JP2013092017A - Breakwater structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a breakwater structure with a fail safe function which is capable of presenting a breakwater function persistently as further as possible without being destroyed even with respect to tsunami beyond an expected scale.SOLUTION: A concave seat 12a a cross section of which is shaped arcuate is installed in an upper part of a shore protection structure 11 and a levee 13 a cross section of which is shaped circular is disposed on the concave seat so as to be rolled to the land side and to the sea side. The levee is disposed in the center of the concave seat while defining the center thereof as an original position, presents a breakwater function at the original position by resisting wave pressure with its own dead weight with respect to tsunami within an expected scale, is rolled from the original position to the land side on the concave seat by tsunami beyond the expected scale and rolled to the sea side in the case of backwash, thereby maintaining the breakwater function, and is recovered to the original position with its own dead weight after termination of tsunami. In the state where the levee is disposed at the original position, the position of a center 14 of gravity is set lower than a rotation center position.

Description

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

  As a breakwater structure against tsunami and storm surge, for example, a movable breakwater as shown in Patent Document 1 and a undulating gate breakwater as shown in Patent Document 2 have been proposed.

JP 2006-70536 A JP 2011-111761 A

The Great East Japan Earthquake caused tremendous damage due to the occurrence of a large tsunami that exceeded the expected scale, and it is said that the cause was that the breakwaters and tidewalls were destroyed early and could not function sufficiently. .
In other words, a tsunami is a “wave” that repeatedly pushes over several times like a normal wave, but in the recent earthquake disaster, the breakwater and tide bank were seriously damaged by the first wave. As a result, the wave after the second wave can no longer perform its original wave-proof function, which is considered to have expanded the damage.

  As shown in Fig. 3, the mechanism of the breakwater of the seawall due to the tsunami exceeding the assumed scale is as follows. This is thought to be because the tide bank 1 could not resist the wave pressure and collapsed to the land side.

  In this way, even when the breakwater and the breakwater are destroyed by a tsunami exceeding the assumed scale and the breakwater function is lost at an early stage, even in the movable breakwater as shown in Patent Literature 1 and Patent Literature 2. In any case, the current wave-breaking structure does not have a sufficient wave-breaking function against a tsunami exceeding the assumed scale, and it is the actual situation that countermeasures against it 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 according to claim 1 is a breakwater structure having a wave-safe function against a large-scale tsunami and having a fail-safe function that is not destroyed by a tsunami exceeding an assumed scale, and is provided along a coastline. A concave seat with an arc-shaped cross-section is installed on the upper part of the structure, and a dam body with a circular cross-sectional shape is arranged on the concave seat so as to be able to roll to the land side and the sea side. By placing the central portion of the concave seat as an original position, it is possible to exert a wave-proof function at the original position by resisting wave pressure due to the dead weight of the levee body against an assumed scale tsunami, and The levee body rolls from the original position to the land side and the sea side on the concave seat due to the tsunami exceeding the assumed scale and the wave pressure of the pulling wave to maintain the wave preventing function, and the original position by the dead weight by the end of the tsunami It is possible to return to The features.

  The invention according to claim 2 is the wave-breaking structure according to claim 1, wherein the dam body is set at a position where the center of gravity is lower than the rotation center position in a state where the bank body is disposed at the original position. It is characterized by being.

The wave-breaking structure of the present invention can maintain the wave-breaking function and avoid the worst situation without breaking the dam body even in the case of a tsunami exceeding the assumed scale.
That is, in the breakwater structure of the present invention, a concave seat is installed on the revetment structure, and a dam body having a circular cross section is arranged on the concave seat so that it can roll on the land side and the sea side, so that it can be used normally. The levee body functions in the same way as ordinary breakwaters and tidewalls due to its own weight, and in the event of a tsunami exceeding the expected scale, the dam body rolls to the land side on the concave seat due to the wave pressure and at the sea side by the pulling To maintain the wave protection function as it is, and after the tsunami ends, by returning to its original position due to its own weight, the tsunami exceeding the expected scale will be maintained without being destroyed. It is possible to reduce tsunami damage.
In particular, when the levee body is located at the original position, the center of gravity is set lower than the rotation center position, so that it is sufficiently stable at the original position in normal times and reliably after rolling. It is possible to return to the position.

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 a conventional general seawall.

One embodiment of the wave-proof structure of the present invention is shown in FIG.
The wave-breaking structure 10 of the present embodiment has a wave-breaking function against a large-scale tsunami, but it is as much as possible without being destroyed even against a tsunami exceeding the assumed scale. The purpose of this structure is to prevent the spread of tsunami damage caused by early destruction such as conventional breakwaters and tidewalls as a structure that can persistently maintain the wavebreak function.

