Method for dismantling marine structures

Abstract

To provide a decomposition method of an offshore structure capable of safely decomposing the offshore structure with a tower and recovering them.SOLUTION: A decomposition method of an offshore structure comprises a setting step of setting a sheet-like structure next to the tower of the offshore structure, and a collapse step of tilting the main body of the offshore structure toward the sheet-like structure by cutting the tower.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for dismantling marine structures equipped with towers such as various observation facilities, communication facilities, lighting facilities, mining facilities, and power generation facilities (e.g., meteorological observation towers, power transmission towers, lighthouses, and offshore wind turbines). [Background technology]

[0002] Patent Document 1 discloses a removal method for safely removing a tension-moored float that moored a floating structure, such as an offshore wind turbine, equipped with a floating structure. In this method, safety is ensured by injecting water into a subsidence water injection section provided on the floating structure to sink the floating structure, and then cutting the mooring ropes in a slackened state.

[0003] Patent Document 2 discloses a method for dismantling a wind turbine without erecting scaffolding, in which a crane device installed inside the wind turbine tower is used to dismantle the tower one by one from the top. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-23233 [Patent Document 2] International Publication No. 2019 / 116511 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors of the present application are considering a method for dismantling an offshore structure equipped with a tower, in which high-altitude work is avoided as much as possible, the base of the tower is cut by explosion or laser, etc., and the main body of the offshore structure (the part above the cut position of the offshore structure) is toppled and then dismantled. However, when toppling the main body of the offshore structure, there is a risk that the main body of the offshore structure will sink into the sea and become impossible to recover.

[0006] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a method for dismantling an offshore structure that can safely dismantle an offshore structure equipped with a tower and recover the main body of the offshore structure. [Means for solving the problem]

[0007] In order to achieve the above object, a method for dismantling a marine structure according to at least one embodiment of the present disclosure includes: a transporting step of transporting the sheet-like structure toward a tower provided on the marine structure; an installation step of installing the sheet-like structure next to the tower; a collapse step of cutting the tower to collapse the main body of the marine structure toward the sheet-like structure; a recovery step of recovering the main body of the marine structure; Equipped with. [Effects of the Invention]

[0008] According to at least one embodiment of the present disclosure, there is provided a method for dismantling an offshore structure that can safely dismantle and recover an offshore structure having a tower. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a flowchart illustrating an outline of a method for dismantling a meteorological observation tower 2A according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram for explaining an example of a transport step (S101) shown in FIG. [Figure 3] FIG. 2 is a plan view for explaining an example of the setting step (S102) shown in FIG. [Figure 4] FIG. 2 is a plan view for explaining an example of the setting step (S102) shown in FIG. [Figure 5] FIG. 2 is a diagram for explaining an example of the collapsing step (S103) shown in FIG. [Figure 6] FIG. 2 is a plan view for explaining an example of the collapsing step (S103) shown in FIG. [Figure 7] 1. FIG. 6 is a diagram for explaining another example of the collapsing step (S103) shown in FIG. [Figure 8] FIG. 2 is a diagram for explaining an example of the collecting step (S104) shown in FIG. [Figure 9] FIG. 10 is a diagram illustrating an example in which a net is used as the sheet-like structure 4. [Figure 10] FIG. 10 is a diagram showing a state in which a sheet-like structure 4 (net) is installed so as to surround a tower 8A. [Figure 11] FIG. 1 is a diagram showing a state in which a main body 2a of a meteorological observation tower 2A is wrapped in a sheet-like structure 4 (net). [Figure 12] 1 is a flowchart showing an outline of a method for dismantling an offshore wind turbine 2 according to an embodiment of the present disclosure. [Figure 13] FIG. 13 is a diagram for explaining an example of a transport step (S201) shown in FIG. [Figure 14] FIG. 13 is a diagram for explaining an example of the setting step (S202) shown in FIG. [Figure 15] FIG. 13 is a plan view for explaining an example of the setting step (S202) shown in FIG. [Figure 16] FIG. 13 is a plan view for explaining an example of the setting step (S202) shown in FIG. [Figure 17] FIG. 13 is a plan view for explaining an example of the setting step (S202) shown in FIG. [Figure 18] FIG. 13 is a diagram for explaining an example of the collapsing step (S203) shown in FIG. [Figure 19] FIG. 13 is a plan view for explaining an example of the collapsing step (S203) shown in FIG. [Figure 20] FIG. 13 is a diagram for explaining another example of the collapsing step (S203) shown in FIG. [Figure 21] FIG. 13 is a diagram for explaining an example of the collecting step (S204) shown in FIG. [Figure 22] FIG. 10 is a diagram illustrating an example in which a net is used as the sheet-like structure 4. [Figure 23]FIG. 1 is a diagram showing a state in which a sheet-like structure 4 (net) is installed so as to surround a tower 8. [Figure 24] FIG. 1 is a diagram showing a state in which a main body 2a of a wind turbine 2 is wrapped in a sheet-like structure 4 (net). [Figure 25] FIG. 10 is a view showing a state in which a cover member 39 is provided on the tower 8. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the invention. For example, expressions expressing relative or absolute arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement exactly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. For example, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. On the other hand, the expressions "comprise," "include," "have," "includes," or "have" of one element are not exclusive expressions that exclude the presence of other elements.

[0011] (Method of dismantling a weather observation tower) FIG. 1 is a flowchart illustrating an overview of a method for dismantling a meteorological observation tower according to an embodiment of the present disclosure.

[0012] The dismantling method shown in Figure 1 includes a transporting step (S101) of transporting a sheet-like structure toward the tower (column) of the meteorological observation tower, an installation step (S102) of installing the sheet-like structure next to the tower, a collapse step (S103) of cutting the tower and collapsing the main body of the meteorological observation tower toward the sheet-like structure, and a recovery step (S104) of recovering the main body of the meteorological observation tower.

[0013] FIG. 2 is a diagram for explaining an example of the transport step (S101) shown in FIG. 2, the meteorological observation tower 2A includes a tower 8A erected on a foundation 37 fixed to the seabed, and a plurality of branch-like projections 5 branching out and extending from the tower 8A. Each of the branch-like projections 5 is provided with measuring equipment 9 for observing meteorological parameters (such as wind direction, wind speed, temperature, humidity, or rainfall).

[0014] 2, in S101, the sheet-like structure 4 is transported by ship 6 to the location where the meteorological observation tower 2A is installed. In S101, for example, the sheet-like structure 4 may be towed by the ship 6 for transportation, or if the sheet-like structure 4 is foldable, the sheet-like structure 4 may be towed or placed on the ship 6 in a folded state for transportation.

[0015] In the illustrated example, the sheet-like structure 4 is a membrane-like structure (sheet) including a first surface 4s (front surface) formed continuously in a plane and a second surface 4t (back surface) formed continuously in a plane on the side opposite the first surface 4s.

[0016] The material of the sheet-like structure 4 may be a material that floats on seawater, such as polyester, EVA (ethylene vinyl acetate), polypropylene, etc. The specific gravity of the sheet-like structure 4 may be, for example, 1.02 or less so that it floats on seawater.

[0017] The specific gravity of the sheet-like structure 4 may be such that the sheet-like structure 4 does not sink when the main body (described later) of the meteorological observation tower 2A is placed on the sheet-like structure 4. The material of the sheet-like structure 4 may be a material that does not float in seawater, and in this case, a float (described later) made of a material that floats in seawater may be attached to the sheet-like structure 4.

