AU2010226975A1 - Precast Concrete Foundation Block and Foundation - Google Patents

Description

Regulation 3.2 AUSTRALIA PATENTS ACT, 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT ORIGINAL Name of Applicant: GRIFFITHS CIVIL BUILD LIMITED Actual Inventors: GRIFFITHS, Melvyn Thomas Address for service in A J PARK, Level 11, 60 Marcus Clarke Street, Canberra ACT Australia: 2601, Australia Invention Title: Precast Concrete Foundation Block and Foundation The following statement is a full description of this invention, including the best method of performing it known to us.

-2 TITLE: PRECAST CONCRETE FOUNDATION BLOCK AND FOUNDATION DESCRIPTION 5 FIELD OF INVENTION The present invention relates to an in-ground foundation system for an above-ground structure. The invention relates to a precast foundation block, foundations using the foundation block, and methods of constructing foundations using the foundation block. In one application of the 10 invention, the foundation system carries a monopole or lattice tower, for example for supporting antennae for a cellular communications system. BACKGROUND 15 Towers for supporting cellular communications antennae are mounted to in-ground concrete foundations. The concrete components are pouted successively in stages in-situ. The construction period is prolonged by the required curing time of the successively poured components. Many tower sites are required in densely populated and built-up areas where a prolonged construction period is undesirable. 20 The strength of concrete components that are poured in situ can be affected by ground and site conditions, for example soil moisture content, soil and air temperatures, and the curing time. Components poured in situ must be oversized to ensure a minimum sufficient finished strength is achieved under unpredictable and uncertain curing conditions. 25 The size of tower foundations limits the installation of towers to sites of sufficient area. Many smaller sites could be used if towers could be mounted on smaller sized foundations. SUMMARY OF INVENTION 30 An object of at least one embodiment of the invention is to provide an in-ground foundation system, or at least to provide the public with a useful choice. An object of at least one other embodiment of the invention is to provide a method of constructing an in-ground foundation system. 2828992-1 -3 In a first aspect the invention may be broadly said to be a foundation interface assembly, for supporting a superstructure attached to the foundation interface assembly when the foundation interface assembly is placed on and attached to a substructure, the foundation 5 interface assembly comprising a precast concrete block, a reinforcing structure, and a top plate; wherein: the block is reinforced by the block reinforcing structure; the block reinforcing structure is partially embedded in the block during casting of the block; 10 portions of the block reinforcing structure extend above a top surface of the block for attachment to a base end of the superstructure to be supported by the foundation interface assembly; the block has a plurality of through-holes, each through-hole extending upwardly from a downward facing surface of the block, through the block, to an upward-facing surface of the 15 block; the top plate is at the top surface of the block; the top plate has a plurality of through-holes; and the portions of the block reinforcing structure extend above the top surface of the block and extend respectively through the through-holes in the top plate for attachment to the base end 20 of the superstructure to be supported by the foundation interface assembly. Preferably, the portions of the block reinforcing structure that extend above the top surface of the block are arranged in a pattern which surrounds the through-holes in the block. 25 Preferably, the though-holes in the top plate are arranged on the circumference of a first circle; the though-holes in the block are arranged on the circumference of a second circle; the first and second circles are concentric; and the radius of the first circle is larger than the radius of the second circle. 30 Preferably, the top plate is a flat annular plate with an aperture through an inner zone of the plate; 2828992-1 -4 a duct, for accommodating passage of one or more electrical cables or the like, extends from a first duct opening at a side wall of the block, and through the block, to a second duct opening at the upward-facing surface of the block; and the second duct opening is aligned with the aperture in the annular plate. 5 Preferably, each of the portions of the block reinforcing structure that extend above the top surface of the block is a steel rod with a threaded upper end portion; threaded nuts are fitted onto the threaded upper end portions of the steel rods to lie 10 below the top plate; and the top plate rests on the threaded nuts which can be screwed up or down the steel rods to level the top plate. In a second aspect the invention may be broadly said to be a foundation comprising the 15 foundation interface assembly of the first aspect of the invention and its preferences, wherein: the foundation interface assembly is fitted to a substructure; the substructure comprises a pad assembly; the pad assembly comprises at least a first pad; the, or each, pad of the pad assembly is a concrete pad that is precast before assembly of 20 the pad assembly; the first pad is reinforced by a first pad reinforcing structure; a first portion of the first pad reinforcing structure is embedded in the first pad; second portions of the first pad reinforcing structure extend above an upper face of the first pad and extend respectively through the through-holes in the block; and 25 the block is fastened to the first pad reinforcing structure by respective first fasteners fitted to the second portions of the first pad reinforcing structure. Preferably, the first pad is a lower pad; 30 the pad assembly comprises at least one upper pad; the upper pad is reinforced by a second pad reinforcing structure which is embedded in the upper pad; the upper pad has through-holes each of which extend from a bottom surface of the upper pad and through the upper pad to an upper face of the upper pad; 2828992-1 -5 third portions of the first pad reinforcing structure extend above the upper face of the first pad and extend respectively though a first subset of the through-holes in the upper pad; and the upper pad is fastened to the first pad reinforcing structure by respective second fasteners fitted to the upper ends of the third portions of the first pad reinforcing structure. 5 Preferably, at least one of: an interface zone between the lower first pad and the upper pad; an interface zone between the upper pad and the block; or at least one of the through-holes in the block; 10 is filled with grout. In a third aspect the invention may be broadly said to be a foundation comprising the foundation interface assembly of the first aspect of the invention and its preferences, wherein: the foundation interface assembly is fitted to a substructure; 15 the substructure comprises a pile; the pile is reinforced by a pile reinforcing structure; a first portion of the pile reinforcing structure is embedded in the pile; second portions of the pile reinforcing structure extend above an upper end of the pile to extend respectively though the through-holes in the block; and 20 the block is fastened to the pile reinforcing structure by respective first fasteners fitted to the second portions of the pile reinforcing structure. Preferably, an interface zone between the pile and the block is filled with grout. 