AU2014202480B2 - Sea defence - Google Patents

Abstract

H:\tw\Interwoven\NRPortbl\DCC\TW\630869 11.doc-24/10/2011 - 16 A sea defence apparatus including a plurality of precast interlocking blocks arranged in a stepped configuration, a duct contiguous through blocks on adjacent steps and a tensioning member extending through the duct to thereby interconnect the blocks. Fig. 1A - . ... ' .. . . . .. . . .

Description

Background of the Invention [0001] The present invention relates to a sea defence construction method and apparatus.

Description of the Prior Art [0002] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

[0003] It is known to provide sea defences, typically in the form of walls or other retaining structures, in order to prevent erosion of coastal areas. Whilst such sea defences may be of a variety of forms, these are typically constructed by forming concrete structures in situ. This process typically involves the construction of formwork which is then filled with concrete and allowed to set before the formwork is removed. It will be appreciated that reinforced concrete or the like can be used for additional strength. However, the use of sea defences in this manner is a time-consuming and expensive process and typically requires significant skilled labour in order to ensure integrity of the structure. Accordingly, it is desirable to provide an improved sea defence structure.

Summary of the Present Invention [0004] In a first broad form the present invention seeks to provide a sea defence apparatus including:

a) a plurality of precast interlocking blocks arranged in a stepped configuration, wherein the blocks are arranged in rows to define a number of steps, and each block including a concave comer edge that interlocks with an edge of a block on an adjacent step, so that each row is offset from an adjacent row;

b) a duct contiguous through blocks on adjacent steps; and,

c) a tensioning member extending through the duct to thereby interconnect the blocks.

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-2[0005] Typically a slope angle for the stepped configuration is at least one of between 20° and 60° and about 30°.

[0006] Typically epoxy is provided between adjacent interlocking blocks.

[0007] Typically each step includes a number of longitudinal blocks arranged end to end and wherein blocks in at least one step include a longitudinal duct contiguous along a length of the blocks and wherein the apparatus includes a longitudinal tensioning member extending through the longitudinal duct to thereby interconnect the blocks in the at least one step.

[0008] Typically the blocks in adjacent steps are offset.

[0009] Typically the blocks are concrete blocks.

[0010] Typically exposed surfaces of the blocks are coated with at least one of water repellent coating and Silane Siloxane.

[0011] Typically the tensioning member is made of stainless steel.

[0012] Typically the tensioning member is a threaded bar secured using threaded nuts and wherein the nuts, engage a shoulder defined by a cut-out in an outer edge of blocks on outer steps.

[0013] Typically the apparatus includes a number of supporting members at least partially embedded in ground for supporting at least some of the blocks.

[0014] Typically the apparatus includes barrier provided on a leading edge of the apparatus, the barrier extending into the ground.

[0015] Typically the apparatus includes a drain for drainage of fluid therethrough.

[0016] In a second broad form the present invention seeks to provide a method of constructing a sea defence, the method including:

a) positioning a plurality of precast interlocking blocks in a stepped configuration so that a duct in the blocks is contiguous through blocks on adjacent steps, wherein the blocks are arranged in rows to define a number of steps, and each block

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-3 including a concave corner edge that interlocks with an edge of a block on an adjacent step, so that each row is offset from an adjacent row; and;

b) providing a tensioning member extending through the duct to thereby interconnect the blocks.

[0017] Typically the method includes providing epoxy between an concave corner edge of each block and an edge of a block on an adjacent step.

[0018] Typically the method includes coating exposed surfaces with a water repellent coating.

[0019] Typically the method includes inserting a threaded bar through the duct and securing the threaded bar using threaded nuts.

[0020] Typically the method includes:

a) embedding a number of supporting members in ground; and,

b) positioning at least some of the blocks on the supporting members.

[0021] Typically the method includes pre-forming the ground in a stepped configuration to receive the blocks.

[0022] Typically the method includes providing a barrier on a leading edge of the apparatus, the barrier extending into the ground.

[0023] Typically the apparatus includes providing a drain extending through the apparatus to allow for drainage of fluid therethrough.

