Method for recovering the platform on which the floating foundation is mounted

Abstract

To provide a method for recovering a trestle mounted with a floating type foundation, capable of recovering a trestle, from a barge, which enables the floating type foundation to be efficiently fabricated and to be safely and efficiently transported to the barge.SOLUTION: A method for recovering a trestle mounted with a floating type foundation to support a tower 82 of an offshore wind mill 80 comprises a towing-back process to allow: a plurality of concrete segments forming the floating type foundation 70 to be fabricated on respective independent trestles 40; the floating type foundation 70 to float on water by submerging a barge 90 in a state where the floating type foundation 70 is fabricated by assembling the plurality of segments respectively placed on a plurality of trestles 40 and mounted on the barge 90 together with the plurality of trestles 40; the barge 90 to float at a location apart from the floating type foundation 70; and the barge 90 to be towed back to a quay wall P. The method also has a recovery process to allow: a plurality of transport means 30 to move from the quay wall P to the barge 90; and the plurality of trestles 40 to be recovered from the barge 90 to the quay wall P with the plurality of transport means 30.SELECTED DRAWING: Figure 17

Description

[Technical Field]

[0001] The present invention relates to a method for recovering a platform on which a floating foundation is mounted. [Background technology]

[0002] Demand for renewable energy is increasing with the aim of reducing greenhouse gas emissions. Renewable energy sources include, for example, solar power generation, wind power generation, hydroelectric power generation, geothermal power generation, and biomass power generation. Wind power generation facilities are often installed in mountainous areas away from residential areas, as the noise and vibrations from wind turbines can have an impact on the living environment and the impact on living spaces must be fully considered. However, it is difficult to secure land in mountainous areas for installing large wind turbines, and it is also difficult to secure transportation routes to wind power generation facilities and install transmission lines, etc., so technological development is underway to install offshore wind turbines that make up wind power generation facilities on the sea (including on water or lakes). When constructing an offshore wind turbine on the sea, a floating foundation may be used as its foundation, and these floating foundations include semi-submersible, spar, purge, and TLP (Tension Leg Platform) types. Of these, the semi-submersible foundation (semi-submersible floating foundation) has a center column that supports the wind turbine tower (support), multiple side columns (three or four) spaced around the center column, and pontoons that connect the center column and side columns, and is a foundation with a relatively good track record due to its excellent stability against waves and sea breezes.

[0003] Conventional floating foundations are generally made of steel, which has led to rising manufacturing costs, and this problem becomes even more pronounced as the size of the floating foundations increases. Therefore, while it is possible to reduce production costs by fabricating a concrete floating foundation in a dock and towing it out to sea for installation, at present no method has been established for efficiently fabricating a concrete floating foundation using a platform in a dock, or for stably and efficiently transporting the platform and floating foundation to a barge, or for retrieving the platform from the barge. Therefore, a method is desired for retrieving the platform from a barge that enables efficient fabrication of a floating foundation and stable and efficient transport to the barge.

[0004] Patent Document 1 proposes a tower assembly method in which multiple tower components created by dividing the tower of an offshore wind turbine vertically are assembled on a jack-equipped platform constructed on a base installed on the ground. Meanwhile, Patent Document 2 proposes an installation method for offshore wind turbines in which the tower of the offshore wind turbine is divided vertically into multiple tower components that are assembled and installed offshore.This installation method includes a caisson installation process in which a caisson, which forms the base of the offshore wind turbine, is installed at the installation location of the offshore wind turbine, an assembly process in which multiple tower components are assembled in the caisson, and a blade installation process in which blades are attached to a nacelle attached to the topmost tower component in the caisson. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-80852 [Patent Document 2] Patent Publication No. 2021-76043 Summary of the Invention [Problem to be solved by the invention]

[0006] Although Patent Documents 1 and 2 describe an efficient tower assembly method, as mentioned above, they do not describe a method for retrieving the platform from the barge, which would enable efficient production of a floating foundation and stable and efficient transportation to the barge.

[0007] The present invention aims to provide a method for recovering a platform on which a floating foundation is mounted, which enables efficient fabrication of a floating foundation and stable and efficient transportation to a barge, and enables the platform to be recovered from a barge. [Means for solving the problem]

[0008] In order to achieve the above object, one aspect of the method for recovering a platform on which a floating foundation is mounted according to the present invention comprises: 1. A method for recovering a floating foundation-mounted platform that supports a tower of an offshore wind turbine, comprising: a retraction process in which a plurality of concrete segments forming the floating foundation are fabricated on their own platforms, and the floating foundation fabricated by connecting the plurality of segments on the platforms is mounted on a barge together with the platforms, the barge is submerged, the floating foundation is brought to the surface of the water, the barge is brought to a position away from the floating foundation, and the barge is retracted to the quay; and a recovery step of moving a plurality of transport means from the quay to the barge, and recovering the plurality of platforms from the barge to the quay by the plurality of transport means.

[0009] According to this aspect, multiple concrete sections are fabricated, and the sections are connected to form a floating foundation. When retrieving multiple mounting frames, the barge that has raised the floating foundation to the water is towed back to the quay, and then multiple transport means are moved from the quay to the barge, and the multiple mounting frames are retrieved from the barge to the quay by the multiple transport means, thereby enabling efficient and reliable retrieval of the mounting frames. Furthermore, the multiple concrete segments that form the floating foundation are fabricated on frames in their own fabrication yards, and then the multiple segments are transported together with their frames by transport means to a connecting yard, where each segment is connected on its frame to fabricate the floating foundation, thereby enabling efficient fabrication of concrete floating foundations in a dock.