25 Preferably, the foundation further comprises a levelling plate, wherein: the levelling plate has a plurality of through-holes; each of the second portions of the pile reinforcing structure is a threaded reinforcing rod; threaded levelling nuts are respectively fitted onto the threaded reinforcing rods; the threaded reinforcing rods extend upward through the through-holes in the levelling 30 plate; the levelling plate rests on the threaded levelling nuts; and the threaded levelling nuts can be screwed up or down the reinforcing rods to level the levelling plate prior to placement of the block on the levelling plate and location of the reinforcing rods respectively in the through-holes in the block. 2828992-1 -6 Preferably, an interface zone between the pile and the levelling plate is filled with grout. Preferably, the through-holes in the block are filled with grout after the second portions of the 5 pile reinforcing structure are located in the through-holes in the block. In a fourth aspect the invention may be broadly said to be a method of constructing the foundation of the second aspect of the invention, comprising the steps of: 1. precasting the first pad; 10 2. placing the first pad on a ground surface at the site with the second portions of the first pad reinforcing structure extending upward; 3. placing the foundation interface assembly over the first pad with the second portions of the first pad reinforcing structure extending respectively upward through the through-holes in the block; and 15 4. fastening the foundation interface assembly to the first pad by respectively fitting the first fasteners to upper ends of the second portions of the first pad reinforcing structure. In a fifth aspect the invention may be broadly said to be a method of constructing the foundation 20 of the preferences of the second aspect of the invention, comprising the steps of: I. precasting the first pad and the upper pad; 2. placing the first pad on a ground surface at the site with the second portions of the first pad reinforcing structure extending upward; 3. placing the upper pad on the first pad, with the second portions of the first pad 25 reinforcing structure extending upward through a second sub-set of the through holes in the upper pad, and the third portions of the first pad reinforcing structure extending upward through the first sub-set of the through-holes in the upper pad; 4. fastening the upper pad to the first pad by respectively fitting the second fasteners to the upper ends of the third portions of the first pad reinforcing structure; 30 5. placing the foundation interface assembly over the upper pad, with the second portions of the first pad reinforcing structure extending upward and respectively through the through-holes in the block; 2828992-1 -7 6. fastening the foundation interface assembly to the pad assembly by respectively fitting the first fasteners to upper ends of the second portions of the first pad reinforcing structure. 5 Preferably, prior to placing the first pad in Step 2 of the methods of the fourth and fifth aspects of the invention, the ground surface is prepared by the steps of: A. excavating topsoil from the site; B. optionally compacting at least an upper layer of exposed subterranean material remaining at the site after excavation of the topsoil; 10 C. optionally placing and compacting hard fill at the site; and D. overlaying the upper layer of subterranean material compacted in Step B, or the hard fill placed and compacted in Step C, with a grout layer. In a sixth aspect the invention may be broadly said to be a method of constructing the 15 foundation of the third aspect of the invention and the first of its preferences, at a site, the method comprising the steps of: 1. forming an in-ground pile cavity at the site; 2. placing the pile reinforcing structure at least partially in the cavity; 3. pouring concrete into the cavity to embed the first portion of the pile reinforcing 20 structure; 4. allowing the poured concrete to at least partially cure to form the pile; 5. placing the foundation interface assembly over the pile with the second portions of the pile reinforcing structure extending upward through the through-holes in the block; and 25 6. fastening the foundation interface assembly to the pile by fitting the first fasteners to respective upper end portions of the second portions of the pile reinforcing structure. In a seventh aspect the invention may be broadly said to be a method of constructing the foundation of the second and third preferences of the third aspect of the invention, at a site, the 30 method comprising the steps of: 1. forming an in-ground pile cavity at the site; 2. placing the pile reinforcing structure at least partially in the cavity; 3. fitting the threaded levelling nuts respectively onto the threaded reinforcing rods; 2828992-1 -8 4. resting the levelling plate on the levelling nuts with the threaded reinforcing rods extending upward through the through-holes in the levelling plate; 5. screwing the levelling nuts up or down to level the levelling plate; 6. pouring concrete into the cavity to embed the first portion of the pile reinforcing 5 structure; 7. allowing the poured concrete to at least partially cute; 8. placing the foundation interface assembly on the levelling plate with the second portions of the pile reinforcing structure extending upward through the through holes in the block; and 10 9. fastening the foundation interface assembly to the pile by fitting the first fasteners to respective upper end portions of the second portions of the pile reinforcing structure. Preferably, hard fill is placed and compacted around the foundation interface assembly and the site reinstated to correspond to the level of undisturbed ground surrounding the site. 15 The term 'comprising' as used in this specification means 'consisting at least in part of, that is to say when interpreting statements in this specification which include that term, the features, prefaced by that term in each statement, all need to be present but other features can also be present. 20 The term 'precast', when used in this specification to refer to a concrete article, is to be understood as indicating that the concrete article is cast, and at least partially cured, substantially in its finished shape before installation of the article at the site at which the article is intended to be used. 25 BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments and methods of utilising the invention will be further described, with reference to the accompanying figures, by way of example only and without intending to be 30 limiting, wherein; Figure 1 shows a perspective view of a foundation interface assembly according to the invention, with detail of ducts shown in broken lines; 2828992-1 -9 Figure 2 shows a perspective view of the foundation interface assembly of Figure 1, with detail of a reinforcing structure shown in broken lines; Figure 3 shows a perspective view of a foundation being the interface assembly of Figure 1 fitted to a pad substructure; 5 Figure 4 shows an exploded view of the foundation of Figure 3; Figure 5 shows a cross-sectional view of the foundation of Figure 3; Figure 6 shows a perspective view of a foundation being the interface assembly of Figure 1 fitted to a pile substructure; Figure 7 shows an exploded view of the foundation of Figure 6; 10 Figure 8 shows a cross-sectional view of the foundation of Figure 6; Figure 9 is an exploded view showing a modification to the foundation of Figure 6; and Figure 10 is a cross-sectional view showing the modification of Figure 9. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 15 Referring to the figures it will be appreciated that the invention may be implemented in various forms and modes. The following description of preferred embodiments of the invention is given by way of example only. References to vertical, horizontal, bottom, top, upper, lower, and side, etc, are to be understood as referring to the particular orientation of the object being discussed as 20 shown in the accompanying figures. It is also to be understood that the invention is not limited to the orientations shown in the figures. Figures 1 and 2 show perspective views of a first embodiment of a foundation interface assembly 100 according to the present invention. This foundation interface assembly includes a precast 25 concrete block 101. Some block detail may be best seen in the cross-sectional view of Figure 5. The block has a rectangular parallelepiped shape, and is preferably cuboid. The block is reinforced by a reinforcing structure 102 embedded in the block. The reinforcing structure 102, shown by broken lines in Figure 2, follows well-known industry-accepted practices and comprises 30 a lattice of steel rods, welded together at some points where the rods overlie or intersect one 2828992-1 - 10 another, and shaped with right angled bends to extend generally in three mutually orthogonal directions that are each substantially parallel to a respective pair of opposite faces of the block. A flat annular steel anchor plate 104 is located on the top face 106 of the block. The anchor 5 plate is preferably provided by the manufacture of the pole or tower to be supported on the foundation interface assembly. The plate includes provision for the base end of the pole or tower to be fastened to the anchor plate after placement of the block on an in-ground foundation substructure. 10 The anchor plate 104 is fastened by a set of ten vertical fastening rods 107 to a flat annular hold down plate 105 (best seen in the cross-sectional view of Figure 5). The hold-down plate 105 is embedded near the bottom of the block and may be welded to adjacent parts of steel rods of the reinforcing structure 102. The anchor plate fastening rods 107 are secured to the hold-down plate 105 and extend upward through the block and through respective holes 109 in the anchor 15 plate 104. The holes are equally spaced around an outer circular ring. The upper end portion of each fastening rod 107 is threaded to take one or more nuts 108 to securely attach the anchor plate to the reinforcing structure 102 of the precast concrete block 101. The fastening rods 107 and embedded hold-down plate 105 can assist in reinforcing the block. 20 The interface zone between the top face 106 of the block 101 and the underside of the anchor plate 104 may be filled with grout (not shown in the figures) to help stabilise the plate on the block and bond the plate to the block. The grout also provides a seal that prevents rain water from reaching and causing corrosion of the embedded parts of the fastening rods 107. 25 The top face 106 of the block 101 has a circular central portion 103 inside the inner circular perimeter of the annular anchor plate 104. This central portion 103 is countersunk below the level of the surrounding portion of the top face 106. The top face of the block may be provided with a fall to the outer edges to assist with drainage and reduce build up of moisture around the base end of a pole or tower or other superstructure supported by the block. 30 As best seen in Figure 1, six ducts 110 are cast into die block 101. Each duct extends from a duct opening 112 at a side wall of the block, though the body of the block, to exit at a respective duct opening 114 in the countersunk portion 103. The six duct openings in the countersunk portion are arranged in two rows, with three duct opening in each row. The three ducts from 2828992-1 -11 one row follow curved paths to respective duct openings at one side face 116 of the block. The three ducts from the other row follow curved paths to respective duct openings at the opposite side face of the block. The three duct openings at each side face are at three respective depths above the bottom of the block. The ducts pass through the block between reinforcing rods to 5 provide clear passage for electrical cables and the like from outside the block to the base of a superstructure fitted to the anchor plate, for example to the interior of a monopole tower fitted to the anchor plate. Some reinforcing rods can be trimmed locally to accommodate the ducts, with additional 'U' bars added, if necessary, to maintain the integrity of the reinforcement of the block. 10 As best seen in Figure 1, seven through-holes 120 are cast in the concrete block. The holes may be formed by placement of tubes prior to casting the concrete block. Tubing made of galvanised steel strip, eg Drossbach tubing, is suitable for this purpose. The seven through-holes 120 extend from the bottom face of the block, vertically upward through the block, to respective openings 15 122 in the countersunk portion 103 of the top face 106 of the block. The openings 120 are equally spaced around an inner circle to lie outside the duct openings 114 but inside the inner perimeter of the annular anchor plate 104 and the outer circle of plate holes 109 (best seen in Figure 4) for the ten reinforcing rods 107. 20 The seven through-holes 120 respectively accommodate the seven reinforcing rods 222 (best seen in Figures 4 and 5), or the seven reinforcing rods 322 (best seen in Figures 7 and 8). The seven rods 222 or 322 extend upward from a substructure on which the block of the foundation interface assembly can be mounted, as will be discussed further below. 25 Figures 3, 4 and 5 show one preferred embodiment in which the foundation interface assembly 100, shown in Figures 1 and 2 and described above, is mounted on a substructure comprising a set of six precast concrete pads. Each pad is 3 metres long, 1 metre wide and 0.3 m high. Each pad of the lower layer is reinforced by an embedded reinforcing structure 206. Each pad of the upper layer is reinforced by an embedded reinforcing structure 208. The reinforcing structures 30 follow well-known industry-accepted practices and are made from a lattice of steel rods which are tied or welded together at some of the points where the rods overlie or intersect one another. The steel rods are shaped with right angled bends to extend generally in three mutually orthogonal directions that are each substantially parallel to a respective pair of opposite faces of the block. 