JPH07166524A - Wave dissipating method by liquefaction of sand - Google Patents

Abstract

PURPOSE:To dissipate waves at a beach or a harbor without using a structure such as a breakwater. CONSTITUTION:A water feed pipe 1 provided with many jet holes 2, 2 is installed in the sea bottom sand ground layer 3 of the water area requiring the dissipation of waves, the water fed by a pump 4 is erupted into the sand ground layer 3 from the jet holes 2, 2, and the sand is movably fluidized (liquefied). The sand is largely moved by waves to largely absorb the energy of waves, and the wave height of waves is damped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is applicable to coasts and harbors.
The present invention relates to a wave-dissipating method for fluidizing sand on the seabed to attenuate the wave height.

[0002]

2. Description of the Related Art Conventional seashores and harbors have a breakwater and a breakwater in order to maintain the calmness of these waters and protect various facilities from waves and prevent coastal erosion. Various methods have been adopted to breakwater by constructing various underwater structures such as levee, submerged dike, and seawall.

However, there is a problem that a huge amount of cost is required to install a structure in the sea, and it is not preferable in view of the scenery, and it also hinders the flow of tidal currents and the movement of fish and the like.

The present invention has been made in view of the above-mentioned conventional circumstances, and artificially fluidizes (liquefies) the sand ground in the sea.
By absorbing the energy of the wave by doing so, it is intended to provide a new method capable of eliminating the wave without adversely affecting the landscape and tidal current without installing a heavy structure.

[0005]

The structure of the present invention for achieving the above object will be described with reference to the drawings corresponding to the embodiments. 3 is characterized in that water is injected to liquefy the sand, and the fluid energy of the sand absorbs the wave energy and attenuates the wave height.

[0006] The wave-dissipating method according to claim 2 is the seabed 6
Install the frame-shaped structure 5 covering the required area on the
It is characterized in that a sand ground layer 3 is formed therein, water is injected into the sand ground layer 3 to liquefy the sand, and the fluid energy of the sand absorbs the wave energy and attenuates the wave height. is there.

[0007]

The present invention is configured as described above, and the water sent by the pump 4 is injected into the sand ground layer 3 from the ejection holes 2 and 2 of the water supply pipe 1. This water is normally discharged onto the sand ground 3 through the sand ground 3, but if the flow rate exceeds a certain limit, the drainage will not catch up, resulting in excessive pore water pressure and lifting of sand particles, mobilizing the sand. (Liquefaction) will occur. In this way, if the sand is liquefied to make it easy to move, the sand is largely moved by the wave, and the energy of the wave is largely absorbed, and the wave height is attenuated.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the invention of claim 1 suitable for water wave with sand ground on the sea floor, and FIG. 2 shows an embodiment of claim 2 suitable for water wave with no sand ground. FIG.

First, in FIG. 1, reference numeral 1 denotes a water pipe buried in the bottom portion or the upper and lower middle portion of a seabed sand ground layer 3, the base end of which is connected to a pump 4 installed in water or above water. A large number of ejection holes 2 and 2 are provided on the surface, and water is injected from the ejection holes 2 and 2 by the water supply from the pump 4. Then, a large number of the water pipes 1 are buried at intervals in the seabed of the water area that requires wave breaking.

Next, in FIG. 2, reference numeral 5 denotes a frame installed on a hard seabed ground 6 having no sand ground layer or little sand ground layer, surrounding a required wide area over a required height. As in the previous embodiment, a large number of water supply pipes 1 provided with ejection holes 2 and 2 are installed at the bottom of the water-like structure.
Each is connected to the pump 4. Then, sand or the like is filled in the frame-shaped structure 6 to artificially configure the sand ground layer 3.

In each of the above embodiments, the sand ground layer 3 is formed by injecting water from the jet holes 2 and 2 of the water supply pipes 1 and 1.
The sand is fluidized (called liquefaction) to make it easier to move. As a result, the liquefied sand moves largely due to the waves, absorbs the wave energy, and attenuates the wave height.

