JP4780386B2 - Tidal Flat Breakwater - Google Patents

Description

  The present invention relates to a tidal flat breakwater.

  Conventionally, with respect to breakwaters, emphasis has been placed on physical functions to prevent waves coming from the open sea, and there are many examples lacking consideration for coexistence with the natural environment and landscapes in the sea area. On the other hand, in recent years, artificial tidal flats have been created in various places from the viewpoint of nature restoration projects concerned about the disappearance of natural tidal flats by landfill and effective use of dredged soil.

  As a typical example of the artificial tidal flat 19, a tidal flat surface 22 that gently descends from the land side 20 to the sea side 21 is formed in the rear area of the breakwater, and is installed at the tip of the slope. Many of the submerged dike 23 are used to attenuate waves. In addition, dredged soil is poured into the lower layer of the artificial tidal flat 19, while the upper layer is covered with mountain sand or sea sand to ensure the stability of the tidal flat surface 22 due to waves.

  Thus, when the artificial tidal flat 19 is created in the back area of the breakwater, not only the physical function to prevent waves but also the function of nature coexistence can be provided. This breakwater makes the seascape better than conventional breakwaters, but the stability of artificial tidal flats is less effective for wave suppression and flow control, making it difficult to ensure stability over the long term. is there. Therefore, when building a breakwater, securing the stability of the artificial tidal flat against waves and flows is an issue.

Moreover, as another breakwater, there exists invention of Unexamined-Japanese-Patent No. 2003-239241, for example.
JP 2003-239241 A

  However, in the above-mentioned breakwater, the submerged dike expecting the wave attenuation effect will reduce the wave-dissipating effect due to the limitation of the depth of the seafloor and the width of the top edge of the seabed. As a result, it is difficult to inhabit the organisms. In addition, if a flat tidal flat that gently descends from the land side to the sea side is formed, the amount of dredged soil that can be thrown in will be reduced, making it unsuitable from the viewpoint of effective use of dredged soil. In addition, when the artificial tidal flat is simply installed behind the breakwater, the artificial tidal flat flows out due to the flow induced by the breakwater (the beach current) when a wave strikes, so it has a function to control the flow effectively. It is important to secure a tidal flat breakwater.

  The present invention has been made in view of the above problems, and its purpose is to reduce long-term stability by reducing the movement and outflow of artificial tidal flats due to the action of waves, and to coexist with nature. The purpose is to provide a tidal flat breakwater that improves the seascape.

  The tidal flat breakwater of the present invention for solving the above-mentioned problems is that a breakwater is installed offshore as appropriate, and a curved submergence opening on the breakwater side is installed between the breakwater and the shore. The feature is that the tidal flat part is formed by throwing tidal flat materials into the space surrounded by the dike and breakwater. In addition, the curved submerged bank is shorter than the breakwater. In addition, the breakwater includes a curved shape opened to the submerged dam side. In addition, a frustoconical breakwater dike is installed at both ends of the breakwater, and the breakwater dike is installed with earth retaining dike extending toward the curved dike. In addition, it is included that the earth retaining dike extending to the curved dike side was installed at both ends of the breakwater. The tidal flat material includes an inclined surface or a horizontal surface that gradually increases toward the breakwater side. It also includes that the tidal flat and the shore were connected by the input material being thrown in between the dragonfly extending from the shore formed behind the curved submarine due to the action of the waves and the curved submerged dike.

  Along with the formation of a tidal flat breakwater that functions as a symbiotic nature, the landscape of the sea area is improved, creating an aminity space and a hydrophilic space for people from the conventional inorganic space. In addition, the tidal flat formed behind the breakwater improves the breakwater stability of the breakwater. In addition, the curved submarine installed between the breakwater and the shore suppresses the wave-induced flow in the area behind the breakwater, thus reducing the movement and outflow of artificial tidal flats and providing long-term stability. In addition, wave scouring can be reduced by the wave breakwater installed at the end of the breakwater, and seawater exchange necessary for living creatures such as clams can be achieved by partial transmission by diffraction.

  Hereinafter, embodiments of the tidal flat breakwater of the present invention will be described with reference to the drawings. In each embodiment of the tidal flat breakwater, the same configuration will be described using the same reference numerals, and only different configurations will be described with different reference numerals.

  1-3 is the tidal flat breakwater 1 of 1st Embodiment. The tidal flat breakwater 1 is a flat-bow-shaped breakwater 3 that opens to the shore side that is set off from the shore 2 as appropriate, and opens toward the breakwater side that is installed between the breakwater 3 and the shore 2 The flat arch-shaped curved submergence 4 and the tidal flat part 6 composed of the tidal flat material 5 such as earth and sand introduced into the space surrounded by the breakwater 3 and the curved submerged dike 4 An inclined surface 7 or a horizontal surface that gently slopes downward from the breakwater side toward the shore side, and both sides are inclined surfaces 8 that slope downward toward the outside. The inclined surface 8 gradually narrows toward the tip. It becomes a flat triangle.

  The curved submerged bank 4 is trapezoidal or convex in section, shorter than the breakwater length L, 0.3 to 0.8 L relative to the breakwater length L, and from the breakwater 3 to 0. It is preferable to install at a position of 5 to 1.5 L. This is to allow the curved submerged bank 4 to properly exert the flow control effect and to prevent the tideland material 5 from flowing out or being scoured and becoming unstable by preventing direct erosion of the waves.

