TECHNICAL FIELD

This disclosure relates to a foundation and its method of construction. The foundation has applications in the construction of roads, buildings, pavements, seawalls, wave & subsea mats, retaining walls, etc.

BACKGROUND ART

A foundation for roads, buildings, pavements, seawalls, retaining walls, and the like is constructed to withstand the usual loads that are applied thereto by persons, vehicles, overlying structures, equipment, machinery and natural phenomena (e.g. weather and water such as waves, tides, currents, etc).

Such loading can include static and dynamic forces including vibratory and shock loading. Such static and dynamic forces are transmitted through to the underlying ground. If the ground is soft and/or water-laden the forces and loads can cause the ground to be (or become) compressed or compacted and thereby subside. With water-laden ground the fluids therein can be pumped laterally away from under the foundation. Over time, this subsidence can lead to degradation of the foundation. In either case, there will be a requirement for ongoing maintenance, remediation or replacement of the foundation.

US 7,470,092 discloses arranging a plurality of cylindrical segment elements in a foundation. US 7,470,092 teaches that each cylindrical segment element can be formed from a tubular or ring-shaped component and, in this regard, teaches that such a component can be formed from, inter alia, a tyre that has had both sidewalls removed therefrom. Further, US 7,470,092 teaches that, in the foundation, the cylindrical segment elements are arranged on a support surface in the form of a graded space of ground and/or the surface of another cylindrical segment.

W 2000/008265 to the present applicant discloses a foundation structure in which a lowermost mattress of tyres is wrapped in a porous sheet such as a geofabric cloth. The purpose of the wrapping of the lowermost tyre mattress with the porous sheet is to allow the passage of water across the lowermost mattress whilst preventing the ingress of relatively finer material into the fill, the latter which can otherwise lead to degeneration of the foundation. It is to be understood that a reference to the background and prior art does not constitute an admission that the background and prior art forms a part of the common general knowledge in the art, in Australia or any other country.

SUMMARY OF THE DISCLOSURE

Disclosed herein is a method of constructing a foundation at a surface. As set forth above, the foundation can have applications in the construction of roads, buildings, pavements, seawalls, wave & subsea mats, retaining walls, etc. In this regard, such structures may be constructed/erected over the foundation that is produced by the method as disclosed herein.

The method comprises laying a barrier material over the surface. The barrier material layer to be used may be specified by a design engineer for a given application. The barrier material layer typically comprises a continuous sheet which forms a single sheet layer within the foundation. Thus, a barrier material sheet (e.g. that comprises one or more lengths of sheet) can be laid out over e.g. a prepared surface. The method thus already contrasts with the arrangements disclosed in US 7,470,092, the arrangements of which employ no such barrier material in the foundation.

The barrier material may take the form of a geotextile material. The geotextile material may comprise a fabric of a woven polymer fibre (e.g. of polypropylene, polyester, etc.). Alternatively, the geotextile material may take the form of a combination of a non-woven geotextile incorporating a geo-grid. The geo-grid may be formed from a polymer such as polypropylene, polyester, polyvinyl alcohol or polyethylene. Such geotextile materials are known to provide excellent tensile performance and resistance. Other geotextile materials can be employed, including a non-woven geotextile or yet-to-be-developed geotextile materials.

Alternatively, the barrier material may take the form of a waterproof membrane. Such a membrane may, for example, be employed in very wet applications. The waterproof membrane may comprise polymeric sheeting (e.g. high density polyethylene, polypropylene, etc.). The waterproof membrane may instead comprise a sheeting of tightly woven polymeric fibre (e.g. a fibre treated so as to be hydrophilic).

The barrier material may be supplied in the form of a roll of long sheeting. For example, when the barrier material is a geotextile, it may comprise ~ 80 kN woven geotextile, ~ 5.1 m width. The barrier material may be laid (e.g. rolled) out along and over the surface. Depending on the required width of foundation, adjacent and generally parallel lengths of barrier material may be overlapped to form the single sheet barrier material layer. The surface over which the barrier material is laid may comprise ground that is prepared so as to receive a layer of the barrier material thereat. For example, the ground may be cleared, excavated, in-filled, graded, compacted, etc. to make it suitable for the layer of barrier material and to make it suitable for having a foundation formed thereat. The preparation of the ground may include the formation of an embankment over existing ground.

