GB2436845A

GB2436845A - Webbed foundation piles

Info

Publication number: GB2436845A
Application number: GB0706849A
Authority: GB
Inventors: Peter Keith Woodward; Patrick Keith Steuart
Original assignee: PICOPILE TECHNOLOGIES Ltd
Current assignee: PICOPILE TECHNOLOGIES Ltd
Priority date: 2006-04-07
Filing date: 2007-04-10
Publication date: 2007-10-10
Also published as: GB0706849D0; GB0607007D0

Abstract

An elongate foundation pile having a longitudinal axis and a plurality of web, fin or blade members extending radially outwardly from the axis, wherein one or more of the web members 114 has at least one further projecting member 116 joined to an edge opposite the edge joined to the central body 112 of the pile. The webs 114 may be joined to the pile body 112 and each other by a mechanical connector 113,115 and the central body 112 of the pile may be hollow.

Description

2436845

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FOUNDATION PILEa

The present invention relates to foundation piles. More specifically, the present invention relates to foundation 5 piles for supporting relatively light structures in soft soils.

Scarcity and cost of suitable land is leading land developers and construction companies to develop marginal 10 sites which were not previously considered suitable for development. Such sites commonly contain deposits of soft clays and organic soils and are found in most European Union countries. A conventional method of building on such compressible soils has been to use unreinforced concrete, 15 reinforced concrete or steel foundation piles. These piles are bored or driven through the softer upper layers and embedded in the hard layers lying beneath. This technique is expensive in that heavy duty piling machinery is required to install the piles into the hard layers. The 20 relatively high cost means that such a technique is not cost effective when it is light structures, such as houses, which are to be built on these foundations. Alternative solutions such as pre-loading, vibro-replacement, vibro-displacement and soil mixing are time-consuming and are not 25 especially effective in deep layers of soft soil.

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It is an aim of the present invention to obviate or mitigate disadvantages of these known techniques.

5 According to the present invention, there is provided an elongate foundation pile having a longitudinal axis and a plurality of web members extending radially outwardly from the axis, wherein one or more of said web members has one or more projecting members projecting outwardly therefrom.

10

Preferably, each web member has a first edge attached to the first edges of the other web members, and a second edge remote from the first edge, and wherein said projecting members project from the second edge.

15

Alternatively, the pile includes an elongate body and each web member has a first edge attached to the body and a second edge remote from the body, and wherein said projecting members project from the second edge.

20

Preferably, each web member has one or more projecting members projecting outwardly therefrom.

25

In one embodiment, one or more of the projecting members projects in a plane perpendicular to the plane of its respective web member. Most preferably, the projecting

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members project outwardly from either side of the respective web member.

In an alternative embodiment, one or more of the web 5 members has two projecting members projecting in planes which are between 90 and 180 degrees relative to the plane of their respective web member. Most preferably, the projecting members project in planes which are between 100 and 150 degrees relative to the plane of their respective 10 web member.

Preferably, the body, if present, web members and projecting members are integrally formed. Preferably, the web members and projecting members extend along the length 15 of the body.

The pile is manufactured from reinforced concrete. In an alternative embodiment, the pile is manufactured from steel. In another alternative embodiment, the pile is 20 manufactured from a fibre-reinforced composite material.

Preferably, the body has first and second ends, the first end having a first connecting means and the second end having a second connecting means, wherein the first and 25 second connecting means are adapted to connect the pile to one or more adjacent piles. Preferably, the connecting

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means are mechanical connecting means.

Preferably, the body is hollow. Most preferably, the hollow body is provided with a number of drainage apertures 5 therein, the apertures adapted to allow fluid flow from the exterior of the body to the interior.

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the 10 accompanying drawings, in which:

Figures 1 (a) - (g) are end views of various preferred embodiments of a foundation pile;

Figures 2(a)-(c) are views of the stages of a method of 15 installing any of the foundation piles of Figure 1 into the ground;

Figures 3(a) and (b) are schematic views of any of the foundation piles of Figure 1 in use; and Figures 4 and 5 are end views of further preferred 20 embodiments of a foundation pile.

