GB2478362A

GB2478362A - A pile with a tube extending lengthwise of the pile

Info

Publication number: GB2478362A
Application number: GB1003754A
Authority: GB
Inventors: Simon CROOK
Original assignee: Shire Structures Ltd
Current assignee: Shire Structures Ltd
Priority date: 2010-03-06
Filing date: 2010-03-06
Publication date: 2011-09-07
Anticipated expiration: 2030-03-06
Also published as: GB2478362B; GB201003754D0

Abstract

A pile and method piling in which a central tube 9 extends lengthwise of the pile. A lower part of the tube may be surrounded by a filler material 10 (figure 3a), such as concrete, in contact with the surrounding ground 11 and an upper part of the tube 9 may be surrounded by a protective section comprising an outer sleeve 12 (figure 3a) and an inner sleeve 13 (figure 3a). The inner sleeve is spaced from the tube 9 and the filler material fills the gap therebetween. Opposed surfaces of the sleeves provide a slip surface that allows the outer sleeve to slide up and down the inner sleeve to accommodate movement of the ground, for example due to frost and temperature related heave of the ground, surrounding the upper part of the pile shaft. The tube may be left hollow or may be filled with concrete or a timber core 23 (figure 9). The pile may be filled via the tube 9 so that it fills from the bottom upwards. It may also have apertures or filling holes 19 (figure 6).

Description

IMPROVEMENTS IN OR RELATING TO SMALL DIAMETER PILES

This invention concerns improvements in or relating to piles. This invention has particular, but not exclusive, application for augerecl cantilever piles in clay subsoils used for the remedial support of building structures.

When piles are used to provide additional support to building structures they can be provided in pairs, directly below the existing foundation or as single piles alongside the existing foundation (cantilever piles). In addition to axial loads, cantilever piles must resist bending caused by the offset between the applied load and the supporting pile.

One method of forming piles in a clay soil is to auger a hole to the required depth and then fill this with a filler material such as concrete or grout. The pile is generally strengthened with solid steel reinforcing bars or rods to limit cracking and give tensile and bending capacity.

The equipment used to auger piles can be large and this makes it difficult/impractical to manoeuvre around existing buildings. In remedial applications the use of smaller equipment generally limits the diameter of the pile to 300mm or less. With small diameter augered piles there are difficulties in placing the concrete or grout at the base of the pile shaft (the concrete/grout can block partway down) and making the head of the support strong enough to resist the bending moments that are applied to cantilever piles (the sections are not wide enough to give much strength using traditional concrete reinforcement).

In a clay subsoil the upper clays can expand and contract with changes in the ground moisture content. This causes the ground level to rise and fall. The pile should preferably be separated from this active clay but be securely embedded in the lower stable clay.

The present invention seeks to overcome or at least mitigate one or more of the aforementioned disadvantages of small diameter augered piles.

In the first aspect of this invention, the pile is provided with a tube extending lengthwise of the pile.

The tube is preferably made with non corrosive materials such as plastics, for example a polyvinylchioride (pvc) or fibreglass but could also be steel with a protective coating that inhibits corrosion, for example paint or plastics.

The tube preferably replaces the solid reinforcing bars employed in the prior art and gives tensile, compressive and bending resistance to the pile.

The tube is preferably located at or towards the centre of the hole formed in the ground for the pile shaft.

The tube is preferably embedded within a filler material that surrounds the tube within the pile shaft. The filler material is preferably a flowable material that sets within the pile shaft to form a solid, rigid shell around the tube. The filler material may be concrete or grout although other materials such as resins or foams may be used.

The tube is preferably configured or adapted to improve its adhesion to the filler material. For example, the outer surface of the tube may have either a rough surface or external nibs that provide a "key" to the filler material.

The tube may remain empty so that the pile has a hollow central core. This may reduce the amount of filler material required.

Alternatively, the tube may be filled with filler material so that the pile has a solid, rigid core.