The method also comprises placing a plurality of tyres that have a single sidewall removed therefrom in a laid-flat arrangement. Thus, a remaining sidewall of each resultant tyre cell can lie over and adjacent to the layer of barrier material.

This arrangement can allow the tyres to be in-filled with a fill material (i.e. the open, upwardly-facing side of the tyres provides a receptacle for the fill material). This arrangement can further allow the fill material to be compacted within the tyres. As explained in further detail hereafter, the compacting of the fill material whilst the remaining tyre sidewall overlays a layer of barrier material has a number of performance advantages over e.g. the arrangements of US 7,470,092 and WO

2000/008265.

The removal of the tyre side wall converts the tyre into an engineered cellular structure (i.e. it is no longer a tyre). Hereafter, this engineered cellular structure will be referred to as a "tyre cell".

In some applications, more than one layer of tyre cells can be employed. For example, in very poor ground conditions, multiple tyre cell layers may be employed to increase load spreading performance. Multiple tyre cell layers may also be employed where larger format tyre cells are either not available or are in short supply. Where multiple tyre cell layers are employed, one layer may be staggered with respect to another layer, i.e. such that a given overlying tyre cell can overlie, and thereby spread and transfer load to and over, multiple underlying tyre cells.

The tyres for producing the tyre cells may be used (i.e. second-hand) tyres that can be pre-selected so as to be fit for purpose. The tyre sidewall may be removed prior to transporting each tyre cell on site, or may be removed on site. The method can therefore provide another means of using tyres that would likely otherwise be stockpiled or disposed of in landfill, or burnt, etc.

The method additionally comprises in-filling the tyre cells with a fill material in a manner such that the underlying layer of barrier material is placed into tension between adjacent tyre cells. Thus, the filled tyre cells, together with the underlying tensioned barrier material layer, can behave as a composite engineered product. As set forth above, the barrier material layer typically comprises a continuous sheet which forms a single sheet layer within the foundation. Thus, the remaining tyre side wall sits in engagement with this barrier material single sheet layer. The method thus contrasts with US 7,470,092 (in which no such barrier material layer is employed) and also contrasts with WO 2000/008265 (in which the lowermost tyre blanket is wrapped within a porous material). Because the remaining sidewall of each tyre cell overlies and contacts the underlying sheet layer of barrier material, in use, when static and dynamic loads/forces are applied to the foundation (including in a lateral direction), these loads/forces can be attenuated and accommodated by e.g. the increased tension in the underlying layer of bamer material between the adjacent tyre cells. The wrapped lowermost tyre blanket of WO 2000/008265 is unable to perform in this manner, because the entire lowermost tyre blanket is wrapped (i.e. in WO

2000/008265 the porous geofabric material overlies the tyre blanket and also extends around the perimeter of the tyre blanket; the wrapping with a geofabric is also for a different purpose - i.e. to prevent fines ingress). In the present method, the barrier material does not overlie the tyre cells. In the present method, the barrier material does not extends around the perimeter edge of the layer of tyre cells.

In the method as disclosed herein, the fill material may be compacted within the tyre cells in a manner such that an optimal degree of pre -tensioning is achieved in the underlying barrier material layer between the adjacent tyre cells. Such compaction may be controlled by way of the type and weight of compacting machinery employed, the number of heavy vehicle passes, etc. The resultant composite product is thus "pre-tensioned" in a suitably controlled manner.

In use, the filled tyre cells can provide a high degree of load spreading for a comparatively low depth of material. Further, the tensioned barrier material layer in conjunction with the filled tyre cells (i.e. the pre-tensioned composite product) can act to spread this load over a large area. In this regard, the tread of each tyre cell typically has a high degree of hoop strength, which enables each tyre cell to act as a cellular confinement for the fill material, thus enabling spreading of the applied load over a larger base area. The tensioned barrier material layer can also reduce lateral displacement of the filled tyre cells in use.

Another benefit of employing filled tyre cells is their ability to attenuate and/or absorb static and dynamic loads and forces, including vibratory and shock loads, which can be transmitted through the foundation (e.g. by the passage thereover of vehicles, waves, etc). This ability to attenuate and/or absorb such loads and forces arises from the inherent material properties of the high performance rubber incorporated into the tyre of the cell. The attenuation and absorptive characteristics of the tyre cells can thereby extend the life of the foundation, and reduce or slow ground compression, compaction and/or pumping, leading to a reduction in frequency of maintenance or reconstruction of the foundation. Thus, within the foundation, each tyre cell can be seen to provide force/load-attenuation, force/load- absorbing, and a force/load-spreading cellular confinement.

