Construction unit of soil erosion prevention work and construction method of soil erosion prevention work

Abstract

To provide a unit and a method for constructing a scour protection, which can install a scour protection material directly below or near an overhanging scaffold of a monopile type structure.SOLUTION: A construction method uses a unit 1 is for constructing a scour protection, which is provided with a work ship 3 in which a water crane 2 is disposed. The water crane 2 includes a lower suspension beam 25 suspended by a first wire 23, disposed below an overhanging scaffold 51 in a vertical direction, and provided with a lower cord 27 for suspending a scour protection material 4, and an upper suspension beam 26 suspended by a second wire 24 and disposed above the overhanging scaffold 51 in the vertical direction. The lower suspension beam 25 and the upper suspension beam 26 are formed to have larger widths in at least one direction than those in a direction orthogonal to the overhanging direction of the overhanging scaffold 51. A scout protection part is formed at a water bottom peripheral edge 6 of a monopile type structure 5. The lower suspension beam 25 is lowered in a state where the position of the upper suspension beam 26 is maintained, and the scour protection material 4 is installed at the water bottom peripheral edge 6.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a construction unit for scour protection work and a construction method for scour protection work.

Background Art

[0002] Offshore wind power is a renewable energy with low carbon dioxide emissions. It has characteristics such as stronger winds than on land, less turbulence in wind speed, and greater stability, so its introduction into the power generation business has been promoted. In many cases, the foundation type of offshore wind power equipment adopts the monopile (single pile) type. Generally, since the foundation diameter of the monopile type is large, scour protection work is carried out to prevent scour around the foundation caused by waves and tides. As scour protection work, for example, a method of directly laying riprap as a scour protection material on the outer periphery of the foundation by a tremie ship, a method of strengthening the soil around the foundation by the frictional force between the rockfill material arranged on the seabed around the outer periphery of the foundation and the soil around the foundation (see, for example, Patent Document 1), a method of laying an impermeable covering on the outer periphery of the foundation and filling stones and crushed stones at the joints of the mat (see, for example, Patent Document 2), etc.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the one hand, different from other regions such as Europe, Japan also needs to consider the impact of tsunamis. The seabed surface velocity of a tsunami is much larger than that of waves and tidal currents, and the required riprap weight can sometimes exceed 10 t. As a scour prevention work considering the impact of tsunamis, there is a construction method in which a bagged root reinforcement material formed by integrating a plurality of stones is installed on the outer periphery of the foundation using an offshore crane, instead of using conventional riprap (30 - 300 kg) as the scour prevention material.

[0005] However, a cantilever scaffold is provided on the upper part of the foundation of the offshore wind power facility for maintenance and management work of the facility, temporary placement of machinery and equipment, etc. Immediately below or near the cantilever scaffold, there is a problem that it is difficult to install the bagged root reinforcement material using an offshore crane because the offshore wind power facility may be damaged when the boom, wire of the offshore crane, or the suspended bagged root reinforcement material contacts the foundation or the cantilever scaffold.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a construction unit for scour prevention work and a construction method for scour prevention work that can easily install a scour prevention material immediately below or near the cantilever scaffold of a monopile-type structure.

Means for Solving the Problem

[0007] To achieve the above object, a construction unit for scour prevention work according to the present invention is a construction unit for scour prevention work that forms a scour prevention portion on the peripheral edge of the water bottom of a monopile-type structure provided with a cantilever scaffold, and includes a work ship on which an offshore crane for installing a scour prevention material to form the scour prevention portion is arranged. The offshore crane is suspended by a first wire suspended from a first hook provided at the end of a boom that can move freely in all directions, and is arranged vertically below the cantilever scaffold. It includes a lower suspension beam provided with a lower cable for suspending the scour prevention material, and an upper suspension beam suspended by a second wire suspended from a second hook provided at the end of the boom and arranged vertically above the cantilever scaffold. The lower suspension beam and the upper suspension beam are formed such that the width length in at least one direction is larger than the width length orthogonal to the protruding direction of the cantilever scaffold.

