JP2013124536A - Breakwater structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an effective and appropriate breakwater structure capable of developing a breakwater function against large-scale tidal waves as persistently as possible.SOLUTION: The breakwater structure uses a levee body 15 constructed with a number of caissons 10 arranged neighboring one another for developing a breakwater function against large-scale tidal waves. The caissons each consist of a cylindrical external structure 11 and a cylindrical or circularly columnar internal structure 12 having a smaller diameter than it. The internal structure is arranged coaxially inside the external structure to secure a planarly annular wave absorbing space 13 therebetween. At least in the outer peripheral face of the external structure facing the sea side, a slit 14 is formed to cause the inflow of tidal waves through the wave absorbing space. The external structure and the internal structure are installed while being each supported by supporting piles 16 driven into a submarine ground, to hold their self-standing states while precluding the horizontal displacement against the wave power of assumed-scale tidal waves.

Description

  The present invention relates to a wave preventing structure as a wave preventing facility against a large-scale tsunami.

  There are various structures and forms of breakwaters, seawalls, and revetment structures as wavebreak structures against tsunamis. For example, Patent Document 1 and Patent Document 2 describe a wave breaker caisson having a wave-dissipating function. I have a suggestion.

JP 2002-275855 A JP 2002-309540 A

  By the way, the conventional breakwater was damaged by the tsunami more than expected due to the Great East Japan Earthquake, and the damage was seriously caused. The tsunami was repeatedly pushed several times. It is thought that the original function was not able to be demonstrated with respect to the tsunami after the 2nd wave because it was damaged by the wave.

  Specifically, for example, in a caisson-type breakwater as shown in FIG. 3, each caisson 1 slides in the first tsunami wave to create a gap between adjacent caisons, and a strong water flow is generated in the gap. This further facilitated the sliding of the caisson 1 and the scouring of the mound 2, and it was thought that the caisson 1 was finally tilted or overturned.

  This also applies to the case of the wave-dissipating caisson shown in Patent Document 1 and Patent Document 2, and in any case, the current wave-breaking structure does not have a sufficient wave-breaking function against a tsunami exceeding the assumed scale. The actual situation is that urgent measures are required.

  In view of the above circumstances, an object of the present invention is to provide an effective and appropriate wave-breaking structure capable of exhibiting a wave-breaking function as strongly as possible even for a large-scale tsunami.

  The present invention is a wave-breaking structure having a wave-breaking function against a large-scale tsunami by a dam body constructed by arranging a number of caisons adjacent to each other, and the caisson includes a cylindrical external structure, A state in which the outer structure has an inner structure having a cylindrical or columnar shape having a smaller diameter than that of the outer structure, the axis of the outer structure being in the vertical direction, and the top is at a position higher than the wave height of at least an assumed scale tsunami In addition, the inner structure is coaxially arranged inside the outer structure to secure a ring-shaped wave-dissipating space in plan view between the outer structure and the inner structure. A slit for allowing a tsunami to flow into the wave-dissipating space through the wave-dissipating space is formed at least on an outer peripheral surface facing the sea side of the external structure, and the external structure and the internal structure are connected to the seabed. Drive into the ground And characterized by being installed sliding impossible and by inverting non supported by the support piles.

  Since the breakwater structure of the present invention is installed by supporting a double-structured caisson composed of an external structure and an internal structure by a support pile, it is large enough to overflow a dam body constructed by these caissons. Even if a large tsunami is received, individual caissons themselves will not slide or fall and be damaged, and the tsunami that reaches the caisson will flow into the wave-dissipating space from the slits and can exhibit a wave-dissipating function. Therefore, the wave-breaking structure of the present invention can maintain the wave-breaking function with respect to the tsunami repeatedly rushing and can surely obtain a disaster-reducing effect.

It is a side elevation view which shows schematic structure of the wave-proof structure which is embodiment of this invention. FIG. It is a figure which shows the destruction mechanism by the tsunami of the conventional common caisson type breakwater.

One Embodiment of the wave-proof structure of this invention is shown in FIGS.
This is installed as a breakwater against a large-scale tsunami, and is assumed to be about once every 1000 years, not only for tsunamis with a probability of occurring once every 100 years (level 1 class tsunami) Even when a larger tsunami (level 2 class tsunami) is generated, the structure is such that the wave-proof function can be maintained as firmly as possible without being destroyed.

Specifically, as shown in FIG. 2, the wavebreak structure of the present embodiment is mainly composed of a series of dam bodies 15 constructed by joining a plurality of caissons 10 arranged adjacent to each other without gaps. However, each caisson 10 is in the form of a hollow double structure, and the caisson 10 is mainly supported by the support pile 16 and installed on the seabed ground.
In the case of the illustrated example, in order to securely join adjacent caissons 10, a flat surface is formed at the contact portion between both external structures 11, and the flat surfaces are in close contact with each other. However, the form of joining of the caissons 10 is arbitrary.

  The caisson 10 in the present embodiment includes an external structure 11 having a cylindrical shape and an internal structure 12 having a columnar shape having a smaller diameter than that of the external structure 11, and the axis of the external structure 11 is set in the vertical direction. As a vertically placed posture, the top is installed on the bottom of the sea in a state that is higher than the wave height when a tsunami of the assumed scale (this embodiment assumes a tsunami of level 1 class at least) In addition to being disposed on the mound 17, the internal structure 12 is coaxially disposed inside the external structure 11, and the wave-dissipating space 13 having an annular shape in plan view is formed between the external structure 11 and the internal structure 12. Is ensured.

