GB1596350A - Construction block for a breakwater or a bulwark - Google Patents

Description

(54) CONSTRUCTION BLOCK FOR A BREAKWATER OR A BULWARK (71) We, IIDA KENSETSU CO., LTD, of 2-15-25, Higashi Hie, Hakata-ku, Fukuoka, Japan, a Japanese Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to blocks for constructing breakwaters or bulwarks which can effectively decrease the force of high magnitude waves while providing stability for the structure.

The invention provides a construction block for constructing a breakwater or a bulward, the block comprising a vertical front wall, a vertical intermediate wall disposed parallel to and spaced from the front wall, a vertical rear wall disposed parallel to and spaced from the intermediate wall, a pair of mutually parallel and spaced apart vertical walls disposed perpendicular to the front, intermediate, and rear walls and interconnecting the said three walls to form a first chamber between the front and intermediate walls and a second chamber between the intermediate and rear walls, each chamber being open at both the top and the bottom thereof, and a through hole formed in the front wall for allowing water to pass into and out of the first chamber, the rear wall having no through hole.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a block of this invention seen from above; Figure 2 is a perspective view of the same block seen from below; Figure 3 is a longitudinal cross sectional view taken along the line I-I of Figure 1; Figure 4 is a chart showing the relationship between the total horizontal pressure and time; Figure 5 is a perspective view showing a breakwater comprising a wall constructed by the above blocks Figure 6 is a perspective view of another block of this invention seen from above; Figure 7 is a perspective view of the block of Figure 6 seen from below; and Figure 8 is a perspective view of a quay comprising a bulwark constructed by the blocks of Figures 6 and 7.

The block shown in Figures 1 to 3 has three walls, namely a front wall 1, an intermediate wall 2 and a rear wall 3 disposed in parallely spaced-apart relationship. Those three walls are joined by two parallel, spaced interconnecting walls 4 which are arranged perpendicular to the 'former three walls 1, 2 and 3. Between the front wall 1 and the intermediate wall 2, a first vertically-open-ended chamber 5 is formed while a second vertically openended chamber 6 is formed between the intermediate wall 2 and the rear wall 3.

A horizontal through hole 7 is formed in the central portion of the front wall 1 such that the incident wave passes therethrough and enters the first chamber 5.

Numeral 8 indicates cut-out portions provided at opposite ends of the front wall 1. The cross-section of each cut-out portion 8 is equal to half the cross-section of the horizontal hole 7 so that when the blocks are arranged laterally as shown in Figure 5, a pair of cut-out portions 8 form a horizontal opening equivalent to the horizontal hole 7.

The block is further provided with means for facilitating the stacking-up of blocks.

Such means consists of retaining protrusions 9 formed on the upper edges of the interconnecting walls 4 and corresponding recesses 10 formed in the lower edges of the walls 4. By engaging the protrusions 9 with the recesses 10 on another block, the blocks can be readily and accurately stacked up on one another.

Numeral 11 (Figure 5) indicates a block uniting material (bulk of gravel) which can promote the integrity of the structure.

Although a bulk of gravel is employed as such material in the attached drawings, other charging materials such as prepacked concrete can be used. Numeral 12 indicates a horizontal foundation which supports the structure on the sea bed.

Referring now to the preferred feature of the parts of the block, the total of the crosssectional area of horizontal hole 7 and the cut-out portions 8 should preferably account for about 25 to 35 percent of the total area of the front wall 1. The length L1 of the first chamber should preferably be 2 to 8 percent of the incident wave length L for efficiently reducing the wave force while the length L2 of the second chamber must be determined in view of the total weight (volume) of the block uniting material 11 to be charged therein. Furthermore, the interconnecting walls 4 should preferably be arranged such that each wall 4 connects the portions of respective walls 1, 2 and 3 which are disposed l/4B (width of the block) away from the respective ends of respective walls 1, 2 and 3.

Construction of a breakwater using these blocks will now be described.

First, a breakwater base including a horizontal foundation plate 12 is constructed on the sea bed and a first row of blocks are mounted on the plate 12 such that front walls 1 of the blocks face out to the sea. Thereafter, subsequent rows of blocks including the second row of blocks are stacked one on another with the joints between adjacent blocks being staggered. (Of course, the joints do not necessarily have to be staggered, and the blocks may be stacked aligning the side lines of all blocks on the same vertical line.) In this embodiment, the stacking operation is carried out steadily and readily due to the provision of the retaining protrusions 9 and the retaining recesses 10 on each block. In this manner, the desired number of rows of blocks are stacked until a breakwater of a desired height is constructed.