Figures 1(a)-(g) show various different embodiments of a pre-fabricated foundation pile in accordance with the present invention. Each pile, shown end on in the figures, 25 has a body 12 and a number of wings, or web members, 14 extending radially outwardly from the body 12. At the end

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of each wing 14 remote from the body 12 is attached a friction member, or projecting member, 16; or two projecting members 16, 18. The body 12, wings 14 and projecting members 16 (or projecting members 16, 18) may be 5 formed separately and attached to one another, but preferably they are integrally formed with one another. The body 12 is preferably a hollow cylinder, although it may equally be solid, or else filled with material, and have a different cross-sectional shape if desired. Each wing 14 10 and projecting member preferably extends along the entire length of the body 12.

A first embodiment of the pile, shown in Figure 1(a), has four wings 14 extending outwardly from the body 12. Each 15 wing 14 is equidistantly spaced about the circumference of the body 12, such that the pairs of wings 14 lying opposite one another are coplanar. At the end of each wing 14, the projecting members 16 extend away from their respective wings 14 in a plane substantially perpendicular to the 20 plane of the wing 14. That is, the angle A between the projecting members 16 and their wings 14 is substantially 90°. In the illustrated embodiment, the projecting members 16 extend either side of the wing 14, thereby forming a "T" shape at the end of each wing 14. The length of the 25 projecting member is preferably half the length of its respective wing. However, the projecting members 16 may

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equally only project on one side of the wing 14 if desired. Figure 1(b) shows a second embodiment of the pile, in which three wings 14 are equidistantly spaced around the circumference of the body 12. Again, each wing 14 has a 5 projecting member 16 projecting substantially perpendicular to the plane of the wing 14. The angle A between wing 14 and respective projecting member 16 is again substantially 90°, and the projecting members 16 are again half the length of their wings 14.

10

A third embodiment of the pile is shown in Figure 1(c), The third embodiment is similar to the first embodiment in that it has four wings 14 equidistantly spaced about the circumference of the body 12. Where the third embodiment 15 differs is that instead of a single projecting member at the end of each wing 14 there are two projecting members 18,20. in this embodiment, the projecting members 18,20 are not perpendicular to the plane of the wing 14. Instead,

each projecting member 18,20 is at an angle A in the range 20 90-180° to the plane of the wing 14. Preferably, the angles A are in the range 100-150° and an angle B between the planes of the two projecting members 18,20 is in the range 60-160°, Most preferably the angles A are substantially 135° and the angle B is substantially 90°, Angles in this 25 preferred range give the optimum amount of side friction to the piles when installed in soft soil. Each projecting

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member 18,20 is preferably half the length of their respective wing 14. The same arrangement of wings 14 and projecting members 18,20 is provided in a fourth embodiment, as seen in Figure 1 (d). However, in the fourth 5 embodiment only three wings 14 are provided equidistantly about the circumference of the body 12.

Figure 1(e) shows a fifth embodiment of the pile. This embodiment is substantially the same as that of the second 10 embodiment shown in Figure 1 (b). The only difference in the fifth embodiment is that the projecting members 16 are substantially the same length as their respective wings 14.

The sixth and seventh embodiments of the pile, as shown in 15 Figures 1(f) and 1(g) respectively, are substantially the same as the third and fourth embodiments shown in Figures 1(c) and 1(d). However, the angles A and B of the sixth and seventh embodiments are each substantially 120°.

20 In each of the illustrated embodiments, the diameter of the body 12 is preferably substantially the same as the length of each wing 14.

The illustrated piles may be manufactured from a wide 25 variety of materials such as aluminium, alloys of magnesium or aluminium, carbon fibre reinforced materials, galvanised

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or non-galvanised steel, or timber. Preferably, the piles are manufactured from one of pre-stressed or reinforced concrete, steel, plastics or a fibre reinforced material. Examples of suitable fibre reinforced materials are those 5 manufactured by Fibreforce Limited of Runcorn, United Kingdom. This material comprises glass, carbon or aramid fibres embedded in a suitable polymer matrix.

