JP6692879B2 - Water flow attenuation network and wave breaker using the same - Google Patents

Description

  The present invention relates to a water flow attenuation network installed offshore of a coast for reducing the height and momentum of a tsunami, and a wave breaker using the same.

  In recent years, large-scale disasters due to tsunamis have occurred in coastal areas, and as measures to prevent tsunami disasters, breakwaters, tidewaters, levees, etc. made of concrete structures have been installed. However, such a fixed structure has a limit in strength and height for preventing a tsunami. That is, with respect to a large-scale tsunami having a height higher than expected, the effect of preventing the tsunami is insufficient, such as insufficient height to receive the tsunami or being destroyed by excessive water pressure of the tsunami. For this reason, it is expected that evacuees who have escaped to high altitude will be caught in the tsunami.

  When the tsunami approaches the coast from the offshore area, the kinetic energy density increases as the water depth becomes shallower, and concentrated water pressure is applied to the breakwater and levees. If it can be attenuated, the height and power of the tsunami reaching the coast can be reduced.

  Therefore, conventionally, there has been proposed one aiming to reduce the energy of the tsunami before reaching the coast by decelerating the flow of the tsunami with an offshore stretched net (see, for example, Patent Document 1). ..).

  In this conventional example, one end side of the net is connected to an anchor member on the seabed, and the other end side of the net is connected to an anchor member at another position on the seabed via a rope, and the net is normally settled on the seabed. Incidentally, when a tsunami occurs and the water flow increases, the net expands into the water, and the flow resistance of the tsunami reduces the flow velocity of the water flow due to the flow resistance when passing through the net.

JP, 2008-63826, A

  In the above-mentioned conventional example, one end side and the other end side of the net are connected to the seabed side, and the water pressure of the tsunami is applied in such a way that the sail of the ship receives wind, so the stress generated in the net and rope depends on the water pressure. Grows. However, since the tsunami is a natural phenomenon, it is difficult to predict its scale and power, and if excessive water pressure is applied by the large-scale tsunami, the nets and lobes will break or the anchor members will come off the seabed. There was a risk of destruction by the tsunami.

  The present invention has been made in view of the above problems, and an object of the present invention is not to be easily destroyed by the water pressure of the tsunami regardless of the scale of the tsunami, and to effectively attenuate the water flow of the tsunami. It is an object of the present invention to provide a water flow attenuating network and a wave preventing device using the same.

In order to achieve the above-mentioned object, the water flow damping network of the present invention has a net having flexibility as a whole and for receiving a water flow due to a tsunami, a floating body imparting buoyancy to the net, and arranged on the seabed. An anchor member and a connecting member that connects the one end side of the net body and the anchor member are provided.In normal times, the whole net body is floated on the sea surface by the floating body, and when the sea surface rises due to the tsunami, it is connected to the anchor member. The one end side of the net body is settled by the tension of the connecting member, and the net body stands up in the sea with the other end side facing upward due to the buoyancy of the floating body.

  Due to this, when the sea surface rises due to the arrival of the tsunami, one end side of the net body sinks due to the tension of the connecting member connected to the anchor member, and the net body rises in the sea with the other end side up, so the tsunami progresses. A part of the water flow that goes straight in the direction of the net reduces the flow velocity due to the flow resistance when passing through the mesh of the net, and the other water flow that is blocked by the flow resistance of the net from the side of the net. Is induced, the momentum of the water flow on the downstream side of the water flow attenuation network is attenuated. In this case, one end side of the net body is connected to the connecting member, but the other end side of the net body is a free end that is not connected to the seabed side, so that both one end side and the other end side of the net body are Excessive water pressure will not be applied to the net as in the case of connecting to the seabed side.

  Further, in order to achieve the above-mentioned object, the breakwater device of the present invention includes a plurality of the water flow attenuation nets, and the water flow attenuation nets are arranged in a plurality of rows in the traveling direction of the tsunami.

  As a result, since the plurality of water flow attenuation networks are installed so as to form a plurality of rows in the traveling direction of the tsunami, the momentum of the tsunami is attenuated in multiple stages by the water flow attenuation networks in each row.

