SUPPORT FOR BUILDING STRUCTURES

Abstract: A method of forming a support or foundation for a building structure comprises forming a number of upwardly diverging support members (122) interconnected at their upper ends by making correspondingly shaped holes in the ground on which the structure is to be supported thereafter pouring concrete into the holes and allowing it to set to form the foundation (132). In certain grounds it may be necessary to extend the support structures (122) by driving piles from their base.

Description: The present invention concerns supports for building structures, especially but not exclusively domestic dwellings. Currently the provision of supports or foundations for relatively small buildings, for example houses, involves numerous and different techniques each of which depends upon the environment in which the building has to be constructed. In certain instances, for example, deep wide trenches have to be dug so that shuttering can be erected on which reinforced concrete footings are formed; in other instances piles have to be driven; in other instances slab floors which may or may not be piled have to be laid; all prior to the actual house erection operation. The Applicants' co-pending Application No. 8602254 discloses one method and apparatus for providing a support for a building irrespective of the environment in which the building has to be constructed, using a ring beam. It is an object of the present invention to provide an improved method and apparatus. According to the present invention there is provided a method of forming a support for a building structure, comprising forming a number of upwardly diverging support members which are interconnected at their upper ends by forming correspondingly shaped holes in the ground in which the structure is to be supported, thereafter pouring concrete into the holes. Preferably each support member is of inverted pyramid shape having a rectangular cross-section. Preferably the support member includes also a pile extending downwardly from its lower end. Preferably the method of forming the hole in which the support member is formed comprises driving an inverted pyramidical steel casing into the ground at the desired location. The steel casing is preferably removed after driving and the hole formed by it is kept open by a temporary casing. It may include an extension from its lower end, the transverse dimensions of the extension being less than those of the casing. The steel casing may be driven with a removable tip thereon which may be removed with the casing after the hole has been formed or alternatively can be left down the hole to form the tip of a pile or pile casing. Preferably the pile or pile casing is guided by the lower opening through the casing during the pile or pile casing driving operation. Preferably the pile or pile casing is driven in a plurality of sections. Preferably the pile driving is terminated when the top of the last driven pile or pile casing section is at a level between the top and bottom of the casing. Preferably said temporary casing includes a body which may be formed from plastics material and is shaped to fit closely against the sides of the hole. Preferably the sides of the temporary casing continuous with the sides of an adjacent hole are arched in plan. Preferably said casing may include an inflatable member adapted to occupy at least part of said hole formed by the extension from the casing. 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 side view of a casing used in the method of the invention; Fig. 2 is an end view of a casing used in the method of the invention; Fig. 3 shows a plan of a support assembly for a building; and Figs. 4 and 5 show respectively an elevation and plan of a temporary casing. The method and apparatus of the present invention has as one of its objects the provision of a simple arrangement for providing a support for a building, which method can be used irrespective of the environment in which the building is being built. A building support comprises a plurality support columns arranged adjacent to each other in overlapping relationship at their upper ends located in the ground on which load bearing walls of a building will be built. Fig. 3 shows such a building base formed by ground-engaging support columns 114, the Figure showing also how the support columns can be located to support features such as a bay window 132. Ground-engaging support columns (not shown) may also be provided to support interior walls or floor areas. After the building site has been initially prepared, for example by levelling, an operative marks out the site according to a pre-arranged plan by marking out the locations of the centre of each column 114 by, for example, a steel pin. Specially designed and constructed apparatus is provided for use in forming a pre-formed hole in which the support column can be formed. The pile driving apparatus comprises essentially a vehicle carrying a pile driving assembly incorporating a large annular mass in the centre of which is located a ram which lifts the mass and allows it to fall onto an anvil which sits on top of a casing to be described below. The apparatus includes also guide means for the anvil and the mass. To provide a good base for the driving assembly to operate from the ground over which it moves can be temporarily covered by reinforced sheets. These may be arranged around the pins in such a manner that they will provide a centre for the driving assembly. In the first instance a casing 122 of the type shown diagrammatically in Figs. 1 and 2 is driven into the ground, centred on the centre of the previously driven steel pin, which is now removed. The casing is rectangular in cross-section and converges downwardly. In side elevation it has a first downwardly converging section 124 which lies at a relatively small angle to the vertical followed by a more steeply angled section 126 leading to an extension 128 whose walls are at a smaller angle to the vertical than the first section. The casing is approximately 2500mm long and its upper rectangular open area is 1500mm by 380mm. The lower open end of the extension is square in cross-section having 152mm, 203mm or 254 mm sides. A removable tip (not shown) is provided on the casing 122 and after fitment of the casing to the anvil of the pile driving assembly and, after careful positioning over the steel pin position, the assembly is operated to force the casing into the ground until its top is at or near ground level. The casing is then withdrawn from the ground so that the tip may be removed before the casing is replaced in the hole. With the anvil lifted off the casing 122 a square cross-section pile section for example of a type disclosed in our U.K. patent application No. 8505799 is located in the lower end of the casing guided by the extension 128. The upper end of the pile is located in a guide on the underside of the anvil which has been lowered onto it. A series of pile sections are driven into the ground below the casing until a pile of a predetermined length is driven with the top of the pile located within the casing. In a modified arrangement it is possible to remove the casing prior to the pile driving operation. As soon as the pile has been driven the casing 122 is removed and the hole in the ground left by the casing is filled with a temporary casing 140, which may be formed from fibreglass contoured to fit closely in the hole around the pile top. The ends 142 of the temporary casing may be arcuate. If for any reason the piling has not been carried out before the casing is removed, an inflatable support 144 (shown diagram­ matically in Fig. 1 by chain lines) may be inserted into the lower part of the hole formed by the extension 128 to prevent infill of earth. When all the holes have been formed and piles driven, the temporary casings are removed and the holes filled with concrete, effectively casting a ring beam (which may be reinforced), in situ. It will be realised that the method and apparatus of the present invention is applicable for any building irrespective of whether the ground is good, bad, subject to heave, water-logged, etc. Perhaps the only skilled operation is the original setting out and thereafter the method can be carried out virtually continuously by unskilled operatives who bring to the site with them all the materials they require. As the process is effectively continuous there need be no delays awaiting the delivery of ready-mixed concrete, rather this can be delivered at any convenient time after the holes have been formed; the only operation to be carried out immediately prior to concreting being the removal of the temporary casings. Numerous modifications can be made without departing from the scope of the invention, for example an hydraulic or pneumatic soil displacement mole could be fitted within the casing and allowed to descend into the ground carrying the casing down with it. The mole could also be used to preform an oversized hole in which a hollow upper pile casing could be fitted in ground subjected to heave. In another method of preforming the hole the casing could be forced into the ground by a suitable vibrating assembly supported by a crane mounted on a transport lorry. In other conditions where the ground is particularly good the pyramidical support column may provide sufficient support and no piles are called for. The casing shown in Figs. 1 and 2 is especially suitable in these circumstances. When piles are driven the extension 128 may be shorter. In buildings which are erected on non-level ground the footings or foundations are often stepped, that is they move from one level to another. The method and apparatus of the present invention can readily cope with this by providing special pyramidical casings 122 which form a step. Thus in operation the step in the foundation is formed at the location of one of the steel pegs driven in during the setting out operation and a stepped casing 122 is utilised at this point.

