GB2383070A

GB2383070A - Gravity wall made of expanded polystyrene blocks

Info

Publication number: GB2383070A
Application number: GB0228790A
Authority: GB
Inventors: Robert John Legon
Original assignee: VENCEL RESIL Ltd
Current assignee: VENCEL RESIL Ltd
Priority date: 2001-12-12
Filing date: 2002-12-10
Publication date: 2003-06-18
Anticipated expiration: 2022-12-10
Also published as: GB0129718D0; GB2383070B; GB0228790D0

Abstract

A gravity wall (1) for forming embankments and retaining material (2) is constructed from expanded polystyrene blocks, where the blocks may be mechanically connected together. The downward component of thrust from the retained material (2) prevents the wall (1) from sliding outwards and a retaining ridge of denser material (32) may be located at the front foot of the wall (1). The front face (12) of the wall may slope backwards or extend vertically and be covered by a vandalism resistant material. Corner blocks (30, fig 2) allow the direction of the wall to be altered. The slope engaging face (116) of the wall (100) may have a first shallower slope (116A) in the lower portion of the wall (100) and a second steeper slope (116B) in the upper portion of the wall (100). Various relative dimensions of the wall (1) components and features are disclosed.

Description

Retaining Walls This invention relates to retaining walls for earth or other matter tending to shift laterally under its own weight.

Retaining walls of brick or masonry have, of course, long been known and, in particular, so-called gravity walls using the mass of the retaining wall to provide resistance to earth pressure are well known. Gravity walls rely on the downward force created by gravity to prevent the wall from slipping forwards under the pressure of the earth or other matter behind it. Part of this downward force is derived from the mass of earth acting on a sloping rear face of the gravity wall. Such traditional retaining walls, however, take a long time to construct and require much labour.

More recently, attempts have been made to use modern materials in the construction of retaining walls, one example being the use of expanded polystyrene.

Expanded polystyrene has been used to relieve stress on a traditional retaining wall by filling a space between a bank of earth at a natural angle of repose and the retaining wall with the expanded polystyrene.

Substantial time and labour are, however, still needed to construct the retaining wall and a large quantity of expanded polystyrene is needed to obtain good results.

As disclosed in patent specification WO 90/15909, expanded polystyrene has been used as formwork for making a building foundation. In the practical use of such formwork, surrounding earth is in contact with the outside of the formwork and the inside of the formwork is filled with a matrix of reinforcement rods for the concrete to be formed. Such an arrangement, requires, however, a substantial amount of labour for the careful setting up of the formwork and reinforcing rods.

As disclosed in patent specification WO 97/39195, the use of spaced-apart blocks of expanded polystyrene is known for providing the core of an earth embankment carrying a road. The use of the spaced-apart blocks is proposed as a solution to the problem of the high cost of the blocks previously used. The creation of a matrix of spaced-apart blocks is, however, somewhat complex.

Thus, the employment of expanded polystyrene is well known in conjunction with earth but is associated with problems of cost and/or labour and/or complexity.

It is an object of the invention to provide a way of using expanded polystyrene in making a retaining wall so that the overall construction is simple and relatively inexpensive to produce.

The present invention provides a retaining wall for earth or other material, wherein the wall is a gravity wall and the material constituting the gravity wall is

expanded polystyrene. Surprisingly, expanded polystyrene, in spite of its great lightness, is able to function as the material of the gravity wall itself rather than merely as a filler material between earth and the gravity wall proper. Surprisingly, one can make a gravity wall of expanded polystyrene which does not slip under the pressure of earth in direct contact with it even though gravity walls previously used very massive materials to resist the lateral pressure of the earth.

Very little labour and time are required to make such a retaining wall because the massive materials of a traditional gravity wall are replaced by expanded polystyrene which can be handled with ease in large prefabricated blocks.

A plurality of blocks could be joined together to make up the height and depth of the wall but advantageously, the wall comprises adjacent blocks of expanded polystyrene each of dimensions corresponding to the full height and depth of the wall. By this means, the wall can be constructed rapidly because each block corresponds to a complete section of wall.

The adjacent blocks of expanded polystyrene may be mechanically connected together, for example, adjacent blocks may be mechanically connected together at the top by means of links.