[0010] Here, concrete segments refer to center columns, side columns, and pontoons made of reinforced concrete (RC), and more specifically, the components of the center column, side columns, and pontoons. Note that in this specification, "concrete" also includes SRC (Steel Reinforced Concrete) structures, which are primarily made of RC but also contain steel (S). Fabricating these segments on their own cradles improves transportability when transporting the fabricated segments together with the cradles to the connecting yard by transport means. Furthermore, at the connecting yard, the segments are connected together while mounted on their own cradles, and the floating foundation is then transported to the barge together with the multiple cradles, improving both connectivity at the connecting yard and transportability to the barge. The combination of good transportability from each fabrication yard to the fabrication yard, good connectivity at the connecting yard, and good transportability to the barge leads to efficient fabrication of the floating foundation and its transport to the barge. In the connecting yard, the floating foundation is fabricated by tensioning each section together with tendons such as PC (Prestressed Concrete) steel bars and PC steel wires. That is, in each fabrication yard, concrete sections are fabricated as PCa (Precast Concrete) bodies on a frame, and in the connecting yard, each PCa body (section) mounted on the frame is tensioned with tendons to fabricate a PCaPC (Precast Prestressed Concrete) floating foundation.

[0011] In another aspect of the method for recovering a platform on which a floating foundation is mounted according to the present invention, The recovery step is characterized in that the fixing of the plurality of mounts fixed to the barge is released.

[0012] According to this aspect, since the multiple mounting platforms are fixed to the barge, when the barge submerges, it is possible to prevent the multiple mounting platforms from separating from the barge and sinking into the water, making them impossible to recover. In this way, by releasing the multiple mounting platforms fixed to the barge and then recovering them to the quay by a transport means, it is possible to quickly recover the mounting platforms.

[0013] In another aspect of the method for recovering a platform on which a floating foundation is mounted according to the present invention, When the transport means is a self-propelled carriage equipped with a lifting mechanism for lifting the platform and lifting it off the ground, the recovery process is characterized in that the transport means moves the multiple platforms lifted up from the barge to the quay.

[0014] According to this aspect, the transport means is a self-propelled cart equipped with a lifting mechanism that lifts the platform and lifts it off the ground, which further improves the recoverability of the platform.

[0015] In another aspect of the method for recovering a platform on which a floating foundation is mounted according to the present invention, The barge is provided with a ballast room; The submersion of the barge is performed by injecting water into the ballast room; The barge is raised by discharging ballast water from the ballast room.

[0016] According to this aspect, the barge is submerged by injecting water into the ballast room equipped on the barge, and the barge is surfaced by discharging ballast water from the ballast room, thereby enabling the barge to be submerged and surfaced stably without equipping the barge with special equipment.

[0017] In another aspect of the method for recovering a platform on which a floating foundation is mounted according to the present invention, The barge has a support leg equipped with a lifting mechanism, The submersion of the barge is performed by lowering the lifting mechanism, The barge is raised by raising the lifting mechanism.

[0018] According to this aspect, the barge has support legs equipped with a lifting mechanism, and the barge is submerged by lowering the lifting mechanism and surfaced by raising the lifting mechanism, thereby enabling the barge to be submerged and surfaced stably without being affected by waves, etc. [Effects of the Invention]

[0019] According to the method of recovering a platform on which a floating foundation is mounted of the present invention, the platform can be recovered from a barge, which enables efficient manufacturing of a floating foundation and stable and efficient transportation to the barge. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is an overall perspective view of an example of a floating foundation manufacturing system according to an embodiment. [Figure 2] 1 is a perspective view of an example of a floating foundation manufactured by a method for manufacturing a floating foundation according to an embodiment. FIG. [Figure 3] 1 is a perspective view of an example of an offshore wind turbine manufactured by a method for manufacturing an offshore wind turbine according to an embodiment. FIG. [Figure 4A] FIG. 2 is a process diagram of an example of a manufacturing method for the floating foundation according to the first embodiment. [Figure 4B] 4B is a process diagram of an example of a method for manufacturing a floating foundation according to the first embodiment, following FIG. 4A. [Figure 5] 10A and 10B are diagrams showing an example of a method for manufacturing a floating foundation according to the second embodiment and an example of a method for manufacturing a floating foundation according to the third embodiment. [Figure 6] FIG. 1 is a perspective view of an example of a multi-axle truck. [Figure 7A] 1A and 1B are diagrams showing the arrangement of multi-axle carriages during the first transportation method for floating foundations, where (a) is a plan view of multiple multi-axle carriages transporting side columns, (b) is a plan view of multiple multi-axle carriages transporting pontoons, and (c) is a plan view of multiple multi-axle carriages transporting center columns. [Figure 7B] FIG. 10 is a diagram illustrating an example of a first transportation method in which a floating foundation is transported together with a frame by a plurality of multi-axle carriages. [Figure 8A] Figures showing the arrangement of multi-axle carriages during the second transportation method for floating foundations, where (a), (b), and (c) are plan views of multiple multi-axle carriages transporting side columns, (d), (e), and (f) are plan views of multiple multi-axle carriages transporting pontoons, and (g) is a plan view of multiple multi-axle carriages transporting a center column. [Figure 8B] FIG. 10 is a diagram illustrating an example of a second transportation method in which a floating foundation is transported together with a frame by a plurality of multi-axle carriages. [Figure 9] FIG. 1 is a process diagram of an example of a launching method for a floating foundation according to an embodiment. [Figure 10] 9, is a process diagram of an example of a launching method for a floating foundation according to an embodiment. [Figure 11] 10, is a process diagram of an example of a launching method for a floating foundation according to an embodiment. [Figure 12] 11 , is a process diagram of an example of a launching method for a floating foundation according to an embodiment. [Figure 13] Following Figure 12, this is a process diagram of an example of a method for launching a floating foundation according to an embodiment, and also a process diagram of an example of a method for recovering a platform on which the floating foundation according to an embodiment is mounted. [Figure 14] 13, this is a process diagram of an example of a method for recovering a platform on which a floating foundation according to an embodiment is mounted. [Figure 15] 14A to 14C are process diagrams illustrating an example of a method for recovering a platform on which a floating foundation according to an embodiment is mounted. [Figure 16] 15, this is a process diagram of an example of a method for recovering a platform on which a floating foundation according to an embodiment is mounted. [Figure 17] 16, this is a process diagram of an example of a method for recovering a platform on which a floating foundation according to an embodiment is mounted. [Figure 18] FIG. 1 is a diagram illustrating a method for manufacturing and towing an offshore wind turbine according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, a floating foundation manufacturing method and floating foundation manufacturing system, an offshore wind turbine manufacturing method, a floating foundation launching method, a floating foundation mounting frame recovery method, and an offshore wind turbine manufacturing and towing method according to embodiments will be described with reference to the accompanying drawings. Note that in this specification and drawings, substantially identical components may be designated by the same reference numerals to avoid redundant description.