2828992-1 - 12 The six pads are arranged in top and bottom layers. Three bottom pads 202 are aligned in one direction and laid side by side. Three top pads 204 are aligned at right angles to the bottom pads and laid side by side on the bottom pads. 5 Each of the two outer pads of the bottom layer has an array of twelve bolts 210. Each bolt 210 extends vertically upward, beyond above the upper face 212 of the pad, from a lower bolt portion 214 that is embedded in the pad as part of the reinforcing structure. Each bolt extends beyond the upper face of the pad by a relatively short distance that is slightly greater than the thickness of 10 a pad of the top layer. The upper end of each bolt is threaded. This array of twelve bolts is made up of three sets, each set having four bolts and occupying a respective 1m x 1 third of the upper pad face, ie a 1 x 1 metre portion of the upper face. The middle pad 219 of the bottom layer has a similar, but not identical, array of upwardly 15 extending reinforcing bolts. Each of the two outer end thirds of the middle pad has a set of four bolts 220 which extend upward, similarly to the bolts 210 of the outer pads of the bottom layer. However, the middle third of the middle pad has a set of seven hold-down bolts 222 which each extend vertically upward, beyond the upper face of the pad, from a lower bolt portion 224 that is embedded in the pad where it is attached to a hold-down ring 225 as part of the reinforcing 20 structure. The set of seven hold-down bolts are equally spaced around a circle to correspond to the circular arrangement of the seven through-holes 120 that are cast in the concrete block 101, as described above. Each of these hold-down bolts extends above the upper surface of the middle pad of the bottom layer of pads by a relatively long distance that is slightly greater than the sum of the thickness of a pad 204 of the top layer and the height of an interface block 101 to 25 be mounted on the pads, as will be explained further below. The upper end of each of the hold down bolts is threaded. Each of the three pads of the top layer has an array of vertical through-holes 230 extending between the upper and lower faces of the pad. Each hole is located in a position corresponding 30 to a respective bolt 210 or 220 extending upwardly from a lower pad. The middle pad of the top layer also has a circular array of vertical through-holes 231 extending between the upper and lower faces of the pad. These through-holes 231 ate located in a 2828992-1 - 13 positions corresponding to respective rods 222 extending upwardly from the centre of the middle lower pad. At the site where the foundation is to be installed, topsoil is excavated down to a depth of about 5 1.5 metres below the surrounding undisturbed ground level. The base of the excavated area is compacted and built up with compacted layers of hard fill. A grout blanket is placed on the prepared base. The three pads 202 of the bottom layer are placed side by side on the grout blanket and levelled. 10 The three pads 204 of the top layer are placed side by side on the bottom layer of pads, with the upwardly-extending bolts 210 and 220 extending respectively through corresponding through holes 230 in the pads 204 of the top layer, and the upwardly- extending rods 222 extending respectively through corresponding through-holes 231 in the middle of the middle pad of the top layer. The interface zone between the top and bottom pad layers can be filled with a grout. 15 Washers and nuts 234 are fitted on the threaded upper ends of each of the shorter length bolts. Ihe top pads are levelled, and the nuts 234 are tightened to securely fasten the pads of the top and bottom layers together to form a substructure unit. The block 101 described above is placed on the unitary arrangement of pads with the seven 20 upwardly extending hold-down bolts 222 extending respectively through the corresponding through-holes 120 in the block. The interface zone between the top layer of pads 204 and the underside of the block 101 can be filled with a grout 235. The diameter of the through-holes 120 is greater than the diameter of the hold-down bolts 222. 25 Grout is poured into the through-holes to fill the space around the bolts and securely locate and bond the bolts within the through-holes. Washers and nuts 236 are fitted on the threaded upper ends of each of the hold-down bolts 222 and the nuts tightened to securely fasten the block 101 to the substructure unit to form a foundation unit, as best seen in Figure 3. 30 The upper faces of the pads 204 in the top layer are sloped with a fall of about 1 in 30 from the sides of the block 101 to the nearest outer edge of the substructure unit to reduce the likelihood of water or soil moisture remaining neat the block or collecting on the substructure unit. A waterproof sealant layer 240, shown in Figure 5, is spread over the exposed upper face of the 2828992-1 -14 pads of the upper layer to seal the exposed ends of the bolts 210 and 220, and the corresponding washers and nuts 234. A pole or tower (not shown in the figures) is placed with its base on the anchor plate 104 and the 5 base of the pole or tower fastened to the anchor plate. In one embodiment of a tower on a pad foundation, the lower end of the tower has an annular base anchor plate with a circular array of through-holes corresponding to the circular array of holes 109 in the anchor plate 104 of the foundation interface block 101. In this case, the washers 10 and nuts 108 are removed from the threaded ends of the rods 222, the tower positioned with its base anchor plate sitting on the anchor plate 104 and the washers and nuts 108 replaced on the threaded ends of the rods 222 and tightened down to secure the tower to the foundation. In-ground cabling 250 (shown in Figure 5) is directed through the ducts 110 in the block 101 and 15 up into the interior of the base of the tower. The cabling may connect to a lightning rod, antennae, or other devices carried on the pole or tower. Figures 6, 7 and 8 show another preferred embodiment, in which the foundation interface assembly 100, shown in Figures 1 and 2 and described above, is mounted on a substructure 20 comprising a pile 300. The pile is a concrete pile that is preferably poured in-situ. The pile is reinforced by a reinforcing structure 302 embedded in the poured concrete body 303 of the pile. The reinforcing structure follows well-known industry-accepted practices and is made from a lattice of steel rods which are tied or welded together at somc of the points where the rods overlie or intersect one another. The pile 300 and its reinforcing structure 302 may extend up to 25 20 metres or more into the ground. The embedded reinforcing structure 302 includes a circular array of seven parallel reinforcing bars or rods 322 which extend vertically upward, beyond the top end of the poured concrete 323 by a distance that is slightly greater than the height of the interface block 101 to be mounted on 30 top of the pile, as will be explained further below. A series of circular rings 324, or a helix, is formed from steel rod and is embedded in the poured concrete 303. The seven vertical rods are encircled by the rings or by the helix. The seven rods are equally spaced around a circle to correspond to the circular arrangement of seven through-holes 120 that are cast in the concrete block 101, as described above. At least the upper end 325 of each of the seven rods is threaded. 2828992-1 15 At the site where the foundation is to be installed, soil is excavated to a depth of about 1 metre below the undisturbed ground level surrounding the site and soil at the base of the excavation removed to provide the effective form work for shaping the pile to be pouted in situ. For 5 example, an augur may be used to form a substantially cylindrical hole at the base of the initial excavation- The reinforcing structure 302 is placed in the hole and concrete poured to form the pile 300. After the pouted concrete is cured, the bottom of the surrounding excavated area is filled with 10 hard fill, and the hard fill compacted in a layer 326 (seen in the cross-sectional view of Figure 8), to fill around the pile 300, up to the top level of the pouted concrete of pile body 303. A 25mm thick blanket of grout 328 is applied over the upper end surface of the poured concrete pile and on the compacted hard fill layer 326 immediately surrounding the pile to provide a bed 15 for the block 101 described above. The block 101 is then placed on the grout 328 with the seven upwardly extending rods 322 extending respectively through the corresponding through-holes 120 in the block. The diameter of the through-holes 120 is greater than the diameter of the upwardly extending 20 rods 322. Grout is poured into the through-holes to fill the space around the rods and securely locate and bond the rods within the through-holes. Washers and nuts 330 are fitted on the threaded upper ends 325 of each of the rods 322 and the nuts tightened to securely fasten the block 101 to the pile substructure 300 to form a foundation unit, as shown in the perspective view of Figure 6. 