As explained in more detail hereafter, the composite engineered product (in-filled tyre cells on a layer of barrier material) can also reduce the amount of excavation required at a given site, and also the amount of engineered fill required to replace the excavated material. In addition, the amount of compactive effort required to compact the engineered fill can be reduced.

In an embodiment, at least some of the tyre cells may be secured to each other. For example the tyre cells may be secured to each other by a fastener or a tying element that is arranged to extend through the treads of adjacent tyre cells. One or more fasteners may be employed such as bolts, rivets, rods. The tying element may take the form of a rope, tendon or cable.

In an embodiment, the method may further comprise arranging a capping layer directly on the in-filled tyre cell layer. The capping layer may be formed from the same or a different fill material as employed for in-filling the tyre cells.

In an embodiment, the method may further comprise arranging a further barrier material layer over the in-filled tyre cells prior to and/or after arranging the capping layer thereon. In an embodiment, the method may further comprise filling each tyre cell firstly with a fill material of relatively coarse grade, and then topping the coarse grade fill material with a separate fill material of a relatively finer grade than the coarse grade. In an embodiment, the fill material may comprise one or more of: crushed rock such as fine crushed rock; a cementitious material; or another stabilised fill material. The fill material may alternatively or additionally comprise site-won material, such as material that is excavated from the site prior to constructing the foundation. This can reduce the amount of new fill material required, and hence can reduce construction costs, as well as reducing excavated site material disposal costs.

In an embodiment, the tyre cells may be laid over the barrier material layer in rows.

In one variation, a given row may be offset from immediately adjacent row(s) by half a tyre cell. This can provide a type of honeycomb, close-packed pattern to the laid-flat arrangement of the tyre cells, which can enhance the spreading of the load as well as the attenuation and accommodation of dynamic forces (including vibratory and shock) that are transmitted through the foundation in use. Adjacent tyre cells are able to work together to receive and absorb such loadings and forces.

In another variation, the rows may be laid in a grid (square) pattern, so as to produce aligned rows and columns of tyre cells. Other laying patterns are possible depending on the application.

In an embodiment, the tyre cells may be laid such that a given tyre cell closely faces or touches the two adjacent tyre cells in its row and, in addition, closely faces or touches two adjacent tyre cells in the immediately adjacent row(s). In a variation, at least some of the plurality of tyres may have both sidewalls removed therefrom.

Also disclosed herein is a foundation for location at a surface, such as can be produced by the method as set forth above.

The foundation as disclosed herein comprises a plurality of tyres arranged at the surface in a laid-flat arrangement.

The foundation also comprises a fill material in-filling at least some of the tyres. The foundation further comprises an elongate securing element that is arranged to extend through the tread of a given tyre at a first tread location. The elongate securing element is also arranged to extend through the given tyre (e.g. inside the hollow of the given tyre from one side to the other). The elongate securing element is further arranged to extend through the tread of the given tyre at a second tread location. The employment of an elongate securing element that extends through a first tread location, through the tyre, and then through a second tread location (e.g. from one side to the other), contrasts with the discrete bolt arrangement disclosed in Fig. 12B of US 7,470,092 and also contrasts with the various discrete tying arrangements illustrated in Figs. 31-42 of WO 2000/008265.

For example, the elongate securing element may be arranged to extend from either the first and/or second tread location and through the tread of another tyre that is arranged at the surface adjacent to the first and/or second tread location. In this regard, multiple such tyres may be secured together by a single elongate securing element. Thus, the elongate securing element can be employed to produce an integrated tyre mattress. Such a mattress may comprise one or more rows of tyres, and one or more columns of tyres.

A first elongate securing element can be provided for securing together all of the tyres in the rows. The same or a further elongate securing element can be provided for securing together all of the tyres in the columns. Each row securing element can therefore cross over, within each tyre, with each column securing element (which may be one and the same elongate securing element).

The elongate securing element may comprise one or more elongate fasteners such as an elongate tie. The elongate tie may take the form of a rope, tendon, cable, tether, etc.

