JP3461264B2 - Wave-dissipating structure - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wave-dissipating structure utilizing wave breaking efficiently. 2. Description of the Related Art As a wave breaking structure utilizing wave breaking, a step-like horizontal plate having the deepest portion on the offshore side disclosed in Japanese Patent Application Laid-Open No. 4-289310 is disclosed.
No. 18 includes a parallel inclined plate, and Japanese Unexamined Patent Publication No. 4-136311 discloses a method in which a breaking submerged breakwater is installed on the open sea side of the main body. [0003] The wave control and coastal maintenance method using an artificial reef including a submerged embankment or a breakwater as shown in FIG. 1 actively breaks waves by using breaking waves. It is excellent in principle in terms of points and has many advantages. However, current artificial reefs and breakwaters do not always have sufficient wave-dissipating function. For this reason, the improvement of the wave-dissipating function has been attempted by increasing the cross-section of the artificial reef as described in the section of the prior art and increasing the permeability of the embankment body. Although various devices have been devised to achieve the required wave energy dissipation, they have not been able to exert a sufficient effect, resulting in problems in economy and stability of the embankment. [0004] In order to solve these problems and develop the artificial reef method into a drastic wave control and coastal conservation method, the wave breaking function based on the breaking wave, which is the principle of this method, is improved, and the breaking wave becomes more aggressive. It is necessary to utilize it on a regular basis. Rather than simply increasing the cross-sectional data, it is necessary to generate breaking waves that can achieve the required wave attenuation. [0005] However, the wave-breaking structure that has been developed so far and effectively utilizes the wave breaking does not significantly improve the wave-breaking function. Means for Solving the Problems A wave-dissipating structure is a double-leaf structure having a lower leaf and an upper leaf which are two upper and lower stages, a trap portion having a slit structure is provided on the upper leaf, and a jet by a composite breaking wave is provided. Is injected into the trap portion, thereby suppressing the cancellation of the wave-dissipating effect due to the wave-forming action caused by the splash and the horizontal vortex generated by the intrusion of the powerful jet of the composite breaking wave. [0008] The present invention will be described below based on numerical simulations and hydraulic experiments. Numerical Simulation Single Leaf In FIG. 2, h ₁ represents the water depth, and R ₁ represents the top height of the single leaf. Numerical simulations were performed using the boundary integration method (BIM) to clarify the changes in the breaking wave shape and jet size when a solitary wave was incident on this single leaf. In the calculation, the relative crown height (R ₁ / h ₁ ) of the single leaf is set as a parameter and 0.25 to 0.5.
Changed to 90. One example of the calculation results is shown in FIGS. These are the waveform changes of the winding wave breaking wave and the winding wave breaking wave, respectively. Further, in order to clarify the relationship between the jet scale, the wave height water depth ratio (H ₁ / h ₁ ) of the incident wave, and the height of the top of the reef on a single leaf, as shown in FIG. On the other hand, the jet length and height were set, and based on this, the jet size index (β ₅ ) was defined as shown in equation (1). Embedded image The relationship between the jet size index (β ₅ ) and the single leaf relative top height (R ₁ / h ₁ ) is expressed by the wave height ratio (H ₁
/ H ₁ ). FIG. 5 shows the result. Maximum value at the jet size reference (beta ₅₎ occurs under the crest depth ratio of each of the incident wave (H ₁ / h _1), wave height depth ratio of the incident wave (H ₁ / h
_{When 1} ) is 0.5, the jet size index (β ₅ ) becomes the maximum value. This means that the jet size index (β ₅ ) of the breaking wave does not exceed the upper limit of 0 even if the wave height ratio (H ₁ / h ₁ ) of the incident wave and the height of the top of the reef (R ₁ ) are changed under a single leaf. .05 is present, indicating that no more jets will occur. In the wave-eliminating structure shown in FIG. 6, X ₁ represents the length of the lower leaf, R ₁ represents the top height of the upper leaf, and R ₂ represents the top height of the lower leaf. . Numerical simulations were also performed on the breaking wave when solitary waves were incident on this double leaf. In the calculation, the relative top height (R ₁ / h ₁ ) of the upper leaf is fixed to 0.8, the relative top height (R ₂ / h ₁ ) of the lower leaf is 0.3 to 0.5, and the lower leaf is The relative length to the water depth (h ₁ ), that is, the step interval (X ₁
/ H ₁ ) is changed from 0.0 to 23.0, and the wave height ratio (H ₁ / h ₁ ) of the incident wave to the leaves is 0.1 to 23.0.
