GB2047303A

GB2047303A - Under-pinning

Info

Publication number: GB2047303A
Application number: GB7914454A
Authority: GB
Original assignee: FLOWERDAY L
Current assignee: FLOWERDAY L
Priority date: 1979-04-25
Filing date: 1979-04-25
Publication date: 1980-11-26
Also published as: GB2047303B

Abstract

A method of underpinning comprises the steps drilling one or more holes 20 beyond the lateral extent of existing foundations 12, enlarging the upper regions of the hole(s) laterally beneath the wall and its foundations, introducing an openwork pile 26 and mounting an openwork cap 28 therein and thereafter introducing concrete to fill the hole and encapsulate the pile and cap. <IMAGE>

Description

SPECIFICATION Improvements in or relating to the underpinning of structures This invention concerns improvements in or relating to the under-pinning of structures, and more particularly relates to a system designed to allow the under-pinning of walls of buildings to stabilise foundations or to counteract or prevent subsidence.

One disadvantage of some existing forms of under-pinning is the amount of excavation necessary with its associated cost, inconvenience and possible damage to services such as water, gas, sewage and electricity. The present invention seeks to provide a system of under-pinning which obviates or at least reduces this disadvantage and which embodies a novel pile arrangement.

According to the present invention a method of under-pinning a wall comprises the steps of drilling one or more vertical holes into the ground alongside the external face of the wall but beyond the lateral extent of any foundation thereof, enlarging the upper regions of the hole laterally beneath the wall and any foundation thereof in a divergent manner both vertically and horizontally to provide access to the underside surface of the wall or its foundation over a length substantially greater than the diameter of the bore, driving an openwork pile into the vertical bore and mounting thereon an openwork pile cap extending into the enlargement and in close proximity to said underside surface, introducing a concrete mix into the hole and the enlargement thereof to fill and encapsulate the pile and cap and to form an abutment against said underside surface, compacting said mix and thereafter allowing or causing it to set.

Conveniently, and if necessary, this underpinning is repeated at spaced intervals along the wall to be supported, following which the ground is restored.

The invention will now be further described by way of example with reference to the accompanying drawings in which: Figure 1 is a vertical section through a wall which is being under-pinned according to the method of the present invention, and Figure 2 is a horizontal section taken along the line Il-Il of Figure 1.

Referring to the drawings the method of underpinning according to the invention is shown as being applied to provide a cavity wall 10, having a foundation or supporting platform 12 and providing a support for an elevated floor 14. It is desired to provide additional support, by virtue of under-pinning, to foundation 12 and hence to wall 10.

In achievement of this requirement ground is cut away externally of wall 10 and beyond the lateral extent of foundation 12 to reduce the ground level 16 and allow a vertical hole 18 to be formed. Preferably the hole is developed downwardly with a reduced cross-section as shown at 20. The depth to which 18, 20 is formed is related to the weight carried by wall 10 and foundation 20, and depends on the nature of the sub-soil below ground level 16. Hole 18 is then extended laterally in its upper regions in a divergent manner both vertically and horizontally as at 22, to provide access to the underside surface 24 of foundation 12.

An openwork or lattice pile 26 is then driven through hole 1 8 and into extension 20 thereof and an openwork or lattice pile cap 28 is located -thereon. Members 26 and 28 are prefabricated from suitably shaped rods or wires, with or without mechanical interconnection at crossing points in known manner. The upper regions of cap 28 are located in close proximity to the undersurface 24 of foundation 12 or, when no foundation or the like is present, to the underside of the lower course of bricks or other elements constituting the wall.

Once members 26 and 28 are firmly in place, a concrete mix is introduced into hole 1 8, 20, 22 and compacted therein until it completely fills the pile 26 and pile cap 28 internally and surrounds the pile to embed it and fill hole 18, 20 and 22 up to the level 30, somewhat below ground level 1 6.

The concrete mix is of such a consistency as to form a solid mass within and around the pile and cap, and to form up against undersurface 24 of foundation 1 2. The concrete mix is then allowed or caused to set, after which fill or spoil is introduced above level 30 to bring it up to ground level 16.

This procedure is repeated at spaced intervals along wall 10 to provide the necessary support according to the load (to be) carried by wall 10.

1. A method of under-pinning a wall comprising the steps of drilling one or more vertical holes into the ground alongside the external face of the wall but beyond the lateral extent of any foundation thereof, enlarging the upper regions of the hole laterally beneath the wall and any foundation thereof in a divergent manner both vertically and horizontally to provide access to the underside surface of the wail or its foundation over a length substantially greater than the diameter of the bore, driving an openwork pile into the vertical bore and mounting thereon an operwork pile cap extending into the enlargement and in close proximity to said underside surface, introducing a concrete mix into the hole and the enlargement thereof to fill and encapsulate the pile and cap and to form an abutment against said underside surface, compacting said mix and thereafter allowing or causing it to set.

