GB2431938A

GB2431938A - Cruciform ground anchor

Info

Publication number: GB2431938A
Application number: GB0522357A
Authority: GB
Inventors: Peter Dunn
Original assignee: Screwfast Foundations Ltd
Current assignee: Screwfast Foundations Ltd
Priority date: 2005-11-02
Filing date: 2005-11-02
Publication date: 2007-05-09
Anticipated expiration: 2025-11-02
Also published as: GB2431938B; GB0522357D0

Abstract

A cruciform ground anchor, which may be for mounting a post, comprises a plurality of fins 14 which taper towards a lower, in use, end of the anchor. Respective elements 18 are fixed between adjacent fins and provide triangular surfaces which slope together towards the lower end. The respective elements 18 may be triangular plates. The fins 14 may extend from a top plate 10 which may carry a post support portion 16. The fins 14 may be mounted to a central rod 12 or tube extending from the top plate 10.

Description

I

GROUND PENETRATING FOUNDATION

This invention concerns a ground penetrating foundation.

Post supports are known, for example as described in GB 2140057, which have a ground engaging portion of cruciform cross-section provided by a plurality of fins which taper towards a lower end.

An object of the invention is to provide an improved ground penetrating foundation, which may serve to support a post or a column, or any other structure.

According to the invention a ground penetrating foundation of cruciform cross-section provided by a plurality of fins which taper towards a lower end,is characterised in that respective elements are fixed between adjacent fins to provide substantially triangular surfaces which slope towards the lower end.

As the foundation is driven into the ground by impact, in any conventional manner, the aforesaid triangular surfaces serve to compact near surface soils. This improves passive resistance to lateral and vertical loads which act upon the foundation.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic perspective view of a practical embodiment of a foundation in accordance with the invention; Figure 2 is a section along line A-A in Figure 1 in the direction shown; Figure 3 is a section along line B-B in Figure 1 in the direction shown; and Figure 4 is a cross-section at a comparable position to that shown in Figure 3, but of a modified embodiment of the invention.

Referring to Figures 1 to 3, a first practical embodiment of the foundation of the invention comprises a top plate 10, an elongate ground penetration rod 12 and four tapering triangular fins 14. All are suitably formed of galvanised steel. The top plate 10 is substantially square. The rod 12 extends perpendicular to the plate 10 from a substantially central location on the latter. The fins 14 are welded to the top plate 10 in a cruciform arrangement, with the narrowest side edge of each fin 14 extending along a diagonal of the plate 10. The fins 14 are also welded to the rod 12 and, as shown, taper to a location adjacent a free lower end of the rod 12. A box-section post support portion 16 is welded to an upper surface of the top plate 10.

Directly beneath the top plate 10, a respective substantially triangular plate 18 is inserted between each pair of adjacent fins 14 and is welded to said fins 14 in a sloping disposition, inclined inwards towards the central elongate rod 12, ie, towards the axis of the cruciform arrangement of the fins 14.

In use, the foundation is typically driven substantially vertically into the ground, the lower end (tip) of the rod 12 and the narrower lower ends of the tapering fins 14 penetrating first, to a position where the top plate 10 is substantially level with or just above the surface of the ground. Penetration of the ground is facilitated by the known tapering form of the fins 14. The cruciform arrangement of the fins 14 stabilises the foundation, once inserted into the ground, against lateral loads. This is enhanced by the provision of the plates 18 which compact the near surface soil and improve passive resistance to both vertical and lateral loads.

The aforesaid foundation is useful where the load to be supported is less onerous than one where installation of a screw pile is required.

However, a modified embodiment, as shown in Figure 4, may actually be used in combination with a screw pile. In this modified embodiment, tapering fins 14 are fixed to a tubular shaft 20 in place of the central rod 10 so that it can be located and driven into the ground over a projecting upper end region of a screw pile, which has previously been vertically driven into the ground.

The foregoing embodiments are not limitative of the scope of the invention and many variations in detail are possible in other embodiments. For example there may be three tapering fins instead of four, or there may be more than four (although that is unlikely as it is an unnecessary complexity). The fins need not be triangular and may taper only in a lower region, while having an upper region of substantially constant width. The fins need not be welded to a top plate, although that is preferred as it results in a robust construction of maximum rigidity. The fins may be spaced apart from the top plate and welded further down the central rod or tube. However, in other embodiments, the fins may be welded only to each other to provide a cruciform cross-section, without the presence of a central rod or tube. In other embodiment, the additional substantially triangular, sloping surfaces between the fins may be provided by elements which are not simple triangular plates. For example, they may comprise plates which are trapezoidal rather than triangular and/or which have additional projecting portions to facilitate fixing.

The exact shape and size of the elements providing the substantially triangular sloping surfaces depends on the number and spacing of the fins and the angle at which the sloping surfaces are to be fixed. This in turn will vary depending on the soil conditions and the purpose for which the foundation is required. The post support (such as 16 in the illustrated embodiments) is optional and if provided may be of any shape, size or disposition.

Claims

CLAIMS

1. A ground penetrating foundation of cruciform cross-section provided by a plurality of fins which taper towards a lower end, characterised in that respective elements are fixed between adjacent fins to provide substantially triangular surfaces which slope towards the lower end.

2. A foundation as claimed in claim I wherein the respective elements are triangular plates.

3. A foundation as claimed in claim I wherein the fins extend from a top plate and the elements are mounted beneath the top plate.

4. A foundation as claimed in any preceding claim wherein the fins are mounted onto a central rod.

5. A foundation as claimed in any of claims 1, 2 or 3 wherein the fins are mounted onto a central tube.

6. A ground penetrating foundation substantially as hereinbefore described with reference to and as illustrated in any of the accompanying drawings.