GB1603637A

GB1603637A - Supporting building structures

Info

Publication number: GB1603637A
Application number: GB2071677A
Authority: GB
Original assignee: John Laing Services Ltd
Current assignee: John Laing Services Ltd
Priority date: 1977-05-17
Filing date: 1977-05-17
Publication date: 1981-11-25
Also published as: NL7805312A; FR2391323A1; DE2821340A1

Description

(54) SUPPORTING BUILDING STRUCTURES (71) We, JOHN LAING SERVICES LIMITED, a British company, of 133/139 Page Street, London NW7 2ER, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of and arrangement for providing support to a building structure.

For various reasons, the support given to a building structure by the soil beneath it may vary from time to time and under certain circumstances it becomes necessary to provide additional support to a structure.

This practice is generally known as underpinning.

The present invention is concerned with the provision of a method and an arrangement which is particularly suitable for use in providing additional support to domestic dwellings, and it can be used to provide support comparatively quickly and cheaply.

Embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a perspective view of part of a foundation for a building with a supporting structure and Figures 2-6 show diagrammatic vertical sections through respective further arrangements.

Referring to Figure 1, there is shown a part of an existing wall 1 and a part of a transversely extending foundation 2 for the wall which are both below ground level and which have been dug out over the region bounded by chain dotted lines 3. For the purpose of illustrating the invention a larger portion of the wall 1 and the foundation 2 is disclosed in the drawing than is actually dug out.

A hole 4, which is some 10 cms. in diameter, is drilled vertically into the soil at a point which is as near as is possible in practice to the side of the base of the foundation 2 and a galvanised steeI tube 5, which is some 7.6 cms. in diameter, is inserted in the hole 4 and held with its lower end some 15 cms. from the bottom of the hole 4 an its upper end some 15 cms. above the level of the top of the base of the foundation 2. The lower of the tube 5 is plugged with a cork and the outer surface of the tube 5 is wound with a bituminous tape (not shown) over a length of 2 meters, starting at a point some 15 cms. from the top of the tube 5. This winding of tape enables vertical movements of the uppermost layer of the soil to be accommodated.

Cement grout, which may include expander and plasticizer additives, is then pumped into the upper end of the tube 5, forcing the cork out of the lower end of the tube 5, the pressure applied to the grout forcing the grout both into the space at the bottom of the hole 4 and upwards between the outer surface of the tube 5 and the inner surface of the hole 4 until it reaches the lowest level of the dug out region 3 which corresponds to the top of the hole 4 and the level of the bottom of the foundation 2.

A section of the wall 1, indicated by dotted lines 6 and some 22 cms. by 30 cms.

deep, is then cut out above the level of the foundation 2. This hole 6 enables an angled or raking hole 7, which is some 13 cms. in diameter, to be more easily drilled through the foundation 2 at an angle, which in the particular embodiment is of 60 , to the horizontal. A hole 8 is then made in the soil beneath the foundation 2 by means of an auger as an extension of the hole 7. A tube 9, which has its lower end plugged is then inserted into the hole 8 to a depth such that it is some 15 cms. from the bottom of the hole 8 with its upper end extending out of the hole 7 for some 15 cms.Cement grout is then forced down the bore of the raking tube 7 under pressure so that it forces the plug out of the bottom of the tube and fills the hole 8 rising up the outside of the tube 9 and into the space between the tube 9 and the hole 7 until it reaches the upper level of the foundation 2.

Holes (not shown) are then drilled into the top of the base of the foundation 2 and bars 11 are inserted into the holes (not shown) in the top of the base of the foundation 2 and grouted in position by means of a resin mixture. A previously made reinforcing cage, includng bars 12, is positioned above the foundation 2, partly extending into the region 6, and surrounding the tubes 5 and 9 and the bars 11.

Shuttering is then erected around the reinforcing structure and concrete is poured into the shuttering to surround the reinforcing structure in the region indicated by the chain dotted lines 3, the concrete being tightly packed into the wall 1. In a modification, a gap is left between the top of the concrete and the wall 1 and the gap is subsequently filled with "dry pack" concrete. The soil is subsequently reinstated above the hardened concrete which forms a cap uniting the tubes 5 and 9.

If desired, instead of removing the portion 6 of the wall indicated by the dotted lines, holes can be drilled in the wall 1 for the insertion of one end of each of the bars 12, only a part of the portion 6 being removed.

In a further variation of the embodiment described, instead of employing steel tubular piles 5 and 9 and forcing grout down their bores so that it returns on the outside of the tubes, it is possible to use pre-cast concrete piles which are grouted in position, the grout being first introduced into the holes 4 and 8 and being forced into the space between the pile and its respective hole as the pile is forced home into its hole.

Furthermore either of the tubes 5 and 9, or other form of pile, could be inserted at an angle which is different from those shown.

It will also be appreciated that, in addition to removing the portion of the wall 1 within the dotted lines 6, it is possible to remove a corresponding portion of the base 2 of the foundation which extends from the side of the wall 1.

Diagrammatic illustrations will now be described of arrangements employing the invention. In each case comparatively small diameter piles are grouted in holes that have been bored in the soil. Small relative movement between each pile and the soil surrounding the upper part of each pile is made possible by wrapping bituminous tape around each pile for a distance of 2 or 3 meters starting at a point some 15 cms. from the top of each pile. It will be appreciated that no special measure is taken to accommodate horizontal movements of the soil with respect to the piles.