  For this reason, the breakwater structure 10 of the present embodiment has no problem with a tsunami of a scale that is assumed to occur once every 100 years (level 1 class tsunami), as with ordinary breakwaters and tidewalls. Even if a large-scale tsunami (level 2 class tsunami) that is assumed to occur once every 1000 years is generated on the basis of demonstrating the wave-breaking function, the wave-breaking is not destroyed. It is installed as having a fail-safe function that can maintain the function.

  Specifically, the breakwater structure 10 of the present embodiment includes a gantry 12 having a concave seat 12a on a revetment structure 11 provided along a coastline, and a dam body having a circular cross section on the gantry 12. 13 is arranged to be able to roll on the land side and the sea side, and when the dam body 13 receives excessive wave pressure due to a tsunami exceeding the expected scale, it rolls to the land side by the wave pressure and The main purpose is to maintain the wave-breaking function by rolling to the sea side by the pulling wave, and to return to the original position after the tsunami ends and to maintain the original wave-breaking function as it is.

  The gantry 12 in this embodiment is constructed integrally with the revetment structure 11 as a robust structure made of, for example, reinforced concrete, and is formed in an arc shape between the side wall portions 12b raised on the land side and the sea side, respectively. It has a sectional shape provided with a concave seat 12a that is smoothly curved.

The dam body 13 in the present embodiment is a strong and massive structure made of, for example, reinforced concrete, and its outer diameter is smaller than the inner diameter of the concave seat 12a, as shown in FIG. By being placed horizontally on the gantry 12 (in a state where the axis of the levee body 13 is horizontal), the center of the gantry 12 is placed at the original position in a normal state and stably placed there. It is what.
The height of the levee body 13 is set to be at least higher than the wave height at the time of occurrence of a tsunami of level 1 class in the state where it is located at the original position as shown in FIG. 1, and its own weight is at least level 1 It is set so that it can resist the wave pressure received during the tsunami of the class and can exert the wave-breaking function in the same way as ordinary breakwaters and tidewalls.
And in the breakwater structure 10 of this embodiment, when the level 2 class tsunami exceeding an assumed scale generate | occur | produces and the excessive wave pressure by it acts on the levee body 13, the dam body 13 is like that. As shown in FIG. 2, it is possible to rotate and roll on the gantry 12 (that is, inside the concave seat 12a) and roll to the land side as shown in FIG. It is possible to rotate and roll.

In addition, since the dam body 13 having a circular cross section is arranged on the concave seat 12a, when the levee body 13 rolls, it rides on the side wall 12b. It rolls in the direction and descends the side wall portion 12b to restore the original position. However, in order to secure the restoring force more reliably, the position of the center of gravity 14 of the dam body 13 is more than the center of rotation (axial core). It is preferable to set it so that it is at a low position. For this purpose, for example, it is preferable to form a hollow portion 15 in the upper portion of the bank 13 as shown in the figure.
By setting the position of the center of gravity 14 of the levee body 13 so low, the dam body 13 can be placed in a stable and stable position at the normal position so that sufficient resistance to wave pressure can be obtained. Even when the frictional resistance between the surface and the concave seat 12a is large, the original position can be reliably restored.

In the case of the tsunami exceeding the assumed scale, the breakwater structure 10 according to the present embodiment rolls the dam body 13 to the land side due to excessive wave pressure as described above, and its position is more land than the original original position. Although it moves slightly to the side, the height as the dam body 13 does not decrease, but rather rises slightly by climbing onto the side wall 12b, and in this state, the wave-proof function can be maintained without any problem.
In addition, the dam body 13 rolls to the sea side at the time of pulling to maintain the wave-breaking function, and after returning to the original position due to its own weight after the tsunami ends, the wave-breaking function can be maintained as it is before rolling. It is.

Therefore, according to the breakwater structure 10 of the present embodiment, not only has a sufficient wavebreak function for level 1 class tsunamis, but also conventional level breakwaters and tides for level 2 class tsunamis exceeding the expected scale. The wave-breaking function will not be lost at an early stage due to collapse or destruction like a bank, so it is possible to cope with the tsunami that can persist and repeatedly push the wave-breaking function. is there.
Of course, in the breakwater structure 10 of the present embodiment, when the wave height exceeds the height of the dam body 13 in the case of a tsunami exceeding the assumed scale, the overflow cannot be prevented. Compared to the case where the entire breakwater or tide wall is collapsed, the damage can be minimized.

