GB2255990A

GB2255990A - Underpinning buildings

Info

Publication number: GB2255990A
Application number: GB9210840A
Authority: GB
Inventors: Roger Alfred Bullivant
Original assignee: Roxbury Ltd
Current assignee: Roxbury Ltd
Priority date: 1991-05-22
Filing date: 1992-05-21
Publication date: 1992-11-25
Anticipated expiration: 2012-05-21
Also published as: GB2255990B; GB9210840D0

Abstract

A method of supporting an existing building comprises at a level below ground level removing a short length of two or three courses of brick and supporting the building above the removed portion on a joist 14 with a pile connector 16 at its end and a jack 28, thereafter removing further portions at the same level and supporting these on joists and jack assemblies, providing a reinforced concrete beam which may be pre-formed 32 or case in situ between the joist to support the building and driving piles 38 through the connectors to a predetermined depth to support the beams and the building they support. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO SUPPORTS FOR BUILDINGS The present invention concerns improvements in or relating to supports for buildings, especially but not exclusively existing buildings which have subsided as a result of heave, that is, movement in the sub-soil, normally clay, on which the original foundation is built owing to alterations in the moisture content thereof. The invention is also applicable in buildings which have subsided for reasons other than heave.

In such situations it is desirable that the building is supported on a new support structure which is effectively isolated from the original support strata so that heave can continue to take place without a detrimental effect on the building and its new support structure.

Attempts have been made in the past to provide such new support structures and whereas they have been successfully achieved, success has often been at considerable expense due to the complicated and consequently time consuming and expensive installation procedures involved.

An object of the present invention is to obviate or mitigage these disadvantages.

According to the present invention there is provided a method of supporting an existing building comprising at or below ground level removing a portion of the building placing a primary support assembly in said removed portion, extending the portion at a constant level and inserting a further primary support assembly spaced from said first support assembly, providing a reinforced concrete structure between said primary support assemblies to support the building thereabove, placing piles alongside said building at said primary support assemblies and connecting the placed piles to the support assemblies.

Preferably each primary support assembly comprises a joist having a pile connector fixed to one end thereof and a jack which is removable after the pile has been connected to the support assembly.

Preferably the reinforced concrete structure comprises a pair of pre-stressed concrete lintels.

Alternatively the reinforced concrete structure comprises a beam which is cast in situ in said removed portion.

Preferably the pile connector comprises a downwardly extending tube.

Preferably after providing the reinforced concrete structure but prior to the removal of the jacks, a hole is drilled through the building below the removed section by a drill bit guided in the pile connector. Thereafter a pile is driven into the sub-soil through said connector and drilled hole.

Preferably the pile is driven by augering sub-soil through said connector and drilled hole and thereafter inserting a pile casing. Alternatively a pile casing may be jacked down into the sub-soil trough the connector and drilled hole by means of a hydraulic jacking assembly acting on the pile and fixed to the connector.

Preferably prior to the removal of the jacking assembly and fixing of the piles they are adjusted to correct any subsidence of the building.

Preferably when the pile casing is positioned it is first temporarily welded to the connector and thereafter the gap between the connector and pile is filled with expoxy resin.

Preferably a plurality of removed portions of brickwork are provided in end to end relationship to provide a substantially continuous reinforced concrete structure around the building.

In the embodiment where the reinforced concrete structure is cast in situ secondary support assemblies may be placed at spaced intervals intermediate said primary assemblies. Said second support structures may comprise hollow section members supported on removable jacks.

Preferably said cast in situ beam is formed by introducing reinforcing members into the removed portion above the lower extremeties of the: joists and hollow members, the reinforcing members extending through the hollow members and being connectable to continuity reinforcement attached to the joists, and pouring concrete between the facing faces of adjacent joists and through said hollow members and reinforcing steel.

Preferably the lower face of each joist and hollow member has a spacing bar fixed thereto to define a space between the base of the joist or member and the top of its supporting jack into which space prior to pouring of concrete is inserted a lower shuttering member. The shuttering member preferably comprises an asbestos sheet.

