Method of constructing monopile foundation

Abstract

To provide a construction method of a monopile type foundation capable of constructing the monopile type foundation constituting a large-sized monopile type offshore wind power generation facility without using a corresponding large-sized self-elevating barge or self-navigating work barge.SOLUTION: A self-elevating barge 40 is stopped in a water area, and a transporting barge 20 loaded with a monopile 3 is moored in the water area. A lower part of the monopile 3 laid down sideways is supported by an erecting device 30 mounted on a carrying barge 20, and a crane 43 of a self-elevating barge 40 and the erecting device 30 are used to submerge and erect a lower end part side 3b of the monopile 3. A monopile 3 erected in a water area is moved to a pile guide part 51 of a driving auxiliary device 50 mounted on a self-elevating barge 40 by a crane 43. The monopile 3 is driven into the water bottom ground SB using the crane 43 and the driving device 45 in a state in which horizontal movement of the monopile 3 is restrained by the pile guide part 51.SELECTED DRAWING: Figure 14

Description

[Technical Field]

[0001] The present invention relates to a construction method for a monopile foundation, and more particularly to a construction method for a monopile foundation that can construct a monopile foundation that constitutes a large-scale offshore monopile wind power generation facility without using a correspondingly large self-elevating barge or self-propelled work vessel. [Background technology]

[0002] In the construction of a monopile-type offshore wind power generation facility, a monopile foundation is built in a body of water as a base for installing the tower, nacelle hub, and blades that make up the wind power generation device. A monopile foundation is constructed by driving a single monopile into the waterbed using a crane mounted on a self-propelled work vessel or a self-elevating platform (SEP vessel) (see, for example, Patent Document 1).

[0003] In the invention described in Patent Document 1, the upper part of a monopile (monopile-type steel pipe pile) is suspended by a first crawler crane mounted on a foundation pile driving SEP, and the lower part of the monopile is suspended by a second crawler crane mounted on a pile transport SEP, and the monopile that has been lying on its side is then erected. After that, the lifting device of the second crawler crane is removed from the monopile, and the erected monopile is suspended in midair by only the first crawler crane, and the monopile is inserted into a positioning and holding device provided on the foundation pile driving SEP.

[0004] When constructing a medium-sized monopile foundation, for example, where the monopile weighs between 500 tons and 1,000 tons, the construction method described in Patent Document 1 can be adopted by using a crane (first crawler crane) mounted on a medium-sized self-elevating barge (a SEP for foundation pile driving) with a maximum lifting load of between 1,200 tons and 1,600 tons. However, when constructing a large monopile foundation, for example, where the monopile weighs between 1,000 tons, a crane mounted on a medium-sized self-elevating barge with a maximum lifting load of between 1,200 tons and 1,600 tons cannot stably lift the monopile into the air. Therefore, to adopt the construction method described in Patent Document 1 for constructing a large monopile foundation, it is necessary to use a correspondingly large self-elevating barge with a crane with a maximum lifting load of between 2,500 tons. Similarly, when using a self-propelled work vessel instead of a self-lifting barge, it is necessary to use a large self-propelled work vessel with a crane that can lift a maximum load of, for example, 3,000 tons or more. However, such large self-lifting barges and self-propelled work vessels are rare in Japan, making their use difficult. Therefore, a new construction method was needed that could build the monopile foundations that make up large monopile offshore wind power generation facilities without using a large self-lifting barge or self-propelled work vessel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-37397 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a monopile foundation construction method that can construct a monopile foundation that constitutes a large-scale monopile offshore wind power generation facility without using a correspondingly large self-elevating barge or self-propelled work vessel. [Means for solving the problem]

[0007] In order to achieve the above object, the monopile foundation construction method of the present invention is a monopile foundation construction method for constructing a monopile foundation that constitutes a monopile offshore wind power generation facility using a self-elevating barge equipped with a crane and a driving auxiliary device, and a transport barge equipped with an erection device, in which the self-elevating barge is parked in a water area where the monopile foundation is to be constructed in a jacked-up state with its elevating legs touching the bottom of the water, the transport barge carrying a monopile that constitutes the monopile foundation and is laid sideways is moored in the water area near the self-elevating barge, and with the load of the lower part of the laid sideways monopile supported by the erection device, the upper end of the monopile is lifted by the crane toward above the erection device In both cases, the monopile is rotated around the rotation mechanism of the erecting device as a fulcrum, thereby submerging the lower end of the monopile in the water area near the transport barge and erecting it, the monopile erected in the water area is moved using the crane from the erecting device to the pile guide unit that constitutes the driving auxiliary device located on the outside of the self-elevating barge, the monopile is moved downward using the crane while the horizontal movement of the monopile is restrained by the pile guide unit, and the monopile is then driven into the waterbed using the crane and driving device while the horizontal movement of the monopile is restrained by the pile guide unit, thereby constructing the monopile foundation. [Effects of the Invention]

