JP3457755B2 - Transmission type wave-breaking structure - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the creation of a calm water area in a harbor and the reduction of waves entering a water intake or discharge port of a thermal power plant along the coast. The present invention relates to a transmission type wave-dissipating structure. 2. Description of the Related Art It is necessary to provide a pier or marina in a harbor, to build an aquaculture farm, or to increase the operation rate of offshore construction work or to protect moored structures. It is necessary to secure the calmness of the water area by installing a wave-dissipating structure in the water area. Normal gravity breakwaters not only have limitations in terms of cost as the water depth increases, but they also negate the replacement of water inside and outside the water area,
It may be restricted from the viewpoint of environmental consideration. In the case where the water depth is relatively large or when the exchange of water inside and outside the water area is emphasized, the use of a transmission type wave-absorbing structure that does not completely shield in the water depth direction has been considered. FIGS. 9 and 10 show examples of a conventional transmission type wave-absorbing structure. FIG. 9 is a side view of a wave-absorbing structure of a type called a curtain wall, in which a vertical plate structure a is arranged so as to penetrate the water surface and reach halfway of the water depth. This type of wave-dissipating structure reduces the propagation of waves behind by blocking the movement of water particles by waves near the surface, and penetrates deeper into deeper waves for longer wavelength waves. This will be dealt with by increasing the amount. When the transmission coefficient Ct (the ratio between the transmitted wave height Ht and the incident wave height Hi, Ht / Hi) as an index of the wave extinction performance is to be suppressed to 0.5 or less, the amount of penetration of the curtain wall is 1/7 times the wavelength. It has been found to be necessary. Therefore,
For example, for a wave having a period of 4 seconds and a wavelength of 25 m, a penetration amount of less than 4 m may be sufficient, but for a wave having a period of 8 seconds and a wavelength of 100 m, a penetration amount of 14 m is required. The scale becomes large. Water areas with large tidal range will be even larger. Also, when the penetration amount increases, the exchange of water inside and outside the water area becomes worse, and the transmission type function is not performed. Furthermore , although the transmission coefficient is small for frequently occurring short-period waves, reflected waves cannot be ignored, and hinder the navigation of ships and workboats in waters where incident waves and reflected waves are superimposed on the front of the curtain wall. There is also a problem that comes. FIG. 10 is a side view of a type of wave-breaking structure called a submerged horizontal plate type, in which a horizontal plate structure b is completely submerged near the water surface. This type of wave-absorbing structure consumes wave energy by using the flat plate to block the movement of water particles, breaking waves on the flat plate, or creating vortices at the end of the flat plate In the case where a wave having a long wavelength is to be eliminated, it is necessary to increase the width of the flat plate accordingly. To suppress the transmission coefficient to 0.5 or less, the width of the flat plate becomes smaller than the wavelength. 1 /
3 to 1/4 is required. Therefore, there is a disadvantage that the width of the plate becomes close to 30 m with respect to a wave having a wavelength of 100 m, and the structure becomes extremely large. Further, when the tide level difference is large, there is also a problem that the depth of submersion at a high tide level becomes large, and the wave elimination performance is deteriorated. [0005] As described above, in the conventional transmission type wave-absorbing structure, in order to exhibit a wave-absorbing effect on a long wavelength wave, the scale becomes large and the cost is reduced. There is a disadvantage that it causes an increase. In addition, the water permeability may be deteriorated as the scale becomes larger. In the case of a curtain wall, the influence of the reflected wave cannot be ignored. Further, in a water area where the tide level difference is large, the curtain wall becomes larger, and in the case of a submerged horizontal plate type, the wave-dissipating performance deteriorates at a high tide level. SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned problems, and has a structure of a much smaller scale than a conventional one for long wavelength waves while maintaining good water permeability. To obtain a sufficient wave-dissipating effect,
