Method and unit for preventing scour of underwater structure

Abstract

To provide a scouring prevention construction method of an underwater structure capable of easily constructing a scouring prevention structure without requiring diving work, by effectively restraining initial scouring caused by installation of a bagged unit.SOLUTION: A scouring prevention method for an underwater structure includes an installation step of installing a scouring prevention unit A on a water bottom surface C around an underwater structure B, wherein the scouring prevention unit A includes a laying surface material, a plurality of bagging units arranged on the laying surface material, and a filling unit arranged in a gap between the plurality of adjacent bagging units or above the plurality of adjacent bagging units. A disassembling bag body of the filling unit is made of a material and / or a structure having a faster disassembling speed than that of the bag body of the bagging unit, and a gap between the underwater structure B and the bagging unit and / or gaps between a plurality of adjacent bagging units are filled with the filling material by the disassembly of the disassembling bag body to construct a scour prevention structure A. The scouring prevention unit is provided with a laying surface material, a plurality of bagging units whose bottom surfaces are connected to the laying surface material, and a filling unit arranged in a clearance between the plurality of adjacent bagging units or in an upper part thereof.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a scour prevention method and scour prevention unit for underwater structures, and in particular to a scour prevention method and scour prevention unit for underwater structures that effectively suppresses initial scouring associated with the installation of bagging units and allows for the easy construction of a scour prevention structure without the need for diving work. [Background technology]

[0002] In underwater structures such as the supports of monopile-type offshore wind power plants and the mounds of breakwaters, a filter layer made of rubble is installed to prevent scouring of the foundations and embedded parts. The crushed stone that makes up the filter layer must be small in size to prevent suction, but it also needs to have a certain weight to prevent movement due to external forces such as waves. To meet these conflicting requirements, a bagging unit is used, in which crushed stone is packed inside a mesh bag. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-195764 Summary of the Invention [Problem to be solved by the invention]

[0004] Because the bagging unit has a flat, dumpling-like shape, even when it is installed close to an underwater structure, a roughly triangular gap will form between the base of the underwater structure and the bottom of the bagging unit in side view (Figure 9).Gaps will also form between adjacent bagging units. As a result, immediately after the bagging unit is installed, vortices are generated in the gaps between the underwater structure and the bagging unit, causing "initial scouring" in which sand from the bottom of the water is sucked out. To prevent initial scouring, immediately after installing the bagging units, crushed stone must be packed into the gaps between the bagging units to cover the bottom surface. The filling of the gaps between the crushed stones is done manually by divers, but the work is easily affected by weather and sea conditions, and there are legal limits on the amount of time the divers can spend underwater, so the work efficiency is very low. For this reason, it takes a very long time to fill the gap, especially for monopiles located in deep water, and suction continues during this time, making it difficult to effectively prevent initial scouring.

[0005] An object of the present invention is to provide a scour prevention method and scour prevention unit for underwater structures that can solve the above-mentioned problems. [Means for solving the problem]

[0006] The method for preventing scouring of underwater structures of the present invention comprises an installation step of installing a scouring prevention unit on the water bottom surface surrounding the underwater structure, the scouring prevention unit comprising a laying surface material, a plurality of bagging units arranged on the laying surface material, and a filler unit arranged in the gaps between adjacent bagging units or above them, the bagging units being formed by filling a filler material inside a bag body, the filler units being formed by filling a filler material inside a decomposable bag body, the decomposable bag body being made of a material and / or structure that decomposes faster than the bag body, and the gaps between the underwater structure and the bagging units, and / or the gaps between adjacent bagging units, are filled with the filler material by decomposition of the decomposable bag body, thereby constructing a scouring prevention structure.

[0007] The method for preventing scouring of underwater structures of the present invention comprises an arrangement step of arranging a plurality of bagging units, each having a bag body filled with filler material, on the water bottom surface surrounding the underwater structure, and a filling step of arranging a filler unit, each having a decomposition bag body filled with filler material, above the gap between the underwater structure and the bagging unit or above the gap between a plurality of adjacent bagging units, wherein the decomposition bag body is made of a material and / or structure that decomposes faster than the bag body, and the decomposition of the decomposition bag body fills the gap between the underwater structure and the bagging unit, and / or the gap between a plurality of adjacent bagging units, with the filler material, thereby constructing a scouring prevention structure.

[0008] In the scouring prevention construction method for underwater structures of the present invention, the installation process may comprise a ground assembly process of assembling the scouring prevention unit on land or on a ship, and a hanging process of hanging the scouring prevention unit onto the water bottom surface around the underwater structure.