  According to the present invention, while imparting flow resistance to a part of the water flow that passes through the net, it is possible to guide the other water flow that does not pass through the net to the side of the net, so that the water flow of the tsunami is effective. The tsunami reaching the coast can be reduced in height and power. In this case, even if a large-scale tsunami is applied, an excessive water pressure is not applied to the net body, so that there is an advantage that it is not easily destroyed by the tsunami.

The side view which shows one Embodiment of the water flow damping network of this invention. Plan view of water flow attenuation network Side view showing operation of water flow attenuation network Plan view showing the operation of the water flow attenuation network The top view which shows 1st Embodiment of the breakwater device of this port plan. Partial plan view showing the operation of the breakwater The top view of the water flow attenuation net | network in 2nd Embodiment of the wave breaker of this port plan. Plan view showing the operation of the water flow attenuation network Partial plan view showing the operation of the breakwater Plan view showing an example of installation of the breakwater Plan view showing the operation of the breakwater

  1 to 4 show an embodiment of the present invention, and show a water flow attenuation network for attenuating a tsunami water flow.

  The water flow attenuation net 1 shown in the same figure has a net body 2 for receiving a water flow caused by a tsunami, first and second floating bodies 3 and 4 for imparting buoyancy to the net body 2, and a pair of anchors arranged on the seabed. The member 5 and a pair of connecting members 6 that connect one end side of the mesh body 2 and each anchor member 5 are provided.

  The net body 2 is made of a synthetic resin net having high tensile strength, and is formed in, for example, a square shape having a side of 100 m. The mesh size of the mesh body 2 is preferably about 100 mm × 100 mm at the minimum and about 300 mm × 300 mm at the maximum. A seaweed aquaculture net in which seaweed is easy to reproduce is used for the net body 2, and such a seaweed aquaculture net is described in, for example, JP-A-2003-158929 and JP-A-2006-180721. is there.

  Each of the first and second floating bodies 3 and 4 is made of a hollow spherical member, and a plurality of them are attached to the peripheral edge of the net body 2 at intervals. The first floating body 3 is formed to be larger than the second floating body 4, and the first floating body 3 is arranged on one of the four sides of the net body 2 and the second floating body is formed on the other three sides of the net body 2. The floating body 4 is arranged.

  Each anchor member 5 is made of a concrete heavy object and is arranged on the seabed at a distance from each other. The shape of the anchor member 5 is preferably a starfish shape as in the present embodiment as a shape that is hard to fall down and is hard to be dragged, but may be another shape such as a low-profile cylindrical shape or a prismatic shape.

  Each connecting member 6 is made of a synthetic resin rope having high tensile strength, and one end thereof is connected to each anchor member 5. The other end of each connecting member 6 is connected to both ends on one end side of the net body 2 (on the other side opposite to one side of the net body 2 on which the first floating body 3 is arranged). In this case, each connecting member 6 is formed to be slightly longer than the distance from the sea surface position S in normal times (at high tide) to the anchor member 5 on the sea floor.

  The water flow attenuation network 1 configured as described above is installed offshore in the coastal area. In this case, in the water flow attenuation net 1, the anchor members 5 are arranged at intervals substantially equal to the width of the net body 2 in the direction orthogonal to the tsunami traveling direction, and one end side of the net body 2 receives the tsunami. It is arranged so that the upstream side and the other end side of the net body 2 are the downstream side of the tsunami.

  Next, the operation of the water flow attenuation network 1 will be described. First, in normal times, as shown in FIG. 1, the entire net body 2 floats above the sea surface due to the buoyancy of the first and second floating bodies 3 and 4. In this case, since the first and second floating bodies 3 and 4 are arranged on the periphery of the net body 2, the net body 2 is kept in a state of being spread along the sea surface as shown in FIG.