Brief Description of the Drawings [0024] An example of the present invention will now be described with reference to the accompanying drawings, in which: [0025] Figure 1A is a schematic side view of a first example of a sea defence apparatus;

[0026] Figure IB is a schematic side view of one of the blocks of Figure 1A;

[0027] Figure 2A is a schematic side view of a second example of a sea defence apparatus;

[0028] Figure 2B is a schematic plan view of the sea defence apparatus of Figure 2A;

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-4[0029] Figure 2C is a schematic front view of the sea defence apparatus of Figure 2A;

[0030] Figures 2D to 2G are schematic side views of examples of the blocks used in the sea defence apparatus of Figure 2 A;

[0031] Figure 3 A is a schematic side view of a third example of a sea defence apparatus; and, [0032] Figures 3B to 3D are schematic side views of examples of the blocks used in the sea defence apparatus of Figure 3 A.

Detailed Description of the Preferred Embodiments [0033] An example of a sea defence apparatus will now be described with reference to Figures 1A and IB.

[0034] In this example, the sea defence apparatus 100 includes a plurality of precast interlocking blocks 110 arranged in a stepped configuration. A duct 120 is provided which is contiguous through blocks 110 on adjacent steps, with a tensioning member 130 extending through the duct 120 to thereby interconnect the blocks.

[0035] The blocks 110 may be positioned directly on suitably prepared ground, such as packed sand or earth. Alternatively, a number of supporting members 140 may be provided, at least partially embedded in ground G, for supporting at least some of the blocks, however supporting members are not essential, and this may depend on site requirements.

[0036] Accordingly, the above-described apparatus provides a sea defence apparatus 100 which can be provided on sloped ground, such as a beach foreshore, or the like. The sea defence apparatus 100 is performed from a plurality of precast blocks 110, which are suitably shaped so as to interlock in a stepped configuration and which are held together using a tensioning member 130, so that blocks 110 on adjacent steps are urged towards each other, thereby forming an effectively unitary body. The unitary body is supported by the ground surface and/or support members 140 such as piles.

[0037] This configuration provides an extremely robust structure that is capable of preventing ground erosion caused by wave action or the like by absorbing and dissipating any wave energy, as well as providing a barrier to prevent inundation of coastal regions.

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-5 [0038] Additionally, the sea defence apparatus is easy to install. For example, support members can be easily provided using standard piling techniques if required, with blocks then being laid on the piles and/or ground, with this being carried out progressively up the slope in a step-wise fashion. As the blocks are precast minimal effort is required on site and positioning of the blocks can be achieved relatively simply using a lifting apparatus such as a crane, winch, jacking arrangement, or the like.

[0039] Positioning can be further facilitated by the interlocking nature of the blocks. In one example, interlocking is achieved using a concave inverted comer edge 111 that acts as a rebate to mate with the edge of a block on an adjacent step. This helps ensure respective ducts 121 in each block 110 align to provide the contiguous duct 120, which in turn allows a tensioning member 130 to be inserted therein and post-tensioned once the blocks are in situ. It will be appreciated however that interlocking can be achieved using any suitable mechanism, such as through the use of another type of interlocking joint, through the use of coupling brackets, or by appropriate preparation of the ground and use of the tensioning member. Use of a rebate style joint is not therefore essential, but does provide an easy mechanism for aligning and interconnecting the blocks.

[0040] It will therefore be appreciated that this provides a mechanism for a sea defence to be constructed in a manner that is cheaper, more rapid and easier than is achievable using formwork construction techniques.

[0041] Furthermore, the stepped configuration can be used to provide seating or the like for individuals at the coast, meaning the provided sea defences do not preclude use of the area on which it is provided for recreation purposes.

[0042] Furthermore, the apparatus can be applied in most situations and includes characteristics of strong design, economical to manufacture and install, low maintenance, long life span, rapid constructability allowing for emergency repairs and installation, fast assembly of wall, easy to construct, minimum plant needed, easy to extend wall heights at later times, 100% recycled for re-use, pleasing to the eye and usable by the public. The system can be adopted as a standard, to make future construction and repairs economical with stock in hand for emergencies.

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-6[0043] A number of further features will now be described.