Preferably, the wall is generally triangular in section and has a substrate-engaging face, a front face rising approximately at right angles from the substrateengaging face, and a sloping earth-engagement face forming the back of the wall. Such a construction is particularly simple. The faces corresponding to the sides of the triangle may be plain and flat or may include surface shaping (for example, for aesthetic reasons) and/or one or more concave or convex curves.

Advantageously, the sloping earth-engagement face has a first, shallower slope in the lower portion of the wall, and a second, steeper slope in the upper portion of the wall. Such a construction can provide greater stability during the preliminary stages of building the wall.

Preferably, the first, shallower slope and the second, steeper slope are respectively defined by faces of auxiliary and main blocks of general triangular section which abut one other. By this means, constraints on the size of blocks which it is practical to manufacture can be circumvented.

Preferably, the first, shallower slope is defined by an auxiliary block having a substrate-engaging face, a sloping earth-engagement face corresponding to the said first, shallower slope, and a main block engagement face

having a slope corresponding to the said second, steeper slope.

Advantageously, the triangular shape is truncated at one or both of the top and rear of the wall by flat sections of length corresponding to one twentieth or more of the height of the wall. By this means, fragile points can be avoided both at the top and foot of the wall and a flat top given to the wall.

Preferably, the depth of the wall at its foot is greater than half the height of the wall. By this means, a suitably large angle for the rear side can be achieved.

The width of a block may be substantially one half of its depth. This provides a good practical arrangement.

The front face may slope backwards from the foot of the wall, for example, at 5 or less.

Instead, the front face may rise substantially vertically from the foot of the wall.

The wall may be made up of prismatic blocks of expanded polystyrene. By this means, a straight wall of constant height is easily made.

Advantageously, a retaining ridge of a denser material, for example, timber or concrete, is located at the foot of the wall at the front thereof. Such a retaining ridge is not essential in all cases but can be useful as a supplementary measure to prevent the

retaining wall from sliding forward. Instead, the retaining ridge can be provided to allow an economy to be made in the area of the wall in contact with the substrate so permitting a saving in the amount of expanded polystyrene used.

The height of the wall may be greater than 1.5 metres, for example, two metres or more.

The wall may include one or more corner blocks to change the direction of the wall as seen in plan.

The front of the wall may be protected by a layer of vandalism-resisting material, for example, a layer of concrete or a cladding of sheet iron.

A retaining wall constructed in accordance with the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a cross-section through the retaining wall; Figure 2 is a plan view of the retaining wall showing the wall turning through a right angle; Figure 3 is a cut-away perspective view showing how a pair of adjacent blocks in a straight-line section of the wall are joined by means of a link;

Figure 4 is a perspective view of a link for use at a corner; Figure 5 is a cut-away cross-section showing a timber ridge at the foot of the wall; Figures 6a to 6j show a variety of alternative cross-sections for the retaining wall; and Figure 7 is a cross-section through a modified for of the retaining wall.

Referring to the accompanying drawings, a retaining wall 1 for earth 2 or other material is shown. The wall 1 is a gravity wall and the material constituting the gravity wall is expanded polystyrene 3.

The wall 1 comprises adjacent blocks 4 of expanded polystyrene each of dimensions corresponding to the full height h and depth d of the wall.

The adjacent blocks 4 of expanded polystyrene are, as shown in Figure 3, mechanically connected together at the top by means of links 5 of wood or metal inserted tightly in corresponding slots in the expanded polystyrene.

The wall 1 is generally triangular in section and has a substrate-engaging face 10, a front face 12 rising

substantially at right angles from the substrate-engaging face 10 forming the front 14 of the wall, and a sloping earth-engagement face 16 forming the back of the wall 18.

The triangular shape is truncated at the top 20 and rear of the wall by flat sections 22 of length 1. The depth of the wall d at its foot is greater than half the height h of the wall.

Alternatively, the front face 12 forming the front 14 of the wall can slope backwards from the foot of the wall, for example, at 5 or less.

Other than at corners, where corner pieces 30 are used, the wall is made up of wedge shaped prismatic blocks of expanded polystyrene. That is, the sides of the blocks are similar, equal and parallel rectilineal figures of wedge shape and the other faces are parallelograms.

As shown, but optionally, a retaining ridge 32 of a denser material is located at the foot of the wall at the front 14 thereof. As shown in Figure 5, the retaining ridge 32 comprises for example, a square section piece of timber anchored to the substrate by bolts 34.