  Here, when a tsunami is generated offshore and the sea surface rises above the normal sea level S due to the arrival of the tsunami as shown in FIG. 3, the net body is caused by the tension of each connecting member 6 connected to each anchor member 5. One end side of 2 settles, and the net body 2 stands up in the sea with the other end side facing up. At that time, in the water flow attenuating network 1, as shown in FIGS. 3 and 4, the net body 2 is deflected by the water pressure of the tsunami according to the tsunami traveling method, and as shown by the white arrow in the figure, it travels straight in the tsunami traveling direction. The flow velocity of a part of the flowing water flow is reduced by the flow resistance when passing through the mesh of the mesh body 2, and another water flow that is prevented from passing through the mesh body 2 by the flow resistance of the mesh body 2 is left and right of the mesh body 2. By being guided to both sides, the momentum of the water flow on the downstream side of the water flow attenuation net 1 is attenuated. In this case, one end side of the net body 2 is connected to the connecting member 6, but the other end side of the net body 2 is a free end that is not connected to the seabed side. Unlike the case where both sides are connected to the seabed side, an excessive water pressure is not applied to the net body 2 and the pressure of the tsunami can be released.

  Also, in normal times, seaweeds start to reproduce in the net body 2 floating on the sea surface, and around the net body 2, there are fish that eat seaweed and other fish that supplement the fish. It reproduces and the net body 2 functions as a fish reef. As a result, the area around the water flow attenuation net 1 becomes an abundant fishing ground, and it becomes possible to contribute to the fishing and aquaculture in the surrounding sea area.

  As described above, according to the water flow attenuation net of the present embodiment, when the sea surface rises due to the tsunami, the tension of the connecting member 6 connected to the anchor member 5 causes one end side of the net body 2 to settle and Since the net body 2 is made to stand up in the sea with the other end side up by the buoyancy of the first floating body 3 generated at the end side, a flow resistance is imparted to a part of the water flow passing through the net body 2 and the net Other water streams that do not pass through the body 2 can be guided to the side of the net body 2. As a result, the water flow of the tsunami can be effectively damped, and the height and power of the tsunami reaching the coast can be reduced.

  In this case, one end side of the net body 2 is connected to the connecting member 6, but the other end side of the net body 2 is not connected to the seabed side. It has the advantage that no strong water pressure is applied and it is not easily destroyed by the tsunami.

  In addition, since the net 2 is floating above the sea surface during normal times, the existence of the net 2 can be easily confirmed from the sea, and the fishing net of a fishing boat is caught in the net 2 to prevent fishery. The obstacle can be avoided. Furthermore, since the net body 2 does not sink to the sea floor during normal times, there is an advantage that it does not affect the ecosystem of marine organisms living near the sea floor.

  In addition, since the whole of the net body 2 is floated above the sea surface by the first and second floating bodies 3 and 4 in normal times, seaweeds can be reproduced in the net body 2 and the water flow attenuation net 1 It is also possible to make the surroundings abundant fishing grounds. As a result, it is possible to contribute to the fishing and aquaculture industries in the surrounding sea area, and there is also an advantage that it is possible to effectively use tsunami countermeasures that are unnecessary during normal times.

  Furthermore, since the net body 2 is formed in a quadrangular shape and the connecting members 6 are connected to both ends of one side of the net body 2, the net body 2 can be widened greatly when a tsunami water flow is received. The water flow damping effect can be enhanced.

  In addition, since the first and second floating bodies 3 and 4 are arranged on the periphery of the net body 2, the net body 2 floating on the sea surface can be kept in a spread state along the sea surface. It is extremely advantageous for reproduction of seaweed.

  In this case, since the first floating body 3 arranged on the other end side of the net body 2 is formed to have a larger buoyancy than the second floating body 4 arranged on one end side of the net body 2, the net body 2 It becomes easier to stand up in the sea with the other end facing up, and the water flow damping effect of the tsunami can be further enhanced.

  5 and 6 show a first embodiment of a breakwater device using a plurality of the water flow attenuation networks 1.

