JP4305872B2 - Tsunami breakwater - Google Patents

Description

  The present invention relates to a tsunami breakwater.

  Various waves occur in the ocean, but tsunamis are similar to changes in tide levels caused by storm surges in that the period of waves is very long. Usually, it is considered that a tsunami breakwater that assumes a high tide level above the storm surge in a construction plan can also serve as a high tide breakwater.

Many of the tsunamis are thought to be generated by seabed shifts and volcanic activity caused by earthquakes, and it is generally understood that coastal areas are always prepared for tsunamis. Conventional tsunami breakwaters are designed to withstand the impact of tsunamis by making the breakwaters large, heavy and solid, so they must be constructed using an extremely large amount of materials, and the construction is long. There was a problem that a period was required and a large construction cost was required.

  In general, most of the coastal population and social capital tend to be concentrated in bays, bays, and cities with harbors, and the areas where construction of tsunami breakwaters is strongly desired overlap. For these reasons, it is convenient to construct a tsunami breakwater that closes the narrow entrances, bays, and port entrances in order to effectively protect coastal people and much of the social capital from damage caused by the tsunami. . However, if a conventional tsunami breakwater is constructed in a narrow area at the entrance of a cove, bay, or port, the ship will not be able to navigate and the function of the port will be lost. The impact will be serious.

For this reason, many of the conventional tsunami breakwaters are constructed in such a way that some of the breakwaters are opened off the bays and harbors in consideration of these adverse effects. There is a problem that the place where the breakwater can be built is limited, and the breakwater necessary for disaster prevention is also increased as the depth of the tsunami reaches due to the large water depth and the impact received by the breakwater increases and the distance from the coast increases. Because of the length of the tsunami, there was a problem that a larger tsunami breakwater was required. In addition, since the tsunami breakwater must be constructed in such a way that a part of the breakwater is opened, the original purpose of the tsunami breakwater to prevent the intrusion of the tsunami is not sufficiently achieved, and the conventional tsunami breakwater constructed in the sea The disaster prevention effect was not only good enough to halve the wave height of the tsunami reaching the land, and it was not favorable for the landscape.

  Furthermore, conventional tsunami breakwaters are large in mass and long in shape, so if an earthquake that causes a tsunami occurs nearby, the tsunami breakwater will be damaged by the impact of the earthquake itself or ground deformation. The tsunami breakwater was damaged and subsidized, and when the tsunami breakwater was attacked by the tsunami, there was a problem that it could not perform its original function.

In order to solve these problems, a tsunami breakwater using a buoyant body or a film-like member has been proposed in Japanese Patent Application Laid-Open No. 2000-282434. This is a breakwater made of concrete or the like constructed in the coastal sea. The opening left in a part of the tsunami is closed by a tsunami breakwater that can be moved in the vertical direction by using a floating body, a film-like member, and the like, and tries to prevent the tsunami from entering.

However, considering the kinetic energy associated with the tsunami water flow, the floating body and film-like members should be moved up and down precisely within a limited area near the breakwater edge to open and close the breakwater opening where the ship comes and goes. There are structural weaknesses in how to do this. In addition, the complex structure is susceptible to damage due to the change in the ground due to the attachment of marine organisms and the impact of the earthquake prior to the tsunami, and the membrane-like member is limited to the vicinity of the breakwater end. There is a concern that the tsunami breakwater disclosed in Japanese Patent Application Laid-Open No. 2000-282434 by a method that must be vertically vertically moved within a specified range may not function sufficiently when an important tsunami strikes .

Furthermore, there are only a few tsunami breakwaters that can prevent the tsunami from entering the coastal sea, and the topography and water depth that can be constructed in the future, as well as the bottom of the sea. It is difficult to construct many tsunami breakwaters of this kind in view of the severe conditions of geology, huge construction costs, and the long construction time. For this reason, there is a disaster prevention method that attempts to close the opening between tsunami breakwaters made of concrete, etc. constructed in the coastal sea with a tsunami breakwater that can be moved vertically using buoyant bodies or membrane members. Even if it has the above effect, there is a limit.