[0022] [Manufacturing system and method for a floating foundation, and a manufacturing method for an offshore wind turbine according to an embodiment] First, an example of a floating foundation manufacturing method and a floating foundation manufacturing system, and an offshore wind turbine manufacturing method according to an embodiment will be described with reference to FIGS. 1 to 8. Here, Fig. 1 is an overall perspective view of an example of a floating foundation manufacturing system according to an embodiment, Fig. 2 is a perspective view of an example of a floating foundation manufactured by the floating foundation manufacturing method according to an embodiment, and Fig. 3 is a perspective view of an example of an offshore wind turbine manufactured by the offshore wind turbine manufacturing method according to an embodiment. Also, Figs. 4A and 4B are process diagrams of an example of a floating foundation manufacturing method according to the first embodiment, respectively. Also, Fig. 5 is a diagram showing both an example of a floating foundation manufacturing method according to the second embodiment and an example of a floating foundation manufacturing method according to the third embodiment.

[0023] In addition, in each figure, the steel bars that form each of the concrete (reinforced concrete) components that make up the floating foundation, as well as the tension members that form each component (connect multiple elements together) and connect each component together are omitted.

[0024] The fabrication system 60 shown in Fig. 1 is a system installed in a dock D for fabricating a floating foundation 70. The floating foundation 70 to be fabricated in the illustrated example is a semi-submersible foundation, but the floating foundation fabricated by the fabrication system 60 may be any other type of floating foundation, such as a spar type, purge type, or TLP type.

[0025] The production system 60 has a plurality of production yards 10 for producing a plurality of types of divided bodies that make up the semi-submersible foundation 70, transport paths 50 provided between each production yard 10, a transport means 30 that transports the divided bodies produced in each production yard 10 via the transport paths 50, and a connection yard 20 that connects each of the divided bodies transported by the transport means 30 to produce the floating foundation 70.

[0026] Within dock D, to the side of the quay P of the connecting yard 20, there is an offshore area S where the manufactured floating foundation 70 is towed and installed, and a barge 90 is moored to the quay P to load the manufactured floating foundation 70 and tow it to the designated installation location for installation.

[0027] 2, the semi-submersible foundation 70 has a concrete center column 70A, three concrete side columns 70B arranged at 120-degree intervals in a plan view in three directions around the center column 70A, and three concrete pontoons 70C connecting the central center column 70A to each side column 70B. The three 120-degree intervals are the longitudinal directions of the pontoons 70C, and are therefore referred to as pontoon axial directions.

[0028] The center column 70A includes a center column foundation 71 and a center tower 72 rising from the center column foundation 71, and the side column 70B includes a side column foundation 73 and a side tower 74 rising from the side column foundation 73.

[0029] The center tower 72 is a stack of multiple center tower elements 72a, the side tower 74 is a stack of multiple side tower elements 74a, and the pontoon 70C is a connection of multiple pontoon elements 75a.

[0030] These are fabricated as separate sections in various ways at a specific fabrication yard 10, and each separate section is transported to a connection yard 20 and connected to fabricate the floating foundation 70. Here, the semi-submersible foundation 70 to be fabricated is equipped with three side columns 70B, but it may also be in a form (not shown) in which four pontoons 70C are arranged at 90-degree intervals in a plan view around a center column 70A, and a side column 70B is connected to each pontoon 70C.

[0031] As shown in Fig. 2, each divided body is placed on its own stand 40. Each stand 40 has a mounting plate 41, a plurality of legs 42 protruding below the mounting plate 41, and an access space 43 below the mounting plate 41 into which the conveying means 30 enters.

[0032] Here, "a stand specific to each divided body" means that the number of stands 40 corresponds to each divided body at a 1:1 ratio. In addition, if the number of stands 40 is small compared to the number of divided bodies and each divided body is manufactured with a time lag, one stand 40 will be diverted from manufacturing multiple divided bodies to transporting them.

[0033] The center column 70A, the side columns 70B, and the pontoons 70C are mounted on their own platforms 40A, 40B, and 40D, respectively.

[0034] Returning to FIG. 1, each production yard 10 is provided inside a specific building 18. In the production yard 10, a gantry crane 15 for producing the sections is installed so as to be movable in the X1 direction along a plurality of rails 13.

[0035] In the fabrication yard 10, a frame 40 is installed, and the divided bodies are fabricated on the frame 40.

[0036] Here, the segment bodies come in various forms. Referring to Figure 2, the segment bodies include the center column foundation 71 and the side column foundations 73. The entire center tower 72 may be included in the segment body, or each center tower element 72a may be included in the segment body, or a portion (in an unfinished state) of the center tower 72 may be included in the segment body. The same applies to the side tower 74.

[0037] The pontoon 70C may also be included in its entirety in a divided body, or may include only a portion thereof (in an unfinished state). Here, the pontoon 70C in the illustrated example is a connected body of multiple pontoon elements 75a, but the pontoon may also be formed from a single pontoon element.