2. A method as claimed in claim 1 wherein the steps of drilling and enlarging the hole inserting the pile and mounting a cap thereon, and introducing the concrete mix, compacting it and allowing or causing it to set, are repeated at spaced intervals along the wall, whereafter the ground over and around the filled holes is restored.

3. A method as claimed in claim 1 or 2 when applied to a cavity wall, the enlargement of the or

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in or relating to the underpinning of structures This invention concerns improvements in or relating to the under-pinning of structures, and more particularly relates to a system designed to allow the under-pinning of walls of buildings to stabilise foundations or to counteract or prevent subsidence. One disadvantage of some existing forms of under-pinning is the amount of excavation necessary with its associated cost, inconvenience and possible damage to services such as water, gas, sewage and electricity. The present invention seeks to provide a system of under-pinning which obviates or at least reduces this disadvantage and which embodies a novel pile arrangement. According to the present invention a method of under-pinning a wall comprises the steps of drilling one or more vertical holes into the ground alongside the external face of the wall but beyond the lateral extent of any foundation thereof, enlarging the upper regions of the hole laterally beneath the wall and any foundation thereof in a divergent manner both vertically and horizontally to provide access to the underside surface of the wall or its foundation over a length substantially greater than the diameter of the bore, driving an openwork pile into the vertical bore and mounting thereon an openwork pile cap extending into the enlargement and in close proximity to said underside surface, introducing a concrete mix into the hole and the enlargement thereof to fill and encapsulate the pile and cap and to form an abutment against said underside surface, compacting said mix and thereafter allowing or causing it to set. Conveniently, and if necessary, this underpinning is repeated at spaced intervals along the wall to be supported, following which the ground is restored. The invention will now be further described by way of example with reference to the accompanying drawings in which: Figure 1 is a vertical section through a wall which is being under-pinned according to the method of the present invention, and Figure 2 is a horizontal section taken along the line Il-Il of Figure 1. Referring to the drawings the method of underpinning according to the invention is shown as being applied to provide a cavity wall 10, having a foundation or supporting platform 12 and providing a support for an elevated floor 14. It is desired to provide additional support, by virtue of under-pinning, to foundation 12 and hence to wall 10. In achievement of this requirement ground is cut away externally of wall 10 and beyond the lateral extent of foundation 12 to reduce the ground level 16 and allow a vertical hole 18 to be formed. Preferably the hole is developed downwardly with a reduced cross-section as shown at 20. The depth to which 18, 20 is formed is related to the weight carried by wall 10 and foundation 20, and depends on the nature of the sub-soil below ground level 16. Hole 18 is then extended laterally in its upper regions in a divergent manner both vertically and horizontally as at 22, to provide access to the underside surface 24 of foundation 12. An openwork or lattice pile 26 is then driven through hole 1 8 and into extension 20 thereof and an openwork or lattice pile cap 28 is located -thereon. Members 26 and 28 are prefabricated from suitably shaped rods or wires, with or without mechanical interconnection at crossing points in known manner. The upper regions of cap 28 are located in close proximity to the undersurface 24 of foundation 12 or, when no foundation or the like is present, to the underside of the lower course of bricks or other elements constituting the wall. Once members 26 and 28 are firmly in place, a concrete mix is introduced into hole 1 8, 20, 22 and compacted therein until it completely fills the pile 26 and pile cap 28 internally and surrounds the pile to embed it and fill hole 18, 20 and 22 up to the level 30, somewhat below ground level 1 6. The concrete mix is of such a consistency as to form a solid mass within and around the pile and cap, and to form up against undersurface 24 of foundation 1 2. The concrete mix is then allowed or caused to set, after which fill or spoil is introduced above level 30 to bring it up to ground level 16. This procedure is repeated at spaced intervals along wall 10 to provide the necessary support according to the load (to be) carried by wall 10. CLAIMS

3. A method as claimed in claim 1 or 2 when applied to a cavity wall, the enlargement of the or each hole being such as to expose the whole width of the undersurface of the wall adjacent the hole or substantially the whole width of the underside of the foundation or supporting platform at that point.

4. A method as claimed in claim 1 or 2 wherein the wall is supported on a foundation or platform and the or each hole is enlarged beyond the lateral extent of the foundation or platform adjacent the hole.

5. A method as claimed in claim 1, 2 or 3 wherein the or each hole has a reduced crosssection extension, sufficiently large to accommodate the pile, in its lower region.

6. A method as claimed in any one of claims 1 to 4 wherein the openwork pile and pile cap are initially prefabricated from suitably shaped rods or wires, with or without mechanical interconnection at crossing points.

7. A method as claimed in any one of claims 1 to 5 wherein the upper regions of the pile cap are arranged in close proximity to the under-surface of the wall or the foundation associated therewith.

8. An under-pinning for a wall formed by the method of any one of claims 1 to 6.

9. An under-pinning for a wall substantially as herein described with reference to and as illustrated in the accompanying drawings.