[0008] With the above configuration, the cantilever scaffold is arranged between the upper suspension beam and the lower suspension beam. Therefore, the construction unit of the scour prevention work can easily and safely place the scour prevention material suspended by the operation of the floating crane on the installation point of the scour prevention material directly below or near the cantilever scaffold without being affected by the cantilever scaffold.

[0009] Also, in the construction unit of the scour prevention work according to the present invention, the first wire may be attached to one end of the lower suspension beam, and the second wire may be attached to one end of the upper suspension beam.

[0010] With the above configuration, the upper suspension beam and the lower suspension beam can maintain a more stable state when suspending the scour prevention material (it is easy to maintain the moment balance with the scour prevention material). Therefore, the safety of the installation work of the scour prevention material can be further improved. Also, since the upper suspension beam and the lower suspension beam are suspended in a stable state, it is possible to more easily prevent contact between the components of the floating crane such as the wire and the suspension beam and the scour prevention material and the monopile-type structure.

[0011] Also, to achieve the above object, the construction method of the scour prevention work according to the present invention is a construction method of the scour prevention work using the construction unit of the scour prevention work according to the present invention, in which the first wire is extended vertically downward while maintaining the position of the upper suspension beam to lower the lower suspension beam, and the scour prevention material is installed at the periphery of the water bottom.

[0012] With the above configuration, the scour prevention material can be easily installed directly below or near the cantilever scaffold of the monopile-type structure. Also, the construction unit of the scour prevention work can prevent contact between the components of the floating crane such as the wire and the suspension beam and the scour prevention material and the monopile-type structure and damage to the monopile-type structure during the installation work of the scour prevention material, and it is possible to perform a safe installation work.

[0013] Further, in the construction method of the erosion prevention work according to the present invention, the erosion prevention material may be provided as a bagged root fixing material of a massive body in which a plurality of stones are integrated, and the bagged root fixing material may be laminated on the periphery of the water bottom to form the erosion prevention part.

[0014] With the above configuration, the erosion prevention part can increase the weight of each erosion prevention material, and it is also possible to prevent the erosion of the periphery of the water bottom of the monopile type structure by a tsunami or the like in which the flow velocity of the sea bottom surface is larger than that of waves and tidal currents.

[0015] Further, in the construction method of the erosion prevention work according to the present invention, stones may be arranged on the periphery of the water bottom to form a filter layer, and a bagged root fixing material of a massive body in which a plurality of stones are integrated may be laminated on the filter layer to form a bagged root fixing material layer, and the erosion prevention part including the filter layer and the bagged root fixing material layer may be formed.

[0016] With the above configuration, the erosion prevention part can prevent the erosion of the periphery of the water bottom of the monopile type structure from occurring from the gap of the bagged root fixing material constituting the bagged root fixing material layer by the filter layer provided on the periphery of the water bottom.

[0017] Further, in the construction method of the erosion prevention work according to the present invention, a plurality of lower cables are provided below the lower suspension beam, and each of the plurality of lower cables can suspend the bagged root fixing material, and the plurality of bagged root fixing materials may be installed simultaneously.

[0018] With the above configuration, since a plurality of bagged root fixing materials can be installed by a single installation work, it is possible to reduce the labor and time for the construction of the erosion prevention work.

Effect of the Invention

[0019] According to the present invention, it is possible to provide a construction unit for erosion prevention work and a construction method for erosion prevention work that can easily install an erosion prevention material directly below or near the cantilever scaffold of a monopile type structure.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0021] Hereinafter, the construction method of the erosion prevention work according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5. In this embodiment, the case of constructing the erosion prevention work on the seabed at the periphery of the foundation of a monopile-type offshore wind power generation device (offshore wind turbine) installed on the sea will be described.