[0008] In this invention, the load of the lower part of a monopile lying sideways on a transport barge is supported by the erection device provided on the transport barge. Then, the crane of a self-elevating barge parked in a jacked-up state near the transport barge lifts the upper end of the monopile above the erection device, and rotates the monopile using the rotation mechanism of the erection device as a fulcrum. In this way, the monopile can be erected with its load supported by the crane of the self-elevating barge and the erection device. This reduces the load on the crane of the self-elevating barge, and makes it possible to stably erect the monopile using the crane of a smaller self-elevating barge, which was previously unavailable, even when constructing a large monopile foundation. Furthermore, by submerging the lower end of the monopile in the water near the transport barge and erecting it, buoyancy acts on the monopile, reducing the monopile's load on the crane of the self-elevating barge. Therefore, even when constructing a large monopile foundation, a crane on a small self-elevating barge, which was previously unavailable, can be used to stably transport the monopile erected in the water from the erection device to the pile guide unit constituting the driving auxiliary device located on the outside of the barge body of the self-elevating barge. The monopile's horizontal movement is then restrained (controlled) by the pile guide unit, and the crane moves the monopile downward, allowing it to land stably on the waterbed. Then, by driving the monopile into the waterbed using the crane and driving device while restraining the monopile's horizontal movement using the pile guide unit, the monopile can be driven stably and accurately. Therefore, the present invention allows a large monopile foundation to be constructed safely without using a correspondingly large self-lifting barge or self-propelled work vessel. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram illustrating a front view of a monopile-type offshore wind power generation facility with a wind power generation device installed on a monopile-type foundation. [Figure 2] This is an explanatory diagram showing, in plan view, a self-lifting barge parked in a jacked-up position in the waters where a monopile foundation is to be constructed, and a transport barge loaded with a monopile lying on its side moored in the waters near the self-lifting barge. [Figure 3] 3A is an explanatory diagram illustrating a monopile with an inner plug installed therein; FIG. 3A is an explanatory diagram illustrating a longitudinal cross-sectional view of a monopile with an inner plug installed therein; FIG. 3B is an explanatory diagram illustrating a cross-sectional view of the state before the inner plug is fixed to the monopile; FIG. 3C is an explanatory diagram illustrating a cross-sectional view of the state after the inner plug has been fixed to the monopile; and FIG. 3D is an explanatory diagram illustrating a cross-sectional view of the state after the inner hollow portion of the monopile has been closed by the inner plug fixed to the monopile. [Figure 4] This is an explanatory diagram showing, in a plan view, the state in which the lower part of the monopile lying sideways is set on the erection device mounted on the transport barge from the state shown in Figure 2, and the hoisting equipment of the crane mounted on the self-lifting barge is connected to the upper end of the monopile. [Figure 5] 5 is an explanatory diagram illustrating an enlarged plan view of the raising device in a state where the lower part of the monopile in FIG. 4 is set. FIG. [Figure 6] 5 is an explanatory diagram illustrating an enlarged front view of the raising device in a state where the lower part of the monopile in FIG. 4 is set. FIG. [Figure 7] 5 is an explanatory diagram showing an enlarged side view of the state in which the lower part of the monopile in FIG. 4 is set in the erection device and the hoisting gear of the crane is connected to the upper end of the monopile. [Figure 8] FIG. 8 is an explanatory diagram showing an enlarged side view of the state in which the upper end of the monopile is lifted upward from the state shown in FIG. 7 by a crane toward the raising device, the monopile is rotated using the raising device as a fulcrum, and the lower end of the monopile is submerged in the waters near the transport barge and raised up. [Figure 9] FIG. 9 is an explanatory diagram illustrating, in plan view, the state in which the monopile in FIG. 8 is erected in a water area near a transport barge. [Figure 10]This is an explanatory diagram illustrating, in a plan view, the situation in which a monopile erected in the water area from the erection device in the state shown in Figure 9 is moved by a crane to the pile guide section of the driving auxiliary device located outside the barge body of the self-lifting barge. [Figure 11] 11 is an explanatory diagram illustrating, in plan view, a state in which the monopile has been moved from the state shown in FIG. 10 to the pile guide section with the opening / closing section in an open position. FIG. [Figure 12] 12 is an explanatory diagram illustrating an enlarged plan view of the driving auxiliary device and monopile in the state shown in FIG. 11. FIG. [Figure 13] 13 is an explanatory diagram showing an enlarged plan view of the state in which the opening / closing portion of the pile guide portion is closed from the state shown in FIG. 12 and the monopile is gripped by the advancing / retracting portion of the pile guide portion. FIG. [Figure 14] 14 is an explanatory diagram illustrating an enlarged cross-sectional view of the driving auxiliary device and monopile in the state shown in FIG. 13. FIG. [Figure 15] FIG. 14 is an explanatory diagram illustrating the driving auxiliary device and monopile in the state shown in FIG. 13 as viewed from the front. [Figure 16] FIG. 16 is an explanatory diagram illustrating, from a front view, the state in which the monopile is moved downward by a crane from the state shown in FIG. 15, while the pile guide part holding the monopile is moved downward, causing the monopile to land on the bottom of the water. [Figure 17] This is an explanatory diagram showing, from a front view, the situation in which the monopile is released from the gripping state of the advancing / retreating part of the pile guide part from the state shown in Figure 16, and the horizontal movement of the monopile is restrained by the pile guide part, and the monopile is driven into the bottom ground using a crane and driving device. [Figure 18] This is an explanatory diagram illustrating a side view of the state in which the construction work of the monopile foundation from the state in Figure 17 has been completed, the monopile has been released from its restraint state by the pile guide section, and the pile guide section has been positioned (stored) on the barge body of the self-lifting barge. [Figure 19]19A and 19B are explanatory diagrams illustrating an inner plug of another embodiment installed inside a monopile, where (a) of FIG. 19 is an explanatory diagram illustrating a cross-sectional view of the state before the inner plug is fixed to the monopile, (b) of FIG. 19 is an explanatory diagram illustrating a cross-sectional view of the state after the inner plug has been fixed to the monopile, and (c) of FIG. 19 is an explanatory diagram illustrating a cross-sectional view of the state after the inner hollow portion of the monopile has been closed by the inner plug fixed to the monopile. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a construction method for a monopile foundation according to the present invention will be described based on the embodiment shown in the drawings.

[0011] As illustrated in FIG. 1 , this construction method involves constructing a monopile foundation 2 that constitutes a monopile offshore wind power facility 1. The monopile offshore wind power facility 1 is configured with the monopile foundation 2, which is made up of a single monopile 3 driven into the waterbed ground SB, and a wind turbine 4 installed on the monopile foundation 2. The monopile 3 is configured as a long tubular body made of metal. In this embodiment, the monopile 3 has a shape that tapers from the top to the bottom, but the shape of the monopile 3 is not limited to this embodiment. In the following description, when the monopile 3 is driven into the waterbed ground SB, the lower portion of the monopile 3 will be referred to as the lower portion of the monopile 3, and the upper portion of the monopile 3 will be referred to as the upper portion of the monopile 3.

