Cellular structures

Abstract

A cellular structure includes a plurality of interconnected cells of fabric material. The cells are at least partially filled with a composite fill material that includes a particulate material and a bonding agent. A cellular unit made up of a plurality of the interconnected cells may have an associated load-bearing frame to enable lifting and/or transportation of the structure. The fill material is preferably resilient.

Claims

1. A method, comprising: at least partially filling an open cellular unit with a first fill material comprising a composite fill material comprising a mixture of first particulate material and a bonding agent, the open cellular unit comprising a plurality of interconnected cells comprising a fabric material, and the open cellular unit being on or in a frame; curing the first fill material to provide a layer of a solid bonded composite fill material; depositing a second fill material onto the layer of the solid bonded composite fill material, the second fill material comprising a second particulate material, wherein the second particulate material is the same or different from the first particulate material; and using the frame to lift and/or transport the filled open cellular unit.

2. The method of claim 1, wherein the frame comprises (i) an outer frame ring; (ii) at least one cross-piece attached to the outer frame ring and configured to pass underneath the open cellular unit; and (iii) at least one upright member attached to the outer frame ring and extending in a vertical direction from the outer frame ring.

3. The method of claim 2, wherein the at least one upright member includes a first end proximate to the outer frame ring and a second end distal from the outer frame member, and wherein the first end includes a socket and the second end includes a hole aligned with the socket.

4. The method of claim 1, wherein the fabric comprises a single strip of fabric folded back and forth on itself to form the plurality of interconnected cells.

5. The method of claim 1, wherein the bonding agent bonds the solid bonded composite fill material to the fabric material.

6. The method of claim 1, wherein the solid bonded composite fill material defines a lowermost layer.

7. The method of claim 1, wherein the solid bonded composite fill material defines an uppermost layer.

8. The method of claim 1, wherein the bonding agent comprises an elastomeric material.

9. The method of claim 1, wherein the solid bonded composite fill material has a ratio of the bonding agent to the first particulate material ranging from 1:7 to 1:15 by weight.

10. The method of claim 1, wherein the plurality of interconnected cells are open such that the solid bonded composite fill material is exposed at a top surface of the cellular structure, a bottom surface of the cellular structure, or both.

11. The method of claim 10, further comprising depositing a second layer of the composite fill material onto the second fill material and curing the second layer of the composite fill material to provide a layer of a second solid bonded composite fill material; wherein the second fill material is contained between the solid bonded composite fill material and the second solid bonded composite fill material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Some preferred embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a schematic perspective view of a prior art cellular confinement system;

(3) FIG. 2 shows a schematic perspective view of a cellular structure including a fill material in accordance with an embodiment of the invention;

(4) FIG. 3a shows a schematic plan view of a cellular unit;

(5) FIG. 3b is a perspective view of the cellular unit of FIG. 3a;

(6) FIG. 4 shows a schematic exploded view of two stacked cellular structures in accordance with an embodiment of the invention;

(7) FIG. 5 shows a schematic perspective view of a filled cellular unit and associated frame in accordance with a preferred embodiment of the invention;

(8) FIG. 6 is an exploded view of the cellular structure of FIG. 5;

(9) FIG. 7 shows the cellular structure of FIG. 5 with the addition of a lifting frame; and

(10) FIG. 8 shows a barrier or wall formed from the cellular structures of FIG. 5.

DETAILED DESCRIPTION

(11) There is shown in FIG. 1 a prior art cellular confinement system 1 including a number of interconnected cells 2 formed from a fabric material such as a nonwoven geotextile available from Terram Limited. For civil engineering applications such as erosion protection the cell diameter is typically 25-45 cm and the cell depth is typically 10-15 cm. For example, the ‘Erocell 25’ product manufactured by Terram Ltd. is available in a panel measuring 10 m×7 m and containing around 1900 cells sized 25×25×10 cm. The flexible panel is collapsed into a flat state and rolled up for ease of delivery. Upon arrival at the site the panel is expanded and may be anchored. The panel may be pinned out on the installation surface to retain the open cell shape and size before filling. Once the panel has been fixed and anchored in place, filling is carried out e.g. using a bulldozer to deposit soil, sand or other filler material as desired.

(12) There is shown in FIG. 2 a cellular structure in accordance with an embodiment of the present invention. The cellular unit 4 is made up of interconnected tubular cells 5, 6 formed of a geotextile material. The tubular cells 5, 6 have a diameter of 250 mm and a depth of 750 mm. The cellular unit 4 is taller than the cellular panels typically used in civil engineering applications.