[0022] As shown in FIGS. 1 and 2, the construction unit 1 for anti-scouring work according to this embodiment (hereinafter referred to as "construction unit 1") includes a work ship 3 equipped with an offshore crane 2. The offshore crane 2 is provided with a boom 20 that can move freely in all directions. The boom 20 extends from a fixed part 20a on the offshore crane 2 and is provided with a first hook 21 and a second hook 22 at its end 20b. The first hook 21 is located closer to the fixed part 20a side 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 provided with an adjustable suspension length. The first wire 23 suspends a lower suspended beam 25 at its tip, and the second wire 24 suspends an upper suspended beam 26 at its tip. The upper suspended beam 26 is provided above the lower suspended beam 25 in the vertical direction. The lower suspended beam 25 is provided with a lower cable 27 (hereinafter referred to as "third hook 27") for suspending the anti-scouring material 4 on its lower surface. The work ship 3 is a known crane ship equipped with an offshore crane 2.

[0023] The monopile type structure 5 to which the construction unit 1 is applied includes a cantilever scaffold 51 on a monopile type foundation 52 which is a base part. The construction unit 1 installs and stacks the anti-scouring material 4 at the bottom of the sea directly below and near the cantilever scaffold 51 (hereinafter referred to as "sea bottom periphery 6") to form an anti-scouring part 7. The anti-scouring material 4 is provided as a mass bagged root consolidating material 41 in which a plurality of stones are put into a bag-shaped body and integrated. The stones constituting the bagged root consolidating material 41 have a weight of, for example, 30 to 300 kg per piece. The bag-shaped body constituting the bagged root consolidating material 41 has a strength that is not damaged by external forces such as tensile force due to the weight of the internal stones when suspended by the offshore crane 2. Further, the bag-shaped body is provided as a net-shaped bag-shaped body having a smaller mesh size than, for example, the stones constituting the bagged root consolidating material 41.

[0024] Furthermore, the offshore crane 2 includes a main body part 28 having a first control part 28a for controlling the movement of the boom 20, a second control part 28b for adjusting the suspension lengths of the first wire 23 and the second wire 24, and a third control part 28c for controlling the drive of the third hook 27.

[0025] The boom 20 is provided with a telescopic mechanism that can be telescopically extended 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 allows the boom 20 to rotate around the fixed part 20a, and is movably provided while ensuring the stability of the work ship 3 which is a floating body. If the boom 20 can move the bag stuffing and fixing material 41 suspended by the movement of the work ship 3 and each movement mechanism provided on the boom 20 to a desired position, a part of the movement mechanism may be omitted. For example, there is a configuration in which the telescopic mechanism is omitted and the boom 20 is provided with the height adjustment mechanism and the rotation mechanism.

[0026] The first hook 21 is rotatably provided around the connection part 21a between the first hook 21 and the boom 20, and is provided with a first wire 23 that can be disengaged. The second hook 22 is rotatably provided around the connection part 22a between the second hook 22 and the boom 20 in the same manner as the first hook 21, and is provided with a second wire 24 that can be disengaged.

[0027] As shown in FIG. 2, the lower suspension beam 25 and the upper suspension beam 26 are each formed in a plate shape that is rectangular in plan view. Also, the lower suspension beam 25 and the upper suspension beam 26 are formed such that the width length in one direction is larger than the width length orthogonal to the protruding direction of the protruding scaffold 51. In the present embodiment, the left - right direction in FIGS. 1 and 3 is the protruding direction of the protruding scaffold 51, and the left - right width lengths W1 and W2 of the lower suspension beam 25 and the upper suspension beam 26 in FIGS. 2 and 4 are formed larger than the width length W3 of the protruding scaffold 51. Further, since the lower suspension beam 25 is provided vertically downward and the bag stuffing and fixing material 41 is suspended via the third hook 27, the width length W2 is formed larger than the width length W1 of the upper suspension beam 26, and the member thickness is also formed larger than that of the upper suspension beam 26.

