GB2356882A - An auger with a cutting element having recesses - Google Patents

Abstract

An auger has a cutting element (14) with a number of recesses (15, 16) cut out of the outer edge of the cutting element (14), which allows secant shaped piling (fig 1) to be constructed. Various shaped recesses are described (figs 4-9). The recesses (15, 16) can be formed by a sliding element, which in the closed position forms a continuous edge on the cutting element (14) or which can be moved to a open position where a recess is formed in the edge of the cutting element (14).

Description

2356882 IMPROVED PILING AUGER, e.q. FOR SECANT WALL PILING The present

invention relates to an auger for use in, for example, secant wall piling.

It is known to construct subterranean walls by forming a series of adjoining or nearly adjoining concrete piles by using auger piling techniques such as continuous f light auger (CFA) auger piling, as described in detail in granted patent nos. GB2303868 and GB2328700, the disclosures of which are incorporated into the present application by way of reference thereto. Auger piling comprises the steps of rotating an auger into the ground, and then withdrawing is the auger, with or without rotation, while pumping concrete to its lower end, thereby forming a concrete pile. A reinforcement member may be inserted into the concrete before it sets so as to provide additional structural strength.

There are several known methods of constructing such a wall using CFA techniques or auger-cast piles.

The simplest method is to form a contiguous bored pile wall, in which a series of piles are formed in a line but without touching one another. This is a relatively straightforward operation and the wall will not be watertight owing to the gaps between the piles.

An alternative technique is to form an interlocking bored pile wall. In this technique, a series of 'female, piles are formed in the desired line of the wall and concreted with a weak concrete mix. No reinforcements are used. A complementary series of 1 male' piles is then formed by boring down at the midpoint between two adjacent female piles, thereby cutting'into the weak concrete mix. Each male pile is then concreted and reinforced in the usual manner so as to leave a series of reinforced, hard concrete piles with the gaps therebetween filled by the weak concrete female piles. This is a great improvement over the contiguous bored pile technique, but does require a great deal of vertical piling accuracy and is still not entirely watertight owing to the properties of the weak concrete of the female piles.

The technique that results in the highest structural integrity is known as secant wall piling.

This is similar to the interlocking bored pile wall construction method outlined above, but strong concrete is used for both the female and the male piles. This means that when forming the male piles, it is necessary for the piling auger to remove concrete from the hardened female piles. This is a difficult and time consuming process, resulting in significant wear on the piling auger. However, the result is a wall that has excellent integrity against water penetration.

According to one aspect of the present invention, there is provided an auger comprising a stem defining a longitudinal axis and carrying a cutting element about said stem, wherein said cutting element is shaped and disposed in a manner such that, when the auger is viewed in a direction parallel to said longitudinal axis, the notional envelope generated by linking together the radially outermost points of the cutting element has the form of a closed geometric form having at least one discontinuity.

The cutting element may be a helical flight, or two or more such flights, or it may be a plurality of blades; or it may be a combination of blades and one or more helical flights.

The notional envelope referred to above is effectively a projection (in a direction parallel to the axis of the auger) of the radially outermost points of the cutting element onto a plane perpendicular to the auger's axis. For a conventional helical flight auger, the notional envelope would be a circle - i.e. a closed geometric form possessing no discontinuities.

In this aspect of the invention, the cutting element is shaped and disposed so that the resultant geometric form of the notional envelope includes at least one discontinuity. Many different geometric forms are possible within the scope of this invention, and the precise form in any given case will be selected according to prevailing operating conditions, e.g. the intended purpose to which the auger is to be put, and the ground conditions at the site. Examples of suitable geometric forms can readily be visualised by starting with the circular envelope of the conventional prior art auger and then introducing one or more discontinuities into the circular form. If the conventional circular envelope is regarded as a disk, the one or more discontinuities may be generated by cutting away peripheral portions of the disk. This process is illustrated in Figures 10-11 of the accompanying drawings. In Fig. 10, the circular envelope 100 corresponds to that of a conventional helical flight auger. If the segment A is removed, the resultant envelope will be partly bounded by dashed line 101 and there will be two discontinuities in the geometric f orm, these being at points d, and d2' Similarly, if the lozenge-shaped section B is removed, there will be two discontinuities at points d3 and d4, and the envelope will be bounded in part by the curved dashed line 102.