(13) With reference to FIGS. 3a and 3b, the cellular structures of FIG. 2 may be formed by taking a strip 3 of nonwoven material and folding it back and forth onto itself. The strip 3 has a depth d of 750 mm. Before each fold, adhesive 7 is applied at a number of spaced apart locations along the strip 3. The resultant pleated stack is then openable into a panel 9 having 21 generally tubular, interconnected cells 5, 6 formed by the folded layers between the adhesive locations. The overall width w of the panel 9 is about 1 metre. Adhesive joints formed in this way have been found to be up to 85% as strong as the nonwoven material itself. A special adhesive is preferred which can retain its bonding strength across a wide temperature range.

(14) According to another preferred method of manufacture the tubular cells 5, 6 may be formed individually and then interconnected by stitching instead of using adhesive. The choice of sewn joints instead of adhesive joints may depend on the material used for the cells.

(15) Turning back to FIG. 2, it can be seen that all of the tubular cells 5, 6 of the cellular unit 4 are filled with a resilient composite material 8 which in this embodiment is a mixture of sand and natural latex. The mixture ratio is approximately 8% of adhesive by weight. Calcium chloride granules or any other suitable catalyst is added to the mixture at the point of filling to initiate chemical cross-linking of the latex rubber. The resultant composite fill material 8 is solid but porous to liquids and gases. The latex bonding agent acts to bind together the sand particles and to bond the composite 8 to the geotextile fabric of the cells 5, 6. Both the composite material 8 and the fabric material of the cells 6 are flexible, resulting in an elastic and deformable cellular unit 4.

(16) Of course, the composite fill material 8 may not completely fill each cell 5, 6. Preferably the composite fill material 8 forms a base and/or upper fill layer for the cells 5, 6. The rest of the fill may be formed by another fill material, such as an unbonded fill material. One material suitable for filling the ‘core’ of the cells is a mixture of particulate material such as sand with a binder such as polypropylene fibres.

(17) It will be seen that the cellular unit 4 has an undulating outer surface formed by the partly cylindrical tubular cells 5 around the outside of the unit 4. The interior of the unit 4 includes generally polygonal tubular cells 6 formed by the intersecting internal fabric walls and bonding points. Whereas the fabric walls of the inner cells 6 are constrained, the outwardly-facing walls of the perimeter cells 5 are more free to bulge upon filling, resulting in a curved outer surface to each perimeter cell 5.

(18) The cells 5, 6 are open at the top and bottom of the cellular unit 4. Thus when the unit 4 is laid on a surface the composite fill material 8 is in direct contact with the surface and its conformability provides a high coefficient of friction. Alternatively, the cellular unit 4 can include a base sheet (not shown) to improve stability for the exposed composite 8 on the base of the structure. Such a base sheet is preferably flexible so as not to reduce the coefficient of surface friction. The cellular unit 4 may be placed on such a base sheet prior to filling in order to assist with the manufacturing process. A sheet of lightweight PVC-coated polyester mesh may be used. Other base and/or top sheets can be applied as desired e.g. for particular applications.

(19) The cellular unit 4 shown in FIG. 2 can be deployed on its own e.g. as a defensive unit or it can be stacked with other units to form a larger barrier structure. The undulating outer surface of the cellular unit 4 can provide a cushioning effect. It can also help to interlock adjacent units in a partially tesselated arrangement.

(20) FIG. 4 shows a cellular structure 10 being stacked on top of another cellular structure 12. Both structures 10, 12 include interconnected tubular cells 14, 15 of a flexible geotextile material. The base structure 12 may be a single cellular unit or it may be made up of more than one cellular unit stacked side-by-side. The outer cells 14 and inner cells 15 of the base structure 12 are filled with a composite fill material 8 in the same way as is described above with respect to FIG. 2. As before, the cellular structure 12 has an undulating outer surface formed by the partly cylindrical perimeter cells 14 around the outside of the structure 12. The structure 12 therefore provides a cushioning outer surface particularly suitable for use as a crash barrier or the like. The undulating outer surface can advantageously enhance the resilient response of the structure 12 and could even result in deflection of an impacting body.

(21) The cellular structures 10, 12 shown in FIG. 4 differ from that of FIGS. 2 and 3b in that each structure 10, 12 is provided with a skirting band 16 around the upper perimeter of the structure 10, 12. The skirting strip 16 can be formed from a different material to the cells 14, 15 such as a stiff plastic, e.g. HDPE or PVC, for reinforcement purposes. Due to the solid nature of the bonded composite fill material 8, the skirting strip 16 is not required to prevent particulate material escaping from between the structures 10, 12, and is preferably omitted. The skirting strip 16 is merely shown for illustrative purposes. Where employed, preferably the skirting band 16 is formed from a strip of the same geotextile material as the cells 14, 15. The skirt portion is preferably flexible and/or liquid permeable, like the fabric material of the cells 14, 15, making it easier to bend the strip 16 around the cells and tuck the band 16 inside or against the cell walls of juxtaposed structures. Although the material is flexible enough to allow the band 16 to bend into the desired shape, it is also sufficiently stiff that the band 16 will hold its shape and lie flat against the cell walls.

