GB2469646A

GB2469646A - A geotechnical structure including particulate material and vertical panels

Info

Publication number: GB2469646A
Application number: GB0906819A
Authority: GB
Inventors: Heindrik Adriaan Jas
Original assignee: Tensar Technologies Ltd
Current assignee: Tensar Technologies Ltd
Priority date: 2009-04-21
Filing date: 2009-04-21
Publication date: 2010-10-27
Also published as: GB0906819D0

Abstract

A method of constructing, optionally in a body of water (2), a reinforced geotechnical structure which includes particulate material (8). A wall is erected with a plurality of vertically extending panels (6) supported by the ground (4) which may be a underwater, at least some of the panels (6) having reinforcing elements (9) which extend transversely away from the panels (6) within a volume in which the structure is to be erected, and depositing particulate material (8) into the volume. The reinforcing elements (9) are preferably plastics geogrids. The reinforcing elements may be introduced under water in a folded or otherwise compacted configuration on which an underwater manipulation is effected to bring the elements (9) into the reinforcing configuration. Also disclosed is a panel (6) suitable for use in constructing a retaining wall of a reengineering structure in a body of water, the panel having lower support formation (7) for engagement with the bottom of the body of water and the panel having a length of a reinforcement element for forming reinforcement in a compacted particulate material.

Description

Geoenqineerinc Structures The present invention relates to a method of constructing in a body of water a geoengineering structure comprised of particulate material incorporating mesh structures such as geogrids as the reinforcement. The body of water in which the structure is constructed may for example be the sea (particularly at a coastal location) or an inland body of water such as a lake or an inland waterway, e.g. river or canal. The invention has application, for example, to the construction of sea walls and also quays, particularly for light commercial vessels.

The type of structure with which the invention is concerned is known in the art as a "reinforced soil structure". In this context the "soil" is a "particulate material", which term is used to include rocks, stones, gravel, sand, earth, clay, aggregate, aggregate held together by a binder such as asphalt or cement, concrete, or any other particulate material used in geotechnical engineering or building. Recycled materials may be used as the "particulate material". The terms "soil", and "particulate material" as used herein are synonymous.

Reinforced soil structures are extensively used in land-based civil engineering constructions. Briefly, such reinforced soil structures comprise compacted soil incorporating reinforcing mesh structures such as geogrids and they may be used for example to allow the erection of a retaining wall or bridge abutment. For example, in the construction of an embankment with a retaining wall, one or more courses of blocks forming the wall may additionally be laid and soil (e.g. aggregate material) introduced behind the blocks to form a lower stratum of the embankment up to the upper level of the blocks. The soil may then be compacted. Subsequently a mesh . S. : structure is laid horizontally on the compacted soil with one of its edges connected to the uppermost blocks. The above sequence (i.e. laying courses of blocks, filling with soil, compacting the soil and laying of a mesh structure) Is repeated as many times *:*. as required until the structure is completed. The geogrids may be of plastics material and comprise transversely spaced, longitudinally extending, oriented strands. (In this context "oriented" means "molecularly oriented"). Such geogrids may be formed by uniaxially or biaxially orienting a plastics sheet starting material which has been provided with holes which form meshes in the final product. In a uniaxial geogrid of this type, there are longitudinally extending, molecularly oriented strands and transverse bars which are either substantially unoriented or have some degree of orientation. In biaxial grids of this type the longitudinally extending, oriented strands are connected by transverse, oriented strands. Examples of other types of geogrids that may be used are those produced, for instance, by stitch bonding fabrics made of polyester filaments and applying a flexible coating such as a PVC coating, or by weaving or by knitting, or even by spot-welding oriented plastics strands together.

Although attempts have been made to use a procedure as outlined above for constructions in bodies of water, they have never succeeded primarily because of the difficulties and expense creating a foundation for the wall under waler and also installing the mesh structure under water. These difficulties can be overcome by lowering the level of the water temporarily but this complicates the construction procedure and adds expense.

Construction work in bodies of water therefore frequently involves the use of sheet piling. Briefly, the piles are steel sheets which are driven into the bed at The bottom of the water body using a piling rig, a vibrator or hydraulic ram. The piles are connected to each other with co-operating slot arrangements provided along the longitudinal edges of the piles. Whilst steel piling is a relatively cheap technique it does suffer from a number of disadvantages. In particular, the piles must be driven deep into the ground (e.g. 5-6m) so as to achieve the required degree of support and even then it may be necessary for them to be further restrained by means of a steel tie or so-called dead man's" anchor in material that is infilled behind the piles for forming the structure. Additionally, steel piles cannot easily be used in combination with reinforced soil so other construction techniques must be employed. A further disadvantage of steel piles is corrosion of the steel, especially if the piles are used in aggressive environments such as a maritime environment where salt from the sea accelerates corrosion.