Figures 2(a)-(c) show the stages for installing one of the 10 piles of the present invention into the ground.

Installation is preferably facilitated by way of a driving head 22 which is attached to the arm 26 of a mechanical excavator. The driving head 22 is removably attached to the arm 26 by a pivot pin 23 which allows the driving head 22 15 to pivot relative to the arm 26 whilst remaining connected thereto. Prior to installation of the pile, generally designated 10, the upper end of the pile 10 is received inside the driving head 22, as shown in Figure 2 (a). The pile 10 is then attached to the driving head 22 by a chain 20 24 connected to the pile at a connection point 28. Thus, when the driving head 22 is lifted by the arm 26, the pile 10 will also be lifted. The driving head also includes a load cell (not shown) located between the upper end of the pile 10 and the end of the driving head 22. The load cell 25 ensures that the end of the pile is not damaged by the driving head 22 during installation.

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Figure 2(b) shows the arrangement of the arm 26, driving head 22 and pile 10 immediately prior to installation. The chain 24 is disconnected from the pile 10 at the connecting 5 point 28 and a retrieval line 30 is attached to the chain 24 to ensure that the chain 24 is pulled clear during installation. The excavator arm 26 then begins to push downwards, along with the driving head 22, and the pile enters the soil, as shown in Figure 2(c). As the pile 10 enters the ground, the overall cross-sectional shape with wings and projecting members provides a high ratio of cross-sectional perimeter to cross-sectional area to ensure that soil disturbance is minimal compared with conventional cylindrical or cuboidal piles.

15

Figures 3(a) and 3(b) show schematically an example of how the piles could be used to support the foundation of a light structure, such as a house. Firstly, groundworks are undertaken to excavate a cavity 32 where the structure is 20 to be located. The piles 10 are then installed into the ground through the cavity as described above. As shown with particular reference to the sectional view of Figure 3(b), the piles 10 are preferably installed in rows and columns of equidistant spacing. If necessary, secondary support 25 piles 40 may also be installed in the gaps left between the columns of piles 10. Once installed in the ground, the

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upper portion of the piles 10 will remain exposed in the cavity 32. A concrete foundation 35 is then poured into the cavity 32, covering the exposed parts of the piles 10, and is allowed to set. The piles 10 thereby provide the 5 concrete foundation 35 with stability and allow the structure to be built upon the foundation 35.

Figures 4 and 5 show further preferred embodiments of a foundation pile in accordance with the present invention. 10 In Figure 4, the pile comprises a body 112 attached to which are a number of female mechanical connectors 113 spaced equidistantly around the circumference of the body 112. The connectors 113 preferably extend longitudinally along the length of the body 112. A number of web members 15 114 are provided for attachment to the body 112. Each web member 114 has a first end provided with a male mechanical connector 115 adapted to be received in one of the corresponding female connectors 113 of the body 112. The second ends of the web members 114 are provided with 20 projecting members 116 in the same manner as with the previously described embodiments. Figure 4 also shows alternative web members 120,122 which can be used in conjunction with the body 112. With the alternative web members 120,122, the projecting members at the second end 25 of the web member 120,122 form a further female connector 123. This allows further web members 114,120,122 to be

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attached in a similar manner to sheet piles. As seen in Figure 4, the web members 122 can be provided bent into different shapes dependent on requirements.

5 Figure 5 shows a similar arrangement where the female connectors 113' are located in the body 112' as opposed to external thereof. The web members 122' are the same as those illustrated in Figure 4 with male connectors 115' at the first end of the web member 122' and projecting members 10 forming a female connector 123' at the second end. Again, this allows further web members to be attached together to form a network of members.

It will be appreciated that for the embodiments described 15 above in the discussion of figures 4 and 5 the respective locations of the male and female connectors is not critical; whilst these are described as being associated with the web members and body respectively, they could equally be associated with the body and web members 20 respectively.

