Scour prevention structure

Abstract

To provide a scour prevention structure capable of effectively preventing scour around a foundation.SOLUTION: The scour prevention structure is provided around a foundation 51 in water, and includes a first bag-packed cohesive soil material 41 disposed along the periphery of the foundation, and a second bag-packed cohesive soil material 42 disposed around the first bag-packed cohesive soil material so as to surround the first bag-packed cohesive soil material in a plan view, and the second bag-packed cohesive soil material has a plane area larger than a plane area of the first bag-packed cohesive soil material in a plan view. A third bagged root fixing material having a plane area larger than that of the first bagged root fixing material is arranged in place of the first bagged root fixing material at every predetermined angle in the periphery of the foundation in a plan view.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a scour prevention structure. [Background technology]

[0002] Offshore wind power generation is a renewable energy source with low carbon dioxide emissions, and has features such as stronger winds than on land, less fluctuation in wind speed, and more stability, which has led to its introduction into power generation businesses. Monopiles (single piles) are often used as the foundation type for offshore wind power generation facilities. Generally, monopile foundations have a large foundation diameter, so measures to prevent scouring around the foundation due to waves and tidal currents are taken. As a measure to prevent scouring, for example, crushed stone known as a filter layer is laid on the surface of the seabed ground, and bagged root protection material known as an armor layer is layered on top of that (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6986119 Summary of the Invention [Problem to be solved by the invention]

[0004] Since the bagged foot protection material is circular in plan view, the armor layer is often arranged in a ring shape around the monopile foundation, with the outside of that in a honeycomb (hexagonal) shape. Also, to prevent localized scouring around the monopile foundation, a structure is adopted in which bagged foot protection material with a small planar area is used around the monopile foundation, and bagged foot protection material with a large planar area is used on the outside. However, the above structure had the problem of large gaps that were weak points against scouring at the boundary between the small-area bagged root protection material and the large-area bagged root protection material. One solution was to stack more bagged root protection material on top of this gap, but this solution was limited because the gaps would still be the same thickness as the lower layer.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a scour prevention structure that can effectively prevent scouring around a foundation. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the scouring prevention structure of the present invention is a scouring prevention structure that is provided around an underwater foundation, and comprises a first bagged root fixation material arranged along the periphery of the foundation, and a second bagged root fixation material arranged around the first bagged root fixation material so as to completely surround the first bagged root fixation material in a planar view, wherein the second bagged root fixation material has a planar area larger than that of the first bagged root fixation material in a planar view, and a scouring prevention structure in which third bagged root fixation materials having a planar area larger than that of the first bagged root fixation material are arranged in place of the first bagged root fixation material at predetermined angles around the foundation in a planar view.

[0007] With this configuration, gaps formed between the first and second bagged root fixation materials can be reduced or eliminated by using third bagged root fixation materials that have a larger planar area than the first bagged root fixation materials and are placed at a predetermined angle around the foundation, thereby effectively preventing underwater scouring around the foundation.

[0008] In addition, in the scouring prevention structure of the present invention, the third bagged root protection material may be the same size as the second bagged root protection material.

[0009] By using the above configuration, the desired scour prevention structure can be constructed using two types of bagged root protection materials, and construction efficiency can also be improved.

[0010] In the scour prevention structure of the present invention, the predetermined angle may be 90°.

[0011] With the above configuration, the desired scour prevention structure can be constructed simply by placing the third bagged root protection material in place of the first bagged root protection material at four locations around the foundation, every 90°, thereby improving construction efficiency.

[0012] In the scour prevention structure of the present invention, the predetermined angle may be 45°.

[0013] With the above configuration, it is possible to construct the desired scouring prevention structure, which can reduce the gap area in plan view, simply by placing the third bagged root fixation material in place of the first bagged root fixation material at eight locations every 45° around the foundation.

[0014] In addition, in the scouring prevention structure of the present invention, the second bagged root fixation material may be layered and laid on top of the layer on which the first bagged root fixation material, the second bagged root fixation material, and the third bagged root fixation material are arranged.