It is an object of the present invention to provide a transmission-type wave-dissipating structure capable of reducing reflected waves and responding to tide level fluctuations. [0007] In order to achieve the above-mentioned object, a transmission type wave-dissipating structure of the present invention is provided on a support frame which is erected on the seabed and allows seawater to pass therethrough, and is provided on the support frame. It has a submerged horizontal plate that is supported and located below the water surface . Further, the transmission type wave-absorbing structure of the present invention is characterized in that
Includes a submerged horizontal plate supported by the support frame and located below the water surface
With that, near the end of the wave lower or wave upper Dobotsusui horizontal plate is extended in a direction substantially perpendicular to the traveling direction of the incoming wave, the temperature toward the waves downward so as to penetrate the water surface It is characterized in that an inclined plate that inclines is provided upright. According to the transmission type wave-absorbing structure of the present invention described above, the incoming wave propagating on the water surface is reflected by the vertical flat plate once trying to pass along the upper surface of the submerged horizontal plate. return over the submerged horizontal plate, then the operation of gradually passes under the submerged horizontal plate. Then, if the return wave and an operation following a reverse path described above. In this way, a part of the wave is delayed in phase, and a part of the energy of the wave is consumed by moving the water on the submerged horizontal plate, so that the transmitted wave is attenuated. Further, by raising the vertical flat plate to the lower side of the wave, the apparent horizontal width B of the submerged horizontal plate changes in accordance with the change of the submerged depth d, and B / d is not so large with respect to the tide level fluctuation. Will not change . Embodiments of the present invention will be described below with reference to the drawings. 1 is a perspective view showing a transmission type wave-dissipating structure as a reference example, FIG. 2 is a graph showing the wave-elimination performance of the transmission type wave-dissipation structure of FIG. 1 with respect to regular waves, and FIG. It is a graph which shows the wave elimination performance with respect to the irregular wave of a wave structure. FIG. 4 is a perspective view showing a transmission type wave-dissipating structure as one embodiment of the present invention, and FIG. 5 is a side view of the transmission type wave-dissipation structure of FIG. (B) shows the correlation with the water surface at the time of high tide. FIG. 6 is a graph showing the wave-damping performance of the transmission-type wave-damping structure of FIG. 4, and FIG. 7 is a graph showing the wave-damping performance of the transmission-type wave-damping structure having a vertical flat plate. FIG. 8 is a perspective view showing a transmission type wave canceling structure as a reference example. First, a transmission type wave-absorbing structure as a reference example shown in FIG. 1 will be described. Reference numeral 1 denotes an immersed horizontal plate disposed at a depth d below the water surface. A wave-dissipating structure is formed by the water horizontal plate 1 and the vertical flat plate 2 erected at the wave-lower end of the submerged horizontal plate 1, which is erected on the seabed so as to allow the permeation of seawater. Supported by the support frame 4. In this way, the vertical flat plate 2 has the incoming wave W
Of the submerged horizontal plate 1 and a width (B) of the submerged depth d of the submerged horizontal plate 1.
