GB2190413A - Support element and the fixing thereof in a substratum - Google Patents

Abstract

The invention provides a support element e.g. a pole (1) for driving into and fixing within a substratum (2), having a hollow elongate body and an end to be driven into the substratum provided with means (3) for cutting a hole in the substratum of wider cross section than the cross section of the body, whereby the hole (5) formed in the substratum by the cutting means may be loaded with a settable material (e.g. grout or polymeric material) to fix the element therein. The settable material is passed through material conduits (6) which open just above the cutting edge (4). An inspection conduit (7) is also provided. The invention is particularly useful where the substratum is easily damaged, e.g. a friable soil. <IMAGE>

Description

SPECIFICATION Support element and the fixing thereof in a substratum This invention relates to support elements and a means of fixing them in substrata. The invention is described with particular reference to driven piles and the fixing of the same in easily damaged soils, but is not limited thereto.

As is wellknown, installing piles for support of, for example, offshore platforms or the like may be achieved by driving into the soil as opposed to drilling. Driving piles, is a very much quicker operation than drilling. Driven piles are usually quite satisfactory in clays and in silicate sands and silt but there are a number of substrata or soils where the mere action of driving the pile into the substrata damages the fabric. Such materials include calcareous sands and silt, and chalk. In these cases, the crushing by the pile toe as it passes and abrasion by the pile wall as it passes means that soil grains are crushed, and the natural cementing between the grains is destroyed.

In easily damaged substrata, an effective foundation is often obtained by drilling a hole larger than the pile, lowering the pile into the hole and filling the space between the outside of the Pile and the inside surface of the hole with grout, often cement, water and desired additives. Alternatively, a steel reinforcing cage may be lowered into the hole, which is then filled with concrete. In either case, a large amount of soil must be excavated to provide a hole of volume greater than the outside volume of the pile. This operation is very time consuming and may take many days as opposed to the requirement for a few hours only to drive a pile.

The problem of providing an easy means of securing a driven support element in a substratum is by no means limited to grouted or concrete-fixed piles. Wherever it is desired to drive a support element having a cutting edge into a substratum the possibility has to be borne in mind of partial destruction of the fabric of the substratum around the wall of the hole thus created. Even if such damage can subsequently be repaired, the operation of filling the hole and fixing the support element has hitherto been a two stage process.

This invention provides a means of securing support elements by driving into a substratum, preferably in a one stage process, such that the resulting driven element is satisfactorily and securely installed in the substratum avoiding the disadvantages outlined above.

According to the invention there is provided a support element for driving into and fixing within a substratum having a hollow elongate body and an end to be driven into the substratum provided with means for cutting a hole in the substratum of wider cross section than the cross section of the body, whereby the hole formed in the substratum by the cutting means may be loaded with a settable material to fix the element therein. Preferably, the body is provided with at least one conduit ending in a port behind the cutting means to permit the settable material to be passed in fluid form from outside the substratum through the conduit and into the hole cut by driving the element.Such conduits are preferably internal within the hollow body of the element and end in ports behind the cutting means (preferably immediately behind the cutting means) to permit the settable material or grout to be passed from outside the substratum through to the hole which is being cut. It will be appreciated that the invention therefore permits the simultaneous driving of a pile and fixing thereof by means of controlled introduction of the settable material or grout into the hole as it is formed.

In another aspect, the invention provides a method of fixing a hollow elongate support element into a substratum which comprises providing said element at the end thereof which is to be driven into the substratum with means for cutting a hole in the substratum of wider cross section than the cross section of the element, driving said element into the substratum and loading the hole cut in the substratum by the cutting means with a settable material for fixing the element into the hole.

It will be immediately apparent to the skilled man that having regard to the general applicability of the invention any settable or curable material may be used depending upon the precise application of the invention, e.g. grouting material or settable plastics materials. The invention will now be further described specifically by reference to driven piles but it is perfectly apparent that the invention is not limited thereto.

In the accompanying drawings: Figure 1 is a longitudinal cross section of part of a driven pile in accordance with invention; and Figure 2 is a cross section along line AA of Figure 1.

Figure 1 shows the pile generally designated by reference numeral 1 driven into soil 2 (e.g.

a friable soil). Pile 1 is equiped with an integrally-formed shoe 3 at the driven end thereof. Shoe 3 provides an annular step on the outside surface of pile 1. It will, of course, be appreciated that it may not always be necessary or indeed desirable to provide a complete annulus; the purpose of the invention is fulfilled if at least part of the crosssection of the whole produced by driving pile 1 is of greater width than the outside diameter of pile 1.

Shoe 3 is chamfered to provide an inside inclined edge 4 and as pile 1 is driven into soil 2 such soil is cut in a clean fashion and is channelled into the interior of pile 1. Driving or pushing pile 1 into soil 2 thus produces an annular space 5 behind shoe 3.

Pile 1 is also provided with a plurality of internally arranged ducts 6 which each end in ports 8 positioned immediately behind shoe 5.

