GB2199603A - Anchored soil structure - Google Patents

Abstract

A structure, eg. an earth retaining wall, has a facing (4) which is held in place by tension members (11, 14) which in turn are connected to an anchor (9) or the anchors (9, 12, 13) formed from substantially linear elements which are laid in the fill (1) during construction. The anchors can be formed from a variety of materials, eg. steel rebar or plastic tubes, and can be of a range of sizes. The anchors are placed in the fill in any convenient orientation, eg. horizontally, vertically or inclined. <IMAGE>

Description

Anchored Soil Structure Background of the Invention The present invention relates to strengthening Cwhich can include stabilising or reinforcing) geotechnical structures made from cohesive or cohesionless soils or a combination of both or waste materials. The soil may be, for instance, earth, sand, clay, gravel, chalk, minestone, pulverised fuel ash, slag or any bulk material. The invetion is particularly applicable to constructing the sides of a cutting or embankment and in the repair of earthworks.

The invention can be applied to any suitable location, for instance to a marine wall such as a quay, a dam, a storage bunker, an unstable slope in a mountainous area, or a wall to contain explosions. The invention is especially suitable for constructing retaining walls and bridge abutments, the construction of embankments on weak soils or steepening embankments or a combination of any of these.

The technique of anchored soil construction involves the embedding of stabilising members into an earth mass to give the mass a required degree of stability in tension, in addition to the natural stability in compression of the mass. The type of stabilising member used and the number and disposition of the members for a particular geotechnical structure depends upon the size of the structure and the characteristics of the soil.

In many cases where an anchored soil structure is produced it is necessary or desirable to provide a facing for an exposed lateral surface of the structure in order to prevent erosion of the surface and also to present a pleasing appearance.

The Invention The first aspect of the invention concerns itself with the problem of providing an anchored soil structure which has a facing made of a number of units which may be rigid or flexible built one on top of another or provided as a single height unit. Reinforced soil structures having various forms of facings are described in British Patent Specification No.s 1,069,361; 1,324,686 and 1,485,004.

The invention provides an anchored soil structure comprising a soil mass, a facing unit or units extending up a lateral surface of the soil mass, an anchoring member embedded in the soil mass and connected to the facing unit by a tension member laid substantially horizontally.

The invention also provides a method of forming an anchored soil structure comprising erecting a facing to extend upwards from a foundation, inserting a prop or temporary clamping arrangement so as to support the facing substantially in an upright position, laying a first layer of soil behind the facing positioning an anchor member on the first layer, securing the anchor member to the facing by a tension member, laying a second layer of soil fill over the anchor and the tension member and removing the temporary prop or temporary clamp.

In a preferred embodiment of the invention å plurability of anchors are secured to the facing by a plurality of tension members, the anchors being spaced apart long the height of the facing. The method further comprises positioning a second anchor member on the second layer and securing it to the facing with a tension member laying a third layer of soil fill, place the next lowermost anchor on the third layer and securing it to the facing, laying further layers of soil fill and anchor members secured to the facing to a required height and topping the soil mass with an uppermost layer of soil fill. It is, of course, desirable that each layer of soil fill be compacted after it is laid and before the next anchor is laid on it.

In another embodiment of the invention the anchor members are placed in a substantially vertical or inclined position positioned behind the facing. A plurality of anchors may be used in any plane, the anchors being connected to the facing by tension members after each layer of soil has been placed. The anchors may extend the full height of the structure or be of limited length.

Where a substantially vertical anchor is used it is desirable for the tensioning member connecting the anchor to the facing to be attached in such a manner so as to permit the tension member to move substantially vertically throughout its length. This may-be achieved by having the tension member attached by means of slideable connections.

In a third embodiment of the invention no facing is required.

In this case anchors on any subtantially horizontal plane are secured to each other by a plurality of tension members. The method further comprises positioning a second layer of anchor members on a second layer and connecting them to each other by tension members, laying a third layer of soil fill, placing the next lowermost anchor members and connecting with tension members, laying further layers of soil fill and anchor members -to a required height and topping the soil mass with an uppermost layer of soil fill.

In another embodiment of the invention the anchor members may be placed in a substantially vertical or inclined position. A plurality of anchors may be used, the anchors being connected to the facing by tensioning members after each layer of soil has been placed. Where a substantially vertical anchor is used it is desirable for the tensioning member connecting the anchor to the facing to be attached with a slideable connection.

Embodiments of the invention will now be described with reference to the accompanying diagramatic drawings of which Figure 1 is a general prospective view of a retaining wall made up of facing units.

Figures 2 - 8 inclusive are side elevations showing the formation of anchored soil structures.

Figure 9 is a plan view of a retaining wall with an anchor placed horizontally substantially parallel with the facing.

Figure 10 is a plan view of a retaining wall with anchors placed vertically.

Figures 11, 12 and 12a are views of tension members passing round an anchor member. When the anchor member is in a substantially vertical plane this connection permits the tension member to slide.

Figure 13 is an enlarged cross-section on the line X-X in figure 9 showing the details of a coupling arrangement between the facing and a tension member in which the tension member can slide in a vertical direction.

Figure 14 is a side elevation of an anchored soil structure.

Figure 15 is a side elevation of an anchored soil structure formed using a plurality of anchors.

Figure 16 is a side elevation of an anchored soil structure formed using anchors laid horizontally and vertically.

Figure 17 is a side elevation of an anchored soil structure formed using inclined and vertical anchors.