By'drawing lines similar to line 101, the initial circular form 100 can be modified to generate any selected polygon. Thus if the point dd is selected, and this point is connected by straight lines extending to points d, and d2, and the three peripheral portions (similar to A) are cut away, the resultant envelope will have the form of a triangle.

Referring to Fig. 11, if portions C and D are cut away, in a manner such that there is a smooth transition at points P and Q, the resultant cuspoid shape has just one discontinuity at point d5.

The approach considered above may be used in the design of augers in accordance with this invention.

Once the geometric form of the notional envelope has been selected, the form and disposition of the cutting element (e.g. blades and/or helical flight(s)) can be designed to conform with the selected envelope.

According to another aspect of the present invention, there is provided an auger comprising a stem defining a longitudinal axis and having at least one generally helical flight disposed around said stem, wherein said at least one flight includes a.plurality of recessed portions at its outer edge, which recessed portions are aligned with each other in a direction parallel to the longitudinal axis of the said stem.

Preferably, two sets of aligned recessed portions are provided on the helical flight, the two sets being positioned on the flight such that the axes of alignment of the recessed portions are diametrically opposed to each other. Alternatively, there may be two parallel and generally coextensive helical flights running together around the stem of the auger, each of the parallel flights having a set of aligned recesses at its outer edge, and the two sets of recesses being aligned in a direction parallel to the axis of the stem and positioned diametrically opposite each other.

The recessed portions are advantageously arcuate in form and may be approximately semi-circular in shape.

According to a third aspect of the present invention there is provided an auger comprising a stem defining a longitudinal axis and having a plurality of blades arranged thereon, wherein said blades are shaped and arranged in a manner such that, when viewed in a direction parallel to said longitudinal axis, the is notional envelope generated by the outermost parts of said blades is a closed geometric form having at least one discontinuity.

According to a forth aspect of the present invention there is provided an auger comprising a stem defining a longitudinal axis and having either a plurality of blades arranged thereon and/or a generally helical flight centred on said stem, wherein said flight includes a plurality of recessed portions at its outer edge, which are aligned with each other in a direction parallel to the longitudinal axis of said stem, or said blades are shaped and arranged in a manner such that, when viewed in a direction parallel to said longitudinal axis, the notional envelope generated by the outermost parts of said blades is a closed geometric form having at least one discontinuity in the form of a recessed portion.

According to a fifth aspect of the present invention there is provided a method of forming a concrete or grout pile, which method comprises the steps of:

i) applying to the ground an auger comprising a longitudinal stem having at least one generally helical flight centred thereon, wherein said flight(s) includes at least one set of recessed portions positioned so as to be aligned with each other in a direction parallel to the longitudinal axis of the auger; ii) applying to said auger forces such that the tool undergoes a first penetration phase and a second withdrawal phase, wherein said second withdrawal phase involves the removal of the auger from the ground in a substantially vertical direction and such that the orientation of the recessed portions remains generally constant; and iii) pumping concrete or grout into the resulting hole either during the second withdrawal phase or after the removal of the tool from the ground.

According to a sixth aspect of the present invention, there is provided a method of forming a concrete or grout pile, which method comprises the steps of:

i) applying to the ground an auger, comprising a stem defining a longitudinal axis having a plurality of blades arranged thereon, wherein said blades are shaped and arranged in a manner such that, when viewed in a direction parallel to said longitudinal axis, the notional envelope generated by the outermost parts of said blades is a closed geometric form having at least one discontinuity.

ii) applying to said auger forces such that the tool undergoes a first penetration phase and a second withdrawal phase, wherein said second withdrawal phase involves the removal of the auger from the ground in a substantially vertical direction and such that the orientation of the recessed portions remains generally constant; and iii) pumping concrete or grout into the resulting hole either during the second withdrawal phase or after the removal of the tool from the ground; The above mentioned methods find particular use in the formation of piles for secant wall construction in which a series of female piles are cast, and a series of male piles subsequently cast in the spaces therebetween.