/ B) is set to about 1/2 to 1/3. A plurality of partition plates 3 for connecting the submerged horizontal plate 1 and the vertical flat plate 2 are arranged side by side with an interval along the traveling direction 5 of the incoming wave W. Each partition plate 3 is formed in a right-angled triangular shape having an oblique side 3a obliquely moving from near the upper edge of the vertical flat plate 2 to near the edge of the submerged horizontal plate 1. In addition, the support frame 4 is configured by an elongated member such as a steel frame or an iron pipe, thereby increasing water permeability. Here, the longitudinal direction 6 of the wave-dissipating structure is arranged orthogonal to the traveling direction 5 of the incoming wave W. FIG. 1
The symbol B in the middle denotes the width of the submerged horizontal plate 1 and the symbol D denotes the vertical plate 2
The symbol s indicates the freeboard portion of the vertical flat plate 2 and the symbol 10 indicates
Indicates the water surface, respectively. Since the transmission type wave-dissipating structure of this embodiment is constructed as described above, the incoming wave W
Is an operation of once passing along the upper surface of the submerged horizontal plate 1, being reflected by the vertical flat plate 2, returning above the submerged horizontal plate 1, and then passing under the submerged horizontal plate 1. Do
You . Then, if the return wave and an operation following a reverse path described above. In this way, a part of the wave is delayed in phase, and a part of the energy of the wave is consumed by moving the water on the submerged horizontal plate 1, so that the transmitted wave is attenuated. Also, when the vertical flat plate is erected near the wave-up end of the submerged horizontal plate, the transmitted wave is sufficiently attenuated by the synergistic action of the vertical flat plate 2 and the submerged horizontal plate 1 on the wave. become. When a plurality of partition plates 3 connecting the submerged horizontal plate 1 and the vertical flat plate 2 are arranged in parallel with each other in parallel with the traveling direction of the wave, the above-mentioned wave along the submerged horizontal plate 1 is formed. The movement is performed smoothly, and the strength of the connection between the submerged horizontal plate 1 and the vertical flat plate 2 is increased. The partition plate 3 is formed in a right-angled triangular shape having an oblique side 3a obliquely inclined from near the upper edge of the vertical flat plate 2 to near the edge of the submerged horizontal plate 1. The mounting strength of the vehicle can be appropriately maintained. FIG. FIG. 3 shows a wave-dissipating performance curve for a regular wave obtained by a simulation calculation or a water tank experiment. The horizontal axis represents the wavelength λ of the incoming wave (regular wave) made dimensionless by the width B of the submerged horizontal plate 1, and the vertical axis represents the transmission coefficient of the wave. FIG. 2 shows a case where the ratio between the depth d and the width B of the submerged horizontal plate 1 is 1/3, and the maximum value of the wavelength λ when the transmission coefficient is less than 0.5. Is 18 times the width B of the submerged horizontal plate 1. FIG. 3 shows a case where the ratio between the depth d and the width B of the submerged horizontal plate 1 is １ ／, but the maximum value of the wavelength λ at which the transmission coefficient is 0.5 or less is It is about 12 times the width B of the horizontal water plate. From these facts, the immersion level of the immersed horizontal plate 1 changes due to the tide level change, and the ratio of d to B becomes 1/2.
Even when changing in the range of 1/3, for example, the period is 8 seconds,
For an incoming wave having a wavelength of 100 m, a submerged horizontal plate 1 having a width of about 8 m and a submergence depth of about 2.7 to 4 m requires only a fairly small wave-breaking structure. When the period is 6 seconds and the wavelength is 56 m, the width may be about 5 m, and the period is 12 seconds and the wavelength is 225
For m, the width needs to be about 20 m. In the present embodiment, the submerged horizontal plate 1 and the vertical flat plate 2 are simple plates. However, a steel plate structure having a certain thickness or a block structure covered with concrete can be used . Further, although intended shown sectional shape of the submerged horizontal plate 1 and the vertical flat plate 2 has a L-shape, permissible even slightly protrudes from the submerged horizontal plate 1 or the vertical flat plate 2 Absent. While still in the illustrated example provided with a vertical flat plate 2 to the end of the wave under side of the submerged horizontal plate 1, the same effect can be obtained with waves upper it is confirmed by calculations and experiments. In the case where the vertical flat plate 2 is provided at the end on the wave upper side of the submerged horizontal plate 1, the incoming wave is indicated by a symbol W 'in FIG. Here, the above-mentioned submerged horizontal plate 1 and vertical plate 2
The principle of the wave-dissipating action in the transmission type wave-dissipating structure of the reference example constituted by the above will be described. When the water depth is large, the wavelength λ of the wave is expressed by the equation [1] using the wave period T. Λ = (gT ² ) / (2π) where g is the gravitational acceleration and π is the pi. On the other hand, when the water depth is very small, the wavelength λh considering the effect of the water depth h is: [Expression 2] is represented by the following equation. Λh = T√ (gh) Therefore, the shorter the water depth, the shorter the wavelength. In the reference example, the energy of the incident wave is dissipated by utilizing the so-called resonance phenomenon that occurs on the submerged horizontal plate, in which the antinode of the wave occurs on the front surface of the vertical flat plate and the node of the wave occurs at the other end of the submerged horizontal plate. , The transmission coefficient is reduced. That is, when the wavelength on the immersed horizontal plate is four times the width of the immersed horizontal plate, Equation 3 is obtained. Equation 3] 4B = lambda _d where λd is the wavelength of the submerged horizontal plate, B is a submerged horizontal plate width [0023] In the structure format transmission wave dissipating structure described above, on the submerged horizontal plate Then, since the apparent water depth h is regarded as being the submersion depth d of the submerged horizontal plate, the water depth h in [Equation 2] is replaced with d, and is substituted into [Equation 3].