It is therefore an object of the present invention to obviate or mitigate the * : aforementioned disadvantages.

According to a first aspect of the present invention there is provided a method of constructing in a body of water a reinforced geotechnical structure comprised of particulate material, the method comprising the steps of: (a) erecting in the body of water a wall comprised of a plurality of vertically extending panels supported by the bed at the bottom of the water, at least some of the panels having attached thereto reinforcing elements that are in a reinforcing configuration In which they extend transversely away from the panels within the volume of water in which the structure is to be erected, and (b) depositing particulate material into said volume to displace the water and form a structure comprised of the particulate material reinforced by said reinforcing elements.

According to a second aspect of the present invention there is provided a panel for use in constructing a retaining wall of a geoengineering structure in a body of water, the panel having a lower support fomiation for engagement with the bottom of the body of water to support the panel upright in the water, and said panel being provided with a length of a reinforcing element for forming reinforcement in compacted particulate material.

The Invention provides a convenient method for constructing a reinforced geotechnical structure in free standing water, such as the sea, a lake, river or canal.

A particular advantage of the invention lies in the fact that the panels used for erecting a retaining wail for the structure have reinforcing elements attached thereto which are used for reinforcing particulate material that is deposited into the water.

With this arrangement, the need to drive panels deeper into the soil layers such as is required in the case of sheet piling to achieve a secure foundation is avoided.

Rather, in constructing structures in accordance with the invention, the panels need only be positioned such that they remain upright (and remain horizontally and vertically aligned with any adjacent panels) whilst the particulate material is being deposited since once step (b) has been completed, there is a more than adequate restraining force on the panels (as a result of the reinforcing elements embedded in the particulate material) to retain them in position.

S.....

In a particularly convenient implementation of the method according to the invention, the reinforcing elements are pre-affbed to the panels before the latter are erected in the water. Alternatively or additionally, the reinforcing elements are flexible and are subjected to an underwater manipulation operation to bring them into their reinforcing configuration in which ideally there is little or no "slack" in the reinforcing elements. Ideally these elements are in a taut condition. The use of flexible reinforcing elements gives rise to the possibility of the elements being introduced under water (e.g. pre-affixed to the panels) in a folded, rolled or other compacted configuration on which an underwater manipulation is effected to bring the elements in to their reinforcing configuration.

When in their reinforcing configuration, the reinforcing elements are preferably in the form of loops which may be formed by ends of lengths of the reinforcing elements being attached to the panels. Ideally the opening defined by the confines of the loop is substantially vertical. Depending on the depth of the water and the vertical height of the loop, a panel may be attached to a single loop or two or more loops (e.g. 4 or 5) which are positioned one above the other. The exact configuration of the "loop" is not critical. Thus, for example, the loop as seen in plan view may provide three sides of a rectangle with the fourth side being provided by the panel. Alternatively, and again in plan view, the loop may provide two sides of a triangle (the third side being provided by the panel) or may be arcuate. Particulate material may be deposited from above initially within the confines the loop so that the interaction between the loops and the particulate material provides for stability of the panels in the water. Subsequently the aggregate may be introduced around and, if appropriate, above the level of the loops to build up the particulate structure to the desired height.

In a particularly preferred embodiment of the invention, the reinforcing elements are flexible and are provided in lengths attached to the panels at two locations across the width of the panel spaced by a distance less than the length of the reinforcing element attached between these locations. The reinforcing elements may then be subjected to an underwater manipulation operation to bring the reinforcing elements into their reinforcing configuration as a loop. Such manipulation may be effected by a removable configuring device which is positioned within the bounds of the length of the reinforcing element and then moved away from the panel to bring the element into its reinforcing configuration. The configuring device may be in the form of a frame, e.g. one having a number (e.g. four) of depending legs. The frame may be progressively lifted as particulate material is introduced into the loop as defined by the reinforcing element.

