GB2284002A

GB2284002A - A modular coastal protection system

Info

Publication number: GB2284002A
Application number: GB9323835A
Authority: GB
Inventors: George Hayes
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-11-19
Filing date: 1993-11-19
Publication date: 1995-05-24
Also published as: GB9323835D0

Abstract

A modular construction coastal protection system comprises a plurality of blocks 1, 2 adapted to be interconnected to form a solid wall. Each block 1, 2 has either a tongue 3 or a groove 4 extending substantially the full length of each of the sides thereof. The tongue 3 or groove 4 is, respectively, received in or receives the groove 4 or tongue 3 in the side of the block immediately adjacent thereto in the wall. A reinforcing bar 6 may be inserted in a hole extending vertically through the sides of each column of blocks. <IMAGE>

Description

DESCRIPTION A MODULAR COASTAL PROTECTION SYSTEM The present invention relates to coastal defences for protecting against and preventing coastal erosion. More specifically, the present invention relates to a modular coastal protection system which is comprised of a plurality of interconnectable blocks.

The present invention also relates to a method of forming a coastal defence using the aforesaid modular coastal protection system.

In many parts of the U.K. and, indeed, throughout the world, coastal erosion represents a serious problem. Within living memory large areas of land have slowly, but surely, been washed away into the sea. On the east coast of England, in particular, this coastal erosion has resulted in the loss of valuable farm land and even the loss of property as the land on which homes, initially built at some distance from the sea, has washed away to drop those homes into the sea.

Over the years many different solutions have been proposed and tried for the problem of coastal erosion.

These have all enjoyed varying degrees of success.

One such solution is the building of groynes made from wood or concrete on the beaches in front of the threatened coastline. These groynes take the form of low fences which extend down the beach into the sea.

The principle by which these groynes work is that they interrupt and break up the tidal flow over the beach thus preventing sand and other coastal material making up the beach from being washed away, and allowing sand and other material carried by the sea to drop down onto the seabed. To some extent groynes do provide an effective defence against coastal erosion as they prevent the beach which protects the coastline behind from being washed away. However, after a heavy blow these groynes may be washed out of the seabed thus necessitating their replacement at a not inconsiderable cost.

Another solution which has been proposed and tried in some areas is placing heavy duty cargo nets over the coast which are backfilled with waste material.

Typically, this waste material is concrete rubble or even tyres - tyres because they are thought to absorb the impact of waves on them which prevents the sea from washing out coast behind them. The theory is that over a period of use sand and other coastal material collects in the interstices between the waste material until a solid wall is formed. However, experience has shown that even these systems may be washed out by the sea.

Yet another solution which has been proposed and tried is to take sand from one area and drop it on the beach in front of the coastline to be protected. Not only is this an expensive solution, but it is also a controversial one inasmuch as the removal of sand from one area may encourage coastal erosion in that area, whilst never providing a permanent solution to the coastal erosion in the area to which it is transferred.

It is an object of the present invention to provide a coastal protection system which is of modular construction, thus facilitating its installation and assembly.

It is yet another object of the present invention to provide a method of forming a coastal defence system which is simple, requires minimal preparatory work and is not prone to be washed out by the sea.

According to a first aspect of the present invention there is provided a block for use in the fabrication of a modular construction coastal protection system which block has either a slot or a tenon or tongue in each of the sides thereof, each of which slots or tongues is adapted to engage, respectively, with the tongue or slot on the side of another block, thus facilitating the interconnection of a plurality of blocks to form a solid wall.

In a preferred embodiment of the present invention the block is square in shape and has a groove and a tongue on each of the two pairs of opposing sides.

This arrangement allows the blocks in a section of blocks within a wall of blocks to slide downwards relative to the section of blocks on each side thereof without imparing the overall structural integrity of the wall. This is a significant advantage in a coastal protection system as it means that if material is washed out from under a particular section of the wall, the blocks in that section can simply settle down into the supporting substrate. In known coastal protection systems as soon as material is washed away from under the system or the supporting substrate becomes unstable, the structural integrity of the system is weakened. If repairs are not carried out soon after this the system may fail altogether within a relatively short period of time.As columns of blocks settle deeper into the substrate the overall height of the wall can be maintained by adding new blocks to the top of the section.