[0012] When the monopile foundation 2 is constructed, the lower part of the monopile 3 is inserted into the waterbed ground SB, and the upper end 3a of the monopile 3 is positioned above the water. The wind turbine generator 4 is composed of a tower 5 fixed to the upper end 3a of the monopile foundation 2 (monopile 3), a nacelle hub 6 installed at the upper end of the tower 5, and a plurality of blades 7 attached to the nacelle hub 6.

[0013] This construction method is particularly suitable for constructing large monopile foundations 2 in which the weight of the monopiles 3 that make up the monopile foundation 2 is, for example, between 1,000 t and 2,000 t. The length (height) of the monopiles 3 that make up the large monopile foundation 2 is, for example, between 50 m and 100 m, and the outer diameter (thickness, width) of the monopile 3 is, for example, between 5 m and 10 m. The large monopile foundation 2 is constructed in a water area with a depth of, for example, between 10 m and 50 m.

[0014] As shown in Figure 2, this construction method uses a self-elevating barge 40 (hereinafter referred to as SEP vessel 40) equipped with a crane 43 and a driving support device 50, and a transport barge 20 equipped with an erection device 30. In the figure, the longitudinal direction of the SEP vessel 40 moored in the water area where the monopile foundation 2 is to be constructed is the X direction, the width direction of the SEP vessel 40 is the Y direction, and the up-down direction is the Z direction.

[0015] The SEP vessel 40 is equipped with a barge body (platform) 41 that can move on the water, and a plurality of lifting legs 42 that can move up and down relative to the barge body 41. The barge body 41 of the SEP vessel 40 is equipped with a crane 43 and a concrete driving auxiliary device 50. The concrete driving auxiliary device 50 is a device used for the work of landing the monopile 3 on the waterbed ground SB and the work of driving concrete. Details of the concrete driving auxiliary device 50 will be explained later.

[0016] In this embodiment, a crane 43 is arranged near the starboard side of the stern of the SEP vessel 40, and a driving auxiliary device 50 is arranged at the stern of the SEP vessel 40. The crane 43 of the SEP vessel 40 may be a crane fixed to the barge main body 41, or may be a crane that is movable on the barge main body 41 (e.g., a crawler crane). A driving device 45 (e.g., a hydraulic hammer or vibro hammer) used to drive the monopiles 3 is loaded on the barge main body 41 of the SEP vessel 40. It is preferable to use a self-propelled SEP vessel 40 equipped with a propulsion device on the barge main body 41, but it is also possible to use a non-self-propelled SEP vessel 40 that does not have a propulsion device and is moved by towing.

[0017] This embodiment illustrates the construction of a large monopile foundation 2, in which the weight of the monopile 3 is, for example, between 1,000t and 2,000t, using a medium-sized SEP vessel 40, in which the maximum lifting load of the crane 43 is, for example, between 1,200t and 1,600t.

[0018] The transport barge 20 is a barge used to transport the monopile 3, and is, for example, a steel barge. The transport barge 20 comprises a barge body 21 and an erection device 30. The erection device 30 is a device used to erect a monopile 3 that has been laid on its side. The erection device 30 is mounted on the barge body 21. Details of the erection device 30 will be explained later.

[0019] The monopile 3 is loaded in a laid-on state on the barge main body 21. The monopile 3 loaded on the barge main body 21 extends in the longitudinal direction of the barge main body 21. In this embodiment, a plurality of support bases 24 for supporting the laid-on monopile 3 and a multi-axle bogie 25 are mounted on the barge main body 21 of the transport barge 20. The multi-axle bogie 25 is used to move the monopile 3 on the barge main body 21. In this embodiment, three monopiles 3 are loaded on the barge main body 21 lined up in the width direction of the barge main body 21, but the number of monopiles 3 loaded on the barge main body 21 is not particularly limited. In this embodiment, two multi-axle bogies 25 are mounted on the barge main body 21, but the number of multi-axle bogies 25 to be mounted on the barge main body 21 can be determined appropriately depending on the weight of the monopile 3 and the load capacity of the multi-axle bogies 25.

[0020] When the monopile 3 is placed on the multiple support stands 24, a gap is provided between the lower side of the monopile 3 and the upper surface of the barge main body 21 so that the multi-axle trolley 25 can enter. In other words, the multiple support stands 24 position the monopile 3 at a higher position than the upper surface of the barge main body 21. In this embodiment, the monopile 3 loaded on the barge main body 21 does not protrude outside the barge main body 21, but part of the loaded monopile 3 may protrude outside the barge main body 21, for example. In other words, the barge main body 21 may be large enough so that part of the monopile 3 protrudes.

[0021] It is preferable to use a self-propelled transport barge 20 equipped with a propulsion device (e.g., thrusters 23a) on the barge main body 21, but it is also possible to use a non-self-propelled transport barge 20 that is towed and moved without a propulsion device. The transport barge 20 is moored to the water area using mooring means 22. Examples of the mooring means 22 include mooring ropes and anchors. The transport barge 20 of this embodiment is equipped with a maneuvering device 23 (a so-called dynamic position system) that controls multiple thrusters 23a provided on the barge main body 21 based on GNSS positioning information, etc., and enables the transport barge 20 to be kept at a fixed position or to move as desired.

[0022] The erection device 30 may be disposed at either the stern or bow of the transport barge 20 (barge body 21). In this embodiment, the erection device 30 is disposed at the stern of the transport barge 20. The monopile 3 loaded on the transport barge 20 is disposed in such a direction that the lower end 3b faces the side where the erection device 30 is disposed.

[0023] As illustrated in (a) to (d) of Figure 3, in this construction method, it is preferable to use an inner plug 10 that is installed in the inner hollow portion of the monopile 3. In this embodiment, inner plugs 10 (10A, 10B) are installed in the lower end 3b and the upper end 3a of the monopile 3, respectively. The inner plugs 10 are configured so that the inner hollow portion of the monopile 3 can be switched between an open state and a closed state by opening and closing them. The inner plug 10 is configured to have a central control unit 11 that is smaller than the inner diameter of the monopile 3, multiple arms 12 that protrude outward from the central control unit 11, and an annular expansion / contraction unit 13 that is arranged on the outer periphery of the central control unit 11.

