BACKGROUND OF THE INVENTION [0001] The present disclosure relates to piling.

[0002] The present invention concerns piling. More particularly, but not exclusively, this invention concerns a pile assembly. The invention also concerns a foundations system, a method of making a pile assembly and a method of making a foundation system.

[0003] Piles are used to provide support to overlying structures, especially where the underlying ground does not itself provide suitable support for the overlying structure. Hollow piles are also known. WO 2008/047161 discloses a method for making a hollow pile, by filling a bore with uncast concrete, and inserting a cavity forming means within the bore. Such methods require casting on site which requires delivery of wet concrete, which may be undesirable. GB2580041 describes a hollow pile made from a plurality of pre-formed pile sections that are stacked to form the pile. The use of pre-formed pile sections permits quality checking of pile sections prior to transportation, and dispenses with the need to transport wet concrete to the site. However, the use of pre-formed pile sections does not necessarily provide good bending resistance.

[0004] The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved pile assembly.

SUMMARY OF THE INVENTION

[0005] In accordance with a first aspect of the present invention, there is provided a pile assembly located within a bore, the pile assembly comprising: a hollow pile comprising a plurality of pre-formed pile sections that form a pile wall surrounding a cavity, to define a hollow interior of the pile; and a plurality of tensioning members for drawing the pre-formed pile sections together. [0006] The applicant has discovered that it is possible to make a pile from pre-formed pile sections and to use tensioning members to draw those pre-formed pile sections together and thus tighten them, thereby providing bending and tension resistance. Furthermore, the use of the tensioning members means that it is possible to provide bending resistance without the need for mechanical joints between the pile sections. Tensioning members may also be used to facilitate placement of the pile sections.

[0007] At least one, more than one and optionally each of the tensioning members may be in tension so as to draw the pre-formed pile sections together. It is possible to use tensioning members to facilitate placement and stacking of the pile sections without being used to draw the pre-formed pile sections together.

[0008] The plurality of pile sections may include pile sections that have different widths from each other. The pile may taper in width, for example so that it has a smaller width at its base and a larger width at its top (or vice versa). Thus, the pile sections forming the pile may increase in width with height up the pile (or vice versa). The pile sections may have the same or a varying internal width (e.g. internal diameter). A taper in the pile may be achieved by varying the thickness of the wall of adjacent pile sections. In embodiments comprising a channel configured to allow the transport of a curable liquid material along the length of the column, a channel in each pile section may be at the same spacing (e.g. radius) from the centre of the pile. That spacing may be defined by the smallest width pile section.

[0009] The pile sections may be tubes. The tubes may have a constant inner width along the height of the pile (even in embodiments in which the outer width of the tubes is not the same along the height of the pile, for example where the tubes forming the pile increase in width with height up the pile). The tubes may have an internal width that is at least half their external width.

[0010] The pile sections may be circular in cross-section. The pile sections may be polygonal in cross-section. [0011] The pile sections may comprise elements (for example, castellations) at each of their axial ends, the axial end elements being sized and shaped to interlock with the corresponding axial end elements of another of the pile sections.

[0012] The pile sections may comprise a plurality of section components. Each pile section may for example be made from between 2 and 4 section components. The plurality of section components may be identical to each other. The section components may be segments of an annulus. Providing section components in each pile section may facilitate efficient transport of the components of the pile (compared to transporting fully assembled, or cast, pile sections).

[0013] Each pile section, and preferably each pile section component, may comprise elements (for example, tongue-and-groove elements) at each axial end, sized and shaped to interlock with the corresponding elements of another of the pile section/pile section component. The method may comprise the step of joining adjacent pile sections together, for example with a fastener.

[0014] At least some of the pile sections may include a raised and/or indented pattern on their outer surfaces, i.e. a textured pattern. The pattern may be irregular. Alternatively, the pattern may be a regular pattern of repeating shapes. Such an arrangement may facilitate effective binding of a curable liquid to the outer surface of the sections and/or increase the resistance between the outer surface of the pile and the cured liquid. At least some of the sections may include protrusions on their outer surface, which may be arranged in a regular pattern. The protrusions may be dome-shaped, or of other geometries e.g. curved or square.

[0015] At least some of the sections may include channels configured to allow the transport of a curable liquid material along the length of the column. The channels may be within the sections, for example entirely enclosed in the solid material of the sections (save at inlets and outlets). The channels may be wholly or partly on the surface of the sections, for example the channels may be exposed channels running along a face of the sections. The channels may comprise transport channels in fluid communication with outlet channels. The transport channels may be vertical. The outlet channels may be inclined or horizontal. The transport channels may be in fluid communication with the outlet channels. There may, for example, be a multiplicity, for example 1 to 10, transport channels in each pile section. The transport channels may be at the same radial position in each pile section in the pile.

[0016] The pile sections may be formed from any type of cementitious material, such as concrete, for example pre-cast concrete. Use of pre-cast concrete has the advantage that the pile sections (or the section components) can be manufactured remotely from the site of the bore and then transported to the bore for use. Manufacturing the pile sections (or the section components) as pre-cast concrete, before their use in the bore, has the advantages of a) better quality assurance in a controlled environment, b) greater precision, and c) the opportunity to create bespoke surface qualities and that quality checks can be carried out on them before their installation in the ground. The pile sections may be reinforced concrete. At least two of the pile sections may have mutually- different lengths (length being measured along the longitudinal axis of the pile section). The use of different lengths of pile section facilitates the construction of a pile the height of which may be tailored to take into account the actual depth of the bore. Typically, a bore may be slightly (250-500mm) deeper than intended. It is therefore useful to have available pile sections of different lengths.