According to a further aspect of the present invention there is provided a method of constructing a concrete or grout pile wall, which method comprises the steps of:

i) forming a series of female piles in accordance with any one of the methods of claims 19, 23 or 28, such that there exists a predetermined gap between adjacent female piles; ii) forming a series of male piles in said predetermined gaps between said female piles, so as to form a pile wall comprising a series of generally complimentary male and female piles.

During boring, rotation of the auger enables its penetration without hindrance from the removed portions and the penetration rate is desirably controlled so as not to loosen the soil on the auger excessively. once the desired depth is achieved, the orientation of the auger c. an be selected and the auger removed from the ground in a substantially vertical direction and without significant rotation - i.e. such that the orientation of the recessed portions remains substantially constant during withdrawal.

Concrete or grout may then be pumped into the resulting hole thereby forming a shaped pile, exhibiting cut out portions which provide a substantially complementary gap, into which the adjacent male piles may be formed. Alternatively, as disclosed in the applicants patent application nos.

GB9515GS2.7 and GB9827373.3, the disclosures of which are incorporated herein by way of reference thereto, concrete may be supplied to the tip of the auger during the withdrawal phase.

Further benefit may be gained if the discontinuities in the notional envelope were only present during the withdrawal/concreting phase. This could be achieved by incorporating one or a number of sliding elements into the cutting element of the auger.

The sliding elements, which are extendable from an open position, wherein the sliding elements are retracted thereby generating discontinuities inthe outermost part of the cutting element, to a closed position, wherein the sliding elements extend such that the cutting element has a continuous radial edge, may be disposed at predetermined positions about the cutting element. The notional envelope during penetration would thus be a discontinuous closed geometric form, thereby allowing maximum boring efficiency of the tool. Means provided at the top of the auger, allow the sliding elements to be opened/retracted in order to generate the required discontinuities in the cutting element prior to withdrawal.

According to a further aspect of the present invention there is provided an auger comprising a stem defining a longitudinal axis and carrying a cutting element about said stem, wherein said cutting element includes at least one sliding element which is moveable from an open position, wherein said sliding element(s) is retracted so as to introduce a discontinuity in the radial edge of the cutting element, to a closed position, wherein said sliding element(s) extends to the extent that said cutting element has a continuous radial edge.

According to a further aspect of the present invention there is provided a method of forming a is concrete or grout pile, which method comprises the steps of:

i) applying to the ground an auger comprising a stem defining a longitudinal axis and a cutting element disposed about said stem, wherein said cutting element includes at least one sliding element which is moveable from an open position, wherein said sliding element(s) is retracted so as to introduce a discontinuity in the radial edge of the cutting element, to a closed position, wherein said sliding element(s) extends to the extent that said cutting element has a continuous radial edge; ii) applying to said auger forces, so as to facilitate a first penetration phase, wherein said sliding element(s) is in an open position, and a second withdrawal phase, wherein said sliding element(s) is in a closed position, said auger being removed from the ground during the withdrawal phase in a substantially vertical direction, such that the orientation of the discontinuity in the radial edge of the cutting element remains generally constant; and iii) pumping concrete or grout into the resulting hole either during the second withdrawal phase or after the removal of the tool from the ground.

In using an auger of the present invention to form a concrete or grout pile, it is possible to form a series of concrete 'female, piles which feature two diametrically opposed cut out portions which extend along the longitudinal axis of the pile. The shape of the recessed portions or discontinuities on the auger, and therefore the shape of the cut out portions of the pile may preferably be chosen so as to produce a female pile wherein the arc of the cut out portions generally compliment the circumference of the male pile. Such an arrangement allows the male piles to be more easily bored between the adjacent female piles and significantly reduces the wear on the auger.