When the relationship between the width B and the wave period T at the time of resonance is obtained, [Equation 4]
The formula holds. T = (4B) / √ (gd) Equation 4 is an approximate equation that does not take into account the movement of water outside the other end of the submerged horizontal plate. Is considered to be the following corrected [Equation 5]. T = (α4B) / √ (gd) Since the water outside the other end of the submerged horizontal plate works as a mass, the resonance period needs to be corrected longer, and therefore α is a value larger than 1. It is thought to be. In the offshore wave (incoming wave), Equation 1 is established between the wave period and the wavelength.
Eliminating T by the equation yields Equation 6 after all. Λ / B = {(8α ² ) / π} · (B / d) For example, if α is 1.5, B / d is 2
In this case, a resonance phenomenon occurs when λ / B is about 11.5. In other words, a structure having a width of about 1/12 or less with respect to the wavelength of the incoming wave can exhibit the wave canceling performance. Since the exact solution of α is unknown,
When the fluid phenomena around the structure was estimated using a numerical calculation method, when B / d was about 2 to 3,
α was found to be between 1.4 and 1.5. In this way, in the transmission type wave-absorbing structure of the reference example, a space with one side opened to create a resonance phenomenon is created by combining the vertical flat plate and the submerged horizontal plate, and furthermore, the submerged horizontal plate is submerged. by shortening the length of the wave by a shallow depth, it can be erased have long wave compared to the size of the structure. When the B / d is increased so as to be effective for a wave as long as possible, a wave having a short wavelength is easily transmitted. Based on experimental results and the like, B / d is preferably 2-3, and considering the freeboard portion s and the tide level difference, the width (ie, B) of the submerged horizontal plate 1 is equal to the height of the vertical flat plate ( The sum of d and freeboard s = D) is slightly more than 1-2 times appropriate.
Also, from the principle, it is significant that the vertical flat plate 2 is placed at the end of the submerged horizontal plate 1, and it may be on the upper side or on the lower side. According to the equation (6), as B / d increases, the longer the wavelength, the more effective the wavelength becomes, but the shorter the wavelength becomes, the easier it is to transmit. / D is selected. However, in a water area where the tide level fluctuates greatly, the submersion depth d of the horizontal plate changes, so that the B / d fluctuates depending on the tide level. No. Therefore, a transmission type wave-dissipating structure improved to cope with tide level fluctuation is an embodiment of the present invention described below. Next, a transmission type wave canceling structure as one embodiment of the present invention will be described with reference to FIG. As shown in FIG. 4, the transmission type wave-dissipating structure of this embodiment includes a submerged horizontal plate 11 that is disposed under the water surface 10 and is submerged.