[0024] In this embodiment, when viewed from above the monopile 3, four arms 12 are arranged radially around the central control unit 11. As illustrated in (b) to (d) of Figure 3, each arm 12 is configured to be extendable and retractable in the radial direction (width direction) of the monopile 3. The arm 12 in this embodiment is configured such that a contact portion that contacts the inner surface of the monopile 3 is provided at the tip of a rod that constitutes an actuator (for example, a hydraulic cylinder or a pneumatic cylinder).

[0025] As illustrated in (b) of Figure 3, when the multiple arms 12 are retracted, the inner plug 10 can be moved relative to the monopile 3. As illustrated in (c) and (d) of Figure 3, when the multiple arms 12 are extended, the inner plug 10 (central control unit 11) can be fixed to the monopile 3. In this embodiment, the multiple arms 12 can be controlled by remotely operating the central control unit 11 using a controller.

[0026] The expansion / contraction unit 13 is configured to be expandable / contractable in the radial direction (width direction) of the monopile 3. As illustrated in (b) and (c) of FIG. 3, when the expansion / contraction unit 13 is contracted, a gap is generated between the expansion / contraction unit 13 and the inner peripheral surface of the monopile 3, and the inner space of the monopile 3 is open. As illustrated in (d) of FIG. 3, when the expansion / contraction unit 13 is expanded, the gap between the central control unit 11 and the inner peripheral surface of the monopile 3 is blocked by the expansion / contraction unit 13, and the inner space of the monopile 3 is closed. By adjusting the degree of expansion / contraction of the expansion / contraction unit 13, the size of the gap between the outer peripheral end of the expansion / contraction unit 13 and the inner peripheral surface of the monopile 3 can also be adjusted.

[0027] In this embodiment, the expansion / contraction unit 13 is configured with a bag portion 13a having an outer shape formed in a circular ring shape. The bag portion 13a may be formed of, for example, elastic rubber or resin. In this embodiment, by remotely operating the central control unit 11 using a controller, it is possible to control the central control unit 11 to inject gas or liquid (e.g., air or water) into the bag portion 13a to expand (expand) it, and to control the gas or liquid to discharge from the bag portion 13a to contract it.

[0028] The inner plug 10A installed in the upper end 3a of the monopile 3 is further provided with a pressure adjustment mechanism 14. With the upper end 3a of the monopile 3 closed by the inner plug 10A, the pressure adjustment mechanism 14 is used to inject and exhaust air into and from the inner hollow portion of the monopile 3 located below the inner plug 10A, thereby adjusting the internal pressure of the inner hollow portion of the monopile 3 located below the inner plug 10A. In this embodiment, the central control unit 11 is remotely operated by a controller, so that the injection and exhaust of gas by the inner plug 10A can be controlled.

[0029] An inner plug 10A installed in the upper end 3a of the monopile 3 and an inner plug 10B installed in the lower end 3b of the monopile 3 are connected by a connecting member 15. The connecting member 15 may be, for example, a string-like member or a rod-like member. The inner plug 10B installed in the lower end 3b of the monopile 3 becomes smaller in diameter than the upper end 3a of the monopile 3 when the multiple arms 12 are shortened and the expansion / contraction section 13 is contracted.

[0030] When installing the inner plugs 10A, 10B in the monopile 3, as illustrated in Figure 3(b), the multiple arms 12 constituting each of the inner plugs 10A, 10B are shortened and the expansion / contraction sections 13 are contracted. Then, by inserting the inner plugs 10A, 10B, which are connected by the connecting members 15, into the inner hollow section of the monopile 3 from the upper opening or the lower opening of the monopile 3, each of the inner plugs 10A, 10B can be placed in the inner hollow section of the monopile 3.

[0031] Thereafter, as illustrated in Fig. 3(c), the multiple arms 12 constituting each of the inner plugs 10A, 10B are extended and the tip portions (contact portions) of each of the arms 12 are pressed against the inner surface of the monopile 3, thereby fixing the inner plugs 10A, 10B to the monopile 3. When removing the inner plugs 10A, 10B from the monopile 3, as illustrated in Fig. 3(b), the multiple arms 12 constituting each of the inner plugs 10A, 10B are shortened and the expansion / contraction portions 13 are contracted. Then, each of the inner plugs 10A, 10B can be taken out of the monopile 3 through the upper opening of the monopile 3.

[0032] The erection device 30 will be described in detail below. Figures 4 to 7 show a state in which the lower part of the monopile 3, which has been laid sideways using the multi-axle carriage 25, is set on the erection device 30 and the load of the lower part of the laid sideways monopile 3 is supported by the erection device 30. The erection device 30 is composed of a support frame 31 that supports the lower part of the monopile 3, a base frame 35 installed at the stern of the transport barge 20, and a rotation mechanism 36 that rotatably connects the support frame 31 to the base frame 35. The support frame 31, the base frame 35, and the rotation mechanism 36 are each mainly made of metal.

[0033] As illustrated in Figures 5 to 7, the support frame 31 of this embodiment has side support parts 32 that support the side surfaces (outer peripheral surfaces) of the lower part of the monopile 3 when it is laid on its side, lower end support parts 33 that support the lower end of the monopile 3, and connecting parts 34 that connect the side support parts 32 and the lower end support parts 33. The side support parts 32 are formed in a substantially arc shape so as to fit along the side surfaces of the monopile 3. In this embodiment, contact members 32a that come into contact with the side surfaces of the monopile 3 are disposed at multiple locations on the side support parts 32. It is preferable to provide a rubber or resin member that acts as an anti-slip material on the inner surfaces (tip surfaces of the contact members 32a) of the side support parts 32 that come into contact with the side surfaces of the monopile 3. Note that the side support parts 32 may also be configured without multiple contact members 32a.