[0017] Optionally one, optionally more than one, and optionally each, of the pre-formed pile sections may comprise a wall portion that forms the pile wall.

[0018] Optionally one, optionally more than one, and optionally each, of the pre-formed pile sections may be substantially annular.

[0019] Optionally one, optionally more than one, and optionally each, of the pre-formed pile sections may have varying lengths to suit. For example, optionally one, optionally more than one and optionally each of the pre-formed pile sections may have a length of from 0.1 to 12m. One or more, optionally more than one, and optionally each, of the pre formed pile sections may have a maximum lateral dimension of from 0.1 to 3 m. .

[0020] One or more, optionally more than one, and optionally each, of the pre-formed pile sections may comprise one or more (for example, two) lugs for handling the pile section. Such lifting lugs may be used to lower and raise the pile section. Such lifting lugs may be provided with an aperture. The aperture may be used to receive a lifting hook, cable or the like to assist in lowering and/or raising the pile section. Such lifting lugs may be provided at, or proximate, the top of the pile section. One or more, optionally more than one, and optionally each, of the pre-formed pile sections may comprise one or more (for example, two) recesses for receiving a lug provided on an adjacent pile section. The provision of such recesses permits lifting lugs to be used and for the pile sections to be stacked without the lifting lugs interfering with pile section stacking. Such recesses may be provided in the bottom of the pile section.

[0021] One or more, optionally more than one, and optionally each, of the pile sections may be provided with a sealing member (such as an annular sealing member) for forming a seal with an adjacent pile section. The provision of such seal members may be used to inhibit loss of fluid from within the pile assembly.

[0022] One or more, optionally more than one, and optionally each, of the pre-formed pile sections comprises one or more tensioning member channels for receiving a tensioning member. One or more tensioning member channels may be formed in a wall portion of the pre-formed pile section. Such tensioning member channels may be formed in the surface of the wall portion of the pre-formed pile section, for example, in an external surface of the wall portion of the pre-formed pile section, and for example, forming a surface groove for receiving a tensioning member. The presence of tensioning members the surface grooves of a pile section facilitates the use of the tensioning members to position pile sections that are to be lowered into place. Furthermore, the location of the tensioning members in the surface grooves allows the tensioning members to be maintained under tension while a pile section is being positioned prior to being lowered and while the pile section is being lowered. Furthermore, locating the tensioning members in the surface grooves may result in the tensioning members having to be manually handled less than if the tensioning members were located in a bore formed through the wall portion. This may be beneficial to worker safety. Such tensioning member channels may also be formed through the wall portion of the pre-formed pile section, for example, in a bore formed through the wall portion.

[0023] Such tensioning member channels in adjacent pile sections may be aligned with respect to one another so that the tensioning member is not twisted and to reduce non- axial forces on the tensioning member. For example, such tensioning member channels may be in the same radial position in each pile section in the pile.

[0024] The pile assembly optionally comprises a base below the pile wall. The base may be pre-formed e.g. pre-cast, and may comprise cementitious material, such as concrete. The base may have been formed in situ (e.g. by casting in situ). The base may be provided with one or more (for example, two) lugs for handling the pile section. Such lifting lugs may be used to lower and raise the base. Such lifting lugs may be provided with an aperture. The aperture may be used to receive a lifting hook, cable or the like to assist in lowering and/or raising the pile section. Such lifting lugs may be provided at, or proximate, the top of the base. The base may comprise one or more transport channels configured to allow the transport of a curable liquid material. Such channels may be configured to receive a curable liquid material from channels provided in an adjacent pile section. The base may comprise one or more outlet channels configured to convey a curable liquid material from a transport channel to an outlet. A curable liquid material may then be delivered to a space between the bore and the base of the pile assembly. [0025] The plurality of tensioning members may draw the base and pile sections together. To facilitate this, the base may be provided with one or more base tensioning member channels for receiving a tensioning member. The base tensioning member channels may be formed in a surface of the base, for example, in an outer surface of the base so that the tensioning members may extend around the base. Alternatively or additionally, base tensioning member channels may extend through the base. For example, base tensioning member channels may comprise bores formed through the base. The base tensioning member channels may be aligned with corresponding tensioning member channels provided in one or more of the pile sections. This may reduce twisting of the tensioning member. The base may be substantially cylindrical. [0026] The pile assembly optionally comprises a cover above the pile wall. The cover may be pre-form ed e.g. pre-cast may comprise cementitious or other materials, such as concrete, steel, or composites. The plurality of tensioning members may draw the cover and pile sections together. To facilitate this, the cover may be provided with one or more base tensioning member channels for receiving a tensioning member. The cover tensioning member channels may be formed in a surface of the cover , for example, in an outer surface of the base so that the tensioning members may extend around the cover. Alternatively or additionally, tensioning member channels may extend through the cover . For example, base tensioning member channels may comprise bores formed through the cover . The cover may be substantially cylindrical. The cover may be temporary or may be permanent. The cover may be chosen from a set of covers, the height of each cover (measured along a direction parallel to the longitudinal axis of the pile assembly) being mutually different. The pile assembly may comprise a spacer, optionally located above the cover, between the cover and the pile wall or between pre-formed pile sections. The spacer may be used so that the top of the pile assembly is at a desired height. The spacer may optionally be chosen from a set of spacers, the thickness of the spacers being mutually different from one another.