The securing together of adjacent tyres using such an elongate securing element can be used in certain applications that require enhanced lateral stability, with the resultant secured-together tyres functioning as a composite engineered unit. In an embodiment of the foundation as disclosed herein, the tyres may be arranged in rows at the surface. In an embodiment of the foundation, the elongate securing element may extend through the treads at first and second tread locations of three or more adjacent tyres in a given row. In an embodiment of the foundation, the elongate securing element may further extend through the treads at first and second tread locations of three or more adjacent tyres in a given column.

For example, the securing element may extend through the treads at first and second tread locations of all of the tyres in a given row. In a further example, the securing element may extend through the treads, at first and second tread locations, of all of the tyres in a given row and may then be looped back to extend through the treads, at first and second tread locations, of all the tyres in next a given row, and so on. Likewise, with all of the tyres in given column(s).

In an embodiment of the foundation as disclosed herein, the fill material may comprise material located at the surface (e.g. site-excavated or pre-existing site material) and/or additional "imported" fill material, as set forth above. When the fill material comprises pre-existing material located at the surface, such fill material may be such as to migrate into the tyres after they have been arranged at the surface in the laid-flat arrangement. For example, this migration of fill material may occur when the foundation is employed in underwater applications. In an embodiment of the foundation as disclosed herein, the additional fill material may comprise a cementitious material which may be allowed to cure within the tyres prior to or after being located at the surface. A certain number of the tyres may be provided with the cementitious material therein.

In an embodiment of the foundation as disclosed herein, the surface may be located under a body of water. For example, the foundation may be employed as a wave or sub-sea mat, or as a protective overlay for undersea cables, pipes, etc. In such applications, tyre sidewalls may have one or more holes formed therein to allow air to escape from within the tyre during arrangement of the tyres at the surface. Also, the pre-existing site material may then comprise sand or silt at the sub-sea location. In an embodiment of the foundation, at least some of the tyres may have a sidewall removed therefrom to form a tyre cell.

In an embodiment, the foundation may further comprise a barrier material that is laid over the surface. The barrier material may be as set forth above. A sidewall of each tyre may lie over and adjacent to the barrier material.

In an embodiment of the foundation, each of the tyres may be in-filled with a fill material that is compacted therein, in a manner such that the underlying barrier material is placed into tension between adjacent tyres, with the attendant advantages as outlined above.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a sectional schematic view of a first embodiment of a foundation as disclosed herein.

Figure 2 is a sectional schematic view of a second embodiment of a foundation as disclosed herein.

Figure 3 is a plan view of the tyre cells in one laid out variation, for use in the foundation of Figures 1 and 2. Figure 4 is a plan schematic view of a foundation as disclosed herein to illustrate one example layout arrangement of the tyre cells.

Figures 5A to 5E respectively show plan, a part lengthwise section, a transverse section, and plan and side detail views of a further embodiment of a foundation as disclosed herein, the foundation being suitable for use in subsea applications. Figures 6A to 6C respectively show plan, a detail plan section, and cross-sectional detail views of yet a further embodiment of a foundation as disclosed herein, the foundation also being suitable for use in subsea applications.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

In the following detailed description, reference is made to accompanying drawings which form a part of the detailed description. The illustrative embodiments described in the detailed description, depicted in the drawings and defined in the claims, are not intended to be limiting. Other embodiments may be utilised and other changes may be made without departing from the spirit or scope of the subject matter presented. It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings can be arranged, substituted, combined, separated and designed in a wide variety of different configurations, all of which are contemplated in this disclosure. Referring firstly to Figure 1, a foundation 10 is shown that has applications in the construction of roads, buildings, pavements, retaining walls, seawalls, wave mats, etc. The foundation 10 can be constructed directly over e.g. cleared ground, or may be formed on a pre-existing or newly constructed embankment. The foundation 10 can also be constructed on sloped ground (e.g. in the case of wave mats, seawalls, etc.). The foundation 10 can also be constructed to curve around landforms, etc. In each such application, the reference letter G is used hereafter to indicate the ground upon which the foundation is constructed.

The foundation 10 comprises a layer of barrier material in the form of a geotextile material layer or a waterproof membrane 12. Hereafter, the layer of barrier material will simply be referred to as material layer 12 (i.e. on the understanding that such a layer can comprise either a geotextile material or a waterproof membrane).

The foundation 10 also comprises a layer 14 that is formed from a plurality of tyre cells 16. Each tyre cell 16 is produced by removing one of the sidewalls from a tyre. The plurality of resultant tyre cells 16 are arranged in a side-by-side, laid-flat arrangement over the material layer 12, whereby the remaining sidewall of each tyre cell 16 overlies and contacts the material layer 12.