[0034] Connecting portions 34 are provided on both sides of the monopile 3, extending in the lengthwise direction of the transport barge 20 along the monopile 3. The side support portions 32 extend in the widthwise direction of the transport barge 20 so as to cross the pair of connecting portions 34. The side support portions 32 are joined to the pair of connecting portions 34 at midpoints in the longitudinal direction. The lower end support portions 33 are provided at the ends of the pair of connecting portions 34 in the longitudinal direction. The lower end support portions 33 extend in the widthwise direction of the transport barge 20 so as to cross the pair of connecting portions 34. As illustrated in Figure 6, the lower end support portions 33 are arranged so as to cross the center of the lower end of the monopile 3.

[0035] 5, in this embodiment, an opening / closing mechanism 33a is provided in the lower end support portion 33. Specifically, the lower end support portion 33 is composed of a pair of plate-like members, and an end of each plate-like member is rotatably connected to an end of the connecting portion 34 via the opening / closing mechanism 33a. When the pair of plate-like members constituting the lower end support portion 33 is rotated by the opening / closing mechanism 33a to extend in the longitudinal direction of the connecting portion 34, the lower end support portion 33 is opened, and the support state of the lower end of the monopile 3 by the lower end support portion 33 is released.

[0036] In this embodiment, base frames 35 are provided on both sides of the support frame 31 (connecting portion 34). The lower ends of the pair of base frames 35 are fixed to the barge main body 21 of the transport barge 20. The pair of base frames 35 extend to a position protruding outward from the stern of the barge main body 21. A rotation shaft 36a constituting a rotation mechanism 36 is provided at the end of the base frame 35 located above the water surface of the water area, and the support frame 31 (connecting portion 34) is rotatably connected to the end of the base frame 35 via the rotation shaft 36a. The side support portion 32 and the rotation shaft 36a are arranged at the same position in the longitudinal direction of the connecting portion 34. The side support portion 32, the lower end support portion 33, and the rotation shaft 36a are arranged outside the stern of the barge main body 21. In this embodiment, the connecting part 34 is configured to be movable relative to the rotation mechanism 36 in the longitudinal direction of the connecting part 34, and by changing the connection position of the connecting part 34 relative to the rotation mechanism 36, the stroke (length) from the rotation mechanism 36 (rotation axis 36a) to the longitudinal end of the connecting part 34 (lower end support part 33) can be changed.

[0037] In this embodiment, the rotation mechanism 36 is provided with a drive unit 36b that drives the support frame 31 to rotate relative to the base frame 35. The drive unit 36b can be configured, for example, by a hydraulic cylinder. In this embodiment, one end of the hydraulic cylinder that configures the drive unit 36b is rotatably connected to the base frame 35, and the other end of the hydraulic cylinder is rotatably connected to the support frame 31. The support frame 31 is driven to rotate relative to the base frame 35 by extending and retracting the drive unit 36b (hydraulic cylinder).

[0038] Next, details of the concrete driving auxiliary device 50 will be described. As illustrated in Figures 12 to 14, the concrete driving auxiliary device 50 includes a pile guide unit 51 that can restrain horizontal movement of the monopile 3, and a movement mechanism 52 that moves the pile guide unit 51 relative to the barge body 41 of the SEP vessel 40. As illustrated in Figures 12 and 13, the pile guide unit 51 of this embodiment is provided with a pair of opening / closing units 51a at the front, and the front units (opening / closing units 51a) of the pile guide unit 51 can be opened and closed by a switching mechanism 51b.

[0039] As illustrated in Figures 13 and 14, when the opening / closing part 51a is closed, the pile guide part 51 is cylindrical. When the monopile 3 is inserted into the pile guide part 51 in the closed state, the horizontal movement of the monopile 3 relative to the pile guide part 51 is constrained (controlled). As illustrated in Figure 12, when the opening / closing part 51a is opened by the switching mechanism 51b, the monopile 3 is released from the constraint of the pile guide part 51.

[0040] In this embodiment, a plurality of advancing and retreating sections 51c are provided on the pile guide section 51. Each of the advancing and retreating sections 51c is configured to be able to move toward and retreat from the center of the cylindrical pile guide section 51. As illustrated in FIG. 13, when the monopile 3 is inserted into the pile guide section 51 with its opening / closing section 51a closed, and the tip of each of the advancing and retreating sections 51c is brought into contact with the side of the monopile 3, the monopile 3 is gripped by the pile guide section 51 (the plurality of advancing and retreating sections 51c). When the tip of each of the advancing and retreating sections 51c is moved away from the side of the monopile 3, the gripping state by the pile guide section 51 is released, and horizontal movement of the monopile 3 relative to the pile guide section 51 is restricted, but vertical movement of the monopile 3 relative to the pile guide section 51 is not restricted.

[0041] The moving mechanism 52 in this embodiment is composed of a forward / backward moving mechanism 53 that moves the pile guide section 51 in the longitudinal direction (X direction) of the SEP vessel 40, an up / down moving mechanism 55 that moves the pile guide section 51 in the vertical direction (Z direction), and a left / right moving mechanism 60 that moves the pile guide section 51 in the width direction (Y direction) of the SEP vessel 40.

[0042] The forward / backward movement mechanism 53 is composed of an actuator 54 extending in the X direction. The actuator 54 is composed of, for example, a hydraulic cylinder or a pneumatic cylinder in which a rod 54b is extendable (movable forward and backward) relative to a cylinder 54a. The rear part of the pile guide part 51 is connected to the front end part of the actuator 54 (rod 54b).

