GB2073281A

GB2073281A - Reinforced soil structure

Info

Publication number: GB2073281A
Application number: GB7941627A
Authority: GB
Original assignee: Netlon Ltd
Current assignee: Netlon Ltd
Priority date: 1979-12-03
Filing date: 1979-12-03
Publication date: 1981-10-14

Abstract

In order to construct a retaining wall and prevent it being forced out of position by the pressure of material behind it, parallel lengths of plastics material mesh structure 7 are laid in soil 1 and the end portions of the lengths 1 are bent up in order to form at least the outer sides 5 of gabions 2. <IMAGE>

Description

SPECIFICATION Reinforced soil structure Background of the Invention The present invention relates to strengthening (which can include stabilising or reinforcing) geotechnical structures made from cohesive or cohesionless soils or a combination of both, though the invention is more suitable for cohesionless materials. The soil may be for instance earth, sand, clay, gravel, minestone, pulverised fuel, ash, slag, or any bulk material. The invention is particularly applicable to constructing the sides of a cutting or embankment, but the invention can be applied in any suitable location, for instance to a marine wall such as a quay, a dam, a storage bunker, a mine dump, an unstable slope in a mountainous area, or a wall to contain explosions.The invention is especially suitable for constructing retaining walls and preventing them being forced out of position by the pressure of material behind them.

The Invention A first aspect of the invention provides a method of retaining soils, comprising laying parallel lengths of plastics material mesh structure and forming at least the bases and outer sides of gabions from the lengths themselves by bending up the end portions of the lengths.

According to another aspect, the present invention provides an engineering construction comprising a retaining wall of gabions, and lengths of mesh structure extending from the gabions into the mass of soil, the ends of the lengths being bent up so that their end portions form at least the bases and outer sides of the gabions. Thus the soil reinforcing layer or length and at least the fact of the gabion, and preferably the top as well, are formed of one integral length of mesh structure.

The word "gabion" is used generally herein to mean a container of mesh structure containing pieces of material such as broken rock, stones or pebble (or any other suitable material) at least most of which is sufficiently large to prevent it passing through the meshes of the gabion. Though the gabions may be of roughly the same height as their width, they are preferably much wider than they are high, being of a form commonly called "mattresses". The principal dimensions of a gabion are the height, width and length, the latter two being taken normal to, and parallel to, the exposed face, respectively.

In general, the lengths of mesh structure are preferably laid horizontally, and there can be a plurality of layers of the mesh structure with a substantial vertical spacing between the layers.

In general, the mesh structure preferably has molecularly oriented strands extending along the lengths of the mesh structure, but this is not essential. The mesh structure is preferably a uniaxially-stretched or biaxially-stretched structure produced by stretching a sheet formed with holes or depressions so as to stretch zones between the holes or depressions into molecularly-oriented strands, the preferred structures being of the type described in British patent application number 7934944. However, the mesh structures could alternatively be integrally-extruded monoplanar or biplanar meshes, for instance formed by the process described in British patent specification number 1 250 478, possibly with subsequent machine direction stretching of the mesh structure.

The invention provides a cheap method which is quick and simple to adopt. It is also a practicai method of constructing a reinforced soil structure where access to the face of the retaining wall is very limited, e.g. for marine walls, river work protection or steep mountain slopes.

Description of Preferred Embodiments Figures 1 to 3 are vertical sections through three different embankment structures in accordance with the invention.

The three structures are similar, the main differences being that that of Figure 1 has a stepped outer face, that of Figure 2 has a sloping outer face and that of Figure 3 has a vertical outer face.

In each of the structures, a soil mass 1 is retained by gabions 2 which are filled with broken rock or other suitable material 3. The base 4, the outer side 5 and the top 6 of each gabion 2 are formed by bending up and back the end portion of a respective length 7 of plastics material mesh structure which extends from the gabion 3 into the mass 1 of the soil. The plastics material mesh structure may be for instance the uniaxiallystretched structure which is described with reference to Figure 2 and in Example 1 of the British Patent application referred to above. The lengths 7 extend as far as necessary into the mass 1, according to normal design criteria, for instance beyond the slip circle.The lengths 7 may have any suitable width, for instance 50 cm to 1, 2 or 3 metres and are preferably laid with their edges nearly in contact, though it is not believed necessary to attach the edges to one another. The vertical spacing between the lengths 7 may be for instance 30 or 50 to 100 cms or as determined by normal design criteria.

The gabions 2 have separate rear walls 8, held in any suitable manner, for instance with metal clips, wire or braid, or spiral retainers (not shown), and have separate side walls (not shown) at suitable intervals, not necessarily between every two lengths 77. Adjacent gabions 2 at the same lever can be held together by for instance metal clips, wire or braid, or spiral retainers, particularly to prevent loss of rock pieces if there is no side wall at that location. As an example, the gabions 2 may be 1 metre wide.

In order to make the construction, the first layer of lengths 7 is laid, the end portions are bent up to form the outer sides 5 of the gabions, the rear walls 8 are supported in position, the gabions 2 are filled with the broken rock or other suitable material 3 and the tops 6 are bent over and fixed closed, for instance with metal clips, wire or braid, or spiral retainers (not shown). The mass 1 of soil is then placed in position and compacted so that it is compacted into the mesh openings of the lengths 7. The mass 1 is roughly levelled off at the height of the top of the first gabions 2, and the procedure is then repeated.

Claims

1. A method of retaining soils, comprising laying parallel lengths of plastics material mesh structure and forming at least the bases and outer sides of gabions from the lengths themselves by bending up the end portions of the lengths.

2. The method of Claim 1, wherein the tops of the gabions are also formed from said lengths.

3. The method of Claim 1 or 2, wherein said lengths are laid horizontally (apart from the end portions).

4. The method of any one of the preceding Claims, wherein there is a plurality of layers of the mesh structure with substantial vertical spacing between the layers.

5. The method of Claim 4, wherein the vertical spacing between the layers corresponds to the height of the gabions.

6. The method of any one of the preceding Claims, wherein the mesh structure has molecularly oriented strands extending along the lengths thereof.

7. The method of Claim 6, wherein the mesh structure is a uniaxially-stretched or biaxiallystretched structure produced by stretching a sheet formed with holes or depressions so as to stretch zones between the holes or depressions into molecularly-oriented strands.

8. A method of retaining soils, substantially as herein described with reference to, or as shown in, any one of the Figures of the accompanying drawing.

9. An engineering construction comprising a retaining wall of gabions, and lengths of mesh structure extending from the gabions into the mass of soil, the ends of the lengths being bent up so that their end portions form at least the bases and outer sides of the gabions.

10. The construction of Claim 9, and made by the method of any one of Claims 2 to 7.

11. An engineering construction, substantially as herein described with reference to, and as shown in, any one of the Figures of the accompanying drawing.