In at least one embodiment, the filler material is introduced through the tube so that the filler material is placed directly at the base of the pile shaft and back fills the space around the tube from the base towards the top of the pile shaft.

This overcomes the problems associated with placing filler material such as concrete or grout in deep small diameter shafts.

In a preferred embodiment, the tube has one or more holes between the ends of the tube through which filler material can flow prior to setting to provide a "key" to the filler material. Preferably, multiple holes are spaced apart along the length of the tube to allow filler material introduced through the tube can flow outwards so as to fill the pile shaft from different levels.

In the second aspect of this invention, an upper part of the pile has a protective section that protects the pile from movement of the surrounding ground.

The protective section preferably comprises two sleeves that extend lengthwise of the pile.

The sleeves are preferably arranged one within the other, i.e. an outer sleeve and an inner sleeve. The sleeves are preferably made with non corrosive materials such as plastics, for example pvc, or fibreglass but could also be steel with a protective coating, for example paint or plastics.

The inside surface of the outer sleeve and the outer surface of the inner sleeve are preferably smooth to give a slip surface such that the sleeves can slide relative to each other in the direction of their length.

The outer sleeve is gripped by the surrounding ground, for example clay, but any movement of the outer sleeve, for example due to ground movement such as caused by expansion/contraction of the clay, is not transferred to the inner sleeve because of the slip surface.

The Outer sleeve preferably provides the compressive strength to prevent lateral earth pressure being transferred to the inner sleeve. The inner tube preferably provides the bending strength to resist any applied moments.

The outer sleeve may be made of plastics and is preferably of sufficient thickness to resist compression forces. The inner sleeve may be made of fibreglass and is preferably of sufficient thickness to resist bending forces.

The inner sleeve may be stronger than the outer sleeve. The inner sleeve may be thicker than the outer sleeve.

The protective section may be provided in a pile according to the first aspect of the invention.

In the third aspect of this invention, the filler material comprises a resin or expanding foam to give enhanced adhesion to the soils.

The filler replaces the concrete or grout traditionally employed.

The filler may be provided in a pile according to either of the first and second aspects of the invention.

In the fourth aspect of this invention, the pile is provided with a hollow tube that extends lengthwise of the pile within a filler material.

The tube is preferably closed at its base so as to remain empty when the filler material is introduced to fill the pile shaft.

The hollow tube significantly reduces the amount of filler material needed to fill the pile shaft.

The hollow tube may be employed in any of the preceding aspects of the invention.

In the fifth aspect of this invention, the pile is provided with a central timber core that extends lengthwise of the pile within a filler material.

The timber core significantly reduces the amount of filler material needed to fill the pile shaft. The filler material protects the timber from decay.

The timber core may be employed in any of the preceding aspects of the invention.

In the sixth aspect of this invention, a method of piling is provided comprising the steps of providing a pile tube, positioning the pile tube to extend lengthwise of a pile shaft so that a lower end of the pile tube is adjacent or near to the base of the pile shaft and the pile tube is spaced from the wall of the pile shaft, providing a flowable filler material, delivering the flowable filler material through the pile tube to the base of the pile shaft and back filling the pile shaft around the pile tube, and allowing the flowable material to set to form a substantially solid shell around the tube and a substantially solid core within the tube.

The filler material may be a concrete or grout. Alternatively, the filler material may be a resin or foam material.

The pile tube may have one or more holes spaced from the lower end through which the filler material can pass. The holes may be of any suitable size and shape.

The method may include providing a protective section at an upper end of the pile shaft. The protective section may comprise a sleeve assembly including an outer sleeve and an inner sleeve that are slidable relative one another. The pile tube preferably extends within the inner sleeve and the filler material fills the gap between the pile tube and inner sleeve.

