GB2305201A

GB2305201A - Water defence block

Info

Publication number: GB2305201A
Application number: GB9518792A
Authority: GB
Inventors: Geoffrey Arthur Griffths; Christopher David Davies
Original assignee: Marshalls Mono Ltd
Current assignee: Marshalls Mono Ltd
Priority date: 1995-09-14
Filing date: 1995-09-14
Publication date: 1997-04-02
Anticipated expiration: 2015-09-14
Also published as: GB2305201B; GB9518792D0

Abstract

A water defence block is provided which has at least one opening 3 which links upper and lower surfaces of the block. The properties of the block are such that the block is subject to a downward force when water flows over the upper surface of the block, the downward force being a reaction to water passing over the opening or openings. Because a downward force is applied to the blocks when water flows over the blocks, it is possible to use water defence blocks having a smaller mass than known water defence blocks.

Description

WATER DEFENCE BLOCK This invention relates to a block for defending against the physical action of water particularly, but not limited to, in an estuarine environment and to a method of protecting against the physical action of water particularly, but not limited to, in an estuarine environment.

Previous attempts at reducing effects of the physical impact of water in an estuarine environment have included laying blocks together on the banks of the estuary in a type of paving. Major disadvantages have arisen in the use of these blocks in that they must be extremely heavy to resist the force of the water which tends to lift and dislodge the blocks and so destroy the defence.

It is expensive, time consuming and can be inefficient to lay very massive blocks, which would be needed to overcome the above described disadvantages.

It is an object of the present invention to provide a water defence block which is less massive and cheaper to produce and install than the prior art and thus improve upon the above described disadvantages.

According to one aspect of the present invention, a water defence block has at least one opening which links upper and lower surfaces of the block, which block is subject to a downward force when water flows over the upper surface of the block, the downward force being a reaction to water passing over the opening or openings.

The top surface of the water defence block may have a form which acts to reduce the speed of water flowing over the top thereof.

The top of the water defence block may comprise a sloping surface, shaped such that water flowing over the opening or openings brings about a pressure drop at the base of the block thus tending to suck the block into position. The slope may vary and may slope in different directions.

The slope may have a crest, there being openings adjacent to the crest.

There may be openings on each side of the crest.

The said openings may take the form of cylindrical passages which link a central portion of the top surface of the block with a central portion of the bottom surface of the block.

The top surface of the block may comprise two planar sloping surfaces which slope away from each other.

The top surface may comprise a plurality of the openings which are arranged along either side of the apex formed between the two planar sloping surfaces.

The water defence block may additionally comprise transverse ducts through which a cable may be passed in order to secure at least two blocks together, to facilitate laying several blocks at a time.

The edges of the water defence block may be shaped to interlock with the edges of another water defence block which may be of the same construction.

The blocks may be constructed of concrete.

The invention extends to a mattress of a plurality of blocks which may be attached to one another by means of cables threaded through the transverse ducts.

According to another aspect of the present invention a method of protecting the edges of a water course against the physical action of water includes placing blocks on the edges of a water course, the blocks having at least one opening, which links upper and lower surfaces of the blocks on the area to be protected, the blocks being retained in their correct position by a downward force on the blocks which force is exerted when water flows over the upper surfaces of the blocks, the downward force being a reaction to water being drawn up the openings from beneath the blocks by the action of the water flowing over the top surface of the blocks.

The method may include protecting a large area from the physical action of water with a mattress of said blocks held together with cables threaded through transverse ducts in the blocks.

By way of example, a specific embodiment of the invention will now be described with reference to the accompanying drawings, in which : Figure 1 is a schematic side view of a single water defence block according to the present invention; Figure 2 is a schematic side view of a "mattress" of water defence blocks according to the present invention; and Figure 3 is a schematic side cross-sectional view through a water defence block according to the present invention.

A water defence block as shown in Figure 1 comprises vertical channels 3 located in two rows at either side of the central ridge formed by the two slopes. The vertical channels 3 pass through the block from the top, as seen in Figure 1, to the bottom. The vertical channels 3 are shown in cross-section in Figure 3. Cable ducts 1 pass transversely through the block to its opposite side. The block also has projections 2 to enable a block interlock with adjacent blocks.