(22) The skirting strip 16 is wrapped around the outside of the perimeter cells 14 in the cellular structures 10, 12 and fixedly attached to an upper part of the cell walls. The skirting strip 16 may be attached to the outside of the cells 14 by sewing and/or gluing, for example. The attachment method used may depend on the respective material(s). A slotted band 16 may instead be fitted inside the cells 14, adjacent to the perimeter walls, and fixedly attached if required. Of course, the skirting strip 16 may not extend around the whole perimeter of the structures 10, 12, and more than one strip 16 may be used.

(23) The skirting strip 16 is attached at the upper end of the base structure 12, partially overlapping with a top portion of the perimeter cell walls and extending above the top of the cells 14 so as to form an upstanding skirt portion. For cells that are 150 cm deep the skirting band 16 may be, for example, 15 to 45 cm deep, with some of the skirting strip 16 overlapping with the cell walls and at least half of its depth left protruding beyond the top of the cell walls. The material of the skirting strip 16 is sufficiently rigid that the strip 16 stands up vertically without substantially crumpling or bending.

(24) FIG. 4 illustrates that when stacking two cellular structures 10, 12, the lower portion of the cell walls in the upper structure 10 fit inside the skirting strip 16 which extends around the perimeter of the lower structure 12. The skirting strip 16 may optionally be fixedly attached to or held against the cell walls of the upper structure 10 by any suitable means e.g. adhesive, sewing, fasteners, etc. The skirting band 16 can help to guide and align the cells when stacking such structures 10, 12 on top of one another. The resultant wall or barrier structure will have substantially vertical perimeter walls on all sides with a reinforcing seal being formed by the skirting strip 16 between the vertically juxtaposed structures 10, 12. The skirting portion may improve the overall strength and impact resistance of the stacked structure. However, such a skirting strip or other such seal means is in no way essential, and is in fact omitted in preferred embodiments of the invention.

(25) As the external skirting strip 16 extends upwardly, the cellular structures 10, 12 can be stacked or deployed in any order and can be used the same way up in all of the layers, making it simple to construct a stacked system. When a number of structures have been stacked on top of one another, e.g. to form a wall or barrier, the skirting strip 16 protruding from the uppermost structure can be folded down to at least partially cover the exposed fill material. Folding of the skirt portion is possible due to the flexibility of the fabric material. Alternatively (but not shown), the skirting band 16 may be integrally formed with the cell walls e.g. where the structures 10, 12 are formed of a single cellular unit. For example, the perimeter cells 14 of a cellular unit may be provided with split wall dimensions. The inwardly-facing half of a perimeter cell 14 may be of a standard depth matching the inner cells 14 in the unit while the outwardly-facing half of each perimeter cell 14 may have an extended wall which is deeper than standard, the extended wall portion acting as a skirt.

(26) The upper cellular structure 10 may be stacked on top of the lower structure 12 before being filled, as shown, or one or more pre-filled structures may be stacked up. However, for ease of handling it may be preferred to manufacture a barrier by filling each cellular structure as it is stacked. Curing of the fill material during stacking can advantageously provide bonding between the stacked layers.

(27) With reference to FIGS. 5 to 7 a cellular structure 18 in accordance with a preferred embodiment includes a cellular unit 20 embedded within a load-bearing frame 22. The cellular unit 20 is substantially the same as that described above with respect to FIG. 2, i.e. the fill material 24 is a sand/adhesive composite, and those features described above will not be repeated. However, the cellular unit 20 may be filled instead with a different material, for example a solid particulate material such as concrete, aggregate, ballast materials (e.g. brick, broken concrete, granite, limestone, sandstone, shingle, slag and stone), crushed rock, gravel, sand, clay, peat or soil, or any mixture of these. As is preferred, the cellular unit 20 is not provided with any kind of skirting strip around its upper periphery.

(28) The load-bearing frame 22 includes an outer frame ring 26 to which there are attached two diagonal cross-pieces 28 which form the base of the frame 22. Four upright members 30 are attached at a lower portion to the corners of the frame ring 26 and are designed to extend slightly higher than the cellular unit 20, to allow for coupling to another frame stacked above. Further frame rings can be provided, e.g. spaced over the vertical extent of the structure. The frame 22 is sized to generally match the perimeter of the cellular unit 20 and to maximise the points of the contact between the cellular unit 20 and the frame 22. The base of the cellular unit 20 is covered by a sheet 21 of flexible fabric material such as a lightweight PVC-coated polyester mesh. The base sheet 21 is too thin to be discernible in FIG. 6. The base sheet 21 is inserted inside the frame 22, over the cross-pieces 28, but in an alternative embodiment it could extend at least partially beneath the frame ring 26 instead or as well.