Ducts 6 aliow liquid grout to be introduced through the pile and through ports 8 out into annular space 5. The rate of introduction of grout may be controlled so that annular space 5 is continuously filled as pile 1 enters soil 2.

When pile 1 has reached the required depth of penetration into soil 2, the grout may be allowed to harden. Obviously, the speed of hardening of the grout may be adjusted by the use of hardeneing-retarding additives or by other means if pile insertion is expected to take some time.

Pile 1 is also provided with an inspection duct 7 and the grout used may be made in part or in its entirety radioactive. This provides an easy means of detecting the progress of grouting of the driven pile 1 by the lowering of a radiation detector through duct 7. Preferably, the rate of introduction of grout is controlled such that annular space 5 is always full to the top. It is, however, possible to envisage circumstances in which filling with grout may be postponed until after the pile has been driven into the soil. However, the preferred embodiments of this invention allow the driving and fixing of piles or other support elements in a one step process.

A suitable means of rendering the grout radioactive is to include within the grout a proportion of irradiated material (e.g. irradiated glass or radioactive fluid). However, it is obvious that alternative means of detection can and may be employed if desired. In Figure 2 duct 7 is shown as having the same approximate dimensions as ducts 6. It will be readily understood that the relative dimensions are immaterial to the performance of the invention but depend solely upon the means of inspection or detection employed making use of inspection duct 7.

As will be understood by the skilled reader, conventional materials such as tubular steel may be employed for the piles or elements of the present invention, depending upon the desired application of the invention. Such matters as the speed to which the settable material is allowed to harden, thus bonding the outside surface of the element to the substratum and repairing any damage done to the fabric of the substratum, are obviously well within the ordinary understanding of the skilled man and may be varied as desired by conventional means for retarding hardening known in the art of settable materials.

It is also perfectly possible to envisage the provision of separate cutting means (shoe 5) of differing sizes for different applications, which means can be fixed (for example, by welding) to an element or pile 1 prior to use.

One beauty of the present invention is that it is extremely flexible in its application. Thus, instead of an annular cutting tool, any desired shape of cutting tool may be provided on the end of the driven element permitting localised supply of settable material only if this is appropriate. For example, it may be desired to drive a pile or other support element into an area where the nature of the soil or substratum changes, immediately over the boundary of such change, with the result that part of the fabric of the soil or substratum may be damaged and part may not.

Claims (19)

1. A support element for driving into and fixing within a substratum having a hollow elongate body and an end to be driven into the substratum provided with means for cutting a hole in the substratum of wider cross section than the cross section of the body, whereby the hole formed in the substratum by the cutting means may be loaded with a settable material to fix the element therein.

2. An element as claimed in claim 1, wherein the body is provided with at least one conduit ending in a port behind the cutting means to permit the settable material to be passed in fluid form from outside the substratum through the conduit and into the hole cut by driving the element.

3. An element as claimed in claim 2, wherein said conduit or, as appropriate, one or more of said conduits is internal within the hollow elongate body, the respective port opening through the wall of the body.

4. An element as claimed in any one of claims 1 to 3, wherein the cutting means is integrally formed with the body.

5. An element as claimed in any one of claims 1 to 3, wherein the cutting means is detachably fastened to the body.

6. An element as claimed in any one of claims 1 to 5, wherein the cutting means comprises an annular cutting tool chamfered on the inside thereof to permit a clean cut to be made when the element is driven into the substratum.

7. An element as claimed in any one of claims 1 to 6, wherein the body is also provided with a monitoring or inspection conduit permitting inspection apparatus to be lowered therethrough to detect the progress of passage of said settable material into the hole in the substratum.

8. An element as claimed in any one of claims 1 to 7 which is a hollow pile for driving into an easily damaged substratum.

9. An element as claimed in claim 1 and substantially as hereinbefore described.

10. A driven pile substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

11. A method of fixing a hollow elongate support element into a substratum which comprises providing said element at the end thereof which is to be driven into the substratum with means for cutting a hole in the substratum of wider cross section than the cross section of the element, driving said element into the substratum and loading the hole cut in the substratum by the cutting means with a settable material for fixing the element into the hole.

12. A method as claimed in claim 11, wherein the element has a hollow body provided with at least one conduit ending in a port behind the cutting means to permit settable material to be passed through the conduit in fluid form from outside the substratum and into the hole cut by the cutting means.

13. A method as claimed in claim 12, wherein said conduit or, as appropriate, at least one of said conduits is internal within the body, the port thereof opening through the body wall behind the cutting means.

14. A method as claimed in any one of claims 11 to 13 further defined by the specific feature of any one of claims 4 to 8.

15. A method as claimed in any one of claims 11 to 14, wherein the settable material is liquid grout.

16. A method as claimed in any one of claims 11 to 14, wherein the settable material is a polymeric material.

17. A method as claimed in any one of claims 11 to 16, wherein the substratum is calcareous sand or silt, or chalk.

18. A method as claimed in claim 11 and substantially as hereinbefore described.

19. A method for fixing a driven pile within a substratum substantially as hereinbefore described with reference to the accompanying drawings.