In addition, like the tsunami breakwater proposed in the aforementioned Japanese Patent Laid-Open No. 2000-282434, a breakwater or a film-like member etc. is vertically moved up and down accurately within a limited range near the breakwater end, and the breakwater where ships come and go In the method of opening and closing the opening, the floating body on the sea surface is located directly above the membrane member when ascending, so the land side isolated by the membrane member is not the high water level that the tsunami brings Due to the buoyancy generated by the sea level, the floating body floats up by subtracting the mass of the floating body and the mass of the film-like member connected to the buoyancy generated in the floating body. For this reason, the effective height of the tsunami that can be received by this tsunami breakwater cannot exceed the height of the floating body that floats on the sea surface. There is inconvenience that you must use. If Furthermore, as the premise of the tsunami breakwater, from what is needed is breakwater made of concrete or the like which is built in the sea of the coast to the left and right of the tsunami breakwater to be built, such as those left and right side of a waterway wall and the natural terrain Etc. are inconvenient. In addition, for example, there is a difficulty in providing a tsunami breakwater at a point where the opening width is large, such as the Tokyo Bay entrance and the Ise Bay entrance.
JP 2000-282434 A Masahiko Oya et al. “Knowing and Preventing Natural Disasters” Kokon Shoin 1996

The problem to be solved by the invention is to provide a tsunami breakwater that can close the necessary coastline from the standpoint of disaster prevention, not limited to bays, bay entrances, and harbor entrances, without seriously affecting ship navigation, the natural environment and fishing. It is to provide an economical and high-performance tsunami breakwater that is less affected by the impact of earthquakes and ground changes, and that also takes landscapes into consideration.

The present invention has been made to solve the above-mentioned various problems. The impermeable curtain is suspended from the floating body that floats on the sea surface, and the lower edge of the curtain body is fixed to the sea floor. The anchor point and the floating body placed on the sea are connected by multiple tethers, and the center of the floating body is located on the offshore side more than a distance corresponding to 50% of the water depth at normal tide from the direct Shanghai surface of the seabed anchoring point at the lower edge of the curtain. In addition to the water depth assumed when the tsunami strikes, the dimension from the center of the floating body to the bottom edge seafloor anchoring point hanging from the center of the floating body should be 50% longer than the water depth. A tsunami breakwater that has a subsidence mechanism and is stored near the seabed during normal times and floated before the tsunami arrives.

Also, the height of the floating body that floats on the surface of the sea should be smaller than the height of the tsunami that is supposed to hit, or equipped with a gas body generator by chemical changes including combustion to float the floating body, A plurality of anchoring points are provided on the hanging curtain, and the anchoring points on the curtain and the anchoring points placed on the offshore seafloor of the floating body are connected by a mooring line. Tsunami breakwater using a tethered net.

Alternatively, with the lower edge of Makutai from floating to float on the sea surface by hanging an impermeable curtain is fixed with anchor bolts unit on the seabed, with the anchor bolt means placed in the floating body of the offshore seabed fixed The anchoring point and the floating body are connected by a plurality of tethers, and the center of the floating body is located on the offshore side at a distance corresponding to 50 to 200 percent of the normal tide depth from the direct Shanghai surface of the seafloor anchoring point at the lower edge of the curtain. The tsunami breakwater has a dimension from the center of the floating body to the bottom seam anchoring point of the curtain hanging from the bottom of the seabed that is 50 to 200 percent longer than the water depth assumed when the tsunami strikes.

The tsunami breakwater of the present invention is capable of assembling many parts of the dam body at high efficiency at land facilities, and is expected to reduce costs by standardizing and standardizing parts. There are advantages you can do. In addition, tsunami breakwaters are stored near the seabed during normal times and can be lifted and deployed when necessary, so that the impact on ship navigation, the natural environment and fishery can be reduced, and the construction of the tsunami breakwater does not deteriorate the landscape. In addition, the height of the tsunami surpassing the height of the floating body floating on the sea can be prevented, and there are few restrictions on the location where the tsunami breakwater is installed, and the levee body has been quickly levitated to become a tsunami breakwater.

Furthermore, the tsunami breakwater of the present invention is resistant to impacts and ground fluctuations because the dam body is extremely light and flexible compared to conventional tsunami breakwaters, and if an earthquake that causes a tsunami occurs nearby. However, the tsunami breakwater is less likely to be damaged or subsidized due to the impact of the earthquake itself or ground deformation, and the original function can be demonstrated when the tsunami breakwater is attacked by the tsunami due to damage or settlement of the tsunami breakwater It is a high-performance tsunami breakwater that solves the problem when it disappears.