The pile of the present invention relies solely on side friction and is not intended to offer an end bearing resistance. As a result, it does not need to be pushed 25 against or into the harder substratum below softer soil layers. By only locating in the soft soil layers, the piles

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do not need to be bored, impact-driven or vibrated into the ground. They can simply be pushed during installation,

which means that the pushing force can be measured during installation. This measurement gives a direct indication of 5 pile capacity and thus a very good indication of the load carrying capacity of each installed pile, Not having to use impact-driving, vibration or boring techniques also has the environmental benefits of limited soil disturbance and noise generation during installation.

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The projecting members at the end of the wings increase the surface area of the pile for increased side friction resistance and provide reinforcement to avoid buckling of the wings and of the pile during installation. The wings 15 themselves provide surface area for contact friction with the soil. The overall pile shape with wings and projecting members provides a large surface area for contact friction with the soil, high resistance to buckling and minimal disturbance of the soil during installation.

20

The piles are preferably provided in single lengths sufficient for the support of relatively light structures, Alternatively, in applications where headroom for installation is limited, the piles can be provided in 25 shortened lengths. In this case, each end of the pile would be provided with connecting means adapted to co-operate

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with the connection means on an adjacent pile in order to connect the two together. Most preferably, the connecting means would be a mechanical connecting means.

5 Although illustrated as having an elongate body portion, the piles need not have a body portion, although it is preferred. In the instances where there is no body, the web members are simply attached to one another along their first edges. In instances where the pile does have a body, 10 the body may be solid, but may alternatively be hollow. In the case where the body is hollow, drainage apertures can be provided in the wall of the body to allow fluid communication between the exterior and interior of the body. Such an arrangement can assist dissipation of excess 15 pore water pressure around the pile by allowing water to flow into the body and to rise up the inside of the body towards the ground surface.

Although illustrated in Figure 3(a) as having a direct 20 connection between the top of the pile and the strip, pad or slab foundation of the structure being supported, the piles may be installed with the top of the pile at a depth below the foundation and a connecting shaft used to transfer the foundation load to the pile.

25

It should also be appreciated that the piles of the present

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invention are not limited to having projecting members on the end of each web member. Some web members may have projecting members whilst others do not. Similarly,

although each illustrated example of the pile shows 5 identical projecting members on each web member, the web members on the same pile may have different types of projecting member. For example, one web member may have the "T" shaped projecting member at 90° whilst the neighbouring web members may have the two projecting members in the 90-10 180° range as described above.

It will also be appreciated that the male and female connector arrangement illustrated in Figures 4 and 5 could be reversed, with the body having male connectors 15 projecting therefrom, and the web members having corresponding female connectors at the first end thereof.

Although it is preferable for the pile of the present invention to be formed from a single material, they could 20 also be formed from a selection of materials. For example, the body of the pile could be made from a plastics material whilst the web members and projecting members could be made from a metal. Furthermore, the web members do not need to extend longitudinally along the whole length of the body 25 although they may do so.

Where the entire pile, or at least the web members and

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projecting members, are made from a plastics material, the leading edges of the members (i.e. those edges which will enter the ground first) can be provided with a metal reinforcement member to protect the leading edges from 5 damage during installation.

These and other modifications and improvements may be incorporated without departing from the scope of the invention.

Claims

CLAIMS -16-

1. An elongate foundation pile having a longitudinal axis and a plurality of web members extending 5 radially outwardly from the axis, wherein one or more of said web members has one or more projecting members projecting outwardly therefrom.

2. The elongate foundation pile as claimed in claim 1

10 wherein each web member has a first edge attached to the first edges of the other web members, and a second edge remote from the first edge, and wherein said projecting members project from the second edge.

15

3. The elongate foundation pile as claimed in claim 1 wherein the pile includes an elongate body and each web member has a first edge attached to the body and a second edge remote from the body, and wherein said

20 projecting members project from the second edge.