[0038] The divided bodies produced in the production yard 10 are produced on the platform 40, and then transported together with the platform 40 by the transport means 30 to the connection yard 20, where they are connected to other divided bodies on the platform 40.Therefore, the divided bodies can take on a variety of shapes depending on the extent to which they are produced on the platform 40 in the production yard 10.

[0039] For example, if the entire center column 70A is a segmented body, the entire center column 70A is fabricated as a segmented body on a frame 40 in a fabrication yard 10. On the other hand, if the center column foundation 71 and center tower 72 are fabricated on a specific frame 40 in a specific fabrication yard 10, the center column foundation 71 and center tower 72 are each fabricated as a segmented body. Here, each center tower element 72a that constitutes the center tower 72 may be fabricated individually, for example, inside a building 18, rather than on a frame 40, and then multiple center tower elements 72a may be placed on the frame 40 and tensioned with multiple tendons to fabricate the center tower 72; in this fabrication method as well, the center tower 72 is a segmented body.

[0040] In any case, the object mounted on the platform 40 and transported to the connection yard 20 together with the platform 40 by the transport means 30 is referred to in this specification as a "divided body." In addition to objects that are 100% manufactured (manufactured from start to finish) on the platform 40, objects that are manufactured in a location other than the platform and then connected together on the platform 40 are also considered to be included in the term "divided body."

[0041] In each production yard 10, concrete segments are produced as PCa bodies, and in the connection yard 20, each PCa body segment is tensioned with tendons to produce a PCaPC floating foundation.

[0042] Returning to Figure 1, in the illustrated example, the center column foundation 71, side column foundation 73, and pontoon 70C are fabricated on specific frames 40A, 40B, and 40D in specific fabrication yards 10A, 10B, and 10D, respectively. As for pontoon 70C, after multiple pontoon elements 75a are fabricated in a location other than frame 40D in fabrication yard 10D, the multiple pontoon elements 75a are tensioned with multiple tendons on frame 40D, whereby the pontoon elements 75a are fabricated.

[0043] Furthermore, the center tower element 72a and the side tower elements 74a are fabricated in a common fabrication yard 10C. The fabricated center tower elements 72a are connected to each other on a common frame 40 via tendons, and similarly, the side tower elements 74a are also connected to each other on the common frame 40 via tendons and transported together with the frame 40 to the connection yard 20. As already described, the center tower 72 and the side towers 74 may be fabricated in an unfinished state as separate bodies on the frame 40, transported to the connection yard 20, and then stacked sequentially on the center column foundation 71 and the side column foundation 73.

[0044] Figure 1 also shows the state in which the side column foundation 73 placed on the platform 40B is being transported in the X2 direction via the transport path 50 to the connecting yard 20 by the transport means 30, and the state in which the pontoon 70C placed on the platform 40D is being transported in the X2 direction via the transport path 50 to the connecting yard 20.

[0045] In the connection yard 20, heavy machinery 55 and the like are used as needed to interconnect the segments on multiple frames 40 via tendons, thereby fabricating the semi-submersible foundation 70. Then, as shown in Figure 3, an offshore wind turbine 80 is fabricated by connecting a tower 82 equipped with a wind turbine 84 to a center column 70A that constitutes the semi-submersible foundation 70. Here, the illustrated example shows a configuration in which the tower 82 is connected to the center column 70A, but a single wind turbine tower may also be connected to the side column 70B.

[0046] Here, methods of connecting the tower 82 to the semi-submersible foundation 70 include connecting the tower 82 while lifting it with heavy machinery 55 in the connection yard 20 as shown in Figure 1, connecting the tower 82 to the semi-submersible foundation 70 installed on the sea (offshore) using a barge equipped with a lifting machine at sea, and transporting the semi-submersible foundation 70 to a barge 90 moored to a quay P, loading it, and then connecting the tower 82 from the quay P using heavy machinery. Furthermore, as will be explained below with reference to Figure 18, there is also a method of connecting the tower 82 from the quay P using heavy machinery while the semi-submersible foundation 70 is floating on the water next to the quay P, without using a barge.

[0047] Next, an example of a method for manufacturing a floating foundation according to the first embodiment will be described with reference to Figures 4A, 4B, and 2. Here, Figures 4A, 4B, and 2 are, in order, process diagrams of an example of a method for manufacturing a floating foundation according to the first embodiment.

[0048] In the illustrated example, the manufacturing method is such that the center column foundation 71 and the three side column foundations 73 are manufactured as separate bodies on the frame 40 in a specific manufacturing yard 10 (manufacturing process, separate body manufacturing process).

[0049] Next, each segment is transported together with its own frame 40 by the transport means 30 to the connecting yard 20, where the center column foundation 71 and the three side column foundations 73 are positioned together with the frames 40 on which they are placed, and pontoon gaps G are provided between the center column foundation 71 and each side column foundation 73 so that the pontoons 70C can be inserted (transportation and positioning process). Here, the process of transporting the segments together with the frames 40 from each production yard 10 can also be referred to as the segment transport process.

[0050] That is, in the transport and positioning step, the center column base 71 and each side column base 73 are positioned in a posture that does not require movement when connecting the other divided bodies thereafter.

[0051] The center column foundation 71, the side column foundation 73, and each pontoon 70C all have an upper deck slab 76, a lower deck slab 77, and left and right side walls 78, with a hollow 79 formed inside that forms a ballast chamber. A plurality of corresponding sheath pipes (not shown) are provided at corresponding positions on the upper deck slab 76, lower deck slab 77, and side walls 78 of the center column foundation 71, the side column foundation 73, and each pontoon 70C, and tensioning materials (not shown) are inserted into each sheath pipe to tension the pipes, thereby connecting the center column foundation 71, the side column foundation 73, and each pontoon 70C.

