GB2257998A

GB2257998A - Apparatus and method for driving piles

Info

Publication number: GB2257998A
Application number: GB9115844A
Authority: GB
Inventors: Ashley Thomas Beighton
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-07-23
Filing date: 1991-07-23
Publication date: 1993-01-27
Also published as: GB9115844D0

Abstract

A pile-driving method and apparatus wherein an anvil member is disposed in driving relationship to a pile and a hammer is repeatedly lifted and dropped onto the anvil member to drive the pile, the hammer having a body element to which further body elements (24, 26, 27) may be added as the pile is driven to increase the mass of the hammer and maintain the rate of driving the pile. <IMAGE>

Description

Title: Apparatus and method for driving piles Description of Invention This invention relates to a method and apparatus for driving piles into the ground.

There are various ways known for driving piles. The simplest is generally known as a drop hammer, comprising a hammer member which is lifted by a winch and cable and then dropped to apply an impulse to the pile. In the case of a hollow pile of sheet metal, the hammer is lifted and dropped within the pile, and impacts on an abutment at the base of the pile which abutment may be a concrete plug. Such use of a drop hammer, however, has disadvantages in that, because of the necessity of providing and accommodating the winch and associated equipment, it is unsuitable for use in confined spaces or where headroom is restricted, and requires substantial dismantling after one pile has been driven and re-assembly for driving the next pile.Further, although the mass of the hammer may be selected to suit the particular pile and type of ground concerned, it is not readily altered during the driving sequence without dismantling and re-assembly of the driving equipment. Thus as the pile is driven deeper and the resistance due to friction at the surface of the pile increases, the speed at which it is driven decreases.

It has also been proposed to use hammer devices working on the same principle as percussive rock drills, for pile driving. Such a hammer may be used at the base of a pile in the case of a hollow pile, fed with compressed air by a flexible hose, or at the top of the pile if the pile has no space extending through its centre. Such a hammer device is of fixed mass, and therefore also suffers the disadvantage that the speed at which the pile is driven decreases as it is driven more deeply and ground resistance increases. Such a hammer may also be disposed at the top of a hollow pile to drive the pile at its base through the intermediary of a mandrel, with the same disadvantage.

It is broadly the object of the present invention to provide a pile driving method and apparatus in which at least some of the above described disadvantages are overcome or mitigated.

According to one aspect of the invention, we provide pile driving apparatus comprising an anvil member adapted to be placed in driving relationship to a pile, a hammer, and means for lifting the latter and dropping it onto the anvil member to apply an impulse force thereto, said hammer comprising a body element adapted to have a selected number of a plurality of further body elements connected thereto to vary the mass of the hammer member.

Preferably the hammer body element and any required further body elements are connectable to one another in end-to-end relationship to form an assembly of elongate configuration in the direction of lifting and dropping of the hammer member.

The further body elements may be connectable to one another and to the first body element by screw threads in the manner of a ground drilling stem, or may be connectable by any other suitable means. They may be of tubular configuration to provide a continuous passage therethrough when connected together.

The means for lifting the hammer relative to the anvil member is preferably operative between the anvil member and hammer and may be fluid pressure operated, e.g. hydraulically or preferably by compressed air which may be provided to the hammer-lifting means through any further tubular body elements connected to the hammer body element.

In use of apparatus according to the invention for pile driving, the hammer body element may be used with none of the further body elements, or any required number thereof, connected thereto. It is relatively straightforward to add further body elements to the hammer and thus increase its mass. When its mass is increased, the impulse applied to the anvil member when the hammer drops is increased, so that as the pile is driven deeper the same rate of driving may be maintained by suitably increasing the hammer mass. However many further body elements are provided, the hammer retains its freedom of action relative to the pile, so the pile is effectively driven.

Pile driving apparatus according to the invention may be used in driving a pile from the top thereof, e.g. in the case of a solid pile, in which case the anvil member is arranged to be suitably connected to the top of the pile.

Preferably, however, apparatus according to the invention is used for the bottom driving of hollow piles, in which case the anvil member is applied to the base of the pile and the hammer disposed within the pile, at a suitable spacing from the pile casing, to be lifted and dropped therein.

According to another aspect of the invention, we provide a method of driving a pile, comprising applying apparatus according to the first aspect of the invention to the pile and repeatedly lifting and dropping the hammer relative to the anvil member to drive the pile, and further comprising adding further body elements successively to the hammer as the pile is driven.

Use of the method according to the invention enables the pile to be driven at a high and more nearly constant rate as the pile is driven more deeply, compared with what would be the case if the mass of the hammer member were not increased by the addition of further body elements, when the rate of pile driving would decrease as the pile is driven more deeply.

These and other features of the invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 shows diagrammatically an embodiment of pile driving apparatus according to the invention, disposed within a pile; Figure 2 is an enlargement of the part of the pile driving apparatus within the circle 2 of Figure 1.

Referring firstly to Figure 1 of the drawings, a pile is indicated generally at 10. It is a tubular casing of sheet steel, comprising two tubular portions 11, 12 connected in end-to-end relationship at an overlapping welded joint indicated at 13 and extending around the circumference of the pile. At its lower end the tubular portion 12 is closed by crimping as shown at 14. As illustrated the pile has been driven such that only a small portion 15 remains above ground level 16.

