JP2006070626A - Wave dissipating block and wave dissipating structure using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent seaside erosion by combining the wave dissipating effect and sand control of a submerged breakwater. <P>SOLUTION: A wave dissipating block 1 is composed of a square bottom plate 2 and a square inclined plate 21 rising from one end of the bottom plate 2 up to a position above the other end. The bottom plate 2 and the inclined plate 21 are integrally molded or formed by assembling parts manufactured as separate bodies. The inclined plate 21 and a stream interfere with each other, and a vortex is formed on the upper face of the inclined plate 21 and rises along the surface. A component heading toward the off shore, of the rising vortex reduces energy of a stream of a billow, reduces a stream flowing into the shore side, and prevents sand from moving toward the off shore from the shore. Since the stream heading toward the shore is reduced, formation of breaking waves is accelerated to improve wave dissipating efficiency. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wave-dissipating block capable of controlling a sand flow phenomenon associated with wave control and a wave-dissipating structure using the same.

A plurality of large-sized wave-dissipating blocks of 10t to 30t made of concrete blocks are arranged to form a submerged dike (artificial reef), and the submerged dike is used as a calm sea area for ocean recreation.
As shown in FIG. 7, a submerged bank is a box-shaped block in which a transmission-type hollow wave-dissipating block having a plurality of openings on its upper surface and a plurality of openings on the upper surface is installed on the mound. (Patent No. 2847399) and is put to practical use.

In addition, a double-leaf type submerged dike using a box having an inclined slit on the upper surface is proposed in Patent Document 2 (Patent No. 3505156), and Patent Document 3 (Patent No. 3298862) describes an upper leaf. There has been proposed a submerged dike using an upright wall box with an opening at the lower end on the offshore side and an inclined slit at the top. (See Figure 6)
Japanese Patent No. 2847399 Japanese Patent No. 3505156 Japanese Patent No. 3298862

The submerged dike (artificial reef) is always submerged under the surface of the water, and a wave-dissipating effect can be obtained without impairing the beach scenery. The effect is recognized, and it is possible to make the sea area suitable for ocean recreation.
However, when a transmission type wave-dissipating block is used, seawater passes through the block. Therefore, in order to obtain the required wave-dissipating performance, it is necessary to widen the top end width, the structure becomes large, and the construction cost is high. It took a long time to complete the construction.

In addition, if wave control is prioritized and the wave-dissipating efficiency is increased, the flow from the offshore to the shore due to the breaking waves generated on the levee body increases, and a large amount of water flow across the dam body as shown in FIG. There was a problem that a water flow spouted from the body to the offshore side was formed, and the sand on the shore side was moved to the offshore by this water current, resulting in erosion of the coast.
The present invention achieves both the wave-dissipating effect and the controlled sediment control, and prevents coastal erosion due to the sediment while effectively performing the wave-dissipation.

The amount of water that flows into the shore side across the submerged dam by reducing the momentum by colliding with the water flow by forming a vortex that rises along the inclined plate by the water flow by providing an inclined plate that extends from one end of the bottom plate to the other end. Is to decrease.
Vortex was efficiently generated by setting the inclination angle of the inclined plate to 45 ° to 60 °.
A connection portion is formed at the end of the bottom plate so that the wave-dissipating blocks can be connected and integrated so that the entire structure can be stabilized.

  This wave-dissipating block is installed on a mound or the like with the tip of the inclined plate facing offshore to form a wave-dissipating structure. Vortices from the bottom to the top along the inclined plate are generated by the water flow from the offshore to the shore caused by waves. Since the inclined plate is installed toward the offshore side, the vortex advances in the direction opposite to the wave traveling direction, collides with the wave, cancels energy, and suppresses the flow velocity of the water flow, so the amount of water flowing into the shore side Decrease. Since the amount of water going to the shore side can be reduced, the amount of water returning from the shore side to the offshore side is reduced, and the outflow of sand on the shore side of the seabed is suppressed, and coastal erosion can be prevented. In addition, by suppressing the flow, the energy of waves can be absorbed by the water flow, and the generation of breaking waves on the offshore side is promoted.

As shown in FIG. 1, the wave-dissipating block 1 is composed of a rectangular bottom plate 2 and a similarly inclined plate 21 extending from one end of the bottom plate 2 to the other end, and the bottom plate 2 and the inclined plate 21 are integrally molded. Or, it is manufactured as a separate body and assembled into a wave-dissipating block.
The bottom plate 2 is a quadrangle having a thickness (t) of about 0.5 m and a side of 2.5 m to 5.5 m, and the inclined plate 21 is attached to the bottom plate 2 at an inclination angle (θ) of 45 ° to 60 °. The thickness is about 0.5 m, the height (H) is 2 m to 5 m, and the tip of the inclined plate 21 is located at a certain distance (L3) from the end of the bottom plate 2, for example, 0.5 m to 1 m. It is like that. The tip of the inclined plate 21 does not protrude outward from the bottom plate 2, and the bottom plate 2 does not collide with the tip of the inclined plate 21 of the existing wave-dissipating block when being connected and damaged. It is like that.

At the end of the bottom plate 2 on the side where the base of the inclined plate 21 is attached, a step portion 22 is provided as a connection portion between the wave-dissipating blocks, and the protruding length (L1) of the step portion 22 is about 1 m. is there.
If necessary, a hanging bracket for transportation and installation is attached to the protruding portion of the step portion 22 of the connecting portion of the bottom plate 2 and the bottom plate 2. Further, a hole (not shown) having an appropriate shape such as a circle or a rectangle is formed in the bottom plate 2 so that a large lifting pressure does not act on the bottom surface of the wave-dissipating block 1 or legs (not shown) are provided.