[0052] Next, as shown in FIG. 4B, the pontoons 70C, which have been transported from the production yard 10 together with the frames 40D, are inserted into the pontoon gaps G in the Y1 direction (pontoon insertion step).

[0053] 4A and 4B is set to the longitudinal length t2 of the pontoon 70C plus an error length due to manufacturing error and / or connection error. This makes it possible to reliably insert the pontoon 70C into the pontoon gap G between the positioned center column foundation 71 and side column foundation 73, eliminating the construction work required to move at least one of the center column foundation 71 and side column foundation 73 when the pontoon 70C cannot be inserted.

[0054] Next, wet joints WJ filled with mortar or the like are constructed between the center column foundation 71 and the side column foundation 73 and the pontoon 70C, and these are tensioned with tendons to connect the center column foundation 71 and the side column foundation 73 to the pontoon 70C (pontoon connecting process). From the viewpoint of waterproofing, it is desirable to also construct wet joints WJ between adjacent pontoon elements 75a, between center tower elements 72a, and between side tower elements 74a.

[0055] Next, the center tower 72 is connected to the center column foundation 71 while being lifted using heavy machinery 55 or the like (center tower connecting process), and the side towers 74 are connected to each side column foundation 73 while being lifted using heavy machinery 55 or the like (side tower connecting process), thereby producing the semi-submersible foundation 70 shown in Figure 2. Here, the transportation and positioning process, pontoon insertion process, pontoon connecting process, center tower connecting process, and side tower connecting process can also be collectively referred to as the connecting process.

[0056] Although the individual tendons are not shown here, the center column 70A is fabricated by tensioning the center column foundation 71 and center tower 72 with a plurality of first tendons, and the side column foundation 73 and side tower 74 are fabricated with a plurality of second tendons with a plurality of side columns 70B. The pontoon 70C is fabricated in a specific fabrication yard 10C by tensioning a plurality of pontoon elements 75a with a plurality of third tendons. Then, in the pontoon connection process, the pontoon 70C is connected to the center column 70A and side column 70B with a plurality of fourth tendons in the connection yard 20. The first to fourth tendons may be PC steel rods or PC steel wires.

[0057] Furthermore, in the fabrication of a semi-submersible foundation (not shown) in which four pontoons 70C are arranged at 90-degree intervals around a center column 70A and a side column 70B is connected to each pontoon 70C, during the pontoon connecting process, it is preferable to use the same third tendon for the third tendon and the fourth tendon, and to tension the two pontoons 70C facing each other around the center column foundation 71 together with the center column foundation 71 using the same third tendon. According to this tensioning method, by tensioning the two pontoons 70C facing each other around the center column foundation 71 together with the center column foundation 71 using the same third tendon, a more efficient connection in the connection yard 20 can be achieved.

[0058] According to the manufacturing method for a floating foundation according to the first embodiment shown in the figures, the transport and positioning process makes it unnecessary to move the center column foundation 71 and each side column foundation 73 when connecting other segments thereafter, thereby enabling efficient connection between the segments.

[0059] Furthermore, as shown in Figure 4B, by fabricating the lower structure of the semi-submersible foundation 70 first and then connecting the upper structure, such as the center tower 72 and side towers 74, the upper structure can be connected to the lower structure in a stable position efficiently and with high construction safety.

[0060] Next, an example of a manufacturing method for a floating foundation according to the second and third embodiments will be described with reference to Figures 5 and 2. Note that Figure 4A will be referenced in the description of the manufacturing method according to the third embodiment.

[0061] The manufacturing method according to the second embodiment is a method in which, at a specific manufacturing yard 10, a center column 70A is manufactured on a mounting base 40A, and a side column 70B is manufactured on a mounting base 40B, and then these divided bodies are transported together with the mounting base 40 to a connection yard 20 for positioning, and pontoons 70C are inserted into each pontoon gap G and connected.

[0062] According to this manufacturing method, the number of steps for connecting the segments in the connecting yard 20 is reduced as much as possible, and therefore the efficiency of connecting the segments in the connecting yard 20 is significantly increased.

[0063] Furthermore, the manufacturing method according to the third embodiment is similar to the method shown in FIG. 4A in that, in the connecting yard 20, the center column foundation 71 and three side column foundations 73 are positioned together with the frames 40 on which they are placed, and then, as shown in FIG. 5, the center tower 72 and side towers 74 are connected to each foundation to manufacture the center column 70A and each side column 70B in advance, and finally, pontoons 70C are inserted into each pontoon gap G and connected.

[0064] Another method, not shown, is to first connect the side column foundation 73 and side column 70B to the pontoon 70C in the connection yard 20, and then move the three connecting bodies to connect them to the center column foundation 71 and center column 70A. Also, if the center column foundation 71 and part of the center tower 72 are manufactured as separate bodies, and similarly the side column foundation 73 and part of the side tower 74 are manufactured as separate bodies and transported to the connection yard 20, the pontoon 70C will be connected to these, and the remaining center tower element 72a of the center tower 72 and the remaining side tower element 74a of the side tower 74 will be connected to them.

[0065] The offshore wind turbine manufacturing method according to the embodiment is a method of connecting a semi-submersible foundation 70 manufactured by the floating foundation manufacturing method according to the first to third embodiments or the floating foundation manufacturing method according to the other embodiments described above, while lifting the tower 82 using heavy machinery 55 in the connection yard 20, as already explained. Another method is to tow the manufactured semi-submersible foundation 70 out to sea (offshore) and install it there, and then connect the tower 82 at sea using a barge equipped with a lifting machine. Another method is to transport the semi-submersible foundation 70 to a barge 90 moored to a quay P, load it on it, and then connect the tower 82 from the quay P using heavy machinery. Another method is to float the semi-submersible foundation 70 on the water beside the quay P without using a barge, as will be explained below with reference to FIG. 18 .