In preferred embodiments of the method, the panels have a lower ground-penetrating structure whereby the panel may be driven into the bed of the water body by a distance sufficient to ensure that the panel remains upright (and horizontally and vertically aligned with any adjacent panels) during the construction process. It is a significant feature of the invention that there is no need for the panel (or more specifically its ground penetrating structure) to be driven into the ground to the extent required in conventional sheet piling. Rather, the ground penetrating structure need only be driven into the waterbed so that, as indicated, the panel is able to remain upright (and horizontally and vertically aligned with any adjacent panels) during the construction process. Once the particulate material has been deposited, the interaction thereof with the reinforcing elements provides a horizontal restraining force on the panel so as to form a stable geoengineering structure. Typically, the ground penetrating structure will be driven into the bed of the water body by a distance of 0.5 -2m. . The ground penetrating structure may, for example, be of a metal (e.g. steel) formation at the base of the panel. Thus, for example, the ground penetrating formation may be a flat metal (e.g. steel) plate but other configurations are possible. For example, the metal fomiation may have corrugations that extend in parallel to the direction in which the panel is driven into the bed of the water body, e.g. corrugations of similar configuration to those employed for sheet piles.

Alternatively the panel may have downwardly converging ribs or the like to assist in penetration into the ground. Although ground penetration of the panels is preferred, we do not preclude the possibility of the panels being mounted on appropriate base structures which sit on the bottom of the water bed. * S **SS

The main body of the panel may for example be constructed of plastics, wood, concrete or other non-corroding materials as appropriate, although we do not preclude the use of steel for applications where the corrosion characteristics thereof *. may be tolerated.

*..: The reinforcing elements may be mesh structures and may for example be plastics geogrids, particularly such geogrids comprised of transversely spaced, longitudinally extending, (molecularly) oriented strands. Most preferably the geogrids are uniaxially oriented but we do not preclude the use of geogrids that are biaxially oriented. Suitable geogrids are, for example, those disclosed in GB2073090, GB2035191, GB2256164, GB2295353 and GB2391832 although other types of geogrids may be used. It should also be appreciated that other forms of reinforcing element known in the art of producing reinforced soil structures may be used, e.g. steel strips when in the form of loops.

The particulate material used for the method of the invention may, for example, be that used in conventional reinforced soil structures, e.g. rocks, stones, gravel, sand, earth, clay, aggregate, aggregate held together by a binder such as asphalt or cement, concrete, or any other particulate or cohesive material used in geotechnical engineering or building.

The particulate material should be compacted (e.g. by vibration) as it is deposited in the water. Conveniently the particulate material is deposited by means of a vibrating funnel which serves not only to provide for relatively accurate deposition of the particulate material but also simultaneously compaction thereof.

Alternatively compaction may be effected by means of a conventional vibrating lance.

The method of the invention is particularly applicable to the construction of reinforcing geotechnical structures in an enclosed volume of water, i.e. one in which the volume of water in which the structure is to be formed is bounded on all sides.

The method of the invention is particularly suitable for the construction of a reinforced geotechnical structure at a shore or bank location of a water body such as the sea, a river or lake. Thus, for example, the method may be used for constructing a quayside wall or erosion protection waterfront. In such constructions, the "land" may provide one boundary for an enclosed volume of water in which the structure is to be erected. We do not however preclude the possibility of employing the method of the invention which, in its finished form is wholly surrounded by water.

The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Fig 1 schematically illustrates a coastal location at which a reinforced geoengineering structure is to be constructed; Fig 2 is a schematic cut-away sectional side view of the finished structure; Fig 3 is a sectional plan view taken on the line Ill-Ill in Fig 2; Fig 4 illustrates one embodiment of panel for forming a retaining wail of the geoengineering structure; Fig 5 illustrates a frame for effecting tautening the geogrids of the panel shown in Fig 4; Figs 6a-6g illustrate a sequence of operations for constructing a reinforced geogengineering structure; Figs 7a and 7b illustrate use of the frame illustrated in Fig 5.

Fig 8 illustrates panel sections for assembling into one embodiment of panel for forming a retaining wall of the geoengineering structure; Fig 9 illustrates a panel assembled from the sections shown in Fig 8 and having a geogrid attached thereto; Fig 10 illustrates part of a retaining wall constructed from panels as shown in Fig 9; and Fig 1 1 illustrates edge formations that may be provided for the panel shown in * . F9 * * To facilitate an understanding of the invention, reference is firstly made to the *S..

schematic views of Figs 1-3 in which Fig I illustrates a coastal location 1 at which a reinforced geoengineering structure is to be constructed in accordance with the * principles of the invention and Figs 2-3 represent the completed structure. In Fig 1, the sea is referenced as 2, the coastal land as 3 and the seabed as 4. * *