Alternatively, an auger of the present invention may be used to cast both the female piles and the male piles. In the case where two discontinuities in the notional envelope are generated, the orientation of the auger during removal from the ground when casting the male pile may be rotated by substantially ninety degrees with reference to the orientation at which the auger was removed during casting of the female pile. In this case the male pile will not be generally cylindrical in shape but will be similar in shape to the adjacent female pile. The shape of the recessed portions exhibited by the female pile may advantageously compliment the adjacent outer circumferential portions of the male pile.

The male pile may alternatively be cast by an auger of the present invention which exhibits different geometry. For example, the auger may have a different diameter or the recessed portions on the auger flight may be not be arcuate but may comprise a straight edge leading from one point on the edge of the generally helical flight directly to a second point. Further geometrical modifications involve using convex alternatives to the circular geometry.

In the case where arcuate recessed portions are provided on the flight, these need not be chosen such that the arc of the cut out portions on the resulting pile exactly compliment the circumferential edge of adjacent pile. Indeed, the arc of the recessed portion is may be chosen such that the arc of the resulting cut out portion is smaller than the circumferential edge of the male pile, thereby creating two zones of contact between the piles. Alternatively, if the arc of the recessed portion exhibited by the female pile was larger than the circumferential arc of the male pile, only one zone of contact would be formed between the piles. Furthermore, curvature irregularities may be desired within the cut out portion or additional deliberate protrusions positioned on the cut out portions of either pile may also be envisaged to enhance water tightness, by forcing the male pile to cut the adjacent female piles in several specific locations during its installation. This could be achieved by providing protrusions on the recessed portions of the helical flight.

A further advantage of the present invention is that, due to its shape, the female pile provides a stable guide for the boring of male piles, thus ensuring the male piles can be more easily applied to the ground in a vertical fashion.

A subterranean wall constructed in this way, using an auger of the present invention to cast both the male and female piles, would exhibit an "undulating" outer edge when viewed through the horizontal cross section.

The structural strength of the wall could advantageously be enhanced by the use of interlocking props, in the form of additional shaped piles, cast in a similar, generally complimentary, manner to the alternate male and female piles but in a plane substantially perpendicular to the plane of the wall.

Furthermore, two walls constructed in accordance with the present invention so as to be parallel to one another, may be connected by means of one or a series of interlocking shaped piles.

is A secant wall comprising a series of interlocking shaped piles may be constructed in which the male and female piles are cast one after the other (rather than casting a series of female piles and subsequently forming the male piles in the gaps therebetween). Each pile may be cast such that the resultant wall runs along a substantially straight axis, wherein the central axes of each of the piles lies along the plane of the wall. Alternatively, each pile may be-cast such that the central axes of that of the piles is cast at a predetermined angle with reference to a plane running through the central axis of the adjacent pile. In this way, it is possible to construct a generally curved.

Further alternatives involves the use of an auger which provides only one set of recessed portions on the helical flight. This auger may be used to construct a wall of identically shaped and similarly orientated piles wherein the recessed portion of the auger generally compliments the opposite circumferential edge of that auger. In this case however it has been found that the pile cast must be allowed to set before a subsequent adjacent pile is cast.

The benefits associated with secant wall construction such as excellent water integrity are thereby achieved without experiencing the drawbacks associated when drilling male piles between hard concrete female piles, or when drilling adjacent to a preformed pile.