The foundation 10 comprises a suitable fill material for in-filling each of the tyre cells 16. The in-filling of each tyre cell 16 is such as to place the underlying material layer 12 into tension. That is, the remaining sidewall of each filled tyre cell presses down on the material layer 12 lying immediately thereunder, and thus pulls at (i.e. stretches) the material between adjacent tyre cells. Thus, the filled tyre cells, together with the underlying tensioned geotextile, work together as a pre-tensioned composite engineered product. This composite engineered product is pre-tensioned by the in-filling of each tyre cell 16.

In the foundation 10 of Figure 1, usually each tyre cell is filled firstly with a fill material of a relatively coarse grade (e.g. crushed rock, such as densely graded base course material). Each tyre cell is then topped with a separate fill material of a relatively finer grade than the coarse grade (e.g. a finer grade crushed rock, a coarse sand, etc). Some tyre cells may be filled with a cementitious material, with these tyre cells able to act as an anchor in the foundation. Other stabilised fill materials can be employed such as crushed basalt or other hard rock, etc., site-excavated material, crushed recycled concrete, crushed asphalt, crushed natural stones such as sandstone, crushed brick, crushed recycled bedding and fill sands, dune and river sands, etc. Such fill materials can have a cementitious material added thereto and can be modified to be water-resistant.

The fill material is typically deployed over the entire tyre cell layer 14, in-filling each tyre cell 16, and also filling up the spaces between tyre cells. The fill material is then usually compacted by a suitable machine (e.g. compactor, roller, excavator, tracked vehicle, etc). A predetermined tension in the composite engineered product can be achieved by employing suitably weighted machines and/or a number of compacting passes. As a result of such compaction, the tyre tread is placed under tension, as is the material layer 12. Thus, the "pre-tensioned" foundation is now ready to receive further structures thereon (e.g. slabs, roadways, road base, paving, capping, etc.).

Figure 1 shows fill material 18 extending above the tyre cell layer 14 to define an optional capping layer. This layer 18 may be further compacted, essentially down to the level of the tyre cell layer 14, prior to arranging a further structure over the foundation (e.g. such as a concrete slab, paving, road surface, road base, etc.). The capping layer 18 may also have a further layer of barrier material arranged thereover and/or thereunder.

Figure 1 also shows a transversely extending strip drain 20 that can be positioned over the material layer 12 at periodic intervals along the length and/or breadth of the foundation 10. The drain 20 can extend through or under the tyre cell layer 14. Each such drain 20 can allow any water that accumulates in the foundation in use to be drained away (i.e. at either side of the foundation). As best shown in Figure 2, each drain 20 can feed into larger collection drains or drainage-ways located alongside the foundation, and can also be vented to air, or into a specific drainage system.

Referring now to Figure 2, where like reference numbers denote like parts, a foundation 30 is shown that is formed into an embankment E. The embankment E can be specifically constructed above the ground to elevate the foundation 30 above multiple different land types, including land that is stable and land that is unstable or very soft, such as swamp land, marshes, sandy sub-soil, unstable clay or silt layers, etc. Alternatively, the embankment E can be a pre-existing embankment at an existing hill, rise, slope, etc., or may form part of the existing topography of the land on which the foundation is to be constructed.

As part of preparing the ground at the embankment E, the top of the embankment can be excavated a short distance down, sufficient for the material layer 12 and tyre cell layer 14, as well as for an optional capping layer 32. In addition, this capping layer 32 may also have a further layer 34 of barrier material arranged thereunder, i.e. between it and the fill material 16 above the tyre cell layer 14. Located to run along either side of each strip drain 20, so as to receive fluid therefrom, is a larger collection drain or drainage-way 36. Each drainage-way 36 is also vented to air via offtake vents 38.

The foundation 30 is otherwise constructed as per the foundation 10. Referring now to Figure 3, where like reference numbers denote like parts, a foundation 40 for a concrete slab 42 is shown. In this embodiment it will be seen that the concrete slab is laid directly onto the in-filled tyre cell layer 14. In addition, the material layer 12 is extended beyond the tyre cell layer 14, such that it locates under the concrete slab 42, between it and the ground G. The foundation 40 is otherwise constructed as per the foundation 10.