[0066] Next, an example of a transport means and an example of a method for transporting a manufactured floating foundation in the connection step of the manufacturing method of a floating foundation according to the embodiment will be described with reference to FIGS. FIG. 6 is a perspective view of an example of a multi-axle bogie. FIG. 7A is a diagram showing the arrangement of multi-axle bogies during a first transportation method for a floating foundation, where (a) is a plan view of multiple multi-axle bogies transporting side columns, (b) is a plan view of multiple multi-axle bogies transporting pontoons, and (c) is a plan view of multiple multi-axle bogies transporting a center column. FIG. 8A is a diagram showing the arrangement of multi-axle bogies during a second transportation method for a floating foundation, where (a), (b), and (c) are plan views of multiple multi-axle bogies transporting side columns, (d), (e), and (f) are plan views of multiple multi-axle bogies transporting pontoons, and (g) is a plan view of multiple multi-axle bogies transporting a center column. Furthermore, FIGS. 7B and 8B are diagrams illustrating an example of a first transportation method and a second transportation method, respectively, for transporting a floating foundation together with a platform using multiple multi-axle bogies.

[0067] The illustrated transport means 30 is a multi-axle bogie, an example of a self-propelled bogie, equipped with a lifting mechanism that lifts the platform 40 to remove it from the ground. The multi-axle bogie 30 is configured as a whole by having a plurality of axles 33 attached to a long car body 31 in the axial direction (L direction) of the car body, and each axle 33 having a plurality of pairs of left and right wheels 35 attached at intervals in the axial direction of the car body, all of which are attached to the corresponding axles 33 so as to be rotatable in the Y3 direction, and a loading platform 32 on the car body 31 is attached so as to be able to be raised and lowered by a lifting mechanism (not shown).

[0068] The multi-axle trolley 30 enters the entry space 43 of each platform 40 shown in Figure 2, etc., with the platform 32 lowered as in the illustrated example, and when transporting the platform 40 together with the divided body, the platform 32 can be raised by the lifting mechanism to allow the platform 40 to be lifted off the ground.

[0069] Although not shown in the drawings, the transport means may be such that the platform 40 is equipped with wheels driven by an actuator, and these driven wheels serve as the transport means. Alternatively, the platform 40 may be equipped with wheels, and the transport means may be a towable cart or a pushable cart. Furthermore, the transport means may be a mobile lifting machine such as a crane.

[0070] In the first transportation method for the floating foundation 70 shown in Fig. 7, in the connection process at the connection yard 20, each multi-axle bogie 30 is arranged so that the body axis direction (L direction) of each multi-axle bogie 30 is parallel to or perpendicular to at least one of the three pontoon axis directions, and each divided body is connected to fabricate the semi-submersible foundation 70. Here, the body axis direction of each multi-axle bogie 30 does not have to be strictly in these directions, but may also be in a direction that is shifted by a few degrees.

[0071] Next, when the semi-submersible foundation 70 is loaded out together with the multiple platforms 40 using the multiple multi-axle carts 30 and transported to the barge 90 moored at the quay P, all of the wheels 35 of all of the multi-axle carts can be controlled in the same or approximately the same direction, thereby moving all of the multi-axle carts 30 in the Y5 direction, which is the transport direction toward the barge 90. Here, controlling the wheels 35 in approximately the same direction means that there is an angle error of, for example, approximately ±10 degrees with respect to the reference wheel angle along the Y5 direction, which is the load-out direction.

[0072] According to this transportation method, when the semi-submersible foundation 70 is fabricated by connecting the segments on the multiple cradles 40 in the connecting yard 20, or when the semi-submersible foundation 70 has been fabricated on the multiple cradles 40 (both connection processes), by controlling all of the wheels 35 of all of the multi-axle bogies 30 to move in the same or approximately the same direction, it is possible to smoothly move the vehicle body axial direction (L direction) of each multi-axle bogie 30 in the desired load-out direction without having to specify a fixed direction, and it is possible to stably and smoothly transport the semi-submersible foundation 70 including the cradles 40 and load it onto the barge 90. Furthermore, there is no need to change the planar shape of the loading platform 32 of the multi-axle bogie 30 depending on the placement position; in other words, multi-axle bogies 30 equipped with loading platforms 32 of the same planar shape can be used without being restricted by the placement position.

[0073] On the other hand, in the second transportation method of the floating foundation 70 shown in Figure 8, during the connection process in the connection yard 20, each multi-axle bogie 30 is positioned with the body axis direction (L direction) of each multi-axle bogie 30 facing in the Y5 direction, which is the transportation direction toward the barge 90, and each divided body is connected to produce the semi-submersible foundation 70.

[0074] Next, when the semi-submersible foundation 70 is loaded out along with the multiple mounting platforms 40 onto the multiple multi-axle trolleys 30 and transported to the barge 90 moored at the quay P, each multi-axle trolley 30 can be moved in a straight line to move all of the multi-axle trolleys 30 in the Y5 direction, which is the transport direction toward the barge 90.

[0075] According to this transportation method, when the semi-submersible foundation 70 is fabricated by connecting the segments on multiple cradles 40 in the connecting yard 20, or when the semi-submersible foundation 70 has been fabricated on multiple cradles 40 (both are connecting processes), the wheels 35 can be moved straight ahead without controlling the angles of the wheels 35 to be in the same direction, allowing the foundation to be moved smoothly in the desired load-out direction, and the semi-submersible foundation 70 including the cradles 40 can be transported stably and smoothly and loaded onto the barge 90. Note that, in order to align the axial direction of the vehicle bodies of all multi-axle bogies 30 with the transport direction toward the barge 90, as shown in the figure, each multi-axle bogie 30 may need to be equipped with a loading platform 32 having a variety of shapes in plan view depending on its location.

