JP2878463B2 - Beach erosion prevention structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beach erosion prevention structure for preventing beach sand from being eroded by waves and flowing offshore.

[0002]

2. Description of the Related Art Conventionally, as a countermeasure against beach erosion, a so-called offshore breakwater in which a permeable wave-breaking structure is installed offshore to control the waves that cause sand to move to reduce the movement of sand on the beach. Many construction methods are used.

However, this method of constructing a breakwater does not directly control the movement of sand on the beach, and cannot be said to be a fundamental erosion prevention measure. In addition, conventional wave-dissipating structures have a great deal of reflection as structures protrude from the surface of the sea, impairing the natural beach scenery and hindering hydrophilicity, and effective alternatives are being sought. is the current situation.

As a countermeasure for preventing beach erosion without impairing the scenery, there is known a method of laying an erosion prevention mat in which a breaking wave zone where sand is most frequently floated by a wave is covered with a mat. It only prevents the generation of floating sand clouds in the part that has been set, but cannot prevent the outflow of once floating sand clouds.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is not only to prevent the occurrence of floating sand clouds and to prevent erosion of the beach, but also to go one step further and to reduce the sand clouds generated by the waves by the force of the waves themselves. It is an object of the present invention to obtain a beach erosion prevention structure which can be moved to the land side by using the shore and is excellent in view.

[0006]

The inventor of the present invention has been studying measures against beach erosion for many years, and found that a reef structure called a demon washing board on the Nichinan coast in Miyazaki Prefecture, which is widely known nationwide, removes offshore sand. Based on the finding that the surface of the wavy body is not covered,
As a result of conducting various studies on the shape of this wavy body,
This is a completed beach erosion prevention structure of the present invention.

That is, the beach erosion prevention structure of the present invention comprises:
The above problem was achieved by reversing the eyes of the demon's washboard and installing a wavy structure on the sea floor with a continuous wave peak deflected offshore.

[0008]

[Action] In general, the mechanism of beach erosion by waves is complicated, but the horizontal reciprocation of water molecules by waves causes the sand to roll up on the surface of the sand brick on the sea floor, which becomes a sand cloud and floats in the seawater. However, it is presumed that the suspended sand is taken offshore by the bottom laminar flow, and the erosion of the seabed gradually progresses.

Therefore, according to the beach erosion prevention structure of the present invention, when a wave passes over a wavy structure provided on the sea floor, water molecules repeat horizontal reciprocating motion on the surface of the wavy structure. Since the wave-shaped peaks whose body shape is continuous are off-shore, vortices are less likely to occur when water molecules move toward the land, and therefore, there is less occurrence of sand clouds.
On the other hand, as the water molecules move offshore, more eddies will form and create sand clouds, which will be transported to land the next time the water molecules move to land. .

That is, the wavy structure of the present invention is configured such that the generation of eddies is reduced when water molecules move on the land side, and the vortices are generated more when the water molecules move offshore.

As described above, the beach erosion prevention structure of the present invention is not limited to simply preventing erosion of the portion covered by the wave-like structure, but utilizes the vortex generating action of the wave-like structure generated by the wave and the force of the wave itself. And move the sand to the land side.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on an embodiment shown in the drawings.

FIG. 1 is a perspective view of a beach erosion prevention structure according to the present embodiment, and FIG. 2 is a sectional view taken along line AA of FIG. FIG. 3 is a perspective view of a specific example of a block constituting the wavy structure.

In FIG. 1, reference numeral 1 denotes a wavy structure, in which a continuous waveform peak T is deflected offshore. The corrugated structure 1 is configured by combining a plurality of concrete blocks 2 in the front-back and left-right directions.
S is sand deposited on the wavy structure 1.

The block 2 constituting the wavy structure 1
May be any shape as long as the peak T of the continuous waveform is formed so as to be offshore when combined. For example, as shown in FIG. It has an inclined surface 2a and a gentle inclined surface 2b, and has an engagement protrusion 2c on the base end side and an engagement protrusion 2 on the lower rear portion of the steeply inclined surface 2a.
The one in which an engaging groove 2d capable of engaging with c is formed may be used. In the block having this configuration, the blocks 2 can be laid on the seabed in an engaged state with each other, so that movement and displacement of the block 2 due to an ocean current or the like can be prevented.

In addition, a trapezoidal block in which the upper surface is inclined as shown in FIG. 3B or a block in which a step 2e is formed on the upper surface of the block 2 as shown in FIG. 3C is used in combination. You can also.

As a position where the corrugated structure 1 is installed, generally, a shallow sea area of about 2 m to 10 m is preferable. The laying width B needs to be about 1/2 of the traveling wavelength in consideration of the stability of the wavy structure 1, and the interval L between the peaks T of the wavy structure is about 1/100 of the wavelength. Is preferred. Further, the depth D of the groove is generally 0.2 to 0.4.
m is preferred.

In order to install these blocks 2 on the sea floor and construct the corrugated structure 1, in order to save labor on the sea, a plurality of blocks 2 are combined in advance and a sabo sheet is attached to the bottom surface. And 1 unit 10m ²
It is effective to set the inner and outer weights to about 10 tons in the air, and to use the hanging metal fittings provided on a crane or the like to grasp and install them on the seabed.

Since the beach erosion prevention structure of the present invention is configured as described above, even if the sand eroded on the beach flows on the wavy structure, it will not flow further offshore. . Therefore, it is an effective measure to prevent erosion instead of the conventional breakwater method using wave-dissipating blocks on the coast where beach erosion has progressed, and the construction cost is about half that of the breakwater method. The beach can be reproduced.

Further, by applying the present structure to the openings of the breakwaters currently constructed nationwide, it is possible to correct the change in the shoreline to a more natural one.

Further, by manufacturing the corrugated structure from a thin concrete plate, it is possible to use the corrugated structure even in a soft ground having a small ground support force.

By arranging the steeply inclined surface of the corrugated structure so as to face the land side, it is possible to adopt a structure for preventing sand from drifting to the corrugated structure.

[0023]

As described above, the beach erosion prevention structure of the present invention is provided with a corrugated structure having a shape in which continuous waveform peaks are deflected to the offshore side, thereby covering the corrugated structure. It is possible to move the sand to the land side by utilizing the vortex generating action generated by the wave and the force of the wave itself, instead of simply preventing the erosion of the damaged portion.

[Brief description of the drawings]

FIG. 1 is a perspective view of a beach erosion prevention structure of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a perspective view of a specific example of a block constituting a wavy structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Corrugated structure 2 Block 2a Steeply inclined surface 2b Slowly inclined surface 2c Engagement protrusion 2d Engagement groove 2e Step T Wave peak S Sand

Claims (1)

(57) [Claims] 1. A beach erosion prevention structure, wherein a wave-like structure having a shape in which a continuous waveform peak is deflected offshore is installed on the sea floor.