The final reinforced structure 5 constructed at the coastal location 1 is depicted in the cut-away sectional side view of Fig 2 and the sectional plan view of Fig 3 (which is taken on the line Ill-Ill in Fig 2) The structure 5 is illustrated as being generally rectangular in plan view (Fig 3) with one longitudinal boundary being defined along the original coastal land 3 and the opposite longitudinal boundary being defined by a retaining wall constructed of a line of vertical panels 6 (see also Fig 4) located in edge-to-edge relationship. The transverse boundaries of the structure are represented by dashed lines. As shown in Fig 2, the lower regions of panels 6 are formed as ground penetrating formations 7 which have been driven a short distance into the seabed 4. Structure 5 further comprises a reinforced soil structure with compacted aggregate material 8 within which are embedded uniaxially oriented, upper and lower plastics geogrids 9. These geogrids 9 are at a level below the original water level and are in the form of lengths of geogrid material each attached to two locations on a panel which are spaced from each other by a distance less than the length of the geogrid which (after tautening -see below) forms a loop as depicted in Fig 3. Finally, the illustrated geoengineering structure incorporates a flat geogrid 10 above the level of upper geogrid 9 and embedded in the aggregate 8.

As mentioned above, the transverse boundaries of the structure are depicted by dashed lines. At these boundaries, there may, for example, be a line of retaining panels (which may -but are not necessarily -be provided with loops of geogrid material). The transverse boundaries may (as illustrated), be perpendicular to the line of panels 6. However one or more of these boundaries may extend at an obtuse angle to the line of panel 6. A further possibility is that there are no panels along the transverse sides of the reinforced structure 5.

Reference is now made to Fig 4 from which it will be seen that individual **,. panels 6 comprise a panel body 6a at the lower end of which is the ground penetrating formation 7 and at the upper end of which are two lifting eyes 6b. Panel body 6a may for example be of concrete or other suitable structural material (e.g. wood, engineering plastics etc). The ground penetrating formation 7 is of a material (e.g. steel) which allows the formation 7 to be driven into the seabed 4 by a suitable force applied to the upper edge of panel 6. Whilst the ground penetrating formation 7 is preferably of steel other materials may be used. As depicted in the drawings, the ground penetrating formation is in the form of a plate but it should be appreciated that other configurations are possible. Thus, for example, the ground penetrating formation 7 may be corrugated.

Additionally shown in Fig 4 are the upper and lower geogrids 9 which are attached to the panel body 6a. Each of these geogrids 9 is in the form of a length of material attached to two locations on the panel body 6a which are spaced from each other by a distance less than the length of the geogrid. As such, the geogrids 9 may be "opened-out" to form loops in the manner explained in the description given below. Geogrid 10 is not illustrated in Fig 4 because it is attached to panel 6 at a later stage in the construction process.

In Fig 4, the panels 6 are preferably such that adjacent panels 6 in the retaining wall structure may be connected together at their side edges by co-operating male and female formations. Ideally these formations are such that a male formation extending along the side edge of one panel may be slid relatively along a co-operating female formation which itself extends along the adjacent side edge of another panel. Thus a panel to be erected may be slid vertically downwards into position next to a pre-erected panel, with the two panels being connected together by their co-operating male and female formations.

Geogrids 9 are attached to the panel body 6a before the panel 6 is located in the water. Attachment of the geogrids may, for example, be in a factory so that the "complete unit" (i.e. panel 6 with affixed geogrids 9) is delivered to the construction site. Although not illustrated in Fig 4, the lengths of geogrid 9 may be folded, rolled or otherwise compacted against the panel body 6a for ease of transport of the assembled unit. Alternatively the pane! 6 and geogrids 9 may be delivered separately to the site where the completed unit is assembled. S...

* S*.** * The panel 6 illustrated in Fig 4 shows upper and lower geogrids 9.

Modifications are possible. Thus, for example, it is possible for a panel to have two lower grids arranged side-by-side and similarly two upper geogrids 9, again arranged side-by-side. Alternatively, if the panel 6 is for use in relatively shallow water then a *:. single geogrid (or two side-by-side geogrids) may be provided at only one level on the panel. Conversely, if the panel is for use in deeper water then it may, for example, have three or more (e.g. four or five) loops of geogrid positioned one above the other.

During construction of the retaining waU assembly, it is necessary for the geogrids 9 to be opened-out" under water so that there is little or no slack in the geogrids. Ideally the geogrids are in a tautened condition. For the purpose of opening-out the loops of geogrids 9 and removing slack (e.g. to achieve a tautened condition) a frame structure 70 as depicted in Fig 5 is employed.