[0018] FIG. 3 is a diagram for explaining an example of the installation step (S102) shown in FIG. As shown in FIG. 3, in S102, a sheet-like structure 4 is installed next to the tower 8A. In the illustrated example, the sheet-like structure 4 is installed in a direction d1 in which the main body 2a of the meteorological observation tower 2A is tilted relative to the position of the tower 8A. In the illustrated example, the sheet-like structure 4 is floated on the sea surface next to the tower 8. Note that the main body 2a of the meteorological observation tower 2A refers to the portion of the meteorological observation tower 2A above the cutting position (described below) of the tower 8A, and includes, for example, a part of the tower 8 and some of the multiple branch-like projections 5. Furthermore, if the sheet-like structure 4 is transported in a folded state in S101, the folded sheet-like structure 4 is unfolded and installed next to the tower 8A in S102. Furthermore, "installing the sheet-like structure 4 next to the tower 8A" more specifically means installing the sheet-like structure 4 in the sea in any direction relative to the tower 8A so that the distance between the tower 8A and the sheet-like structure 4 is less than h, where h is the height of the tower 8A from the sea surface.

[0019] In S102, the sheet-like structure 4 may be fixed in place with tension applied to it using multiple ships 6 (see Figure 3) or multiple anchors 20 (see Figure 4) to prevent the sheet-like structure 4 from moving due to the influence of wind, waves, etc.

[0020] In the example shown in Fig. 3, the four corners of a rectangular sheet-like structure 4 in a plan view are fixed under tension by being pulled in four directions by ropes 16 by four ships 6. In the example shown in Fig. 4, in consideration of the safety of the ships 6, anchors 20 are provided via anchor cables 18 at each of the four corners of the rectangular sheet-like structure 4 in a plan view, and the sheet-like structure 4 is fixed under tension using the anchors 20.

[0021] Fig. 5 is a diagram for explaining an example of the collapse step (S103) shown in Fig. 1. The dashed line in Fig. 5 indicates a cutting position P1 where the tower 8A is cut in S103.

[0022] As shown in FIG. 5, in S103, the base portion 8r of the tower 8A may be cut by laser or explosion while the tower 8A is being pulled by a rope 24 or the like toward the sheet-like structure 4 on at least one ship 6.

[0023] In this case, as shown in Fig. 6, for example, two ships 6 may use ropes 24 to pull the tower 8A in two different directions g1 and g2 while cutting the tower 8A, thereby tipping the main body 2a of the meteorological observation tower 2A toward a direction d1 between the two directions g1 and g2. For example, two ships 6 may use ropes 24 to pull the tower 8A with equal force from two different directions g1 and g2 while cutting the tower 8A, thereby tipping the main body 2a of the meteorological observation tower 2A toward a direction d1 intermediate between the two directions g1 and g2. As shown in Fig. 6, by cutting the tower 8A and tipping the main body 2a of the meteorological observation tower 2A toward the sheet-like structure 4 (in other words, by positioning the sheet-like structure 4 in advance in the direction d1 in which the main body 2a of the meteorological observation tower 2A will tip relative to the tower 8A), the main body 2a of the meteorological observation tower 2A can be easily recovered using the sheet-like structure 4.

[0024] FIG. 7 is a diagram for explaining another example of the collapsing step (S103) shown in FIG. As shown in FIG. 7, in S103, a first incision C1, a second incision C2, and a third incision C3 may be formed in the tower 8A by a laser.

[0025] In the example shown in FIG. 7 , first, a laser a1 is irradiated onto a base portion 8r of the tower 8A from the sheet-like structure 4 side (one side) of the tower 8A so as not to penetrate the tower 8A, thereby forming a first incision C1 in the tower 8 (first irradiation step). Next, a laser a2 is irradiated onto the base portion 8r of the tower 8A from the sheet-like structure 4 side of the tower 8A at an angle different from the first incision C1 so as not to penetrate the tower 8A, thereby forming a second incision C2 in the tower 8A that connects to the first incision C1, and removing a portion (fragment) of the tower 8A between the first incision C1 and the second incision C2 from the tower 8A (second irradiation step). Then, a laser a3 is irradiated onto the base portion 8r of the tower 8A from the opposite side of the tower 8A from the sheet-like structure 4 (the other side) of the tower 8A, thereby forming a third incision C3 that connects to at least one of the first incision C1 and the second incision C2 (third irradiation step), thereby cutting the tower 8A. In the illustrated example, the first cut C1 and the third cut C3 are each formed horizontally in the base portion 8r of the tower 8A, and the second cut C2 is formed diagonally from above to below in the base portion 8r of the tower 8A.

[0026] By irradiating the lasers a1 to a3 as described above, the main body 2a of the meteorological observation tower 2A can be tilted toward the sheet-like structure 4 without having to tow the tower 8A by a ship. This makes it easy to safely retrieve the main body 2a of the meteorological observation tower 2A using the sheet-like structure 4.

[0027] 5, in the collapse step, if there is a direction in which branch-like projections 5 do not extend from tower 8A, that direction may be set as collapse direction d1. In this case, when main body 2a of meteorological observation tower 2A is in a collapsed state, the direction in which branch-like projections 5 do not extend from tower 8A is downward. Also, if there is no direction in which branch-like projections 5 do not extend from tower 8A, branch-like projections 5 extending in collapse direction d1 may be cut off before cutting tower 8A. This makes it possible to prevent damage to sheet-like structure 4 by branch-like projections 5.

[0028] FIG. 8 is a diagram for explaining an example of the collecting step (S104) shown in FIG. As shown in FIG. 8, in S104, the sheet-like structure 4 with the main body 2a of the meteorological observation tower 2A placed thereon is transported to the shore, and the main body 2a of the meteorological observation tower 2A is pulled up onto land and recovered.

[0029] In the example shown in Figure 8, the sheet-like structure 4 with the main body 2a of the meteorological observation tower 2A placed on it is towed by a ship 6 to the shore, and the main body 2a of the meteorological observation tower 2A is then lifted onto land using a crane 26. In S104, the main body 2a of the meteorological observation tower 2A may be disassembled into several parts at sea so that the weight of the object to be lifted by the crane 26 is within the allowable load of the crane 26. Furthermore, when the main body 2a of the meteorological observation tower 2A is to be lifted as a whole without being disassembled, the main body 2a of the meteorological observation tower 2A may be lifted using, for example, a large crane at a dock in a shipyard.

[0030] 8, a plurality of floats 28 are attached to the outer edge 4h of the sheet-like structure 4. The number of floats 28 may be determined so that the sheet-like structure 4 does not sink when the main body 2a of the meteorological observation tower 2A is placed on the sheet-like structure 4. However, if the specific gravity of the sheet-like structure 4 is small enough that the sheet-like structure 4 does not sink when the main body 2a of the meteorological observation tower 2A is placed on it, the floats 28 may not be provided.