Claims: 1. A method of forming a support for a building structure, characterised in that it comprises forming a number of upwardly diverging support members intercon­ nected at their upper ends by forming correspondingly shaped holes in the ground on which the structure is to be supported, pouring concrete into the holes and allowing the concrete to set. 2. A method as claimed in claim 1, characterised in that each support member is of inverted pyramid or truncated pyramid shape having a rectangular cross-section. 3. A method as claimed in claim 1 or claim 2, characterised in that the support member includes also a pile extending downwardly from its lower end. 4. A method as claimed in any of claims 1 to 3, characterised in that the said correspondingly shaped hole is formed by driving an inverted pyramidal steel casing (122) into the ground at the desired location. 5. A method as claimed in claim 4, characterised in that the steel casing (122) is removed after driving and the hole formed by the casing is kept open by a temporary casing placed therein. 6. A method as claimed in claim 4 or claim 5, characterised in that the steel casing (122) includes an extension (126) from its lower end, the transverse dimensions of the extension being less than those of the casing. 7. A method as claimed in any of claims 4 to 6, characterised in that the steel casing is driven with a removable tip thereon which is removed with the casing after the hole has been formed or is left down the hole to form the tip of a pile or pile casing. 8. A method as claimed in any of claims 3 to 7, characterised in that the pile or pile casing is guided by the lower opening through the casing during the pile or pile casing driving operation and the pile or pile casing is driven in a plurality of sections. 9. A method as claimed in claim 8, characterised in that the pile driving is terminated when the top of the last driven pile or pile casing section is at a level between the top and bottom of the casing. 10. A method as claimed in any of claims 5 to 9, characterised in that said temporary casing includes a body formed from plastics material shaped to fit closely against the sides of the hole, the sides of the temporary casing contiguous with the sides of an adjacent hole being arched in plan and the casing includes an inflatable member adapted to occupy at least part of said hole formed by the extension from the casing.

Inventors: BULLIVANT, ROGER ALFRED
Applicants: ROXBURY LIMITED
Application year: 1987
Main classification: E02D27
IPC codes: E02D27