  As shown in FIG. 5, the wave breaker 10 shown in the figure has a plurality of water flow attenuation nets 1 arranged in a plurality of rows in the traveling direction of the tsunami. In this case, each water flow attenuation network 1 has a water flow attenuation network 1 in the rear row (row downstream in the direction of tsunami) on the downstream side between the water flow attenuation networks 1 in the front row (row upstream in the direction of tsunami). They are arranged in a staggered pattern so that they are located. Further, each water flow attenuation net 1 is arranged in a fan shape as a whole so that the number of the water flow attenuation nets 1 in each row gradually increases from the upstream side to the downstream side in the traveling direction of the tsunami.

  In this breakwater device 10, since the plurality of water flow attenuation nets 1 are installed so as to form a plurality of rows in the traveling direction of the tsunami, the water flow attenuation nets 1 in each row can increase the tsunami momentum in multiple stages. Attenuated. In this case, since the water flow attenuation nets 1 are arranged in a zigzag manner, the water flow of the tsunami does not pass through between the water flow attenuation nets 1 in each row, and the water flow attenuation nets 1 in the front row are provided as shown in FIG. The water flow guided to the side of the net body 2 flows into almost the front of the net body 2 of the water flow attenuation net 1 in the rear row, and the water flow attenuation nets 1 in each row can efficiently attenuate the tsunami water flow.

  7 to 9 show a second embodiment of the breakwater device using a plurality of the water flow attenuation networks 1.

  In the breakwater device 10 of the first embodiment, the water flow of the tsunami is evenly guided to the left and right sides of the mesh body 2. However, in the breakwater device 20 of the present embodiment, the water flow of the tsunami When the net is received, the net 2 rises in the sea so as to incline to the left or right with respect to the direction of the tsunami, and the water current of the tsunami is guided to one side of the net 2.

  That is, in the present embodiment, as shown in FIG. 7, one of the pair of left and right connecting members 6 (the left side in the figure) is longer than the other connecting member 6 (the right side in the figure), When each connecting member 6 is strained due to the water flow of the tsunami, as shown in FIG. 8, one connecting member 6 is inclined longer than the other connecting member 6 and the net body 2 is inclined, as shown by the white arrow in the figure. Thus, the water flow of the tsunami is guided to one side of the net body 2.

  In addition, the wave breaker 20 of the present embodiment is similar to the wave breaker 10 of the first embodiment such that each water flow attenuation net 1 is positioned between the water flow attenuation nets 1 in the front row and the water flow attenuation nets 1 in the rear row. Are arranged in a zigzag pattern, and are arranged in a fan shape as a whole so that the number of the water flow attenuation nets 1 in each row gradually increases from the upstream side to the downstream side in the traveling direction of the tsunami.

  In the wave preventing device 20 of the present embodiment, the momentum of the tsunami is attenuated in multiple stages by the water flow attenuation network 1 in each row, as in the first embodiment. In this case, since the net body 2 is inclined to the left or right with respect to the tsunami traveling direction, the water flow of the tsunami is caused by the water flow attenuation nets 1 in each row as shown by the white arrow in FIG. 2 is guided to one side. As a result, the traveling direction of the tsunami can be changed to the left or right side as a whole of the wave preventing device 20, so that, for example, even if the tsunami arrives, it is possible to guide the tsunami to the side with less damage.

  FIG. 10 and FIG. 11 show an example in which the above-mentioned wave breaker is installed offshore in a coastal area, and is an installation example in the case of a terrain with hills B on both sides of a coast A where there are houses and ports on the land side. ..

  In this installation example, a first breakwater device group G1 consisting of a plurality of breakwater devices for guiding the tsunami water flow to the left and right is installed in the center, and the tsunami water flow is to the left and right to one side (left side in the figure). A second group of wave breakers G2 including a plurality of wave breakers for guiding is installed on the left side in the figure, and a third wave breaker for guiding the water flow of the tsunami to the other side (right side in the figure). The wave breaker group G3 is installed on the right side in the figure. In this case, the first wave breaker 10 (the water flow damping network 1 guides the water flow of the tsunami evenly to the left and right) is the same as that of the first embodiment in each of the wave breakers of the first wave breaker group G1. ) Is used for each wave breaker of the second wave breaker group G2, and the same second breaker 20 (the water flow attenuation network 1 as shown in FIG. 2) is used for the tsunami water flow to the left and right. (The one guiding to the left side in the figure) is used. Further, in each of the wave preventing devices of the third wave preventing device group G3, there is provided a third wave preventing device 30 (the water flow attenuating network 1 is provided with the water flow of the tsunami to which the second wave preventing device 20 is formed in the opposite direction). The one that guides to the other side (right side in the figure) is used.