[0031] According to the above-described method for dismantling a meteorological observation tower 2A, a sheet-like structure 4 is placed next to the tower 8A prior to cutting the tower 8A. Then, the tower 8A is cut and the main body 2a of the meteorological observation tower 2A is tilted toward the sheet-like structure 4. This prevents the main body 2a of the meteorological observation tower 2A from sinking into the sea, allowing the main body 2a of the meteorological observation tower 2A to be recovered. Furthermore, because the tower 8A is cut and the main body 2a of the meteorological observation tower 2A is tilted toward the sheet-like structure 4, the amount of work at height is reduced compared to when scaffolding is set up around the tower 8A while the tower 8A remains standing and the meteorological observation tower 2A is dismantled by working at height. This reduces the amount of work at height, allowing the meteorological observation tower 2A to be safely dismantled and recovered. Furthermore, by receiving the main body 2a of the fallen meteorological observation tower 2A with the sheet-like structure 4, waves caused by the main body 2a of the meteorological observation tower 2A are prevented from being generated and debris, dust, and the like from scattering from the main body 2a of the meteorological observation tower 2A are prevented.

[0032] Furthermore, as explained using Figures 3 and 4, by using a ship 6 or an anchor 20 to apply tension to the sheet-like structure 4 and fix it, it is possible to prevent the sheet-like structure 4 from moving due to the influence of wind, waves, etc., and the main body 2a of the meteorological observation tower 2A that has fallen down on the collapse step can be properly received and recovered by the sheet-like structure 4.

[0033] Furthermore, when the sheet-like structure 4 is transported in a folded state and then unfolded and installed next to the tower 8A, the sheet-like structure 4 can be easily transported while the unfolded sheet-like structure 4 can support a large marine structure such as a meteorological observation tower 2A.

[0034] Next, several other embodiments will be described with reference to Figures 9 to 11. In the above-described embodiments, the sheet-like structure 4 is a membrane-like structure including a first surface 4s formed continuously in a plane and a second surface 4t formed continuously in a plane on the opposite side to the first surface 4s. However, the sheet-like structure 4 may be a net-like structure (net), as exemplified in Figure 9. In this case, it is also possible to carry out the method for dismantling a meteorological observation tower 2A described with reference to Figures 1 to 8.

[0035] Furthermore, if the sheet-like structure 4 is a net-like structure, the meteorological observation tower 2A may be dismantled by the dismantling method described with reference to Figures 10 and 11. In the method for dismantling the meteorological observation tower 2A described with reference to Figures 10 and 11, the basic flow is the same as S101 to S104 shown in Figure 1, but the installation step of S102 and the recovery step of S104 are different from those in the above-described embodiment.

[0036] In the embodiment shown in Figures 10 and 11, the steps of transporting the sheet-like structure 4 to the location where the meteorological observation tower 2A is installed and cutting the tower 8A and tilting it toward the sheet-like structure 4 are the same as in the embodiment described above using Figure 1, etc., so we will not explain them here. Below, we will explain the steps of installing the sheet-like structure 4 and using the sheet-like structure 4 to transport the main body of the meteorological observation tower 2A to the shore and retrieve it.

[0037] 10, the sheet-like structure 4 is a net, and a plurality of floats 28 are attached at intervals to an upper edge 4u of the sheet-like structure 4, and a plurality of weights 23 are attached at intervals to a lower edge 4d of the sheet-like structure 4. A rope 46 is passed through the upper edge 4u of the sheet-like structure 4, and a rope 48 is passed through the lower edge 4d of the sheet-like structure.

[0038] 10, in the installation step of S102, the sheet-like structure 4 is deployed around the tower 8A (to the side of the tower 8A) using the ship 6 so that the sheet-like structure 4 surrounds the foundation 37 of the tower 8A. At that time, the ship 6 deploys the sheet-like structure 4 by passing inside the sheet-like structure 4 to avoid the tower 8A.

[0039] Specifically, first, one longitudinal end portion 4a of the sheet-like structure 4 is unfolded about halfway around the tower 8A along a first direction e1, which is one of the clockwise and counterclockwise directions in a plan view. Next, the longitudinal middle portion 4b of the sheet-like structure 4 is unfolded about one lap around the outer periphery of the tower 8A along a second direction e2, which is the other of the clockwise and counterclockwise directions (the opposite direction to the first direction e1) in a plan view. Next, the other longitudinal end portion 4c of the sheet-like structure 4 is unfolded about halfway around the outer periphery of the longitudinal middle portion 4b of the sheet-like structure 4 along the first direction e1. Then, the overlapping portions of the longitudinal middle portions 4b on one side of the tower 8A are fixed (coupled) using fasteners 40 at one location or at two locations at different distances from the tower 8A. In addition, it is preferable that one or two fixing points using the fixing device 40 are located on the opposite side to the collapse direction d1 of the main body 2a of the meteorological observation tower 2A, so that the main body 2a of the meteorological observation tower 2A can be easily wrapped in the sheet-like structure 4 when the fixing is later released.

[0040] As a result, in a plan view, the longitudinal middle portion 4b of the sheet-like structure 4 is arranged to surround the tower 8A, and the combination of the longitudinal one end side portion 4a and the longitudinal other end side portion 4c of the sheet-like structure 4 is arranged on the outer circumferential side of the longitudinal middle portion 4b to surround the tower 8A. In other words, the longitudinal middle portion 4b of the sheet-like structure 4 forms an inner circumferential ring 42 that surrounds the tower 8A, and the combination of the longitudinal one end side portion 4a and the longitudinal other end side portion 4c of the sheet-like structure 4 forms an outer circumferential ring 44 that surrounds the inner circumferential ring 42.

[0041] By installing the sheet-like structure 4 in this manner, when the tower 8A is cut in the collapse step (S103) and the main body 2a of the meteorological observation tower 2A is collapsed toward the sheet-like structure 4 (the opposite side from the fixing device 40 in the illustrated example), the main body 2a of the meteorological observation tower 2A can be accommodated between the inner ring 42 and the outer ring 44. In the collapse step, the sheet-like structure 4 is maintained in an unfolded state by pulling the sheet-like structure 4 with a ship in multiple directions away from the tower 8A (for example, directions 4 and 5 indicated by the white arrows in FIG. 10), and the tower 8A is cut in that state, thereby securing a large space inside the sheet-like structure 4 (between the inner ring 42 and the outer ring 44) for accommodating the main body 2a of the meteorological observation tower 2A. Here, when there is one fixing device 40, the side where a large space can be secured is limited to the side opposite the fixing device 40, so by tilting the main body 2a of the meteorological tower 2A on the side opposite the fixing device 40, it is possible to easily fit the main body 2a of the meteorological tower 2A inside the sheet-like structure 4. When there are two fixing devices 40, the outer ring 44 can be positioned farther from the inner ring 42, so that a large space can be secured in all directions, increasing the degree of freedom in the direction in which it can be tilted. After the sheet-like structure 4 is unfolded in this manner, before the collapse step (S203), the rope 48 passed through its lower edge 4d is pulled and tightened by the ship until the bottom of the sheet-like structure 4 closes, thereby preventing the collapsed structure from falling to the seabed.

[0042] In the recovery step (S104) after the collapse step, the fixing devices 40 are released at two locations, and the rope 46 passing through the upper edge 4u (float 28 side) of the sheet-like structure 4 and the rope 48 passing through the lower edge 4d (weight 23 side) are pulled and tightened by the ship, so that the sheet-like structure 4 is made into a bag shape and the main body 2a of the meteorological observation tower 2A is wrapped in the sheet-like structure 4, as shown in FIG. 11. This allows the main body 2a of the meteorological observation tower 2A, wrapped in the bag-shaped sheet-like structure 4, to be towed to land together with the sheet-like structure 4. When the ship arrives on land, the main body 2a of the meteorological observation tower 2A, still wrapped in the sheet-like structure 4, is pulled onto land by the crane 26 (see FIG. 10).