[0043] The vertical movement mechanism 55 includes a rotating unit 56 to which the rear of the actuator 54 is fixed, a lifting unit 57 to which the rotating unit 56 is rotatably connected, a support unit 58 that supports the lifting unit 57 so that it can move up and down in the vertical direction, and a lifting guide 59 that guides the lifting unit 57's lifting and lowering movement relative to the support unit 58. The horizontal movement mechanism 60 includes a rail 61 that extends in the Y direction and is laid at the stern of the barge main body 41 of the SEP vessel 40, and a movable base 62 that can move in the Y direction on the rail 61. The support unit 58 is fixed on top of the movable base 62. In this embodiment, the support unit 58 is erected in the center of the movable base 62, and the lifting guide 59, lifting unit 57, rotating unit 56, and actuator 54 are disposed on both sides of the support unit 58, respectively.

[0044] 14 and 18, in this embodiment, the actuator 54 can be switched between a state in which it extends in the Z direction and a state in which it extends in the X direction by rotating the rotating part 56 relative to the lifting part 57. As shown in FIG. 18, when the driving auxiliary device 50 is not in use, the length of projection of the rod 54b relative to the cylinder 54a of the actuator 54 is shortened to set the actuator 54 in a state in which it extends in the Z direction, thereby setting the pile guide part 51 in a state in which it is positioned near the stern part above the barge main body 41 (stored state).

[0045] As shown in FIG. 14, when the driving auxiliary device 50 is used for the work of setting the monopile 3 on the waterbed SB or for driving the monopile 3, the rotating unit 56 is rotated relative to the lifting unit 57 to extend the actuator 54 in the X direction. In this state, the pile guide unit 51 can be moved in the X direction by changing the projection length of the rod 54b relative to the cylinder 54a of the actuator 54. Furthermore, the pile guide unit 51 can be moved in the Z direction relative to the barge main body 41 by raising and lowering the lifting unit 57 relative to the support unit 58. Furthermore, the pile guide unit 51 can be moved in the Y direction relative to the barge main body 41 by moving the movable base 62 in the Y direction along the rail 61. The opening and closing operation of the opening / closing unit 51a by the switching mechanism 51b and the movement of the pile guide unit 51 by the front-rear movement mechanism 53, the up-down movement mechanism 55, and the left-right movement mechanism 60 can be remotely controlled by a controller. The concrete pouring auxiliary device 50 may also be configured without the relatively large moving mechanism 52 as illustrated in this embodiment.

[0046] Next, the specific work procedure of this construction method will be explained.

[0047] As illustrated in FIG. 2 , an SEP vessel 40 equipped with a crane 43 and a driving support device 50 is parked in a water area where a monopile foundation 2 is to be constructed, in a jacked-up state with its lifting legs 42 resting on the bottom of the water SB. When parking the SEP vessel 40, each of the lifting legs 42 is moved downward relative to a barge body 41 floating in the water area, so that the bottom ends of each of the lifting legs 42 rest on the bottom of the water SB. From this state, the barge body 41 is moved upward relative to each of the lifting legs 42, moving the barge body 41 to a position higher than the water surface level WL1 of the water area and supporting the barge body 41 in midair with the lifting legs 42. By raising the barge body 41 to a height out of the reach of waves, the barge body 41 is no longer affected by waves.

[0048] The pile guide section 51 of the auxiliary driving device 50 is placed at the planned driving position of the monopile 3. The horizontal position of the pile guide section 51 can be adjusted by the forward / backward movement mechanism 53 and the left / right movement mechanism 60. The opening / closing section 51a of the pile guide section 51 is set in the open position. The driving device 45 is loaded onto the barge body 41 of the SEP vessel 40, and a hoisting device 44 that can be connected to the upper end 3a of the monopile 3 is attached to the wire rope 43a of the crane 43 of the SEP vessel 40.

[0049] Then, the transport barge 20 carrying the monopile 3 laid sideways is moored in a water area near the SEP vessel 40. More specifically, the transport barge 20 transports the monopile 3 and the multi-axle carriage 25 to the construction water area, and the transport barge 20 is moored to the water bottom ground SB using mooring means 22 such as mooring lines and anchors. If there is an offshore structure around the construction water area, the transport barge 20 may be moored to the offshore structure. In this embodiment, the transport barge 20 is further kept at a fixed position by controlling the multiple thrusters 23a provided on the barge main body 21 using a maneuvering equipment 23 mounted on the transport barge 20.

[0050] In this embodiment, a plurality of movable support platforms 24 are provided on the barge body 21 of the transport barge 20. By placing the monopile 3 on the plurality of support platforms 24, the monopile 3 is positioned at a position higher than the upper surface of the barge body 21. The monopile 3 is positioned so that its lower end 3b faces the side where the erection device 30 is located.

[0051] As in this embodiment, when the concrete pouring auxiliary device 50 is mounted on the stern of the SEP vessel 40 and the erecting device 30 is mounted on the stern of the transport barge 20, the SEP vessel 40 and the transport barge 20 are arranged facing the same direction. The transport barge 20 should be arranged so that the stern end of the barge main body 41 of the SEP vessel 40 and the stern end of the barge main body 21 of the transport barge 20 are in roughly the same position in the lengthwise direction (X direction) of the SEP vessel 40. In other words, the SEP vessel 40 and the transport barge 20 should be arranged so that the erecting device 30 is lined up alongside the concrete pouring auxiliary device 50.

[0052] As illustrated in Figures 2 and 3, an inner plug 10 is installed inside the monopile 3 loaded on the transport barge 20. In this embodiment, an inner plug 10 (10A, 10B) is installed inside each of the upper end 3a and lower end 3b of the monopile 3. As illustrated in Figure 3(c), the expansion / contraction portion 13 of each inner plug 10 (10A, 10B) is in a contracted state, and a gap is provided between the expansion / contraction portion 13 and the inner peripheral surface of the monopile 3, i.e., the inner hollow portion of the monopile 3 is left open.

