GB1577149A - Method of reinforcing and stabilising soil - Google Patents

Description

(54) A METHOD OF REINFORCING AND STABILISING SOIL (71) We, IMPERIAL CHEMICAL INDUS TRIES LIMITED, Imperial Chemical House, Millbank, London SW1P 3JF a British Company do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to the use of certain warp knitted fabrics for soil reinforcement and stabilisation.

According to one aspect of the present invention, a method of reinforcing and stabilising soil comprises incorporating therein at least one fabric layer constituted by a warp knitted fabric having high tenacity, synthetic polymeric, continuous filament yarns inlaid in the warp direction.

Such warp knitted fabrics with high tenacity yarns inlaid in the warp direction only are eminently suited to reinforcing soil stuctures when it is necessary only to withstand loading in a single direction. Examples of such uses are the reinforcement and stabilisation of soil embankments in which the fabric layers are positioned above one another and parallel to the ground level, and the anchoring of concrete or other retaining walls behind which soil layers are built up between fabric layers affixed at one end thereof to the walls. This fabric structure is advantageously utilised in such end-uses because of its ability to substantially eliminate all the initial strain produced by deformation in conventional woven fabrics when used in similar situations. In other words.

the unidirectional alignment of the high tenacity yarns within the structure of the warp knitted fabric greatly reduces the highstrain, low stress associated with conventional woven fabrics when a load is initially applied. This fabric structure exhibits high strength/low extension in the warp direction and low strength/high extension in the weft direction.

According to another aspect of the present invention, the method utilises a warp knitted fabric having such high tenacity yarns inlaid in both the warp and weft directions. Such fabric is utilised in circumstances of soil stabilisation and reinforcement where high strength/low extension characteristics are required in both warp and weft directions.

The yarns of the warp knitted fabric which are knitted together and "bind-in" the inlaid high tenacity yarns may exhibit lower tenacities than the inlaid yarns. Both the knitted yarns and the in-laid yarns may be composed, for example, of polyester, polyamide, or polypropylene.

The continuous filaments of the high tenacity yarns desirably have a tenacity of at least 6g/decitex, preferably greater than 7 g/decitex. These yarns may be flat yarns or twisted yarns, preferably with a yarn decitex in the region of 1100. The continuous filaments of the knitted, binder yarns generally have tenacities less than 4.5 g/ decitex, preferably in the range 3 to 4 g/ decitex. These yarns may be bulked yarns or flat yarns, for example, and preferably with a yarn decitex of at least 100.

The fabrics may be produced on Raschel, Compound needle, or Bearded needle, warp knitting machines. The knitting method used involves a technique, known in the warp knitting art as the "evasion technique", wherein only the bind-in yarns are picked up and knitted by the needles and the high tenacity yarns are laid-in.

Various extensibilities in the fabrics can be achieved by varying the directional linearity of the inlaid yarns either in the warp direction alone or in both the warp and weft directions.

A typical warp knitted fabric for use. in the present invention is illustrated in the following Example:- Machine: Mayer Raschel; 20 gauge.

Yarns: (a) 167 decitex 30 filament bulked poly ester yarn; filament tenacity 3.5 g/ decitex.

(b) 110 decitex, 96 filament flat poly ester yarn twisted to 100 turns/metre; filament tenacity 7.5 g/decitex.

Knitting Notation: Front bar: full set; yarn (a) knitting 1-0/2-3 Middle bar: full set; yarn (b) knitting 0-0/1 - 1/0-0/2-2 Back bar: full set; yarn (b) knitting yarns (b) were inlaid at 17 per cm.

Fabric Properties: Weight: 309 g/sq metre Strength in Warp Direction (da N): 603 (5 cm wide fabric strip) Strength in Weft Direction (da N): 184 (5 cm wide fabric strip) Extensibility (warp direction): 15% Extensibility (weft direction): 84% Pore size distribution (0,): 95 u WHAT WE CLAIM IS: 1. A method of reinforcing and stabilising soil comprising incorporating therein at least one fabric layer constituted by a warp knitted fabric having high tenacity, synthetic polymeric, continuous filament yarns inlaid in the warp direction.

2. A method according to claim 1, wherein said fabric has said high tenacity yarns inlaid in both the warp and weft directions.

3. A method according to claim 1, wherein several layers of said fabric are positioned above one another and parallel to ground level in a soil embankment.

4. A method according to claim 1, comprising anchoring a retaining wall behind which soil is built up by building up the soil in layers between layers of said fabric affixed at one end thereof to the wall.

5. A method according to any preceding claim wherein, the warp knitted fabric is formed from yarns knitted together which form the structure into which the high tenacity yarns are in-laid, said knitted yarns having a tenacity lower than that of the inlaid yarns.

6. A method according to claim 5, wherein the knitted yarns have a tenacity per filament of less than 4.5 g/decitex.

7. A method according to claim 5, wherein the inlaid yarns have a tenacity per filament of at least 6 g/decitex.

8. A method of reinforcing and stabilising soil according to claim 1, incorporating at least one layer of fabric substantially as hereinbefore described with reference to the Example.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. Machine: Mayer Raschel; 20 gauge. Yarns: (a) 167 decitex 30 filament bulked poly ester yarn; filament tenacity 3.5 g/ decitex. (b) 110 decitex, 96 filament flat poly ester yarn twisted to 100 turns/metre; filament tenacity 7.5 g/decitex. Knitting Notation: Front bar: full set; yarn (a) knitting

1-0/2-3 Middle bar: full set; yarn (b) knitting 0-0/1 - 1/0-0/2-2 Back bar: full set; yarn (b) knitting yarns (b) were inlaid at 17 per cm.

Fabric Properties: Weight: 309 g/sq metre Strength in Warp Direction (da N): 603 (5 cm wide fabric strip) Strength in Weft Direction (da N): 184 (5 cm wide fabric strip) Extensibility (warp direction): 15% Extensibility (weft direction): 84% Pore size distribution (0,): 95 u WHAT WE CLAIM IS: 1. A method of reinforcing and stabilising soil comprising incorporating therein at least one fabric layer constituted by a warp knitted fabric having high tenacity, synthetic polymeric, continuous filament yarns inlaid in the warp direction.

2. A method according to claim 1, wherein said fabric has said high tenacity yarns inlaid in both the warp and weft directions.

3. A method according to claim 1, wherein several layers of said fabric are positioned above one another and parallel to ground level in a soil embankment.

4. A method according to claim 1, comprising anchoring a retaining wall behind which soil is built up by building up the soil in layers between layers of said fabric affixed at one end thereof to the wall.

5. A method according to any preceding claim wherein, the warp knitted fabric is formed from yarns knitted together which form the structure into which the high tenacity yarns are in-laid, said knitted yarns having a tenacity lower than that of the inlaid yarns.

6. A method according to claim 5, wherein the knitted yarns have a tenacity per filament of less than 4.5 g/decitex.

7. A method according to claim 5, wherein the inlaid yarns have a tenacity per filament of at least 6 g/decitex.

8. A method of reinforcing and stabilising soil according to claim 1, incorporating at least one layer of fabric substantially as hereinbefore described with reference to the Example.