When constructing a pile wall using a tool according to the present invention, a substantial amount of concrete is saved due to the area of overlap between adjacent interlocking piles. Clearly the is potential saving of material is greater the larger the designed overlap. The maximum overlap is essentially governed by the diameter of the stem. As the reader will readily appreciate, the area of overlap between adjacent interlocking piles also governs the finish of the wall itself. Clearly, in the case of a larger overlap between the piles, the edge of the resulting pile wall will be smoother, whereas if a smaller overlap is employed, then the wall will be further from being a straight edge.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 illustrates the formation of a secant pile retaining wall; Figures 2 and 3 show an auger of the present invention; Figure 4 shows a plan view of a flight in accordance with the present invention; Figure 5 illustrates a female pile in which the recessed portion has a smaller arc than the circumferential arc of the adjacent male pile; Figure 6 illustrates a female pile in which the recessed portion has a larger arc than the circumferential arc of the adjacent male pile; Figures 7A and 7B show a plan view of adjacent male and female piles which have both been formed using an auger of the present invention; is Figure 8 shows a plan view of a wall formation in which adjacent piles are formed using an auger of the present invention which provides one set of recessed portions on the helical flight; Figure 9 illustrates a plan view of a pile formed using an auger of the present invention, in which protrusions are provided on the recessed potions of the pile; Figures 10 and 11 illustrate certain design features associated with one aspect of the invention, as described above; Figures 12 and 13 illustrate subterranean walls constructed in accordance with the present invention; and Figure 14 illustrates the relative positions at which adjacent piles may be cast using a tool of the presentinvention, in order to construct a generally curved wall.

Figure 1 illustrates a secant wall construction in which a series of female piles 2 are formed in a line having a predetermined series of gaps there between.

Male piles 3 are then formed in the gaps between the preformed line of female piles so as to form a substantially complimentary wall of alternate male and female piles. The piles are all formed from strong concrete or grout thereby resulting in a generally watertight wall with high structural integrity.

Figures 2 and 3 show different views of an auger 12 of the present invention. The auger comprises a longitudinal stem 13 having a helical flight 14 centred thereon. The flight exhibits two sets of recessed portions 15, which are aligned with the longitudinal axis of the stem 13. The sets of recessed portions 15 are positioned on the flight 14, such that they are diametrically opposed to each other. Each recessed portion 16 is substantially semi circular in shape.

Figure 4 illustrates the flight 14 of figure 2 and 3, when viewed directly from.above or below. The projected image of the flight indicates the shape of the female piles formed by an auger of the present invention.

Figure 5 illustrates a female pile 18, in which the recessed portion 19 has a smaller arc than the circumferential arc of the adjacent male pile 20. In this situation there exists two zones of contact, 21a and 21b, between the piles. Alternatively, as shown in Figure 6, the arc of the recessed portion 23 exhibited by the female pile 22 may be larger than the circumferential arc of the adjacent male pile 25, therefore only one zone of contact 24 would be formed between the piles.

Figures 7A and 7B illustrate embodiments in which an auger of the present invention may be used to form both the male and the female piles. when forming the male pile 27 adjacent to the female pile 26, the orientation of the auger during removal from the ground is rotated by ninety degrees relative to the auger orientation during removal in casting the female pile.

In this case the same auger may be used to form both of the piles. However, as illustrated in Figure 7B, it may be advantageous to construct a pile wall in which the geometry of the male pile is slightly different to that of the female pile. In this case the male pile 29 has been formed from an auger in accordance with the present invention, in which the recessed portions of the auger, have been formed by effectively cutting across the edge of the flight in a generally straight line.

Figure 8 illustrates an alternative construction in which both the male and female piles are cast using an auger of the present invention. The piles are formed using an auger which provides only one setof recessed portions on the cutting element. This auger can then be used to construct a wall of substantially identically shaped and similarly orientated piles wherein the recessed portion of the auger generally compliments the opposite circumferential edge of the auger.

Additional protrusions may be provided on the recessed portions of the auger such that a pile 30, as illustrated in Figure 9, may be formed exhibiting protrusions 31 and 32. If a male pile were to be cast adjacent to such a female pile, the resulting construction would benefit from enhanced water tightness.

Figures 12 and 13 illustrate the horizontal cross sectional views of subterranean walls which have been constructed using an auger of the present invention to cast both the male and female piles. The wall will exhibit a generally undulating outer edge due to the shape and orientation of the resulting piles. In figure 12, the wall 34 comprises a series of interlocking male piles 35 and female piles 36. In addition, piles 37 have been cast in a plane perpendicular to the plane of the wall, in order to acts as props to increase the strength of the structure. Figure 13 illustrates a is structure which comprises two such undulating walls 40 and 41 which run parallel to one another, and are linked by internal connecting piles 39.

