JP2024062017A - Floating artificial tidal flats - Google Patents

Abstract

[Problem] When a floating artificial tidal flat sways due to the influence of waves, the amplification of swaying caused by the movement of water stored in the floating artificial tidal flat is suppressed. [Solution] A floating artificial tidal flat that floats on the water surface, comprising a floating structure 20 having a bottom plate 21 and vertical walls 22, 23 erected like a fence around the periphery of the bottom plate 21 and configured to float on the water surface, and a base 30 that covers the bottom plate 21 inside the vertical walls 22, 23 of the floating structure 20 and forms a tidal flat by being partially submerged in the water stored in the floating structure 20, and the base surface 32f of the base 30 that can come into direct contact with water has a height dimension that continuously decreases from one end side in the direction along the traveling direction W of the waves around the floating structure 20 toward the center, and a height dimension continuously increases from the center toward the other end. [Selected Figure] Figure 3

Description

The present invention relates to a floating artificial tidal flat that can be floated on the water surface.

Technology relating to artificial tidal flats is described in Patent Document 1. The artificial tidal flat 100 described in Patent Document 1 is intended to restore a coastal area rich in living creatures. As shown in FIG. 11, the artificial tidal flat 100 is constructed by constructing coastal soil 103 that slopes gently downward from an upright revetment 101 toward the offshore direction, and the surface of the coastal soil 103 is partially submerged in seawater K. Furthermore, a wave-dissipating wall 105 for blocking waves is installed at the offshore tip of the coastal soil 103.

In the case of the artificial tidal flat 100 described above, the scale of the facilities is large, so the locations where it can be installed are limited. For this reason, when an artificial tidal flat is to be installed near a facility such as an aquaculture farm, a floating artificial tidal flat as shown in Patent Document 2 is preferably used. In the case of a typical floating artificial tidal flat 110, as shown in FIG. 12, it is equipped with a floating structure 112 that floats on the sea surface, and a base portion 114 that is installed inside the floating structure 112 to imitate the coastal soil 103 of the artificial tidal flat 100. A specified amount of seawater K is stored inside the floating structure 112. The base surface 114s with which the seawater comes into direct contact in the base portion 114 is formed to gently slope downward toward the sea, like the coastal soil 103 of a typical artificial tidal flat 100.

Patent No. 4566145 Japanese Patent Application Laid-Open No. 7-124592

As described above, the base surface 114s of the base portion 114 of the floating artificial tidal flat 110 is formed to slope gently downward toward the ocean, as shown in Figure 12. For this reason, for example, as shown in Figure 13, when the ocean surface waves push up the offshore end 112x (right side) of the floating structure 112 and the shore end 112y (left side) moves down, the seawater K in the floating structure 112 moves leftward, climbing the slope of the base surface 114s. In this case, the base surface 114s acts as a resistance to the movement of the seawater K, and the displacement X1 of the center of gravity G of the seawater K becomes relatively small. Next, as shown in FIG. 14, when the shore end 112y (left side) of the floating structure 112 is pushed up by the waves on the ocean surface and the offshore end 112x (right side) descends, the base surface 114s does not resist the movement of the seawater K, and the seawater K flows down to the right along the base surface 114s. As a result, the speed at which the seawater K moves increases, and the amount of movement increases, and the displacement X2 of the center of gravity G of the seawater K becomes large. Therefore, as shown in FIG. 14, the right side of the floating structure 112 sways more when it descends. In other words, the swaying of the floating artificial tidal flat 110 caused by the waves on the ocean surface is further amplified by the movement of the seawater K inside the floating structure 112.

The present invention was made to solve the above problems, and the problem that the present invention aims to solve is to suppress the amplification of the swaying caused by the movement of water stored in a floating artificial tidal flat when the floating artificial tidal flat sways due to the influence of waves.

The above problems are solved by each invention. The first invention is a floating artificial tidal flat that floats on the water surface, comprising a floating structure that includes a bottom plate and a vertical wall that stands like a fence on the periphery of the bottom plate and is configured to float on the water surface, and a base that covers the bottom plate inside the vertical wall of the floating structure and is partially submerged in the water stored in the floating structure to form a tidal flat, and the base surface that can directly come into contact with water in the base decreases in height in a stepped or continuous manner from one end side in the direction along the traveling direction of the waves around the floating structure toward the center, and increases in height in a stepped or continuous manner from the center toward the other end.