[0009] In the scouring prevention method for underwater structures of the present invention, the bottoms of a plurality of bagging units may be connected to a laying surface material, and in the hanging step, the scouring prevention units may be hung by the plurality of bagging units.

[0010] In the method for preventing scouring of an underwater structure of the present invention, the degradable bag may be provided with a biodegradable net.

[0011] The scouring prevention unit of the present invention comprises a laying surface material, a plurality of bagging units whose bottom surfaces are connected to the laying surface material, and a filling unit arranged in the gaps between or above adjacent bagging units, wherein the bagging units are formed by filling a filling material inside a bag body, the filling units are formed by filling a filling material inside a decomposition bag body, and the decomposition bag body is made of a material and / or structure that decomposes faster than the bag body.

[0012] In the scour prevention unit of the present invention, the laying surface material may be a net material, a mesh sheet, or a waterproof sheet. [Effects of the Invention]

[0013] The method for preventing scouring of underwater structures of the present invention involves placing gap fillers in the gaps between the underwater structure and the bagging units, and in the gaps between the bagging units, simultaneously with or immediately after the installation of the bagging units, thereby utilizing the difference in the decomposition speed of the bags in the bagging units and the bagging units to autonomously fill the gaps and effectively prevent initial scouring.In addition, since diving work by divers is not required, the construction is safe and inexpensive. The scouring prevention unit for underwater structures of the present invention is formed by arranging bagging units and interfilling units on a laying surface material in advance to form a unit, so that by simply hanging it underwater and installing it around the underwater structure, a scouring prevention structure (filter layer) that can effectively prevent scouring of the underwater structure can be easily constructed. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is an explanatory diagram of a scour prevention unit according to the present invention; [Figure 2] Diagram of the bagging unit [Figure 3] Illustration of the hanging process (1) [Figure 4] Illustration of the hanging process (2) [Figure 5] Illustration of construction of scour prevention structure (1) [Figure 6] Illustration of construction of scour prevention structure (2) [Figure 7] Explanatory diagram of Example 2 (1) [Figure 8] Explanatory diagram of Example 2 (2) [Figure 9] Explanatory diagram of the prior art DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, the scour prevention method and scour prevention unit for underwater structures of the present invention will be described in detail with reference to the drawings. [Example]

[0016] [Scour prevention unit] <1> Overall configuration (Figure 1) The scour prevention unit 1 is equipment that is placed on the water bottom C around the underwater structure B to prevent scouring of the water bottom C. The scouring prevention unit 1 includes at least a plurality of bagging units 10, a plurality of filling units 20, and a laying surface material 30. In detail, it is configured as follows. A plurality of bagging units 10 are arranged adjacent to each other on the laying surface material 30. The bagging units 10 may be arranged in parallel, staggered, radial, or any other desired arrangement. Since the bagging units 10 have a generally circular shape in a plan view, gaps G are generated between adjacent bagging units 10 and between the underwater structure B and the bagging units 10. A plurality of filling units 20 are arranged in the gap G between the bagging units 10 and above or inside the gap G between the underwater structure B and the bagging units 10. The bottoms of the multiple bagging units 10 are connected to the top surface of the laying surface material 30.

[0017] <1.1>Underwater structures The underwater structure B that is the subject of the present invention is a structure that is installed on the water bottom C or penetrates into the ground from the water bottom C. In this example, the underwater structure B is a support pillar of a monopile-type offshore wind power generation facility. However, the underwater structure B is not limited to offshore wind power generation facilities, and can also be applied to breakwater mounds, bridge pier foundations, etc.

[0018] <2> Bagging unit (Figure 2) The bagging unit 10 is a unit that constitutes the filter layer of the scouring prevention unit 1. The bagging unit 10 includes at least a bag body 11 and a filler material 12 filled in the bag body 11. When placed on the water bottom C, the bagging unit 10 has a generally spherical shape that is flattened vertically. In this example, a bag material for root protection made of a bag-shaped knitted fabric is used as the bag body 11. In detail, the bottom net is formed by narrowing the bottom end of a cylindrical Russell knitted fabric made of polyester fiber, and the opening at the top end is formed as the bag mouth. However, the knitted fabric is not limited to this, and may be made of nylon, polyethylene, etc. A necking rope 13 for tightening and closing the bag mouth is passed through the bag mouth of the bag body 11. In this example, crushed stone having a diameter of about 150 mm is used as the filler material 12. However, the present invention is not limited to this, and boulders, other natural aggregates, concrete rubble, etc. of any suitable diameter can be used.

