GB2379471A

GB2379471A - Method of trimming the head of a cast-in-situ pile

Info

Publication number: GB2379471A
Application number: GB0120237A
Authority: GB
Inventors: Robert Arthur Merritt; Jimmy Elliott
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-08-20
Filing date: 2001-08-20
Publication date: 2003-03-12
Anticipated expiration: 2021-08-20
Also published as: GB2379471B; GB0120237D0

Abstract

A method for breaking a pile, diaphragm wall, or a barrette foundation element, through a horizontal plane involves casting concrete to above the height of said plane and, while the concrete remains wet, applying tubing (19) from the top of the foundation element towards said plane. The tubing (19) is essentially horizontally disposed and fastened to a support/thrust member (10) having shaft (11, 12) which, in use, extend upwardly and are exposed above the wet concrete so that it can be determined when the tubing (19) is in the correct place. The pile is then broken through said horizontal plane by use of splitting wedges.

Description

CONCRETE FOUNDATION ELEMENTS This invention relates to a method for the removal of the upper portion of reinforced concrete piles, diaphragm wall and barrette foundation elements.

Foundation elements such as reinforced concrete piles and diaphragm walls providing ground support for a civil engineering structure are cast in holes or trenches pre-formed in the ground around a steel reinforcement framework or"cage"which is inserted in the hole or trench before the concrete is poured. The upper ends of the cage members extend above the concrete for incorporation in the overlying structure to be supported. The upper region of the set concrete is usually of inferior quality and strength, for example because it will contain mud or other debris from the bottom of the hole or trench and which"floats"on the surface of the concrete as it is poured, so it is necessary to remove the upper portion of the set concrete pile or diaphragm wall to an accurately-predetermined height to provide a full-strength support for the overlying structure at the required level.

European Patent No. 0888481 describes a method of breaking away and removing the upper portion of a reinforced concrete pile by treating the reinforcement which is to be within that portion of pile subsequently to be broken away so as to isolate it from the concrete cast around it, forming a transverse hole in the pile at the level where it is to be broken away and inserting oppositely-acting wedges within the hole so that, on forcing the wedges apart, they apply forces which act towards opposite ends of the pile to split the pile in a transverse plane. The upper portion may then be removed by lifting it away from the remainder of the pile, the isolation or"debonding"treatment enabling the upper portion to be thus separated from the reinforcement.

It is stated, in said European Patent No. 0888481, to be a preference to form the hole in the pile by inserting piping or tubing through the reinforcement at the intended level before the concrete is cast. It is also preferred to place the debonding material in position before the concrete is cast. However, these steps entail practical problems in that, if the tubing or the debonding material is attached to the reinforcement cage before the cage is placed in the augured pile hole, the actual position of the tubing or the lower end of the debonding

material after placing the cage may not be at the intended level, with the result either that the exposed end of the pile remaining after removal of the upper portion is too low, rendering the pile effectively worthless, or too high, therefore requiring manual remedial work to reduce it to the required height. In any event, the ends of the tubing generally become filled with concrete and are thus difficult to locate and need to be cleaned out before the wedges can be inserted. For these reasons, it is more common practice to drill the hole after the concrete is set. Although drilling can be done at precisely the intended height, however, the operative runs the risk of developing the industrial disease known as Hand Arm Vibration.

To minimise the risk of the debonding material extending too far down the pile-that is, below the intended cut-off level-it has become common practice to apply it"short".

However, this will usually mean that in the pile it extends to a position above the intended cut-off level, this resulting in a pile break which is not clean and requires manual remedial work to make it flat at the required level.

The present invention provides means whereby the tubing and the debonding material can respectively be applied to the pile after the concrete has been poured and to precisely the intended level.

According to one aspect of the invention, a method of applying tubing in an intended horizontal plane in or through a concrete pile, diaphragm wall or barrette foundation element for removal of that portion of the foundation element above the tubing after inserting oppositely-acting wedges therein and applying separation forces thereto to split the foundation element in said horizontal plane comprises casting concrete to form the foundation element to a height above said plane and, while the concrete remains wet, applying tubing from the top of the pile and urging the tubing downwards through the concrete towards said plane, the tubing being essentially horizontally disposed and fastened to a support/thrust member including a shaft element which in use extends upwardly and is exposed above the wet concrete, and measuring the length of the exposed shaft element to determine when the tubing is in said plane.

The support/thrust member may comprise a tubing attachment element to maintain the tubing substantially straight as it is urged downwardly through the wet concrete and an upstanding shaft element or elements attached thereto. Preferably the shaft element or elements is or are formed at the upper end thereof, that is, remote from the tubing attachment element, with engagement means for a device which can apply pushing or pulling forces axially to the shaft element, either to urge it downwardly through the wet concrete or to apply lifting forces to the portion of pile above the tubing after the concrete has set and separation forces have been applied from within the tubing.

In a preferred embodiment, the support/thrust member comprises two essentially parallel shaft body elements joined at their upper or head ends by a loop constituting engagement means for a grab element forming part of a boom assembly for exerting downwards axial pressure and/or for a hook element for exerting upwards axial lifting forces, the shaft elements terminating at their lower ends in outwardly-directed coaxial feet for fastening to the tubing. In use, one or more, preferably two, stabiliser elements may attached between the feet to reinforce the tubing between the feet where, otherwise, it would be unsupported.

The tubing may be held in contact with the stabiliser elements by fastening means such as a flexible elongate wrap material fastened in tensioning manner by a non-return clasp means.

The length of the tubing, and preferably also of the tubing attachment element, should in general be substantially the same as the width of the pile so that the ends of the tubing are essentially flush with the pile surfaces at which the tubing terminates. The tubing may contain a filler material to prevent ingress of wet concrete as the tubing is urged downwardly into its intended position.

The invention also includes a support/thrust member for tubing to be located laterally in a concrete foundation element, the member comprising a U-shaped body member with outwardly-directed coaxial feet, one or more tubing stabiliser member being attached between the feet and extending across the gap between the limbs of the body member in a tubing-support disposition. Preferably, two such stabiliser members are attached on respective adjacent lower quadrants of the feet, whereby the tubing can be received in and

supported by the valley between said stabiliser members. The invention further more includes an assembly comprising a support/thrust member as hereinbefore described and a length of tubing attached to the tubing attachment element thereof.

According to another aspect of the invention, a method of applying isolation material between a concrete foundation element reinforcement member and the concrete from which the foundation element is formed so that the isolation material extends through an upper part of the foundation element subsequently to be broken away above an intended horizontal plane comprises casting concrete to form the foundation element to a height above said plane and, while the concrete remains wet, applying a sleeving of isolation material around the reinforcement member and urging the sleeving downwards through the concrete with an applicator means until the bottom of the sleeving is in said plane and withdrawing the applicator means.

Preferably, the sleeving is caused to be spatially fixed to the reinforcement member before the applicator means is withdrawn.

The applicator means may comprise tubing which is closed at one end, the sleeving being initially inserted in the tubing before being offered to the upper end of the reinforcement member, or may comprise a clamp tool which can engage with the sleeving for application purposes and disengage therefrom for withdrawal purposes.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, of which Figure 1 is a front elevation of a support/thrust member for use in the first aspect of the invention and attached to tubing and Figure 2 is a fragmentary end elevation on an enlarged scale of the apparatus of Figure 1.

Referring firstly to Figure 1, the support/thrust member consists essentially of an inverted U-shaped member shown generally at 10 and including parallel shaft elements 11,12

joined at their upper ends by a loop 13 and formed at their lower ends with outwardly-directed coaxial feet 14,15. Stabiliser bars 16,17 are attached, by welding, to adjacent lower quadrants of and between the feet 14,15, the weld filler metal being shown at 18 (Fig. 2). A length of tubing 19, the ends of the tubing being co-terminus with the outer extremities of the feet 14,15, is attached to and in the gap between the stabiliser bars 16,17 by means of flexible tie-wrap straps 20 the free ends 21 of which are passed through a locking buckle 22 and tightened by applying tension thereto, the locking buckle 22 being of the type which can engage with the strap element 20 to prevent return thereof through the buckle element.

The length of the tubing 19 will be essentially the same as the width of the pile to be formed and the interior of the tubing, at least at its end regions, contains a foamed plastics material 23.

In use in forming a pile, an auger hole is initially formed in the ground to receive the lower end of the concrete pile and suitable reinforcing members are inserted in the hole and surrounded with shuttering or form work above ground level to contain the wet concrete until it has become dimensionally stable. Wet concrete is then poured within the shuttering so that it progressively fills the hole and the void defined by the shuttering and, before it has become dimensionally stable, an assembly of the type shown in Figure 1 is then applied from the top, open end of the shuttering down through the wet concrete until the tubing is at the intended level above which the upper portion of the pile is subsequently to be removed. This is determined by measuring the height of the shaft elements extending above the wet concrete. After the concrete has set and the shuttering has been removed, it is a simple job to locate the ends of the tubing 19 and to insert therein, after removal of the foamed plastics material, the wedge set of a concrete burster and to perform the pile-splitting process, following which the upper portion of the pile can then be removed complete merely by applying a crane hook to loop 13 of the shaft elements and lifting. The tubing may be formed from UPVC or other material which preferably is easy to work and sufficiently rigid to withstand compression pressures in being forced through the wet concrete while nevertheless yielding under the expansion pressure exerted by the wedges.

For use in forming a diaphragm wall, the same method is used but a trench is initially formed in the ground; the shuttering may extend to the bottom of the trench and, after the concrete has set, the shuttering is removed and the trench is back-filled.

Debonding material may be applied to the concrete reinforcement elements while the concrete is still wet by applying a sleeving of such material over the upper exposed ends of the reinforcement members and urging it downwardly through the wet concrete by using an applicator, until the bottom end is at the same level as the tubing 16, tying or otherwise securing it in place on the reinforcement member, and withdrawing the applicator. The applicator may comprise closed-or blind-ended tubing, the open end being applied over the end of the reinforcement member and the blind end urging the debonding material downwardly from the upper end thereof, the tubing being provided with one or more apertures to enable the debonding material to be secured to the reinforcement member before withdrawal of the tubing, or may comprise gripping apparatus comprising a pair of pivoted grip members with suitable clamps attached thereto for gripping the debonding material as it is forced down the reinforcing member. Clamping pressure is maintained while the debonding material is secured to the reinforcement member, whereafter the clamps are released and the apparatus withdrawn. After the concrete has set, the upper part

I [nD iio ae a aet) ai of the pile is then broken away as hereinbefore described, the debonding material enabling o the upper part of the pile to be lifted away from the reinforcement members.

Claims

Claims 1. A method of applying tubing in an intended horizontal plane in or through a concrete pile, diaphragm wall or barrette foundation element for removal of that portion of the foundation element above the tubing after inserting oppositely-acting wedges therein and applying separation forces thereto to split the foundation element in said horizontal plane, the method comprising casting concrete to form the foundation element to a height above said plane and, while the concrete remains wet, applying tubing from the top of the foundation element and urging the tubing downwards through the concrete towards said plane, the tubing being essentially horizontally disposed and fastened to a support/thrust member including a shaft element which in use extends upwardly and is exposed above the wet concrete, and measuring the length of the exposed shaft element to determine when the tubing is in said plane.
2. A method according to claim 1, in which the support/thrust member comprises a tubing attachment element and an upstanding shaft element or elements attached thereto.
3. A method according to claim 2, in which the shaft element or elements is or are formed at the upper end thereof with engagement means for a device which can apply pushing or pulling forces axially to the shaft element.
4. A method according to any preceding claim, in which the support/thrust member comprises two essentially parallel shaft body elements joined at their upper or head ends by a loop constituting engagement means for a grab element and/or for a hook element for exerting upwards axial lifting forces, the shaft elements terminating at their lower ends in outwardly-directed coaxial feet for fastening to the tubing.
5. A method according to claim 4, in which stabiliser elements are attached between the feet to support the tubing.
6. A method according to claim 5, in which the tubing is held in contact with the stabiliser elements by fastening means comprising a flexible elongate wrap material fastened in tensioning manner by a non-return clasp means.
7. A method according to any preceding claim, in which the tubing contains a filler material to prevent ingress of wet concrete as the tubing is urged downwardly into its intended position.

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8. A support/thrust member for tubing to be located laterally in a concrete foundation element, the member comprising a U-shaped body member with outwardly-directed coaxial feet.
9. A member according to claim 8 including one or more tubing stabiliser members attached between the feet and extending across the gap between the limbs of the body member in a tubing-support disposition.
10. A member according to claim 9, including two such stabiliser members attached on respective adjacent lower quadrants of the feet.
11. An assembly comprising a support/thrust member according to any of claims 8 to 10 and a length of tubing attached to the tubing attachment element thereof.
12. A method of applying isolation material between a concrete foundation element reinforcement member and the concrete from which the foundation element is formed so that the isolation material extends through an upper part of the foundation element subsequently to be broken away above an intended horizontal plane, the method comprising casting concrete to form the foundation element to a height above said plane and, while the concrete remains wet, applying a sleeving of isolation material around the reinforcement member and urging the sleeving downwards through the concrete with an applicator means until the bottom of the sleeving is in said plane and withdrawing the applicator means.
13. A method according to claim 12, in which the sleeving is spatially fixed to the reinforcement member before the applicator means is withdrawn.
14. A method according to claim 12 or claim 13, in which the applicator means comprise tubing which is closed at one end, the sleeving being initially inserted in the tubing before being offered to the upper end of the reinforcement member.
15. A method according to claim 12 or claim 13, in which the applicator means comprise a clamp tool which can engage with the sleeving for application purposes and disengage therefrom for withdrawal purposes.
16. A method according to claim 1, substantially as herein described.
17. A support/thrust member according to claim 8, substantially as herein described with reference to and as illustrated in the accompanying drawings.
18. A method according to claim 12, substantially as herein described.