[0043] 10 and 11, a sheet-like structure 4 (net) is installed to surround the tower 8A, so that no matter which way the tower 8A falls, the main body 2a of the meteorological observation tower 2A can be contained within the sheet-like structure 4. Therefore, the sheet-like structure 4 can be used to more reliably prevent the main body 2a of the meteorological observation tower 2A from sinking into the sea, and the main body 2a of the wind turbine 2 can be easily recovered.

[0044] (Method of dismantling offshore wind turbines) 12 is a flowchart showing an outline of a method for dismantling an offshore wind turbine according to an embodiment of the present disclosure. Hereinafter, an offshore wind turbine will be simply referred to as a wind turbine.

[0045] The dismantling method shown in Figure 12 includes a transportation step (S201) of transporting a sheet-like structure toward the tower of the offshore wind turbine, an installation step (S202) of installing the sheet-like structure next to the tower, a collapse step (S203) of cutting the tower and collapsing the main body of the wind turbine toward the sheet-like structure, and a recovery step (S204) of recovering the main body of the wind turbine.

[0046] FIG. 13 is a diagram for explaining an example of the transporting step (S201) shown in FIG. 13, the wind turbine 2B includes a tower 8B, a wind turbine rotor 10, and a nacelle 11. The wind turbine rotor 10 includes a plurality of blades 12 and a hub 14 to which the plurality of blades 12 are attached, and the nacelle 11 supports the hub 14 so that it can rotate.

[0047] 13, in S201, the sheet-like structure 4 is transported by ship 6 to the location where wind turbine 2B is installed. In S201, for example, the sheet-like structure 4 may be towed by the ship 6 for transportation, or if the sheet-like structure 4 is foldable, the sheet-like structure 4 may be towed or placed on the ship 6 in a folded state for transportation.

[0048] In the illustrated example, the sheet-like structure 4 is a membrane-like structure (sheet) including a first surface 4s (front surface) formed continuously in a plane and a second surface 4t (back surface) formed continuously in a plane on the side opposite the first surface 4s.

[0049] The material of the sheet-like structure 4 may be a material that floats on seawater, such as polyester, EVA (ethylene vinyl acetate), or polypropylene. The specific gravity of the sheet-like structure 4 may be, for example, 1.02 or less so that it floats on seawater. In particular, if the sheet-like structure 4 is made of an oil sorbent (such as polypropylene) that absorbs oil, even if oil inside the main body 2b of the wind turbine 2B is scattered or leaked after the main body 2b of the wind turbine 2B is toppled in the collapse step described below, the oil can be collected by the sheet-like structure 4 made of the oil sorbent, thereby effectively preventing marine pollution.

[0050] Furthermore, the specific gravity of the sheet-like structure 4 may be such that the sheet-like structure 4 does not sink when the main body of the wind turbine 2B (described later) is placed on the sheet-like structure 4. Furthermore, the material of the sheet-like structure 4 may be a material that does not float in seawater, in which case a float (described later) made of a material that floats in seawater may be attached to the sheet-like structure 4.

[0051] Note that while the example shown in Figure 13 illustrates a monopile wind turbine 2B that includes a foundation 38 fixed to the seabed, the method for dismantling a wind turbine 2B according to the present disclosure can also be applied to any bottom-fixed wind turbine, such as the gravity type shown in Figure 14, monopile type, and jacket type, as well as floating wind turbines such as semi-submersible type, spar type, and tension rig type.

[0052] FIG. 15 is a diagram for explaining an example of the setting step (S202) shown in FIG. As shown in FIG. 15, in S202, the sheet-like structure 4 is installed next to the tower 8B. In the example shown, the sheet-like structure 4 is installed in a direction d1 in which the main body 2b of the wind turbine 2B is tilted relative to the position of the tower 8B. In the example shown, the sheet-like structure 4 is left floating on the sea surface next to the tower 8B. Note that the main body 2b of the wind turbine 2B refers to the portion of the wind turbine 2B above the cutting position (described below) of the tower 8B, and includes the wind turbine rotor 10, the nacelle 11 (see FIG. 13), and part of the tower 8B. Furthermore, if the sheet-like structure 4 was transported in a folded state in S201, then in S202, the folded sheet-like structure 4 is unfolded and installed next to the tower 8B. Furthermore, "installing a sheet-like structure 4 next to the tower 8B" means, more specifically, that if the height of the tower 8B from the sea surface is h, then installing the sheet-like structure 4 in the sea in any direction relative to the tower 8B so that the distance between the tower 8B and the sheet-like structure 4 is less than h.

[0053] In S202, the sheet-like structure 4 may be fixed in place with tension applied to it using multiple ships 6 (see Figure 15) or multiple anchors 20 (see Figure 16) to prevent the sheet-like structure 4 from moving due to the influence of wind, waves, etc.

[0054] In the example shown in Fig. 15, the four corners of a rectangular sheet-like structure 4 in a plan view are fixed by four ships 6 using ropes 16 to pull the four corners in four directions with tension. In the example shown in Fig. 16, in consideration of the safety of the ships 6, anchors 20 are provided via anchor cables 18 at each of the four corners of the rectangular sheet-like structure 4 in a plan view, and the sheet-like structure 4 is fixed in a state where tension is applied to the sheet-like structure 4 using the anchors 20.

[0055] In S202, the oil fence 22 may be installed so as to surround the sheet-like structure 4, for example, as shown in Fig. 16. In the example shown in Fig. 16, the oil fence 22 is installed so as to surround the tower 8B and the sheet-like structure 4, but the oil fence 22 may be installed so as to surround only the sheet-like structure 4 without surrounding the tower 8B.

[0056] Furthermore, when the wind turbine 2B is, for example, a semi-submersible offshore wind turbine (see FIG. 14), the shape of the sheet-like structure 4 may be formed to conform to the shape of the floating body 30 of the wind turbine 2B in a plan view, as shown in FIG. 17, for example. In the example shown in FIG. 17, the floating body 30 includes three lower hulls 32, and in a plan view, the three lower hulls 32 extend in directions that differ by 120 degrees from the position of the tower 8B. In the example shown in FIG. 17, the sheet-like structure 4 has a pentagonal shape in a plan view, including two sides that extend along two of the three lower hulls 32, and the two sides form an angle of 120 degrees.

[0057] Fig. 18 is a diagram for explaining an example of the collapse step (S203) shown in Fig. 12. The dashed line in Fig. 18 indicates a cutting position P1 where the tower 8B is cut in S203.

[0058] As shown in FIG. 18, in S203, the base 8r of the tower 8B may be cut by laser or explosion while the tower 8B is being pulled by a rope 24 or the like toward the sheet-like structure 4 by at least one ship 6.

[0059] In this case, as shown in Fig. 19, for example, two vessels 6 may use ropes 24 to pull the tower 8B in two different directions g1 and g2 while cutting the tower 8B, thereby tipping the main body 2b of the wind turbine 2B toward a direction d1 between the two directions g1 and g2. For example, two vessels 6 may use ropes 24 to pull the tower 8B with equal force from two different directions g1 and g2 while cutting the tower 8B, thereby tipping the main body 2b of the wind turbine 2B toward a direction d1 intermediate between the two directions g1 and g2. As shown in Fig. 19, by cutting the tower 8B and tipping the main body 2b of the wind turbine 2B toward the sheet-like structure 4 (in other words, by positioning the sheet-like structure 4 in advance in the direction d1 in which the main body 2b of the wind turbine 2B will tip relative to the tower 8B), the main body 2b of the wind turbine 2B can be easily recovered using the sheet-like structure 4.

