JPH0739646B2 - Wave control structure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a wave control structure used as a breakwater or a breakwater.

(Prior Art) Conventionally, structures such as concrete caisson are often used as breakwaters and breakwaters. These structures are simply rectangular shapes, trapezoidal shapes for the purpose of reducing wave force, curved surfaces such as circles, and even water that allows waves to penetrate inside and consume energy due to disturbance. Various types, such as those having an internal space such as a part, have been proposed.

These structures are installed directly on the rubble mound on the ocean floor or directly on the ocean floor, and most of them are subject to horizontal sliding force and vertical lifting force due to waves due to their own gravity or the gravity of sand or stone packed inside. I try to make them oppose.

(Problems to be Solved by the Invention) Generally, the wave control structure installed on the seabed is subjected to horizontal sliding force and vertical lift force by the progress of waves. On the other hand, there are some conventional wave control structures as described above that reduce the horizontal force received from the waves by devising the upper shape, but the lifting force acting on the bottom plate of the structure As the area of the bottom slab becomes larger, the weight must be heavier in order to prevent slipping and tipping due to wave force, which results in a larger structure and higher construction costs. There was a problem that it became longer.

On the other hand, since the lifting pressure increases as the acting bottom area increases, it is conceivable to provide an opening in the bottom plate of the wave control structure to reduce the lifting pressure.

However, unless the opening ratio is considerably increased, the effect of reducing the lifting pressure cannot be expected, but on the other hand, the negative effects such as the reduction of sliding resistance and the reduction of structural strength due to the reduction of the bank weight due to the opening are significant. The idea of providing a bottom plate opening for the purpose of pressure reduction was regarded as unrealistic.

It is an object of the present invention to reduce the aperture ratio of the through holes of the bottom slab sufficiently to reduce the weight of the bank, to reduce the structural strength to a practically small amount, and to reduce the lifting pressure to a negligible level. More specifically, even if it is relatively lightweight, the horizontal force component acting as a sliding force decreases because the wave force acts in the center direction of the circle, and the vertical force component increases the sliding resistance. In the semi-arc type wave control structure, the lifting force due to waves is reduced to a negligible level while maintaining the required structural strength, so there is no need to increase the weight even when the bottom area is large. It is intended to do so.

(Means for Solving Problems) A feature of the present invention for solving the above-mentioned conventional problems and achieving the intended purpose is that a wave control wall having a substantially semi-arcuate shape is formed on the bottom slab 11. In the wave control structure having the structure body 10 having the water repellent part of the internal space 15 on the rubble mound 14 on the seabed, the bottom plate 11 is provided with a plurality of through holes, and the whole through holes are provided. The aperture ratio of 5 to 20% of the area of the bottom plate 11
%.

(Operation) In the wave control structure of the present invention, the wave force acting on the outer surface of the semicircular arc-shaped main body is concentrated in the center direction of the arc, and the horizontal force component acting as the sliding force is reduced and the vertical force component is reduced. Increases sliding resistance.

Therefore, the weight of the structure can be reduced, the thickness of the bottom plate becomes thin, and the inner space formed by the bottom plate 11 and the wave control wall 12 is reduced.
There will be a water retention section in 15. Since the bottom slab is thin, even if there is an opening, the weight reduction of the bank is small. Further, as the wave progresses, the wave pressure acting on the bottom surface is dispersed and absorbed from the opening of the through hole, so that the lifting pressure acting on the bottom surface of the structure body is reduced, and the wave control structure from the opening of the through hole is reduced. The wave pressure that has entered the water repellent part of the body acts downward on the upper surface of the bottom plate, resisting the lifting pressure that pushes up the structure and cancels it. The effect of reducing the lifting pressure is drastically reduced to less than 20% when there is no opening even if the aperture ratio of the through hole is at most 5% of the bottom plate.
It was confirmed by the following experiment that the attenuation was almost zero at -20%, that is, the attenuation was negligible.