As already mentioned, the wall 1 includes one or more corner blocks 30 to change the direction of the wall as seen in plan in Figure 2. The corner blocks 30 are each made up of two blocks 36 and 36'secured to each other by a link, or corner brace, 38 comprising two

pieces of galvanized metal bent at right angles (Figure 4) and inserted tightly into slots at the top of the blocks 36 and 36'.

The blocks 36 and 36'are triangular in plan and each can be made by securing a pair of the wedge-shaped prismatic blocks (used in the straight-line sections of the wall) together adhesively and cutting them across diagonally. As that operation, yields two pieces of like hand, it has, of course, to be repeated with another pair of adhesively secured blocks whilst cutting along the other diagonal to obtain two pieces of opposite hand. By combining a piece of one hand with a piece of the other hand, a corner piece comprising the blocks 36 and 36'is achieved. If desired, a corner piece could be formed integrally instead of making it up by cutting the wedgeshaped prismatic blocks.

If desired, the front 14 of the wall 1 can be protected by a layer of vandalism-resisting material 40 such as concrete or sheet iron.

In a practical example of the wall 1, the height h was 2000 millimetres, the depth d 1200 millimetres, the length 1 200 millimetres and the blocks making up the straight-line sections of the wall were 600 millimetres wide. The blocks were of medium density expanded polystyrene and the restraining ridge was of timber of 100 x 100 millimetres section.

In erecting the retaining wall to retain a bank of earth or other material, a level substrate is prepared in front of the bank of earth to be retained, the earth of the bank being at its natural angle of repose. The substrate can simply be the ground in front of the bank or a layer of concrete or other material can be provided in front of the bank. The expanded polystyrene blocks constituting the wall are now placed in position and joined to each other by means of the links. Some temporary restraint of any suitable form and/or the optional ridge 32 are now applied to the blocks and the earth of the bank shifted using, for example, a bulldozer so as to lie against the sloping earth-engagement face 16 of the blocks. The earth lying against the face 16 provides, by gravity, a force component pushing the block down against the substrate and the temporary restraint can now be removed. A vandal-resistant layer on the front face of the wall can now be applied if desired.

The wall relies on its geometry to resist the main forces applied to it and the sloping rear face engaging with the retained face generates a downward force component that provides the wall with its ability to resist overturning and sliding forces. The depth of the wall is greater at the foot of the wall than at the top.

Typically the ratio of the depth of the wall to its height is between 0.4 to 1.0 and 1.25 to 1. 0, for

example, the ratio can be between 0.5 to 1.0 and 0.9 to 1.0, or between 0.6 to 1.0 and 0.8 to 1.0.

It is to be understood that the geometry of the blocks and, in particular, the slope of the earthengagement face is chosen so that the blocks do not slide or topple forward under the action of the earth or other material behind the wall. A suitable safety factor is, of course, included. Suitable geometry may be determined by simple experiment or by application of the calculations used for the previously known gravity walls.

Various examples of alternative cross-sections for the retaining wall are shown in Figures 6a to 6j. Figure 6a corresponds to Figure 1, Figure 6b shows the continuous slope of the earth-engagement face of Figure 6a replaced by a stepped face, Figure 6c shows the combination of a backward-sloping front face with a sloping substrate-engaging face rising towards the front of the wall, Figure 6d shows the use of front face which provides a strong backwards slope, Figure 6e shows a combination of the features of Figures 6b and 6d, Figure 6f shows an inclined top edge combined with a vertical front face, Figure 6g shows a small variation on Figure 6c, Figure 6h shows the use of a stepped front face, Figure 6i shows a variation on Figure 6d and Figure 6j shows a combination of the features of Figures 6h and 6i.

A construction will now be described with reference to Figure 7 for use when greater stability is considered necessary during the preliminary stages of erecting the wall. Figure 7 shows a retaining wall 100, wherein a sloping earth-engagement face 116 has a first, shallower slope 116A in the lower portion of the wall, and a second, steeper slope 116B in the upper portion of the wall. The first, shallower slope 116A and the second, steeper slope 116B are respectively defined by faces of an auxiliary block 120 and a main block 122, each of general triangular section, which abut one other. The first, shallower slope 116A is defined by the auxiliary block 120 which has a substrate-engaging face 130, a sloping earth-engagement face 132 corresponding to the said first, shallower slope 116A, and a main block engagement face 134 having a slope corresponding to the said second, steeper slope 116B. The main and auxiliary blocks abut each other but need not be mechanically secured to each other.