Preferably, one of the two tongues on each block is shorter in length than the slots and the block is mounted in a wall of blocks with this tongue forming the vertical side of the block. This ensures that a continuous hole runs vertically down each side of each column of blocks in the wall. A reinforcing bar can be inserted down each of these holes and embedded in the substrate supporting the wall. If the height of the wall demands it a plurality of reinforcing bars may be connected end to end to achieve the required overall length. For this purpose each bar has a spigot at one end and a hole in the other end.

Preferably, each block can be bolted to the block neighbouring it on each side thereof. Conveniently, the bolts used are jay bolts which allows stiffening bars to be secured to the front and/or back of the wall.

Preferably, each block has a drainage hole in it to prevent water from accumulating behind the wall.

Preferably, the block is fabricated using fibreglass reinforced concrete.

According to a second aspect of the present invention there is provided a modular construction coastal protection system formed from a plurality of blocks in accordance with the first aspect of the present invention which have been interconnected together.

According to a third aspect of the present invention there is provided a method of forming a coastal defence using the blocks in accordance with the first aspect of the present invention wherein a level trench is excavated into the beach immediately in front of the section of coastline to be protected, a first row of blocks is positioned in the trench which is inclined at an angle towards the coastline, reinforcing bars are then slid into the vertical holes between the blocks and embedded into the beach substrate, and additional rows of blocks are built up on the said first row of blocks until the required height is achieved whilst maintaining the initial angle of inclination.

Preferably, the space between the resultant wall of blocks and the coastline behind it is backfilled with hardcore, gravel and/or sand.

Preferably, the angle of inclination of the wall is 70 degrees. This has been found to be most effective in dissipating the energy of waves incident upon the wall, thus minimising any possibility of the wall being breached by the sea.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a front view of two blocks in accordance with the first aspect of the present invention which are interconnected side by side; Fig. 2 shows a partial side view of a coastal protection system in accordance with the second aspect of the present invention, formed from the blocks shown in Fig. 1; Fig. 3 shows a side view of a specially designed block to complete the top of the coastal protection system; and Fig. 4 shows a side view of a specially designed block to complete the ends or sides of the coastal protection system.

Referring to Fig. 1 of the drawings there is shown two interconnected blocks 1, 2. Each block 1, 2 is identical and is pre-cast using fibreglass reinforced concrete.

Each block 1, 2 is generally square in shape and has a tenon or tongue 3 bordering two of the adjacent sides thereof and a slot 4 in the other two adjacent sides thereof. The tongue 3 and the slot 4 allows each block to be interconnected with another block on each of the four sides thereof. However, the length of the tongue 3 on the side of the block is less than the depth of the slot 4 on the side of the block so that when two blocks are interconnected side by side a gap 5 is formed between the end of the tongue 3 and the bottom of the slot 4. In use, the gap is intended to receive a reinforcing bar 6 (only partially shown).

The purpose of this reinforcing bar will be explained hereinbelow. As can be seen in Fig. 2 the length of the tongue 3 at the top of the block is the same as the depth of the slot at the bottom of the block. This ensures that the connection between blocks interconnected one on top of another is of maximum possible strength.

Each block has a drainage hole 7 in the middle thereof and a locating hole 8 immediately adjacent the edge of each of the four sides thereof. The drainage hole allows any water which collects behind the block when it is assembled into a wall to drain away. As shown in Fig. 2, each of the locating holes 8 is adapted to receive a bolt 9 which allows the block to be bolted to the neighbouring block on each of its four sides.

As seen in Fig. 2, a coastal defence is constructed using the blocks shown in Fig. 1 by digging a trench into the beach substrate 10. A first row of blocks 11 is then positioned in this trench and bedded in at an angle which is inclined towards the coastline to be protected - that is to say away from the sea.

