JPH0819648B2 - Wave-dissipating structure - Google Patents

Description

The present invention relates to a wave-dissipating structure installed on a coastal dike or an offshore structure.

“Prior Art” Conventional wave-dissipating structures of this type are those in which a deformed block is tilted and piled up in front of a coastal breakwater or breakwater, that is, on the side on which waves enter, so that the waves are extinguished. It has been known.

"Problems to be Solved by the Invention" However, the conventional wave-dissipating structure has the following problems.

(I) When installing a deformed block in a place where the depth of water is large, a large amount of construction cost is required, and construction is impossible in reality.

(Ii) It is difficult to apply to permeable structures (such as curtain wall bank).

(Iii) In order to build a wave-dissipating structure by stacking odd-shaped blocks, it is necessary to incline the transverse cross section into a substantially trapezoidal shape in order to stabilize the wave-dissipating structure, and the space cannot be used effectively. , It is impossible to berth a ship.

(Iv) Scour may occur on the front of the embankment or breakwater, and the deformed block may sink.

The present invention has been made in view of the above problems, and can be constructed at a lower construction cost than that of a conventional deformed block, and can be applied to a permeable structure, and is easy. It is an object of the present invention to provide a wave-dissipating structure capable of effectively utilizing a space without damaging the ship and allowing a ship to berth.

[Means for Solving the Problems] In order to solve the above problems, the present invention horizontally arranges at least one wave-eliminating plate in which holes or slits are formed in a wall surface below the water surface of a front surface of a seawall or a breakwater. It is characterized by being provided in the state.

[Operation] According to the wave-breaking structure of the present invention, when the water particles moving up and down in the vicinity of the wall surface of the coastal leve hit a wave-breaking plate horizontally provided on the wall surface, a part of the water-hole is a hole of the wave-breaking plate. By passing through the inside, a large turbulence (vortex) is generated near the upper and lower surfaces of the wave-eliminating plate, and as a result, the reflected wave energy is efficiently dissipated and the wave-eliminating action is performed.

[Examples] Hereinafter, the present invention will be described with reference to FIGS. 1 to 5. FIG. 1 shows a first embodiment of the present invention, which shows a wave-dissipating structure built on the coast.

In the figure, reference numeral 1 is a coastal embankment, and on a wall surface 1a below the water surface, wave-eliminating plates 2 and 2 extending along it are horizontally fixed in two stages. The wave-eliminating plate 2 is composed of a porous wall or a slit wall having a large number of holes (or slits) 2a, 2a, ...

Then, when the wave is incident on the wave-dissipating structure as described above, the following wave-dissipating action is performed.

Generally, on a wall 1a that is impermeable to waves, such as a coastal levee or a normal breakwater, overlapping waves are formed on the front surface of the wall 1a due to the invasion of waves. The motion of water particles in this overlapping wave is
As shown in the drawing, the belly (N point) is excellent in the vertical direction, and the node (0 point) is excellent in the horizontal direction. Then, the antinode of the wave (N point) is located at the wall surface 1a portion, and the water particles in the vicinity move up and down in the vertical direction along the wall surface 1a.

Therefore, in the wave-dissipating structure of the present invention, when the water particles that move up and down hit the wave-dissipating plates 2 and 2 horizontally provided on the wall surface 1a, a part of the holes 2a and 2a of the wave-dissipating plate 2 are formed. ... By passing through the inside, a large turbulence (vortex) is generated in the vicinity of the upper and lower surfaces of the wave-eliminating plate 2, and as a result, the reflected wave energy is efficiently dissipated, which causes the wave-eliminating action. Will be done.

Therefore, the wave-breaking structure of the present invention, unlike the conventional wave-breaking plate vertically installed, because the wave-breaking plate is installed in the horizontal direction orthogonal to the movement of water particles, the wave-breaking efficiency is enhanced, In addition, it does not need to be tilted and clogged up like a deformed block, it is economical and difficult to break, it can effectively utilize the space, and it is possible to berth a ship. It has effects such as being able to be installed in a permeable structure.

Next, the second embodiment of the present invention will be described with reference to FIGS.
An example will be described.

The present embodiment is a wave-breaking structure constituted by combining a wave-breaking plate with a permeable breakwater (airtight curtain wall dam) provided by the present applicant earlier. The same components as those shown are designated by the same reference numerals.

Reference numeral 3 in the figure denotes a permeable breakwater, and this permeable breakwater has two wall portions 4 and 4 extending in parallel in a direction intersecting with the direction of wave propagation, and both of these wall portions 4. It has a side wall portion (not shown) that closes both ends in the horizontal direction and a top plate portion 5 that closes the upper end, and has an air layer A sealed inside, and the side of the wave incident side On the wall surface 4, along the extending direction of the wall surface 4, three wave-dissipating plates 2,2,2
Is fixed horizontally. The permeable breakwater 3 and the wave-eliminating plate 2 are supported by a large number of piles 6, 6, ... That are deeply driven into the subseabed ground G, so that the upper part of the permeable breakwater 3 is above the water surface. It is exposed at the bottom and the lower part is below the surface of the water. Of course, the wave-eliminating plate 2 has a large number of holes 2a, 2a, ...

