GB2418026A

GB2418026A - Method of load testing a pile

Info

Publication number: GB2418026A
Application number: GB0518156A
Authority: GB
Inventors: James Mcgrattan
Original assignee: MCGRATTAN PILING Ltd
Current assignee: MCGRATTAN PILING Ltd
Priority date: 2004-09-10
Filing date: 2005-09-07
Publication date: 2006-03-15
Also published as: GB0420077D0; GB0518156D0

Abstract

There is disclosed a method and apparatus for load testing of piles (30;40;50). In the prior art load testing of piles has been achieved using a "Kentledge" block or stack. Such a known technique of load testing is time consuming and expensive. Accordingly, the invention provides a method of load testing a pile (30;40;50), the method comprising the steps of: disposing a load measuring means (34;44;54) above the pile (30;40;50) to be load tested, and applying an axial force or load to the pile (30;40;50) through the load measuring means (34;44;54) by a pile driving means (36) or mechanical excavator (48;58). The load measuring means (34;44;54) comprise a load cell. There are also beneficially provided means for measuring movement or deflection of the pile (30;40;50), e.g. a deflectometer.

Description

1 241 8026

METHOD OF LOAD TESTING A PILE

FIELD OF INVENTION

The present invention relates to a method and apparatus for use in piling, and in particular to an improved method whereby piles may be load tested by easier and cheaper means than conventionally.

BACKGROUND TO INVENTION

The use of piles is of great importance in the construction industry; piles are often driven into the ground in order to support the foundations of a building.

Typically piles are driven into the ground by means of a pile hammer or piling hammer - a heavy hammer which is supported above the pile and reciprocated in order to drive the pile into the ground. Once the pile is in place it can be load tested to ensure it is fit for purpose. Such load testing is typically achieved using what is known as a Kentledge (concrete) block or stack built in a framework, as shown in Figure 1. The Kentledge stack, generally indicated by reference numeral 10, comprises a number of blocks 12 mounted on a frame or secondary beams 14. Initially the weight of the Kentledge stack is supported by support beams (not shown). To test a pile 20, an hydraulic ram or jack 22 is activated to lift the Kentledge stack 10 through main or jacking beam 24. The weight of the Kentledge stack 10 acts on pile 20 through a load cell 26 which measures the force applied to the pile 20. Also deflectometer 21 detects any movement or deflection in the pile 20 as a result of the application of the load. Once the test is finished the load cell 26 is taken away, and the data recorded by the load cell 26 is used to establish whether the pile 20 is or is not fit for purpose.

Each of the blocks 12 in a Kentledge stack typically weighs around 6 tonnes and there can be up to 90 blocks in a Kentledge stack. These blocks are transported to site and the Kentledge stack built in position making this method of load testing a pile time consuming and expensive. The expense of this operation is often 1S compounded by the presence of capital equipment on site, such as pile hammers mounted on cranes or on mechanical excavators sitting idle whilst load testing takes place.

It is an object of at least one embodiment of at least one aspect of the present invention to alleviate or obviate these and other problems in the art.

SUMMARY OF INVENTION

The object is conveniently addressed or achieved by providing the general solution of utilising pile driving means or a mechanical excavator in a method of load testing a pile.

According to a first aspect of the present invention there is provided a method of load testing a pile, the method comprising the steps of: disposing a load measuring means above the pile to be load tested, and applying an axial force or load to the pile through the load measuring means by a pile driving means or mechanical excavator.

The load measuring means (and optionating movements measuring means) may comprise a load cell.

The method may also include the step of providing means for measuring movement or deflection of the pile, e.g. a deflectometer.

The load measuring means (and optional movement measuring means) may be capable of communicating data to a data storage means, e.g. a computer such as a laptop or palmtop computer or the like.

The method may comprise the further steps of: measuring the axial force by means of the load measuring means; preferably though optionally measuring the deflection of the pile under the axial force; and communicating the measured axial force and optionally the measured deflection to a/the data storage means.

The method may also comprise the yet further step of: issuing a certificate indicating the measured axial force, and optionally deflection of the pile, and therefore a load bearing capacity of the pile.

The certificate may be issued in paper and/or electronic form.

The pile driving means may comprise a pile driving rig.

Alternatively, the pile driving means may comprise a mechanical excavator as disclosed in GB 2 351 312B, also by the present Applicant, the content of which is incorporated herein by reference.

Conveniently, therefore, the pile driving means may comprise a mechanical excavator. The mechanical excavator may include an elongate arm having a first end providing first attachment means for attachment to a piling hammer, and a second end providing second attachment means for attaching the arm to a bucket mounting portion of the mechanical excavator, wherein the arm comprises two substantially straight sections fixedly joined at an obtuse angle which angle faces the piling hammer in use. Such an arm is described by the Applicant as "swan necked".