4, 0.5 and 0.6 standing solitary waves were launched. FIG. 7 showing the calculation results confirms the occurrence of breaking waves with waveform changes not found in the conventional classification. This breaking wave is caused by the combination of the steepened main wave peak and the secondary wave peak, instead of the development of the secondary wave peak in front of the main wave peak, which replaces the main wave peak. The feature lies in the shape of the complex wave peak, like a crown, and the powerful jet emission from it. The breaking wave that remarkably develops the jet by the combination of the main wave peak and the secondary wave peak is referred to as a composite breaking wave here. Further, in order to clarify the waveform characteristics at the breaking limit and the jet drop limit of the composite breaking wave, the same incident wave having a wave height water depth ratio (H ₁ / h ₁ ) of 0.5 is applied to the relative crest height (R). FIG. 8 shows a comparison between a double leaf having an upper leaf of ₁ / h ₁ ) of 0.8 and a single leaf having the same top height as that of a single leaf. As is apparent from FIG. 8, the characteristic is clearly shown in the coronation waveform at the time of the breaking limit, which characterizes the composite breaking wave. In addition, the jet size of the wound wave type breaking wave at this time is almost close to the upper limit of the jet generated on the single leaf as can be seen from FIG. 5, and the jet size of the combined wave breaking type greatly exceeds this. From these results, the tip of the leaf is a two-step consisting of the lower leaf 1 and the upper leaf 2, and the step interval (X ₁ / h ₁ ), which is the relative length to the water depth of the lower leaf, is about 6.5. Thereby, the breaking wave type can be made into a complex type breaking wave, and a strong jet can be generated. Hydraulic Experiments The generation of complex breaking waves will be described with hydraulic experiments together with numerical simulations. Experimental conditions Using a two-dimensional wave water tank with a length of 65 m, a width of 1 m and a depth of 1.6 m, which is glass-coated on one side, the top of the upper leaf (R ₁ ) is 26.0 cm in the water tank and the top of the lower leaf is 26.0 cm. Edge height (R ₂ ) is 13.0 cm, length of lower leaf (X ₁ ) is 250.0
cm double steel leaf model was installed, 16 wave height meters were installed as shown in FIG. 9, and the water depth (h ₁ ) was 31.0.
cm, and generated a stationary solitary wave having a wave height (H ₁ ) of 13.0 cm. Spatial waveforms before and after the breaking limit were recorded by a high-speed video camera (manufactured by NAC, 200 frames / second) and analyzed to determine the image. Experimental Results It was confirmed that the same composite breaking wave as that obtained by the numerical simulation was generated. Spatial waveforms at the breaking limit and jet fall limit of the composite breaking wave obtained by image analysis were compared with those obtained by numerical simulation under the same conditions. As a result, for the steep coronal wave peak and the powerful jet that characterize the complex breaking wave,
Both the experimental results and the numerical calculations show good agreement. The feature of the compound breaking wave is that a strong jet is generated by combining the main wave peak and the secondary wave peak. In particular, it is characterized by the jet size at the breaking wave limit. As described above, in the conventional breaking wave generated by a single leaf, there is an upper limit in the value of the jet size index (β ₅ ) according to the wave height water depth ratio (H ₁ / h ₁ ) of the incident wave, and the relative top of the leaf It is clear from the numerical calculation that even when the height (R ₁ / h ₁ ) is increased, breaking waves exceeding the upper limit are not generated. Therefore, a breaking wave exceeding 0.05 which is the upper limit of the jet size (β ₅ ) in the conventional breaking wave is a tentative standard regarding the generation of the composite breaking wave. Conditions for Generating Complex Wave Breaking on Double Leaf For a solitary wave incident on a double leaf with the relative top height (R ₁ / h ₁ ) of the upper leaf fixed at 0.8, The generation conditions were examined. The size of the breaking wave and jet on the double leaf is determined by the step interval (X ₁
/ H ₁ ), the jet size index (β ₅ ) and the step interval (β ₅ ) when the relative top height (R ₂ / h ₁ ) of the lower leaf is changed to 0.3 to 0.6. X ₁ / h ₁ ) was examined. FIG. 10 shows the result, which shows the step interval (X ₁ / h ₁ ) and the relative top height (R) of the lower leaf.