[0044] The blocks can be precast from any suitable material, but are typically made of concrete, and optionally, reinforced concrete. In the event that the blocks are made of reinforced concrete, the reinforcement can either be grade 316 stainless steel, or grade N500 ‘ normal steel’ with a 70mm cover. Helicafeinforcement may also be provided around the ducts to resist bursting forces induced by the stress bars during tensioning. In accordance with typical applicable standards, 16 mm diameter bars are usually the minimum size Ngrade steel reinforcement used to improve durability. Use of concrete allows the wall to be easily recycled should the need arise.

[0045] The blocks can be created in any suitable size, depending on the preferred application, and are generally designed to achieve sufficient structural capacity under “typical” seawall loadings, which it will be appreciated may vary depending on the location of installation. In one example, the precast block elements can have standard lengths, such as 1500 mm, 3000 mm and 6000mm, or the like, although any suitable dimensions can be used. A typical step size of 300mm (riser) by 600mm (tread) can be used, although this may depend on the slope of the ground, or required inundation prevention, and can therefore be varied to suit specific conditions, for example by adjusting the dimensions of the concave comer edge 111.

[0046] Exposed surfaces of the blocks can be coated with a water-repellent coating such as Silane Siloxane, or the like. Furthermore, during construction, epoxy can be provided between adjacent interlocking blocks 110 to ensure sealing between the blocks 110 to prevent water ingress. Additionally, the use of epoxy can absorb compressive forces as blocks are post-tensioned during construction, thereby helping to prevent damage to the blocks 110.

[0047] Each step typically includes a row or course including a number of longitudinal blocks arranged end to end and these may also include tensioning members extending longitudinally along two or more of the blocks to provide further support. Blocks on adjacent steps or courses can be provided in an offset configuration, as will be described in more detail below, to further increase the strength of the constructed arrangement. It will be appreciated that different arrangements of blocks can be used for example in a stretcher bond,

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-7raking stretcher bond, straight diagonal bond or the like, depending on the particular requirements of the site.

[0048] For example, straight joints, where blocks on adjacent courses are aligned, can be used to allow for some settlement of the apparatus. In this instance, each group of stepped blocks 110 forms an effectively independent panel, in abutment with one or more adjacent panels, allowing each panel to settle independently. Each butt joint between blocks on a course would typically include a hinge formed by a basic male/female joggle, which in one example measures 200 x 200 x 30 mm deep. A packer of 2 mm can be placed in the joint to eventually give a 2 mm gap in the joint, thereby allowing for relative settling, whilst providing some physical coupling between adjacent blocks on a course. In one example, the use of a longitudinal tensioning member is only required in the event that blocks are aligned in adjacent courses to provide additional structural integrity.

[0049] The tensioning member and longitudinal tensioning members may be of any suitable form but is typically made of stainless steel, to provide corrosion resistance. In one example stainless steel grade 316 is used, but it will be appreciated that other suitable materials could be used. The tensioning member may be a thread bar using nuts, which engage the blocks 110. In one particular example, a Macalloy™ 650 stainless fully threaded bar system can be used as this is available in grade 316 stainless steel, but it will be appreciated that other arrangements could be used, such as use of a tensioning cable or the like.

[0050] The tensioning member can extend between upper and lower blocks in the steps, which act as anchors, so that the tensioning member 130 extends through blocks 110 on all the courses. However, this is not essential and instead the tensioning member 130 may only extend through blocks 110 on some of the courses.

[0051] The tensioning member is provided in the contiguous duct, with multiple ducts typically being provided 750 mm from the ends of the blocks 110, with an intermediate spacing of 1500 mm, thereby ensuring forces applied by the tensioning member can be accommodated. Tensioning is typically achieved using tensioning nuts that engage threads on the tensioning member and abut against a shoulder on the block. In one example, a long nut can be used, allowing tensioning members to be coupled together. This can be used to

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-8allow additional steps to be added and coupled to existing steps, allowing for the sea defence apparatus to be built progressively, for example to accommodate changes in sea levels or the like. Typically, once the tensioning member is installed, the ducts are grouted and optionally capped, thereby helping to prevent ingress of water. It will be appreciated that a similar arrangement is typically used for the longitudinal tensioning member and this will not therefore be described in further detail.