The invention will now be described in more detail by way of example only with reference to the accompanying drawings in which like reference numerals are used to indicate corresponding parts throughout and wherein: Figures la,lb,lc,ld show typical prior art remedial pile arrangements; Figures 2a, Zb show sections through typical prior art augered piles; Figure 3a shows a pile according to a first embodiment of this invention; Figure 3b is a section on the line 1-1 of Figure 3a; Figure 3c is a section on the line 2-2 of Figure 3a; Figure 4 shows a modification to the pile of Figure 3a; Figure 5 shows the method of filling the pile shaft from the base using the pile of Figure 3a; Figure 6 shows a modification to the pile of figure 3a; Figure 7 shows a resin or expanding foam filler; Figure 8 shows a pile with a hollow central core; and Figure 9 shows a pile with a timber core.

Referring first to Figures la,lb,lc,ld four typical prior art remedial pile arrangements are shown in which the applied load 1 results in compression 2 and/or tension 3 loads in the piles. The cantilever pile (Figure id) also needs to resist the bending 4 applied to the pile head.

Figures 2a,2b show sections through typical prior art augered piles. Figure 2a shows a concrete grout infill 5 and multiple reinforcing bars 6 arranged in a circle so that each bar is covered by the infill 5. The distance between the bars 6 and the outer surface of the pile shaft is referred to as the cover 7. As the pile diameter reduces, it is not possible to maintain the cover 7 without reducing the number of bars 6 and only a single reinforcing bar 6 can be used with small diameter piles as shown in Figure 2b. A single reinforcing bar 6 does not, however, provide the bending capacity required for cantilever piles.

Figures 3a,3b,3c show a pile according to this invention. The pile includes a central tube 9 that extends lengthwise of the pile shaft. In the lower part of the pile shaft, the central tube 9 is surrounded by a filler 10 in contact with the soil 11. The central tube 9 is made from a non corrosive material such as a plastics or fibre glass that allows the cover 7 to be reduced.

In the upper part of the pile shaft, the pile has a protective Section comprising two sleeves, an outer sleeve 12 and an inner sleeve 13 of which the opposed inner and outer surfaces provide a smooth slip surface such that the outer sleeve 12 can slide up and down relative to the inner sleeve 13. In this embodiment, the inner sleeve 13 is slightly longer than the outer sleeve 12 but this is not essential.

The central tube 9 extends within the inner sleeve 13 and is radially spaced therefrom. The filler 10 fills the gap between the central tube 9 and the soil 11 in the lower part of the pile shaft and also fills the gap between central tube 9 and the inner sleeve 13 of the protective section in the upper part of the pile shaft. The protective section may be configured and/or adapted to prevent flowable filler material penetrating between the sleeves 12,13. For example the ends of the sleeves may be taped together for assembly and installation purposes with the tape being made of a material that degrades in situ and/or breaks to allow relative sliding movement between the sleeves 12,13.

The pile is anchored to the soil in the lower part of the pile shaft and can accommodate movement in the soil surrounding the upper part of the pile shaft by axial sliding movement of the outer sleeve 12 on the inner sleeve 13, for example to accommodate expansion/contraction of a clay soil surrounding the pile shaft.

The outer sleeve 12 is preferably capable of preventing lateral earth pressure being transferred to the inner sleeve. The inner sleeve 13 is preferably capable of resisting bending loads. The outer sleeve 12 may be made of plastics, optionally reinforced. The inner sleeve 13 may be made of fibreglass, optionally reinforced. The outer sleeve may be thinner 12 than the inner sleeve 13.

The central tube 9 may be configured and/or adapted to key the filler material to the outer surface in at least the lower part of the pile shaft and preferably in the upper and lower parts of the pile shaft. For example, the outside surface of the central tube may be provided with ribs 15 (Figure 4) or a rough surface to aid adhesion to the filler 10.

Figure 5 shows the method of introducing the filler 10 through the central tube 9. The filler 10 is preferably a flowable material that passes down the inside of the central tube 9 from the top 16 and flows out from the bottom of the tube 9 to flow up and around the tube 9 from the base 17 of the pile shaft as indicated by the arrows.