(29) It will be understood that the use of two diagonal cross-pieces 28 can stabilise the frame ring 26 to an extent but will still allow the frame 22 to twist and bend. In particular, the base of the frame 22 can conform to an uneven surface. The cross-pieces 28 are preferably thin and narrow so as to interfere as little as possible with the contact between the cellular unit 20 and the ground, while still bearing the load of the cellular unit 20 and transmitting the load to the rest of the frame 22. The frame 22 is preferably made of stiff metal components.

(30) The upright corner members 30 are provided with sockets 32 spaced slightly from the bottom of the frame. The top of each upright member 30 terminates in a right angle and a horizontal connector 33 with a hole 34 which is arranged align with the socket 32 on a frame stacked above, as will be explained in more detail below. The upright members 30 are also provided with holes 36 which allow for connection of a top lifting frame 37 or other hoisting means, e.g. as shown in FIG. 7. The exemplary lifting frame 37 includes a loop 39 centred over the cellular unit 20 which facilitates rapid deployment of the structure 18, for example by a fork lift truck, crane or HIAB-equipped lorry. The lifting frame 37 is designed to spread the load carried by the supporting frame 22.

(31) The cellular structure 18 is manufactured as follows. The frame 22 is constructed and a base sheet 21 is inserted inside the frame ring 26, on top of the cross-pieces 28. Next the cellular sub-assembly of the cellular unit 20 is opened out and stood on top of the base sheet 21, inside the frame 22. The cellular sub-assembly may be provided collapsed in flat-pack form or even flattened and rolled up. To aid in opening out the cellular sub-assembly, the cells may be pinned open prior to filling. The fill material 24, for example a mixture of sand and latex adhesive together with a cross-linking catalyst, is then poured into the tubular cells to fill them to the desired level and left to solidify. If a particulate fill material is used without a bonding agent then compaction may be required.

(32) In order to increase the mass of the cellular structure 18 and the coupling between the cellular unit 20 and the frame 22, the fill material 24 is also preferably poured into the gaps between the perimeter walls of the cellular unit 20 and the frame ring 26. It will be seen from FIGS. 5 to 7 that the lower end of the cells are effectively encased by the fill material 24 within the frame ring 26. The fill material 24 may not bond completely to the frame 22 but it will help to transmit forces and enable the overall structure to bend and flex in a unified response e.g. to impact.

(33) The cellular structure 18 can be used on its own or in combination with other such structures. The load-bearing frame 22 allows each cellular unit 20 to be more easily handled, e.g. picked up and transported to a desired location for use. As the structure 18 is pre-filled it can be rapidly deployed to instantly form a barrier or defensive wall. The size of the structure 18 can be adapted depending on its intended use.

(34) FIG. 8 shows one example of how a barrier structure can be built up from a plurality of pre-filled cellular structures 18. In this example, 12 cellular structures 18, 18′, each with their own frames, are interconnected to form a crash barrier capable of passing the British Standard PAS 68 vehicle crash test. The structures 18, 18′ may not all have the same fill material. Each structure 18, 18′ may also contain a mixture of fill materials within its cells.

(35) Structures 18, 18′ stacked side-by-side are connected to one another by link plates 38 which couple adjacent sockets 32. The link plates 38 may be bolted or screwed against the sockets 32. It can be seen that the bevelled corners of the frame rings 26 leave room for the sockets 32 to abut and space to insert a link plate 38 between them. Link plates 38 can be attached both above and below each pair of coupled sockets 32.

(36) An upper structure 18′ can be stacked on top of a lower structure 18 with the horizontal connectors 33 and holes 34 at the top of an upstanding member 30 of the lower structure 18 aligned underneath the sockets 32 of the upper structure 18′. The vertically stacked upright members 30 can then be bolted together via the sockets 32 and connectors 33. Link plates 38 are used to sandwich the sockets 32 and connectors 33. While the connections hold adjacent structures 18, 18′ firmly together both horizontally and vertically, the spacing between connections at the corners of each frame 22 ensures that the overall barrier is not rigid and can still flex upon impact.

(37) It is also shown in FIG. 8 how horizontal struts 40 can be fixed across the top perimeter of a frame 22, extending between the connectors 33, e.g. by bolts 42 passing through the strut 40 and a corner connector 33 below. Link plates 38 can be used to span adjacent struts 40 and to couple together adjacent uprights 30 at the same time. Adjacent frames 22 are therefore connected together at both their upper and lower ends, even in the top layer of a stack.

(38) It will be appreciated that FIG. 8 merely illustrates one examples of a barrier system and that the cellular structures 18 can be stacked both horizontally and/or vertically in as many layers as is desired to form a barrier of desired dimensions.