[0052] The supporting members operate to provide foundations for the apparatus, and the particular configuration used can vary depending on geotechnical conditions and topography of the site. Foundation design is to be sufficient to prevent damage caused by differential settlement of the blocks. This is especially important with segmental prestressed block construction, as eccentricity of the pre-stress forces can be induced by differential settlement, resulting in unbalanced bending forces in the structure. Design of the supporting members therefore typically utilizes a pile and headstock configuration, providing a rigid foundation for the superstructure. In one specific example, Continuous Flight Auger (CFA) Piles can be used to provide structural resistance against compressive and lateral loads on the seawall. CFA Piles should be installed such that they are embedded into a clay layer where possible. However, piles may not be required and largely this will depend on the nature of the ground on which the sea defence apparatus is constructed.

[0053] A barrier may be provided at a leading edge of the apparatus with the barrier extending into the ground. The barrier may be a vinyl sheet pile or the like which is intended to prevent wash out of material beneath the apparatus, which in turn could compromise the strength and structural integrity of the apparatus. Vinyl sheetpiles are easy to install and achieve reasonable durability in the marine environment and can be provided under the top of the seawall to provide protection where overtopping scour is expected.

[0054] In a further example, a drain might be provided through the apparatus to relieve hydrostatic pressure behind the apparatus. This drainage is typically configured to prevent wash out of material from behind the apparatus. In one example the drainage includes a granular fill and geotextile installed behind the apparatus with 40 mm weep hole ducts through the blocks 110 where required. Drainage ducts may only to be included in 3000 mm and 6000 mm blocks, and in general would be arranged to not interfere with stressing ducts.

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-9[0055] A second specific example will now be described in more detail with reference to Figures 2A to 2G.

[0056] In this example, the apparatus 200 again includes a number of blocks 210 generally arranged in a stepped configuration, with a contiguous duct 220 containing a tensioning member 230. It will be noted that in this example, the stepped configuration is steeper than in the previous example, which can be used for example to provide greater coastal protection. Any angle of slope for the stepped configuration can be used, but in one example, this is between 20° and 60° and more typically about 30°.

[0057] As shown in this example, each block includes four ducts 220 extending therethrough. Additionally, as shown in Figure 2B, blocks 210 on adjacent steps are offset, so that each block 210 is coupled to two different blocks 210 on an adjacent step, using respective tensioning members and ducts 230, 220, thereby improving structural integrity of the apparatus 200.

[0058] Again, supporting members in the forms of piles 240 are driven into the ground to provide a foundation for the apparatus 200. In this example, a vinyl sheet 250 extends from a lowest step in front of the foremost pile 240.1 into the ground G. The vinyl sheet pile prevents water erosion occurring under the sea defence apparatus, and is typically sandwiched between the lowermost block 220 and supporting member 240, as shown.

[0059] In this example, four different types of block are used, as shown generally at 210.1, 210.2, 210.3, 210.4 in Figure 2A, and each of which is shown in Figures 2D to 2G, respectively.

[0060] In particular, the blocks 210.1 shown in Figure 2D include a duct portion 221 extending therethrough, to provide part of the contiguous duct 220. The block 210.1 includes a concave comer edge 211 acting as a rebate, and which in this example includes an angled comer 212, having a complimentary shape to an angled cut out 213 provided on the opposing longitudinal edge of the block on an adjacent block 210, thereby allowing blocks on adjacent steps to interlock. The second type of block 210.2 shown in Figure 2E further includes a longitudinal duct 222 extending through a length of the block 210.2, allowing a longitudinal tensioning member (not shown) to be inserted therethrough to place blocks 210.2 along a step

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- 10under compression in a longitudinal direction, thereby providing additional structural support.

[0061] The block 210.3 shown Figure 2F acts as a tensioning member anchor block for a lower end of the tensioning member, and is typically used as a lowest step, includes a cut-out in a lower corner of the block 210 that defines a shoulder 213.1 for receiving a tensioning nut 231 that is used in maintaining tension in the tensioning member 230. Similarly, the block

210.4 shown in Figure 2G acts as a tensioning member anchor block for an upper end of the tensioning member, and is typically used as an upper step block. The block 210.4 includes a concave comer edge 211 defining a shoulder for receiving the tensioning nut 232 at an upper end of the tensioning member 230.