Delivering the filler to the base 17 of the pile and back filling the pile shaft from the base 17 ensures the space around the tube 9 is completely filled over the whole length of the pile shaft. The central tube 9 is also filled with the filler 10.

On setting, the filler 10 forms a solid pile with a solid reinforced core provided by the central tube 9 and the filler 10 inside the tube 9. The filler 10 also forms a solid shell around the core.

Figure 6 shows a modification in which the central tube 9 is provided with multiple holes 19 spaced apart in the vertical direction in the lower part of the pile shaft to allow the filler to run into the pile shaft at different levels. The number of levels employed may be varied. For example, long piles may employ more levels. Any level may have more than one hole spaced apart in the circumferential direction.

The filler 10 may be concrete or grout that sets to form a solid, rigid pile shaft.

Alternatively, the concrete or grout may be replaced with any other suitable filler material including but not limited to a resin or foam material such as indicated by reference numeral 20 in Figure 7. Such materials are preferably also flowable prior to setting. Foam materials may include expanding foam materials The central tube 9 may be used to deliver the filler material to the base of the pile shaft and provide a solid core when the filler within the tube 9 sets.

Alternatively, the central tube may be closed at the lower end as indicated by reference numeral 21 in Figure 8 and the filler 22 introduced around the outside of the central tube 9 so that only the gap between tube 9 and the ground 11 in the lower part of the pile shaft and between the tube 9 and the inner tube 13 of the protective section in the upper part of the pile shaft is filled, i.e. the central tube 9 remains unfilled or hollow.

The central tube 9 may be replaced with a solid timber core 23 as shown in Figure 9. The filler 24 surrounds the timber and protects it from decay. Any of the filler materials described previously may be employed. The timber core 23 may be treated to enhance protection against decay. The pile with timber core 23 may be provided with a protective section in the upper part of the pile shaft as described previously.

It will be understood the invention is not limited to the embodiments above-described. For example, in some embodiments the assembly of outer and inner tubes at the upper end of the pile shaft may be omitted and the filler fills the gap between the central tube 9 and the soil over substantially the whole length of the pile shaft. In other embodiments, the central tube may be omitted and optionally replaced by any other suitable reinforcement embedded within the filler such as reinforcing bars or rods. Any of the features of the invented pile described herein may be employed separately or in combination with any other feature(s) and the invention extends to and includes all such arrangements.

Other modifications will be apparent to those skilled in the art.

Claims

CLAIMS1. A pile provided with a tube extending lengthwise of the pile.
2. A pile according to claim 1 wherein the tube is made of non corrosive material.
3. A pile according to claim 2 wherein the tube is made of as plastics or fibreglass.
4. A pile according to claim 1 wherein the tube is made of steel with a protective coating that inhibits corrosion.
5. A pile according to claim 1 wherein the protective coating is paint or plastics.
6. A pile according to any preceding claim wherein the tube replaces the CO solid reinforcing bars and gives tensile, compressive and bending resistance to the pile. CO 20
7. A pile according to any preceding claim wherein, in use, the tube is located at or towards the centre of a hole formed in the ground for the pile shaft.
8. A pile according to claim 7 wherein, in use, the tube is embedded within a filler material that surrounds the tube within the pile shaft.
9. A pile according to claim 8 wherein the filler material is a flowable material that sets within the pile shaft to form a solid, rigid shell around the tube.
10. A pile according to claim 8 or claim 9 wherein the filler material is concrete or grout or resins or foams.
11. A pile according to any of claims 8 to 10 wherein the tube is configured or adapted to improve its adhesion to the filler material.
12. A pile according to claim 11 wherein the outer surface of the tube has either a rough surface or external nibs that provide a "key" to the filler material.
13. A pile according to any of claims 8 to 12 wherein, in use, the tube remains empty so that the pile has a hollow central core.
14. A pile according to any of claims 8 to 12 wherein, in use, the tube is filled with filler material so that the pile has a solid, rigid core.
15. A pile according to claim 14 wherein, in use, the filler material is introduced through the tube so that the filler material is placed directly at the base of the pile shaft and back fills the space around the tube from the base (Y) towards the top of the pile shaft.