Waves traveling from offshore are accompanied by water flow toward the shore regardless of whether or not breaking waves are generated. As shown in FIG. 2, the inclined plate 21 and the water flow interfere with each other, and a vortex is generated on the upper surface of the inclined plate 21 and rises along the surface. Since the tip of the inclined plate 21 faces offshore, the rising vortex has a component toward the offshore side, collides with the water flow from the offshore to the shore, and diminishes the energy of the water flow toward the shore. Therefore, the water flow from the submerged dike to the offshore is reduced, and the sand is prevented from moving offshore from the shore.
Moreover, the generation of breaking waves is promoted by reducing the water flow toward the shore, and the wave-dissipating efficiency is improved.

Construction example 1
As shown in FIG. 3, this wave-dissipating block is installed on the mound 3 composed of the seabed or rubble by connecting and using the step portion 22 in order with the tip of the inclined plate 21 facing the offshore side. It is a submerged bank. The top of the wave-dissipating block 1 is set to be lower than the lowest water level due to tides, and the top of the wave-dissipating block 1 is always submerged below the surface of the water at low tide. It is desirable that the top water depth at the water level is about 1.5 m.

The top water depth is preferably 1.5 m or less from the viewpoint of the wave-dissipating efficiency, but it must be determined in consideration of the influence on the navigating ship. By installing a buoy in the sea area around the submarine and taking measures against the ship, it is possible to reduce the top water depth to about 0.5 m.
Since each wave-dissipating block 1 is connected by the step part 22, it is integrated as a structure and is a stable structure.

As already described, in each wave-dissipating block 1, a vortex is generated on the upper surface of the inclined plate 21 by the water flow accompanying the waves, and collides with the water flow to reduce the water flow. At the same time, the generation of breaking waves offshore is encouraged by diminishing water currents.
Mixing of air into seawater is promoted by the generation of vortices and breaking waves, and oxygen is entrained in the seawater, making it preferable as a place of habitat for seafood along with purification of seawater.

Since the wave-dissipating block 1 having the wave-dissipating effect and the water-flow-dissipating effect is connected, the wave energy is attenuated, and the waves rushing from the offshore to the shore side are extinguished and flow into the shore side over the submerged dam Reduce the amount of water flow.
As shown in FIG. 4, if necessary, a large concrete block to be the rear mound 20 is installed on the shore side, or the rear mound is constructed in advance by rubble or the like.

Construction example 2
As shown in FIG. 5, a large block 4 is installed on the front side offshore on the rubble mound 3, and the wave-dissipating block 1 is connected to each other by a step portion 22 on the back side. The rectangular block 4 is for the safety and stability of the entire structure of the submerged dike, and it is desirable to install a concrete block of 20 t or more.
Since wave power does not act directly on the wave-dissipating block 1, it is possible to prevent the wave-dissipating block from moving. It is not limited to a concrete block, and may be a large waste such as abandoned ship and abandoned automobile, and a heavy object such as rubble, or a structure such as a caisson.

As described above, according to the wave-dissipating block of the present invention, the water flow from the offshore to the shore is diminished by the vortex generated on the inclined plate of the wave-dissipating block, so that the amount of water flowing into the shore side is reduced. As a result, the amount of water returning from the shore side to the offshore side is reduced, and the outflow of sand on the shore side is suppressed, thereby preventing coastal erosion.
In addition, the water flow can be absorbed by the water flow because the flow is suppressed, and the generation of breaking waves on the offshore side is promoted. It can be an area.

In addition, since the rise in the average water level can be suppressed, the increase in the amount of overtopping and the generation of beach currents can be suppressed, greatly contributing to the stabilization of the beach.
It can also be used as a breakwater or a revetment using a wave-dissipating block, and the application range of the wave-dissipating block of the present invention is wide.
Since the habitat space is secured by the wave-dissipating block in the surface layer portion of the submerged dike, breakwater and revetment as the wave-dissipating structure of the present invention, it can be a fish reef.

The front view of a wave-dissipating block. Action | operation explanatory drawing of a wave-dissipating block. Sectional drawing of the wave-dissipating structure using a wave-dissipating block. Sectional drawing of a rear mound. Sectional drawing of a wave-dissipating structure with a rectangular block on the offshore side. Sectional drawing of the submerged dike using the box which has the conventional slit. Sectional drawing of the submerged dike using the conventional transmission hollow wave-dissipating block. Explanatory diagram of coastal erosion due to submarine installation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wave-dissipating block 2 Bottom plate 21 Inclined plate 22 Step part 3 Mound

Claims (5)

A wave-dissipating block having an inclined plate that extends from one end of the bottom plate upward to the other end. The wave-dissipating block according to claim 1, wherein the angle of the inclined plate is 45 ° to 60 °. 3. The wave-dissipating block according to claim 1 or 2, wherein a connection portion is formed at an end portion of the bottom plate. A wave-dissipating structure in which a plurality of wave-dissipating blocks each having an inclined plate extending from one end of the bottom plate upward to the other end are connected with the tip of the inclined plate facing the offshore side. The wave-dissipating structure according to claim 4, wherein a block block is installed at the tip of the offshore side.

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