[0062] It will be appreciated that whilst the different blocks can have different physical forms, this is not essential, and more typically each of the blocks will be substantially identical and that the difference is in function rather than physical configuration.

[0063] A second specific example will now be described in more detail with reference to Figures 3A to 3D.

[0064] In this example, the apparatus 300 again includes a number of blocks 310 generally arranged in a stepped configuration, with a contiguous duct 320 containing a tensioning member 330. In this example, supporting members are not required, and the apparatus 300 is constructed by providing the blocks 310 directly on prepared ground. A vinyl sheet 350 extends from a second lowest step into the ground G to prevent water erosion occurring under the sea defence apparatus. A drain 360 extends through the block 310 on the second lowest step, thereby allowing water to drain through the blocks 310 and bypass the vinyl sheet 350, allowing for drainage from behind the apparatus.

[0065] In this example, three different types of block are used, as shown in Figures 3B to 3D, respectively. In particular, the blocks 310.1 shown in Figure 3B include a duct portion 321 extending therethrough, to provide part of the contiguous duct 320. The block 320.1 includes a concave corner edge 311 acting as a rebate, and which in this example includes a recess

312, whilst the opposing longitudinal edge of the block 310.1 includes a concave comer edge

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- 11 313 acting as an angled rebate for engaging an adjacent block 310, thereby allowing blocks on adjacent steps to interlock.

[0066] The block 310.2 shown in Figure 3C acts as a tensioning member anchor block for an upper end of the tensioning member, and is typically used as an upper step block. In this example, the recess 312 receives the tensioning nut 332 at an upper end of the tensioning member 330. The block 310.3 shown Figure 3D acts as a tensioning member anchor block for a lower end of the tensioning member, and is typically used as a lowest step. In this example, the rebate 313 receives a tensioning nut 331 that is used in maintaining tension in the tensioning member 330. Each of the blocks 310.1., 310.2, 310.2 have a generally similar profile, with the difference being in the manner of operation rather than construction, thereby further simplifying the manufacture of the pre-cast blocks.

[0067] An example of the installation process for the arrangement of Figures 3A to 3D will now be described in more detail. In this example, the installation process uses the following steps:

1. Construct a sand/bidum/rock bund to ensure the construction works are protected;

2. Level and compact sand for the first (lowest) row of steps;

3. Precast steps delivered to site in 3000 mm and 6000 mm lengths;

4. Lay first row of steps;

5. Install vinyl sheet piles behind first row;

6. Compact and level sand with water and reversible plate vibrator for the second row of steps;

7. Lay the second row of steps in stretcher bond and bolt the second row to the first row with the stainless steel tensioning members and long retaining nuts. As part of this process, the lifting holes at the back of the step are covered with a layer of spunbond needle-punched continuous filament polyester geotextile, such as Bidum A49™, so that the lifting hole functions as a drainage duct;

8. Extend the stainless steel tensioning members to a third row of steps; and,

9. Follow steps 6,7 & 8 until the apparatus is completed.

[0068] Other tasks that typically need to be performed during this process include squaring off 6000 mm panels with 3000 mm panels to provide straight edges. Butt joints may be

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- 12provided between panels to induce flexibility to allow relative settling of panels and a special panel can be used at corners of the apparatus that can be mitred to provide a strong and flush finish.

[0069] During construction, the rock available from a previous wall that has been demolished can be buried between -1.0 and -1.50 AHD to form additional protection to the toe of the vinyl wall. A vinyl sheet pile can also be installed behind the top step to mitigate scour from overtopping wave action, whilst a transition at the culvert outlet to be treated by spraycrete and stainless steel mesh to ensure integrity of the structure.

[0070] It will be appreciated from the above that a wide range of block configurations could be used and that the specific examples shown are for the purpose of illustration only.

[0071] Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.

