JP2013087546A - Breakwater structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a breakwater structure comprising a fail safe function with which a breakwater function can be presented as persistently as possible without being destroyed even by tsunami exceeding the estimated scale.SOLUTION: On a shore protection structure 11 provided along the shoreline, a slab-shaped levee 12 constituted of a steel plate is installed in such a state as being capable of standing/falling, and a buffering device 13 supporting the levee is interposed between the levee and the shore protection structure. With respect to the wave height in the estimated scale, the buffering device supports the levee against the wave pressure and maintains the standing state of the levee to prevent overflow to the land side. With respect to the wave height exceeding the estimated scale, the buffering device is operated by the wave pressure and the levee falls down to the land side to allow overflow, thereby preventing the levee from being destroyed. The levee is installed while being inclined to the land side with respect to a perpendicular surface in the standing state as a steel plate in a curved slab shape expanded toward the land side, thereby the levee functions as a flared breakwater structure.

Description

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

  As is well known, for example, a flare-type wave-breaking structure as shown in Patent Document 1 and a water-proof facility as shown in Patent Document 2 have been proposed as wave-breaking structures against waves and storm surges.

JP 2007-205129 A JP 2011-1819 A

The Great East Japan Earthquake caused enormous damage due to the occurrence of a large tsunami that exceeded the expected scale. One reason is that the breakwater was destroyed at an early stage and could not function properly.
In other words, a tsunami is a “wave” that repeatedly pushes over several times in the same way as a normal wave, but in the recent earthquake disaster, the breakwater was seriously damaged by the first wave. The wave after the second wave can no longer exhibit its original wave-proofing function, which is thought to have expanded the damage.

Major examples of breakwater destruction mechanisms caused by tsunamis exceeding the expected scale are shown in Figs.
In the case of a general caisson type breakwater, as shown in FIG. 3, the individual caisson 1 slides somewhat in the first wave to create a gap between the caissons, and a strong water flow acts on the gap. It is thought that sliding of caisson 1 and scouring of mound 2 will proceed rapidly, and eventually the entire breakwater will be completely collapsed or destroyed.
In addition, as shown in FIG. 4, when the wave height of the first wave greatly exceeds the height of the breakwater 4 and an overflow occurs, the backside 3 on the land side is scoured by the overflow and the breakwater It is also assumed that 4 cannot resist the wave pressure and collapses to the land as it is.

  This is the same for the wave-breaking structure shown in Patent Document 1 and the tide-proofing facility shown in Patent Document 2, and in any case, the wave-breaking function against tsunami exceeding the expected scale is not available in the current wave-breaking structure. The reality is that it is not enough and countermeasures are urgently needed.

  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 much as possible without being destroyed even by a tsunami exceeding an assumed scale. .

  The invention described in claim 1 is a wave-breaking structure that has a wave-protecting function against a large-scale tsunami and has a fail-safe function that is not destroyed even when the wave height exceeds an assumed scale. A plate-shaped dam body made of steel plate is installed on the revetment structure in a state where it can be raised and lowered, and a shock absorber that supports the levee body is interposed between the levee body and the revetment structure. Therefore, it is possible to prevent overflow to the land side by supporting the dam body against the wave pressure of the assumed scale and maintaining the standing state of the dam body against the wave pressure. And, for wave heights exceeding an assumed scale, the shock absorber is operated by the wave pressure, and the levee body overturns to the land side so that overflow is allowed.

  The invention according to claim 2 is the wave-breaking structure according to claim 1, wherein the dam body is formed of a curved plate-shaped steel plate that bulges toward the land side, and the dam body is vertical in a standing state. It is installed in a slanted state on the land side with respect to the surface.

In the case of a tsunami exceeding the assumed scale, the wave-breaking structure according to the present invention has a fail-safe function of avoiding destruction at the expense of part of the wave-breaking function, thereby avoiding the worst situation. Is possible. In other words, in the breakwater structure of the present invention, in the case of a tsunami exceeding the assumed scale, the shock absorber is activated by the wave pressure, and the dam body is temporarily overlaid to the land side, thereby minimizing the overflow It is possible to reduce the tsunami damage as a whole by maintaining the wave-breaking function persistently by allowing the dam body to avoid being damaged by receiving excessive wave pressure.
In particular, by installing the levee body in an inclined state on the land side as a curved plate shape that bulges toward the land side, it functions as a flare-type wave-breaking structure in normal times and has excellent wave-breaking performance Can be demonstrated.