Ideally, this angle of inclination is 70 degrees as this has been found to be most effective in absorbing wave energy - an important consideration for any effective sea defence.

Once the first row of blocks 11 is in place a reinforcing bar 6 is inserted into the gap between each adjacent pair of blocks and embedded in the beach substrate. To facilitate this the reinforcing bars 6 may be greased before insertion. Another row of blocks 12 is then placed on top of the first row 11. Each block in the second row 12 is bolted to the block below it in the first row 11 with a jay bolt 9 which also allows a stiffening rod 13 to be clamped in place at the back of the wall.

Hardcore, sand and gravel, or any other suitable materials, are then used to backfill behind the wall.

The building process is then continued until the desired height of wall is reached, backfilling and tamping down at two row intervals.

The wall is finally finished by securing a row of the blocks shown in Fig. 3 to the top of the wall and a column of the blocks shown in Fig. 4 to each side of the wall. However, it should be noted that the use of these additional blocks is optional and may be dispensed with if deemed unnecessary.

The modular construction coastal defence system described hereinbefore is ideally suited for preventing erosion of cliffs which are made of relatively soft material such as the clay found along the Holderness coast. In this regard it is envisaged that the clay will gradually amalgamate with the backfilling material to provide a firm and solid base. Further erosion from beneath the cliff face is prevented and it is even envisaged that by building successive walls, one in front of the other, land may even be reclaimed from the sea.

Claims

1. A modular construction coastal protection system comprising a plurality of blocks adapted to be interconnected to form a solid wall, wherein each block has either a tongue or a groove extending substantially the full length of each of the sides thereof, which tongue or groove is, respectively, received in or receives the groove or tongue in the side of the block immediately adjacent thereto in the wall.

2. A modular construction coastal protection system according to Claim 1, wherein each block is square in shape and has a groove and a tongue on each of the two pairs of opposing sides.

3. A modular construction coastal protection system according to Claim 1 or 2, wherein each block comprises fixing holes in the walls of the grooves and in the tongues to enable the blocks to be bolted together side by side in the wall.

4. A modular construction coastal protection system according to Claim 3, wherein jay bolts are used to bolt the blocks together and to secure stiffening bars to the front and/or back of the wall.

5. A modular construction coastal protection system according to any preceding Claim, wherein some or all of the blocks are provided with drainage holes to prevent water from accumulating behind the wall.

6. A modular construction coastal protection system according to any preceding Claim, wherein the blocks are fabricated from fibreglass reinforced concrete.

7. A modular construction coastal protection system according to any preceding Claim, wherein a continuous hole extends vertically through or down the sides of each column of blocks in which a reinforcing bar is received and embedded in the substrate supporting the wall.

8. A modular construction coastal protection system according t Claim 7, wherein the width of each tongue forming the vertical side of a block is less than the depth of each groove forming the vertical side of a block so that when the two are interconnected a gap is formed between the two.

9. A modular construction coastal protection system according to any preceding Claim, wherein hardcore, gravel or sand is used to backfill the space behind the wall of blocks.

10. A modular construction coastal protection system according to any preceding Claim, wherein the wall of blocks is inclined or leans away from the sea and towards the coastline.

11. A modular construction coastal protection system according to Claim 10, wherein the angle of indication of the wall of blocks to the ground is 700.

12. A block for use in the fabrication of a modular construction coastal protection system which block has either a groove or a tongue extending substantially the full length of each side thereof, which groove or tongue is adapted to engage with the tongue or groove, respectively, in the side of another block, thus facilitating the interconnection of a plurality of blocks to form a solid wall.

13. A method of forming a modular construction coastal protection system using a plurality of blocks adapted to be interconnected to form a solid wall, wherein a level trench is excavated in the beach immediately in front of the section of coastline to be protected, a first row of blocks is laid in the trench, which row is vertically inclined towards the coastline, reinforcing bars are inserted through holes or gaps formed between the sides of adjacent pairs of blocks and embedded into the beach substrate, and additional rows of blocks are built up on the said first row of blocks until the required height is achieved whilst maintaining the initial angle of inclination.