Regardless of the value of ₂ / h ₁ ), in each case, the jet size index (β ₅ ) is the maximum value 0.05 for a single leaf with a relative top height (R ₁ / h ₁ ) of 0.8. , And the composite leaf is always generated by the double leaf having two steps, so that the wave breaking effect can be obtained. Upper leaf relative crest height when the (R ₁ / h ₁₎ is 0.8, step interval (X ₁ / h ₁₎ is approximately 4.5 and the lower leaves of the relative crest height (R ₂ / h ₁₎ Is from 0.4 to 0.5, it is possible to generate a composite type breaking wave with a jet nearly three times as large as the largest jet in the conventional breaking wave. The optimal value of the step interval (X ₁ / h ₁ ), which is the interval between the lower leaf and the upper leaf, is related to the breaking point position by the lower leaf, and the jet size is set when the upper leaf is set slightly before this breaking point. Is the largest. FIG. 11 illustrates this fact.
The distance (δx) from the wave breaking point by the lower leaf to the step position of the upper leaf (a negative sign means that the upper leaf is before the wave breaking point by the lower leaf, that is, offshore) and the jet size index (β ₅ ) Are shown for incident waves with wave height water depth ratios (H ₁ / h ₁ ) of 0.4, 0.5 and 0.6, respectively. From this figure,
It can be seen that when the step is installed about 2 h ₁ before the breaking point by the lower leaf, a composite breaking wave with the largest jet occurs. Wave Height Attenuation Characteristics of Composite Wave Breaker 1) Wave Height Change The difference in wave height change after wave breaking due to the difference in wave breaking formula under the wave height depth ratio (H ₁ / h ₁ ) of the same incident wave. For the sake of clarity, the wave height ratio (H ₁ / h ₁ ) of the incident wave is 0.30,
The solitary waves of 0.42 and 0.55 were converted to the relative crown height (R ₁ /
h ₁ ) are 0.43 and 0.85, and the relative leaf height (R ₁ / h ₁ ) of the upper leaf is 0.
85 in the lower leaves of the relative crest height (R ₂ / h ₁₎ is 0.4
3. Step interval between lower leaf and upper leaf (X ₁ /
h ₁ ) are respectively incident on the 8.06 double leaves,
The change in wave height at that time was investigated. In this case, since the reflectivity differs depending on the condition of the leaf, the change in the wave height after breaking is normalized by the maximum wave height (H _max ) before each breaking limit, and the dimensionless distance (X ₂ / h) from the tip of the leaf. ₁ ) (for double leaves, the distance X ₂ from the top leaf tip) was compared. On the double leaf, even at the measurement point W16 (see FIG. 9), the attenuation is still advancing and in the transient state, the wave height there is set as the transmitted wave height (H _T ), and this is the maximum wave height (H _max ) on the leaf. the difference with obtaining the pulse height attenuation height (H _max -H _T) of the ratio to the maximum height (H _max) (1
−H _T / H _max ) was defined as the attenuation rate, and the effect of the crushing waveform equation on this attenuation rate was examined. Relative top height of single leaf (R ₁ / h ₁ )
Is 0.85, the winding-type breaking wave generated on the single leaf and the relative top height (R ₁ / h ₁ ) of the upper leaf are 0.85, and the relative top height (R ₂ / h ₁ ) of the lower leaf is ) Is 0.