[0019] <3> Filling unit The filling unit 20 is a component that fills the gap G of the scouring prevention unit 1. The filling unit 20 includes at least a decomposition bag 21 and a filler 22 filled in the decomposition bag 21. When installed on flat ground, the filling unit 20 has a generally spherical outer shape that is flattened vertically. In this example, crushed stone of the same diameter as the filler material 12 is used as the filler material 22. However, this is not limiting, and crushed stone of a larger or smaller diameter than the filler material 12 may also be used. Also, the filler material 22 may be made of a material different from the filler material 12.

[0020] <3.1> Decomposition bag The decomposable bag body 21 is a bag material that accommodates the filler material 22. The decomposing bag 21 is made of a material and / or structure that decomposes faster in the sea than the bag 11 of the bagging unit 10. In this example, a bag material made of a knitted biodegradable mesh is used as the degradable bag body 21. The biodegradable material is, for example, paper or biodegradable plastic. The decomposable bag 21 is not limited to being made of a material different from that of the bag 11, and may be made of the same material but with a thinner knitted fabric or with slits in the knitted fabric to increase the decomposition speed.

[0021] <4> Laying surface material The laid surface material 30 is a surface material that forms the bottom surface of the scour prevention unit 1. In this example, a polyester fiber net material is used as the laying surface material 30. However, the laying surface material 30 is not limited to this, and any other suitable material may be used, such as a polyurethane fiber net material, mesh sheet, waterproof sheet, nonwoven fabric or multi-layered fabric, as long as it has the flexibility to follow the undulations of the water bottom surface C and a predetermined tensile strength.

[0022] [Scour prevention method] <1> Overall structure The scour prevention method for underwater structures is a method in which the water bottom C around the underwater structure B is covered with a scour prevention structure A. The scouring prevention structure A is a filter layer formed by filling the gaps G between a plurality of bagging units 10 with filler material 22. Here, the bagging units 10 may be in a state where the bag bodies 11 have been disassembled and only the filler material 12 remains. The method for preventing scouring of an underwater structure includes at least an installation step S1. One of the features of the method for preventing scouring of underwater structures is that it is configured to prevent initial scouring of the water bottom surface C due to the installation of the bagging unit 10 by decomposing the decomposable bag body 21 of the filling unit 20 and filling the internal filling material 22 into the gap G of the bagging unit 10.

[0023] <2> Installation process The installation process S1 is a process of installing the scour prevention unit 1 on the water bottom surface C around the underwater structure B. Here, "around the underwater structure" is not limited to the area close to the underwater structure B, but can broadly include the area around the underwater structure B that is at risk of scouring due to tidal currents. In this example, the installation process S1 is made up of a base assembly process S11 and a hanging process S12.

[0024] <2.1> Base assembly process (Fig. 1) The on-site assembly step S11 is a step of assembling the scour prevention unit 1. The on-site assembly step S11 is carried out on land or on a ship. A plurality of bagging units 10 are arranged on top of the laying surface material 30 spread out on the installation surface. The arrangement and spacing of the bagging units 10 correspond to the design of the scour prevention structure A to be constructed on the water bottom surface C. A rope is passed through the mesh of the bag body 11 at the bottom of the bagging unit 10 and the mesh of the laying surface material 30, connecting the bagging unit 10 to the laying surface material 30. A plurality of filling units 20 are placed in the gaps G between adjacent bagging units 10. In this case, the filling units 20 may be placed on top of the gaps G, or may be filled between the gaps G. Furthermore, for a bagging unit 10 that is adjacent to an underwater structure B after installation on the water bottom surface C, a filling unit 20 is placed on the top near the underwater structure B.

[0025] <2.2> Hanging process (Fig. 3, 4) The hanging step S12 is a step of hanging the scour prevention unit 1 onto the water bottom C around the underwater structure B. The scour prevention unit 1 assembled on the ground is loaded onto a large crane ship and transported to the installation location of the underwater structure B. Near the underwater structure B, the ship-mounted scour prevention unit 1 is hoisted into the water using a hoisting device D or the like and placed on the water bottom C. In this example, the bottom of the bagging unit 10 is connected to the laying surface material 30, so by engaging the hook of the hanging tool D with the hanging rope of the bagging unit 10, the entire scouring prevention unit 1 can be stably hung via the bagging unit 10. In addition, because no hanging load is placed on the filling unit 20, there is no risk of damaging the decomposable bag body 21 before installation.