Preferably, the method further includes the step of attaching an additional weight to the mechanical excavator prior to applying the axial force to the pile to enable a greater axial force to be applied to the pile.

Preferably, the additional weight is a pile hammer.

According to a second aspect of the present invention there is provided an apparatus for load testing a pile, the apparatus comprising: a pile driving means or a mechanical excavator, and a load measuring means.

The load measuring means may comprise a load cell.

The apparatus may also include a means for measuring movement or deflection of the pile, e.g. a deflectometer.

The apparatus may further comprise means for communicating data from the load measuring means and/or movement or deflection measuring means to a data storage or computer means.

Alternatively, the load cell may include data storage or computer means.

The pile driving means may comprise a pile driving rig.

Alternatively, the pile driving means may comprise a mechanical excavator.

The apparatus may further include an additional weight, the additional weight being attached to the mechanical excavator.

The additional weight may be a pile hammer.

Preferably, the apparatus includes a data processor and/or printer attached or operably connected to a/the data storage means and/or load cell and/or deflectometer to analyse output data from said load cell and/or deflectometer and to provide on-site certification that a pile is fit for purpose.

According to a third aspect of the present invention these is provided use of a pile driving means or mechanical excavator in a method according to the first aspect of the present invention.

According to a fourth aspect of the present invention there is provided a method of pile driving comprising the steps of: (a) driving a pile into the ground; (b) load testing the pile; (c) optionally repeating steps (a) and (b) until the pile is capable of supporting a predetermined load.

Step (b) may comprise load testing the pile by a method according to the first aspect of the present invention.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described by way of example only, and with reference to the accompanying drawings, which are: Figure 1 a typical method of testing a pile using a Kentledge stack according to the prior art, as previously discussed; Figure 2 a schematic diagram of apparatus used in a method of load testing a pile using a piling hammer according to a first embodiment of the present invention; Figure 3 a schematic diagram of apparatus used in a method of load testing a pile using a mechanical excavator according to a second embodiment of the present invention; Figure 4(a) a schematic diagram of apparatus used in a method of load testing a pile using a mechanical excavator according to a third embodiment of the present invention; and Figure 4(b) a schematic diagram of part of the apparatus of Figure 4(a) to an enlarged scale.

DETAILED DESCRIPTION OF DRAWINGS

Referring to Figure 2 there is shown a schematic diagram of apparatus used in a method of load testing a pile 30 using a piling rig or hammer 36 according to a first embodiment of the present invention. The pile 30 has been driven into the ground 32 in a conventional manner, and is shown in a position to be load tested.

After driving the pile 30, a load measuring device 34 and optional deflectometer (not shown) are disposed axially above the pile 30. The load measuring device 34 then measures the downward axial force being applied to the pile 30 by the piling hammer 36 which is held in position by a mechanical excavator 38. This provides a measure of the load bearing capacity of the pile 30.

If the load bearing capacity of the pile 30 is insufficient then the load measuring device 34 (and optional deflectometer) can be removed and piling recommenced, e.g. using the piling hammer 36. This procedure can be repeated until the load bearing capacity of the pile 30 is sufficient for purpose.

In a modification the load measuring device 34 may be provided between the pile 30 and piling hammer 36 during piling.

Turning now to Figure 3, there is shown a schematic diagram of apparatus used in a method of load testing a pile 40 using a mechanical excavator 48 according to a second embodiment of the present invention. The mechanical excavator 48 has an articulated arm 41 carrying a bucket 43, and applies a load to the pile 40 through load measuring device 44 comprising a load cell, which is mounted on the pile 40.

As well as measuring the load applied to the pile 40, the cell 44 can include means for measuring any deflection or movement (e.g. deflectometer), which occurs within the pile 40.

Attached to the load cell 44 by a cable (not shown) is a data logger (not shown). The data logger records the load applied to the pile 40 and optionally any resultant deflection of the pile 40. The data logger produces via an associated or operably connected printer (not shown) a print-out - optionally instantaneously with the load test being completed - the print-out stating whether or not the pile 40 is fit for purpose. Such "certification" allows a builder to get back to work as soon as the test has finished.

Referring now to Figures 4(a) and 4(b) there is shown an apparatus used in a method of load testing a pile 50 using a mechanical excavator 58 according to a third embodiment of the present invention. The third embodiment is similar to the second embodiment, like parts being identified by the numerals incremented by ten (10). It will, however, be noted that in this third embodiment the arm 41 and bucket 43 of the mechanical excavator 48 are oriented in a different disposition.

Also illustrated is data acquisition and storage means 55, which optionally includes a printer, and which is connected to the load cell 54 by cable 57.

According to a fourth embodiment of the present invention there is provided a method of load testing a pile similar to the second and third embodiments hereinbefore described but instead using a mechanical excavator carrying an elongate (extension) arm and piling hammer as described in GB 2 351 312 B. also by the present Applicant, the content of which is incorporated herein by reference.