[0015] By adopting the above-described configuration, a scour prevention structure with an upper and lower two-layer structure can be constructed, and scouring around the foundation can be prevented more effectively. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a scour prevention structure that can effectively prevent scouring around a foundation such as an underwater monopile foundation, for example. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a perspective view of a scour prevention structure according to an embodiment of the present invention. [Figure 2] FIG. 2 is a side view of the scour prevention structure according to the present embodiment. [Figure 3] 1 is a plan view (1) of a scour prevention structure according to the present embodiment. [Figure 4]FIG. 2 is a plan view (2) of the scour prevention structure according to the present embodiment. [Figure 5] FIG. 10 is a side view showing the hanging state of bagged root protection materials above water in the construction method of the scour prevention structure according to this embodiment. [Figure 6] FIG. 6 is a front view taken along line AA in FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0018] A scour prevention structure according to an embodiment of the present invention will be described below with reference to Figures 1 to 6. In this embodiment, a scour prevention structure is constructed on the seabed around the base of a monopile-type offshore wind power generation device (offshore wind turbine) installed in the sea.

[0019] 1 and 5, the monopile structure 5 in this embodiment is a monopile-type offshore wind power generation device installed on the sea. The monopile structure 5 includes a monopile foundation 51, an overhanging scaffolding 52, a tower section 53, mooring and lifting equipment 54, and a power transmission cable 55.

[0020] The monopile foundation 51 exerts a desired bearing force against waves and tidal currents to support the monopile structure 5. The monopile foundation 51 has a cylindrical outer shape, and a scour prevention structure 10 is provided on the seabed edge 6, which is the edge of the foundation on the seabed.

[0021] The cantilever scaffolding 52 is provided on the offshore portion 51a of the monopile foundation 51, and includes an outer peripheral portion 52a that is generally circular in plan view and protrudes outward from the outer peripheral surface of the monopile foundation 51, and a cantilever portion 52b that protrudes further outward from a part of the outer peripheral portion 52a. The cantilever scaffolding 52 is used for maintenance work on the monopile structure 5 and as a temporary storage area for machinery and equipment.

[0022] The tower section 53 is the wind turbine section that generates electricity and is attached to the top of the monopile foundation 51. The tower section 53 is formed with a known configuration. For example, the tower section 53 includes a tower connected to the top of the monopile foundation 51, a nacelle that is connected to the top of the tower and stores the generator and other components, blades that form the wind turbine, a hub that connects the nacelle and the blades, and a connection section that connects the monopile foundation 51 and the tower.

[0023] The mooring and lifting equipment 54 is connected to the cantilever scaffolding 52 and provided on the offshore section 51a, and is used as an access facility from the sea for workers performing maintenance work on the monopile structure 5. The mooring and lifting equipment 54 comprises a mooring section for accessing the monopile structure 5 from the sea, and a lifting facility (fixed ladder) for accessing the cantilever scaffolding 52 from the mooring section.

[0024] The power transmission cable 55 electrically connects the tower section 53 to a power receiving facility (not shown) that is provided on land and receives the power generated by the monopile structure 5, and the power generated by the tower section 53 is transmitted to the power receiving facility by the power transmission cable 55. The power transmission cable 55 extends from the tower section 53 through the monopile foundation 51 to the seabed, and is laid on the seabed to reach the power receiving device, thereby supplying the power generated by the tower section 53.

[0025] The monopile structure 5 is constructed by a known construction method, which includes, for example, a step of transporting the monopile foundation 51 to the construction site and casting it, a step of forming a filter layer 11 on the seabed periphery 6, a step of forming a bagged root protection layer 12 on the filter layer 11 to form a scour prevention structure 10, a step of connecting the tower section 53 to the monopile foundation 51, and a step of laying a power transmission cable 55 from the wind turbine section to the power receiving equipment installed on land.

[0026] The following describes the scour prevention structure 10. The scour prevention structure 10 is installed around a monopile foundation 51 on the seabed. The scour prevention structure 10 comprises a filter layer 11 installed around the monopile foundation 51 on the seabed, and a bagged root protection layer 12 made up of a plurality of bagged root protection materials 4 stacked on the filter layer 11.

[0027] The filter layer 11 is composed of crushed stone 8 spread over the seabed. The filter layer 11 is formed in an area slightly smaller than the area of ​​the bagged root protection layer 12 placed above it in plan view. The crushed stone 8 is spread over the top surface of the filter layer 11 so as to make it as smooth as possible.

[0028] The bagged root protection layer 12 is composed of multiple bagged root protection materials 4. The bagged root protection materials 4 are a mass formed by integrating multiple stone materials into a bag-shaped body. The stone materials that make up the bagged root protection materials 4 have a weight of, for example, 30 to 300 kg per piece. The bag body that makes up the bagged root protection materials 4 has enough strength to withstand external forces such as tensile force due to the weight of the stone materials inside when suspended by the floating crane 2. The bag body may also be a mesh-like bag body with a mesh size smaller than that of the stone materials that make up the bagged root protection materials 4.