25 A pole or tower (not shown in the figures) is placed with its base on the anchor plate 104 and the base of the pole or tower fastened to the anchor plate. In one embodiment of a tower on a pile foundation, the lower end of the tower has an annular 30 base anchor plate with a circular array of through-holes corresponding to the circular array of holes 109 in the anchor plate 104 of the foundation interface block 101. In this case, the washers and nuts 108 are removed from the threaded ends 325 of the rods 322, the tower positioned with its base anchor plate sitting on the anchor plate 104 and the washers and nuts 108 replaced on the threaded ends of the rods 322 and tightened down to secure the tower to the foundation. 2828992-1 - 16 The pile foundation includes a first circular array of fasteners for securing the base of the tower to the foundation interface block and a second circular array of fasteners for securing the block to the pile. The first and second circular arrays of fasteners are preferably concentric and the 5 radius of the first circle is larger than that of the second circle. This arrangement of inner and outer fasteners at the capping block 101 allows the base or foot plate of a monopole tower base to be fitted to a pile having a relatively smaller diameLer. In-ground cabling 330 (shown in Figure 8) is directed through the ducts 110 in the block 101 and 10 up into the interior of the base of the tower. The cabling may be connected to a lightning rod, antennae, or other devices carried on the pole or tower. Figures 9 and 10 show details of modifications to the pile foundation seen in Figure 6. These modifications allow levelling of the block 101 and the anchor plate 104. The reinforcing bars or 15 rods 322 arc threaded, at least at their upper ends 325. Threaded levelling nuts 401 are screwed down onto the upper ends of the rods 322. A levelling plate 403 has a circular array of through holes 405 corresponding to the circular arrangement of rods 322. After the reinforcing structure 302 is placed in the hole formed in the ground, the levelling plate is placed on the levelling nuts with the rods 322 extending through the through-holes 405 in the plate. The levelling nuts may 20 be screwed up or down to level the plate. Concrete is then poured into the hole to form the pile 300. The levelling plate may be annular with an aperture 407 in an inner zone to facilitate pouring of the concrete into the hole. After the concrete has at least partially cured, the block 101 can be placed on the levelling plate 25 with the rods 322 extending upward and respectively through the through-holes 120 in the block. The block tests on the plate and is substantially level. The block can be securely fastened to the pile substructure by tightening nuts 330 onto the threaded upper ends 325 of the rods 322. A second array of levelling nuts 411 can be used to provide a second or alternative levelling 30 adjustment. The second levelling nuts 411 are screwed down onto the threaded upper end portion of the anchor plate fastening rods 107 which protrude upwardly from the top face 106 of the block 101. The anchor plate 104 is placed on the second levelling nuts 411 with the rods 107 extending respectively through the through-holes 109 in the anchor plate. The second levelling nuts may be screwed up or down to level the anchor plate. This allows correction and/or finer 2828992-1 - 17 adjustment of the levelling provided by the levelling plate located under the block 101. The space between the anchor plate and the top of the block 101 may be filled with grout 415. The base or foot plate (not shown in the figures) of a tower or other superstructure to be supported on the foundation is placed on the anchor plate with the rods 107 extending upward through respective 5 holes provided in the base or foot plate. Nuts 108, optionally with washers 413, are screwed onto the threaded rods 107 and tightened to secure the tower or other superstructure to the foundation. The anchor plate 403 may be dispensed with and the base or foot plate of the tower or other 10 superstructure placed directly on the second levelling nuts 401. In each of the embodiments described above and shown in Figures 3 to 10, the excavated area can be filled with hard fill after completion of the installation of the block on the pad or pile substructure, and after any in-ground cabling has been routed through the ducts. The hard fill is 15 compacted in layers to cover the substructure unit and is optionally covered with a layer of poured concrete or top soil, for example, to restore the ground level. The hard fill compacted over and around the substructure and around block serves to strengthen the foundation, and in particular provides resistance to lateral loads placed on the foundation. 20 Alternatively, the block, and optionally the pad substructure, may be installed above ground level if the loadings on the foundation do not require the added strength provided by the subterranean installation of these components. 25 The precast block 101 and pads 202 and 204 described above are preferably fitted with lifting points or eyes (not shown in the figures) to facilitate lifting and positioning of the precast concrete components, for example by a crane. The precast substructure pads described above may have vertical holes (not shown in the figures) 30 to allow for earthing rods, or ground anchors for extra foundation strength. The concrete of the precast block and pads, or the pile poured in-situ, may include reinforcing fibres embedded in the concrete. For example, the precast components may be lightened by adding reinforcing fibres and thereby reducing the amount of steel reinforcing required. 2828992-1 - is The rods, bolts, nuts, washers and lifting eyes in the embodiments described above may be protected by hot dip galvanising or by any other suitable corrosion-resistant coating or plating. 5 The foundations described above are suitable for supporting monopoly or lattice towers for lighting and cellular communications antennae, and other applications. In alternative embodiments, the foundation interface block is not shaped as described above, but instead has a horizontal cross-section that is round or circular, or triangular, or polygonal, to 10 allow for aesthetics or other considerations. The use of the precast concrete components reduces the on-site construction period by reducing or eliminating the waiting time otherwise needed to allow for the curing of concrete poured on site. The use of precast concrete components also means that these components can be precast 15 under controlled conditions so that the components can consistently meet design requirements without any uncertainties that otherwise could be caused if using concrete poured on-site, for example by weather, by inadequately skilled operators, or by locally-supplied concrete. Off site precasting of the concrete components under controlled conditions with materials of a known and reliable standard can also allow the sizes or design strengths of components to be reduced 20 because there is no need to over-size or over-design to allow for uncertainties in materials or conditions during construction. 2828992-1