[0027] The cover may be provided on an upper surface with a configuration for mating with a corresponding configuration provided on a tensioning jack. The upper surface of the cover may be provided with a female configuration (such as a recess) for mating with a corresponding male configuration provided on a tensioning jack. The cover may be provided with multiple such configurations. Such configurations facilitate location of a tensioning jack for pulling the pre-formed pile sections together.

[0001] The cover, when in place, may be substantially below ground level, for example, up to 10.0m below ground level, optionally up to 8.0m below ground level, optionally up to 6.0m below ground level and optionally up to 4.0m below ground level. The cover, when in place, may be at least from 0.5m below ground level, optionally at least 1.0m below ground level, optionally at least 2.0m below ground level and optionally at least 3.0m below ground level. [0002] The cover may be selected from a set of covers. The height of each cover in the set of covers may be mutually different. The provision of covers of different heights allows the length of the pile assembly to be finely-tuned so that it is not necessary to remove or break-down excess material used to form the pile assembly. The pile assembly may comprise a spacer, optionally on the cover, or optionally between the pre-formed pile sections and the cover, or optionally between pre-formed pile sections. The spacer may be selected from a set of spacers. The thickness of each spacer in the set of spacers may be different. The provision of spacers of different thicknesses allows the length of the pile assembly to be finely-tuned so that it is not necessary to remove or break-down excess material used to form the pile assembly.

[0028] At least one, optionally more than one and optionally each of the tensioning members may extend the length of the pile. This allows the tensioning members to draw the pile sections together in an even manner and/or for the tensioning members to be tensioned as desired.

[0029] At least one, optionally more than one and optionally each of the tensioning members may extend through or along each pile section. As mentioned above, each pile section may comprise one or more tensioning member channels for receiving a tensioning member. At least one, optionally more than one and optionally each tensioning member may be received by a respective tensioning member channel.

[0030] At least one, optionally more than one and optionally each of the tensioning members may be secured, optionally at or near each end of the tensioning member. This allows tension to be applied to the tensioning members. At least one, optionally more than one and optionally each of the tensioning members may be secured at or near the bottom of the pile and optionally at or near the top of the pile. If the pile assembly comprises a base, the plurality of tensioning members may draw the base and pile sections together. To facilitate this, the base may be provided with one or more base tensioning member channels for receiving a tensioning member.

[0031] The pile assembly may comprise a suitable number of tensioning members. The pile assembly may comprise from two to twenty tensioning members, optionally from two to ten tensioning members and optionally from two to six tensioning members. The plurality of the tensioning members may be the same. Alternatively, at least one of the tensioning members may be different from the remainder of the tensioning members. [0032] At least one, optionally more than one and optionally each of the tensioning members may comprise a cable or a rod.

[0033] The pile assembly may comprise a cured material between at least part of an outside of the pile and the surface of the bore. The cured material may be grout. The cured material may be cementitious. The cured material may be resin. The cured material may optionally comprise reinforcing material. The cured material is optionally in contact with one or more of the plurality of the tensioning members.

[0034] The pile assembly of the first aspect of the present invention may be used in a variety of different situations. For example, the pile assembly may be used as a bearing pile for large diameter piles in dry or wet bored conditions, with or without the use of support fluid. The pile assembly may be used as a retaining wall pile, for secant walls or contiguous piled walls, for example. The pile assembly may be used as a tension pile, a laterally-loaded pile or a temporary works pile.

[0035] In accordance with a second aspect of the present invention, there is provided a foundations system comprising at least one pile assembly in accordance with the first aspect of the present invention. The foundations system may comprise a plurality of pile assemblies, at least one of which is a pile assembly in accordance with the first aspect of the present invention. More than one, and optionally each, of the plurality of pile assemblies may have those features described above in relation to the pile assembly of the first aspect of the present invention.

[0036] The foundations system may comprise a pile cap above the pile assembly. . The pile cap may also be positioned above the plurality of pile assemblies, if a plurality of pile assemblies is present. Such a pile cap is typically provided to provide a stable in situ cast foundation for any overlying structure and to provide a larger area for the distribution of loads into the underlying pile assemblies. [0037] The pile cap, if present, is optionally attached to the pile assembly. In this connection, the plurality of tensioning members of the pile assembly may draw the pile cap and the pile sections together. To facilitate this, the pile cap may be provided with one or more pile cap tensioning member channels for receiving a tensioning member. Pile cap tensioning member channels may extend through the pile cap. For example, pile cap tensioning member channels may comprise bores formed through the pile cap. The pile cap may be substantially cylindrical. If the foundations system comprises a pile cap, the plurality of tensioning members may draw the pile cap and the pile sections together. To facilitate this, the pile cap may be provided with one or more pile cap tensioning member channels for receiving a tensioning member.