Preferably the hollow members extend beyond the surface of the structure being supported so that side shuttering members may be affixed thereto.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a perspectice view of a length of a building to be supported and the means for supporting it; Fig. 2 is a cross-section on the line II-II of Fig. 1; Fig. 3 is an elevation of a length of a structure to be supported and the modified means for supporting it during construction; Fig. 4 is a cross-section on the line IV-IV of Fig.

3; and Fig. 5 is an elevation of a component of the support means.

In the embodiment illustrated in Figs. 1 and 2, the building to be supported is a cavity brickwork wall 10 which was originally supported on a foundation 11 which having been built, for example, on clay, has moved, thereby failing to efficiently fulfil its function. The present invention aims to provide an alternative support for the brickwork wall.

The method of the present invention is to excavate a trench (not shown) alongside the wall to be supported on the outside of the building of which the wall forms a part. It is not necessary to excavate down to the original foundation.

Working from the excavated trench two courses of brickwork are initially removed over a distance of about half a metre. A primary support assembly 12 is then fitted in the space formerly occupied by the removed brickwork. The support assembly comprises an I-section joist 14 the depth of which is 152mm and the width of which is 114mm". To one end of the joist, which is of a length greater than the thickness of the wall, there is rigidly fixed, for example by welding, a tube 16 the longitudinal axis of which is vertical. The joist 14 is fitted with its top surface 18 abutting the lower surface 20 of the course of bricks defining the top of the region of removed brickwork and its end opposite to that to which the tube 16 is attached in line with or just inside the inside surface 22 of the wall.The joist is supported by a jack 28 interposed between its base 24 and a lower brick course 30 and the jack is activated to hold the joist against the upper brickwork. A further section of brickwork can then be removed to either side of the joist, maintaining the removal at a depth of two courses for a distance of around 3 metres at which point a further primary support assembly 12' is inserted and the operation is repeated all along the wall.

At the conclusion of the preliminary procedures described above, that is after the placement of the further primary support assemblies alongside the first placed primary support assemblies a pair of reinforced concrete lintels 32 are located within the removed brickwork courses. The lintels 32 are pre-stressed and their ends are located between the webs of the joists 14 of the support assemblies 12, 12! Prior to insertion of the lintels a layer of mortar 34 is spread along their top surfaces so that when further jacks (not shown) are placed below the lintels and actuated the lintels are brought into contact with the underside of the remaining wall 10. The jacks can be adjusted to correct subsidence.

With the jacks still in position and not further adjusted epoxy resin spacers 36 are cast between the underside of the lintels and the upper side of the lower flanges of the joists and when these have set they rigidly support the lintels by their ends on the joists.

It will be realised that when the new lintels have been fixed they are held in position by the jacks 28 which, in turn, are supported on the foundation which has to be replaced. Foundation replacement can then commence and a first step is to drill downwardly through the tube 16 fixed to the end of each joist 14 of the primary support assembly 12 through the lower regions of the wall and existing foundation 11 into the sub-soil. A pile hole (not shown) is then formed in the sub-soil by passing a pile forming auger through the tube 16 and the drilled hole and extending the hole into the sub-soil to a predetermined depth.Tubular steel pile casings 38 can then be inserted through the tube 16 and the drilled hole in the building into the sub-soil, the pile casings being isolated by the surrounding soil to minimise the effect of heave thereon by low friction coatings or any suitable known means.

After placing a pile casing 38 in the desired position it is temporarily affixed to the tube 16 at the end of the joist 14 by a preliminary weld and thereafter the gap between the casing 16 and the tube is filled by epoxy resin 40 which is allowed to set thereby providing a rigid connection between the pile casing and the joist which is capable of withstanding not only vertical loads but also twisting loads. Further attachment of the pile casing to the tube is achieved by additional welding along the upper and lower surfaces of the tube 16.It will be realised that the lintels and the building it supports are now supported by the system of piles so that the jacks can be removed and the remaining space between the beam and the upper surface 30 of the remaining foundation structure can be filled with a compressible material, for example, polystyrene foam so that any movement of the existing foundation due, for example, to heave in the sub-soil, is permitted without having any effect on the newly fitted lintels and the original building which they support.