[0029] In this embodiment, two sizes of bagged root protection materials 4 are used. When placed on flat ground, the bagged root protection materials 4 are a first bagged root protection material 41 with a small planar area, and a second bagged root protection material 42 with a planar area larger than that of the first bagged root protection material 41.

[0030] The arrangement of the bagged root fixation materials 4 in the bagged root fixation layer 12 will now be described. As shown in Figure 3, in plan view, multiple bagged root fixation materials 4 are arranged so as to overlap each other along the circumferential surface of the monopile foundation 51. In plan view, the bagged root fixation layer 12 also has multiple bagged root fixation materials 4 arranged so as to overlap each other on the radial outside of the monopile foundation 51.

[0031] First bagged root protection materials 41 are mainly arranged in the first annular portion 31, which is the innermost portion provided so as to contact the peripheral surface of the monopile foundation 51. Second bagged root protection materials 42 are arranged in place of the first bagged root protection materials 41 at locations (four locations) every 90° in plan view in the first annular portion 31. The first annular portion 31 is filled with bagged root protection materials 4 so as to form a substantially circular shape in plan view. Note that instead of the second bagged root protection materials 42 arranged in the first annular portion 31, a third bagged root protection material (not shown) having a larger planar area than the first bagged root protection materials 41 but a different planar area from the second bagged root protection materials 42 may be used.

[0032] The second annular portion 32, which is located on the outer periphery of the first annular portion 31, is configured with multiple overlapping second bagged root fixation materials 42, completely surrounding the first annular portion 31 in plan view. The second annular portion 32 is formed in a generally hexagonal shape in plan view. Between the first annular portion 31 and the second annular portion 32, where gaps are large in plan view, four second bagged root fixation materials 42A are provided to fill the gaps. From the third annular portion onward, which is located on the outer periphery of the second annular portion 32, multiple second bagged root fixation materials 42 are regularly arranged to be similar in shape to the second annular portion 32. Finally, the bagged root fixation materials 4 are laid out to a size that covers the filter layer 11 in plan view, forming the bagged root fixation layer 12.

[0033] As described above, by combining and arranging the first and second bagged root protection materials 41 and 42, the gap between the monopile foundation 51 and the bagged root protection layer 12 and the gap between adjacent bagged root protection materials 4, 4 can be minimized, thereby preventing scouring. The bagged root protection layer 12 shown in Figure 3 is the bottom layer. As shown in Figures 1 and 2, multiple bagged root protection materials 4 are laid on top of this layer to form a multi-layered bagged root protection layer 12. When constructing the upper layer of the bagged root protection layer 12, the first and second bagged root protection materials 41 and 42 may be combined as shown in Figure 3, or only the first or second bagged root protection materials 41 or 42 may be used.

[0034] Figure 4 shows a different arrangement pattern of the bagged root protection materials 4 from that shown in Figure 3. As shown in Figure 4, in plan view, multiple bagged root protection materials 4 are arranged so that they overlap each other along the circumferential surface of the monopile foundation 51. In plan view, the bagged root protection layer 12 also has multiple bagged root protection materials 4 arranged so that they overlap each other on the radial outside of the monopile foundation 51.

[0035] First bagged root protection materials 41 are primarily arranged in the first annular portion 31, which is the innermost portion and is provided in contact with the peripheral surface of the monopile foundation 51. Instead of the first bagged root protection materials 41, second bagged root protection materials 42 are arranged at eight locations (every 45° in a plan view) in the first annular portion 31. The first annular portion 31 is filled with bagged root protection materials 4 so that they form a substantially circular shape in a plan view. Instead of the second bagged root protection materials 42 arranged in the first annular portion 31, third bagged root protection materials (not shown) having a larger planar area than the first bagged root protection materials 41 but a different planar area from the second bagged root protection materials 42 may be used. In the configuration shown in FIG. 4, the first annular portion 31 has the first bagged root protection materials 41 and the second bagged root protection materials 42 arranged alternately in the circumferential direction.