It will be understood that the foregoing embodiments are provided for illustrative purposes only, and that various modifications and improvements may be made to the specific methods and apparatus described herein without departing from the scope of the invention.

It can be seen from the foregoing that the present invention provides a simple and effective means whereby a pile may be load tested without the need to bring specialized testing equipment to site. The invention has the further advantage that rapid, and possibly effectively instant, certification of a load bearing capacity of a pile can be provided.

Claims

1. A method of load testing a pile, the method comprising the steps of: disposing a load measuring means above the pile to be load tested, and applying an axial force or load to the pile through the load measuring means by a pile driving means or mechanical excavator.

2. A method of load testing a pile as claimed in claim 1, wherein the load measuring means comprises a load cell.

3. A method of load testing a pile as claimed in either of claims 1 or 2, wherein the method also includes the step of providing means for measuring movement or deflection of the pile such as a deflectometer.

4. A method of load testing a pile as claimed in any preceding claim, wherein the load measuring means and/or movement measuring means is/are capable of communicating data to a data storage means such as a computer means, laptop computer, or palmtop computer.

5. A method of load testing a pile as claimed in any preceding claim, wherein the method comprises the further steps of: measuring the axial force by means of the load measuring means; optionally measuring the deflection of the pile under the axial force; and communicating the measured axial force and optionally the measured deflection to a/the data storage means.

6. A method of load testing a pile as claimed in claim 5, wherein the method also comprises the yet further step of: issuing a certificate indicating the measured axial force, and optionally deflection of the pile, and therefore a load bearing capacity of the pile.

7. A method of load testing a pile as claimed in any preceding claim, wherein the pile driving means comprises a pile driving rig.

8. A method of load testing a pile as claimed in any of claims 1 to 6, wherein the pile driving means comprises a mechanical excavator.

9. A method of load testing a pile as claimed in claim 8, wherein the mechanical excavator includes an elongate arm having a first end providing first attachment means for attachment to a piling hammer, and a second end providing second attachment means for attaching the arm to a bucket mounting portion of the mechanical excavator, and wherein further the arm comprises two substantially straight sections fixedly joined at an obtuse angle which angle faces the piling hammer in use.

10. A method of load testing a pile as claimed in any preceding claim, wherein the method further includes the step of attaching an additional weight to the mechanical excavator prior to applying the axial force to the pile to enable a greater axial force to be applied to the pile.

11. A method of load testing a pile as claimed in claim 10, wherein the additional weight is a pile hammer.

12. An apparatus for load testing a pile, the apparatus comprising: a pile driving means or a mechanical excavator, and a load measuring means.

13. An apparatus for load testing a pile as claimed in claim 12, wherein the load measuring means comprises a load cell.

14. An apparatus for load testing a pile as claimed in either of claims 12 or 13, wherein the apparatus comprises means for measuring movement or deflection of the pile.

15. An apparatus for load testing a pile as claimed in any of claims 12 to 14, wherein the apparatus further comprises means for communicating data from the load measuring means and/or movement or deflection measuring means to a data storage means or computer means.

16. An apparatus for load testing a pile as claimed in either of claims 12 or 13, wherein the load measuring means includes data storage or computer means.

17. An apparatus for load testing a pile as claimed in any of claims 12 to 16, wherein the pile driving means comprises a pile driving rig.

18. An apparatus for load testing a pile as claimed in any of claims 12 to 16, wherein the pile driving means comprises a mechanical excavator.

19. An apparatus for load testing a pile as claimed in claim 18, wherein the apparatus further comprises an additional weight, the additional weight being attached to the mechanical excavator.

20. An apparatus for load testing a pile as claimed in claim 18, wherein the additional weight is a pile hammer.

21. An apparatus for load testing a pile as claimed in any of claims 12 to 20, wherein the apparatus comprises a data processor and/or printer attached or operably connected to a/the data storage means and/or a/the load cell and/or a/the deflectometer to analyse output data from the load cell and/or deflectometer to provide on site certification of a load bearing capacity of a pile.

22. Use of a pile driving means or mechanical excavator in a method according to any of claims 1 to 11.

23. Use of a pile driving means or a mechanical excavator in a method of load testing a pile.

24. A method of driving a pile comprising the steps of: (a) driving a pile into the ground; (b) load testing the pile; repeating steps (a) and (b) until the pile is capable of supporting a predetermined load.

25. A method for driving a pile as claimed in claim 24, wherein step (b) comprises load testing the pile by the method of any of claims 1 to 11.

26. A method of load testing a pile as hereinbefore described with reference to the accompanying drawings.

27. An apparatus for load testing a pile as hereinbefore described with reference to the accompanying drawings.

28. Use of a pile drive means or mechanical excavator in a method of load testing a pile as hereinbefore described with reference to the accompanying drawings.