[0076] Next, an example of a method for launching a floating foundation according to an embodiment and an example of a method for recovering a platform on which the floating foundation is mounted will be described with reference to FIGS. 9 to 13 are process diagrams showing an example of a launching method for a floating foundation according to an embodiment, and FIGS. 13 to 17 are process diagrams showing an example of a recovery method for a platform on which a floating foundation according to an embodiment is mounted.

[0077] As shown in Figure 9, the method for launching the floating foundation according to the embodiment involves mooring a barge 90 on the water S to the side of the quay P of the connecting yard 20 of the dock D, and then, as already explained, fabricating multiple concrete segments, each on its own platform 40, and connecting the multiple segments on the platforms 40 to fabricate the semi-submersible foundation 70.

[0078] Next, as shown in Fig. 10, the semi-submersible foundation 70 together with the multiple mounting frames 40 are transported in the Y7 direction to the barge 90 by multiple multi-axle carriages 30 and loaded onto the barge 90. Each mounting frame 40 transported onto, for example, the deck of the barge 90 is fixed to the deck (this completes the transport process).

[0079] Following this transportation process, the tower 82 may be connected to the semi-submersible foundation 70 from the quay P using heavy machinery to manufacture the offshore wind turbine 80, but here the following description will assume that the installation of the tower 82 is performed offshore.

[0080] After each mounting frame 40 is fixed to the barge 90, all multi-axle carriages 30 are moved (evacuated) in the Y8 direction to the connecting yard 20 as shown in Figure 11, and then, as shown in Figure 12, the barge 90 loaded with multiple mounting frames 40 and semi-submersible foundations 70 is moved (towed) in the Y9 direction to the offshore offshore wind turbine installation position.

[0081] Next, as shown in Figure 13, the barge 90 is submerged in the Y10 direction, and the semi-submersible foundation 70 is launched into the water. Here, the submergence method of the barge 90 is performed by pouring water into a ballast chamber (not shown) equipped in the barge 90. As another submergence method, if the barge 90 has support legs equipped with a lifting mechanism (not shown), the support legs can be lowered to submerge the barge (this is the launching process).

[0082] According to the method for launching a floating foundation shown in the figures, the semi-submersible foundation 70 can be efficiently transported to the barge 90, and after being transported to the barge 90, the semi-submersible foundation 70 can be towed to a predetermined position offshore and launched into the water, thereby achieving stable and smooth launching of the semi-submersible foundation 70.

[0083] On the other hand, in the method for recovering the platform on which the floating foundation of the embodiment is mounted, as shown in Figure 13, the semi-submersible foundation 70 is mounted on a barge 90 together with multiple platforms 40 at the installation position of the semi-submersible foundation 70, and the barge 90 is submerged in the Y10 direction at the installation position of the semi-submersible foundation 70, and after the semi-submersible foundation 70 is brought to the surface (floated), the barge 90 is moved in the Y11 direction to a position away from the semi-submersible foundation 70, as shown in Figure 14.

[0084] Here, if the barge 90 is equipped with a ballast room (not shown), the barge 90 can be submerged by injecting water into the ballast room, and the barge 90 can be surfaced by discharging ballast water from the ballast room. Additionally, if the barge 90 has support legs equipped with a lifting mechanism (not shown), the barge 90 can be submerged by lowering the lifting mechanism, and the barge 90 can be surfaced by raising the lifting mechanism.

[0085] Next, as shown in Figure 15, (part of) the barge 90 is raised onto the water in the direction Y12, and as shown in Figure 16, the barge 90 carrying multiple platforms 40 is pulled back to the quay P in the direction Y13 (pulling back process).

[0086] After the pulled-back barge 90 is moored to the quay P, the multiple multi-axle carriages 30 waiting in the connecting yard 20 are moved from the quay P to the barge 90 in the direction Y14.

[0087] The multiple mounting platforms 40 fixed to the deck of the barge 90 are released, the multiple multi-axle trolleys 30 are allowed to enter the entry spaces 43 of the corresponding mounting platforms 40, the loading platform 32 is raised to lift the mounting platforms 40 and remove them from the ground, and then, as shown in Figure 17, each multi-axle trolley 30 is moved in the direction Y15 from the barge 90 to the quay P, thereby recovering the multiple mounting platforms 40 from the barge 90 to the quay P (this is the recovery process).

[0088] According to the illustrated example of a method for recovering a mounting base on which a floating foundation is mounted, multiple concrete sections are manufactured and connected to form a semi-submersible foundation 70. When recovering multiple mounting bases 40, the barge 90 that has raised the semi-submersible foundations 70 to the water is towed back to the quay P, and then multiple multi-axle trolleys 30 are moved from the quay P to the barge 90, and the multiple mounting bases 40 are recovered from the barge 90 to the quay P by the multiple multi-axle trolleys 30, thereby enabling efficient and reliable recovery of the mounting bases 40.

[0089] Next, an example of a method for manufacturing and towing an offshore wind turbine according to an embodiment will be described with reference to Fig. 18. Here, Fig. 18 is a diagram for explaining a method for manufacturing an offshore wind turbine, among the methods for manufacturing and towing an offshore wind turbine.

[0090] As already explained, the offshore wind turbine manufacturing method shown in the figure differs from the method of connecting the tower 82 (see Figure 3) to the semi-submersible foundation 70 at the connection yard 20, or the method of connecting the tower 82 from the quay P to the semi-submersible foundation 70 mounted on a barge 90 on the water, in that the semi-submersible foundation 70 is floated above the water next to the quay P and the tower 82 is connected to the quay P.

[0091] In Figure 18, the dashed dotted lines indicate the seabed B and the quay wall P, as well as the water depth t5 and draft t6 of the semi-submersible foundation 70 before water is poured into the ballast room 79A equipped in the semi-submersible foundation 70. In contrast, the solid lines indicate the seabed B and the quay wall P, as well as the water depth t7 and draft t8 of the semi-submersible foundation 70 after water has been poured into the ballast room 79A, and the water depths t5 and t7 before and after water pouring are substantially unchanged.