[0028] The second wire 24 extends from the second hook 22 toward both end portions 26a, 26a in plan view on the upper surface of the upper suspension beam 26 and is attached thereto. Also, the first wire 23 extends from the first hook 21 toward both end portions 26a, 26a in plan view and is attached, and is lowered vertically downward from the upper suspension beam 26 and attached to both end portions 25a, 25a in plan view of the upper surface of the lower suspension beam 25. The lower suspension beam 25 and the upper suspension beam 26 are suspended in the above-described configuration, and thus are suspended in a stable state with almost no rotational moment generated.

[0029] A plurality of third hooks 27 are provided on the vertically lower surface of the lower suspension beam 25, and a bag bottom fixing material 41 is suspended 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 suspension beam 25.

[0030] As shown in FIGS. 3 and 4, the first wire 23 and the second wire 24 can each independently adjust the suspension length. Therefore, it is possible to lower the lower suspension beam 25 while maintaining the position of the upper suspension beam 26. Also, the first wire 23 and the second wire 24 have a tensile strength that does not break when suspended to the installation location of the bag bottom fixing material 41. The lower suspension beam 25 and the upper suspension beam 26 have a bending strength that is not destroyed when suspended to the installation location of the bag bottom fixing material 41.

[0031] The first control unit 28a, the second control unit 28b, and the third control unit 28c each have a mechanism for remotely driving their respective control targets. In the present embodiment, the first control unit 28a includes an operating device that extends and retracts the boom 20 on the work ship 3, adjusts the height of the boom 20, and rotates the boom 20 about the fixed portion 20a. The second control unit 28b includes a rotating mechanism that remotely rotates the first hook 21 and the second hook 22 to adjust the lengths of the first wire 23 and the second wire 24, and includes an operating device for the rotating mechanism on the work ship 3. The third control unit 28c includes an operating device that remotely removes the bag bottom fixing material 41 by the third hook 27 on the work ship 3.

[0032] As shown in FIG. 5, in the present embodiment, a filter layer forming material 8 using a known stone or the like is laminated on the seabed periphery 6 to form a filter layer 81. The stone used for the filter layer forming material 8 has a particle size of 80 mm or less, for example. By laminating the bagging root fixing material 41 on the filter layer 81 to form a bagging root fixing material layer 42, a washing and excavation prevention part 7 composed of the filter layer 81 and the bagging root fixing material layer 42 is formed. The plurality of bagging root fixing materials 41 are formed with substantially the same weight.

[0033] In addition, in the present embodiment, the work ship 3 is provided with a discharge part (not shown) for discharging and laminating the filter layer forming material 8 on the seabed periphery 6. The discharge part is composed of a known tremie pipe. If a desired filter layer 81 can be formed, the discharge part for laminating the filter layer forming material 8 may be provided on a ship other than the work ship 3, and the filter layer 81 may be formed in advance by the ship before the formation of the bagging root fixing material layer 42.

[0034] The washing and excavation prevention part 7 has an outer shape that is a hollow circle in plan view and a trapezoid in front view surrounding the monopile foundation 52. Note that the form is not limited to the above as long as the washing and excavation prevention part 7 has a desired performance. For example, it may be formed in an outer shape that is a hollow rectangle in plan view or a rectangle in front view.

[0035] The monopile type structure 5 in the present embodiment is a monopile type offshore wind power generation device provided on the sea (hereinafter referred to as "monopile type offshore wind power generation device 5"). The monopile type offshore wind power generation device 5 includes a cantilever scaffold 51, a monopile type foundation 52, a power generation part 53, a mooring and lifting facility 54, and a power transmission cable 55.

[0036] The cantilever scaffold 51 is provided on the sea part 52a of the monopile type foundation 52, and includes an outer peripheral part 51a having a substantially circular shape in plan view protruding outward from the outer peripheral surface of the monopile type foundation 52 and a protruding part 51b protruding further outward from a part of the outer peripheral part 51a. The cantilever scaffold 51 is used for the maintenance and management work of the monopile type offshore wind power generation device 5 and as a temporary placement place for mechanical equipment.