(Y)
16. A pile according to claim 15 wherein the tube has one or more holes Q 20 between the ends of the tube through which filler material can flow prior to setting to provide a key to the filler material.
17. A pile according to claim 16 wherein multiple holes are spaced apart along the length of the tube to allow filler material introduced through the tube to flow outwards so as to fill the pile shaft from different levels.
18. A pile according to any preceding claim wherein an upper part of the pile has a protective section that protects the pile from movement of the surrounding ground.
19. A pile according to claim 18 wherein the protective section comprises two sleeves that extend lengthwise of the pile.
20. A pile according to claim 19 wherein the sleeves are arranged one within the other.
21. A pile according to claim 19 or claim 20 wherein the sleeves are made of non corrosive material.
22. A pile according to claim 21 wherein the sleeves are made of plastics or fibreglass.
23. A pile according to claim 19 or claim 20 wherein the sleeves are made of steel with a protective coating.
24. A pile according to claim 23 wherein the protective coating is paint or plastics.
25. A pile according to any of claim 19 to 24 wherein an inside surface of an (Y) outer one of the sleeves and an outer surface of an inner other of the sleeves are Q smooth to give a slip surface such that the sleeves can slide relative to each (Y) other in the direction of their length. 0 20
26. A pile according to claim 25 wherein the outer sleeve is gripped by the surrounding ground such that any movement of the outer sleeve due to ground movement is not transferred to the inner sleeve because of the slip surface.
27. A pile according to claim 25 or claim 26 wherein the outer sleeve provides compressive strength to prevent lateral earth pressure being transferred to the inner sleeve.
28. A pile according to any of claims 25 to 27 wherein the inner sleeve provides bending strength to resist any applied moments.
29. A pile according to any of claims 25 to 28 wherein the outer sleeve made of plastics and is of sufficient thickness to resist compression forces.
30. A pile according to any of claims 25 to 29 wherein the inner sleeve is made of fibreglass and is of sufficient thickness to resist bending forces.
31. A pile according to any of claims 25 to 30 wherein the inner sleeve is stronger than the outer sleeve.32. A pile according to any of claims 25 to 31 wherein the inner sleeve is thicker than the outer sleeve.
32. A pile having a protective section that protects an upper part of the pile from movement of the surrounding ground.
33. A pile having a filler material that comprises a resin or expanding foam to give enhanced adhesion to the soils.

(Y)
34. A pile having a hollow tube that extends lengthwise of the pile within a Q filler material. C)

Q 20
35. A pile provided with a central timber core that extends lengthwise of the pile within a filler material.
36. A method of piling is provided comprising the steps of providing a pile tube, positioning the pile tube to extend lengthwise of a pile shaft so that a lower end of the pile tube is adjacent or near to the base of the pile shaft and the pile tube is spaced from the wall of the pile shaft, providing a flowable filler material, delivering the flowable filler material through the pile tube to the base of the pile shaft and back filling the pile shaft around the pile tube, and allowing the flowable material to set to form a substantially solid shell around the tube and a substantially solid core within the tube.
37. A method according to claim 36 wherein the filler material is a concrete or grout or resin or foam material.
38. A method according to claim 36 or claim 37 wherein the pile tube has one or more holes spaced from a lower end through which filler material can pass.
39. A method according to any of claims 36 to 38 wherein a protective section is provided at an upper end of the pile shaft.
40. A method according to claim 39 wherein the protective section comprises a sleeve assembly including an outer sleeve and an inner sleeve that are slidable relative one another.
41. A method according to claim 40 wherein the pile tube extends within the inner sleeve and the filler material fills the gap between the pile tube and inner sleeve.

(Y)
42. A pile substantially as hereinbefore described with reference to Figures 3 to 9 of the accompanying drawings. C)
43. A method of piling substantially as hereinbefore described with reference to Figures 3 to 9 of the accompanying drawings.