Referring to Figure 1, an anchored soil structure comprises a soil mass C1) having two retaining walls C2 and 3) each made up of a plurality of individual facings C4). For the sake of illustration one of the units 641 is removed from its normal position in the retaining wall. All the facings are supported upon a foundation (5) below the level of the surrounding ground (6).

Figure 2 illustrates the method of construction of the anchored soil structure shown in t1). Initially a trench is cut in the ground and concrete poured in to form the foundation cos). The facing (4), formed in one unit or built from sections is placed on the foundation and held substantially vertically. Soil C1) is laid horizontally and compacted to the level of the lowest anchor (9) which coincides with the connection to the facing (10). Anchor (9) is laid on the soil and connected to the facing by tension member (11). Another layer of soil is placed and compacted to the next lowest anchor (12) and the process repeated. When top anchor (13) has been placed and tension member (8a) installed, soil is laid to the final level (15), support to the facing is removed when convenient.

The method of construction of the wall illustrated in figure 3 is similar to the method used for the wall illustrated in figure 2.

Figures 4, 5, 6 and 6a illustrate the method of construction where vertical anchors are used. A trench is cut in the ground and the concrete is placed. The facing is placed on the foundation and held substantially vertically, soil is placed and compacted to the level of the lowest tension member (16) which coincides with the lowest connection point on the facing (17). The anchor (18) is forced into the compacted soil so as to be substantially vertical, alternatively the anchor (18) may be held in place as the initial layer of soil is placed. The tension member is placed to connect the anchor to the facing. Another layer of soil is laid and compacted up to the next lowest tension member (19), the soil being compacted around the anchor (18). When convenient the support of the facing is removed.

Other layers of soil are laid and the procedure repeated until the top tension member (20) has been fixed, soil is laid to the final level (21).

Figures 7 and 8 illustrate the method of construction where inclined anchors are used, the procedure for construction is similar to that in figures 5 and 6.

Figures 9 illustrate a method of connecting an anchor (22) laid substantially horizontally to the facing (4) by means of a tension member (23). The anchor (23) is laid on the compacted soil and the tension member passed back and forward between the connection position (24) on the facing in a manner similar to a lacing. The next layer of soil is placed on top of the anchor and the tension member. The tension member if formed from a pliant material should preferrably be taut.

Figure 10 illustrates a similar method to that used in figure 9 except that in this case the anchors (25) are embedded substantially vertically in the soil, and connected to the facing (26) by the tension member (27) at connections (28). Figure 11 is an enlarged illustration of the connection A in figure 10, between the anchor 22) and the tension member (23). The anchor (22)in this illustration is formed by placing a reinforcing bar (24) inside a-tube (25) and filling the void with concrete (26).

Figure 12 and 12a illustrate how a plurality of anchors (27) may be connected to tension members (28).

Figure 14 illustrates the method of construction of an anchored soil structure in the form of an embankment. Initially the anchor members C29) are placed on the. ground parallel but inside to the toe of the proposed embodiment. The anchors at opposite sides of the embankment are connected by tension member (30) , soil is placed over the anchors and tension members and compacted to the level of the next lowest anchor, anchors (31) are placed on the soil with tension number (32) connected. The process is continued until the top layer of anchors (33) and tension connectors (34) are placed.

Additional soil is placed to a final level (35).

Figure 15 illustrates a similar construction method except that a plurality of anchors is used at each side of the embankment.

Figure 16 illustrates a method of construction which combines horizontal anchors (36) with a vertical anchor (18), the tension member (15) is connected to the anchor (37) with a slideable connection.

Figure 17 illustrates a method of constructing an anchored soil structure using substantially vertical (38) and included anchors (39) connected with tension members (40). Initially the anchor members are held at the correct inclination or vertically and the first tension member (40) arranged to hold the anchors in place. Soil is placed on top of the tension member and compacted to the level of the next lowest tension member (41). Tension member (41) is placed to connect the anchors, additional soil is placed and compacted to the next level of tension member, the process is repeated until the top tension member (422 is placed connecting the anchors (.38) and (39) , more soil is placed to a final level (43).

Various materials and forms of materials may be used for the anchors, including tubes, bars or shaped sections made of metal, polymers, glass or wood. The tension members can be in the form of wire, tape, chains, rods, bars, sheet material, grids, planks, rope formed from metal, glass, polymers or vegetable matter.

Claims (9)

1. A wall, embankment or earth structure including foundations formed using anchor elements held in place by tension members, the anchors are made up of bars, tubes or composite shapes laid horizontally, vertically or inclined in the soil or waste fill material.

2. A wall, embankment or earth structure, as in Claim 1, which uses a purality of anchor members laid separately or connected together.

3. A wall, embankment or earth structure, as in Claim 2, which is formed of anchor members made of metal, glass, vegetable matter, polymers or concrete.

4. A wall, embankment or earth structure, as in Claim 3, in which the anchors are connected together by tapes, chains, rope, bars, sheet material, grids, planks formed from metal, glass, ploymers or vegetable matter.

5. A wall, embankment or earth structure, as in Claim 4, which has a vertical face made up of full sized elements, incremented units or composite facings.

6. A wall, embankment or earth structure, as in Claim 5, which has facings which may be rigid or flexible.

7. An embankment or earth structure, as in Claim 4, which is formed without a facing.

8. A wall, embankment or earth structure, as in Claim 6, which is made of anchors placed horizontally, inclined or vertically.

9. A wall, embankment or earth structure substantially as described herein with reference to Figures 1-17 of the accompanying drawings.