Here, the operation effect of the permeable breakwater 3 provided by the present applicant will be briefly described below. When a wave propagates across the permeable breakwater 3, the internal air layer A causes a change in the water surface. Depending on whether it is compressed or expanded, it acts as a damper. That is, when the water surface inside the permeable breakwater 3 rises, the air is compressed and tries to push the water surface downward, and conversely, when the inside water surface drops, the air A expands and tries to raise the water surface. It is designed to attenuate the energy of the waves that are going to be transmitted.
Therefore, the transmitted wave that has passed through the permeable breakwater is smaller than the incoming wave, and compared with the conventional curtainwall without a closed air layer, which has the same width of the levee body and the draft depth of the curtainwall. The transmittance can be lowered. However, on the other hand, there is also a problem that the reflectance may increase.

Therefore, in the wave-dissipating structure of the second embodiment, three wave-dissipating plates 2, 2, 2 are horizontally provided on the wall surface 4 of the transparent breakwater 3 to reduce the reflectance and the energy. This is intended to increase the loss rate.

Here, a model experiment was conducted on the second embodiment shown in FIG. 3, and the data obtained by this is shown in FIGS. 4 and 5.

First, in FIG. 3, reference symbol L is the wavelength of the incoming wave, B1 is the length of the wave breaking plate 2, B2 is the length of the transparent breakwater 3, and B is B1 and B2.
And h are added together, h is the water depth of the sea near the structure installation, h2 is the draft depth of the curtain wall, and ε is the aperture ratio of the wave-eliminating plate 2 (= hole area / wave-eliminating plate Area).

The model used in this experiment was set with B / h = 1.2 and h2 = 0.5h, and three wave-eliminating plates with ε = 0.3 were used. Furthermore, in CASE.1, B1 / h = 0.2, B2 / h = 1.0 In CASE.2, B1 / h = 0.5 and B2 / h = 0.7 are set.

By transmitting the incoming waves with different waveforms L to the model whose numerical values are set in this way, the B / L as shown in Fig. 4 can be obtained.
And the energy loss K _L ² and the relationship between B / L and the reflectance K _R as shown in FIG. 5 could be obtained. Then, the following conclusions can be drawn from these data.

Regarding the transmittance, there was almost no difference between CASE.1 and CASE.2, but when CASE.2, that is, the long wave-dissipating plate 2 was used, the energy loss rate K _L ² was It is high and the reflectance K _R is low, and it can be seen that the reflected energy is efficiently dissipated by the wave-eliminating plate 2. Thus, if the length B1 of the wave-eliminating plate 2 is set to about half the water depth h or more, the wave-eliminating structure of the present invention has a sufficient wave-eliminating function within the range of the substantial wave period. Becomes

Therefore, in the second embodiment, in addition to being able to lower the wave transmittance as compared with the conventional curtain wall bank without a closed air layer, the reflected energy is efficiently dissipated, The reflectance of incoming waves can be lowered, and an ideal wave-dissipating effect can be achieved.

Of course, the same effect as the first embodiment can be obtained.

"Effects of the Invention" As described above, the present invention is one in which at least one wave-dissipating plate having holes or slits is provided in a horizontal state on a wall surface below the water surface on the front surface of a coastal dike or breakwater. , The wave-eliminating plate becomes orthogonal to the movement of water particles to enhance the wave-eliminating efficiency, and there is no need to incline and stack it like a deformed block, which is economical and hard to break, and also makes effective use of space. It is possible to carry out the above, and it is possible to berth a ship, and it is possible to install it on a transparent structure such as a curtain wall bank.

Furthermore, the wave-dissipating structure combined with the transmissive structure can reduce the transmittance of incoming waves and efficiently dissipate reflected energy to lower the reflectance of incoming waves. It is possible to perform ideal wave cancellation.

[Brief description of drawings]

1 and 2 show a first embodiment of the present invention. FIG. 1 is a side sectional view of a wave-dissipating structure in which a wave-dissipating plate is installed on a coastal levee, and FIG. 2 is a shore. FIGS. 3 to 5 are views for explaining water particle motion of overlapping waves near the breakwater, and FIGS. 3 to 5 are views showing a second embodiment. FIG. 3 shows that a wave-eliminating plate is installed in front of a transparent breakwater. FIG. 4 is a side sectional view of the wave-dissipating structure, FIG. 4 is a diagram showing the relationship between the incoming wave and the energy loss rate, and FIG. 5 is a diagram showing the relationship between the incoming wave and the reflectance. 1 ... Coastal levees, 2 ... Breakwater plates, 2a ... Holes or slits, 3 ... Transparent levees.

Claims (1)

[Claims] 1. A wave-dissipating structure characterized in that at least one wave-dissipating plate having holes or slits is horizontally provided on a wall surface below the water surface of a coastal breakwater or a breakwater.