Retaining wall and blocks for the formation thereof

A block having at least one front face, at least one back face, sides connecting the front and back faces, a top surface, a bottom surface and at least one cavity passing through the entire height of the block from the top surface to the bottom surface, wherein the cavity is positioned so that the centre of mass of the block lies closer to the back face than does the geometric centre of the block.

FIELD OF THE INVENTION

The present invention relates to a retaining wall and blocks for use in the formation thereof. While the invention is described with reference to a retaining wall, it will be recognised that the structure described is also suitable for use in mass gravity walls, reinforced soil structures, bridge abutments, stream channels, coastal protection systems, sea walls, erosion prevention, tunnel access, wing walls, storage bins and similar applications.

INTERPRETATION

As used herein, the terms “front face” and “back face” are interpreted according to the orientation of a block in ordinary use, the front face being the face which is visible in use. For example, where the blocks are used to form a retaining wall, the “back face” is the side which is against the earth or other substance being retained and the “front face” is the face visible to passers-by.

BACKGROUND

It is known to use stacked blocks to create retaining walls. These blocks may have a tapered shape, so that they can be fitted together in a curve. One popular product is the MASSBLOC® retaining wall system, which utilises tapered blocks with a facetted front profile.

Some models, such as the KEYSTONE® planter unit, contain cavities, which reduce the weight of each block, and can be filled with soil to hold vegetation, improving the aesthetic qualities of the wall. Blocks of this general type are disclosed in U.S. Pat. Nos. 5,601,384, 6,622,445, 6,701,687, and 4,920,712.

One major problem with existing blocks is that the centre of mass is located towards the front of the block, reducing the stability of the retaining wall. The MASSBLOC® retaining wall system comprises two types of blocks—a base block for the bottom layer of a wall, and a standard block that has a lip protruding from the lower back edge of the block, which fits behind the block below to ensure that the blocks on each layer are the same distance back from the layer below. However, this requires the use of two different types of blocks in constructing the retaining wall, with the accompanying inefficiencies and increased costs.

SUMMARY OF INVENTION

An object of the present invention is the provision of an improved block which is designed so that a single block shape can be used for an entire structure. A further object of the present invention is the provision of a block designed to be exceptionally stable when the block is built into a structure.

A block having at least one front face, at least one back face, sides connecting the front and back faces, a top surface, a bottom surface and at least one cavity passing through the entire height of the block from the top surface to the bottom surface, wherein the cavity is positioned so that the centre of mass of the block lies closer to the back face than does the geometric centre of the block.

Preferably the block is tapered from the front to the back, such that the back is narrower than the front, has a flat bottom surface and a lip on the top surface at the front of the block. Preferably, the block has a single, curved front face and the lip on the top surface at the front of the block also is curved, in a reverse curve to the curve of the front face, so that the lip is oval in plan view.

The block may have vertical grooves in each side panel of the block, near the front, adapted to receive a spacer plate between adjacent blocks. The block may also have a groove across the top of the block, which may be fitted with a rod to secure a geotextile.

In addition, the back face of the block and the sides of the back of the block may be formed with horizontal slots for receiving a structural connecting tie. Preferably, the structural connecting tie is designed to provide a strong connection between the upper and lower course of the wall, and further, to provide a tensile connection.

The present invention also provides a structure made from two or more rows of the above described blocks; the structure may be a retaining wall. The rows of blocks may be straight or curved.

In each row of blocks, adjacent blocks may be in contact with each other or may be spaced apart by a predetermined gap; spacer plates may be fitted into grooves in the sides of adjacent blocks to close off the gaps. Spacer plates are particularly useful when the row is curved, since they allow adjacent blocks to be spaced apart sufficiently to achieve the desired shape of the row without leaving unsightly gaps.

The blocks may be fabricated from a porous substance, such as no fines concrete, and the spacer plates are fabricated from a durable substance such as fibre cement sheeting, concrete, fibre glass, plastic or treated timber.

BEST METHOD OF CARRYING OUT THE INVENTION

A preferred embodiment of a block according to the present invention is shown inFIG. 1. A block1has a horizontal cross-section having a back face2, a first side face3with a first vertical groove4and a second side face5with a second vertical groove6and a curved front face7, with a cavity10passing through the entire height of the block.

The vertical grooves4,6are shown as narrow grooves, but may in fact be large cutouts.

The back face2has a width B which is significantly less than the overall width A of the front face7. The front face7is depicted in the drawings as a smooth curve with an approximate radius of 800 mm; the radius of the front face may be varied as required by the selected proportions of the block. Alternatively, the front face could be formed as two or more angled flat faces to give a faceted appearance to the block. This variant is shown inFIG. 1a, which depicts a block with three angled front faces7,8and9.

The cavity10is set towards the front of the block1so that the centre of mass of the block1lies behind its geometric centre. The distance by which the centre of mass of the block is moved back from the geometric centre obviously depends upon both the dimensions and the proportions of the block; for example, for a block of the general proportions shown inFIG. 1, with a depth of 1041 mm, the positioning of the cavity10is such that the centre of mass is moved towards the back of the block relative to the geometric centre by approximately 30 mm. The object of moving the centre of mass towards the rear of the block is to increase the stability of the block when it is built into a structure such as a retaining wall, where the pressure on the blocks falls on the rear faces of the blocks and thus tends to tip the blocks forwards.

The base of the block1is substantially planar. A top groove11is formed across the top of block1adjacent the back face2and parallel to the back face. The block1may be provided with one or more lifting eyes (not shown) to facilitate lifting the block.