  A large number of slits 14 communicating with the inner extinguishing space 13 are formed at intervals in the circumferential direction on at least the outer peripheral surface of the external structure 11 facing the sea side, and is constructed by the caisson 10 as a whole. The tsunami that has reached the series of levee bodies 15 can flow into the wave-dissipating space 13 in each caisson 10 from the slits 14.

  Further, a conventional caisson type breakwater is usually installed by simply disposing each caisson on the mound, but in this embodiment, both the external structure 11 and the internal structure 12 are on the mound 17. As shown in FIG. 1, the caisson 10 is installed not only simply but also firmly supported by a large number of support piles 16 driven into the submarine ground. It is surely prevented from slid to the land side or toppling over the wave force.

According to the breakwater structure of the present embodiment based on the above-described configuration, not only for the assumed scale, for example, a level 1 class tsunami, but also for a larger tsunami (for example, a level 2 class tsunami). It is possible to perseverely exhibit an excellent wave preventing function without being easily damaged or destroyed.
That is, the wave-breaking structure of this embodiment is constructed with these caissons 10 because both the outer structure 11 and the inner structure 12 in each caisson 10 are supported by the support piles 16 as described above. The caisson 10 immediately slides even if it receives a large wave force from a level 2 class tsunami that overflows a series of levee bodies 15 or if the mound 17 is scoured. It will not be damaged or destroyed by overturning. Therefore, it can maintain a wave-proof function persistently against tsunamis that repeatedly push in, and a disaster reduction effect can be obtained with certainty.

  Moreover, the tsunami that has reached the caisson 10 flows into the wave-dissipating space 13 from the slits 14 formed in the external structure 11, and the waves that have flowed into the wave-dissipating spaces 13 from the slits 14 collide with each other. In the wave-dissipating space 13, the waves are distributed to the left and right and flow around the inner structure 12, and the flow from both sides collides violently on the back side (land side) of the wave-dissipating space 13. By generating such a flow in the inside, the tsunami energy can be effectively attenuated and the wave-absorbing function can be surely exhibited, and the disaster mitigation effect can be sufficiently expected.

  Although the embodiment of the present invention has been described above, the above embodiment is merely a preferred example, and the present invention is not limited to the above embodiment. For example, appropriate modifications and applications as listed below are possible. Is possible.

Although it is realistic that the structure of the external structure 11 and the internal structure 12 constituting the caisson 10 is made of steel or reinforced concrete, it is not particularly limited.
Further, the internal structure 12 is not limited to a solid columnar shape as in the above embodiment, and may be a hollow cylinder similar to the external structure 11 when desired strength is obtained.
In any case, it is preferable to set the structure, form, shape, and dimensions of the external structure 11 and the internal structure 12 so that the entire caisson 10 can withstand a level 2 class tsunami. What is necessary is just to design optimally according to the assumed scale of a tsunami and the required wave prevention performance.

  Similarly, steel piles, PC piles and other arbitrary structures can be used for the support piles 16, but in any case, the support piles 16 support the caisson 10 reliably and are resistant to level 2 class tsunamis. However, it is preferable to be able to prevent the sliding and overturning, so that the structure, diameter size, required number, installation interval, depth of penetration into the submarine ground, etc. are optimally designed so that this is possible. Just do it.

  In the above embodiment, the slit 14 is provided only on the outer peripheral surface of the outer structure 11 on the sea side. However, the formation position of the slit 14, its shape and size, and other configurations are arbitrary, and include, for example, the land side. It is also conceivable to form the slits 14 over the entire circumference of the external structure 11. In that case, in the case of a large-scale tsunami that causes overflow, the tsunami that flows into the wave-dissipating space 13 flows out from the slit 14 on the land side, but the tsunami simply flows over the dam body 15. The effect of attenuating the tsunami energy passing through the narrow wave-dissipating space 13 can be expected.

In addition, it is conceivable that the internal structure 12 is also formed in a hollow cylindrical shape and slits 14 are formed on the outer peripheral surface thereof. In this case, the positional relationship between the external structure 11 and the slits 14 provided in the internal structure 12 is appropriately set. By doing so, it is conceivable that the wave-dissipating space 13 in the caisson 10 is not only circular, but the wave-dissipating effect is further enhanced as the wave-dissipating space 13 in which a more complicated water flow occurs.
Furthermore, it is also conceivable that the tsunami energy is released upward by providing a slit 14 or an appropriate opening at the top of the caisson 10 and ejecting the wave flowing into the caisson 10 upward.

  In addition, although the said embodiment is an example in the case of installing the breakwater structure of this invention offshore as a breakwater, of course, the breakwater structure of this invention may be installed in a coast part as a tide wall or a breakwater structure. Needless to say, it is possible and the scale of the tsunami is arbitrary.

DESCRIPTION OF SYMBOLS 10 Caisson 11 External structure 12 Internal structure 13 Wave-dissipating space 14 Slit 15 Bank body 16 Support pile 17 Mound

Claims (1)

It is a wave-breaking structure having a wave-breaking function against a large-scale tsunami by a dam body constructed by arranging a number of caisons adjacent to each other,
The caisson comprises a cylindrical outer structure and a cylindrical or columnar inner structure having a smaller diameter than the outer structure,
The external structure is installed on the sea bottom with the axis being the vertical direction and the top being at a position higher than the wave height of at least the assumed scale tsunami, and the internal structure is coaxial with the external structure To ensure a ring-shaped wave-dissipating space in plan view between the external structure and the internal structure, and at least an outer peripheral surface facing the sea side of the external structure leads to the wave-dissipating space. Forming a slit to allow the tsunami to flow into the wave-dissipating space,
A wave-proof structure characterized in that the outer structure and the inner structure are installed so as not to be slidable and toppling over by a support pile driven into the seabed ground.

Images