It is sectional drawing which shows schematic structure of the wave-proof structure which is embodiment of this invention, Comprising: It is a figure which shows the condition which received the tsunami of the assumed scale. It is a figure which shows the condition which received the tsunami exceeding the assumption scale. It is explanatory drawing of the destruction mechanism by the tsunami of the conventional general breakwater. It is explanatory drawing of the destruction mechanism by the tsunami of the conventional general breakwater.

One embodiment of the wave-proof structure of the present invention is shown in FIG.
The wave-breaking structure 10 of the present embodiment assumes a large-scale tsunami and has a wave-breaking function against the tsunami. In particular, the wave-breaking structure 10 is tenacious as much as possible without being destroyed even by a tsunami exceeding the assumed scale. A structure capable of maintaining the wave-breaking function is intended to prevent the spread of tsunami damage due to early destruction as in the prior art.

  Therefore, the breakwater structure 10 according to the present embodiment has a wavebreak function for a tsunami whose level of occurrence is assumed to be about once every 100 years (level 1 class tsunami) without trouble as with a normal breakwater. In addition, even if a large-scale tsunami (level 2 class tsunami) that is expected to occur once every 1000 years is generated, the minimum wave-breaking without being destroyed It is installed with a fail-safe function that can maintain the function.

  Specifically, the breakwater structure 10 of the present embodiment is based on the fact that a plate-shaped dam body 12 made of a steel plate is installed on a strong revetment structure 11 provided along the coastline. However, the dam body 12 is supported by the revetment structure 11 in a state where the levee body 12 can be raised and lowered as indicated by a broken line, and the levee body 12 is disposed between the levee body 12 and the revetment structure 11 on the back side. The main point is that the shock absorber 13 supported from the (land side) is interposed.

  In the present embodiment, the steel plate as the levee body 12 has a curved plate shape that slightly bulges toward the land side, and the dam body 12 is slightly inclined toward the land side as shown by a solid line in FIG. By installing in a state (this state is an original standing state), the dam body 12 itself functions in the same manner as a flare type breakwater as shown in Patent Document 1 in an ordinary state, and is excellent in breakwater. It can function.

The height of the levee body 12 is set to be at least larger than the wave height assumed in the case of a level 1 class tsunami, which is an assumed scale. As shown in FIG. 12 and the shock absorber 13 supporting the same can maintain the standing state of the dam body 12 against the wave pressure and prevent overflow.
However, as shown in FIG. 2, in the case of a level 2 class tsunami exceeding the assumed scale, the dam body 12 collapses to the land side due to the shock absorber 13 defeating the wave pressure and contracting. The height of the body 12 is lowered and the overflow is intentionally allowed.

  As described above, the breakwater structure 10 of the present embodiment has a structure that allows the overflow of the dam body 12 to fall over in the event of a tsunami exceeding the assumed scale, so that it is sufficient for a level 1 class tsunami. In addition to having a wave-breaking function, a minimum wave-breaking function can be exerted against a level 2 class tsunami without being destroyed like a conventional breakwater.

That is, when a tsunami of level 1 class, which is an assumed scale, is received, the dam body 12 can maintain its standing state against the wave pressure as shown in FIG. In addition, the wave-proof function is demonstrated without hindrance.
At that time, depending on the tsunami scale, there is room for the shock absorber 13 to be slightly retracted due to wave pressure and the dam body 12 to be slightly inclined to the land side. Therefore, the supporting force of the shock absorber 13 is set appropriately and sufficiently so as not to occur.

On the other hand, when a level 2 class tsunami exceeding the assumed scale is received, an excessive wave pressure acts on the dam body 12, so that the shock absorber 13 resists the wave pressure as shown in FIG. The supporting force is set so that the dam body 12 can not be completely cut and is greatly degenerated to allow the levee body 12 to fall to the land side and allow the tsunami to overflow.
In this way, in the event of a tsunami exceeding the expected scale, the levee body 12 is overlaid to allow a minimum overflow, so that excessive wave pressure acts on the dam body 12. Therefore, it is possible to prevent the dam body 12 from being completely destroyed. Therefore, compared with the conventional case where the entire breakwater is completely destroyed, the tsunami damage at that point is minimized. Is possible.