[0053] Next, as illustrated in FIGS. 4 to 7 , the lower part of the monopile 3 lying laterally is set on the erection device 30 using the multi-axle carriage 25, and the load of the lower part of the monopile 3 lying laterally is supported by the erection device 30. More specifically, in this embodiment, the multi-axle carriage 25 is moved between the lower side of the monopile 3 and the upper surface of the barge main body 21, and the monopile 3 is released from the support state of the multiple supports 24, so that the monopile 3 is placed on the multi-axle carriage 25. Then, with the monopile 3 supported by the multi-axle carriage 25, the multi-axle carriage 25 is moved toward the erection device 30, so that the lower part of the monopile 3 is placed on the support frame 31 of the erection device 30. The side surfaces of the lower part of the monopile 3 are supported by the side support parts 32 of the support frame 31, and the lower end of the monopile 3 is brought into contact with the lower end support part 33 of the support frame 31.

[0054] Next, with the monopile 3 supported by the multi-axle cart 25, the hoisting device 44 attached to the wire rope 43a of the crane 43 is connected to the upper end 3a of the monopile 3. Then, the wire rope 43a of the crane 43 is tensioned, and the load on the upper part of the monopile 3 is suspended by the crane 43. Note that the operation of connecting the hoisting device 44 to the upper end 3a of the monopile 3 may be performed, for example, when the monopile 3 is placed on multiple support bases 24.

[0055] 7 to 9, with the load at the bottom of the monopile 3 lying sideways supported by the erection device 30, the upper end 3a of the monopile 3 is lifted upward by the crane 43. Then, the monopile 3 is rotated together with the support frame 31, with the rotation mechanism 36 (rotation shaft 36a) of the erection device 30 as a fulcrum, so that the lower end of the monopile 3 is submerged in the water area near the transport barge 20 and erected. The multi-axle cart 25 should be retracted immediately before the upper end 3a of the monopile 3 is lifted upward by the crane 43.

[0056] During the process of erecting the monopile 3, the lower end 3b of the monopile 3 and a part of the support frame 31 located on the lower end side of the monopile 3 (part of the connecting part 34 and the lower end support part 33) become submerged. The upper part of the monopile 3 becomes positioned above the water surface level WL1 of the water area.

[0057] In this embodiment, when the upper end 3a of the monopile 3 is lifted by the crane 43 above the erection device 30, the support frame 31 is rotationally driven by the drive unit 36b provided in the rotation mechanism 36. Even if the rotation mechanism 36 is not provided with the drive unit 36b, when the upper end 3a of the monopile 3 is lifted by the crane 43 above the erection device 30, the support frame 31 will naturally rotate following the monopile 3. The work of erecting the monopile 3 is preferably carried out by gradually rotating the monopile 3 and the support frame 31 of the erection device 30 at a relatively slow speed.

[0058] When the monopile 3 is being erected, its load is supported by the erection device 30 and the crane 43. When the lower end 3b of the monopile 3 is submerged, buoyancy acts on the monopile 3, reducing the load on the erection device 30 and the crane 43. Therefore, with this construction method, even if the weight of the monopile 3 exceeds the maximum lifting load of the crane 43 of the SEP vessel 40, it is possible to erect the monopile 3 by using the erection device 30. Specifically, even if the monopile 3 weighs, for example, 1,000 tons or more and 2,000 tons or less, it can be erected using the crane 43 of a medium-sized SEP vessel 40 whose maximum lifting load is, for example, 1,200 tons or more and 1,600 tons or less.

[0059] As shown in Figure 8, the inner plug 10B installed in the lower end 3b of the monopile 3 is positioned so that when the monopile 3 is erected, it is located below the water surface level WL1 of the water area. During the process of erecting the monopile 3, water from the water area flows into the inner space of the lower end 3b of the monopile 3. The magnitude of the buoyancy acting on the monopile 3 during the process of erecting the monopile 3 and when the monopile 3 is erected depends on the water level WL2 in the inner space of the monopile 3.

[0060] Therefore, the magnitude of buoyancy acting on the monopile 3 can be adjusted by adjusting the water level WL2 in the inner hollow portion of the monopile 3. In this embodiment, the water level WL2 in the inner hollow portion of the monopile 3 is adjusted using the inner plugs 10 (10A, 10B) installed in the monopile 3, thereby adjusting the magnitude of buoyancy acting on the monopile 3. In Figure 8, the water present in the inner hollow portion of the monopile 3 is visualized by diagonal lines.

[0061] When the expansion / contraction portion 13 of the inner plug 10B installed inside the lower end 3b of the monopile 3 is contracted to open the inner plug 10B, water can pass through the inner plug 10B. When the expansion / contraction portion 13 of the inner plug 10B is expanded to close the inner plug 10B, water cannot pass through the inner plug 10B. Therefore, by opening and closing the inner plug 10B to adjust the amount of water flowing above the inner plug 10B, the water level WL2 in the inner space of the monopile 3 can be adjusted. Furthermore, by adjusting the degree of expansion / contraction of the expansion / contraction portion 13 of the inner plug 10B to adjust the amount of water passing through the inner plug 10B per unit time, the amount of change in buoyancy acting on the monopile 3 can also be adjusted.

[0062] In this embodiment, when the expansion / contraction section 13 of the inner plug 10A installed in the upper end 3a of the monopile 3 is contracted and the inner plug 10A is opened, air in the inner space located below the inner plug 10A can pass through the inner plug 10A. Therefore, when both the upper and lower inner plugs 10A and 10B are open, water from the body of water can easily flow into the inner space above the inner plug 10B.

[0063] When the expansion / contraction section 13 of the inner plug 10A is expanded and the inner plug 10A is closed, air in the inner space below the inner plug 10A of the monopile 3 cannot pass through the inner plug 10A. The inner space below the inner plug 10A becomes a closed space between the inner plug 10A and the water surface in the inner space. Therefore, it is relatively difficult for water from the water body to flow into the inner space above the inner plug 10B.

[0064] Furthermore, with the inner plug 10A closed, the pressure adjustment mechanism 14 is used to inject and discharge air into and from the hollow space located below the inner plug 10A, thereby adjusting the internal pressure of the hollow space located below the inner plug 10A, thereby making it possible to adjust the amount of water per unit time flowing into the hollow space of the monopile 3 and the water level WL2 in the hollow space of the monopile 3. Therefore, by opening and closing the inner plug 10A and operating the pressure adjustment mechanism 14, the magnitude of the buoyancy acting on the monopile 3 and the amount of change in the buoyancy acting on the monopile 3 can be adjusted.