In each of the foundations as set forth above, the tyre cells 16 are typically produced from used (i.e. second-hand) tyres. The tyre cells 16 can be produced from a large format tyre, such as a truck tyre, or from a smaller format tyre such as an automotive vehicle tyre. In the case of large format tyres, a single tyre cell layer 14 is usually sufficient for construction of the foundation. Vehicle tyres can be employed when truck tyres are not available or are in short supply. When vehicle- derived tyre cells are employed, typically the foundation is constructed with a stack of tyre cell layers 14 (e.g. two + layers). An upper layer is typically staggered with respect to an adjacent lower layer, such that a given overlying tyre cell overlies, and is thereby able to spread and transfer load and forces over, multiple (e.g. 3) underlying tyre cells.

Before forming the tyre cells 16, each tyre is pre-selected (i.e. inspected and checked) so as to be fit for purpose. Because tyres are already a highly engineered and designed product (i.e. having high performance material properties), the tread of each tyre cell is able to provide a high degree of hoop strength in use in the foundation. Used tyres can thus be re-purposed (i.e. they would likely otherwise be stockpiled, disposed of in landfill, or burnt, etc). As will be explained hereafter, the tyre cells 16 provide a number of advantages to a foundation. One such advantage is the ability of the tyre cells to attenuate and absorb static and dynamic (including vibratory and shock) forces and loads which can be transmitted through the foundation. This ability is attributed to the material properties of the high performance rubber incorporated into the tyre cell. The attenuation and absorptive characteristics of the tyre cells enable them to receive, absorb and distribute such forces and loads. This can extend the life of the foundation, and reduce or slow ground compression, compaction and/or pumping. In turn, this results in a reduction in the frequency of maintenance and

reconstruction of the foundation.

The tyre sidewall can be removed prior to transporting each tyre cell 16 to a site. Alternatively, the tyre sidewall can be removed on site using a suitable portable machine (tyre-cutter). In some applications, the removed sidewall can be re-used in the foundation, such as by positioning it within and at the base of its respective cell before the cell is in-filled. For certain applications, both tyre sidewalls can be removed from at least some of the tyres, to produce a unit comprising essentially the tread of the tyre.

The tyre cells 16 can be stacked on site prior to being arranged over the material layer 12. Typically, the tyre cells 16 are stacked with their intact side wall facing up (i.e. such that each tyre cell does not collect rain, silt, dust, debris, etc). This can be particularly useful when constructing a foundation in a tropical location, where insects (e.g. mosquitoes) can breed in stagnant water.

When the material layer 12 is a geotextile typically it takes the form of a sheet format of a woven polymer fibre (e.g. of polypropylene or polyester fibre). For example, the geotextile can be manufactured from durable, high-modulus polypropylene yarns woven into a robust, dimensionally stable geotextile sheet. The geotextile material can be supplied in the form of a roll of long sheeting. A suitable type of geo-material for the foundation is so-called "80 kN woven geotextile". Such a geotextile is supplied in rolls of ~ 5.1 m widths. Alternatively, the material layer 12 can be a combination of a non-woven geotextile and a geo-grid that has a high tensile strength (e.g. a composite product of non- woven polypropylene geo-fabric and high-strength polyester (e.g. PET) fibres). Other geotextile materials can be employed. In a further alternative, the material layer 12 can comprise a waterproof membrane, such as may be employed in very wet applications. The waterproof membrane can comprise e.g. rolls of polymeric sheeting (e.g. of high density polyethylene, polypropylene, etc.). The waterproof membrane may instead comprise e.g. rolls of a tightly woven polymeric fibrous sheet material (e.g. a fibre treated so as to be hydrophilic).

The material layer 12 is rolled out along and over the optionally pre-prepared ground G. In the case where two or more rolls are required to cover a given width of foundation, the adjacent and generally parallel lengths of material can be overlapped. For example, as shown in Figure 4, two adjacent lengths 12a and 12b of overlapped material sheets, each having a width X of ~ 5.1 m, are laid out in parallel, but so as to overlap by a distance Y that is typically > lm. The two adjacent lengths typically have an overall width that is greater than the layer of tyre cells 12, so that the material layer 12 extends laterally beyond the tyre cell layer 14 on either side of the foundation. This allows the material layer 12 to be secured over the ground immediately adjacent to the foundation, which can also help to secure this ground (e.g. against erosion, etc.).