[0038] If the foundations system comprises a plurality of pile assemblies, then the pile cap is optionally attached to each of the plurality of pile assemblies. Each of the plurality of pile assemblies may comprise a plurality of tensioning members for drawing the pile cap and pile sections together. If a pile assembly comprises a base and pile cap, the tensioning members may draw the base, the pile cap and the pile sections together.

[0039] The pile cap is optionally pre-formed (e.g. pre-cast) or may be formed in situ. [0040] In accordance with a third aspect of the present invention, there is provided a method of forming a pile assembly in accordance with the first aspect of the present invention, the method comprising: stacking a plurality of pre-formed pile sections end-to-end within the bore to form a hollow pile, the pre-formed pile sections forming a pile wall surrounding a cavity, to define a hollow interior of the pile; applying a tensioning force to at least one of the plurality of tensioning members, thereby drawing the pre-formed pile sections together.

[0041] A tensioning force may be applied to more than one and optionally each of the plurality of tensioning members. The same force need not be applied to each tensioning member. For example, it may be desirable to apply different tensioning forces to different tensioning members, for example, in order to change the position and/or orientation of a part of the pile assembly.. [0042] The method may comprise forming the bore. Forming the bore may comprise using a bore or drill. Those skilled in the art will realise that it is not necessary to use a rotating member, such as a drill, to form the bore.

[0043] The method may comprise providing a base. The base may be a pre-formed base or the base may be formed in situ. The base may be provided at or near the bottom of the bore. The base may be provided by lowering a pre-formed base.

[0044] The plurality of the tensioning members may be secured relative to the base such that a force may be applied to the tensioning members and to the base. Such a force increases the tension in the tensioning members and applies a force to the base that urges the base in an upwards direction.

[0045] The method may comprise lowering a pre-formed base into the bore, optionally with the plurality of the tensioning members being secured relative to the base such that a force may be applied to the tensioning members and to the base. The tensioning members are accessible at the ground surface, even when the base is in position at or near the bottom of the bore.

[0046] The base may comprise one or more base tensioning member channels for receiving a tensioning member, each tensioning member being received by a respective base tensioning member channel. The use of the base tensioning member channels facilitates the correct positioning of the tensioning members, subsequent pre-cast sections and any cover.

[0047] The base may be sealed to the adjacent pile section to inhibit fluid passage therepast.

[0048] The base tensioning member channels may be formed in a surface of the base, for example, in an outer surface of the base so that the tensioning members may extend around the base. Alternatively or additionally, base tensioning member channels may extend through the base. For example, base tensioning member channels may comprise bores formed through the base. The base may be substantially cylindrical.

[0049] In the absence of a base, the method may comprise lowering a lowermost pre-cast pile section into the bore, optionally with the plurality of the tensioning members being secured relative to the lowermost pile section such that a force may be applied to the tensioning members and to the lowermost pile section. Such a force increases tension in the tensioning members and urges the lowermost pile section in an upwards direction. The method may comprise lowering the lowermost pile section into the bore, optionally with the plurality of the tensioning members being secured relative to the base such that a force may be applied to the tensioning members and to the lowermost pile section. The tensioning members are accessible at the ground surface, even when the lowermost pile section is in position at or near the bottom of the bore. The lowermost pile section may comprise one or more base tensioning member channels for receiving a tensioning member, each tensioning member being received by a respective tensioning member channel.

[0050] The use of the tensioning member channels facilitates the correct positioning of the tensioning members.

[0051] The method may comprise securing at least one, optionally more than one and optionally each of the plurality of tensioning members, optionally prior to stacking the plurality of pre-formed pile sections end-to-end within the bore to form a hollow pile and optionally after providing a base at or near the bottom of the bore (or if a base is not provided, after providing a lowermost pile section at or near the bottom of the bore). Such securing is a temporary securing and not a permanent securing. Securing the tensioning member optionally comprises applying tension to the tensioning member. Such a pre stress/tensioning step may facilitate alignment of pre-formed pile sections prior to lowering into the pile. Such a step may also be used to modify the orientation of the base (if present) or lowermost pile section (if no base is used), for example, to ensure that the base or lowermost pile section is level. This step does not correspond to that of applying a tensioning force to the plurality of tensioning members, thereby drawing the pre-formed pile sections together. This step typically takes place after a base (if present) or lowermost pile section has been located in the bore.

[0052] The method may comprise aligning a pile section relative to one or more of the (optionally secured) tensioning members. The method may comprise turning a pile section relative to one or more of the (optionally secured) tensioning members. The method may comprise aligning a pile section relative to one or more of the tensioning members to locate one or more of the tensioning members in respective tensioning member channel(s) provided in the pile section. The method may comprise aligning more than one of the pile sections in this way.

[0053] The method may comprise lowering a pile section in the bore. The method may comprise aligning a pile section relative to one or more of the (optionally secured) tensioning members prior to lowering the pile section in the bore. Alternatively or additionally, the method may comprise lowering the pile section in the bore and then aligning a pile section relative to one or more of the (optionally secured) tensioning members.

[0054] The method may comprise lowering more than one, and optionally each, pile section into the bore.