In addition, when the opening ratio is about 10%, special bottom plate reinforcement is not required even for a large ground reaction force acting on the bottom plate during large waves. When the aperture ratio is about 20%, special bottom plate reinforcement is not required when used in a place where only small and medium waves act, and some bottom plate reinforcement is used when used in a place where large waves come in. Is required, but does not require significant reinforcement. On the other hand, when the aperture ratio is 20% or more, a large bottom plate reinforcement is required to resist the large waves, the total weight increases, the manufacturing cost increases, and the practicability becomes low.

(Example) Next, the Example of this invention is described in drawing.

FIG. 1 shows an embodiment of the present invention. This wave control structure has a structure body 10 having a wave control wall 12 in a substantially semi-circular shape on a bottom slab 11 on a rubble mound 14 formed on a seabed 13. The space 15 with a semicircular cross section is formed inside,
The whole space is a water repellent part. This structure body 10
Is a cylindrical wave control wall as the waves progress from the front side.
Since the force in the traveling direction of the wave that acts on the outer surface of 12 acts in the center direction of the cylinder and the structure body 10 is pressed against the bottom surface side, a structure that can counter the wave force even if the whole is lightweight. There is.

In the bottom plate 11 of the structure body 10, a large number of through holes 16, 16 ... Which communicate with the internal space 15 are opened, and the lifting pressure is reduced by the above-mentioned action, so that the weight of the structure is further reduced. It is possible and has an economical structure.

Next, description will be given of an experimental example in which a model similar to the structure of the embodiment shown in FIG. 1 was used to confirm the reduction of the lifting pressure acting on the bottom plate by providing the bottom plate with a through hole.

Fig. 2 shows the experimental water depth (h) at the embankment installation position (h) of 35 cm, embankment semicircle radius of 25 cm, embankment upright height of 5 cm, mound thickness of 10 cm,
When the opening ratio (εb) of the bottom slab is changed to 0%, 5%, 10% and 20% under the condition of mound coating thickness of 10.7 cm and a random wave with a significant wave period (T) of 2.6 seconds is applied. The horizontal axis represents the wave height (H) of the passing wave at the position where the structure is installed, and the vertical axis represents the lifting pressure (Pu) at the front toe of the embankment corresponding to the wave height. It shows the relationship of pressure. In addition, the lift force in the case of having an opening (εb> 0) is a value obtained by subtracting the downward force acting on the upper surface of the bottom plate. The plotted data are average wave height, significant wave height, 1/10 maximum wave height and maximum wave height, average wave pressure, 1/3 maximum wave pressure, 1/10 maximum wave pressure and maximum wave height for three wave groups with different wave trains. Wave pressure was used.

From this figure, it is possible to reduce the lifting pressure to a little less than 20% when there is no opening and to an almost negligible level when the opening is 10% by providing an opening with an opening of 5% at the bottom. Recognize. At an opening ratio of 10%, the lifting pressure becomes almost zero, and at an opening ratio of 20%, a similar tendency is seen.

Figures 3 and 4 show the results of sliding experiments when the experimental water depth (h) was 30 cm and the other structural conditions were the same as in Figure 2. The experiment uses a random wave with a significant wave period (T) of 2.6 seconds, and 5 for each of three different wave groups.
Waves with significant wave height were applied to measure the amount of movement of the levee body. Moreover, the weight (W) of the bank is 3 of 40 kg, 45 kg and 50 kg.
It was a kind. The horizontal axis of the figure is the maximum wave height (H) passing through the bank, and the vertical axis is the cumulative sliding amount (S) when about 250 waves are applied. In Fig. 3, the bottom plate has holes. If not, Fig. 4 shows the case where the bottom plate has an aperture ratio of 20%.

From these figures, it can be seen that when there is a hole in the bottom slab, the wave height at which the levee begins to slide increases, and the amount of sliding also becomes smaller than when there is no hole. This is due to the effect of reducing the lifting pressure, which is because the force for lifting the dam body is reduced and it becomes difficult for the dam body to move.

By providing the opening in the bottom slab in this manner, the lifting pressure is reduced, and the stability of the bank can be significantly improved.

