subsequently, at a second, lower pressure to maintain movement of the pile out of the ground.
7. A method according to claim 5 or 6, wherein the pressurising system comprises a first, higher pressure pressurising device and a second, lower pressure pressurising device.
8. A method according to claim 7, wherein the lower pressure pressurising device is operated at a greater volume flow rate than the higher pressure pressurising device.
9. A method according to any preceding claim, comprising an initial step of displacing gas from the interior of the pile using liquid.
10. A method according to any preceding claim, wherein the pressurised fluid is water.
11. A method according to any preceding claim, wherein a support structure is used to support the pile when it is being removed from the ground.
12. A method according to claim 10, wherein the support structure comprises a crane.
13. A method according to any preceding claim, being used to remove raked piles from ground.
14. A method according to any preceding claim, further comprising the step of cleaning the pile after removal from the ground.
15. A method according to any preceding claim, further comprising the step of permitting air to enter the interior of the pile at the point at which the pile is about to leave the ground, so that pressurising fluid can flow out of the pile.
16. An apparatus for removing a hollow pile from the ground, in which an end of the hollow pile is closed by the ground, the apparatus comprising means for supplying pressurised fluid to the interior of the hollow pile, means for closing the hollow pile to prevent escape of pressurised fluid from the interior, whereby, when pressurised fluid is fed to the interior, a force is generated tending to remove the hollow pile from the ground closing the end of the hollow pile.
17. An apparatus according to claim 16, further comprising a closure member for closing an end of the pile.
18. An apparatus according to claim 16, wherein the closure member comprises a metal closure member.
19. An apparatus according to claim 16 or 17, wherein the closure member comprises a reinforced metal closure member.
20. An apparatus according to any of claims 16 to 19, wherein the pressurising system is configured to operate at at least two different pressures.
21. An apparatus according to claim 20, wherein the pressurising system comprises a first, higher pressure pressurising device and a second, lower pressure pressurising device.
22. An apparatus according to claim 21, comprising a third pressurising device for pumping liquid to the interior of the hollow pile to displace gas contained therein.
23. An apparatus according to claim 21, wherein the lower pressure pressuring device is configured to operate at a greater maximum volume flow rate than the higher pressure pressurising device.
24. An apparatus according to any of claims 16 to 23, wherein an escape valve is provided in the pile, to allow air to be displaced from the interior of the pile by pressurising fluid.
25. An apparatus according to any of claims 16 to 24, further comprising a structure for supporting the pile while it is being removed from the ground.
26. An apparatus according to claim 25 wherein the supporting structure comprises a crane.
27. A method for removing a hollow pile from the ground, substantially as herein described with reference to the accompanying drawing.
28. An apparatus for removing hollow pile from the ground, substantially as herein described with reference to the accompanying drawings.