And a sloping plate 12 erected in the vicinity of an end on the lower side of the wave, rising upward toward the lower side of the wave, and supported by a support frame 13 erected on the seabed so as to allow the permeation of seawater. It is configured. The inclined plate 12 is provided so as to be substantially perpendicular to the traveling direction 5 of the incoming wave W and penetrate the water surface. [0031] FIG. 5 (a), the correlation between the tilt plate 12 and the like and water 10 at a low tide (low tide), and FIG. 5
(B) shows a similar relationship during high tide level (high tide), d _L, d _H is submerged sinking depth of the horizontal plate 11 at each low tide and high tide, B _L, B _H is the distance between the inclined plate 12 and the leading edge of the submerged horizontal plate 11 at the water level at low tide and at high tide , respectively. In this embodiment, by the inclined plate 12 is raised inclined toward the waves downward, B _L according to d _L is small compared to d _H is smaller than the B _H, resulting B _L / d _L and B _H / d _H are closer to each other than when they are not inclined. For example, suppose that the tide level difference between low tide (at low tide) and high tide (at high tide) is 2 m, the width B _H of the submerged horizontal plate at high tide is 16 m, and the height of the submerged horizontal plate is 16 m. Submersion depth d _H =
Assuming that 8 m (B _H / d _H = 2) and the inclination angle of the inclined plate = 53 degrees (vertical case is 90 degrees), B _L = 1 at low tide level
4.5 m and d _L = 6 m (B _L / d _L = 2.42).
As shown by the performance curves representing the transmission coefficients at the time of low tide (dashed line in FIG. 6) and at the time of high tide (solid line in FIG. 6), the wave-dissipating performance by numerical calculation is almost the same. It can be seen that the transmission coefficient is 0.36 or less for waves having a wave period of 12.5 seconds or less and a wavelength of 244 m or less regardless of the tide level difference. On the other hand, FIG. 7 shows a calculation result in the case of the reference example in which the inclined plate is 90 degrees. The width B of the submerged horizontal plate is 16 m, and the submerged depth d _H of the submerged horizontal plate. = 8m,
B / d _H = 2 (at high tide), d _L = 6 m, B / d _L = 2.
67 is a performance curve for 67 (at low tide). Comparing the performance curve of FIG. 6 with the performance curve of FIG. 7, there is not much difference at the time of low tide (dashed line in the figure), but at the time of high tide (solid line in the figure) in FIG. On the other hand, although the transmission coefficient is low, the effective wave period region is narrow. Since it is necessary to compare the two in terms of design, it can be concluded that this embodiment has better performance than the transmission type wave-absorbing structure of the reference example. In the transmission type wave-dissipating structure of this embodiment, as in the case of the reference example, even if the inclined plate 12 is provided at the upper end of the submerged horizontal plate 11 at the upper end of the wave, the lower end is provided at the lower end of the submerged horizontal plate. It has been confirmed by calculations and experiments that the same effect as in the case of providing is obtained. Next , a transmission type wave canceling structure as a reference example will be described with reference to FIG. As shown in FIG. 8, the transmission type wave-dissipating structure of this reference example has a submerged horizontal plate 11 that is disposed submerged under the water surface 10, and a wave-lower end of the submerged horizontal plate 11. A vertical flat plate 12a standing near the section and extending substantially perpendicular to the traveling direction of the incoming wave and penetrating the water surface;
1 and a floating body 17a to which both sides of the vertical flat plate 12a are attached, a structure 17 is formed, and the structure 17 is provided with four support frames planted on the seabed so as to allow the permeation of seawater. The leg 16 is supported so that the depth can be adjusted according to the tide level. That is, in the case of this reference example, a depth adjusting mechanism is provided so that the immersion depth of the immersion horizontal plate 11 can be kept substantially constant according to the tide level fluctuation. As a depth adjusting mechanism, for example, a tooth (straight tooth) is formed on the leg 16, a gear meshing with the tooth is built in the structure 17, and the gear is rotated in accordance with a tide level change to raise and lower the structure 17. adjusting performing position include a so-called rack-and-pinion mechanism. In addition to this, the leg 16 is formed in an extendable structure so that the effective length of the leg 16 can be adjusted by a hydraulic jack, and the hydraulic jack is operated according to the tide level to change the length (depth) of the leg 16. ) To adjust the submerged horizontal plate 1
The submersion water depth of the submersible water 1 may be kept substantially constant, or the water depth may be kept constant by the floating body portion 17a of the structure 17, and may be fixed to the leg 16 at every predetermined tide level. [0037] Also in reference example of FIG. 8, as in the embodiment of FIG. 4 described above, even if the vertical flat plate 12a is attached to the vicinity of the wave upper end of the submerged horizontal plate 11, wave lower It has been confirmed by calculations and experiments that the same operation and effect as those provided near the end portion can be obtained. According to the reference example of FIG. 8, in addition to being not affected by the tide fluctuation, for example, referring to FIG.