According to the present invention, the height dimension of the base surface decreases stepwise or continuously as it approaches the center from one end in the direction along the wave propagation direction around the floating structure, and increases stepwise or continuously as it approaches the other end from the center. That is, the side shape of the base surface is formed in an approximately valley shape, and the height dimension is large at one end and the other end, and the height dimension at the center is small. Therefore, the center of the base surface and its vicinity are submerged. Then, when one end of the floating structure is pushed up and the other end is lowered by the influence of the waves, the water in the floating structure 112 moves up the slope of the base surface from the center to the other end. Also, when the other end of the floating structure is pushed up and the one end is lowered by the influence of the waves, the water in the floating structure 112 moves up the slope of the base surface from the center to the one end. In this way, when the floating structure is affected by waves, the water inside the floating structure 112 moves up the slope of the base surface, making it difficult for the water to move from the center to one end or the other end. Furthermore, the water inside the floating structure moves an approximately equal amount to one end and the other end of the base surface. As a result, the swaying at one end and the other end due to the movement of water is approximately equal. In other words, when the floating artificial tidal flat sways due to the effect of waves, the amplification of the swaying caused by the movement of the water stored inside can be suppressed.

The second invention is a floating artificial tidal flat that floats on the water surface, comprising a floating structure that is configured to float on the water surface and includes a bottom plate and a vertical wall that is erected like a fence around the periphery of the bottom plate, and a base that covers the bottom plate inside the vertical wall of the floating structure and is partially submerged in the water stored in the floating structure to form a tidal flat, and the base surface that can directly come into contact with water in the base increases in height in a stepped or continuous manner from one end side in the direction along the wave propagation direction around the floating structure toward the center, and decreases in height in a stepped or continuous manner from the center toward the other end.

According to the present invention, the height dimension of the base surface increases stepwise or continuously from one end side in the direction along the wave propagation direction around the floating structure toward the center, and decreases stepwise or continuously from the center toward the other end. That is, the side shape of the base surface is formed in an approximately mountain shape, and the height dimension is small at one end side and the other end side, and the height dimension at the center is large. Therefore, the part of the base surface except the center becomes submerged. Then, when one end side of the floating structure is pushed up and the other end side descends due to the influence of the waves, the water in the floating structure 112 becomes difficult to move to the other end side because the base surface with the approximately mountain-shaped side becomes a resistance. Also, when the other end side of the floating structure is pushed up and the one end side descends, the water in the floating structure 112 becomes difficult to move to the one end side because the base surface with the approximately mountain-shaped side becomes a resistance. Furthermore, when the floating structure sways due to the effect of waves, the water stored inside the floating structure moves by an approximately equal amount to one end and the other end of the base surface. This means that the swaying caused by the movement of water is approximately equal on one end and the other end. In other words, when the floating artificial tidal flat sways due to the effect of waves, the amplification of the swaying caused by the movement of the water stored inside can be suppressed.

According to the third invention, the base surface is composed of an upwardly sloping surface and a downwardly sloping surface. This allows the floating artificial tidal flat to be formed in a state close to nature.

According to the present invention, when a floating artificial tidal flat sways due to the effect of waves, the amplification of the swaying caused by the movement of water stored in the floating artificial tidal flat can be suppressed.

FIG. 1 is a schematic perspective view of a floating artificial tideland according to a first embodiment of the present invention. FIG. 2 is a schematic vertical cross-sectional view of the floating artificial tideland. FIG. 2 is a schematic vertical cross-sectional view showing the floating artificial tideland floating on the sea surface. FIG. 2 is a schematic vertical cross-sectional view showing the influence of ocean surface waves on the floating artificial tideland. FIG. 2 is a schematic vertical cross-sectional view showing the influence of ocean surface waves on the floating artificial tideland. FIG. 1 is a schematic vertical cross-sectional view showing a floating artificial tideland according to modified example 1 floating on the sea surface. FIG. 11 is a schematic vertical cross-sectional view showing the influence of ocean surface waves on a floating artificial tideland according to Modification 1. FIG. 11 is a schematic vertical cross-sectional view showing the influence of ocean surface waves on a floating artificial tideland according to Modification 1. FIG. 11 is a schematic perspective view of a floating artificial tideland according to modified example 2. FIG. 11 is a schematic perspective view of a floating artificial tideland according to modified example 3. FIG. 1 is a schematic vertical cross-sectional view of a conventional artificial tideland. FIG. 1 is a schematic vertical cross-sectional view showing a conventional floating artificial tideland floating on the sea surface. FIG. 1 is a schematic vertical cross-sectional view showing the influence of ocean surface waves on a conventional floating artificial tideland. FIG. 1 is a schematic vertical cross-sectional view showing the influence of ocean surface waves on a conventional floating artificial tideland.