Essentially, this structure 70 comprises a rectangular frame 11 (constructed of frame members 72) for which the area between the four sides is essentially open.

At each corner of the rectangular frame is a leg 73 carrying a respective lifting eye 74 The manner in which frame structure 70 is employed to tension the geogrids is described in more detail below.

A sequence of operations for producing a reinforced structure is now described with reference to Figs 6a-6g.

Fig 6a shows a body of water 80 which has been excavated using conventional techniques (e.g. dredging) to form a trench 81 in the seabed 82, the original level of the seabed being depicted by the dashed line 83.

A panel 6 as depicted in Fig 4 is arranged so that the geogrids 9 surround a frame 70 (of the type shown In Fig 5). The panel 6 and associated frame 70 are then lifted by means of a crane or similar lifting apparatus (not shown) and positioned over the water at the intended location for the panel 6 (Fig 6b). The panel 6 and frame 70 are then simultaneously lowered into the water and panel 6 is driven (e.g. about I *..I metre) into the seabed 82 by means of a hammering or vibrating force depicted in Fig 6c b the arrow 84. This force for driving the lower end of the panel 6 into the seabed 82 may be produced by any conventional form of powered hammer :. assembly, examples of which will be well known to persons skilled in the art. The depth to which the panel 6 needs to be driven into the seabed 82 is only that which is required to ensure that the panel 6 is able to stand upright without further support afld as indicated above, may be about 1 metre. Additionally it should be noted that the ground penetrating formation 7 of adjacent panels 6 may be driven to different depths in an undulating seabed so that the upper edges of the panel 6 are level with each other.

In the next step (Fig 6d), the geogrids 9 are tautened (to remove slack) by moving the frame 70 (by means of the aforementioned crane) away from the panel 6 towards the shore (i.e. in the direction of arrow 85 -see Fig 6d). This operation is depicted in more detail in Figs 7a and Tb which schematically illustrate a panel 6 with geogrids 9 attached thereto. Also shown in Figs 7a and 7b is a frame 70 for which the legs 73 thereof are surrounded by the geogrids 9 (see particularly Fig 7a). As will be noted from Fig 7a, the geogrids 9 are initially "slack" and may, in fact, have folds or rolls of geogrid material which need to be opened-out to form a loop in which there is no slack material. By moving the frame 70 away from the panel 6, the geogrids 9 are unfolded and all slack material is taken-up so that, as schematically depicted in Fig 7b, the geogrids 9 adopt a somewhat rectangular loop structure with the geogrids being in a vertical plane.

In the next operational step, aggregate material 86 (the "soil") is deposited from above into the loops of the underwater geogrids 9 (Fig 6e). Conveniently deposition of the aggregate material 86 is from a funnel structure schematically indicated by reference numeral 87 in Fig 6e. During this deposition procedure, the frame 70 is progressively lifted in the direction of arrow 88 since it will be appreciated that as the loops of geogrid 9 become fulled with the aggregate material the loop structure can be maintained without the need for the frame 70.

Aggregate material 86 is compacted as it is introduced into the loops of geogrid 9. For this purpose, the funnel 87 may be a vibrating unit and be positioned so that its stem locates within the deposited aggregate material to effect compaction *:" thereof. Alternatively, a separate vibrating lance may be used. All of these techniques are well-known in the art.

One preferred construction method contemplated in accordance with the invention involves erection of a number of panels 6 in side-by-side relationship and filling the loops of geogrids 9 of these panels with aggregate material 86 using the procedure described above. Once the loops have been filled, additional aggregate material 86 may be introduced around the loops of geogrid 9 (as depicted in Fig 6f) again with vibration compaction. In this way, the level of aggregate material both within and surrounding the loops may be raised to the level of the water on the other side of panel 6. At this point, a flat geogrid 10 (see also Fig 2) may be provided on top of the previously deposited aggregate and then itself embedded in an upper aggregate layer 89 (see Fig 6g) to produce the final structure.

Reference is now made to Fig 8 which illustrates a further embodiment of panel 100 (formed as lower and upper sections 101 and 102 respectively) which may be used for constructing the outer retaining wall of the geoengineering structure and which is in effect equivalent to panel 6 in Fig 2.