(Advantages of the Invention) As described above, in the wave control structure of the present invention, a plurality of through holes are opened in the bottom plate of the structure body having the wave control wall in a substantially semi-arc shape, and the aperture ratio is 5% of that of the bottom plate. By setting it to ~ 20%, the upward lift force acting on the bottom surface due to the progress of waves is dispersed and absorbed in the openings of the through holes, and is reduced, and the wave pressure that has entered the water retaining space from the through holes is the upper surface of the bottom slab. Since it acts downwardly to resist the lifting pressure, the weight for resisting the lifting pressure can be reduced. In the design, the bottom plate opening ratio is 10% and the lifting pressure is almost negligible. If the opening ratio is about 10%, there is no practical problem because the decrease of the bank weight and structural strength due to the opening is small. Can be said. The structure, which is originally light and difficult to slide, can be further reduced in weight, and the manufacturing and installation costs thereof can be further reduced and the construction period can be shortened.

[Brief description of drawings]

FIG. 1 is a partial perspective view of an embodiment of the wave control structure of the present invention, and FIGS. 2 to 4 are graphs showing the results of experimental examples. 10 …… Structure body, 11 …… Bottom plate, 12 …… Wave control wall, 13
...... Sea floor, 14 …… Rubble mound, 15 …… Space, 16 …… Through hole.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (71) Applicant 999999999 Toa Construction Industry Co., Ltd. 5 Yonbancho, Chiyoda-ku, Tokyo (71) Applicant 999999999 Toyo Construction Co., Ltd. 5-1, Koraibashi, Higashi-ku, Osaka-shi, Osaka (71) Applicant 999999999 PS Co., Ltd. Marunouchi, Chiyoda-ku, Tokyo 3-4-1 (71) Applicant 999999999 Wakatsuki Construction Co., Ltd. 1-4-7 Hamacho, Wakamatsu-ku, Kitakyushu, Fukuoka (72) Inventor, Masaru Tanimoto Yokosuka, Kanagawa 3-1-1 Nagase Inside the Port Technology Research Institute, Ministry of Transport (72) Inventor, Jiro Okumura 5-41-5 Shonan, Takatori, Yokosuka City, Kanagawa Prefecture (72) Nobutaka Namekawa, 3-25-16 Shibahara, Urawa City, Saitama Prefecture (72) ) Inventor Makoto Sawahata 1-20-13-102 Natsumidai, Funabashi City, Chiba Prefecture (72) Inventor Fumiaki Hashizume 253-18 Castle, Sakura City, Chiba Prefecture (72) Inventor Kazuhiko Sakai Higashimurayama, Tokyo Ontacho 5-36-4-210 (72) Inventor Kobori Kyosei 80-16 (72) Inventor Toshiaki Nakamura Oshima, Koto-ku, Tokyo 4-5-11-805 (72) Invention Person Naohiro Koga 1-1-19-2-309 Higashibayashi Sagamihara City, Kanagawa Prefecture (72) Inventor Keisumi Ishimaru 1300-2 Kamihideya, Okegawa City, Saitama Prefecture Inventor Kunio Funada 4-1-20 Natsumi Funabashi City, Chiba Prefecture ―301 (72) Inventor Masayuki Akama 4-5-2 Fukuei, Ichikawa City, Chiba Goyo Construction Bank Toku Dormitory (72) Inventor Tsunehiro Sekimoto 4-18-1 Gyotoku No. 1 Condominium No.502, Gyotoku Station, Ichikawa City, Chiba Prefecture

Claims (1)

[Claims] 1. A wave control structure having a wave control wall 12 having a substantially semi-circular arc shape on a bottom slab 11, and a structure body 10 having a water retaining portion of an internal space 15 installed on a rubble mound 14 on the seabed. 2. The wave control structure according to, wherein the bottom plate 11 is provided with a plurality of through holes, and the aperture ratio of the whole through holes is set to 5% to 20% of the area of the bottom plate 11.