[Embodiment 1]
A floating artificial tideland according to a first embodiment of the present invention will be described below with reference to Figures 1 to 10. The floating artificial tideland 10 according to this embodiment is a facility for cultivating aquatic organisms such as fish and shellfish that live on tideland and purifying seawater. Here, front, back, left, right, and up and down shown in the figures correspond to the front-back, left-right, and up-down directions of the floating structure 20 in the floating artificial tideland 10.

<Outline of Floating Artificial Tidal Flat 10>
1 and 2, the floating artificial tideland 10 is an artificial tideland used while floating on the sea surface S, and is configured so that it can be moored, for example, to a quay 3. The floating artificial tideland 10 comprises a floating structure 20 that is floated on the sea surface S, a base 30 that forms a tideland inside the floating structure 20, a water supply device 40 that supplies seawater to the inside of the floating structure 20, and a drainage device 50.

<Regarding the floating structure 20>
As shown in Fig. 1 and Fig. 2, the floating structure 20 is formed of steel plates or the like into a rectangular container shape with an open top. That is, the floating structure 20 includes a bottom plate portion 21, a front plate portion 22 and a rear plate portion 23 erected in front of and behind the bottom plate portion 21, and a left plate portion 24 and a right plate portion 25 erected on the left and right sides of the bottom plate portion 21. The edges of the bottom plate portion 21, the front plate portion 22, the rear plate portion 23, the left plate portion 24, and the right plate portion 25 are joined to each other by welding or the like, so that the floating structure 20 is formed into a rectangular container shape. Hooks 27 used for mooring the floating structure 20 are formed on the left and right sides of the upper surface of the front plate portion 22 and the upper left and right sides of the upper surface of the rear plate portion 23 of the floating structure 20 in a state of protruding upward. The floating structure 20 is positioned such that the front plate 22 faces offshore and the rear plate 23 faces the quay 3, and the hooks 27 are moored to the mooring posts 3p on the quay 3 side and the mooring posts 3p on the offshore side, respectively. Therefore, the fore-aft direction of the floating structure 20 is aligned with the traveling direction W of the waves on the sea surface S. Here, the dimensions of the floating structure 20 in the fore-aft and lateral directions are set to, for example, about 10 m.

<Regarding the base portion 30>
The base 30 is a part that constitutes a tidal flat inside the floating structure 20, and is configured to be close to a natural tidal flat. The base 30 covers the entire surface of the bottom plate 21 inside the floating structure 20. As shown in FIG. 2, the base 30 includes a conglomerate layer 37 composed of rocks, conglomerates, etc., a sand layer 36 laminated on the conglomerate layer 37, and a mud layer 32 laminated on the sand layer 36. The surface of the mud layer 32 is capable of directly contacting the seawater K stored inside the floating structure 20. That is, the surface of the mud layer 32 is the base surface 32f. As shown in FIG. 2, the height dimension of the base surface 32f is continuously reduced from the front plate 22 side (front end side) of the floating structure 20 toward the center. Therefore, the base surface 32f between the front end side and the center is a sloping surface with a downward slope that is low on the center side.

The height dimension of the base surface 32f increases continuously from the center of the floating structure 20 toward the rear plate 23 (rear end side). Therefore, the base surface 32f between the center and rear end side is an inclined surface with a higher upward gradient at the rear end side. That is, the side shape of the base surface 32f is formed into a substantially flattened V shape by a downward gradient inclined surface from the front end side to the center and an upward gradient inclined surface from the center to the rear end side. The center of the base surface 32f and its vicinity are configured to be submerged. Here, the inclination angle between the front end side and the center of the base surface 32f is approximately equal to the inclination angle between the rear end side and the center, and is set to, for example, 10° to 20°.

<Water supply device 40 and drainage device 50>
The water supply device 40 is a device that supplies surrounding seawater to the inside of the floating structure 20, i.e., onto the base 30. The water supply device 40 includes a water supply pump (not shown) that draws up seawater, and a water supply pipe 43 that guides the seawater drawn up by the water supply pump to the inside of the floating structure 20. The drainage device 50 is a device that discharges seawater K (seawater + rainwater) stored in the floating structure 20 from the bottom of the floating structure 20 to the outside. The drainage device 50 includes a drainage pump (not shown) that discharges the seawater K (seawater + rainwater), and a drainage pipe 53 that guides the drainage from the drainage pump to the outside. The drainage device 50 is configured to be able to discharge the seawater K (seawater + rainwater) to the outside of the floating structure 20 through the mud layer 32, the sand layer 36, and the conglomerate layer 37 of the base 30 by driving the drainage pump. Here, a level meter (not shown) that detects the level of seawater K (seawater + rainwater) is installed on the floating structure 20, and the water supply device 40 and the drainage device 50 are driven so that the level of seawater K falls within an acceptable range.