[0037] The monopile foundation 52 exerts a desired supporting force against waves and tidal currents to support the monopile type offshore wind power generation device 5. Further, the monopile foundation 52 has a cylindrical outer shape, and a scour prevention portion 7 is formed at the seafloor periphery 6 which is the foundation periphery at the seafloor.

[0038] The power generation unit 53 is a wind turbine unit that generates power and is attached to the upper part of the monopile foundation 52. Further, the power generation unit 53 is formed by a known configuration. For example, the power generation unit 53 includes a tower connected to the upper part of the monopile foundation 52, a nacelle connected to the upper end of the tower and storing a generator and the like, blades forming a windmill, a hub connecting the nacelle and the blades, and a connecting portion connecting the monopile foundation 52 and the tower.

[0039] The mooring and lifting equipment 54 is connected to the overhanging scaffold 51 and provided in the upper sea part 52a, and is used as access equipment for workers to perform maintenance work and the like of the monopile type offshore wind power generation device 5 from the sea. The mooring and lifting equipment 54 includes a mooring portion for accessing the monopile type offshore wind power generation device 5 from the sea, and lifting equipment (fixed ladder) for accessing the overhanging scaffold 51 from the mooring portion.

[0040] The power transmission cable 55 electrically connects the power generation unit 53 and a power receiving facility (not shown) provided on land for receiving and supplying the power generated by the monopile type offshore wind power generation device 5. The power generated by the power generation unit 53 is transmitted to the power receiving facility by the power transmission cable 55. The power transmission cable 55 extends from the power generation unit 53 through the monopile foundation 52 to the seabed, and is laid on the seabed to reach the power receiving device, thereby supplying the power generated by the power generation unit 53.

[0041] The monopile-type offshore wind power generation device 5 is constructed by a known construction method. For example, it includes a step of transporting and driving the monopile-type foundation 52 to the construction site, a step of forming a filter layer 81 on the seabed periphery 6, a step of forming a bagged root reinforcement material layer 42 on the filter layer 81 to form an erosion prevention part 7, a step of connecting a power generation part 53 to the monopile-type foundation 52, and a step of laying a power transmission cable 55 from the wind turbine part to a power receiving facility provided on land.

[0042] Next, the actions and effects of the erosion prevention work construction unit and the erosion prevention work construction method according to the above-described embodiment of the present invention will be described with reference to FIGS. 1 to 5. First, the work ship 3 is brought close to and moored to the monopile-type offshore wind power generation device 5, and the filter layer forming material 8 provided on the work ship 3 is laminated on the seabed periphery 6 by a discharge part that discharges the filter layer forming material 8 to form the filter layer 81.

[0043] As shown in FIGS. 1 and 2, a plurality of bagged root reinforcement materials 41 are suspended via a plurality of third hooks 27 below the lower stage suspension beam 25. With the plurality of bagged root reinforcement materials 41 suspended, the marine crane 2 provided on the work ship 3 is operated to dispose the upper stage suspension beam 26 above the overhanging part 51b of the overhanging scaffold 51 and the lower stage suspension beam 25 below the overhanging part 51b. By the above operation, the overhanging part 51b is disposed in a state of being inserted between the lower stage suspension beam 25 and the upper stage suspension beam 26.

[0044] Also, the upper stage suspension beam 26 is suspended in a state where substantially no rotational moment is generated by the second wires 24 attached to both end portions 26a, 26a in plan view. Similarly, the lower stage suspension beam 25 is also suspended in a state where substantially no rotational moment is generated by the first wires 23 that extend vertically downward from the upper stage suspension beam 26 and are attached to both end portions 25a, 25a in plan view.

[0045] While maintaining the arrangements of the lower suspension beam 25, the upper suspension beam 26, and the cantilever portion 51b, the boom 20 is driven by the first control unit 28a to move a plurality of bagging root consolidating materials 41 to a desired installation position on the filter layer 81.