4. The elongate foundation pile as claimed in any one of claims 1 to 3 wherein each web member has one or more projecting members projecting outwardly 25 therefrom.

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5. The elongate foundation pile as claimed in any one preceding claim wherein one or more of the projecting members projects in a plane perpendicular to the plane of its respective web member.

5

6. The elongate foundation pile as claimed in any one of claims 1 to 4 wherein one or more of the web members has two projecting members projecting in planes which are between 90 and 180 degrees relative

10 to the plane of their respective web member.

7. The elongate foundation pile as claimed in any one preceding claim wherein the projecting members project outwardly from either side of the respective 15 web member.

8. The elongate foundation pile as claimed in any one preceding claim wherein the projecting members project in planes which are between 100 and 150 20 degrees relative to the plane of their respective web member.

9. The elongate foundation pile as claimed in any one preceding claim wherein the web members and

25 projecting members extend along the length of the body.

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10. The elongate foundation pile as claimed in any one preceding claim, which is manufactured from aluminium, an alloy of magnesium or aluminium, 5 galvanised or non-galvanised steel, timber, pre-

stressed or reinforced concrete, plastics or a fibre reinforced material.

11. The elongate foundation pile as claimed in any one 10 preceding claim, which is manufactured from reinforced concrete.

12. The elongate foundation pile as claimed in any one preceding claim, which is manufactured from steel.

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13. The elongate foundation pile as claimed in any one preceding claim, which is manufactured from a fibre reinforced material.

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14. The elongate foundation pile as claimed in any one preceding claim, which is manufactured from a carbon fibre reinforced material.

25

15.

The elongate foundation pile as claimed in any one preceding claim, which is manufactured from a fibre-reinforced composite material.

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10

15

16. The elongate foundation pile as claimed in any one of claims 3 to 15 wherein the body is hollow.

17. The elongate foundation pile as claimed in claim 16 wherein the hollow body is provided with a number of drainage apertures therein, the apertures adapted to allow fluid flow from the exterior of the body to the interior.

18. The elongate foundation pile as claimed in any one of claims 3 to 17 wherein the diameter of the body is substantially the same as the length of each web member.

19. The elongate foundation pile as claimed in any one of claims 3 to 18 wherein the body has first and second ends, the first end having a first connecting means and the second end having a second connecting 20 means, wherein the first and second connecting means are adapted to connect the pile to one or more adjacent piles.

25

20.

The elongate foundation pile as claimed in claim 19 wherein the connecting means are mechanical connecting means.

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21. The elongate foundation pile as claimed in any one preceding claim wherein web members and projecting members are integrally formed.

5

22. The elongate foundation pile as claimed in any one of claims 3 to 21 wherein the body, web members and projecting members are integrally formed.

10

23. The elongate foundation pile as claimed in any one of claims 3 to 18 wherein one or more web members are attached to the body by location of a male mechanical connector in a female mechanical connector, wherein either the male mechanical 15 connector is provided with the first edge and the female mechanical is provided within or attached to the body, or the male mechanical connector is provided within or attached to the body and the female mechanical connector is provided with the 20 first edge.

24. The elongate foundation pile as claimed in claim 23

wherein said mechanical connectors provided within or attached to the body extend longitudinally along 25 the length of the body.

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25. The elongate foundation pile as claimed in claim 23 or claim 24 wherein all of said web members are attached to the body by location of a said male mechanical connector in a said female mechanical

5 connector.

26. The elongate foundation pile as claimed in claim 25 wherein said mechanical connectors provided within or attached to the body are spaced equidistantly

10 around the circumference of the body.

27. The elongate foundation pile as claimed in any one of claims 23 to 26 wherein one or more projecting members forms a further female or male connector.

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28. The elongate foundation pile as claimed in claim 27 wherein each projecting members forms a further female or male connector.

20

29. The elongate foundation pile as claimed in claim 27 or claim 28 further comprising one or more additional web members attached to said further female or male connectors.

25

30. An elongate foundation pile substantially as hereinbefore described with reference to the

accompanying drawings