<Operation of the floating artificial tideland 10>
When the floating artificial tideland 10 is floating on the sea surface S, it sways under the influence of the waves of the sea surface S, as shown in Figures 3 to 5. Here, the floating structure 20 of the floating artificial tideland 10 is positioned so that its front-to-rear direction is along the traveling direction W of the waves of the sea surface S, as described above. For this reason, the floating structure 20 mainly sways back and forth, repeating a state in which the front plate portion 22 side is pushed up and the rear plate portion 23 side is pushed down by the influence of the waves (see Figure 4), a horizontal state (see Figure 3), and a state in which the rear plate portion 23 side is pushed up and the front plate portion 22 side is pushed down (see Figure 5). When the floating structure 20 sways back and forth, the seawater K stored in the floating structure 20 also moves back and forth in accordance with the swaying of the floating structure 20.

Here, the base surface 32f of the base portion 30 of the floating artificial tidal flat 10 has a flattened V-shaped side shape formed by a downwardly sloping surface from the front end side to the center and an upwardly sloping surface from the center to the rear end side. The inclination angle between the front end side and the center of the base surface 32f is set to be approximately equal to the inclination angle between the rear end side and the center. Therefore, the displacement amounts X1 and X2 of the center of gravity G caused by the movement of seawater K are approximately equal in the state in which the front plate portion 22 side is pushed up and the rear plate portion 23 side is lowered as shown in FIG. 4, and the state in which the rear plate portion 23 side is pushed up and the front plate portion 22 side is lowered as shown in FIG. 5. Therefore, the forward and backward sway caused by the movement of seawater K is approximately equal. Furthermore, in either the forward or backward case, the seawater K moves in the direction of climbing the inclined surface of the base surface 32f, so the movement amount of seawater K is suppressed. Therefore, when the floating artificial tideland 10 sways due to the effect of waves, the amplification of the swaying caused by the movement of the seawater K stored in the floating artificial tideland 10 can be suppressed.

<Correspondence between terms related to the first embodiment and terms related to the present invention>
The front plate 22, the rear plate 23, the left plate 24, and the right plate 25 in the floating structure 20 according to this embodiment correspond to the fence-like vertical wall portion erected on the periphery of the bottom plate of this invention. The front end side of the base surface 32f according to this embodiment corresponds to one end side in the direction along the wave traveling direction, and the rear end side of the base surface 32f corresponds to the other end side in the direction along the wave traveling direction. Furthermore, seawater K corresponds to water in this invention.

<Advantages of the floating artificial tideland 10 according to this embodiment>
According to the floating artificial tideland 10 of this embodiment, the height dimension of the base surface 32f decreases continuously from the front end (one end) in the direction along the wave travel direction W around the floating structure 20 toward the center, and increases continuously from the center toward the rear end (the other end). That is, the side shape of the base surface 32f is formed in a flattened V-shape, and the height dimension is large at the front end and the rear end, and the height dimension at the center is small. Therefore, the center of the base surface 32f and its vicinity are submerged. Then, when the front end side of the floating structure 20 is pushed up and the rear end side is lowered by the influence of the waves, the water in the floating structure 20 moves up the slope of the base surface 32f from the center to the rear end. In addition, when the rear end side of the floating structure 20 is pushed up and the front end side is lowered by the influence of waves, the water in the floating structure 20 moves up the slope of the base surface from the center to the front end side. This makes it difficult for the water in the floating structure 20 to move from the center to the front end side or the rear end side when the floating structure 20 is affected by waves. Furthermore, when the floating structure 20 sways due to the influence of waves, the water in the floating structure 20 moves by approximately equal amounts to the front end side and the rear end side of the base surface 32f. Therefore, the forward and backward swaying caused by the movement of water is approximately equal. In other words, when the floating artificial tidal flat 10 sways due to the influence of waves, the amplification of the swaying caused by the movement of the water stored inside can be suppressed.

<Modification 1>
Here, the present invention is not limited to the above embodiment, and modifications are possible within the scope of the present invention. For example, in the present embodiment, as shown in Figs. 2 and 3, the base surface 32f is formed so that the height dimension is continuously decreased from the front end side (one end side) toward the center, and the height dimension is continuously increased from the center to the rear end side (other end side). However, as shown in Figs. 6 to 8, the base surface 32f can also be formed so that the height dimension is continuously increased from the front end side (one end side) toward the center, and the height dimension is continuously decreased from the center to the rear end side (other end side). That is, the base surface 32f can be formed so that the height dimension is small at the front end side and the rear end side, and the height dimension is large at the center, so that the side shape is a flat mountain shape. In this case, the base surface 32f is submerged in seawater K except for the center and its vicinity.