43, step interval (X ₁ / h ₁₎ is shown in Figure 12 which was compared with the attenuation factor _{(1-H T / H max} ) by composite breaking waves on the double leaf 8.06. [0026] In the same leaf, but the damping factor increases with wave height depth ratio of the incident wave regardless of breaking format (H ₁ / h _1), wave height depth ratio of the incident wave (H ₁ / h ₁₎ is 0 .42, the attenuation rate of the composite breaking wave (1-H
_T / H _max ) is increased by about 15%, and the wave height attenuation occurs at an early stage after the wave breaking (where the propagation distance of the wave tip is small) due to the generation of the composite wave breaking. The wave height at the measuring point W16 where the transmittance and the reflectivity X ₂ are the longest is defined as the transmitted wave height (H _T ).
This defines the transmittance (K _T = H _T / H ₁ ) as a ratio to the incident wave height (H ₁ ). On the other hand, the reflectivity at stations W01 to (K _R), defined as the ratio H _R / H ₁ and wave height of the reflected waves in W01 point (H _R) and incident wave height (H _1), the crushed form The differences in reflectivity based on the differences were discussed. FIG. 13 shows the peak-to-depth ratio (H ₁ / H) of the incident wave.
h ₁₎ the relative crest height the solitary wave of 0.30,0.42 and 0.55 (R ₁ / h ₁₎ 0.85 single leaf,
And, the lower leaves of the relative crest height (R ₁ / h ₁₎ is 0.8
5, the upper leaf relative crest height (R ₂ / h ₁₎ is 0.43,
The transmittance (K _T ) and the reflectance (K _R ) are shown when the light is incident on a double leaf having a step interval (X ₁ / h ₁ ) of 8.06. Rolling wave breaking on a single leaf,
On the double leaf, complex breaking waves have appeared. In the case of a single leaf, the reflectance (K _R ) is 0.31 for an incident wave having a wave height water depth ratio (H ₁ / h ₁ ) of 0.42,
The transmittance (K _T ) is 0.37, whereas the reflectance (K _R ) is 0.2 for a double leaf having a smaller cross section.
The transmittance (K _T ) has decreased to 0.28. Further, the wave height water depth ratio (H ₁ / h ₁ ) is 0.5
For the incident wave of _No. 5, the transmittance (K _T ) is reduced to 0.24, and the peak height water depth ratio (H _T / h ₁ ) of the transmitted wave can be suppressed to about 0.13. As described above, even under the condition of the same incident wave and the height of the top of the leaf, the step is not one step (single leaf), but the step interval (X ₁ / h ₁ ) is about 8.06. By using a two-stage step (double leaf) having the following, not only the reflectance (K _R ) can be reduced, but also the transmittance (K _T ) can be reduced with the occurrence of the composite breaking wave. The wave breaking effect due to the generation of splash and horizontal vortex generated by the intrusion of a strong jet in the trap-type double leaf method combined breaking wave cancels out the wave-dissipating effect. On the other hand, the leaves have a slit structure in order to convert the jet rush into only the generation of strong vortex diffusion (see FIG. 14). As shown in FIG. 14, the trap portion having the slit structure is formed by arranging plates at an interval with respect to a traveling direction of a wave. This slit structure captures the generated jet and suppresses its wave-making action. When the optimized water depth (h ₁ ) of the trap portion is fixed at 31.0 cm and the incident wave is a solitary wave, the peak height water depth ratio (H ₁ / H) of the incident wave is used.