As also shown in Figure 4, typically the tyre cells 16 in the layer 14 are laid out over the material layer 12 in columns (C I, C2, C3, . . . C7). For example, for a ~ 7 metre wide sub-base foundation, seven columns of tyre cells are provided. The resultant seven columns C 1-C7 have an approximate overall width of 6.7 m.

As shown in Figure 4 (i.e. when viewed in plan), each column is also offset from immediately adjacent column(s) by half a tyre cell. This enables the tyres in the layer 14 to closely pack, thereby providing the layer 14 with a honeycomb pattern/structure.

Each tyre cell 16 closely faces or touches two adjacent tyre cells in its column. The tyre cells 16 in the "outermost" columns (C I & C7) closely face or touch two adjacent tyre cells in the immediately adjacent columns (C2 & C6). The tyre cells 16 in the "intermediate" columns (C2 to C6) closely face or touch two adjacent tyres in the immediately adjacent columns on either side thereof. Thus, edge tyre cells face or touch four adjacent tyre cells, whereas intermediate cells closely face or touch six adjacent cells. This close-packed arrangement also assists the foundation to more effectively attenuate and spread the load and absorb the forces transmitted through the foundation in use. In this regard, adj acent tyre cells can work together to share load and attenuate/absorb dynamic (including unevenly applied) forces and loads at the foundation arising from both moving and stationary vehicles, structures, etc. In certain applications, some or all of the adj acent tyre cells 16 in the layer 14 can be secured to each other. For example, securing of the tyre cells can be employed when the underlying ground is particularly soft or unstable, such as swamp or marsh land, mangroves, flood plains, sandy sub-soil, unstable clay or silt layers, etc. The adjacent tyre cells can be secured together using fasteners such as bolts, rivets, rods, etc. Alternatively, as will be described below, the adjacent tyres can be secured together using elongate tying elements such as rope, tendons, cable, etc. This securing together of the tyre cells can enhance lateral stability in the tyre cell layer 14 (i.e. by further resisting lateral displacement under load arising from

dynamically applied forces). In this regard, the secured-together tyre cells effectively functioning as a single composite engineered unit.

In use, and when compared to existing foundation constructions, the filled tyre cells 16 provide a high degree of load spreading for a comparatively low depth of foundation material. The tread of each tyre cell has a high degree of hoop strength, which enables each tyre cell to act as a cellular confinement for the fill material, thus facilitating the spread of the applied load over a larger base area. Further, the tensioned material layer 12 acts in conjunction with the filled tyre cells 16 to spread this load over a large area, whilst at the same time reducing lateral displacement of the filled tyre cells. This performance is regardless of whether adjacent tyre cells are secured to each other or not.

Referring now to Figures 5 and 6, two arrangements for a subsea cable/pipe protection mattress 50 (Fig. 5) and a sub-sea cable/pipe stability mattress 60 (Fig. 6) will be described, with each mattress 50, 60 being formed from tyres, in this case whole tyres 52 (although tyre cells 16 as described above could be used). Truck or car tyres can be used, or even so-called "super-single" tyres. The mattress dimensions can be altered to suit user requirements.

In the embodiment of Figure 5, the subsea cable/pipe protection mattress 50 is designed to sit over and protect a subsea cable Ca. The mattress 50 comprises multiple whole tyres 52 arranged in a grid (square) pattern. As shown in Fig. 5 A, the mattress 50 comprises five rows and twenty-four columns of tyres 52, with the subsea cable Ca lying under the central row of tyres in use.

Fig. 5A also shows that certain of the tyres 52a are in-filled with a cementitious material (e.g. concrete). These tyres 52a help to sink the mattress during placement over the cable Ca, and also act as an anchor in use. The number of concrete filled tyres can be varied depending on the application (e.g. subsea currents, tides, water flows, depth of use, etc.).

Figs. 5D and 5E show that each tyre 52 has a series of (i.e. four, e.g. 20 mm) holes 54 formed into each of the side walls, and a series of (i.e. four, e.g. 30mm) holes 56 formed into the treads, of each tyre. The holes 54 can be equi-spaced around the top edge of the tyre and the holes 56 can be equi-spaced around the centre line of the tyre perimeter for rope fixing. The holes 54 allow air to escape during casting of concrete into the tyres 52a, and when the mattress 50 is being sunk in a body of water, again to help sink the mattress during placement over the cable Ca. Also, after mattress placement, and when sand and silt, etc migrate inside the tyres 52, the holes 54 allow trapped water to escape. In use, sand and silt, etc can also migrate between the tyres, such that the mattress 50 can settle into the seabed.