Claims (19)

1. A foundation interface assembly, for supporting a superstructure attached to the foundation interface assembly when the foundation interface assembly is placed on and attached to a 5 substructure, the foundation interface assembly comprising a precast concrete block, a reinforcing structure, and a top plate; wherein: the block is reinforced by the block reinforcing structure; the block reinforcing structure is partially embedded in the block during casting of the block; 10 portions of the block reinforcing structure extend above a top surface of the block for attachment to a base end of the superstructure to be supported by the foundation interface assembly; the block has a plurality of through-holes, each through-hole extending upwardly from a downward facing surface of the block, through the block, to an upward-facing surface of the 15 block; the top plate is at the top surface of the block; the top plate has a plurality of through-holes; and the portions of the block reinforcing structure extend above the top surface of the block and extend respectively through the through-holes in the top plate for attachment to the base end 20 of the superstructure to be supported by the foundation interface assembly.

2. A foundation interface assembly as claimed in claim 1, wherein the portions of the block reinforcing structure that extend above the top surface of the block are arranged in a pattern which surrounds the through-holes in the block. 25

3. A foundation interface assembly as claimed in claim 1, wherein: the though-holes in the top plate are arranged on the circumference of a first circle; the though-holes in the block are arranged on the circumference of a second circle; the first and second circles are concentric; and 30 the radius of the first circle is larger than the radius of the second circle.