Referring to the drawings, the best mode for carrying out the invention will be described. In the following description, the term “offshore” is used for the side where the tsunami pushes against the tsunami breakwater, and the term “land” is used for the opposite side. Use.

FIG. 1 is a cross-sectional view of the tsunami breakwater near the center of the present invention in a state where a tsunami is received. Tsunami breakwater of the present invention as shown in FIG. 1, Makutai of hanging an impermeable curtain 3 including a material capable of ensuring a sufficient strength of the floating body 1 to float on the sea surface 21 against an impact tsunami The lower edge 4 is fixed to the seabed 5 and the anchoring point 8 placed on the seafloor 7 offshore of the floating body is connected to the floating body by a plurality of tethers 9, and the center of the floating body is the direct Shanghai surface of the seafloor lower edge seafloor anchoring point. The water depth is assumed to be located more than 50% of the water depth at high tide during normal times, and the dimension from the floating body center to the bottom seam anchoring point 6 of the curtain hanging from the center of the floating body is assumed when the tsunami strikes In addition to the above, the water depth should be 50% or longer. Equipped with a floating body levitation mechanism, both ends of the tsunami breakwater are fixed by guiding them to a point where a safe height for disaster prevention on land can be secured. Since the tsunami breakwater will receive the impact of the tsunami, each member must have the necessary strength and the fixing points should be sufficiently strong. In order to fix the fixing point placed on the lower edge of the curtain or the offshore seafloor of the floating body to the seabed 5, as shown in FIG. 10, it may be secured using anchor bolts that reach the seabed rock. Here, the distance of more than 50% of the water depth at normal tide is offshore to ensure that the wave receiving part consisting of the curtain and the floating body can be positioned on the high water level side. If the center of is located 50% to 200% off the normal tide depth from the direct Shanghai surface at the seafloor anchor point of the lower edge of the curtain, the effect can be demonstrated. In addition, since the required dimensions of the curtain body are increased accordingly, the dimension from the center of the floating body to the bottom edge seabed anchoring point 6 of the curtain body hanging from the sea floor is added to the water depth assumed at the time of the tsunami strike, and 50% to 200% of the water depth. Percentage is longer.

Further, if necessary, the floating body constituting the tsunami breakwater can be made into a flexible membrane air sac 22 or a hard gas container 23, or a gas body generated by a chemical change including combustion in order to quickly give buoyancy to the floating body. or using.

During normal times, these are placed near the seabed, but the height of the floating body does not necessarily exceed the height of the tsunami that strikes, and the impervious curtain is preferably lightweight and flexible. The floating body is an air sac 22 made of a flexible membrane or a hard gas container 23, and a system that obtains buoyancy by filling the air sac or hard gas container with gas to form a floating body is a gas from an external device. When a necessary device such as a pipe 14 or a valve 15 for supplying the gas is attached and a gas body generated by a chemical change including combustion is used as the buoyancy of the floating body, a gas body generator is attached.

In addition, when the floating body is a hard gas container, and the floating body is to be stored near the seabed in a state where the gas container is filled with gas during normal times, it can be opened and closed to keep the floating body near the seabed. The floating body levitating restraint device 10 may be provided and placed.

FIG. 2 shows an embodiment of the present invention. During normal times, as shown in FIG. 2, the dam body is stored near the seabed 5 . Although not shown , if the main part of the levee body is covered with a film-like cover at the time of storage, adverse effects due to attachment of marine organisms and sediments can be reduced. If the lower edge of the impervious curtain is buried in the seabed, water flow from the bottom of the bank can be effectively prevented.

When an tsunami or an abnormal storm surge is expected, as shown in FIG. 3, the floating body 1 is levitated before the tsunami or storm surge arrives, and the tsunami breakwater wall composed of the floating body and the impervious curtain 3. To prepare for the invasion of tsunami and abnormal high tide.