h ₁ ) are 0.28, 0.40, 0.44 and 0.50
In the case where a Knoid wave is incident, the dimensionless period (see Equation (2)) is set to 20, and the wave height water depth ratio (H
₁ / h ₁ ). Embedded image The top of the lower leaf (R ₂ ) is fixed at 13.2 cm, the top of the upper leaf (R ₁ ) is fixed at 26.3 cm, and the step interval (X ₁ / h ₁ ) of the leaves is 0.0, 3.23. , 8.06,
In addition to changing the breaking wave formula in five ways of 8.89 and 9.53, the dimensionless horizontal distance (X ₂ / h ₁ ) from the end of the upper leaf to the offshore end of the trap is 1.61,
The relationship between the jet rush and the position of the trap portion was examined by changing to 3.23 and 4.07. For comparison, an experiment was conducted in which the slit structure of the trap portion was changed to crushed stone having a particle size of 5 to 10 mm, and a rubber film having a thickness of 1 mm was attached to the trap portion and the lower portion was hollow. It was carried out. These waveform changes are
Measurements were made with 16 wave gauges (see FIG. 15), and the state of splash and horizontal vortex generation at the time of jet rush was observed with three video cameras (manufactured by NAC, 200 frames / second).
FIG. 16 shows a case in which a solitary wave with a peak height water depth ratio (H ₁ / h ₁ ) of 0.44 for a double leaf and a trap portion is provided (the step interval X ₂ / h _{1 of the} upper leaf is 4.
07) and a comparison of waveform changes when the light is incident on a case having no trap portion. Up to W05, which coincides with the breaking point, the waveforms in both cases are identical except for the reflection part. In the waveform on the shore side from W07 (W07 to W16 in FIG. 15), the wave height attenuation effect of the trap portion appears in the entire waveform. FIG. 17 shows a case in which a cunoid wave having a peak water depth ratio (H ₁ / h ₁ ) of an incident wave of 0.44 is incident on a trap type double leaf. According to this, although the breaking point fluctuates due to the return flow from the reef, the wave height attenuation on the shore side from the measuring point W09 after passing through the trap portion is abrupt, and is compared with the solitary wave in FIG. However, it can be seen that the damping effect is large. In other words, in the case of a cunoid wave, the effect of the return flow is added, and the wave elimination is promoted, and the wave elimination effect is remarkable. FIG. 18 shows a spatial change of the wave height ratio (H / H ₁ ) at each measurement point after breaking of the solitary wave and the cunoid wave. In the case of a solitary wave (indicated by a circle in the figure), the trapping effect appears more clearly in the region on the shore side (X / h ₁ > 12.1) than the offshore end of the trap portion. Further, in the case of the Cunoid wave (indicated by a triangle in the figure), the value of the peak height ratio (H / H ₁ ) is less than 0.1 when X / h ₁ > 30, and the peak height attenuation is more remarkable than in the case of the solitary wave. is there. Note that X is a shore-facing coordinate with the step position of the lower leaf as the origin. FIG. 19 shows that when the position of the upper leaf is changed, the peak height water depth ratio (H ₁ / h ₁ ) of the incident wave is 0.44, and the trap portion from the end of the upper leaf is changed. Dimensionless distance to the offshore end (X ₂ /
FIG. 9 shows changes in the transmittance (K _T ) and the reflectance (K _R ) of a solitary wave when h ₁ ) is 4.07. The figure also plots the case without the trap portion. The transmission rate (K _T ) in the case of having the trap portion is smaller than that in the case of not having the trap portion. In the case where the step interval (X ₁ / h ₁ ) at which the most developed complex type breaking wave is 8.06, the transmissibility (K _T ) without the trap portion is about 0.3, When the portion is provided, the wave-elimination effect becomes remarkable, and the transmissivity decreases to about 0.22. Further, the leaf step interval (X ₁ /
By providing a trap portion having a slit structure in a region where h ₁ ) is 3.2 to 9.5, wave elimination is effectively performed.
The reflectance (K _R ) is determined by the step interval (X ₁ / h) between leaves.
₁ ) decreases with the increase of the leaf step interval (X ₁ /
When h ₁ ) is 8.06, the minimum value is 0.2. When the trap portion is provided, the reflectivity (K _R ) of the region where the step interval (X ₁ / h ₁ ) of the leaf is greater than 3.23 is 0.02 to 0.0 compared to the case where the trap portion is not provided.
It has increased by about three. This is because the return flow from the trap develops the reflected wave. FIG. 20 shows the relationship between the entry point of the jet and the position of the end off the trap.
