JP2835867B2 - Coastal erosion prevention method using wave-dissipating structures - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of preventing erosion of a shore using a structure having a wave-dissipating function (prior art). In most cases, concrete breakwater blocks or rocks are piled up from the sea floor, such as a straight jetty or a breakwater installed at a point about 100m away from the coast. An artificial reef construction method has been developed in which tons of rocks are stacked up to a height of about 1 m from the water depth at low tide.

(Problems to be Solved by the Invention) However, the above-mentioned coastal erosion prevention method is a method in which several tons of concrete tetrapot (registered trademark) or rocks are piled up from the sea floor, and the tide level is large. In areas where there is no quarry nearby, it is extremely difficult to transport rocks and tetrapots, and this method is extremely limited in terms of location. In addition, if the seabed is sandy or mud geological, a large amount of foundation work is essential to prevent rocks and tetrapods from flowing offshore.

[Means for solving the problem]

The method proposed by the present invention is a completely different construction method from the conventional breakwater method centered on civil engineering work in which embankments mainly composed of heavy objects such as tetrapods or rocks or concrete bodies are installed offshore of the coast. is there. It uses a net or metal frame made of metal, resin, or synthetic fiber to make a semicircular or cylindrical structure or cage-like housing, and a medium spherical sphere with a specific gravity of 0.5 to 0.7 to give buoyancy in it. ,
In order to increase the surface area with a sphere to have a wave canceling function, a circular hole is made in the center of the sphere in the vertical direction, and fan-shaped openings are provided above and below the circumference, and the center of the fan-shaped opening is closer to the center than one side. A floating sphere that floats in water with a specific gravity of 1.5 to 2 with a line directed to it, and a specific gravity of 3 to 4 to have a wave-dissipating function for waves that rise from the bottom of the floating breakwater while rotating and coming in To store a solid sphere.

The diameter of each of the three types of spheres is 15 to 30 cm, and the storage ratio of these wave-dissipating spheres is 40 to 70% depending on the strength of the waves. The wave energy is converted into the kinetic energy of these spheres, and the floating wave structure with the function of converting the waves into the current is installed in the sea offshore in parallel with the sandy beach on the coastline where wave erosion is remarkable, It is a floating wave structure that is fixed to the anchor with mooring lines to prevent the floating wave structure from flowing out due to waves.All submarine foundation work is unnecessary and can be installed regardless of tides and tides. Coastal erosion prevention method that is economical and can be installed in a short time.

In this method, when a wave coming from the offshore wave while rotating from the offshore hits the floating wave structure installed offshore in parallel with the coastline while floating in the sea, the wavebreaker housed in the floating wavebreaking structure Among the spheres, a solid sphere having a high specific gravity rotates and is lifted by waves rising from the bottom of the floating breakwater while coming in, and then collides with the floating sphere. The floating spheres also receive transverse waves and oblique waves and collide with each other while moving, reducing the energy of the rotating waves. The waves that have escaped from the wave-breaking structure are diverging waves that reach the shore, return waves, and collide with the floating breakwater when returning offshore. The waves collide with the waves, and the return waves are canceled by the mutual interference between the waves, and the energy of the wave approaching is reduced.

(Action) Various spheres (diameter 15cm to 30cm) with a specific gravity of 0.5 to 4 in a semicircular or cylindrical structure composed of a metal frame and net, or a metal cage. When a wave-dissipating structure that accommodates in a range of 40-70% is installed in the sea in a floating state, both the spheres with a specific gravity of 1.5-2 and the spheres with a specific gravity of 3-4 in the structure are in a floating state Therefore, when receiving waves, specific gravity 1.5
The floating sphere having a large surface area of ~ 2 moves, rotates and collides.

On the other hand, a floating sphere having a specific gravity of 3 to 4 receives a low wave, is lifted up, moves and collide, and converts the energy of the wave into the energy of the sphere. This wave-dissipating structure is installed alongside the shoreline at a certain distance from the shore, offshore, in a floating state in the sea, and fixed with mooring lines and anchors to prevent this wave-dissipating structure from moving and flowing away This is an erosion prevention method.