Due to the tsunami and storm surge, a high water level 11 appears on the offshore side of the tsunami breakwater. Here, in the tsunami breakwater of the present invention, as shown in FIG. 1, the floating body 1 is arranged so as to be located on the offshore side 7 from the anchoring point 6 of the curtain body 3, and the anchoring point 9 and the position of the anchoring line 9 are anchored. By adjusting the length of the cord, the floating body center is located on the offshore side more than a distance corresponding to 50% of the normal tide depth from the direct Shanghai surface at the bottom seam anchoring point of the curtain body. Since the curtain 3 hanging from the center to the bottom of the sea is given a dimension that exceeds the water depth by 50% or more in addition to the water depth expected when the tsunami hits the installation point, the high water level 11 off the tsunami breakwater reaches below the floating body and floats Push up the curtain upper part 13 on the land side 12.

In the tsunami breakwater of the present invention, the high water level 11 off the tsunami breakwater reaches the lower part of the floating body and pushes up the upper part 13 of the floating body 12 on the floating land, so that the floating body 1 subjected to the water pressure of the tsunami is further increased by the high water level of the tsunami. As it floats and is always located on the high water level of the tsunami, even if the height of the floating body that floats on the surface of the sea is smaller than the height of the tsunami that hits it, the tsunami with high wave height is prevented from progressing be able to.

Tsunamis and storm surges have a very long period of at least a few minutes and in some cases over 10 hours, so the rise time of the tide level is very long, and the embankment has a high water pressure caused by high water levels over a long period of time. If this is a tsunami, it is usually repeated several times. For this reason, the function as a tsunami breakwater cannot be fulfilled unless water leakage from the dike is reduced as much as possible. Many of the conventional tsunami breakwaters are inadequate as tsunami breakwaters because it is difficult to close all the openings necessary for disaster prevention, but the tsunami breakwater of the present invention is necessary for disaster prevention. All the openings can be closed without any gaps, and the high water level entering the land side of the tsunami breakwater can be effectively prevented.

In general sense, the impact of tsunamis is immeasurable, and it may seem impossible to stop the tsunami impact with a tsunami breakwater consisting of floating bodies and impervious curtains. Although the speed is very large under the deep water conditions, the wave height is negligible because the wavelength is very long.On the other hand, as the water depth decreases as you approach the shore, it is affected by the seabed and topography. The wave height increases, but the speed is very slow. Therefore, if the material and shape of the floating body and impervious curtain that match the conditions of the location where the tsunami breakwater is provided are selected, a tsunami breakwater effective for disaster prevention can be realized.

Unlike the conventional hard tsunami breakwater, the tsunami breakwater of the present invention mainly composed of a floating body, an impermeable curtain and a tether is flexible, so that the shape of the levee body is greatly displaced when subjected to a tsunami impact. The displacement of the levee means that the impact of the tsunami does not apply to the tsunami breakwater at one time, but the magnitude of the impact is known to be inversely proportional to the square of the time at which it acts. Compared to conventional hard tsunami breakwaters, the flexible tsunami breakwater of the present invention, which requires time for displacement of the dam body when subjected to a tsunami impact, can be said to be optimal as a tsunami breakwater. In addition, since the tsunami breakwater of the present invention has an extremely large water flow blocking effect, it is possible to suppress the occurrence of accidents such as submerged excavation and breakage of the tsunami breakwater that tend to occur with the tsunami water flow.

Furthermore, since the tsunami breakwater of the present invention is a tsunami breakwater body by hanging an impermeable curtain from a floating body levitated on the sea surface and fixing the lower edge to the seabed, the conventional tsunami breakwater is There is an advantage that can be dealt with by increasing the vertical dimension of the curtain body or lengthening the tether, even at deep water sites where construction is difficult, and construction costs can be greatly reduced.

FIG. 4 is a cross-sectional view near the center of the tsunami breakwater showing another embodiment of the present invention. A tsunami breakwater with the floating body 1 and the curtain 3 near the seabed is shown. The floating body shown here is an air sac 22 made of a flexible, tough material with very little gas permeation. A pipe 14 and a valve 15 for supplying gas are attached to the air sac. When the air sac is stored near the seabed, the air sac is filled with gas when it is necessary to expand the levee body. And give buoyancy. Since the air sac that becomes a floating body when stored near the seabed 5 is not filled with gas, it is not bulky, and it is difficult to obstruct the navigation and water flow of the ship. When filling the air sac with gas, the gas flows at a high speed, and the air sac does not need to be drained.