[0072] Persons skilled in the art will appreciate that numerous variations and modifications will become apparent. All such variations and modifications which become apparent to persons skilled in the art, should be considered to fall within the spirit and scope that the invention broadly appearing before described.

[0073] For example, whilst the above described apparatus has been described for use in sea defences, it could also be applied to other circumstances. Additionally, whilst a stepped could be used, this is not essential and sloped or horizontal arrangements could be provided.

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Claims (7)

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1) A sea defence apparatus including:

a) a plurality of precast interlocking blocks arranged in a stepped configuration, wherein the blocks are arranged in rows to define a number steps, and each block including a concave corner edge that interlocks with an edge of a block on an adjacent step, so that each row is offset from an adjacent row;

b) a duct contiguous through blocks on adjacent steps; and,

c) a tensioning member extending through the duct to thereby interconnect the blocks.

2) Apparatus according to claim 1, wherein a slope angle for the stepped configuration is at least one of:

a) between 20° and 60°; and,

b) about 30°.

3/7

Fig. 2B

3) Apparatus according to claim 1 or claim 2, wherein epoxy is provided between adjacent interlocking blocks.

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4) Apparatus according to any one of the claims 1 to 3, wherein each step includes a number of longitudinal blocks arranged end to end and wherein blocks in at least one step include a longitudinal duct contiguous along a length of the blocks and wherein the apparatus includes a longitudinal tensioning member extending through the longitudinal duct to thereby interconnect the blocks in the at least one step.

5/7

Fig. 2G

Fig. 2F

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5) Apparatus according to any one of the claims 1 to 5, wherein the blocks in adjacent steps are offset.

6/7

6) Apparatus according to any one of the claims 1 to 5, wherein the blocks are concrete blocks.

7) Apparatus according to any one of the claims 1 to 6, wherein exposed surfaces of the blocks are coated with at least one of:

a) water repellent coating; and,

b) Silane Siloxane.

8) Apparatus according to any one of the claims 1 to 9, wherein the tensioning member is made of stainless steel.

9) Apparatus according to any one of the claims 1 to 10, wherein the tensioning member is a threaded bar secured using threaded nuts and wherein the nuts, engage a shoulder defined by a cut-out in an outer edge of blocks on outer steps.

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- 1410) Apparatus according to any one of the claims 1 to 9, wherein the apparatus includes a number of supporting members at least partially embedded in ground for supporting at least some of the blocks.

11) Apparatus according to any one of the claims 1 to 10, wherein the apparatus includes barrier provided on a leading edge of the apparatus, the barrier extending into the ground.

12) Apparatus according to any one of the claims 1 to 11, wherein the apparatus includes a drain for drainage of fluid therethrough.

13) A method of constructing a sea defence, the method including:

a) positioning a plurality of precast interlocking blocks in a stepped configuration so that a duct in the blocks is contiguous through blocks on adjacent steps, wherein the blocks are arranged in rows to define a number steps, and each block including a concave corner edge that interlocks with an edge of a block on an adjacent step, so that each row is offset from an adjacent row; and,

b) providing a tensioning member extending through the duct to thereby interconnect the blocks.

14) A method according to claim 13, wherein the method includes providing epoxy between an concave corner edge of each block and an edge of a block on an adjacent step.

15) Apparatus according to claim 13 or claim 14, wherein the method includes coating exposed surfaces with a water repellent coating.

16) Apparatus according to any one of the claims 13 to 15, wherein the method includes inserting a threaded bar through the duct and securing the threaded bar using threaded nuts.

17) Apparatus according to any one of the claims 13 to 16, wherein the method includes:

a) embedding a number of supporting members in ground; and,

b) positioning at least some of the blocks on the supporting members.

18) Apparatus according to any one of the claims 13 to 17, wherein the method includes preforming the ground in a stepped configuration to receive the blocks.

19) Apparatus according to any one of the claims 13 to 18, wherein the method includes providing a barrier on a leading edge of the apparatus, the barrier extending into the ground.

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20) Apparatus according to any one of the claims 13 to 19, wherein the apparatus includes providing a drain extending through the apparatus to allow for drainage of fluid therethrough.

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Fig. 2A

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7/7

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Fig. 3B Fig. 3C