Various modifications can be made without departing from the scope of the invention, for example, the joists can be formed from steel sections other than I-sections.

The piling arrangement is normally dictated by the condition of the ground in which the building structure was originally built. It is possible, for example, to dispense with the augering technique and place the pile casings by jacking them down into the ground utilising hydraulic jacks afixed to the tubes at the end of the joists. Alternatively the piles can be driven by normal impact or vibratory pile driving techniques although these are recognised as not normally being suitable in view of the reactions which they set up which could prove to be damaging to the existing building.

In the modification shown in? Figs. 3, 4 and 5 the reinforced concrete beam is cast in situ. In these drawings and the following description of the modification components similar to those described with reference to Figs. 1 and 2 have been given the same reference numeral.

The method of construction commences in the manner described above but three courses of brick are removed.

In this modification the tube 16 on the end of the joist 14 is inclined downwardly towards the wall at a small angle, for example, 50 and 13mm (2 inch) diameter steel rod 24 is welded to the underside of the joist 14 in alignment with the wells 26 of the joist.

After an interval a secondary support structure 52 is introduced into the area of removed brickwork. The second structure has a depth similar to the joist, that is 152mm, a width which is slightly greater than the width of the wall and a thickness of around 76mm. It is formed from two square cross-section hollow steel sections 54 arranged side-by-side and attached along the joining edges 56. It has a steel bar 58 of 12mm cross-section welded across its base. The sections 54 are located in the gap in the brickwork in a manner similar to the joist and are held against the underside 20 of the remaining brickwork by a further jack 60 in such a position that one section projects outwardly of the outer surface 62 of the wall.

Further sections of brickwork are removed on either side of the primary support structure 12 for a distance of around 3 metres at which point a further primary support structure 12' is inserted and the operation is repeated all along the wall.

At the conclusion of the preliminary procedures described above, that is after the placement of the further primary support structures alongside the first placed primary support structures or after the completion of the entire procedure, that is the placing of a plurality of primary support structures, a reinforced concrete beam is case in situ in the removed brickwork.

This is achieved in the first instance by inserting a reinforcing steel member(s) 50 into the gap, the member(s) 50 being threaded through the passages through the sections of the secondary support structures 52 and linking with continuity reinforcement in the form of arcuate reinforcing members 64 fixed to the sides of the web 26 of the joists 14.

Base shuttering in the form of asbestos sheets 66 is then fitted with the transverse edges of the sheets 66 being located in the gap between the top surfaces of the jacks 28,60 and the lower surfaces of the joists 14 and tubular members 56 respectively, this spacing having been achieved by the steel rods 24,58 fixed to the bottom thereof. It will be realised that rear shuttering will not be required as this will be formed by the ground within the wall. Front shuttering in the form of additional asbestos sheets 68 is attached to the protruding front faces of the tubular members 54 of the secondary support structure by, for example, self tapping screws 70. It will be noticed that in view of this protrusion there is a gap 72 between the front shuttering 68 and the front face 62 of the wall 10 into which concrete can be poured to form the beam.

Prior to the pouring of concrete each jack 12,60 can be individually adjusted to correct any subsidence of the wall and to ensure that the subsequently to be cast beam is correctly positioned. It will be realised that when the new supporting beem has been formed it is held in position by the jacks 28,60 which, in turn, are supported on the foundation which has to be replaced.

Foundation replacement by piles 38 passing through holes drilled through the tubes 16ivan then commence as described with reference to Figs. 1 and 2 and when the beam has been supported on the piles the jacks 28,40 can be removed and the space between the beam and brick course 30 filled with a compressible material.