[0036] The second annular portion 32, which is located on the outer periphery of the first annular portion 31, is configured with multiple overlapping second bagged root fixation materials 42, completely surrounding the first annular portion 31 in plan view. The second annular portion 32 is formed in a generally hexagonal shape in plan view. Between the first annular portion 31 and the second annular portion 32, where gaps are large in plan view, four second bagged root fixation materials 42A are provided to fill the gaps. From the third annular portion onward, which is located on the outer periphery of the second annular portion 32, multiple second bagged root fixation materials 42 are regularly arranged to be similar in shape to the second annular portion 32. Finally, the bagged root fixation materials 4 are laid out to a size that covers the filter layer 11 in plan view, forming the bagged root fixation layer 12.

[0037] As described above, by combining and arranging the first and second bagged root protection materials 41 and 42, the gap between the monopile foundation 51 and the bagged root protection layer 12 and the gap between adjacent bagged root protection materials 4, 4 can be minimized, thereby preventing scouring. The bagged root protection layer 12 shown in Figure 4 is the bottom layer. As shown in Figures 1 and 2, multiple bagged root protection materials 4 are laid on top of this layer to form a multi-layered bagged root protection layer 12. When constructing the upper layer of the bagged root protection layer 12, the first and second bagged root protection materials 41 and 42 may be combined as shown in Figure 4, or only the first or second bagged root protection materials 41 or 42 may be used.

[0038] 5 and 6, a method (one example) of constructing the scour prevention structure 10 according to this embodiment will be described. The construction unit 1 of the scour prevention structure 10 comprises a work vessel 3 equipped with a floating crane 2. The floating crane 2 comprises a boom 20 that can move freely in any direction. The boom 20 extends from a fixed part 20a on the floating crane 2 and is equipped with a first hook 21 and a second hook 22 at its end 20b. The first hook 21 is positioned closer to the fixed part 20a than the second hook 22. A first wire 23 is suspended from the first hook 21, and a second wire 24 is suspended from the second hook 22. The first wire 23 and the second wire 24 are each equipped with adjustable suspension lengths. A lower-stage suspension beam 25 is suspended from the tip of the first wire 23, and an upper-stage suspension beam 26 is suspended from the tip of the second wire 24. The upper-stage suspension beam 26 is provided vertically above the lower-stage suspension beam 25. The lower hoisting beam 25 is provided on its underside with a lower rope 27 (hereinafter referred to as the "third hook 27") for suspending bagged root protection material (scour prevention material) 4. The work vessel 3 is a known crane vessel equipped with a floating crane 2.

[0039] The water crane 2 is equipped with a control unit 28 having a first control unit 28a that controls the movement of the boom 20, a second control unit 28b that adjusts the suspension length of the first wire 23 and the second wire 24, and a third control unit 28c that controls the drive of the third hook 27.

[0040] The boom 20 is provided with a telescopic mechanism that is telescopic in the direction extending from the fixed part 20a, a height adjustment mechanism that adjusts the height of the boom 20, and a rotation mechanism that is capable of rotating the boom 20 around the fixed part 20a, and is provided so that it can move freely while ensuring the stability of the floating work vessel 3. The boom 20 may omit some of the movement mechanisms as long as it is possible to move the suspended bagged root protection material 4 to the desired position using the movement of the work vessel 3 and the movement mechanisms provided on the boom 20. For example, the telescopic mechanism may be omitted, and the boom 20 may be configured with the height adjustment mechanism and the rotation mechanism.

[0041] The first hook 21 is provided so as to be rotatable about a connection part 21a between the first hook 21 and the boom 20, and is provided so as to be able to be freely hooked and unhooked a first wire 23. The second hook 22 is provided so as to be rotatable about a connection part 22a between the second hook 22 and the boom 20, similar to the first hook 21, and is provided so as to be able to be freely hooked and unhooked a second wire 24.

[0042] As shown in Figure 6, the lower hoisting beam 25 and the upper hoisting beam 26 are each formed in a rectangular plate-like shape in a plan view. Furthermore, the lower hoisting beam 25 and the upper hoisting beam 26 are formed so that their width in one direction is larger than the width perpendicular to the overhang direction of the overhanging scaffolding 52. In this embodiment, the left-right direction in Figure 5 is the overhang direction of the overhanging scaffolding 52, and the left-right widths W1 and W2 of the lower hoisting beam 25 and the upper hoisting beam 26 in Figure 6 are formed larger than the width W3 of the overhanging scaffolding 52. Furthermore, since the lower hoisting beam 25 is provided vertically downward and the bagged root protection material 4 is suspended via the third hook 27, the width W2 is formed larger than the width W1 of the upper hoisting beam 26, and the member thickness is also formed larger than that of the upper hoisting beam 26.