[0055] The method may comprise providing a curable material between at least part of an outside of the pile and the surface of the bore. The curable material may be grout. The curable material may be a curable resin precursor. The curable material may optionally be provided with reinforcing material. The curable material is optionally in contact with one or more of the plurality of the tensioning members. The curable material may be provided before or after the application of the tensioning force to the plurality of tensioning members.

[0056] The method may comprise providing a cover on the stack of the plurality of pile sections. The cover may inhibit ingress of foreign matter etc. into the cavity formed by the plurality of pile sections. The cover may be cylindrical. The cover may be temporary or permanent. The method may comprise selecting a cover from a set of covers. The height of each cover in the set of covers may be mutually different. The provision of covers of different heights allows the length of the pile assembly to be finely-tuned so that it is not necessary to remove or break-down excess material used to form the pile assembly. The method may comprise providing a spacer, optionally on the cover, or optionally between the pre-formed pile sections and the cover, or optionally between pre- formed pile sections. The method may comprise selecting a spacer from a set of spacers. The thickness of each spacer in the set of spacers may be different. The provision of spacers of different thicknesses allows the length of the pile assembly to be finely-tuned so that it is not necessary to remove or break-down excess material used to form the pile assembly.

[0057] The cover, when in place, may be substantially below ground level, for example, up to 10.0m below ground level, optionally up to 8.0m below ground level, optionally up to 6.0m below ground level and optionally up to 4.0m below ground level. The cover, when in place, may be at least from 0.5m below ground level, optionally at least 1.0m below ground level, optionally at least 2.0m below ground level and optionally at least 3.0m below ground level.

[0058] The depth of the cover below ground level may optionally depend on the diameter of the pile. For example, if a pile is narrow, then the depth of the cover below ground level may be lower than if the pile is wide.

[0059] As mentioned above, the method comprises applying a tensioning force to at least one of the plurality of tensioning members, thereby drawing the pre-formed pile sections together. The method may also comprise applying a compressive force to the pile assembly, optionally at the same time as the tensioning force is applied.

[0060] In accordance with a fourth aspect of the present invention, there is provided a method of making a foundations system in accordance with the second aspect of the present invention. In this connection, the method may comprise forming a plurality of pile assemblies. At least one, optionally more than one and optionally each of the pile assemblies may be formed using the method of the third aspect of the present invention. [0061] The method may comprise providing a cap. The method may comprise securing the pile assembly to the cap. Securing the cap to the pile assembly may comprise use of plunge bars or similar.

[0062] The method may comprise securing the plurality of pile assemblies to the cap. [0063] In accordance with a fifth aspect of the present invention, there is provided a method of forming a pile assembly in a bore, the method comprising: providing two or more tensioning members in the bore; using the two or more tensioning members to orient a first pre-formed pile section; and lowering the first pre-formed pile section within the bore.

[0064] The applicant has discovered that it is possible to use tensioning members to ensure that pre-formed pile sections are oriented correctly before being lowered into a bore and during the installation process i.e. as the first pre-formed pile section is lowered within the bore.

[0065] The method may comprise providing in the bore a base to which the tensioning members are attached. The base may be provided at or near the bottom of the bore.

[0066] The tensioning members may be secured, for example, at or above the top of the bore. Securing the tensioning members may facilitate easier orienting of the first pre formed pile section.

[0067] At least one, optionally more than one, and optionally each, of the pre-formed pile sections may comprise one or more features of the pile sections described above in relation to the pile assembly of the first aspect of the present invention. For example, the first pre-formed pile section may be substantially tubular. For example, the first pre formed pile section may comprise one or more tensioning member channels to receive a respective tensioning member. The one or more tensioning member channels may be formed in a surface of the first pre-formed pile section. Using the two or more tensioning members to orient a first pre-formed pile section may comprise orienting the first pre formed file section so that at least one, optionally more than one, and optionally each tensioning member is received in a respective tensioning member channel.

[0068] The method may comprise lowering the first pre-formed pile section along at least part of the length of the two or more tensioning members.

[0069] The tensioning member may comprise cables for example. The tensioning members are typically in tension when the tensioning members are used to orient the first pre-formed pile section. [0070] The method may comprise using the two or more tensioning members to orient a second pre-formed pile section. The second pre-formed pile section may be lowered down the bore.

[0071] The tensioning members may be used to orient further pre-formed pile sections. Multiple pre-formed pile sections may be used to make a pile. The pile is optionally hollow.

[0072] The tensioning members may be used to draw the various parts of a pile assembly together by applying a tension to one or more of the tensioning members, substantially as described in relation to the first, second, third and fourth aspects of the present invention. [0073] The method may comprise providing a cover. The cover may be provided on top of a pile comprising a plurality of pre-formed pile sections.

[0074] The method of the present aspect of the invention may be used to make a pile assembly in accordance with the first aspect of the present invention.

[0075] It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the third aspect of the invention may incorporate any of the features described with reference to the pile assembly of the first aspect of the invention and vice versa.