[0046] As shown in FIGS. 3 and 4, after moving a plurality of bagging root consolidating materials 41 to a desired installation position, the second control unit 28b extends the first wire 23 vertically downward. By the above operation, the lower suspension beam 25 descends while maintaining the position of the upper suspension beam 26, and the plurality of bagging root consolidating materials 41 are installed at the desired installation positions on the filter layer 81.

[0047] With the above mechanism, the upper suspension beam 26 and the lower suspension beam 25 form a two-stage suspension frame in which the cantilever scaffold 51 is disposed between them when installing the bagging root consolidating material 41 at the periphery 6 of the seabed. Therefore, the construction unit 1 can easily install the bagging root consolidating material 41 directly below or in the vicinity of the cantilever scaffold 51 without being affected by the cantilever scaffold 51 by lowering the lower suspension beam 25 while maintaining the arrangement of the upper suspension beam 26. Further, since the bagging root consolidating material 41 is installed by the lowering operation of the lower suspension beam 25, it is possible to prevent contact and damage due to contact between the wire, the suspension beam, the bagging root consolidating material, etc. and the monopile type offshore wind power generation device 5 during the installation work. Therefore, the installation work of the bagging root consolidating material 41 can be performed more safely.

[0048] By attaching the first wire 23 to both end portions 25a, 25a in plan view, it is possible to make the lower suspension beam 25 in a state where almost no rotational moment occurs during the installation work of the bagging root consolidating material 41. Similarly, by attaching the second wire 24 to both end portions 26a, 26a in plan view, it is possible to make the upper suspension beam 26 in a state where almost no rotational moment occurs during the installation work of the bagging root consolidating material 41. Therefore, the lower suspension beam 25 and the upper suspension beam 26 can be made in a mechanically more stable state (it is possible to easily maintain the moment balance with the suspended bagging root consolidating material 41). With the above mechanism, the safety during the installation work of the bag bottom consolidating material 41 can be further improved. Also, since the lower suspension beam 25 and the upper suspension beam 26 are in a stable state, it is possible to more easily prevent contact between the components of the floating crane 2, the bag bottom consolidating material 41, and the monopile type offshore wind power generation device 5.

[0049] The lower suspension beam 25 suspends the bag bottom consolidating materials 41 on each of a plurality of third hooks 27 provided on the lower surface and installs them simultaneously on the filter layer 81, so that a plurality of bag bottom consolidating materials 41 can be installed simultaneously in one installation work. Therefore, the labor and time for the construction of the bag bottom consolidating material layer 42 and the erosion prevention part 7 can be reduced.

[0050] The third hooks 27 that restrain the plurality of bag bottom consolidating materials 41 at desired positions on the filter layer 81 are opened by the operation of the third control unit 28c to release the restraint of all the bag bottom consolidating materials 41. The plurality of bag bottom consolidating materials 41 whose restraint has been released are installed at desired positions on the filter layer 81. As shown in FIG. 5, by repeating the above installation work until a desired stacking height is obtained, a bag bottom consolidating material layer 42 is formed, and a desired erosion prevention part 7 in which the filter layer 81 and the bag bottom consolidating material layer 42 are stacked on the sea bottom periphery 6 is formed.

[0051] Since the erosion prevention material 4 uses the bag bottom consolidating material 41, the weight of each erosion prevention material 4 increases, so it is also possible to prevent erosion of the sea bottom periphery 6 of the monopile type foundation 52 by a tsunami or the like in which the sea bottom surface flow velocity is greater than the wave and tidal current.

[0052] The erosion prevention part 7 forms a filter layer 81 on the sea bottom periphery 6 and a bag bottom consolidating material layer 42 on the filter layer 81, so that it is possible to prevent erosion of the sea bottom periphery 6 of the monopile type foundation 52 from occurring through the gaps between the bag bottom consolidating materials 41 that make up the bag bottom consolidating material layer 42.