  In this installation example, as shown by the white arrow in FIG. 11, when a tsunami arrives off the coast, the tsunami passing through the second group of breakwater devices G2 turns to the left or right and rises to the left The tsunami that travels toward B and passes through the third group of breakwater devices G3 turns to the other left and right and travels toward hill B on the right side. In addition, the tsunami passing through the first group of breakwater devices G1 attenuates the water flow and travels straight.

  As described above, in the installation example, the tsunami traveling toward the coast A is guided to the left and right hills B side by the second and third breakwater device groups G2 and G3, and the water flow of the tsunami traveling straight is first. The tsunami guided to the left and right is prevented from going up to the land by the hill B, and the tsunami arriving at the central coast A where the height from the sea is low The height and power of can be reduced. This can reduce the damage of the tsunami on the land side in the terrain such as the installation example.

  Note that the above installation example is an example, and other installation forms can be adopted depending on the topography of the coastal area. That is, the first breakwater device 10 has a high damping effect on the water flow of the tsunami, and the second and third breakwater devices 20 and 30 have a high effect of changing the traveling direction of the tsunami. Therefore, for example, from the sea surface like a cove. In the terrain where the height of the coast is low and the width of the coast is narrow, by installing the second or second breakwater device 20 or the third breakwater device 30, the tsunami is guided to one side to enter the cove. By preventing the intrusion of tsunami, it is considered possible to enhance the wave-prevention effect in such terrain. Further, for example, on a coastline where the beach continues for a long time, if the water flow of the tsunami is attenuated by installing the first breakwater device 10 in multiple rows along the coastline. It is thought that the wave effect can be enhanced.

  DESCRIPTION OF SYMBOLS 1 ... Water-flow attenuation net, 2 ... Net body, 3 ... 1st floating body, 4 ... 2nd floating body, 5 ... Anchor member, 6 ... Connection member, 10 ... 1st wave preventing device, 20 ... 2nd prevention Wave device, 30 ... Third wave preventing device.

Claims (8)

The whole has flexibility and a net body for receiving the water flow due to the tsunami,
A floating body that gives buoyancy to the net,
An anchor member arranged on the seabed,
A connecting member that connects the one end side of the net body and the anchor member,
In normal times, the floating body floats the whole net above the sea surface, and when the sea surface rises due to the tsunami, one end of the net will sink due to the tension of the connecting member connected to the anchor member, and the floating body will cause the other net to float. A water flow attenuation network characterized by standing up in the sea with the end side up. The water flow attenuation net according to claim 1, wherein the net is formed in a quadrangular shape, and the connecting members are respectively connected to both end sides of one side thereof. The water flow attenuation net according to claim 1 or 2, wherein the floating body is arranged on the periphery of the net. The water flow damping net according to claim 3, wherein the floating body arranged on the other end side of the net body is formed to have a larger buoyancy than the floating body arranged on one end side of the net body. A plurality of water flow damping networks according to claim 1, 2, 3 or 4,
A wave breaker in which each water flow attenuation network is arranged in multiple rows in the direction of the tsunami. The wave breaker according to claim 5, wherein each of the water flow attenuating nets is formed so that the net body inclines horizontally to one side with respect to the traveling direction of the tsunami in a state where the water flow of the tsunami is received. . The water flow attenuating networks are arranged so that the water flow attenuating networks in a row downstream in the tsunami traveling direction are located downstream of the water flow attenuating networks in the upstream row in the tsunami traveling direction. The wave preventing device according to claim 5. 8. The water flow attenuation nets are arranged so that the number of water flow attenuation nets in each row gradually increases from the upstream side to the downstream side in the tsunami traveling direction. Wave breaker.

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