However, in order to ensure such a fail-safe function, the dam body 13 is stably rolled on the gantry 12 without being destroyed even in the case of a tsunami exceeding the assumed scale, and the wave is prevented as it is. Since it is assumed that the function can be maintained and the original position can be returned to the original position, it is natural that the strength, shape and weight of the levee body 13 should be appropriately set so as to be possible.
Moreover, since the dam body 13 needs to be able to stably roll and be restored to the original position while preventing the dam body 13 from falling off the concave seat 12a, the shape of the dam body 13 -It is necessary to set the shape of the concave seat 12a appropriately according to the dimensions and the own weight.
Furthermore, since the base 12 and the revetment structure 11 need to be sufficiently robust so that they are not easily destroyed or scoured, the base 12 is supported by the support pile 16 as shown in the figure. Therefore, even if the revetment structure 11 is scoured to some extent, it is possible to stably support the gantry 12 and the dam body 13 and maintain the wave-breaking function.

  As described above, according to the breakwater structure 10 of the present invention, the dam body 13 having a circular cross section is installed on the concave seat 12a so as to be able to roll, and in the case of a tsunami exceeding the assumed scale, the dam body 13 rolls. By deliberately allowing movement, it is possible to avoid the situation where the wave-breaking function is completely lost due to falling or being destroyed when exceeding the assumed scale, such as conventional breakwaters and seawalls Therefore, it is possible to maintain the wave-proofing function persistently and sufficiently reduce the tsunami damage.

In addition, if the dam body 13 has a structure capable of maintaining the wave-proof function at the same position without rolling even when the tsunami exceeds the assumed scale, it is not necessary to roll the dam body 13 intentionally. (In other words, it is not necessary to provide a fail-safe function as in the present invention), but this is equivalent to simply raising the assumed scale of the tsunami to the level 2 class, in which case the level 2 class The dam body 13 as well as the gantry 12 and the revetment structure 11 that support the tsunami need to be extremely heavy and robust, and they must be firmly and structurally integrated. Such a thing is not realistic.
On the other hand, in the present invention, the levee body 13 has a circular cross section and is simply disposed on the concave seat 12a. In the case of a tsunami exceeding the assumed scale, the dyke body 13 is allowed to roll. Since the wave-breaking function can be maintained afterwards, such a structure allows the wave-breaking function 13 and the gantry 12 and the revetment structure 11 to be tenaciously strong without being excessively heavy or excessively strong. Sustainable, extremely reasonable and effective.

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, as long as it does not depart from the gist of the present invention. Appropriate design changes and applications are possible.
In short, in the present invention, the dam body 13 having a circular cross section may be arranged and installed in a state that it can be rolled by the concave seat 12a. The shape and structure are arbitrary, and an optimal design may be made in consideration of the assumed scale and location conditions of the tsunami.
For example, in order to secure a sufficient dead weight, the dam body 13 is realistic to have a horizontal columnar shape with a solid cross section of a reinforced concrete structure. In that case, for example, a steel material or a steel pipe can be used as a material for the dam body 13, and if necessary, an appropriate filler may be filled therein to secure a desired mass. .
In the illustrated example, the side wall 12b of the gantry 12 is raised on the revetment structure 11 by installing the gantry 12 having the concave seat 12a on the revetment structure 11, but if possible, the gantry 12 Is embedded in the upper portion of the revetment structure 11 so that the concave seat 12a is installed at a position lower than the upper surface of the revetment structure 11, and a groove functioning as the concave seat 12a is directly formed on the upper surface of the revetment structure 11. By doing so, it may be considered that the gantry 12 is omitted and the revetment structure 11 itself has a function as the concave seat 12a.

DESCRIPTION OF SYMBOLS 10 Wave breaker structure 11 Seawall structure 12 Mount 12a Concave seat 12b Side wall part 13 Bank body 14 Center of gravity 15 Hollow part 16 Support pile

Claims (2)

A wave-breaking structure with a fail-safe function against a large-scale tsunami and a fail-safe function that is not destroyed by a tsunami exceeding the expected scale,
A concave seat with a circular cross-sectional shape is installed on the revetment structure along the coastline, and a dam body with a circular cross-sectional shape is arranged on the concave seat so that it can roll to the land side and the sea side. And
The dam body is located at the center of the concave seat as the original position, so that it can resist the wave pressure by the dead weight of the levee body against the tsunami of the assumed scale, and can exert the wave preventing function at the original position. The levee body rolls from the original position to the land side and the sea side on the concave seat due to the tsunami exceeding the assumed scale and the wave pressure of the pulling wave, and maintains the wave protection function, and the tsunami ends. A wave-proof structure characterized by being able to return to its original position by its own weight. The wave-breaking structure according to claim 1,
The dam body is set at a position where the center of gravity of the levee body is lower than the rotation center position in a state where the dam body is disposed at the original position.

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