In the embodiment of Figure 5, the mattress 50 is held together by one (or more) elongate securing elements in the form of elongate rope(s) 58. Each rope can comprise 20mm polypropylene rope fitted through the tyres in the pattern as shown. Rope joins can be spliced in the middle section of the mattress.

Other elongate fasteners can be used such as cables, tendons, rods, sheaths, tethers, etc. The ropes of 20mm woven polypropylene can provide rot, salt, sand, etc.

resistance. The rope(s) 58 is threaded through first and second tread locations in the form of holes 56 that are formed in the treads of tyres, typically at opposing tread sides thereof. The rope(s) 58 extend centrally along each of the rows and columns, and are bent/curved/looped around the end of each row/column to be fed back through the next adjacent row/column, and so on. As shown in Fig. 5C, the rope 58 also extends through the concrete filled tyres 52a, being cast into the concrete during on-shore formation of the mattress 50.

Fig. 5B shows that aluminium ferrules or knotted rope stoppers 59 can be applied to the rope 58 at various locations. These stoppers 58 act to prevent rope pull-through the tyres and also act to prevent tyre movement in the mattress in use. In the embodiment of Figure 5, these stoppers 59 can be fitted into the central three rows of tyres (i.e. where the concrete filled tyres 52a are not employed) and e.g. at each row end, as well as at every fourth tyre between the ends.

In the embodiment of Figure 6, the subsea cable/pipe stability mattress 60 is designed to sit over and anchor a subsea cable Ca at various locations along its length. The mattress 60 comprises multiple whole tyres 62 arranged in a grid (square) pattern. Figure 6 A shows a truck tyre mattress plan view (scale 1 :50). As shown in Fig. 6A, the mattress 60 comprises three rows (plain A, Norm 3132) and six columns of tyres 62 (plain B, Norm 6264), with the subsea cable Ca again lying under the central row of tyres in use. The number of tyres can be varied depending on the application (e.g. subsea currents, tides, water flows, etc). In contrast to the subsea cable/pipe protection mattress 50 of Figure 5, in the mattress 60 of Figure 6, and as best shown in Fig. 6C, each of the tyres 62 is infilled with a cementitious material 64 (e.g. concrete). Figure 6C shows a truck tyre detail section view at a scale of 1 : 10 with concrete cast into the tyre section. These in-filled tyres provide considerable weight to the mattress and thereby enable the entire mattress 60 to act as an anchor for a subsea cable/pipe in use. The in-filled tyres also eliminate the need for rope stoppers 59, as in mattress 50.

As shown in Fig. 6A, the mattress 60 comprises three tyre rows of approximate width A of 3.132 m and six tyre columns of approximate width B of 6.264 m. Again, the mattress 60 is held together by multiple elongate row ropes 66 and column ropes 68. Other elongate fasteners can be used such as cables, tendons, rods, sheaths, etc. The ropes can e.g. be of up to 24mm woven polypropylene to provide rot, salt, sand, etc resistance. However, the ropes 66, 68 are threaded through first and second tread locations in the form of hole pairs formed in the treads of each tyre, with the pairs located at opposite sides of each tyre. This defines a rope loop for each row or each column, with each rope loop extending generally centrally along its row or column (i.e. each rope loop is bent/curved/looped around the end of its row or column to be fed back through the same row/column).

The rope detail for a truck tyre mattress is shown in a part sectional plan view in Fig. 6B (scale 1 :25). As shown in Figure 6B the rope loops 66, 68 each extend through the concrete of each of the filled tyres 62, the ropes being cast into the concrete during on-shore formation of the mattress 60. The polypropylene rope is cast into concrete. The rope loops 66, 68 provide a more secure and robust form of connection between adjacent tyres 62 in use. Again, in use, sand and silt, etc. are able to migrate between the tyres, such that the mattress 60 can settle into the seabed.

It should be noted that the mattresses 50 & 60 are not limited to subsea cable- covering applications, but can be used for other subsea or above ground

stabilisation purposes. Variations and modifications may be made to the embodiments previously described without departing from the spirit or ambit of the disclosure.

In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments.