GB2408525A

GB2408525A - Method of underpinning

Info

Publication number: GB2408525A
Application number: GB0327604A
Authority: GB
Inventors: Paul Kiss
Original assignee: Abbey Pynford Holdings Ltd; Abbey Pynford House Foundations Ltd
Current assignee: Abbey Pynford Holdings Ltd; Abbey Pynford House Foundations Ltd
Priority date: 2003-11-27
Filing date: 2003-11-27
Publication date: 2005-06-01
Also published as: GB0327604D0

Abstract

A method of supporting brickwork 14 includes the steps of forming at least one composite pile 10 adjacent to the brickwork 14; creating at least one void 21 in the brickwork 14; and connecting a cantilevered support member 18 for the brickwork 14 to each composite pile 10, such that the support 18 extends into the one of the voids 21 in the brickwork 14. In use, the cantilevered supports 18 may be pre-deflected to prevent further movement.

Description

tow- 2408525

IMPROVEMENTS RELATING TO UNDERPINNING

This invention relates to a method of supporting brickwork and to a system for supporting brickwork and, in particular, to a method and system which can be used to underpin existing brickwork, for example, the wall of a building.

The purpose of underpinning is to support a wall that may otherwise subside and, in situations where ground heave may occur, to isolate the underside of the underpinning system from the underlying ground in order to ensure that the effects of ground heave do not lift the wall which is being supported. For many years, underpinning contractors and the like have searched for a simple and easy to use system which requires little or no additional digging and which provides the same level of underpinning support that can be created by fully excavated methods and systems.

In the specification, the term "brickwork" is intended to cover bricks, breeze blocks, concrete units or other blocks which are used in the building industry to construct, for

example, a wall.

Many underpinning systems are in common use at present. One example of a known system is a so-called "hammerhead pile" in which the pile is constructed typically from concrete and the hammerhead out of either reinforced concrete or a prefabricated steel arrangement.

However, this and other known systems suffer from a number of problems. Firstly, it is difficult to reinforce the piles to carry the associated bending moment from the cantilever or, alternatively, it is difficult to find sufficient space and money in which to create the larger diameter piles that are needed. Secondly, significant deflection of the cantilever can be a problem as the support offered to the brickwork is then reduced, leading to the brickwork collapsing. Thirdly, connection between the pile and the cantilever beam is difficult and can result in movement of the cantilever and poor support. Finally, the known systems do not readily lend themselves to dealing with heaving ground, i.e. they do not permit the cost effective creation of a void below the system to isolate the underpinning and the main property from the underlying ground or remnance of foundations, which may subsequently rise.

It is an aim of the present invention to provide a simple and easy to use method of underpinning brickwork and a system for underpinning brickwork which requires little or no excavation of the existing foundations.

According to the present invention, there is provided a method of supporting brickwork, the method comprising the steps of: forming at least one composite pile adjacent to the brickwork; creating at least one void in the brickwork; and 1 1 connecting a cantilever support member for the brickwork to the or each composite pile such that the or each support extends into one of the voids in the brickwork.

The present invention also provides a system for supporting brickwork, the system comprising: at least one composite pile formed, in use, adjacent the brickwork; and a cantilever support member connected to the or each composite pile and extending into a void in the brickwork so as to support the brickwork.

Accordingly, the present invention provides a system which avoids the need to excavate pre-existing foundations and which is capable of absorbing the significant bending moments which are generated between the cantilever and the pile.

The cantilever support member is preferably connected to reinforcementwithin the composite pile. The reinforcement is preferably a metal section, typically box section, within the pile which is typically formed from concrete or the like. The metal section is preferably steel, although other suitable materials could be used. The section may extend within the concrete or, alternatively, may be a sleeve around a concrete centre.

A jack may be used to preload the cantilever support after the support has been connected to the pile so as to set the required supporting force on the brickwork.

Typically, several piles and cantilever supports will be used to support a wall and, when this is the case, it is preferable that an additional support member is mounted between adjacent cantilever supports for providing additional support to the brickwork.

Packing means may be inserted into any gap between any of the support members and the brickwork so as to affect the transfer of load between the brickwork and the support member. In particular, the packing may be a grout bag which can be filled so as to exert a predetermined load on the brickwork.

The cantilever support may include one or more beams and preferably includes a pair of C-section channels on opposing sides of the pile.

One example of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a partial cross sectional view through a system according to the present invention; Figure 2 is a plan view of the system shown in Figure 1; Figure 3 is a front elevation view of a wall in which two cantilever supports have been provided; Figure 4 is a cross sectional view along B-B from Figure 3; Figure 5 is a side elevation view of a bracket for connecting a cantilever to the pile; and Figure 6 is a side elevation view of the upper end of the pile.

Figure 1 shows a composite pile 10 which has been formed in the ground 11 adjacent a set of existing foundations 12 which, previously, supported a wall 13, formed from a double skin of brickwork 14. The pile 10 has, running through its entire length, a metal, typically steel, reinforcement 15. This reinforcement is optional, depending upon the pile requirements and may or may not run the entire length of the pile. The upper portion of the pile is provided with a hollow section 60 which projects from the upper end of the pile and which, elsewhere, is surrounded by a gettable cementitious material such as concrete 16. The sleeve may be a box or other hollow section manufactured from steel although other suitable materials could be used. The pile is formed by excavating a pile bore 17, filling this with the concrete 16 and subsequently plunging the hollow steel section 60 into the concrete. The section serves to reinforce the pile and provide, at its upper end, the connection point for a pair of cantilever arms 18 which may be steel or concrete sections. The cantilever arms 18 are connected, either via screw type fixing means such as bolts or by welding, to a support plate 19 which is, itself, welded to the upper end 20 of the section 60.

One or more voids 21 (seen most clearly in Figure 3) are formed within the brickwork 14 and the cantilever arms 18 extend from the upper end 20 of the pile 10 into the void or voids beneath the brickwork 14.

The upper end 20 of the section 60 is arranged to be below the normal level of the ground and the area surrounding the upper end of the pile is excavated and shattering 51 placed so as to prevent the surrounding earth collapsing into that area. Once the pile has been completed, and the cantilevers placed and loaded in the appropriate manner, this region is filled in, either with earth or further concrete 50, to protect the cantilever and its connection to the pile.

As seen in Figure 3, a jack assembly 30, comprising a jack 31 and a metal tray 32, is placed in the gap between the brickwork 14 and the upper surface of the cantilever.

The tray 32 is provided with upturned edge portions 33 which are sized so as to engage, using lips 34, with the upper surface of the cantilever supports. The jack can then be extended using a predetermined force to thereby predeflect the cantilever to a point at which further deflection is unlikely to occur, thereby ensuring that the cantilever does not move at a later date. The gap between the brickwork and the upper surface of the cantilever is then filled with a packing means 35, which may be dry packing, shims or the like or may, alternatively, take the form of a grout bag (not shown) which can be filled with grout to a predetermined pressure, so as to exert the appropriate load on the brickwork 14.

Depending on the load to be supported, as can be seen in Figure 3, several piles and cantilever supports can be used, typically spaced apart by a distance of between 1 and 2.5 metres along the face of the wall to be underpinned.

If anti-heave precautions are required, one or more additional support sections 40 are located in each open portion 42 of the channel of the cantilever and supported on the lower flanges of the channel of the cantilever. Additional channel sections 41 can then be connected to the support sections 40 and extend between adjacent cantilevers so as to provide additional support to the brickwork 14. If there is any gap between the brickwork 14 and the additional channel sections 41, this can be predeflected using a jack, as described above, and may, subsequently, be filled with a packing material which again may be dry packing or may take the form of an inflated grout bag if pre-deflection is required. It is envisaged that the support sections 40 and additional channel sections 41 may be sized such that when one additional channel section 41 is supported by one or more support sections 40 at each end, the additional channel section 41 is able to support a plurality of brickwork skins 14. This would be particularly useful when a cavity wall is to be supported.

Claims

1. A method of supporting brickwork, the method comprising the steps of: forming at least one composite pile adjacent to the brickwork; creating at least one void in the brickwork; and connecting a cantilevered support member for the brickwork to the or each composite pile such that the or each support extends into one of the voids in the brickwork.

2. A method according to claim 1, wherein the cantilever support member is connected to reinforcement within the composite pile.

3. A method according to claim 2, wherein the reinforcement is either a metal section within the pile or a sleeve around an outer portion of the pile.

4. A method according to any one of claims 1 to 3, further comprising the step of using a jack to preload the cantilever support after it has been connected to the pile.

5. A method according to any one of the preceding claims, further comprising the step of mounting an additional support member between adjacent cantilever supports for providing additional support to the brickwork.

6. A method according to any one of the preceding claims, further comprising the step of inserting packing means into a gap between any support member and the brickwork so as to transfer load between the brickwork and the support member.

7. A method according to claim 6, wherein the packing is a grout bag which can be filled so as to exert a predetermined load on the brickwork and/or serve to pre-deflect the sections.

8. A system for supporting brickwork, the system comprising: at least one composite pile formed, in use, adjacent the brickwork; and a cantilever support member connected to the or each composite pile and extending into a void in the brickwork so as to support the brickwork.

9. A system according to claim 8, wherein each cantilever support member is connected directly to a metal outer sleeve of the composite pile.

10. A system according to either claim 8 or claim 9, wherein the cantilever support member is connected at substantially 90 to the pile.

11. A system according to any one of claims 8 to 10, further comprising an additional support member mounted between adjacent cantilever supports to provide additional support to the brickwork.

12. A system according to any one of claims 8 to 11, further comprising packing means in a gap between any support member and the brickwork so as to transfer the load between the brickwork and the support member.

13. A system according to claim 12, wherein the packing means is a grout bag which is filled so as to exert a predetermined load on the brickwork.

14. A method, substantially as described with reference to the accompanying drawings.

15. A system, substantially as described with reference to the accompanying drawings.