As the step interval (X ₂ / h ₁ ) increases, the transmissibility (K _T ) decreases uniformly. This indicates that the propagation distance of the breaking wave destination on the upper leaf after the jet enters is related to the wave extinction efficiency. For comparison of the trap structure, the trap portion was replaced with a slit structure and A: crushed stone having a particle size of 5 to 10 mm and B: 1 mm in thickness
An experiment was conducted in which a rubber film was placed on the top end of the trap portion and the lower portion was hollow. For hydraulic experiments,
Step interval the maximum scale of the jet occurs (X ₁ / h ₁₎
Is 8.06, and the dimensionless horizontal distance (X ₂ / h ₁ ) is 3.2.
At the position 3, a trap having a different structure as described above was installed. These waveform changes were measured with 16 wave gauges, and 3
A video camera (manufactured by NAC, 200 frames / second) was used to observe the state of splash and horizontal vortex generation at the time of jet entry, and to compare the relationship between the transmissibility (K _T ) and the structure of the trap section. FIG. 21 shows the result.
In the case of the crushed stone (marked by X in FIG. 21) and the rubber film (marked by □ in FIG. 21), no difference is recognized in the transmissibility (K _T ) between the two, but the trap portion is not provided in both (FIG. 20).
The transmission rate (K _T ) is larger than that of Solid-reef). This means that at the moving floor boundary and the movable boundary of the rubber film that move or deform due to the jet rush, the powerful jet rush is absorbed by the deformation of the boundary surface, and the vortex diffusion development due to the rush occurs. Restrained,
It is considered that the transmission rate is rather increased. As a result of the above experiment, no effect can be obtained even if the trap portion is simply a permeable structure such as rubble, and a slit structure having a jet trapping function is optimal. Application Example A case where the wave-dissipating structure of the present invention is constructed on a steep shore where shore protection is carried out by a breakwater or artificial reef as shown in FIG. I do. In order to break the waves to be controlled at the desired position, a double reef that functions as a wave-dissipating function integrated with the original terrain will be constructed. As the structure type of the lower leaf, an appropriate one such as a leaf, a submerged bank, a submerged horizontal plate, and a swash plate can be selected. Further, an upper leaf for generating a secondary wave is constructed. At the entry point of the jet on the upper leaf, a trap portion having a slit structure is provided. As a result, as shown in FIG.
It restores shallow beaches to steep eroded beaches, improves beach stability and seawater purification ability, and creates a rich beach environment. Furthermore, since a water area with high calmness is created between the wave-dissipating structure of the present invention and the beach, a place suitable for marine recreation can be provided. The trap section also functions as a fish reef. In addition, oxygen is supplied by the breaking wave jet, which increases dissolved oxygen, and becomes a favorable environment for biological growth. Become a spot. Further, as shown in FIG. 23, when the present invention is applied to a nourishment work or an artificial beach on a gently sloping beach, it is possible to achieve a higher wave-dissipation efficiency than when conventional artificial reefs and submerged levee are installed. Fine sand is supplied to the shore, and the particle size of the sand beach can be reduced. In other words, it not only enhances the purification function of the beach and the satisfaction in use, but also creates a comfortable beach. By making the leaf a double leaf, not only the reflectance (K _R ) can be reduced, but also the transmittance (K _T ) can be reduced with the occurrence of the composite breaking wave. . Therefore, the wave-dissipating structure in which the composite type breaking wave is generated on the double leaf effectively performs the wave-dissipation, and has a great effect of wave extinction. By providing a trap portion at the portion where the strong jet of the generated composite breaking wave enters, the generation of splash and horizontal vortex is suppressed, the wave is prevented from being regenerated, and the entry of the jet is used to generate strong vortex diffusion. Can be converted. For this reason, the generated jet is caught and its wave-making action is suppressed, so that wave extinction is effectively performed.