Figure 14 demonstrates the geometric arrangement of a series of piles which are cast such that the central axis 42 of each pile is positioned at a predetermined angle e with reference to a plane 43 running through the central axis of the adjacent pile.

In this way, it is possible.to construct a generally curved wall as shown. The angle e may remain identical between each subsequent pile, or may be varied in accordance with the required shape/curvature of the structure.

The reader should appreciate that various modifications may be made to the shape and relative size of the recessed portions on the auger flight, without departing from the concept of the present invention. It should also be noted that the helical flight is prone to considerable wear and therefore, in the case of the present invention, there will be 18naturally occurring distortions on the pile shape.

Claims (33)

1. An auger comprising a stem defining a longitudinal axis and carrying a cutting element about said stem, wherein said cutting element is shaped and disposed in a manner such that, when the auger is viewed in a direction parallel to said longitudinal axis, the notional envelope generated by linking together the radially outermost points of the cutting element has the form of a closed geometric form having at least one discontinuity.

2. An auger as claimed in claim 1, wherein said closed geometric form has at least two discontinuities.

3. An auger as claimed in claim 1 or 2, wherein said cutting element comprises a helical flight.

4. An auger as claimed in claim 1, 2 or 3, wherein said cutting element comprises a plurality of blades.

5. An auger comprising a stem defining a longitudinal axis and carrying a cutting element about said stem, wherein said cutting element includes at least one sliding element which is moveable from an open position, wherein said sliding element(s) is retracted so as to introduce a discontinuity in the radial edge of the cutting element, to a closed position, wherein said sliding element(s) extends to the extent that said cutting element has a continuous radial edge.

6. An auger as claimed in claim 5, wherein said cutting element includes two sliding elements.

7. An auger as claimed in claim 5, wherein said cutting element includes three sliding elements.

8. An auger as claimed in claim 5, 6 or 7, wherein said cutting element comprises a helical flight.

9. An auger as claimed in claim 5, 6 or 7, wherein said cutting element comprises a plurality of blades.

10. An auger as claimed in any one of claims 5 to 9, wherein said sliding element(s), when in an open position, introduces a generally arcuate discontinuity is in the outer radial edge of the cutting element.

11. An auger comprising a stem defining a longitudinal axis and having at least one generally helical flight disposed around said stem, wherein said at least one flight includes a plurality of recessed portions at its outer edge, which recessed portions are aligned with each other in a direction parallel to the longitudinal axis of the said stem.

12. An auger as claimed in claim 11, wherein said helical flight includes two sets of recessed portions positioned on said flight(s) such that the axes of alignment of said recessed portions are diametrically opposed to each other.

13. An auger as claimed in claim 11 or 12, wherein said recessed portions are generally arcuate in form.

14. An auger as claimed in claim 11, 12 or 13, wherein said recesses are all substantially identical in size'and shape.

15. An auger as claimed in claim 11, which comprises two parallel and generally coextensive helical flights running together around the stem of the auger, each of the parallel flights having a set of aligned recesses at its outer edge, and the two sets of recesses being aligned in a direction parallel to the axis of the stem and positioned diametrically opposite each other.

16. An auger comprising a stem defining a longitudinal axis and having a plurality of blades arranged thereon, wherein said blades are shaped and arranged in a manner such that, when viewed in a direction parallel to said longitudinal axis, the notional envelope generated by the outermost parts of said blades is a closed geometric form having at least one discontinuity.

17. An auger as claimed in claim 16, wherein said discontinuity results in the formation of a generally circular form having a recessed portion.

18. An auger comprising a stem defining-a 2S longitudinal axis and having either a plurality of blades arranged thereon and/or a generally helical flight centred on said stem, wherein said flight includes a plurality of recessed portions at its outer edge, which are aligned with each other in a direction parallel to the longitudinal axis of said stem, or said blades are shaped and arranged in a manner such that, when viewed in a direction parallel to said longitudinal axis, the notional envelope generated by the outermost parts of said blades is a closed geometric form having at least one discontinuity in the form of'a recessed portion.