A retaining wall according to the invention can be constructed of one monolithic block of polystyrene or can be made up of several components. As an aid to alignment and/or load sharing, these components can be held together by friction or can be adhesively secured or mechanically fixed.

As already mentioned, fragile corners to the expanded polystyrene are preferably avoided to aid robustness.

A retaining wall according to the invention can be erected directly upon an existing slab, on natural soil, a prepared substrate or a concrete footing.

The front foot of the wall can with advantage be located below the level of the surrounding ground or another form of temporary or permanent restraint can be provided.

Curved walls can be formed by aligning parallel sided blocks on a radius or specially shaped blocks can be used.

External corners can be formed by adjacent blocks which simply overlap one another.

Internal corners can be provided in the retaining wall if desired, in particular, blocks which interface with the retained material in two directions can be used.

Corner blocks can be formed from a monolithic block of polystyrene or built up from several smaller pieces that can be held together by friction, adhesively secured or mechanically fixed together.

The wall faces can be protected by cladding in metal, concrete, masonry, timber, plastics material or other suitable material.

Claims

CLAIMS :

1. A retaining wall for earth or other material, wherein the wall is a gravity wall and the material constituting the gravity wall is expanded polystyrene.

2. A retaining wall as claimed in claim 1, wherein the wall comprises adjacent blocks of expanded polystyrene each of dimensions corresponding to the full height and depth of the wall.

3. A retaining wall as claimed in claim 2, wherein the adjacent blocks of expanded polystyrene are mechanically connected together.

4. A retaining wall as claimed in claim 3, wherein adjacent blocks are mechanically connected together at the top by means of links.

5. A retaining wall as claimed in any preceding claim, wherein the wall is generally triangular in section and has a substrate-engaging face, a front face rising approximately at right angles from the substrateengaging face, and a sloping earth-engagement face forming the back of the wall.

6. A retaining wall as claimed in claim 5, wherein the sloping earth-engagement face has a first, shallower slope in the lower portion of the wall, and a second, steeper slope in the upper portion of the wall.

7. A retaining wall as claimed in claim 6, wherein the first, shallower slope and the second, steeper slope are respectively defined by faces of auxiliary and main blocks of general triangular section which abut one other.

8. A retaining wall as claimed in claim 7, wherein the first, shallower slope is defined by an auxiliary block having a substrate-engaging face, a sloping earthengagement face corresponding to the said first, shallower slope, and a main block engagement face having a slope corresponding to the said second, steeper slope.

9. A retaining wall as claimed in any of claims 5 to 8, wherein the triangular shape is truncated at one or both of the top and rear of the wall by flat sections of length corresponding to one twentieth or more of the height of the wall.

10. A retaining wall as claimed in any of claims 5 to 9, wherein the depth of the wall at its foot is greater than half the height of the wall.

11. A retaining wall as claimed in claim 2 or any of claims 3 to 10 when dependent on claim 2, wherein the width of a block is substantially one half of its depth.

12. A retaining wall as claimed in any of claims 5 to 11, wherein the front face slopes backwards from the foot of the wall.

13. A retaining wall as claimed in claim 12, wherein the front face slopes backwards at 5 or less.

14. A retaining wall as claimed in any of claims 5 to 12, wherein the front face rises substantially vertically from the foot of the wall.

15. A retaining wall as claimed in any of claims 5 to 14, wherein the wall is made up of prismatic blocks of expanded polystyrene.

16. A retaining wall as claimed in any preceding claim, wherein a retaining ridge of a denser material is located at the foot of the wall at the front thereof.

17. A retaining wall as claimed in any preceding claim, wherein the height of the wall is greater than 1.5 metres.

18. A retaining wall as claimed in any preceding claim, wherein the wall includes one or more corner blocks to change the direction of the wall as seen in plan.

19. A retaining wall as claimed in any preceding claim, wherein the front of the wall is protected by a layer of vandalism-resisting material.

20. A retaining wall substantially as herein described with reference to, and as illustrated by, the accompanying drawings.