  On the other hand, the breakwater 3 also has a flat bow shape that opens toward the shore side, and frustoconical wave breakwater 9 is formed at both ends, and the wave breakwater 9 has a trapezoidal cross section extending toward the curved breakwater side. The earth retaining submarine 10 is formed. Thus, since the tidal flat portion 6 is surrounded by the breakwater 3 and the earth retaining dike 10 and the curved submerged dike 4 whose both ends extend toward the dirt retaining dike, the movement and outflow due to the flow of the tidal flat material 5 is effectively performed. It can be suppressed. In addition, the wave breakwater 9 allows the partial penetration of waves to the tidal flat 6 and has a function of promoting the exchange of seawater necessary for the inhabiting of benthic organisms such as clams, so that the tidal flat 6 is benthic. It is also a habitat of

  Further, FIG. 4 shows a structure in which a trapezoidal earth retaining dike 10 having a trapezoidal cross section extending toward the curved dike side is formed at both ends of the flat bow-shaped breakwater 3 without providing the wave breaking dike 9. Except that is not formed, it has the same configuration as the tidal flat breakwater 1 described above.

  FIG. 5 shows a case where the incident wave height is 1 m, which is an example of the analysis result of the beach current when the curved submerged bank 4 is not installed and when the curved submerged bank 4 is installed. Since the average flow velocity on the tidal flat when not installed is 0.12 m / s, the average flow velocity on the tidal flat when installing the curved submarine 4 is 0.07 m / s. The average flow velocity on the tidal flat is smaller when the submarine 4 is installed.

  Moreover, FIG. 6 shows an example of the analysis result of the beach current on the representative survey lines 11 and 12 in (1) and (2) of FIG. 5, and according to this, the tidal flat when the curved submergence 4 is not installed is shown. The flow velocity on the tidal flat when the curved submergence 4 is installed is smaller than the flow velocity on the portion.

  As a result, it was possible to confirm the above-mentioned effect that the movement and outflow due to the waves and flow of the tidal flat material 5 were effectively suppressed. In addition, although the said breakwater 3 was demonstrated with the planar arch shape, this may not be limited to a planar arch shape but may be linear.

  7 and 8 show a tidal flat breakwater 13 according to the second embodiment. The tidal flat breakwater 13 uses a dragonfly 14 extending from the shore 2 formed behind the curved submerged dam 4 due to the action of waves, and earth, sand, gravel, stone or stone between the dragonfly 14 and the curved submerged dam 4. An input material 15 such as a granulated material is input to connect the tidal flat portion 5 and the shore 2, and the other configuration is the same as that of the tidal flat breakwater 1 of the first embodiment. When the earth and sand 15 is added to the dragonfly 14 in this way, when it is at low tide, it becomes a connecting path 16 and people can walk across the tidal flat part 6.

  FIG. 9 shows tidal flat breakwaters 17 and 18 according to the third embodiment. Of these, the tidal flat breakwater 17 in FIG. (1) is obtained by changing the breakwater 3 from a flat bow to a straight line and removing the breakwater dike 9 and the earth retaining dike 10; It has the same structure as the tidal flat breakwater 13 and has the same effect. In addition, the tidal flat breakwater 18 in FIG. 2 is a straight breakwater 3 inclined in a predetermined direction, and a flat bow-shaped curved submergence line 4 and a retaining ring dike 10 are installed. It has the same structure as the tidal flat breakwater 17 of (2) and has the same effect. In this structure, the curved submerged wall 4 is formed to be inclined at a predetermined angle with respect to the straight breakwater 3.

It is a top view of the tidal flat breakwater of 1st Embodiment. It is a perspective view of the tidal flat breakwater of 1st Embodiment. (1) is the sectional view on the AA line of FIG. 1, (2) is the sectional view on the BB line. It is a top view of a tidal flat breakwater that does not form a wave breaker. It is the figure which showed the analysis result of the beach current when not installing a curved submerged bank and installing a curved submerged bank. It is the figure which showed the analysis result of the beach current on the typical survey line in (1) and (2) of FIG. It is a top view of the tidal flat breakwater of 2nd Embodiment. (1) is the CC sectional view taken on the line of FIG. 7, (2) is the DD sectional view taken on the line. (1) And (2) is a top view of the tidal flat breakwater of 3rd Embodiment. It is sectional drawing of the conventional tidal flat breakwater.

Explanation of symbols

1, 13, 17, 18 Tidal Flat Breakwater 2 Banks 3 Breakwater 4 Curved Submarine 5 Tidal Flat Material 6 Tidal Flat Section 7, 8 Inclined Surface 9 Wave Breaking Submerged 10 Distillation Submarine 11, 12 Representative Side Line 14 Tonboro 15 Input Material 16 Connection Road 19 Artificial tidal flat 20 Land side 21 Sea side 22 Tidal flat surface 23 Submarine

Claims (7)

  A breakwater is installed offshore as appropriate from the shore, a curved submarine opened toward the breakwater side is installed between the breakwater and the shore, and tidal flat material is placed in the space surrounded by the curved submerged wall and the breakwater. A tidal flat breakwater characterized by the formation of a tidal flat.   The tidal flat breakwater according to claim 1, wherein the curved submarine is shorter than the breakwater.   The tidal flat breakwater according to claim 1 or 2, characterized in that the breakwater has a flat bow shape opening toward the submerged breakwater side.   4. A frustoconical wave breakwater dike is installed at both ends of the breakwater, and an earth retaining dike extending toward the curved dike is installed in the wave breakwater. The tidal flat breakwater described in.   The tidal flat breakwater according to any one of claims 1 to 4, wherein earth retaining dike extending toward the curved submerged wall is installed at both ends of the breakwater.   The tidal flat breakwater according to any one of claims 1 to 5, wherein the tidal flat portion is an inclined surface or a horizontal plane that gently descends and slopes from the breakwater side toward the shore side.   The input material is thrown in between the dragonfly extended from the shore formed behind the curved submerged by the action of waves and the curved submerged dike, and the tidal flat and the shore are connected. The tidal flat breakwater according to any one of 6 above.

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