DESCRIPTION OF THE DRAWINGS

[0076] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:

[0077] Figure 1 shows a schematic cross-sectional view of an example of an embodiment of a foundations system in accordance with the second aspect of the present invention; [0078] Figure 2 shows schematic cross-sectional views of a pile assembly under construction;

[0079] Figure 3 shows a schematic cross-sectional view of an example of an embodiment of a pile assembly in accordance with the first aspect of the present invention; [0080] Figure 4 shows a schematic cross-section view of a pile assembly under construction;

[0081] Figure 5A shows a schematic cross-section view of part of an embodiment of a pile assembly showing an arrangement of a spacer and a cover;

[0082] Figure 5B shows a schematic cross-section view of part of another embodiment of a pile assembly showing an alternative arrangement of a spacer and a cover; and [0083] Figure 6 is a schematic representation of an embodiment of a method of making a pile assembly in accordance with the present invention.

DETAILED DESCRIPTION

[0084] Figure 1 shows a schematic cross-sectional view of a an example of an embodiment of a foundations system in accordance with the present invention The foundations system is denoted generally by reference numeral 1. The foundations system 1 comprises multiple pile assemblies (in this case, eight, two of which are shown 2, 3) attached to a pile cap 4. The foundations system 1 comprises a first pile assembly 2 located within a first bore 5. The first pile assembly 2 comprises a first hollow pile 200 comprising a plurality of pre-formed pile sections 2A, 2B, 2C, 2D that form a pile wall surrounding a cavity, to define a hollow interior of the pile. The foundations system 1 also comprises a plurality of tensioning members in the form of cables for drawing the pre-formed pile sections together. Two tensioning members 9, 10 are used to draw pile sections 2A, 2B, 2C, 2D together, though those skilled in the art will realise that a different number of tensioning members may be used. Anchor wedges (not shown in Fig. 1) retain the tensioning members in tension and inhibit release of tension. A second pile assembly 3 is shown located within a second bore 6, and comprises a second hollow pile 300 comprising a plurality of pre-formed pile sections 3A, 3B, 3C, 3D that form a pile wall surrounding a cavity, to define a hollow interior of the pile. Two tensioning members in the form of cables are provided for drawing the pre-formed pile sections 3A, 3B, 3C, 3D together. Anchor wedges (not shown in Fig. 1) retain the tensioning members in tension and inhibit release of tension. Those skilled in the art will realise that a different number of tensioning members may be used.

[0085] The first pile assembly 2 and second pile assembly 3 each comprise a base 7, 8. Bases 7, 8 are pre-cast concrete disks. Each tensioning member 9, 10, 11, 12 is secured to the respective base 7, 8 so that when a tensioning force is applied to the respective tensioning member then an upwards force is applied to the base, such an upwards force urging the base and pile sections towards one another. The tensioning members provide bending and tension resistance to the pile assembly, and mean that adjacent pile sections do not have to be physically connected to one another.

[0086] The tensioning members 9, 10, 11, 12 are located in base tensioning member channels (not shown) formed in the external circumferential surface of the base. The tensioning members extend along the length of the respective first 200 and second 300 pile, located in tensioning member channels formed in the external circumferential surface of the pile sections 2A, 2B, 2C, 2D, 3A, 3B, 3C, 3D. The tensioning members extend through bores (not shown) formed in at the top of the cover 13, 14, and are secured in tension by anchor wedges (not shown).

[0087] Each pile section 2A, 2B, 2C, 2D, 3 A, 3B, 3C, 3D is a pre-cast concrete tube, having a hollow interior. Pile sections 2A, 2B, 2C, 2D form first pile 200 and pile sections 3A, 3B, 3C, 3D form second pile 300. As mentioned above, the external surface of pile sections 2A, 2B, 2C, 2D, 3A, 3B, 3C, 3D are provided with tensioning member channels for receiving tensioning members. This facilitates well-defined placement of the tensioning members, but also facilitates alignment of the pile sections relative to one another, as will be explained below.

[0088] Pre-cast pile sections are advantageous in that they dispense with the need to transport liquid concrete and to form a pile fully from liquid concrete on site. Furthermore, pre-cast pile sections may be readily inspected for defects. Piles made from pre-cast pile sections are also typically easier to dismantle or break-down than traditional cast in situ piles. Furthermore, given that it is possible to make pre-cast piles sections using fibre-reinforced concrete, there may be no need for reinforcement cages that would usually be used with cast in situ piles. Examples of such pre-case pile sections are described in GB2580041.

[0089] As mentioned above, the first 200 and second 300 piles are hollow piles. Hollow piles use less material than non-hollow piles, and the pile sections are relatively light and easy to handle, depending on size, of course. Furthermore, hollow piles may be less stiff than non-hollow piles, and the stiffness of hollow piles tends to better match the stiffness of the surrounding ground, providing better load transfer from pile to ground, thereby improving overall load bearing capacity and settlement performance as against traditional non-hollow cast in situ piles.

[0090] A cementitious grout 19, 20 is provided between the external surfaces of pile sections 2A, 2B, 2B, 2D, 3 A, 3B, 3C, 3D and the internal surface of the respective first bore 5 or second bore 6. The grout 19, 20 is also in contact with the tensioning members 9, 10, 11, 12. The grout 19, 20 provides increased friction between the pile and the bore. [0091] Those skilled in the art will realise that repeat grouting operations may be adopted in order to increase end bearing resistance through the use of grout-carrying channels (for example, tubes-a-manchette) incorporated in the base.

[0092] Those skilled in the art will realise that repeat grouting operations may be adopted in order to increase shaft friction resistance through the use of channels (such as those provided by tubes-a-manchette) incorporated in the hollow pre-cast pile sections.