Of course, although the overflow is allowed, the overflow remains only as much as the decrease in the height of the levee body due to the collapse of the dam body 12, so that the damage is minimized as compared with the case where the entire dam body 12 is destroyed. It is possible to stop.
When the tsunami ends and the wave height and wave pressure are reduced, the shock absorber 13 naturally expands by its own restoring force and raises the dam body 12 to return to the state of FIG. The body 12 can recover the wave preventing function again and be prepared for the subsequent tsunamis, and can also exert the wave preventing function against the tsunamis that repeatedly push in as before.

As described above, according to the breakwater structure 10 of the present invention, although the minimum overflow is temporarily generated in the case of the largest tsunami exceeding the assumed scale, the dam body 12 is completely Since it is possible to avoid the destruction and to maintain the wave-breaking function persistently, it is possible to reduce the tsunami damage as a whole.
In other words, if the levee body 12 does not fall down even in the case of a tsunami exceeding the assumed scale, the dam body 12 will eventually break down due to excessive wave pressure, and the wave protection function will be completely lost at that time. Therefore, it is assumed that the tsunami that rushes after that cannot be dealt with at all like the conventional breakwater, but when the scale exceeds the assumed scale as described above, the minimum overflow is required. By providing the fail-safe function of avoiding destruction by allowing it, it is possible to avoid the worst situation.

However, in order to ensure such a fail-safe function, the dam body 12 will stably collapse without being destroyed even in the event of a tsunami exceeding the expected scale, and after the tsunami ends, it will be buffered. Since it is premised on that the restoring force of the device 13 stably returns to the standing state, the specifications such as the strength and restoring performance of the dam body 12 and the shock absorber 13 are set appropriately so as to be possible. Of course there is a need.
For this purpose, not only is the revetment structure 11 constructed sufficiently robust so as not to be damaged by scouring during overflow, the dam body 12 and the shock absorber 13 are, for example, illustrated in FIG. As shown, it is preferably supported and installed by a robust support pile 14.

  Even if the tsunami exceeds the assumed scale, if the dam body 12 is maintained in a standing state and can be prevented from overflowing, it is not necessary to lie down on the dam body 12 (that is, fail-safe). However, this is equivalent to simply raising the assumed tsunami scale to the level 2 class, and in that case the height of the dam body 12 is much larger. Such is not practical because it needs to be set and its strength much stronger.

Although one 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, and may be within the scope of the present invention. Appropriate design changes and applications are possible.
For example, in the above embodiment, the levee body 12 is installed in a curved plate shape in an inclined state so as to function as a flare-type wave-breaking structure at normal times. If it has intensity | strength, it may be made into a mere lithographic form, and may be installed in the state which made the bank body 12 stand upright.
In short, in the present invention, the dam body is supported so as to be able to fall by a shock absorber, and the tsunami exceeding the assumed scale is intentionally fallen to allow overflow, and is automatically restored after the tsunami ends. As long as that is the case, the specific structure of the dam body and the shock absorber may be arbitrary, and may be optimally designed in consideration of the assumed scale and location conditions of the tsunami.

DESCRIPTION OF SYMBOLS 10 Breakwater structure 11 Seawall structure 12 Dike body 13 Shock absorber 14 Support pile

Claims (2)

A wave-breaking structure with a fail-safe function against a large-scale tsunami and with a fail-safe function that is not destroyed even when the wave height exceeds the expected scale,
A plate-shaped dam body made of steel plate is installed on a revetment structure provided along a coastline in a undulating state, and a shock absorber for supporting the levee body between the levee body and the revetment structure is provided. Intervening,
With respect to the wave height of the assumed scale, it is possible to prevent overflow to the land side by supporting the bank body against the wave pressure and maintaining the standing state of the bank body, and For wave heights exceeding an assumed scale, the shock absorber is operated by the wave pressure, and the levee body overturns to the land side so that overflow is allowed. The wave-breaking structure according to claim 1,
The levee body is formed of a curved plate-shaped steel plate that bulges toward the land side, and the dam body is installed in an inclined state on the land side with respect to a vertical plane in a standing state. Structure.

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