[0092] The semi-submersible foundation 70 is lowered onto the water from the quay P by a mobile lifting machine 56 (heavy machinery) such as a crane, and water is poured into the ballast chamber 79A of the semi-submersible foundation 70 which is moored to the quay P, thereby adjusting the draft t8 of the semi-submersible foundation 70 to be smaller than the water depth t7 of the quay P, and lowering the level of the semi-submersible foundation 70 below the level before the water was poured in. This level adjustment makes it possible to lower the lifting height of the tower 82 by the heavy machinery 56 as low as possible, thereby improving the connectivity of the tower to the floating foundation (preparation process).

[0093] Next, the tower 82 is lifted and connected to the semi-submersible foundation 70, which has been raised above the water, using heavy machinery 56, thereby completing the offshore wind turbine 80 (see FIG. 3).

[0094] Here, by adjusting the level of the semi-submersible foundation 70 to be lowered, the semi-submersible foundation 70 can be placed on the seabed B beside the quay P.

[0095] According to this method, the semi-submersible foundation 70 can be stabilized in an immovable position when connecting the tower 82, thereby improving the yield when connecting the tower 82 to the semi-submersible foundation 70.

[0096] Furthermore, the method of connecting the tower 82 to the semi-submersible foundation 70 may not be the method using the mobile lifting machine 56, but may instead involve using an erection device (not shown) on the quay P to erect the tower 82 and connect it to the semi-submersible foundation 70. Alternatively, the tower 82 may be connected to the semi-submersible foundation 70 using a self-elevating work platform (SEP) on the water (the above is the offshore wind turbine manufacturing process).

[0097] Next, after the offshore wind turbine 80 is fabricated next to the quay P, the ballast water is drained from the ballast chamber 79A of the semi-submersible foundation 70, and the draft is returned to the draft for towing, after which the offshore wind turbine is towed to a designated position offshore (towing process).

[0098] In this towing process, ballast water is injected into the ballast chamber 79A as needed to increase the draft, thereby making it possible to tow the semi-submersible foundation 70 in a stable position.

[0099] According to the illustrated example of the method for fabricating and towing an offshore wind turbine, water is poured into the ballast chamber 79A of the semi-submersible foundation 70 to make the draft of the semi-submersible foundation 70 smaller than the water depth of the quay P, and the level of the semi-submersible foundation 70 is adjusted to be lowered, and then the tower 82 is connected to the semi-submersible foundation 70 in a state where it is floating above the water to fabricate the offshore wind turbine 80, thereby ensuring good connectivity of the tower 82 to the semi-submersible foundation 70. Then, after draining ballast water from the ballast chamber 79A and returning the draft to the draft for towing, the offshore wind turbine 80 can be towed safely to a predetermined position offshore.

[0100] It should be noted that the present invention is not limited to the configurations shown here, and other embodiments may be possible in which other components are combined with the configurations described in the above embodiments. In this regard, the present invention can be modified within the scope of the present invention, and can be appropriately determined depending on the application form. [Explanation of symbols]

[0101] 10, 10A, 10B, 10C, 10D: Production yard 13: Rail 15: Gantry crane 18: Building 20: Connecting Yard 30:Transportation means (multi-axle cart) 31: Body 32: Cargo bed 33: Axle 35: Wheels 40, 40A, 40B, 40C, 40D: Stand 41: Mounting plate 42: Legs 43: Approach space 50:Transport path 55: Heavy machinery (crane) 56: Mobile lifting equipment (cranes, heavy machinery) 60: Manufacturing system (floating foundation manufacturing system) 70: Floating foundation (semi-submersible foundation) 70A: Center column (split body) 70B: Side column (divided body) 70C: Pontoon (divided body) 71: Center column foundation (divided body) 72: Center tower (divided body) 72a: Center tower element (divided body) 73: Side column foundation (divided body) 74: Side tower (divided body) 74a: Side tower element (divided body) 75a: Pontoon element (divided body) 76:Upper floor version 77: Lower floor version 78: Side wall 79:Hollow 79A: Ballast room 80: Offshore wind turbines 82: Tower 84: Windmill 90: Barge D: Dock P: Pier S: Offshore (sea, water) G: Pontoon clearance WJ: Wet joint B: Undersea

Claims

1. 1. A method for recovering a floating foundation-mounted platform that supports a tower of an offshore wind turbine, comprising: a retraction process in which a plurality of concrete segments forming the floating foundation are fabricated on their own platforms, and the floating foundation fabricated by connecting the plurality of segments on the platforms is mounted on a barge together with the platforms, the barge is submerged, the floating foundation is brought to the surface of the water, the barge is brought to a position away from the floating foundation, and the barge is retracted to the quay; a recovery step of moving a plurality of transport means from the quay to the barge, and recovering the plurality of platforms from the barge to the quay by the plurality of transport means.

2. 2. The method for recovering a platform on which a floating foundation is mounted according to claim 1, wherein the recovery step includes releasing the plurality of platforms fixed to the barge.

3. 3. The method for recovering a platform on which a floating foundation is mounted according to claim 2, wherein, when the transport means is a self-propelled carriage equipped with a lifting mechanism for lifting the platform and lifting it off the ground, in the recovery step, the transport means moves the platform from the barge to the quay in a lifted state.

4. The barge is provided with a ballast room; The submersion of the barge is performed by injecting water into the ballast room; 2. The method for recovering a platform on which a floating foundation is mounted according to claim 1, wherein the floating of the barge is carried out by discharging ballast water from the ballast room.

5. The barge has a support leg equipped with a lifting mechanism, The submersion of the barge is performed by lowering the lifting mechanism, 2. The method for recovering a platform on which a floating foundation is mounted according to claim 1, wherein the barge is raised by raising the lifting mechanism.

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