Within the pile is disposed a pile driving apparatus which comprises a hammer and anvil assembly 17, as shown in greater detail in Figure 2 at the base of the pile. The driving hammer assembly comprises an anvil 18 and hammer body element 19, the hammer body element and anvil having respective piston and cylinder portions which provide a cylinder space 20 therebetween. An inlet passage 21 provides for admission of fluid under pressure, namely compressed air, to the cylinder space 20. The arrangement is such that the admission of compressed air to the cylinder space 20 will lift the hammer body element relative to the anvil member, and release of such compressed air will permit the hammer body element to drop and apply an impulse force to the anvil.

Mechanism of generally known type is provided to effect such admission and release of air. Above the passage 21, the hammer body element is hollow with an internal cavity 22.

At its uppermost end, the hammer body element is provided with a part-conical screw thread 23, which preferably is of a standard form as used for ground drill stems. This provides for connection of the hammer body element to a superposed further body element 24 which has a corresponding internal screw thread. The further body element 24 at its upper end has a further screw thread 25 providing for connection to successive identical further body elements 26, 27.

Each of the further body elements 24, 25, 27 has a passage extending lengthwise through it to provide a continuous passage 28 leading to the cavity 22 of the hammer body.

The uppermost further body element 27 is connected, again by the same type of screw thread 29, to a cap unit 30. This provides a pipe connection 31 for a source of compressed air. The hammer body element 17, further body elements 24, 26, 27 and cap unit 30, all have flats 32 or other formations for engaging by spanner devices to enable these components to be connected to and disconnected from one another.

In use of the apparatus, driving of the pile would commence with the hammer assembly 17 and one or possibly even none of the further body elements as 24, 26, 27 connected thereto, with, of course, the cap unit 30 connected to the hammer assembly or such further body element. The arrangement is such that the cap unit 30 is accessible above the top of the pile, so the number of further body elements depends on the length of the pile. As the pile is driven, the driving assembly may be withdrawn from the pile to the extent necessary for further body elements to be added to increase the operative mass of the hammer assembly in a number of steps. Thus the rate of pile driving may be maintained as the pile is driven. In principle, the hammer has a variable mass and maintains its freedom of action during driving, to provide a sustained high driving rate.

Although described above in relation to the bottom driving of a hollow pile, the invention is equally applicable to the top driving of a pile which is not hollow to enable the hammer assembly to be disposed within it. In this case, the anvil member is suitably connected to the top of the pile.

It will also be appreciated that modifications may be made in respect of the above described embodiment without departing from the scope of the invention. For example, the hammer body element, further body elements and cap unit may be connected by means other than the screw threads particularly described, e.g. by clamping devices or the like. The hammer may be lifted by means other than compressed air, e.g. hydraulically or by a mechanical means which is not fluid pressure operated. Where the hammer-lifting means is fluid pressure operated, suitable fluid under pressure may be provided thereto by use of an external pipe or pipes rather than the hollow further body elements.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. Pile driving apparatus comprising an anvil member adapted to be placed in driving relationship to a pile, a hammer, and means for lifting the hammer and dropping it onto the anvil member to apply an impulse force thereto, said hammer comprising a body element adapted to have a selected number of a plurality of further body elements connected thereto to vary the mass of the hammer member.

2. Pile driving apparatus according to Claim 1 wherein the hammer body element and further body elements are connectable to one another in end-to-end relationship to form an assembly of elongate configuration in the direction of lifting and dropping of the hammer member.

3. A pile driving apparatus according to Claim 2 wherein the hammer body element and further body elements have screw thread formations for connection to one another.

4. Pile driving apparatus according to Claim 2 or Claim 3 wherein said further body elements are of tubular configuration and when connected together provide a continuous passage therethrough.

5. Pile driving apparatus according to any one of the preceding claims wherein the means for lifting the hammer relative to the anvil member is fluid pressure operated.

6. Pile driving apparatus according to Claim 5 wherein said fluid is compressed air.

7. Pile driving apparatus according to Claim 5 or Claim 6 as appendant to Claim 4 wherein said continuous passage through the further body elements provides for delivery of said fluid to the hammer-lifting means.

8. Pile driving apparatus according to any one of the preceding claims wherein the hammer-lifting means is operative between the anvil member and hammer.

9. The combination of a pile and pile driving apparatus according to any one of the preceding claims, said anvil member being disposed in driving relationship to the pile and said hammer being freely movable relative to the pile.

10. The combination according to Claim 9 wherein said pile comprises a hollow casing having a closed base, and said anvil member lies on said base.

11. The combination according to Claim 10 wherein the body element of the hammer and any further body elements connected thereto are spaced from the interior surface of the casing of the pile.

12. The combination according to Claim 11 comprising a plurality of further body elements, extending substantially up to the top of the pile.

13. A method of driving a pile, comprising applying apparatus according to any one of Claims 1 to 8 to the pile, repeatedly lifting and dropping the hammer relative to the anvil member to drive the pile, and further comprising adding further body elements successively to the hammer as the pile is driven.

14. Pile driving apparatus substantially as hereinbefore described with reference to the accompanying drawings.

15. A method of driving a pile, substantially as hereinbefore described.

16. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.