Lower panel section 101 is moulded from plastics material and has a plate-like body 103 depicted as having side edges 104 and 105 as well as upper and lower edges 106 and 107 respectively. On one face of the plate-like body 103 is a grid formed of reinforcing ribs 108-111. Within this grid, there are two ribs 108 and four ribs 109 all parallel to the side edges 104 and 105 and extending from upper edge 106 towards lower edge 107. As shown in Fig 8, the lower ends of ribs 108 and 109 converge in height towards the lower edge 107 down to the level of the surface of body 103. That region of the panel section 101 between, on the one hand, the level at which the ribs 108 and 109 begin to taper downwardly and, on the other hand, the lower edge 107 of the panel section 101 is a ground penetrating region so that the panel section 101 may be driven into the water bed up to the level where the ribs 108 and 109 begin to taper. Typically this distance will be about 1 metre for a panel 100 (comprised of sections 101 and 102) which has a total height of 4 metres.

Ribs 108 have a strip portion projecting above the level of ribs 109. Along this strip portion is a line of apertures 112 positioned such that an aperture 112 in one rib 108 aligns with an aperture 112 in the other rib 108. Additionally, the strip portions of ribs 108 each extend beyond the upper edge 106 of panel body 103 to form lugs 113, in each of which Is provided an aperture for convenience referenced as 112a, the two apertures 112a being in alignment with each other.

Ribs 110 and 111 extend perpendicularly to ribs 108 and 109. As shown in Fig 8, ribs 110 (being of greater height than ribs 111) have a strip portion which projects above ribs 111. Provided In each such strip portion is a line of apertures 1 14 positioned such that an aperture 114 in one rib 110 aligns with an aperture 114 in an adjacent rib 110.

Reference is now made to upper panel section 102, for which only the lower region thereof is shown in Fig 8. Panel section 102 is similar to panel section 101 in that it is of the same width and has, on one surface, a grid of reinforcing ribs 121 to 124. Provided along a strip portion of each rib 121 which projects above ribs 122 is a line of apertures 125 positioned such that any one aperture 125 in a rib 121 aligns with an aperture 125 in the other rib 121. For convenience, the lowermost aperture in each rib 121 is referenced as 125a.

The ribs 123 and 124 on upper panel section 102 extend perpendicularly to the ribs 121 and 122. Along a strip portion of the ribs 123 which projects above ribs 124 is a line of apertures 126 positioned such that an aperture 126 in one rib 123 aligns, firstly, with an aperture 126 in an adjacent rib 123 and secondly with an aperture 114 in a rib 110 when the two panel sections 101 and 102 are assembled together in the manner described below.

The lower rib 124 (designated as 124a for convenience) effectively defines a lower edge for the panel section 102. Ribs 121 terminate at the level of the lowermost rib 124a whereas ribs 122 project beyond rib 124a by a short distance as referenced by 1 22a.

The manner in which panel sections 101 and 102 are assembled together to form a complete panel 100 may be appreciated from a consideration of Figs 8 and 9.

As shown in Fig 8, panel section 101 and 102 are positioned such that the lowermost rib 124a of panel section 102 is positioned above the upper ends of the ribs 108 and *..e 109 of lower panel section 101. Panel section 102 is then lowered so that its I I* .1.

* 1 lowermost rib 124 lies against the upper ends of ribs 108 and 109 with the lower ends 122a of the ribs 122 (on upper panel section 102) projecting below the upper ends of ribs 109 and lying thereagainst. Similarly the lugs 113 on lower panel section 101 lie against the lower ends of ribs 121 such that all apertures 112a and 125a are in alignment. A bar 130 (see Fig 9) is now inserted through the aligned apertures 112a and 125a. *

The assembled panel is shown in Fig 9 which further illustrates a loop of geogrid material 140 (equivalent to the loop 9 shown in, and described with reference to, Fig 2). More specifically, each end of the geogrid 140 is fixed to a respective rod 141 (e.g. of fibreglass) which locates in aligned apertures 114 of the horizontal ribs on panel section 101. The spacing between the two rods 141 is somewhat less than the overall length of the geogrid 140 so the latter may initially be folded, furled or rolled on to itself, as very schematically depicted by the "wavy line 142 in Fig 9. For convenience, Fig 9 illustrates only one geogrid 140 but it will be appreciated that a plurality of such geogrids 140 may be provided at different heights on the panel section, depending on the depth of water in which the panel is to be erected. It will be further appreciated that the loop of geogrid 140 will ultimately be subjected to an underwater manipulation operation (such as described above) to produce a tautened loop.