In use, the blocks are linked together in a "mattress" as shown in Figure 2. To assemble a mattress the blocks are first laid together so that projections 2 interlock. The two projections 2 at each end of one side of a block receive between them one projection 2 from each of two other blocks.

In this way an offset formation is achieved.

When linked in the above manner, cables (not shown) are passed through the cable ducts 1 to hold the blocks in tight contact and to stop them separating under the action of water.

The mattress is then laid, in this case on the banks of an estuary, though this is not to be taken as a limitation of the use of this specific embodiment of the present invention. When water passes over the mattress of blocks the pressure in the vertical channels 3 will be reduced because of the speed of the water passing over the top of the vertical channels 3. Water passing at speed over the top of the vertical channels 3 will be at a lower pressure than that of water at the bottom of the vertical channels 3 because of its speed. The action is similar to that of an atomiser in which air rushing across the top of a tube suspended in perfume will draw perfume up the tube.

A suction force up the vertical channels 3 from the top thereof results in reduced pressure at the bottom of the vertical channels 3. The reduction in pressure at the base of the channels 3 will result in a force pulling upwards at the bottom of the channels 3. Such upward force will provoke a downward reaction from the block which reaction will increase the apparent weight of the block. The increased apparent weight results in the passing water having to exert a greater force to dislodge the blocks from their position than would be needed in a more massive prior art block.

The above described specific embodiment of the present invention provides a water defence block which resists movement by the action of water to the same extent as a more massive and consequently more expensive block.

A more massive block is not only more expensive to product but also more expensive to put in place.

The blocks may be positioned, for optimum effect, on a revetment slope, for example a slope of 1 in 3.

The blocks may be placed on upward or downward slopes.

The blocks may have any desired size but will usually be less than 1 metre square. They may for example be metre square.

The blocks may have voids or depressions therein to further reduce weight. For example the profile of the underside of the blocks may be relieved rather than flat.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A water defence block having at least one opening which links upper and lower surfaces of the block, which block is subject to a downward force when water flows over the upper surface of the block, the downward force being a reaction to water passing over the opening or openings.

2. A water defence block as claimed in Claim 1, the top surface of the block having a form which acts to reduce the speed of water flowing over the top thereof.

3. A water defence block as claimed in Claim 2, in which the top of the water defence block comprises a sloping surface, shaped such that water flowing over the opening or openings brings about a pressure drop at the base of the block thus tending to suck the block into position.

4. A water defence block as claimed in Claim 3, in which the slope has a crest, there being openings adjacent to the crest.

5. A water defence block as claimed in Claim 4, in which there are openings on each side of the crest.

6. A water defence block as claimed in Claim 4 or Claim 5, in which the said openings take the form of passages which link a central portion of the top surface of the block with a central portion of the bottom surface of the block.

7. A water defence block as claimed in Claim 6, in which the passages are cylindrical.

8. A water defence block, as claimed in any one of the preceding claims, in which the top surface of the block comprises two planar sloping surfaces which slope away from each other.

9. A water defence block as claimed in Claim 8, in which the top surface comprises a plurality of openings which are arranged along either side of the apex formed between the two planar sloping surfaces.

10. A water defence block as claimed in any one of the preceding claims, comprising transverse ducts through which a cable may be passed in order to secure at least two blocks together, to facilitate laying several blocks at a time.

11. A water defence block as claimed in any one of the preceding claims in which the edges of the water defence block are shaped to interlock with the edges of another water defence block of the same construction.

12. A water defence block as claimed in any one of the preceding claims, constructed of concrete.

13. A water defence block constructed and arranged substantially as herein described, with reference to Figures 1 and 3 of the accompanying drawings.

14. A plurality of water defence blocks as claimed in any one of the preceding claims, attached to one another to form a mattress of blocks.

15. A mattress of blocks constructed and arranged substantially as herein described, with reference to Figure 2 of the accompanying drawings.

16. A method of protecting the edges of a water course against the physical action of water comprising placing blocks on the edges of a water course, the blocks having at least one opening, which links upper and lower surfaces of the blocks on the area to be protected, the blocks being retained in their correct position by a downward force on the blocks which force is exerted when water flows over the upper surfaces of the blocks, the downward force being a reaction to water being drawn up the openings, from beneath the blocks by the action of the water flowing over the top surface of the blocks.

17. A method of protecting the edges of a water course against the physical action of water, substantially as herein described with reference to the accompanying drawings.