[0053] The embodiments of the construction unit and construction method of the scour prevention work according to the present invention have been described above. However, the present invention is not limited to the above embodiments and can be appropriately modified without departing from the gist thereof. For example, the bag filling and root fixing material layer 42 may be directly formed on the seabed periphery 6. Further, the first wire 23 and the second wire 24 may be attached to the four corners in plan view of each of the lower suspension beam 25 and the upper suspension beam 26, or the first wire 23 and the second wire 24 may be attached to four or more positions in plan view of each suspension beam. Further, a configuration in which a stone material having a larger particle size than the filter layer forming material 8 is used as the scour prevention material 4 may be employed. Note that if it is possible to construct the scour prevention part on the water bottom periphery of the water structure provided with the overhanging scaffold, the water structure to which the present invention is applied is not limited to the monopile type offshore wind power generation device 5 of the present embodiment. For example, a pier provided with an overhanging scaffold may be used.

Description of Reference Numerals

[0054] 1 Construction unit of scour prevention work (construction unit) 2 Floating crane 3 Work ship 4 Scour prevention material 5 Monopile type structure (monopile type offshore wind power generation device) 6 Water bottom periphery (seabed periphery) 7 Scour prevention part 8 Filter layer forming material 20 Boom 21 First hook 22 Second hook 23 First wire 24 Second wire 25 Lower suspension beam 26 Upper suspension beam 27 Lower cable (third hook) 41 Bag filling and root fixing material 42 Bag filling and root fixing material layer 51 Overhanging scaffold 81 Filter layer

Claims

1. A construction unit for an anti-scouring work, which forms an anti-scouring part at the bottom periphery of a monopile-type structure having a cantilevered scaffold, comprising: A work ship on which a floating crane for installing an anti-scouring material to form the anti-scouring part is arranged; The floating crane: A lower suspension beam suspended by a first wire suspended from a first hook provided at the end of a boom that can move freely in all directions, arranged below the lower part of the cantilevered scaffold in the vertical direction, and having a lower cable for suspending the anti-scouring material; An upper suspension beam suspended by a second wire suspended from a second hook provided at the end of the boom, arranged above the lower part of the cantilevered scaffold in the vertical direction; Comprising; The lower suspension beam and the upper suspension beam are each formed such that the width in at least one direction is larger than the width orthogonal to the cantilever direction of the cantilevered scaffold; The second wire extends from the second hook and is attached to both ends of the upper suspension beam respectively; The first wire extends from the first hook and is attached to both ends of the upper suspension beam respectively, extends vertically downward from the upper suspension beam, and is attached to both ends of the lower suspension beam; The first wire and the second wire are each independently adjustable in suspension length; A construction unit for an anti-scouring work.

2. A construction method for an anti-scouring work using the construction unit for an anti-scouring work according to Claim 1, comprising: Extending the first wire vertically downward while maintaining the position of the upper suspension beam to lower the lower suspension beam; Installing the anti-scouring material suspended by the lower suspension beam at the bottom periphery; A construction method for an anti-scouring work.

3. The anti-scouring material is provided as a bagged root reinforcement material in which a plurality of stones are integrated into a massive body; Stacking the bagged root reinforcement materials at the bottom periphery to form the anti-scouring part; The construction method for an anti-scouring work according to Claim 2.

4. Arranging stones at the bottom periphery to form a filter layer; Stacking bagged root reinforcement materials in which a plurality of stones are integrated into a massive body on the filter layer to form a bagged root reinforcement material layer; Forming the anti-scouring part including the filter layer and the bagged root reinforcement material layer; The construction method for an anti-scouring work according to Claim 2.

5. A plurality of the lower cables are provided at the lower part of the lower suspension beam; Each of the plurality of lower cables can suspend the bag-packing root consolidating material, and installs the plurality of bag-packing root consolidating materials simultaneously. The method for constructing the erosion prevention work according to claim 3 or 4.

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