According to this method, when a wave-dissipating structure installed in a floating state in the sea receives a wave approaching from offshore, it is converted into the movement of a floating sphere, and the wavelength and wave height are greatly reduced. However, since 100% of the waves are not eliminated, a part of the wave that has escaped from the wave-dissipating structure reaches the shore and returns as a wave. This wave is a method of colliding with a wave exiting the wave, reducing the energy of the wave by a synergistic effect due to the mutual interference of the waves, extinguishing the wave, and preventing coastal erosion by a return wave.

Most of the shore sand movement occurs underwater. It is the result of waves and the flow they create. As long as there are waves, the beach is constantly moving.

Especially when the waves approach the beach and the waves are small, the sand on the seabed moves toward the shore along with the orbital motion of the water molecules. On the other hand, when the waves are large and high, they carry the sand off the shore and offshore. If there is a steep shoal such as a sand bar, the waves break there, and the sand bar acts as a filter.
Also, sand moved by severe turbulence due to the waves has structures that prevent the waves and accumulate wherever the action of the waves is reduced.

The present invention is a method for preventing coastal erosion by a wave breaking structure devised based on such a natural phenomenon.

Spheres with different specific gravities are accommodated in a semi-circular or circular structure using a net reinforced with an iron frame, or a metal cage with a specific gravity of 40-70% depending on the level of waves. The wave structure is set 50cm to 1m below the sea floor in the sea and set alongside the coastline. Since this wave-absorbing structure is entirely floating, it is fixed with mooring lines and anchors to prevent erosion and movement due to waves to make it a coastal erosion prevention body.

When a wave coming from offshore hits this coastal erosion prevention body, the specific gravity of the floating spheres contained in the wave-breaking structure is 1.5 to 1.5
The sphere of the floating sphere having a large surface area of 2 rotates, moves up and down, right and left, and collides between the spheres. On the other hand, specific gravity 3
The above-mentioned heavy sphere moves up and receives a low wave among the swelling waves. Most of the wave is converted into spherical motion of the wave-dissipating structure and its energy is attenuated, but a part of the wave rushes toward the shore. When this wave returns as a return wave and returns to the wave-dissipating structure, it becomes the kinetic energy of the floating sphere again, or it collides with the next shunt wave inside and outside the structure, and the energy of both the shunt wave and the return wave is Offset.

In this way, the wave-dissipating structure reduces large and high waves from offshore by its spherical motion, but the wave-dissipating structure reduces the housing density of the containing sphere so that seawater can move freely. There is a space where water flows freely. This structure enables the wave-dissipating structure not only to move the sphere, but also to reduce and eliminate waves due to the collision of the wave of the wave approaching and the wave of the returning wave. As a result, it is possible to prevent coastal erosion by extinguishing a wave having a large wavelength and wave height, and to apply the present invention to restoration of a beach already eroded by a wave.

[Brief description of the drawings]

FIG. 1 is an overall view of the shore erosion prevention by the wave breaking structure of the present invention. Is a sphere, is an iron frame, is a mooring line, is an anchor Figure 2 shows the shape of a wave-dissipating structure ~ is a wave-dissipating structure using a combination of a net and a frame. Is a sphere, b. Is net, c. Is the frame

Claims (1)

(57) [Claims] 1. A semi-circular or cylindrical structure or a cage-like housing made of a net or metal frame made of metal or resin or synthetic fiber, and a hollow having a specific gravity of 0.5 to 0.7 in order to have buoyancy therein. A spherical hole is formed in the center of the sphere in the vertical direction in order to increase the surface area so as to have a wave-eliminating function, a fan-shaped opening is provided above and below the circumference, and the center is located at one side of the fan-shaped opening. A floating sphere floating in water with a specific gravity of 1.5 to 2 with a line directed toward the part, and a specific gravity of 3 to give a wave-dissipating function to the waves that roll up from the bottom of the floating breakwater while rotating while coming in ~ 4 solid spheres are stored. Each of the three spheres with different specific gravity has a diameter of 15 ~ 30cm
According to the strength of the waves, the storage rate of the wave-dissipating sphere is set to 40 to 70% depending on the strength of the waves, and the wave-dissipating structure with the function of converting the wave energy to the kinetic energy of these spheres and converting the waves into a flow is remarkably wave eroded A coastal erosion prevention method that is installed on the shoreline in a suspended state in the sea offshore in parallel with the sandy beach, and fixed to the anchor with mooring lines to prevent the wave-dissipating structure from being washed away by waves.