Finally, the block-uniting material 11 (for example, gravel) is charged into the inside of the second chamber 6 and the construction of the breakwater is completed. As mentioned above, since each interconnecting wall 4 of the block connects portions of respective walls 1, 2 and 3 which are disposed l/4B (width of the block) away from either end of the said respective walls, second chambers 6 of the same space can be formed in a vertical direction as well as a widthwise direction even if the blocks are stacked in a staggered pattern. Accordingly, along with the charging of gravel into the chamber 6, the blocks are integrally formed into a rigid structure due to the frictional resistance of the gravel which works in a vertical direction as well as a horizontal direction.

Furthermore, the gravel shows the friction coefficient of 0.8 when the blocks receive an external force from a wave. This value contrasts with a friction coefficient of 0.5 for conventional concrete blocks.

Since a conventional breakwater made by blocks is entirely of a concrete construction, only 50 percent of the weight of the structure can be used as resistance against the outer force in the stability computation of the structure. Whereas, with this invention, about 70 to 80 percent of the weight of the structure can be employed as such resistance. Furthermore, since the gravel is inexpensive compared to concrete, the structure can be constructed cheaply.

Moreover, a breakwater constructed using the blocks of the present invention can remarkably reduce the wave force and thereby promote the stability of the structure.

Furthermore, since the block of this invention has a high wave force dissipation effect with minimum cross-sectional area, the structure can be constructed economically.

Generally, as shown in Figure 4, when the wave hits a conventional structure, the horizontal pressure of the wave (shown by the solid line) rapidly increases as soon as the wave hits the structure and soon reaches a maximum value P0, and then immediately and rapidly decreases. After the rapid decrease, the horizontal pressure gradually disappears. Therefore, the structure should be large enough to withstand the maximum horizontal pressure P0.

Accordingly to the present invention, the wave firstly hits the front wall 1. The maximum horizontal pressure P, at this time is less than P0 since the front wall 1 is provided with the hole 7 and cutout portions 8. The wave weakened after hitting and passing through the hole 7 and cut-out portions 8 secondly hits the intermediate wall 2. The horizontal pressure P2 is also less than P0. In other words, P0 is distributed to P, and P2. Accordingly, if the ratio of the cross-sectional area of the hole 7 and cutout portions 8 as well as the distance L1 between the front wall 1 and the intermediate wall 2 are set within the aforementioned range, P0 could be evenly distributed into P, and P2. Furthermore, the value of P, and P2 (horizontal pressure) per se could become still less. In fact, the horizontal pressure that the breakwater of this invention receives can be T to 1 of the pressure received by the conventional type of breakwater by making the ratio of crosssectional area of the horizontal hole 7 and cut-out portions 8 at 25-35 percent of the total area of the front wall 1 and L, at 2/108/100 of the incident wave length. In view of the above, the block described shows a highly improved affect on lowering wave pressure.

As discussed above, the block according to the present invention is mainly used for constructing breakwaters. However, the block is also applicable to bulwarks for harbour-quays where the calmness of the wave is required, since the block can absorb the reflected wave.

In such a case, the intermediate wall 2 is provided with cut-out portions 13 (Figures 6 and 7) each having a cross-sectional area equal to 1/3-1/4 of the cross-sectionai area of the holes 7 of the front wall 1. Through the cut-out portions 13, sea water enters the second chamber 6 from the first chamber 5.

No block uniting material is charged into the second chamber 6 of this modified block.

The block described has the following advantages.

1) Since the shape and the construction of the block are simple, manufacture and installation are conducted easily.

Accordingly, the construction period is shortened as well as the overall economic advantage is obtained.

2) Since the overall weight of the structure constructed by the blocks according to the present invention is much smaller than the weight of a structure formed by conventional type blocks. such blocks can be used in a site where a firm base cannot be obtained.

3) Due to the block uniting material in the second chamber, not only the frictional resistance between the contacting surfaces of blocks but also the friction resistance of the gravel are employed as resistance against wave force. Therefore the brakewater structure formed by the blocks described is extremely stable.