4. A foundation interface assembly as claimed in claims 1, 2 or 3, wherein: the top plate is a flat annular plate with an aperture through an inner zone of the plate;

2828992-1 - 20 a duct, for accommodating passage of one or more electrical cables or the like, extends from a first duct opening at a side wall of the block, and through the block, to a second duct opening at the upward-facing surface of the block; and the second duct opening is aligned with the aperture in the annular plate.

5 5. A foundation interface assembly as claimed in any one of the preceding claims, wherein: each of the portions of the block reinforcing structure that extend above the top surface of the block is a steel rod with a threaded upper end portion; threaded nuts are fitted onto the threaded upper end portions of the steel rods to lie 10 below the top plate; and the top plate rests on the threaded nuts which can be screwed up or down the steel rods to level the top plate.

6. A foundation comprising the foundation interface assembly as claimed in any one of claims 1 15 to 5, wherein: the foundation interface assembly is fitted to a substructure; the substructure comprises a pad assembly; the pad assembly comprises at least a first pad; the, or each, pad of the pad assembly is a concrete pad that is precast before assembly of 20 the pad assembly; the first pad is reinforced by a first pad reinforcing structure; a first portion of the first pad reinforcing structure is embedded in the first pad; second portions of the first pad reinforcing structure extend above an upper face of the first pad and extend respectively through the through-holes in the block; and 25 the block is fastened to the first pad reinforcing structure by respective first fasteners fitted to the second portions of the first pad reinforcing structure.

7. A foundation as claimed in claim 6, wherein: the first pad is a lower pad; 30 the pad assembly comprises at least one upper pad; the upper pad is reinforced by a second pad reinforcing structure which is embedded in the upper pad; the upper pad has through-holes each of which extend from a bottom surface of the upper pad and through the upper pad to an upper face of the upper pad; 2828992-1 - 21 third portions of the first pad reinforcing structure extend above the upper face of the first pad and extend respectively though a first subset of the through-holes in the upper pad; and the upper pad is fastened to the first pad reinforcing structure by respective second fasteners fitted to the upper ends of the third portions of the first pad reinforcing structure. 5

8. A foundation as claimed in claim 7, wherein at least one of: an interface zone between the lower first pad and the upper pad; an interface zone between the upper pad and the block; or at least one of the through-holes in the block; 10 is filled with grout.

9. A foundation comprising the foundation interface assembly as claimed in any one of claims 1 to 5, wherein: the foundation interface assembly is fitted to a substructure; 15 the substructure comprises a pile; the pile is reinforced by a pile reinforcing structure; a first portion of the pile reinforcing structure is embedded in the pile; second portions of the pile reinforcing structure extend above an upper end of the pile to extend respectively though the through-holes in the block; and 20 the block is fastened to the pile reinforcing structure by respective first fasteners fitted to the second portions of the pile reinforcing structure.