By changing the submersion depth of the submerged horizontal plate according to the wave period of the entering wave, the better one of the performance curves can be selected, so that a low transmission coefficient can be obtained for short waves and relatively A predetermined transmission coefficient can be obtained even for a long wave. Further, the provision of the structure 17 allows the leg 16 to be lifted and towed as a floating body, so that the installation water area and direction can be easily changed. In the above description, it was shown that the width of the submerged horizontal plate is 16 m and the period is effective up to a wave of about 12 seconds. May be narrower. As described in detail above, according to the transmission type wave canceling structure of the present invention, the following effects and advantages can be obtained. (1) It is possible to reduce transmitted waves with respect to long-wavelength waves with a smaller-scale structure than before, which not only reduces the cost but also the permeability of the flow around the structure, that is, the water inside and outside the water area. And the replacement is improved, and an industrially extremely useful effect can be obtained. (2) Because despite variations always substantially constant wave dissipating effect of the tide is I line, it is suitable as a wave dissipating structure in severe waters tidal fluctuations.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing the entire structure of a transmission type wave canceling structure as a reference example. FIG. 2 is a graph showing the wave-damping performance of the transmission-type wave-damping structure of FIG. 1 with respect to regular waves. FIG. 3 is a graph showing the wave-elimination performance of the transmission-type wave-elimination structure of FIG. 1 with respect to irregular waves. FIG. 4 is a perspective view showing the overall structure of a transmission type wave-dissipating structure as one embodiment of the present invention. 5A is a side view showing a correlation between the transmission type wave-dissipating structure of FIG. 4 and a water surface at a low tide. FIG. (B) is a side view showing the correlation between the transmission type wave-dissipating structure of FIG. 4 and the water surface at the time of high tide. FIG. 6 is a graph showing the wave-damping performance of the transmission-type wave-damping structure of FIG. FIG. 7 is a graph showing the wave-damping performance of a transmission-type wave-damping structure having a vertical flat plate. FIG. 8 is a perspective view showing the entire structure of a transmission type wave-dissipating structure as a reference example. FIG. 9 is a side view showing a curtain wall type as an example of a conventional transmission type wave-absorbing structure. FIG. 10 is a side view showing a submerged horizontal plate type as another example of the conventional transmission type wave-absorbing structure. DESCRIPTION OF SYMBOLS 1,11 Submerged horizontal plate 2 Vertical plate 3 Partition plate 3a Oblique side 4,13 Support frame 5 Traveling direction of incoming wave 10 Water surface 12 Inclined plate 12a Vertical plate 16 Leg 17 as support frame 17 Structure 17a Floating body Part B Width d of submerged horizontal plate 1 Submerged depth W of submerged horizontal plate 1 Incoming wave

Claims (1)

(57) [Claims 1] A supporting frame erected on the seabed to allow permeation of seawater, and a submerged horizontal plate supported by the supporting frame and positioned below the water surface is provided. A sloping plate that extends in the direction substantially perpendicular to the traveling direction of the incoming wave near the bottom or upper end of the submerged horizontal plate, and that rises and falls to the lower side of the water so as to penetrate the water surface A transmission-type wave-absorbing structure, characterized in that a standing wave is provided.