Panels 100 (with attached geogrid loops 140) are intended to be erected in side-by-side relationship to produce a retaining wall for the geogengineering structure. Such a retaining wall is illustrated in Fig 10 which depicts three panels 100 in side-by-side relationship although it will be appreciated that many more such panels will be used for the construction of a retaining wall. Further illustrating in Fig are flat geogrids 150 (equivalent to geogrid 10 in Fig 2) which are attached to the panel by means of rods 151 which locate through aligned apertures 112 in ribs 108 and/or through aligned apertures 125 in ribs 121 (depending on whether the geogrids are attached to the lower panel section 101 or upper panel section 102). It wifi be appreciated that the flat geogrids 150 are only attached after the panels 100 have been erected and the geogrids 140 tautened and embedded in aggregate.

Although not illustrated in Figs 8-10, it is preferred that the sidemost ribs 111 S...

(of lower panel section 101) and 122 (of upper panel section 102) are configured to * S allow the panel 100 to be connected to two similar panels 100 along their edges by *: relative sliding movement. Examples of such edge formations are shown in Fig 11 S...

from which it will be seen that the side edge of one panel 100 is provided along its length with a rail 161 having a bulbous head 162 whereas extending along the edge of art adjacent panel 100' is a slot 163 opening into a bulbous recess 164. This arrangement allows the two panels 100 and 100' to be slotted together during assembly of a retaining wall constructed from the panels by positioning the lower edge of one panel (say panel 100) above the upper edge of the other panel 100' and then lowering the higher panel so that the head 162 slides relatively along the recess 164. It will be appreciated that the other edge of panel 100 (this edge not being sen in Fig 11) is provided with a slot opening into a bulbous recess. Similarly the unseen other side edge of panel 100' is provided with a rail provided with a bulbous head.

It will be appreciated from the foregoing description that the invention provides a convenient method of constructing a reinforced geotechnical structure in a body of water which avoids disadvantages associated with conventional methods, e.g. the need to drive sheet piling deep into the ground.

Whilst the invention is applicable particularly to the construction of reinforced geotechnical structures in a body of water and has been described with specific reference thereto, it should neverttieless be appreciated that the invention is more generally applicable and may be employed for the construction of geotechnical structures in other environments.

Thus, the invention should be broadly construed as encompassing a method of constructing a reinforced geotechriical structure comprised of particulate material, the method comprising the steps of: (a) erecting a wall comprised of a plurality of vertically extending panels supported by the ground, at least some of the panels having reinforcing elements affixed thereto that are in a reinforcing configuration in which they extend transversely away from panels within the volume in which the structure is to be *S.* *****. erected, and

S

S..... * .

(b) depositing particulate material into said volume and form a structure comprised of the particulate material reinforced by said reinforcing elements.

S *.b *

Therefore, in its broadest aspect, the present invention embraces not only construction of geotechnical structures in water but also on "dry land". All features of the invention as described above specifically in relation to construction In water are applicable mutatis mutandis to construction in other environments. Thus reference to operations effected in or under water should be considered as being applicable to the same operation but effected in a different environment.