[0043] The second wires 24 are attached by extending from the second hooks 22 toward both ends 26a, 26a in a plan view of the upper surface of the upper hoisting beam 26. Furthermore, the first wires 23 are attached by extending from the first hooks 21 toward both ends 26a, 26a in a plan view, and are lowered vertically downward from the upper hoisting beam 26 to be attached to both ends 25a, 25a in a plan view of the upper surface of the lower hoisting beam 25. By being suspended in the above configuration, the lower hoisting beam 25 and the upper hoisting beam 26 are suspended in a stable state with almost no rotational moment being generated.

[0044] A plurality of third hooks 27 are provided on the vertical lower surface of the lower hoisting beam 25, and a bagged root protection material 4 is hung from each of the plurality of third hooks 27. The plurality of third hooks 27 are provided at equal intervals on the lower surface of the lower hoisting beam 25.

[0045] The hanging length of the first wire 23 and the second wire 24 can be adjusted independently. This makes it possible to lower the lower hoisting beam 25 while maintaining the position of the upper hoisting beam 26. Furthermore, the first wire 23 and the second wire 24 have sufficient tensile strength to withstand being broken when hoisted at the installation location of the bagged root protection material 4. The lower hoisting beam 25 and the upper hoisting beam 26 have sufficient bending strength to withstand being broken when hoisted at the installation location of the bagged root protection material 4.

[0046] The first control unit 28a, the second control unit 28b, and the third control unit 28c each have a mechanism for remotely driving the controlled objects. In this embodiment, the first control unit 28a is provided on the work vessel 3 with an operating device for extending and retracting the boom 20, adjusting the height of the boom 20, and rotating the boom 20 around the fixed part 20a. The second control unit 28b is provided with a rotation mechanism for remotely rotating the first hook 21 and the second hook 22 to adjust the lengths of the first wire 23 and the second wire 24, and an operating device for the rotation mechanism is provided on the work vessel 3. The third control unit 28c is provided on the work vessel 3 with an operating device for remotely attaching and detaching the bagged root protection material 4 using the third hook 27.

[0047] In this embodiment, crushed stone 8 made of known stone or the like is layered on the seabed periphery 6 to form the filter layer 11. The stone used for the crushed stone 8 has a particle size of, for example, 80 mm or less. A plurality of bagged root protection materials 4, consisting of first bagged root protection materials 41 and second bagged root protection materials 42, are arranged and layered in predetermined positions on the filter layer 11 to form the bagged root protection layer 12, thereby forming a scour prevention structure 10 consisting of the filter layer 11 and the bagged root protection layer 12.

[0048] In this embodiment, the work vessel 3 is also equipped with a discharge section (not shown) that discharges and layers the crushed stone 8 onto the seabed periphery 6. The discharge section is constructed of a known tremie pipe. Note that, as long as the desired filter layer 11 can be formed, the discharge section that layers the crushed stone 8 may be provided on a vessel other than the work vessel 3, and the filter layer 11 may be formed in advance by that vessel before the formation of the bagged root protection material layer 12.

[0049] The scour prevention structure 10 has an external shape that is hollow hexagonal (circular) in plan view and trapezoidal in front view, surrounding the monopile foundation 51. However, the scour prevention structure 10 is not limited to the above-mentioned form as long as it has the desired performance. For example, it may be formed with an external shape that is hollow rectangular in plan view, or rectangular in front view.

[0050] The scour prevention structure 10 of this embodiment is a scour prevention structure 10 provided on the seabed peripheral edge 6 of an underwater monopile foundation 51, and comprises a first bagged root fixation material 41 arranged along the periphery of the monopile foundation 51, and a second bagged root fixation material 42 arranged around the first bagged root fixation material 41 so as to completely surround the first bagged root fixation material 41 in a planar view, and the second bagged root fixation material 42 has a larger planar area than the first bagged root fixation material 41 in a planar view, and the second bagged root fixation material 42, which has a larger planar area than the first bagged root fixation material 41, is arranged in place of the first bagged root fixation material 41 at predetermined angles around the monopile foundation 51 in a planar view. With this configuration, the gaps formed between the first bagged root protection material 41 and the second bagged root protection material 42 can be reduced or eliminated by using the second bagged root protection material 42, which has a larger planar area than the first bagged root protection material 41 and is arranged at a predetermined angle around the monopile foundation 51. This makes it possible to effectively prevent scouring around the underwater monopile foundation 51. Furthermore, the desired scour prevention structure 10 can be constructed using two types of bagged root protection materials 4, the first bagged root protection material 41 and the second bagged root protection material 42, thereby improving construction efficiency.