Referring to Figures 2-6, in which similar parts will be referred to by the same reference numerals, there is shown in Figure 2, a wall 15 having a foundation 16 which is comparatively deep. The level of the ground is indicated at 17. In this embodiment, a hole is excavated adjacent to a wall 15 and of sufficient depth to enable a vertically extending pile 18 to be grouted in a hole which has been drilled in the soil in one of the ways previously described with reference to tube 5. A section of the wall 15 is then cut out at 19 and a further hole is drilled through the base of the hole 19 and extended by means of an auger into the soil, thereby enabling a pile 21 to be grouted both in the further hole and in the extension thereof in the soil in the way previously described with reference to tube 9.A reinforced concrete cap 22 is then cast around the tops of the piles 18 and 21, uniting the tops of the piles and acting as a support beam for the wall 15. The cap 22 can conveniently be triangular in plan view with one angled or raking pile 21 near to one corner and a vertical pile 18 near to each of the other corners.

In Figure 3, there is shown an arrangement in which a triangular cap 23 extends through a hole 19 in a wall 15 and couples together a first pile 24, which is in compression, and a pair of piles 25, only one of which is visible, which are in tension. In this arrangement, the cap 23 acts in a cantilever manner in stabilising possible vertical movements of the wall.

In the arrangement of Figure 4, there is a rectangular cap 26 which passes through a wall 15 immediately above a foundation 16 and couples together a pair of angled or raking piles 27, 28.

The arrangement of Figure 5 shows a pair of vertical piles 29, 30 coupled together by a rectangular cap 32, which passes through a wall 15 immediately above a foundation 16.

Figure 6 illustrates a rectangular cap 33 coupling together an angled or raking pile 34 and a vertical pile 35. The cap 33 is formed in a channel beneath a foundation 16 and is laid on a bed of compressible material 36 which is designed to take up vertical movements of the soil in a situation in which the soil "heaves".

It will be appreciated that a new foundation itself can be constructed as a cap for piles that have been grouted in holes in the soil in the way previously described. The foundation in such an arrangement can include a reinforcing cage and forms a ground beam coupling together, for example, two rows of piles which are arranged so that the piles of one row are staggered with respect to the piles of the other row.

The dimensions of the piles, the angles at which they are arranged with respect to a wall and their spacing can be varied, as required, and piles of different length or of different diameter can be coupled together by the same cap or beam.

Within the scope of the appended claims, there are included variations and modifications, including different combinations of the integers of the embodiments which have been described herein by way of example.

For example, the compressible layer 36 could be employed with other of the arrangements described than that of Figure 6.

By grouting the pile 5 in position first, it is possible to use the pile 5 as an anchor for the machinery used to drill and auger holes 7 and 8.

The layer of resilient material provided on the tube to accommodate longitudinal movement may be other than the bituminous tape described, WHAT WE CLAIM IS: 1. A method of providing support for an existing building structure including the steps of drilling a hole for each of first and second piles, the said hole being of greater diameter than its respective pile, inserting each pile in its respective hole, forcing cement grouting between each pile and its respective hole and forming a cap or beam which unites the tops of the first and second piles and provides a support for the structure.

2. A method as claimed in claim 1 including the steps of inserting a tubular pile in its respective hole and pumping cement grout through the bore of the said pile, there being a space between the wall of the hole and the outer surface of the tubular pile such that grout pumped into the tube is forced out of the lower end of the tube upwards from the bottom towards the top of the hole into the space between the tube and the wall of the hole.

3. An arrangement for providing support to an existing building structure including first and second piles, each pile being grouted by means of cement grouting in a hole of greater diameter than the respective pile, and a cap or beam uniting the upper portions of the first and second piles and providing support for the structure.

4. An arrangement as claimed in claim 3 including a layer of flexible material on a portion of the outer surface of the pile to accommodate relative longitudinal movement between the pile and its surroundings.

5. An arrangement as claimed in either claim 3 or claim 4 in which the cap or beam forms a cantilever structure with the first and second piles, one of the piles being in compression and one in tension when in use.

6. An arrangement as claimed in either claim 3 or claim 4 in which the first and second piles are in compression when in use.

7. An arrangement as claimed in any one of the preceding claims in which the cap or beam passes through a cut-out portion in a wall.

8. An arrangement as claimed in any one of the claims 1 to 6 in which the cap or beam is beneath the foundation of a building when in use.

9. An arrangement as claimed in claim 8 in which a layer of compressible material is arranged beneath the cap or beam.

10. A method of providing support for a building structure substantially as described herein with reference to Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, or Figure 6 of the accompanying drawings.

11. An arrangement for providing support for a building structure substantially as described herein with reference to Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, or Figure 6 of the accompanying drawings.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The dimensions of the piles, the angles at which they are arranged with respect to a wall and their spacing can be varied, as required, and piles of different length or of different diameter can be coupled together by the same cap or beam. Within the scope of the appended claims, there are included variations and modifications, including different combinations of the integers of the embodiments which have been described herein by way of example. For example, the compressible layer 36 could be employed with other of the arrangements described than that of Figure 6. By grouting the pile 5 in position first, it is possible to use the pile 5 as an anchor for the machinery used to drill and auger holes 7 and 8. The layer of resilient material provided on the tube to accommodate longitudinal movement may be other than the bituminous tape described, WHAT WE CLAIM IS:

1. A method of providing support for an existing building structure including the steps of drilling a hole for each of first and second piles, the said hole being of greater diameter than its respective pile, inserting each pile in its respective hole, forcing cement grouting between each pile and its respective hole and forming a cap or beam which unites the tops of the first and second piles and provides a support for the structure.