In the modifications shown in Figs. 3,4 and 5 the tubular members of the secondary support structure need not be side-by-side square section tubular members but could have any other suitable form, provided that they allow the passage of reinforcing steel therethrough and offer adequate vertical support. Alternative forms of shuttering may be employed when the beam is being cast.

Claims

Claims:

1. A method of supporting an existing building comprising at or below ground level removing a portion of the building, placing a primary support assembly in said removed portion, extending the portion at a constant level and inserting a further primary support assembly spaced from said first support assembly, providing a reinforced concrete structure between said primary support assemblies to support the building thereabove, placing piles alongside said building at said primary support assemblies and connecting the placed piles to the support assemblies.

2. A method as claimed in claim 1, in which each primary support assembly comprises a joist having a pile connector fixed to one end thereof supported and a jack which is removable after the pile has been connected to the support assembly.

3. A method as claimed in claim 1 or claim 2, in which the pile connector comprises a downwardly extending tube.

4. A method as claimed in any one of claims 1 to 3, in which after providing the beam but prior to the removal of the jacks, a hole is drilled through the building below the removed section by a drill bit guided in the pile connector.

5. A method as claimed in claim 4, in which after drilling the hole through the building a pile is driven into the sub-soil through said connector and drilled hole.

6. A method as claimed in claim 5, in which the pile is driven by augering sub-soil through said connector and drilled hole and thereafter inserting a pile casing.

7. A method as claimed in claim 5, in which a pile casing is jacked down into the sub-soil through the connection and drilled hole by means of a hydraulic jacking assembly acting on the pile and fixed to the connector.

8. A method as claimed in any one of claims 5 to 7, in which prior to the removal of the jacking assembly and fixing of the piles the jacks are adjusted to correct any subsidence of the building structure.

9. A method as claimed in any one of claims 5 to 8, in which when the pile is positioned it is first temporarily welded to the connector and thereafter the gap between the connector and pile is filled with epoxy resin.

10. A method as claimed in any one of the preceding claims, in which a plurality of removed portions of brickwork are provided in end to end relationship to provide a continuous case in situ beam around the structure.

11. A method of supporting an existing building as claimed in any one of the preceding claims, in which the reinforced concrete structure comprises a pair of pre-stressed concrete lintels.

12. A method of supporting an existing building as claimed in any one of claims 1 to 10, in which the reinforced concrete structure comprises a beam which is case in situ in said removed portion.

13. A method as claimed in any one of the preceding claims, in which the dowardly extending tube of the pile connector is inwardly inclined.

14. A method as claimed in claim 12 or claim 13, in which secondary support assemblies are placed at spaced intervals intermediate said primary assemblies.

15. A method as claimed in claim 14, in which second support structures comprise hollow section members supported on removable jacks.

16. A method as claimed in any of claims 12 to 15, in which said beam is formed by introducing reinforcing members into the removed portion above the lower extremeties of the joists and hollow members, the reinforcing members extending through the hollow members and being connectable to continuity reinforcement attached to the joists, and pouring concrete between the facing faces of adjacent joists and through said hollow members and reinforcing steel.

17. A method as claimed in any one of claims 12 to 16, in which the lower face of each joist and hollow member has a spacing bar fixed thereto to define a space between the base of the joist or member and the top of its supporting jack into which space prior to pouring of concrete is inserted a lower shuttering member.

18. A method as claimed in claim 17, in which the shuttering member comprises an asbestos sheet.

19. A method as claimed in any one of claims 12 to 18, in which the hollow members extend beyond the surface of the structure being supported so that side shuttering members may be affixed thereto.

20. A method of supporting an existing building, substantially as hereinbefore described with reference to Figs. 1 and 2 or Figs. 3 to 5 of the accompanying drawings.

21. Any novel subject matter or combination including novel subject matter disclosed in the foregoing specification or claims and/or shown in the drawings, whether or not within the scope of or relating to the same invention as any of the preceding claims.