FIG. 5 is a cross-sectional view near the center of the tsunami breakwater showing another embodiment of the present invention, and shows the tsunami breakwater stored in the seabed. The floating body shown here is a gas container 23 made of a hard material such as steel or high-strength concrete. A necessary number of gas containers having dimensions suitable for production and transportation installation are prepared, and these may be used in series, and devices such as a pipe 14 and a valve 15 for supplying gas are attached to the gas container. In addition to filling the gas container with gas when the gas container is stored near the seabed and need to expand the levee body when it needs to be expanded, the floating body is kept near the seabed. There is a method in which an openable / closable floating body levitation restraint device 10 for placing is provided and stored near the seabed in a state where a gas container is filled with gas in advance. According to the latter method, there is an advantage that the tsunami breakwater can be deployed more quickly.

  If the floating body is equipped with a gas generator that uses chemical changes including combustion, the piping for supplying gas to the floating body, the pressure accumulator, etc. can be omitted, and accidents related to wear of the piping and pressure accumulator can be avoided. can do. This further improves the reliability of the tsunami breakwater that must be maintained in good condition until the tsunami occurs.

FIG. 6 is a bird's-eye view of the tsunami breakwater 16 in another embodiment of the present invention. In general, most of the coastal population and social capital tend to concentrate in the city 17 with the bay, the gulf coast, and the port, and the areas where construction of tsunami breakwaters is strongly desired overlap. For these reasons, to effectively protect many people on the coast and social capital from damage caused by the tsunami, construct a tsunami breakwater that closes the narrow harbor 18 at the entrance of the bay, bay, and port. Compared to the construction of a tsunami breakwater in the vicinity 19 for a long time, disaster prevention effects can be obtained with much less cost and time. The end 20 of the tsunami breakwater is led and fixed to a point where a safe height can be secured for on-land disaster prevention. If necessary for disaster prevention, the tsunami breakwater of the present invention can be installed at various points such as the vicinity of the river mouth, water supply, and strait, in addition to the narrow inlets, bays, and ports.

FIG. 7 is a cross-sectional view near the center of the tsunami breakwater showing another embodiment of the present invention, and shows the tsunami breakwater in a state of receiving the high water level of the tsunami. This tsunami breakwater is provided with a plurality of anchoring points 24 at appropriate intervals on the curtain from the upper edge of the impermeable curtain 3 hanging on the seabed 5 to the seam anchoring point 6 of the lower edge. A plurality of anchoring points 8 placed on the side seabed are connected by a mooring line 9. As a result, the pressure received by the curtain can be distributed and applied to a number of fixing points provided on the seabed, and the downward force indicated by the arrow 25 acting on the floating body when subjected to a tsunami impact is greatly reduced. Can be made. The mooring line in the figure is equipped with an impact buffering device 26 for reducing the impact acting on the mooring line.

For comparison, FIG. 8 shows a tsunami breakwater that does not have a plurality of anchoring points on the curtain body 3 that hangs on the seabed 5 and does not have a plurality of tethers connected thereto. In this case, the pressure received by the curtain body is concentrated only on the fixing points provided on the floating body and the seabed, and the downward force acting on the floating body when subjected to the impact of the tsunami is large.

The tsunami breakwater of Example 7 uses a tether network in which a plurality of tethers are coupled in a net pattern. This is a network formed by combining a plurality of tethers in a planar or three-dimensional manner, and the force applied to the tethers can be distributed to a number of tethers. In addition, the tether net also has the effect of protecting the curtain from damage caused by drifting objects that tend to accompany the tsunami flow.

FIG. 9 shows another embodiment of the present invention, and is a cross-sectional view near the central part of the tsunami breakwater of the present invention installed at a point where the water depth is large. The tsunami breakwater, since the water depth is large, the vertical dimension of the impermeable curtain 3 dripping on the seabed 5 is increased, the appropriate one Makutai the edge of a Makutai to Makutai lower edge seabed fixed point 6 A plurality of fixing points 24 are provided at intervals, and a plurality of fixing points 8 placed on the offshore seafloor of the floating body are connected by a tether 9. This tsunami breakwater can disperse and bear the pressure received by the curtains at a number of fixing points on the sea floor, and can reduce the downward force acting on the floating body when subjected to the impact of the tsunami Therefore, a large tsunami suppression effect can be obtained even when it is provided at a point with a large depth, which has been considered difficult in the past.