[0060] FIG. 20 is a diagram for explaining another example of the collapsing step (S203) shown in FIG. As shown in FIG. 20, in S203, a first incision C1, a second incision C2, and a third incision C3 may be formed by a laser.

[0061] In the example shown in Fig. 20, first, a laser beam a1 is irradiated onto a base portion 8r of the tower 8B from the sheet-like structure 4 side (one side) of the tower 8B so as not to penetrate the tower 8B, thereby forming a first incision C1 in the tower 8B (first irradiation step). Next, a laser beam a2 is irradiated onto the base portion 8r of the tower 8B from the sheet-like structure 4 side of the tower 8B at an angle different from the first incision C1 so as not to penetrate the tower 8B, thereby forming a second incision C2 in the tower 8B that connects to the first incision C1, and removing a portion (fragment) of the tower 8B between the first incision C1 and the second incision C2 from the tower 8B (second irradiation step). Then, a laser beam a3 is irradiated onto the base portion 8r of the tower 8B from the opposite side of the sheet-like structure 4 of the tower 8B (the other side) to form a third incision C3 that connects to at least one of the first incision C1 and the second incision C2 (third irradiation step), thereby cutting the tower 8B. In the illustrated example, the first cut C1 and the third cut C3 are each formed horizontally in the base portion 8r of the tower 8B, and the second cut C2 is formed diagonally from above to below in the base portion 8r of the tower 8B.

[0062] By irradiating the lasers a1 to a3 as described above, the main body 2b of the wind turbine 2B can be tilted toward the sheet-like structure 4 without the need to tow the tower 8B with a ship. This makes it easy to safely recover the main body 2b of the wind turbine 2B using the sheet-like structure 4. 18 to 20, etc., it is desirable to tilt the main body 2b of the wind turbine 2B toward the front side or rear side of the main body 2b of the wind turbine 2B. This makes it possible to prevent the sheet-like structure 4 from being damaged by the blades 12b of the wind turbine 2B. Note that the front side and rear side of the main body 2b of the wind turbine 2B refer to the front side (upwind side) and rear side (downwind side) along the rotation axis of the wind turbine rotor 10 in the case of a horizontal axis wind turbine.

[0063] FIG. 21 is a diagram for explaining an example of the collecting step (S204) shown in FIG. As shown in FIG. 21, in S204, the sheet-like structure 4 with the main body 2b of the wind turbine 2B placed thereon is transported to the shore, and the main body 2b of the wind turbine 2B is pulled onto land and recovered.

[0064] 21, the sheet-like structure 4 with the main body 2b of the wind turbine 2B placed thereon is towed by a ship 6 to the shore, and the main body 2b of the wind turbine 2B is then lifted onto land using a crane 26. In S204, the main body 2b of the wind turbine 2B may be disassembled into several parts at sea so that the weight of the object to be lifted by the crane 26 is within the allowable load of the crane 26. Furthermore, when the main body 2b of a large wind turbine 2B is to be lifted as a whole without being disassembled, the main body 2b of the wind turbine 2B may be lifted using, for example, a large crane at a dock in a shipyard.

[0065] 21, a plurality of floats 28 are attached to the outer edge 4h of the sheet-like structure 4. The number of floats 28 may be determined so that the sheet-like structure 4 does not sink when the main body 2b of the wind turbine 2B is placed on the sheet-like structure 4. However, if the specific gravity of the sheet-like structure 4 is small enough that the sheet-like structure 4 does not sink when the main body 2b of the wind turbine 2B is placed on it, the floats 28 may not be provided.

[0066] According to the method for dismantling the wind turbine 2B described above, a sheet-like structure 4 is placed next to the tower 8B prior to cutting the tower 8B, and the tower 8B is then cut and the main body of the wind turbine 2B is toppled toward the sheet-like structure 4. This allows the main body 2b of the wind turbine 2B to be recovered while using the sheet-like structure 4 to prevent the main body 2b of the wind turbine 2B from sinking into the sea. Furthermore, because the tower 8B is cut and the main body 2b of the wind turbine 2B is toppled toward the sheet-like structure 4, the amount of work at height can be reduced compared to when scaffolding is set up around the tower 8B while the tower 8B remains standing and the wind turbine 2B is to be dismantled by working at height, allowing the wind turbine 2B to be safely dismantled and recovered. Furthermore, by receiving the main body 2b of the toppled wind turbine 2B with the sheet-like structure 4, it is possible to prevent waves from being created by the main body 2b of the wind turbine 2B and to prevent oil from scattering and leaking from the main body 2b of the wind turbine 2B.

[0067] Furthermore, as explained using Figures 15 and 16, by using a ship 6 or an anchor 20 to apply tension to the sheet-like structure 4 and fix it, it is possible to prevent the sheet-like structure 4 from moving due to the influence of wind, waves, etc., and the main body 2b of the wind turbine 2B that has fallen on the collapse step can be properly received and recovered by the sheet-like structure 4.

[0068] Furthermore, as explained using Figure 16 etc., by installing an oil fence 22 to surround the sheet-like structure 4 before the collapse step (S203), even if oil inside the wind turbine 2B scatters or leaks when and after the main body 2b of the wind turbine 2B is collapsed, the oil can be collected by the oil fence 22, thereby preventing marine pollution.

[0069] When the folded sheet-like structure is transported and then unfolded and installed next to the tower, the unfolded sheet-like structure 4 can support a large marine structure such as a wind turbine 2B while facilitating the transportation of the sheet-like structure 4.

[0070] Next, several other embodiments will be described using Figures 22 to 24. In the above-described embodiments, the sheet-like structure 4 is a membrane-like structure including a first surface 4s formed continuously in a plane and a second surface 4t formed continuously in a plane on the opposite side to the first surface 4s, but the sheet-like structure 4 may also be a net-like structure (net), as exemplified in Figure 22. In this case, it is also possible to carry out the method for dismantling a wind turbine 2B described using Figures 12 to 21.

[0071] Furthermore, if the sheet-like structure 4 is a net-like structure, the wind turbine 2B may be dismantled by the dismantling method described with reference to Figures 23 and 24. In the method for dismantling the wind turbine 2B described with reference to Figures 23 and 24, the basic flow is similar to S201 to S204 shown in Figure 12, but the installation step of S202 and the recovery step of S204 are different from those in the above-described embodiment.

[0072] In the embodiment shown in Figures 23 and 24, the steps of transporting the sheet-like structure 4 to the location where the wind turbine 2B is installed and cutting the tower 8B and tilting it toward the sheet-like structure 4 are the same as in the embodiment described above using Figure 12, etc., so we will not explain them here. Below, we will explain the steps of installing the sheet-like structure 4 and the steps of using the sheet-like structure 4 to transport the main body of the wind turbine 2B to the shore and recover it.

[0073] 23, the sheet-like structure 4 is a net, and a plurality of floats 28 are attached at intervals to an upper edge 4u of the sheet-like structure 4, and a plurality of weights 23 are attached at intervals to a lower edge 4d of the sheet-like structure 4. A rope 46 is passed through the upper edge 4u of the sheet-like structure 4, and a rope 48 is passed through the lower edge 4d of the sheet-like structure.

[0074] 23, in the installation step of S202, the sheet-like structure 4 is deployed around the tower 8B (to the side of the tower 8B) using the ship 6 so that the sheet-like structure 4 surrounds the foundation 38 of the tower 8B. At that time, the ship 6 deploys the sheet-like structure 4 by passing inside the sheet-like structure 4 to avoid the tower 8B.

[0075] Specifically, first, one longitudinal end portion 4a of the sheet-like structure 4 is unfolded about halfway around the tower 8B along a first direction e1, which is one of the clockwise and counterclockwise directions in a plan view. Next, the longitudinal middle portion 4b of the sheet-like structure 4 is unfolded about one lap around the outer periphery of the tower 8B along a second direction e2, which is the other of the clockwise and counterclockwise directions (the opposite direction to the first direction e1) in a plan view. Next, the other longitudinal end portion 4c of the sheet-like structure 4 is unfolded about halfway around the outer periphery of the longitudinal middle portion 4b of the sheet-like structure 4 along the first direction e1. Then, the overlapping portions of the longitudinal middle portions 4b on one side of the tower 8B are fixed (coupled) using fasteners 40 at one location or at two locations at different distances from the tower 8B. It is preferable that the one or two fixing points using the fixing device 40 are located on the opposite side to the collapse direction d1 of the main body 2b of the wind turbine 2B, so that the main body 2b of the wind turbine 2B can be easily wrapped in the sheet-like structure 4 when the fixing is later released.

[0076] As a result, in a plan view, the longitudinal middle portion 4b of the sheet-like structure 4 is arranged to surround the tower 8B, and the combination of the longitudinal one end side portion 4a and the longitudinal other end side portion 4c of the sheet-like structure 4 is arranged on the outer circumferential side of the longitudinal middle portion 4b to surround the tower 8B. In other words, the longitudinal middle portion 4b of the sheet-like structure 4 forms an inner circumferential ring 42 that surrounds the tower 8B, and the combination of the longitudinal one end side portion 4a and the longitudinal other end side portion 4c of the sheet-like structure 4 forms an outer circumferential ring 44 that surrounds the inner circumferential ring 42.

[0077] By installing the sheet-like structure 4 in this manner, when the tower 8B is cut in the collapse step (S203) and the main body 2b of the wind turbine 2B is collapsed toward the sheet-like structure 4 (the opposite side from the fixing device 40 in the illustrated example), the main body 2b of the wind turbine 2B can be accommodated between the inner circumference side ring 42 and the outer circumference side ring 44. In the collapse step, the sheet-like structure 4 and the oil fence 22 are maintained in an expanded state by pulling the sheet-like structure 4 and the oil fence 22 by a ship in multiple directions away from the tower 8B (for example, directions 4 and 5 indicated by white arrows in FIG. 23), and then the tower 8B is cut in this state, thereby ensuring a large space inside the sheet-like structure 4 (between the inner circumference side ring 42 and the outer circumference side ring 44) for accommodating the main body 2b of the wind turbine 2B. Here, when there is one fixing device 40, the side on which a large space can be secured is limited to the side opposite the fixing device 40, so by tilting the main body 2b of the wind turbine 2B to the side opposite the fixing device 40, it is possible to easily fit the main body 2b of the wind turbine 2B inside the sheet-like structure 4. When there are two fixing devices 40, the outer circumferential ring 44 can be positioned farther from the inner circumferential ring 42, so that a large space can be secured in all directions, and the degree of freedom in the direction in which it can be tilted can be increased. After the sheet-like structure 4 is unfolded in this manner, before the collapse step (S203), the rope 48 passed through its lower edge 4d is pulled and tightened by the ship until the bottom of the sheet-like structure 4 closes, thereby preventing the collapsed structure from falling to the seabed.

[0078] In the recovery step (S204) after the collapse step, the fixing by the fixing devices 40 at two points is released, and the rope 46 passing through the upper edge 4u (float 28 side) of the sheet-like structure 4 and the rope 48 passing through the lower edge 4d (weight 23 side) are pulled and tightened by the ship, so that the sheet-like structure 4 is made into a bag shape and the main body 2b of the wind turbine 2B is wrapped in the sheet-like structure 4 as shown in FIG. 24. In this state, the main body 2b of the wind turbine 2B wrapped in the bag-shaped sheet-like structure 4 can be towed to land together with the sheet-like structure 4. When the ship arrives on land, the main body 2b of the wind turbine 2B, still wrapped in the sheet-like structure 4, is pulled onto land by the crane 26 (see FIG. 21).

[0079] 23 and 24, a sheet-like structure 4 (net) is installed so as to surround the tower 8B, so that no matter which way the tower 8B falls, the main body 2b of the wind turbine 2B can be contained in the sheet-like structure 4. Therefore, the sheet-like structure 4 can be used to more reliably prevent the main body 2b of the wind turbine 2B from sinking into the sea, and the main body 2b of the wind turbine 2B can be easily recovered.

[0080] The present disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these modifications. 23, the rope 48 passing through the lower edge 4d of the sheet-like structure 4 (net) may be pulled and tightened in advance by a ship before the collapse step (S203). This allows the main body 2b of the wind turbine 2B to be recovered more reliably by the sheet-like structure 4.

[0081] Furthermore, for example, in the example shown in FIG. 21, in the recovery step (S204), the sheet-like structure 4 with the main body 2b of the wind turbine 2B placed on it is transported to the shore, and the main body 2b of the wind turbine 2B is pulled up onto land and recovered, but in other embodiments, after the collapse step (S203), the main body 2b of the wind turbine 2B may be dismantled and recovered using a heavy machinery ship (not shown) or the like before being transported to the shore.

[0082] Furthermore, for example, in each of the above-described embodiments, before the collapse step (S203), lid members 39 for restricting the intrusion of seawater into the interior of the tower 8B may be provided at each of the base portion 8r of the tower 8B and the tip portion 8t of the tower 8B, as shown in Fig. 25. These lid members 39 may be panel-shaped as shown in the figure, or may be balloon-shaped (not shown).

[0083] This makes it possible to prevent air from leaking from inside the tower 8B due to seawater entering the tower 8B when the tower 8B is cut using the collapse step to collapse the main body 2b of the wind turbine 2B, thereby making it easier for the tower 8B to float in seawater. This makes it difficult for the main body 2b of the wind turbine 2B to sink in the sea, and reduces the buoyancy required of the sheet-like structure 4 and / or float 28 to float the main body 2b of the wind turbine 2B in seawater. It also makes it possible to prevent oil, dust, etc. inside the tower 8B of the wind turbine 2B from scattering or flowing out to the outside of the tower 8B.

[0084] It is desirable that the lid member 39 on the base portion 8r side be provided above the cutting position P1 of the tower 8B (see, for example, FIG. 18) and at an appropriate distance from the cutting position P1 so as not to be affected by explosions of the tower 8B or lasers during the collapse step. In another embodiment, a float member may be attached to the tower 8B instead of the lid member 39 in order to float the tower 8B.

[0085] Furthermore, in each of the above-described embodiments, a method for dismantling a meteorological observation tower 2A and a method for dismantling a wind turbine 2B have been exemplified, but the present disclosure is applicable to a method for dismantling any marine structure equipped with a tower, not limited to the meteorological observation tower 2A and the wind turbine 2B.

[0086] The contents described in each of the above embodiments can be understood, for example, as follows.

[0087] (1) A method for dismantling an offshore structure (for example, the above-described meteorological observation tower 2A or wind turbine 2B) according to at least one embodiment of the present disclosure includes: A transport step of transporting a sheet-like structure (e.g., the above-mentioned sheet-like structure 4) toward a tower (e.g., the above-mentioned tower 8A or tower 8B) provided on the marine structure; an installation step of installing the sheet-like structure next to the tower; A collapse step of cutting the tower and collapsing the main body of the marine structure (for example, the main body 2a or the main body 2b) toward the sheet-like structure; a recovery step of recovering the main body of the marine structure; Equipped with.

[0088] According to the method for dismantling an offshore structure described in (1) above, a sheet-like structure is placed next to the tower prior to cutting the tower, and the tower is then cut and the main body of the offshore structure is tilted toward the sheet-like structure, thereby preventing the main body of the offshore structure from sinking into the sea using the sheet-like structure and allowing the main body of the offshore structure to be recovered. Furthermore, because the tower is cut and the main body of the offshore structure is tilted toward the sheet-like structure, the amount of work at height can be reduced compared to when scaffolding is erected around the tower while the tower remains standing and the offshore structure is dismantled by working at height, so the offshore structure can be safely dismantled and recovered.

[0089] (2) In some embodiments, in the method for dismantling a marine structure described in (1) above, In the installation step, the sheet-like structure is fixed while tension is applied to the sheet-like structure using a ship (for example, the ship 6 described above) or an anchor (for example, the anchor 20 described above).

[0090] According to the method for dismantling a marine structure described in (2) above, it is possible to prevent the sheet-like structure from moving due to the influence of wind, waves, etc., and the main body of the marine structure that has fallen over in the collapse step can be properly received and recovered by the sheet-like structure.

[0091] (3) In some embodiments, in the method for dismantling a marine structure according to (1) or (2), Before the collapse step, a step of installing an oil fence (for example, the oil fence 22 described above) so as to surround the sheet-like structure is provided.

[0092] According to the method for dismantling marine structures described in (3) above, even if oil inside the marine structure scatters or spills when or after the main body of the marine structure is toppled, the oil can be collected by an oil fence, thereby preventing marine pollution.

[0093] (4) In some embodiments, in the method for dismantling a marine structure according to any one of (1) to (3) above, The specific gravity of the sheet-like structure installed in the installing step is smaller than the specific gravity of seawater.

[0094] According to the method for dismantling a marine structure described above in (4), the buoyancy of the sheet-like structure can be utilized to prevent the main body of the marine structure from sinking into the sea, making it easier to recover the marine structure.

[0095] (5) In some embodiments, in the method for dismantling a marine structure according to any one of (1) to (4) above, A float (for example, the above-mentioned float 28) is attached to the sheet-like structure installed in the installation step.

[0096] According to the method for dismantling an offshore structure described above in (5), the buoyancy of the floats can be used to prevent the main body of the offshore structure from sinking into the sea, making it easier to recover the offshore structure.

[0097] (6) In some embodiments, in the method for dismantling a marine structure according to any one of (1) to (5) above, In the transporting step, the sheet-like structure is transported in a folded state, In the installation step, the folded sheet-like structure is unfolded and installed next to the tower.

[0098] According to the method for dismantling an offshore structure described in (6) above, the sheet-like structure is transported in a folded state in the transportation step, which makes it easy to transport the sheet-like structure in the transportation step. Also, the folded sheet-like structure is unfolded and installed next to the tower in the installation step, which makes it possible to handle the dismantling of large offshore structures.

[0099] (7) In some embodiments, in the method for dismantling a marine structure according to any one of (1) to (6) above, In the recovery step, the sheet-like structure with the main body of the marine structure placed thereon is towed to land, and the main body of the marine structure is pulled up onto land.

[0100] According to the method for dismantling an offshore structure described in (7) above, the main body of the offshore structure can be safely recovered to land.

[0101] (8) In some embodiments, in the method for dismantling a marine structure according to any one of (1) to (7) above, The collapsing step includes: a first irradiation step of irradiating the tower with a laser (for example, the above-mentioned laser a1) from one side of the tower in the horizontal direction so as not to penetrate the tower, and forming a first notch (for example, the above-mentioned first notch C1) in the tower; a second irradiation step of irradiating the tower with a laser (e.g., the above-mentioned laser a2) from the one side of the tower in the horizontal direction at an angle different from that of the first notch so as not to penetrate the tower, and forming a second notch (e.g., the above-mentioned second notch C2) in the tower that connects to the first notch; and a third irradiation step of irradiating the tower with a laser (e.g., the above-mentioned laser a3) from the other side of the tower opposite to the one side in the horizontal direction, to form a third notch (e.g., the above-mentioned third notch C3) that connects to at least one of the first notch and the second notch.

[0102] According to the method for dismantling a marine structure described in (8) above, the main body of the marine structure can be toppled toward the sheet-like structure without having to tow the tower with a ship, which makes it easy to safely recover the main body of the marine structure using the sheet-like structure.

[0103] (9) In some embodiments, in the method for dismantling a marine structure described in (8) above, In the collapse step, the tower is cut while being pulled in two different directions (for example, the above-mentioned directions g1 and g2).

[0104] According to the method for dismantling an offshore structure described in (9) above, by cutting the tower while pulling it with an appropriate force in the two different directions, the main body of the offshore structure can be toppled in a desired direction between the two different directions, which makes it easy to recover the main body of the offshore structure using a sheet-like structure.

[0105] (10) In some embodiments, in the method for dismantling a marine structure according to any one of (1) to (9) above, The sheet-like structure is made of an oil adsorbent material (such as the above-mentioned polypropylene) that adsorbs oil.

[0106] According to the method for dismantling a marine structure described in (10) above, even if oil inside the marine structure scatters or leaks after the main body of the marine structure is toppled, the oil can be collected by a sheet-like structure made of oil absorbent material, thereby preventing marine pollution.

[0107] (11) In some embodiments, in the method for dismantling a marine structure according to any one of (1) to (10) above, the marine structure is a wind turbine (e.g., the wind turbine 2 described above), In the collapsing step, the wind turbine body is collapsed to the front side or the rear side of the wind turbine body.

[0108] According to the method for dismantling a marine structure described in (11) above, by tilting the wind turbine body toward the front or rear side of the wind turbine body, it is possible to prevent the sheet-like structure from being damaged by the wind turbine blades.

[0109] (12) In some embodiments, in the method for dismantling a marine structure according to any one of (1) to (11) above, Before the collapse step, a step is provided in which a cover member (e.g., the above-mentioned cover member 39) is provided at each of the base portion of the tower (e.g., the above-mentioned base portion 8r) and the tip portion of the tower (e.g., the above-mentioned tip portion 8t) to restrict the intrusion of seawater into the interior of the tower.

[0110] According to the method for dismantling an offshore structure described in (12) above, when the tower is cut and the main body of the offshore structure is toppled in the collapse step, air leakage from the inside of the tower due to seawater intrusion into the tower can be suppressed, making the tower more likely to float in seawater. This makes it difficult for the main body of the offshore structure to sink in the sea, and reduces the buoyancy required for the sheet-like structure and / or floats to float the main body of the offshore structure in seawater. In addition, it is possible to suppress oil, dust, etc. inside the wind turbine tower from scattering or flowing out of the tower.

[0111] (13) In some embodiments, in the method for dismantling a marine structure according to any one of (1) to (12) above, The sheet-like structure is in the form of a film.

[0112] According to the method for dismantling an offshore structure described in (13) above, the main body of the offshore structure can be recovered by using a membrane-like structure to prevent the main body of the offshore structure from sinking into the sea. In addition, because the tower is cut and the main body of the offshore structure is tilted toward the membrane-like structure, the amount of work at height can be reduced compared to when scaffolding is erected around the tower and the offshore structure is dismantled by working at height, so the offshore structure can be safely dismantled and recovered.

[0113] (14) In some embodiments, in the method for dismantling a marine structure according to any one of (1) to (12) above, The sheet-like structure is in the form of a net.

[0114] According to the method for dismantling an offshore structure described in (14) above, the main body of the offshore structure can be recovered by using a net-like structure to prevent the main body of the offshore structure from sinking into the sea. In addition, because the tower is cut and the main body of the offshore structure is toppled toward the net-like structure, the amount of work at height can be reduced compared to when scaffolding is erected around the tower and the offshore structure is dismantled by working at height, and therefore the offshore structure can be safely dismantled and recovered.

[0115] (15) In some embodiments, in the method for dismantling a marine structure according to any one of (1) to (14) above, In the installation step, the sheet-like structure is installed so as to surround the tower.

[0116] According to the method for dismantling an offshore structure described in (15) above, the main body of the offshore structure can be contained in the sheet-like structure no matter which way the tower falls, and therefore, the sheet-like structure can be used to more reliably prevent the main body of the offshore structure from sinking into the sea. [Explanation of symbols]

[0117] 2A Weather Observation Tower 2a Main unit 2B Windmill 2b main body 4 Structures 4a Longitudinal end side 4b Longitudinal middle section 4c Other longitudinal end side 4d bottom edge 4u upper edge 4s 1st page 4t 2nd side 5 Branches 6 Ships 8A, 8B Tower 8r Root 8t tip 9. Measuring Instruments 10 Wind turbine rotor 11 Nacelle 12 blades 14 Hub 16 Rope 18 Anchor rope 20 Anchor 22 Oil Boom 23 weight 24 Rope 26 Crane 28 Float 30 Floating Body 32 Lower Hull 37 Basics 38 Basics 40 Fixtures 42 Inner ring 44 Outer ring 46 Rope 48 Rope C1 First cutting depth C2 Second cutting depth C3 Third cut P1 cutting position a1, a2, a3 laser d1 Collapse direction g1,g2 direction e1 1st direction e2 2nd direction

Claims

1. a transporting step of transporting the sheet-like structure toward a tower provided on the marine structure; an installation step of installing the sheet-like structure next to the tower; a collapse step of cutting the tower to collapse the main body of the marine structure toward the sheet-like structure; a recovery step of recovering the main body of the marine structure using the sheet-like structure; Equipped with A method for dismantling a marine structure, wherein the sheet-like structure is a sheet or net and is foldable.

2. 2. The method for dismantling a marine structure according to claim 1, wherein in the installing step, the sheet-like structure is fixed while applying tension to the sheet-like structure using a ship or an anchor.

3. A transport step of transporting a sheet-like structure toward a tower equipped on the marine structure; an installation step of installing the sheet-like structure next to the tower; a collapse step of cutting the tower to collapse the main body of the marine structure toward the sheet-like structure; a recovery step of recovering the main body of the marine structure; Equipped with A method for dismantling an offshore structure, comprising a step of installing an oil fence to surround the sheet-like structure before the collapsing step.

4. 4. The method for dismantling a marine structure according to claim 1, wherein the specific gravity of the sheet-like structure installed in the installing step is smaller than the specific gravity of seawater.

5. 5. The method for dismantling a marine structure according to claim 1, wherein a float is attached to the sheet-like structure installed in the installing step.

6. A transport step of transporting a sheet-like structure toward a tower equipped on the marine structure; an installation step of installing the sheet-like structure next to the tower; a collapse step of cutting the tower to collapse the main body of the marine structure toward the sheet-like structure; a recovery step of recovering the main body of the marine structure; Equipped with In the transporting step, the sheet-like structure is transported in a folded state, In the installation step, the folded sheet-like structure is unfolded and installed next to the tower.

7. 7. A method for dismantling a marine structure according to claim 1, wherein in the recovery step, the sheet-like structure with the main body of the marine structure placed thereon is towed to land, and the main body of the marine structure is pulled up to the land.

8. A transport step of transporting the sheet-like structure toward a tower equipped on the marine structure; an installation step of installing the sheet-like structure next to the tower; a collapse step of cutting the tower to collapse the main body of the marine structure toward the sheet-like structure; a recovery step of recovering the main body of the marine structure; Equipped with The collapsing step includes: a first irradiation step of irradiating the tower with a laser from one side of the tower in a horizontal direction so as not to penetrate the entire cross section of the tower, thereby forming a first notch in the tower; a second irradiation step of irradiating the tower with a laser from the one side of the tower in the horizontal direction at an angle different from that of the first notch so as not to penetrate the entire cross section of the tower, thereby forming a second notch in the tower connected to the first notch; a third irradiation step of irradiating the tower with a laser from the other side of the tower opposite to the one side in the horizontal direction to form a third notch connected to at least one of the first notch and the second notch.

9. 9. The method for dismantling a marine structure according to claim 8, wherein in the collapsing step, the tower is cut while being pulled in two directions different from each other.

10. A transport step of transporting the sheet-like structure toward a tower equipped on the marine structure; an installation step of installing the sheet-like structure next to the tower; a collapse step of cutting the tower to collapse the main body of the marine structure toward the sheet-like structure; a recovery step of recovering the main body of the marine structure; Equipped with A method for dismantling an offshore structure, wherein the sheet-like structure is made of an oil adsorbent material that adsorbs oil.

11. the marine structure is a wind turbine, The marine structure dismantling method according to claim 1 , wherein in the collapsing step, the wind turbine body is collapsed onto a front side or a rear side of the wind turbine body.

12. A transport step of transporting the sheet-like structure toward a tower equipped on the marine structure; an installation step of installing the sheet-like structure next to the tower; a collapse step of cutting the tower to collapse the main body of the marine structure toward the sheet-like structure; a recovery step of recovering the main body of the marine structure; Equipped with A method for dismantling an offshore structure, comprising the step of providing a cover member at each of the base and tip of the tower to restrict intrusion of seawater into the interior of the tower before the collapsing step.

13. A transport step of transporting the sheet-like structure toward a tower equipped on the marine structure; an installation step of installing the sheet-like structure next to the tower; a collapse step of cutting the tower to collapse the main body of the marine structure toward the sheet-like structure; a recovery step of recovering the main body of the marine structure; Equipped with A method for dismantling a marine structure, wherein the sheet-like structure is a membrane.

14. A transport step of transporting the sheet-like structure toward a tower equipped on the marine structure; an installation step of installing the sheet-like structure next to the tower; a collapse step of cutting the tower to collapse the main body of the marine structure toward the sheet-like structure; a recovery step of recovering the main body of the marine structure; Equipped with A method for dismantling a marine structure, wherein the sheet-like structure is in the form of a net.

15. The marine structure dismantling method according to claim 14 , wherein the installing step installs the sheet-like structure so as to surround the tower.

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