Claims

CLAIMS1. A method of constructing in a body of water a reinforced geotechnical structure comprised of particulate material, the method comprising the steps of: (a) erecting in the body of water a wall comprised of a plurality of vertically extending panels supported by the bed at the bottom of the water, at least some of the panels having reinforcing elements affixed thereto that are in a reinforcing configuration in which they extend transversely away from the panels within the volume of water in which the structure is to be erected, and (b) depositing particulate material into said volume to displace the water and form a structure comprised of the particulate material reinforced by said reinforcing elements.
2. A method as claimed in claim 1 wherein the reinforcing elements are pre-affixed to the panels before the latter are erected in the water.
3. A method as claimed in claim 1 or 2 wherein the reinforcing elements are flexible and are subjected to an underwater manipulation operation to bring them into their reinforcing configuration. * *
4. A method as claimed in claim 3 wherein the reinforcing elements are introduced under water in a folded or other compacted configuration on which said *. underwater manipulation is effected to bring the elements into the reinforcing * configuration.
5. A method as claimed in claim 3 or 4 wherein the reinforced configuration is in a taut condition.
6. A method as claimed in any one of claims 1 to 5 wherein, in their reinforcing configuration, the reinforcing elements are in the form of loops.
7. A method as claimed in claim 6 wherein the openings defined by the confines of the loops are substantially vertical.
8. A method as claimed in claim I wherein the reinforcing elements are flexible and are provided in length attached to the panels at two locations spaced by a distance less than the length of the reinforcing element attached between these locations and said reinforcing elements are subjected to an underwater manipulation operation to bring the reinforcing elements into their reinforcing configuration as a loop.
9. A method as claimed in claim 8 wherein said underwater manipulation is effected by providing a removable configuring device within the bounds of the length of the reinforcing element, and moving the configuring device away from the panel to bring the reinforcing element into its reinforcing configuration in the form of a loop.
10. A method as claimed in claim 9 wherein the configuring device is progressively lifted out of the loop as the particulate material is deposited therein.
11. A method as claimed in claim 10 wherein the movement of the configuring device is effected by a crane or other lifting apparatus capable of effecting horizontal and vertical movement of the configuring device. *S.. * * ***.
12. A method as claimed in claim 9 wherein the configuring device comprises a frame having four legs that locate within the loops. **** *** *
13. A method as claimed in any one of claims 1 to 12 wherein the reinforcing elements are mesh structures, preferably plastics geogrids.
14. A method as claimed in claim 13 wherein mesh structures are plastics geogrids having transversely spaced, longitudinally extending, oriented strands.
15. A method as claimed in claim 14 wherein the geogrids are uniaxially oriented.
16. A method as claimed in any one of claims 1 to 15 wherein the lower edges of the panels comprise ground penetrating structures and the panels are driven into the bed of the body of water.
17. A method as claimed in claim 16 wherein the ground penetrating structure is of metal.
18. A method as claimed in claim 17 wherein the ground penetrating structure is a plate.
19. A method as claimed in claim 17 wherein the ground penetrating structure is of corrugated configuration.
20. A method as claimed in claim 16 wherein the ground penetrating structure comprises a plate provided with downwardly converging ribs.
21. A method as claimed in any one of claims I to 16 wherein the panels are connected together at their side edges by co-operating male and female fomiations.
22. A method as claimed in claim 21 wherein said formations are such that the male formation at the side edge of one panel may be slid relatively along the S...female formation at the adjacent side edge of another panel whereby a panel to be erected may slide vertically downwards into position next to a pre-erected panel. I..:
23. A method as claimed in any one of claims ito 22 wherein during step (b) the particulate material is compacted by vibration.

S

*. .:
24. A method as claimed in any one of claims ito 23 wherein the erected panels extend above the water level.
25. A panel for use in constructing a retaining wall of a geoengineering structure in a body of water, the panel having a lower support formation for engagement with the bottom of the body of water to support the panel upnght in the water, and said panel being provided with a length of a reinforcing element for forming reinforcement in compacted particulate material.
26. A panel as claimed in claim 25 wherein said lower support formation is a ground penetrating formation.
27. A panel as claimed in claim 26 wherein the ground penetrating formation is in the form of a plate.
28. A method as claimed in claim 27 wherein the ground penetrating structure is of metal.
29. A method as claimed in claim 28 wherein the ground penetrating structure is a plate.
30. A method as claimed in claim 29 wherein the ground penetrating structure is of corrugated configuration.
31. A panel as claimed in any one of claims 25 to 30 wherein the reinforcing element is a mesh structure.
32. A panel as claimed in claim 31 wherein the mesh structure is a plastic S...geogrid.*...S.*
33. A panel as claimed in claim 32 wherein the geogrid comprises : transversely spaced, longitudinally extending, oriented strands. *.*S

*.
34. A panel as claimed in claim 33 wherein the geogrid is uniaxially * ** oriented. *

**.... * .
35. A panel as claimed in any one of claims 25 to 34 wherein the mesh structure is in a length attached to the panel at two locations longitudinally spaced along the length of the mesh structure.
36. A method of constructing a reinforced geotechnical structure comprised of particulate material, the method comprising the steps of: (a) erecting a wall comprised of a plurality of vertically extending panels supported by the ground, at least some of the panels having reinforcing elements affixed thereto that are in a reinforcing configuration in which they extend transversely away from panels within the volume In which the structure is to be erected, and (b) depositing particulate material into said volume and form a structure comprised of the particulate material reinforced by said reinforcing elements.
37. A method as claimed in claim 36 adopting the features of any one of claims 2 to 23 as applied to an environment other than a body of water.
38. A panel for use in constwcting a retaining wall of a geoengineering structure, the panel having a lower support formation for engagement with the ground to support the panel upright, and said panel being provided with a length of a reinforcing eiement for forming reinforcement in compacted particulate material. S.. * *SS..... * . *5SS S...S *5* * * . S * a.S