A raised lip12is formed on the top of the block, integral with the block. The front edge12a of the lip12follows the curve of the front face7of the block, and the rear edge13of the lip12is formed with a reverse curve. The lip12in use provides a guide for the setback of each row of blocks in a structure, after the first row. It is of course known to provide a protrusion on a block to assist in correct setting of second and subsequent rows of blocks, but the protrusion normally is formed on the underside of the block rather than on the upper surface. Forming the lip on the top of the block means that, in a wall under construction, it is very easy to verify that the second and subsequent rows have been correctly positioned, because the position of each of the second and subsequent rows relative to the lips of the blocks on the underlying row can easily be visually checked.

Curvature to the rear edge13of the lip12provides further advantages, because it results in a small contact area between the front face of the block7and the rear edge13of the lip12. Furthermore, the curved shape of the rear edge13reduces the amount of variation in the setback obtained between subsequent rows of blocks when forming curved rows of blocks. It is even more advantageous if both the rear edge13of the lip12is curved and the front face7is also curved, because this further reduces variation in the point of contact between the two surfaces and results in less variation in the setback obtained for the blocks when formed into subsequent layers of curved rows. Furthermore, the junction between the curved front face12and the rear edge13of the lip allows for a greater versatility in the positioning of the blocks without losing contract between the lip12and the next uppermost row of blocks.

The back face2of the block is formed with a transverse slot30parallel to, and a short distance below, the upper edge of31of the back face. L-shaped slots32,33are formed with one limb of the L on each side face3,5adjacent the back face and the other limb of the L, extending onto the adjacent part of the back face2. The slots32,33are aligned and a short distance above the lower edge34of the back face of the block. The slots30,32,33used to receive securing ties as described below. However, if the block is to be used only for low rise structures (typically three rows or less) then these slots are not required.

The block1may typically have dimensions of greatest width A being 1200 mm, back width B being 650 mm, height C being 1000 mm, depth D being 950 mm and full depth E being 1200 mm.

Blocks1are used to form a retaining wall, as shown inFIG. 2andFIG. 3. The blocks1of the present invention can be used to form a wall which is either curved or substantially straight, or with variable curvature. A first layer of blocks21,22and23is placed directly on a prepared substrate. In a curved wall, such as that shown inFIG. 2, a spacer plate24is fitted into first vertical groove4in block22and second vertical groove6in block21, to fit the space between the blocks. Likewise, a spacer plate25is fitted into first vertical groove4in block23and second vertical groove6in block22. If greater stability is required, the cavity10in each block, and the space29between blocks21and22and spacer plate24and the space29abetween blocks22and23and spacer plate25can be filled with soil, hard fill or concrete.

A second layer of blocks26and27is then placed on top of the first layer of blocks21,22and23in a running bond pattern, i.e. the blocks26,27are offset from the blocks beneath by half a block width. Other patterns such as stack bond may also be used, i.e. one row is placed on top of the other with no lateral offset. The second layer of blocks is placed so that the front face7of block27and the front face7of block26is in contact with the curved surface13of the lip12of block22in the first layer. A spacer plate28is fitted into the first vertical groove4in block27and the second vertical groove6in block26to fit the space between the blocks. This pattern may be repeated for as many layers as desired. The blocks may be locked or bound together horizontally and/or vertically (see below).

To create a straight wall, the blocks1are simply positioned in a straight line. In this configuration, spacer plates are not required, but if it is preferred to space the blocks somewhat further apart, then spacer plates may be used to fill the gaps between the blocks.

If a structure to be made from the blocks1is more than three rows of blocks high, or if a particularly strong structure is required, a tie as shown inFIG. 5may be used to provide a strong tensile connection between adjacent rows of blocks.

The tie40may be made of any suitable material; it is depicted as made from stainless steel plate. The tie40consists of a foot portion41which tapers in height along its length, i.e. the outer end42has a height X which is less than the height Y of the inner end43of the foot. Thus, when the foot portion41is driven into the slot30in the back of one of the blocks, the shape of the foot portion securely wedges the tie tightly into the slot.

The shank44of the tie is formed with a twist45so that the end46of the tie, which lies in a plane parallel to the plane of the foot portion41, extends perpendicular to the foot41, so that the end46can engage in the slot32/33of an adjacent block in the row above, as shown inFIG. 4. As shown in that figure, a row of blocks may be secured to the adjacent row of blocks either by using twisted ties as shown inFIG. 5, which engage individually with a corresponding slot32/33, or by using a straight tie50as shown inFIG. 6, which engages with a bar47engaged between two opposed slots32/33. The straight tie50is the same as the twisted tie time shown inFIG. 5except that the twist45is omitted from the shank44, so that the end46of the tie is aligned with the foot41.

The ties40,50provide an easily used connection between the blocks which also gives a strong tensile connection. It should be noted that the connection formed between the blocks are the ties40,50are designed to allow sufficient movement of the blocks to accommodate the active pressure on a structure such as a retaining wall, from the soil behind the wall:—this active pressure typically applies a lateral and downwards pressure to the back of the wall, causing the wall to rotate forwards.

When they are filled with soil, as described above, cavities10may be used as planter boxes. In the top layer, filled cavities10may be used to secure traffic protection devices, such as guardrails or barriers, lamp posts, hand rails or signs etc.

A bar (not shown) may be fitted into top groove11, and a geotextile is fed around the bar in a loop. The geotextile reinforces the soil which is being retained and holds the wall into the soil. This bar in groove fitting provides sufficient strength to achieve close to the full tensile capacity of the geotextile.

The blocks1can be fabricated from no-fines concrete (concrete in which the fine sandy material is removed). The use of a porous material allows water to drain through the blocks1, reducing the pressure applied to the wall. The spacer plates may be fabricated from fibre cement sheeting.