Further, when the trap portion has a slit structure, a remarkably large wave canceling effect can be obtained. The wave-dissipating structure of the present invention overcomes the weak point of low wave-dissipating efficiency while retaining the advantages of the conventional artificial reef construction method. By installing the wave-dissipating structure of the present invention on the shore where it has been considered difficult to control waves with artificial reefs and submerged levees, it is possible to obtain a more effective control effect than the detached levee. As a result, it is possible to restore a shallow shore on a steeply eroded coast, enhance the stability of the shore and purify the seawater, improve the sandy beach environment, and create a rich beach environment. In addition, the creation of a calm water area can secure an optimal place for marine recreation. Further, when the present invention is applied to a beach nourishment or artificial beach, the particle diameter of the sand beach can be made smaller than that of the conventional reef or submergence due to the high wave-dissipating efficiency, and the purification function and utilization of the sand beach can be improved. Satisfaction can be increased. If a slit structure is provided in the trap section, it functions as a fish reef, and in addition, the supply of dissolved oxygen increases with the intrusion of a powerful jet. Diversity can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a conventional wave breaking type wave breaking structure. FIG. 2 is a side view of a single-leaf wave-absorbing structure. FIG. 3 is a diagram showing a relationship between a change in wave height of a solitary wave on a single leaf and a height of a leaf top end; FIG. 4 is a diagram illustrating the length and height of a jet at the time of a jet drop limit. FIG. 5 shows a jet size index and a wave height ratio (H) of an incident wave.
₁ / h ₁ ) and a diagram showing a relationship between a leaf top end height. FIG. 6 is a side view of the double-leaf wave breaking structure. FIG. 7 is a diagram showing a waveform change of a composite breaking wave on a double leaf. FIG. 8 is a comparison diagram of a change in wave height when the same incident wave is made incident on a single leaf and a double leaf having the same height. FIG. 9 is a schematic diagram of a water tank in which a hydraulic experiment was performed. FIG. 10 is a diagram illustrating a relationship between a jet size index, a step interval, and a top height of a lower leaf. FIG. 11 is a diagram showing a relationship between a distance from a breaking point to a step position of an upper leaf and a jet size index when only the lower leaf is used. FIG. 12 is a diagram showing a relationship between a peak height water depth ratio (H ₁ / h ₁ ) of an incident wave and an attenuation rate. FIG. 13 is a diagram comparing the reflectance and the transmittance of a single leaf and a double leaf. FIG. 14 is a perspective view when a trap portion has a slit structure. FIG. 15 is a schematic diagram of a water tank in which a hydraulic experiment was performed on a wave-dissipating structure having a trap portion. FIG. 16 is a diagram comparing waveform changes accompanying a compound breaking wave when a solitary wave is made incident. FIG. 17 is a waveform change diagram of a Knoid wave on a trap type double leaf. FIG. 18 is a diagram showing a change in wave height after breaking a Knoid wave. FIG. 19 is a diagram showing a relationship among a transmittance, a reflectance, and a step interval. FIG. 20 is a diagram showing the relationship between the transmission rate and the position of the offshore end of the trap section. FIG. 21 is a diagram illustrating a relationship between a transmissivity and a trap unit structure. FIG. 22 shows an example of application to a steep beach. FIG. 23 shows an example of application to beach nourishment. [Description of Signs] 1 Lower leaf 2 Upper leaf 3 Trap unit having a slit structure

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Hidemi Rikuta               6-41 Prince, Hayatahigashicho, Gifu City, Gifu Prefecture               Apartment Higashicho 2 (72) Inventor Akihide Tada               2570-4 Shimotsuruma, Yamato City, Kanagawa Prefecture (72) Inventor Tadashi Fukumoto               2570-4 Shimotsuruma, Yamato City, Kanagawa Prefecture                (56) References JP-A-4-11107 (JP, A)                 JP-A-4-289310 (JP, A)                 Japanese Utility Model Showa 54-172891 (JP, U)

Claims (1)

(57) [Claims 1] A double-leaf wave-dissipating structure comprising a lower leaf and an upper leaf, wherein a trap portion having a slit structure is provided on the upper leaf, and a jet by a composite type breaking wave is trapped by the trap portion. Wave-dissipating structure designed to rush into