[0026] <3> Construction of scour prevention structures (Figures 5 and 6) After the installation of the scouring prevention unit 1, when a predetermined time has elapsed, the decomposition bag body 21 of the filling unit 20 decomposes, and the filling material 22 filled in the decomposition bag body 21 spills out. Since the filling unit 20 is installed in advance above the gap G between the underwater structure B and the bagging unit 10, the spilled filling material 22 self-fills into the gap G, so that the filling material 22 covers the root portion of the underwater structure B without any gaps, and a scouring prevention structure A consisting of the bagging unit 10 and the filling material 22 is constructed. As time passes, the bag body 11 of the bagging unit 10 decomposes, and the filling material 12 inside engages with the filler material 22 to form a filter layer of a predetermined thickness. The anti-scouring method for underwater structures of the present invention combines two types of bags with different decomposition rates, making it possible to autonomously construct a filter layer of a predetermined thickness while preventing initial scouring of the water bottom surface C due to construction time differences. [Example]

[0027] [Example of no installation surface material] The method for preventing scouring of underwater structures of the present invention can also be carried out without using the laying surface material 30. In this example, the bagging unit 10 and the filling unit 20 are handled separately. Near the underwater structure B, the bagging units 10 are suspended underwater using a hoisting tool D or the like and placed on the water bottom C (placement process S2: Figure 7). It is desirable to connect the bagging units 10 to the hoisting tool D in advance while arranging them at a predetermined interval. The filling unit 20 is hung using a hanging device D into the gap G between the underwater structure B and the bagging unit 10 installed on the water bottom C, and into the gap G between adjacent bagging units 10 (filling process S3: Figure 8). [Explanation of symbols]

[0028] 1 Scour prevention unit 10 bagging units 11 Bag body 12 Filling material 13 Mouth-squeezing rope 20 Filling Unit 21 Decomposition bag 22 Filling material 30 Laying surface material A Scour prevention structure B Underwater structures C Underwater surface D. Lifting equipment S1 Installation process S11 Ground assembly process S12 Hanging process S2 placement process S3 Filling process G Gap

Claims

1. A scour prevention method for an underwater structure, in which the bottom surface of the water surrounding the underwater structure is covered with a scour prevention structure of a predetermined thickness, An installation step of installing a scour prevention unit on the bottom surface of the water around the underwater structure, The scouring prevention unit comprises a laying surface material, a plurality of bagging units arranged on the laying surface material, and a filling unit arranged in the gaps between the plurality of adjacent bagging units or above them, The bag filling unit fills the inside of the bag with a filling material, The filling unit is formed by filling a filling material inside a decomposition bag body, The decomposition bag is made of a material and / or structure that decomposes faster than the bag itself, By decomposing the decomposable bag body, the gap between the underwater structure and the bagging unit and / or the gap between the adjacent bagging units is filled with the filler material to construct the scouring prevention structure. A method for preventing scouring of underwater structures.

2. A scour prevention method for an underwater structure, in which the water bottom surface around the underwater structure is covered with a scour prevention structure of a predetermined thickness, an arrangement step of arranging a plurality of bagging units, each having a bag body filled with a filler material, on the bottom surface of the water around the underwater structure; A filling step is included in which a filling unit having a filling material filled inside a decomposition bag is placed above the gap between the underwater structure and the bagging unit or above the gaps between the adjacent bagging units, The decomposition bag is made of a material and / or structure that decomposes faster than the bag itself, By decomposing the decomposable bag body, the gap between the underwater structure and the bagging unit and / or the gap between the adjacent bagging units is filled with the filler material to construct the scouring prevention structure. A method for preventing scouring of underwater structures.

3. The installing step includes: a ground assembly process of assembling the scour prevention unit on land or on a ship; and a hanging step of hanging the scour prevention unit on the water bottom surface around the underwater structure. The method for preventing scouring of an underwater structure according to claim 1.

4. The bottoms of the plurality of bagging units are connected to the laying surface material, In the hanging step, the scouring prevention unit is hung by a plurality of the bagging units. The method for preventing scouring of an underwater structure according to claim 3.

5. The degradable bag is characterized in that it comprises a biodegradable net. The method for preventing scouring of an underwater structure according to any one of claims 1 to 4.

6. A scour prevention unit to be placed on the bottom surface of the water around the underwater structure, A laying surface material; A plurality of bagging units each having a bottom surface connected to the laying surface material; A filling unit is provided, the filling unit being arranged in the gap between the adjacent plurality of bagging units or above the gap, The bag filling unit fills the inside of the bag with a filling material, The filling unit is formed by filling a filling material inside a decomposition bag body, The decomposition bag is made of a material and / or structure that decomposes faster than the bag itself. Scour prevention unit.

7. The laying surface material is a net material, a mesh sheet, or a waterproof sheet, The scour prevention unit according to claim 6.

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