As a result, when the front end of the floating structure 20 is pushed up and the rear end is lowered by the influence of waves, as shown in FIG. 7, the seawater K in the floating structure 20 moves to the rear end, but the movement of the seawater K is restricted by the resistance of the flat mountain-shaped base surface 32f. Also, as shown in FIG. 8, when the rear end of the floating structure 20 is pushed up and the front end is lowered, the seawater K in the floating structure 20 moves to the front end, but the movement of the seawater K is restricted by the resistance of the flat mountain-shaped base surface 32f. Furthermore, when the floating structure 20 sways due to the influence of waves, the seawater K in the floating structure 20 moves forward and backward by approximately equal amounts. Therefore, the forward and backward swaying due to the movement of water is approximately equal. In other words, when the floating artificial tidal flat 10 sways due to the influence of waves, the amplification of the swaying due to the movement of the seawater K stored inside can be suppressed.

<Modification 2>
In this embodiment, as shown in Fig. 3 etc., the base surface 32f is formed such that the side shape is a flattened V-shape, with a downwardly sloping surface from the front end side to the center and an upwardly sloping surface from the center to the rear end side. However, as shown in Fig. 9, the base surface 32f can also be formed in a concave pyramid shape, with the center and its vicinity submerged in seawater K. This makes it possible to suppress the amplification of rocking of the floating structure 20 caused by the movement of seawater K not only when the floating structure 20 rocks back and forth, but also when the floating structure 20 rocks left and right.

<Modification 3>
In this embodiment, as shown in Fig. 6 etc., an example has been shown in which the base surface 32f is formed so that the side shape is a flat mountain shape. However, as shown in Fig. 10, the base surface 32f may be formed in a pyramid shape so that the part other than the central part and its vicinity is submerged in the seawater K. This makes it possible to suppress the amplification of the rocking motion of the floating structure 20 caused by the movement of the seawater K not only when the floating structure 20 rocks back and forth but also when the floating structure 20 rocks left and right.

＜Other＞
In the present embodiment, as described above, an example in which the base surface 32f is formed by a combination of inclined surfaces has been shown. However, instead of forming the base surface 32f by an inclined surface, it is also possible to form the base surface 32f by a plurality of steps. This makes it possible to efficiently suppress the movement of seawater K in the floating structure 20. In addition, in the present embodiment, as shown in FIG. 1, an open-top type floating structure 20 has been exemplified, but it is also possible to use a floating structure 20 with a roof. In addition, in the present embodiment, as shown in FIG. 1, a planar rectangular floating structure 20 has been exemplified, but the planar shape of the floating structure 20 can be appropriately changed according to the planar shape of the installation site. Furthermore, in the present embodiment, a floating artificial tideland 10 used in the sea has been exemplified, but the floating artificial tideland 10 according to the present invention can also be used in lakes, marshes, and rivers.

10: Floating artificial tideland 20: Floating structure 21: Bottom plate portion 22: Front plate portion (vertical wall portion)
23: Rear plate portion (vertical wall portion)
24: Left plate portion (vertical wall portion)
25...Right plate (vertical wall)
30: Base portion 32f: Base surface K: Seawater S: Sea surface (water surface)
W: Wave direction

Claims (3)

A floating artificial tidal flat that floats on the water surface,
A floating structure including a bottom plate portion and a vertical wall portion erected like a fence on a periphery of the bottom plate portion and configured to float on the water surface;
a base portion that covers the bottom plate portion inside the vertical wall portion of the floating structure and that forms a tidal flat by being partially submerged in water stored in the floating structure;
It has
The base surface with which water can directly come into contact at the base has a height dimension that decreases stepwise or continuously from one end in the direction along the wave propagation direction around the floating structure toward the center, and a height dimension that increases stepwise or continuously from the center toward the other end. A floating artificial tidal flat that floats on the water surface,
A floating structure including a bottom plate portion and a vertical wall portion erected like a fence on a periphery of the bottom plate portion and configured to float on the water surface;
a base portion that covers the bottom plate portion inside the vertical wall portion of the floating structure and that forms a tidal flat by being partially submerged in water stored in the floating structure;
It has
The base surface with which water can directly come into contact at the base has a height dimension that increases stepwise or continuously from one end in the direction along the wave propagation direction around the floating structure toward the center, and the height dimension decreases stepwise or continuously from the center toward the other end. The floating artificial tideland according to claim 1 or 2,
The floating artificial tidal flat, wherein the base surface is composed of an upwardly sloping surface and a downwardly sloping surface.

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