10. A foundation as claimed in claim 9, wherein an interface zone between the pile and the block is filled with grout. 25

11. A foundation as claimed in claim 9 or claim 10, the foundation further comprising a levelling plate, wherein: the levelling plate has a plurality of through-holes; each of the second portions of the pile reinforcing structure is a threaded reinforcing rod; 30 threaded levelling nuts are respectively fitted onto the threaded reinforcing rods; the threaded reinforcing rods extend upward through the through-holes in the levelling plate; the levelling plate rests on the threaded levelling nuts; and 2828992-1 - 22 the threaded levelling nuts can be screwed up or down the reinforcing rods to level the levelling plate prior to placement of the block on the levelling plate and location of the reinforcing rods respectively in the through-holes in the block. 5

12. A foundation as claimed in claim 11, wherein an interface zone between the pile and the levelling plate is filled with grout.

13. A foundation as claimed in any one of claims 9 to 12, wherein the through-holes in the block are filled with grout after the second portions of the pile reinforcing structure are located in the 10 through-holes in the block.

14. A method of constructing a foundation as claimed in claim 6 at a site, comprising the steps of: 1. precasting the first pad; 15 2. placing the first pad on a ground surface at the site with the second portions of the first pad reinforcing structure extending upward; 3. placing the foundation interface assembly over the first pad with the second portions of the first pad reinforcing structure extending respectively upward through the through-holes in the block; and 20 4. fastening the foundation interface assembly to the first pad by respectively fitting the first fasteners to upper ends of the second portions of the first pad reinforcing structure.

15. A method of constructing a foundation as claimed in claim 7 or claim 8 at a site, comprising 25 the steps of: 1. precasting the first pad and the upper pad; 2. placing the first pad on a ground surface at the site with the second portions of the first pad reinforcing structure extending upward; 3. placing the upper pad on the first pad, with the second portions of the first pad 30 reinforcing structure extending upward through a second sub-set of the through holes in the upper pad, and the third portions of the first pad reinforcing struc ture extending upward through the first sub-set of the through-holes in the upper pad; 4. fastening the upper pad to the first pad by respectively fitting the second fasteners to the upper ends of the third portions of the first pad reinforcing structure; 2828992-1 - 23 5. placing the foundation interface assembly over the upper pad, with the second portions of the first pad reinforcing structure extending upward and respectively through the through-holes in the block; 6. fastening the foundation interface assembly to the pad assembly by respectively fitting 5 the first fasteners to upper ends of the second portions of the first pad reinforcing structure.

16. A method of constructing a foundation, as claimed in claim 14 or claim 15, wherein prior to placing the first pad in Step 2, the ground surface is prepared by the steps of: 10 A. excavating topsoil from the site; B. optionally compacting at least an upper layer of exposed subterranean material remaining at the site after excavation of the topsoil; C. optionally placing and compacting hard fill at the site; and D. overlaying the upper layer of subterranean material compacted in Step B, or the hard 15 fill placed and compacted in Step C, with a grout layer.

17. A method of constructing a foundation as claimed in claim 9 or claim 10 at a site, comprising the steps of: 1. forming an in-ground pile cavity at the site; 20 2. placing the pile reinforcing structure at least partially in the cavity; 3. pouring concrete into the cavity to embed the first portion of the pile reinforcing structure; 4. allowing the poured concrete to at least partially cure to form the pile; 5. placing the foundation interface assembly over the pile with the second portions of 25 the pile reinforcing structure extending upward through the through-holes in the block; and 6. fastening the foundation interface assembly to the pile by fitting the first fasteners to respective upper end portions of the second portions of the pile reinforcing structure. 30

18. A method of constructing a foundation as claimed in claim 11 or 12 at a site, the method comprising the steps of: 1. forming an in-ground pile cavity at the site; 2. placing the pile reinforcing structure at least partially in the cavity; 3. fitting the threaded levelling nuts respectively onto the threaded reinforcing rods; 2828992-1 -24 4. resting the levelling plate on the levelling nuts with the threaded reinforcing rods extending upward through the through-holes in the levelling plate; 5. screwing the levelling nuts up or down to level the levelling plate; 6. pouring concrete into the cavity to embed the first portion of the pile reinforcing 5 structure; 7. allowing the poured concrete to at least partially cure; 8. placing the foundation interface assembly on the levelling plate with the second portions of the pile reinforcing structure extending upward through the through holes in the block; and 10 9. fastening the foundation interface assembly to the pile by fitting the first fasteners to respective upper end portions of the second portions of the pile reinforcing structure.

19. A method as claimed in claim 16, 17 or 18, wherein hard fill is placed and compacted around the foundation interface assembly and the site reinstated to correspond to the level of 15 undisturbed ground surrounding the site. 2828992-1