Next, an example of an experiment conducted on the embodiment shown in FIG. 2 will be described. In the experiment, width 50 cm, length 30 m
A sand ground layer 3 with a length of 1.7 m and a height of 20 cm is formed in the small waterway of No. 4, and water pipes with small holes every 1 cm are installed in it.
It was placed on the main canal floor. Then, the water depth on the sand ground layer 3 is set to 1
The experiment was conducted under the conditions of 7.5 cm, a wave period of 1 second, and a wave height of 6 cm.

In this experiment, wave waveforms were measured at two points on the offshore side and the shore side of the sand ground layer 3. The result is shown in FIG. The upper part of the figure shows the offshore side waveform, and the lower part shows the shoreside waveform. On the shoreside, a clear decrease in wave height is observed after the water supply to the pipe is started. According to this, when water is sent, a wave height of about 6 cm on the offshore side is attenuated to a wave height of about 3.5 cm on the shore side, and the wave height transfer rate is about 0.6 and the wave energy transfer rate is 0.36. It can be seen that the absorption rate of wave energy is high even in a relatively short sand layer. Therefore, assuming that this experimental scale is 1/100, the wave period is about
10 seconds, wave height 6m, water depth 17.5m, sand ground layer length 170
m, height 20m, in which case the wave height is 6m
It will be attenuated to 3.5m.

The present invention can be used as a breakwater or breakwater at a harbor or coast if the energy to move the pump is obtained. In particular, it seems to be useful as a coastal breakwater that values the landscape. In recent new breakwaters, a submerged dike may be used with an emphasis on the landscape, but a wave near the submerged dike may cause a flow near the submerged dike, which may cause a problem in sand movement. Then there is no such problem.

Further, the opening of the harbor needs to be opened widely for the entry and exit of ships, which is a major cause of waves entering the harbor easily. By using the wave-dissipating method of the present invention at the port entrance, it is possible to reduce waves entering the port without hindering the navigation of the vessel.

Alternatively, it is also effective as a wave embankment that suppresses shaking when a ferry boat is docked. This reduces the waves without hindrance when the ship is docked and enables safe docking and safe handling of people and vehicles thereafter. Of course, it is only necessary to operate the device for the required time, so energy consumption can be limited.

In the present invention, energy can be supplied by using ordinary commercial power, but energy generated by wave power generation or the like can also be used. With this energy, it is possible to supply it when needed, and it seems that the location is close. Further, in the present invention, the wave is not extinguished unless water is sent, and it can be extinguished only when necessary.

[0018]

As described above, according to the present invention, water is jetted to the sand ground layer on the sea floor to liquefy the sand so that the wave is dissipated. Wave-dissipating can be effectively achieved without constructing a structure, and the cost can be greatly saved, and there is no risk of obstructing the movement of tidal currents and fish. In addition, since there is no part above the sea surface, it does not adversely affect the landscape, and water can be sent only when necessary to dissipate the wave, thus reducing operating costs.

Further, the present invention can be used in combination with a conventional wave-dissipating facility. For example, if it is applied to a port opening,
Invasion waves into the port can be reduced without hindering the navigation of vessels. Furthermore, it can be effectively used as a wave removing means for suppressing the sway when a ferry boat is docked.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a vertical sectional view showing another embodiment.

FIG. 3 is a measurement diagram of a wave-dissipating state according to an experiment of the present invention.

[Explanation of symbols]

 1 Water pipe 2 Jet hole 3 Sand ground layer 4 Pump 5 Frame structure 6 Seabed ground

Continued Front Page (72) Inventor Hironobu Miura 3-1-1 Nagase, Yokosuka City, Kanagawa Prefecture

Claims (2)

[Claims] 1. Liquefaction of sand, characterized in that water is injected into the sand layer of the sea floor to liquefy the sand, and the fluidization of the sand absorbs wave energy to attenuate the wave height. Wave breaking method. 2. A frame-shaped structure having a required area is installed on the seabed, a sand ground layer is formed therein, and water is injected into the sand ground layer to liquefy the sand. , A method of extinguishing waves by sand liquefaction, characterized in that wave energy is absorbed and wave height is attenuated by fluidization of sand.