[0093] Those skilled in the art will realise that other sorts of grout (such as a resin) may be used.

[0094] A method of making the foundations system 1 of Figure 1 will now be described with reference to Figures 2 and 6. The method will be described with reference to the formation of the first pile assembly 2. Referring to Figure 6, the method of forming a pile assembly is denoted generally by reference numeral 200. The method 200 comprises stacking 201 a plurality of pre-formed pile sections end-to-end within the bore to form a hollow pile, the pre-formed pile sections forming a pile wall surrounding a cavity, to define a hollow interior of the pile; and applying 202 a tensioning force to at least one of the plurality of tensioning members, thereby drawing the pre-formed pile sections together. The method is now described in more detail with reference to Figure 2. Referring to A, the first bore 5 is formed in the ground G using methods well-known to those skilled in the art. A support tube 21 is inserted into the mouth of the bore 5 to maintain the integrity of the bore at the bore’s mouth. Two tensioning members in the form of cables are located in respective base tensioning member channels in base 7 and the tensioning members are secured so that any subsequent pulling of the tensioning cables will urge the base upwards once the base is in place. Referring to B, base 7 is lowered into the bore using two lifting lugs (not shown) provided on top of base 7. Base 7 is pre-cast and has a generally disk-like shape. Referring to C, tensioning members 9, 10 are “locked-in ” at lock-in positions 22, securing the position of the tensioning members and providing some tension therein. The “locked-in” tensioning members provide a guide for the placement of pile sections 2A, 2B, 2C, 2D. Pile section 2A is oriented so that the “locked-in” tensioning members are located within tensioning member channels formed in the external surface of pile section 2A. Once the two tensioning members are each located in a respective tensioning member channel, the pile section 2A is lowered down the first bore 5 onto first base 7. The lifting lugs of base 7 are received by two recesses (not shown) provided in the bottom of pile section 2A. Pile sections 2B, 2C, 2D are then lowered into place (see D). A cover 13 is then placed on top of pile section 2D to inhibit entry of unwanted material into the void formed by the hollow pile (see E). Anchor wedges 23 are then installed (see F). Referring to G, grouting 19 is then introduced into a gap between the external surface of the pile and the internal surface of first bore 5. In this connection, each pile section 2A, 2B, 2C, 2D is provided with a plurality of transport channels that extend parallel to the length of the pile section, within the wall of each pile section (see, for example, Fig. 2 and associated text of GB2580041). The transport channels of adjacent pile sections are aligned so that grout may be delivered along the length of the pile. Each transport channel is in communication with radially-extending outlet channels that convey grout from the transport channel to an outlet in the exterior surface of the pile section, thereby delivering grout to the gap between the pile section and the bore. The temporary cover 13 may then be fitted over the first pile assembly, with the tensioning members 9, 10 extending through channels provided in the cover 13. Referring to H, tension 24 is applied to tensioning members 9, 10 to draw the first base 5 and pile sections 2A, 2B, 2C, 2D towards the cover 13. Anchor wedges 23 permit passage of the tensioning member in one direction only. In this case, anchor wedges 23 permit passage of the tensioning member upwards i.e. in a direction that increases tension, but do not permit passage of the tensioning member downwards past the anchor wedges. The anchor wedges therefore maintain any tension in the tensioning member. The tensioning members may be “locked-in” using a clamp (not shown). Cap 4 may then be fitted over the first pile assembly 2. Connection between the cap 4 and first pile assembly 2 may be achieved by methods known to those skilled in the art. For example, the first pile assembly 2 may be provided with plunge bars that may be tied-in to an overlying structure, such as cap 4.

[0095] The example above describes how a foundations system comprising a cover may be constructed. An example of an embodiment of a pile assembly without such a cover will now be described with reference to Figure 3. The pile assembly is denoted generally by reference numeral 1002. The pile assembly 1002 comprises a hollow pile 1200 comprising a plurality of pre-formed pile sections 1002A, 1002B, 1002C, 1002D that form a pile wall surrounding a cavity, to define a hollow interior of the pile. Two tensioning members 1009, 1010 are used to draw pile sections 1002A, 1002B, 1002C, 1002D together, though those skilled in the art will realise that a different number of tensioning members may be used.

[0096] The pile assembly 1002 comprises a base 1007. Base 1007 is a pre-cast concrete disks. The pile assembly 1002 also comprises a cover 1013. Each tensioning member 1009, 1010 is secured to base 1007 so that when a tensioning force is applied to the respective tensioning member then an upwards force is applied to the base, such an upwards force urging the base, pile sections and cover towards one another. The tensioning members provide bending & tension resistance to the pile assembly, and mean that adjacent pile sections do not have to be physically connected to one another. [0097] The tensioning members 1009, 1010 are located in base tensioning member channels (not shown) formed in the external circumferential surface of the base. The tensioning members extend along the length of the pile 1200, located in tensioning member channels formed in the external circumferential surface of the pile sections 1002A, 1002B, 1002C, 1002D.

[0098] Each pile section 1002A, 1002B, 1002C, 1002D is a pre-cast concrete tube, having a hollow interior. Pile sections 1002A, 1002B, 1002C, 1002D form pile 200. As mentioned above, the external surface of pile sections 1002A, 1002B, 1002C, 1002D are provided with tensioning member channels for receiving tensioning members. This facilitates well-defined placement of the tensioning members, but also facilitates alignment of the pile sections relative to one another, as will be explained below.