19. A method of forming a concrete or grout pile, which method comprises the steps of:

i) applying to the ground an auger comprising a longitudinal stem having at least one generally helical flight centred thereon, wherein said flight(s) includes at least one set of recessed portions positioned so as to be aligned with each other in a direction parallel to the longitudinal axis of the auger; ii) applying to said auger forces such that the tool undergoes a first penetration phase and a second withdrawal phase, wherein said second withdrawal phase involves the removal of the auger from the ground in a substantially vertical direction and such that the orientation of the recessed portions remains generally constant; and iii) pumping concrete or grout into the resulting hole either during the second withdrawal phase or after the removal of the tool from the ground.

20. A method as claimed in.claim 1, wherein said helical flight includes two sets of recessed portions positioned on said flight(s) such that the axes of alignment of said recessed portions are diametrically opposed to each other.

21. A method as claimed in claims 19 or 20, wherein said recessed portions are generally arcuate in f orm.

22. A method as claimed in claim 19, 20 or 21, wherein said recesses are all substantially identical in size and shape.

23. A method of forming a concrete or grout pile, which method comprises the steps of:

i) applying to the ground an auger, comprising a stem defining a longitudinal axis having a plurality of blades arranged thereon, wherein said blades are shaped and arranged in a manner such that, when viewed in a direction parallel to said longitudinal axis, the notional envelope generated by the outermost parts of said blades is a closed geometric form having at least one discontinuity.

ii) applying to said auger forces such that the tool undergoes a first penetration phase and a second withdrawal phase, wherein said second withdrawal phase involves the removal of the auger from the ground in a substantially vertical direction and such that the orientation of the recessed portions remains generally constant; and iii) pumping concrete or grout into the resulting hole either during the second withdrawal phase or after the removal of the tool from the ground;

24. A method as claimed in claim 23, wherein said notional envelope exhibits two discontinuities in the outer edge of said closed geometric form.

25. A method as claimed in claim 23, wherein said notional envelope exhibits three discontinuities in the outer edge of said closed geometric form

26. A method as claimed in claim 23, wherein said notional envelope exhibits four discontinuities in the outer edge of said closed geometric form

27. A method as claimed in claim 23, wherein said notional envelope exhibits five discontinuities in the outer edge of said closed geometric form

28. A method as claimed in any one of claims 23 to 26, wherein said discontinuities, when viewed in a direction parallel to said longitudinal axis, are arcuate in shape.

29. A method of forming a concrete or grout pile, which method comprises the steps of:

i) applying to the ground an auger comprising a stem defining a longitudinal axis and a cutting element is disposed about said stem, wherein said cutting element includes at least one sliding element which is moveable from an open position, wherein said sliding element(s) is retracted so as to introduce a discontinuity in the radial edge of the cutting element, to a closed position, wherein said sliding element(s) extends to the extent that said cutting element has a continuous radial edge; ii) applying to said.auger forces, so as to facilitate a first penetration phase, wherein said sliding element(s) is in an open position, and a second withdrawal phase, wherein said sliding element(s) is in a closed position, said auger being removed from the ground during the withdrawal phase in a substantially vertical direction, such that the orientation of the discontinuity in the radial edge of the cutting element remains generally constant; and iii) pumping concrete or grout into the resulting hole either during the second withdrawal phase or after the removal of the tool from the ground.

30. A method of constructing a concrete or grout pile wall, which method comprises the steps of:

i) forming a series of female piles in accordance with any one of the methods of claims 19, 23 or 28, such that there exists a predetermined gap between adjacent female piles; ii) forming a series of male piles in said predetermined gaps between said female piles, so as to form a pile wall comprising a series of generally complimentary male and female piles.

31. A method according to claim 29, wherein said male piles are formed in accordance with any one of the methods of claims 19, 23 and 28.

32. A piled wall which is constructed by a method as defined in any one of claims 19, 23, 28 or 30.

33. A piling method substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.