[0051] Furthermore, in the scour prevention structure 10, if the specified angle is 90°, the desired scour prevention structure 10 can be constructed simply by placing the second bagged root protection material 42 instead of the first bagged root protection material 41 at four locations around the monopile foundation 51 at 90° intervals, thereby improving construction efficiency.

[0052] Furthermore, in the scouring prevention structure 10, if the specified angle is 45°, the desired scouring prevention structure 10 can be constructed by simply placing the second bagged root fixation material 42 instead of the first bagged root fixation material 41 at eight locations every 45° around the monopile foundation 51, making it possible to reduce the gap when viewed in a plane.

[0053] In addition, in the scouring prevention structure 10, by stacking and laying the second bagged root protection material 42 on the upper layer on which the first bagged root protection material 41 and the second bagged root protection material 42 are arranged, it is possible to construct a scouring prevention structure 10 with a two-layer structure, and scouring around the monopile foundation 51 can be more effectively prevented.

[0054] Although the embodiment of the scour prevention structure according to the present invention has been described above, the present invention is not limited to the above embodiment and can be modified as appropriate within the scope of the invention.

[0055] For example, the scour prevention structure 10 has been described as having a two-layer structure in the vertical direction, but it may also have a multi-layer structure having three or more layers.

[0056] The scour prevention structure 10 has been described as having the second bagged root protection materials 42 arranged every 45° or 90° of the first annular portion 31, but the predetermined angle is not limited to this, and the second bagged root protection materials 42 may be arranged, for example, every 60°. Also, as mentioned above, a third bagged root protection material may be arranged in place of the second bagged root protection materials 42 arranged in the first annular portion 31.

[0057] The scouring prevention structure 10 has been described as having a second bagged root fixation material 42A placed to fill the gap between the first annular portion 31 and the second annular portion 32, but instead of the second bagged root fixation material 42A, bagged root fixation materials 4 of other shapes and sizes, such as the first bagged root fixation material 41 or the third bagged root fixation material, may also be placed.

[0058] The scour prevention structure 10 has been described as being composed of a filter layer 11 and a bagged root protection layer 12, but the bagged root protection layer 12 may also be formed directly on the seabed edge 6 without providing a filter layer 11.

[0059] It should be noted that the offshore structure to which the present invention is applied is not limited to the monopile structure 5 of this embodiment, as long as it is possible to install a scour prevention section around the bottom edge of the offshore structure equipped with overhanging scaffolding. For example, it may be a bridge pier or the like.

[0060] The Sustainable Development Goals (SDGs) are 17 international goals that were adopted at the United Nations Summit in September 2015. The welding device according to this embodiment can contribute to achieving one of the 17 SDGs, for example, goal 7, "Affordable and clean energy." [Explanation of symbols]

[0061] 4. Bag-packed root protection material 10 Anti-scouring structure 41 First bagged root protection material 42 Second bagged root protection material (third bagged root protection material) 51 Monopile foundation (foundation)

Claims

1. A scour prevention structure provided around an underwater foundation, A first bagged root protection material arranged along the periphery of the foundation; A second bagged root fixation material is arranged around the first bagged root fixation material so as to completely surround the first bagged root fixation material in a plan view, The second bagged root protection material has a planar area larger than the planar area of ​​the first bagged root protection material in a plan view, A scour prevention structure in which third bagged root fixation materials having a larger planar area than the first bagged root fixation materials are arranged in place of the first bagged root fixation materials at predetermined angles around the foundation when viewed in a plane.

2. The scour prevention structure according to claim 1, wherein the third bagged root protection material is the same size as the second bagged root protection material.

3. The scour prevention structure according to claim 1 , wherein the predetermined angle is 90°.

4. The scour prevention structure according to claim 1 , wherein the predetermined angle is 45°.

5. The scour prevention structure described in claim 1, wherein the second bagged root protection material is layered and laid on top of the first bagged root protection material, the second bagged root protection material, and the third bagged root protection material.

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