[0099] The tensioning members 1009, 1010 are held in tension by anchor wedges 1023 A, 1023B. Anchor wedges resist release of the tension in the tensioning members, - [00100] Pile 200 is a hollow pile. Hollow piles use less material than non-hollow piles, and the pile sections are relatively light and easy to handle, depending on size, of course. Furthermore, hollow piles may be less stiff than non-hollow piles, and the stiffness of hollow piles tends to better match the stiffness of the surrounding ground, providing better load transfer from pile to ground, thereby improving overall load bearing coveracity and settlement performance as against traditional non-hollow cast in situ piles. [00101] A cementitious grout 1019, 1020 is provided between the external surfaces of pile sections 1002A, 1002B, 1002C, 1002D and the internal surface of bore 1005. The grout 1019, 1020 is also in contact with the tensioning members 1009, 1010. The grout 1019, 1020 provides increased friction between the pile and the bore.

[00102] A method of making the pile assembly 1002 of Figure 3 will now be described with reference to Figures 3 and 4. Referring to A, bore 1005 is formed in the ground G using methods well-known to those skilled in the art. A support tube 1021 is inserted into the mouth of the bore 1005 to maintain the integrity of the bore at the bore’s mouth. Two tensioning members in the form of cables are located in respective base tensioning member channels in base 1007 and the tensioning members are secured so that any subsequent pulling of the tensioning cables will urge the base upwards once the base is in place. Referring to B, base 1007 is lowered into the bore using two lifting lugs (not shown) provided on top of base 1007. Base 1007 is pre-cast and has a generally disk-like shape. Referring to C, tensioning members 1009, 1010 are “locked-in” at lock-in positions 1022, securing the position of the tensioning members and providing some tension therein. The “locked-in” tensioning members provide a guide for the placement of pile sections 1002A, 1002B, 1002C, 1002D. Pile section 1002A is oriented so that the “locked-in” tensioning members are located within tensioning member channels formed in the external surface of pile section 1002A. Once the two tensioning members are each located in a respective tensioning member channel, the pile section 1002A is lowered down bore 1005 onto base 1007. The lifting lugs of base 1007 are received by two recesses (not shown) provided in the bottom of pile section 1002A. Pile sections 1002B, 1002C, 1002D are then lowered into place (see D). A cover 1013 is then placed on top of pile section 1002D to inhibit entry of unwanted material into the void formed by the hollow pile (see E). Anchor wedges 1023 A, 1023B are then installed (see F). Referring to G, grouting 1019 is then introduced into a gap between the external surface of the pile and the internal surface of first bore 5. In this connection, each pile section 1002A, 1002B, 1002C, 1002D is provided with a plurality of transport channels that extend parallel to the length of the pile section, within the wall of each pile section (see, for example, Fig. 2 and associated text of GB2580041). The transport channels of adjacent pile sections are aligned so that grout may be delivered along the length of the pile. Each transport channel is in communication with radially-extending outlet channels that convey grout from the transport channel to an outlet in the exterior surface of the pile section, thereby delivering grout to the gap between the pile section and the bore. Referring to H, tension 1024 is applied to tensioning members 1009, 1010 to draw the base 1007 and pile sections 1002A, 1002B, 1002C, 1002D together. Anchor wedges 1023 A, 1023B permit passage of the tensioning member in one direction only. In this case, anchor wedges 1023 A, 1023B permit passage of the tensioning member upwards i.e. in a direction that increases tension, but do not permit passage of the tensioning member downwards past the anchor wedges. The anchor wedges 1023 A, 1023B therefore maintain any tension — in the tensioning member.

[00103] Plunge bars (not shown) may be inserted into the top portion of the pile assembly provide additional bending and tension resistance as well as providing continuity reinforcement into the above structure e.g. slab / pile cap.

[00104] Figures 5A and 5B show pile assemblies comprising a spacer 501. The spacer 501 comprises a disk or annulus of pre-cast concrete. In Figure 5A, the spacer 501 is located between pile section 2D and cover 13. In Figure 5B, the spacer 501 is located on top of cover 13, which is itself located on top of pile section 2D. Spacer 501 adjusts the length of the pile assembly so that the top of the pile assembly is in the desired position, in this case, substantially level with the surrounding ground G. Spacer 501 is provided with channels (not shown) for the location of tensioning members. Such channels may be located in the external (circumferential) surface of the spacer 501. [00105] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

[00106] The examples above describe the use of cables as tensioning elements in the pile assembly. Those skilled in the art will realise that other tensioning elements, such as rods or cables, could be used.

[00107] The examples above describe the use of a pre-formed base. Those skilled in the art will realise that the piling assembly need not comprise a base. Furthermore, the base, if used, may be a base that is formed in situ.

[00108] The examples above describe the use of a pre-formed pile cap . Those skilled in the art will realise that the foundations system need not comprise a pile cap , but the provision of a pile cap may be preferred. If a pile cap is provided, then a pile cap may be formed in situ. [00109] The pile sections used in the examples above are exclusively pre-cast. It is possible for at least one pile section to be made in situ.

[00110] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.