WHAT WE CLAIM IS: 1. A construction block for constructing a breakwater or a bulwark, the block comprising a vertical front wall, a vertical intermediate wall disposed parallel to and spaced from the front wall, a vertical rear wall disposed parallel to the spaced from the intermediate wall, a pair of mutally parallel and spaced apart vertical walls disposed perpendicular to the front, intermediate, and rear walls and interconnecting the said three walls to form a first chamber between the front and intermediate walls and a second chamber between the intermediate and rear walls, each chamber being open at both the top and the bottom thereof, and a through hole formed in the front wall for allowing water to pass into and out of the first chamber, the rear wall having no through hole.

2. A block according to claim 1, wherein the front wall has cut-out portions at opposite ends thereof, each cut-out portion having a cross-section equal to half the cross-section of the through hole.

3. A block according to claim 2, wherein the total cross-sectional area of the through hole and of the cut-out portions amounts to 25 to 35 percent of the total area of the front wall.

4. A block according to any of claims 1 to 3, wherein the distance between the front and intermediate walls is 2 to 8 percent of the incident wave length.

5. A block according to any of claims 1 to 4, wherein the distance between the intermediate and rear walls is sufficient to allow block uniting material to be charged into the second chamber.

6. A block according to any of claims 1 to 4, wherein at least one cut-out portion is formed in the intermediate wall to allow communication between the first chamber and the second chamber.

7. A construction block for constructing a breakwater or a bulwark, substantially as herein described with reference to Figures 1 to 3 or Figures 6 and 7 of the accompanying drawings.

8. A breakwater or bulwark substantially as herein described with reference to Figure 5 or Figure 8 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. cut-out portions 8 at 25-35 percent of the total area of the front wall 1 and L, at 2/108/100 of the incident wave length. In view of the above, the block described shows a highly improved affect on lowering wave pressure. As discussed above, the block according to the present invention is mainly used for constructing breakwaters. However, the block is also applicable to bulwarks for harbour-quays where the calmness of the wave is required, since the block can absorb the reflected wave. In such a case, the intermediate wall 2 is provided with cut-out portions 13 (Figures 6 and 7) each having a cross-sectional area equal to 1/3-1/4 of the cross-sectionai area of the holes 7 of the front wall 1. Through the cut-out portions 13, sea water enters the second chamber 6 from the first chamber 5. No block uniting material is charged into the second chamber 6 of this modified block. The block described has the following advantages.

1) Since the shape and the construction of the block are simple, manufacture and installation are conducted easily.

Accordingly, the construction period is shortened as well as the overall economic advantage is obtained.

2) Since the overall weight of the structure constructed by the blocks according to the present invention is much smaller than the weight of a structure formed by conventional type blocks. such blocks can be used in a site where a firm base cannot be obtained.

3) Due to the block uniting material in the second chamber, not only the frictional resistance between the contacting surfaces of blocks but also the friction resistance of the gravel are employed as resistance against wave force. Therefore the brakewater structure formed by the blocks described is extremely stable.

WHAT WE CLAIM IS: 1. A construction block for constructing a breakwater or a bulwark, the block comprising a vertical front wall, a vertical intermediate wall disposed parallel to and spaced from the front wall, a vertical rear wall disposed parallel to the spaced from the intermediate wall, a pair of mutally parallel and spaced apart vertical walls disposed perpendicular to the front, intermediate, and rear walls and interconnecting the said three walls to form a first chamber between the front and intermediate walls and a second chamber between the intermediate and rear walls, each chamber being open at both the top and the bottom thereof, and a through hole formed in the front wall for allowing water to pass into and out of the first chamber, the rear wall having no through hole.

2. A block according to claim 1, wherein the front wall has cut-out portions at opposite ends thereof, each cut-out portion having a cross-section equal to half the cross-section of the through hole.

3. A block according to claim 2, wherein the total cross-sectional area of the through hole and of the cut-out portions amounts to 25 to 35 percent of the total area of the front wall.

4. A block according to any of claims 1 to 3, wherein the distance between the front and intermediate walls is 2 to 8 percent of the incident wave length.

5. A block according to any of claims 1 to 4, wherein the distance between the intermediate and rear walls is sufficient to allow block uniting material to be charged into the second chamber.

6. A block according to any of claims 1 to 4, wherein at least one cut-out portion is formed in the intermediate wall to allow communication between the first chamber and the second chamber.

7. A construction block for constructing a breakwater or a bulwark, substantially as herein described with reference to Figures 1 to 3 or Figures 6 and 7 of the accompanying drawings.

8. A breakwater or bulwark substantially as herein described with reference to Figure 5 or Figure 8 of the accompanying drawings.