FIG. 10 is a cross-sectional view near the center of the tsunami breakwater showing another embodiment of the present invention, and shows the tsunami breakwater in a state of receiving the high water level of the tsunami. This tsunami breakwater uses anchor bolt 28 means for fixing the bottom edge seabed anchoring point of the impermeable curtain hanging on the seabed 5 and a plurality of anchoring points placed on the offshore seafloor of the floating body. By causing the anchor bolts to reach the bedrock 27, which is strong on the seabed, the pressure applied to the curtain can be distributed and borne at the anchoring points on the seabed, and the force acting on the floating body when subjected to a tsunami impact It can be absorbed into the bedrock.

  The tsunami breakwater of the present invention can be applied to high waves and storm surges other than tsunami.

It is a cross-sectional view near the central part of the tsunami breakwater of the present invention . It is a cross-sectional view near the central part of the tsunami breakwater showing one embodiment of the present invention . It is a cross-sectional view near the central part of the tsunami breakwater showing another embodiment of the present invention . It is a cross-sectional view near the central part of the tsunami breakwater showing another embodiment of the present invention . It is a cross-sectional view near the central part of the tsunami breakwater showing another embodiment of the present invention . It is a tsunami breakwater bird's-eye view which shows the other Example of this invention . It is a cross-sectional view near the central part of the tsunami breakwater showing another embodiment of the present invention . It is a cross-sectional view near the central part of the tsunami breakwater for comparison . It is a cross-sectional view near the central part of the tsunami breakwater showing another embodiment of the present invention . It is a cross-sectional view near the central part of the tsunami breakwater showing another embodiment of the present invention .

DESCRIPTION OF SYMBOLS 1 Floating body 2 Land side lower part of floating body 3 Actuator body 4 Actuator lower edge part 5 Sea bottom 6 Adhering point of lower part of curtain body 7 Offshore side 8 Adhering point off the seabed 9 Mooring line 10 Floating body suspension control device 11 High water level 12 Floating land side 13 Actuator upper part 14 Piping 15 Valve 16 Invention Tsunami breakwater 17 Cove, bay, city with harbor 18 Cove, bay, port narrowed place 19 Near shoreline 20 End of tsunami breakwater 21 Sea surface 22 Air sac 23 Hard gas container 24 Adhering point on curtain 24 25 Arrow indicating downward force acting on floating body 26 Shock absorber 27 Rock bed 28 Anchor bolt

Claims (6)

The impervious curtain is suspended from the floating body that floats on the sea surface, and the lower edge of the curtain body is fixed to the seabed, and the anchoring point placed on the seafloor off the floating body and the floating body are connected by multiple tethers, and the center of the floating body The bottom edge of the bottom of the curtain that hangs from the center of the floating body to the bottom of the seafloor In addition to the water depth assumed at the time of the tsunami attack, the dimension up to the anchoring point is 50% longer than the water depth. It has a floating body levitation mechanism. Tsunami breakwater that emerges before.   2. The tsunami breakwater according to claim 1, wherein the height of the floating body that floats on the sea surface is smaller than the height of the tsunami that assumes an attack. The tsunami breakwater according to claim 1 or 2, further comprising a gas body generating device by chemical change including combustion for the floating of the floating body. 4. The method according to claim 1, wherein a plurality of fixing points are provided on the curtain body hanging on the seabed, and the plurality of fixing points placed on the offshore seafloor of the floating body are connected by a mooring line. Tsunami breakwater. The tsunami breakwater according to any one of claims 1 to 4, wherein a mooring network in which a plurality of mooring lines are coupled in a net shape is used instead of the mooring line . The impermeable curtain is hung from the floating body that floats on the sea surface, and the lower edge of the curtain is fixed to the sea floor using anchor bolt means, and the anchor is fixed using anchor bolt means placed on the offshore seabed of the floating body. The point and the floating body are connected by a plurality of tethers so that the center of the floating body is located on the offshore side at a distance corresponding to 50 to 200 percent of the high tide depth during normal times from the direct Shanghai surface at the anchoring point of the bottom edge of the curtain. The size from the center of the floating body to the bottom edge seabed anchoring point hanging from the center of the floating body is 50% to 200% longer than the water depth assumed when the tsunami strikes. The tsunami breakwater according to any one of claims 1 to 5 .