[0065] After the monopile 3 has been erected, the weight of the monopile 3 is supported by the buoyancy acting on the monopile 3 and the crane 43. During the process of erecting the monopile 3, the water level WL2 in the inner hollow portion of the monopile 3 is adjusted so that the load on the crane 43 when the monopile 3 is separated from the erection device 30 is below the maximum lifting load of the crane 43. As described above, the water level WL2 in the inner hollow portion of the monopile 3 is adjusted by opening and closing the inner plugs 10 (10A, 10B) installed inside the monopile 3 and operating the pressure adjustment mechanism 14.

[0066] As illustrated in Figure 8, the water level WL2 in the hollow portion of the monopile 3 in an upright state can be adjusted as appropriate depending on the weight of the monopile 3 and the maximum lifting load of the crane 43. However, it is preferable to operate the inner plugs 10 (10A, 10B) so that the water level WL2 in the hollow portion of the monopile 3 is lower than the water surface level WL1 in the water area. The lower the water level WL2 in the hollow portion of the monopile 3 and the greater the buoyancy acting on the monopile 3, the more the load supported by the crane 43 can be reduced. However, reducing the buoyancy acting on the monopile 3 stabilizes the posture of the monopile 3 when it is moved in the water area by the crane 43, and reduces the swaying of the monopile 3. Therefore, it is preferable to adjust the magnitude of the buoyancy acting on the monopile 3, taking into consideration the maximum lifting load of the crane 43 and the weight of the monopile 3. By adjusting the stroke (length) from the rotation mechanism 36 (rotation axis 36a) to the longitudinal end (lower end support portion 33) of the connecting portion 34, the buoyancy acting on the monopile 3 can also be adjusted without changing the water level WL2 in the inner space of the monopile 3.

[0067] The magnitude of the buoyancy acting on the monopile 3 may be adjusted so that the lifting force of the crane 43 (the load supported by the crane 43) is, for example, 300 to 600 tons, more preferably 400 to 500 tons. Specifically, the vertical distance (height) from the lower end of the monopile 3 to the water level WL2 in the hollow portion of the monopile 3 may be adjusted to, for example, 5 to 30% of the length (height) of the monopile 3, more preferably 10 to 25%. More specifically, although it depends on the length of the monopile 3, the vertical distance may be adjusted to, for example, 3 m to 30 m, more preferably 5 m to 25 m.

[0068] After the monopile 3 has been erected, it is possible to lower the water level WL2 in the inner hollow portion of the monopile 3 by increasing the internal pressure in the inner hollow portion of the monopile 3 using the pressure adjustment mechanism 14 of the inner plug 10A, but it is relatively difficult to lower the water level WL2 in the inner hollow portion of the monopile 3 after the monopile 3 has been erected. Therefore, in the process of rotating the monopile 3 using the erection device 30, it is advisable to operate the inner plug 10 (10A, 10B) so that the water level WL2 in the inner hollow portion after the monopile 3 has been erected is lower than the water level WL2 in the inner hollow portion that is set when the monopile 3 is separated from the erection device 30.

[0069] Specifically, if the monopile 3 is rotated with the upper and lower inner plugs 10A, 10B completely closed, a relatively large water pressure will be applied to the lower inner plug 10B, which may result in a large load being placed on the inner plug 10B. Therefore, it is advisable to keep the upper and lower inner plugs 10A, 10B in an open state when starting to rotate the monopile 3.

[0070] Furthermore, if the upper and lower inner plugs 10A, 10B are left open until the monopile 3 is erected, there is a possibility that the water level WL2 in the hollow portion of the monopile 3 will be the same height as the water surface level WL1 of the water area. Therefore, it is advisable to gradually expand the expansion / contraction sections 13 of the upper and lower inner plugs 10A, 10B during the process of rotating the monopile 3, thereby adjusting the amount of water flowing into the hollow portion of the monopile 3, so that the water level WL2 in the hollow portion of the monopile 3 will be lower than the water surface level WL1 of the water area when the monopile 3 is erected. If the upper inner plug 10A is kept closed during the process of rotating the monopile 3, and the internal pressure in the hollow portion of the monopile 3 is adjusted by the pressure adjustment mechanism 14 of the inner plug 10A, the amount of water flowing into the hollow portion of the monopile 3 can be adjusted more accurately. In addition, before moving the monopile 3 away from the support frame 31, it is advisable to adjust the stroke (length) from the rotation mechanism 36 (rotation axis 36a) to the longitudinal end (lower end support portion 33) of the connecting portion 34, thereby adjusting the buoyancy acting on the monopile 3 without changing the water level WL2 in the inner space of the monopile 3.

[0071] After the monopile 3 has been erected, as shown in Fig. 10, the monopile 3 erected in the water area is moved by a crane 43 from the erecting device 30 to the pile guide part 51 of the driving auxiliary device 50 arranged outside the SEP vessel 40. While the monopile 3 is being moved, the lower end 3b of the monopile 3 is kept submerged.

[0072] In this embodiment, when the monopile 3 is erected, the side support parts 32 of the support frame 31 are disposed closer to the transport barge 20 than the monopile 3. Therefore, by using the crane 43 to move the erected monopile 3 in a direction away from the side support parts 32, the monopile 3 can be moved away from the erection device 30.

[0073] As in this embodiment, when an opening / closing mechanism 33a is provided on the lower end support portion 33 of the support frame 31 of the erection device 30, the opening / closing mechanism 33a can be remotely operated to open the lower end support portion 33, thereby releasing the support state of the lower end of the monopile 3 by the lower end support portion 33, making it easier to move the erected monopile 3 away from the erection device 30.

[0074] As shown in Figure 10, when moving the monopile 3 in a water area using the crane 43, it is advisable to close the inner plugs 10 (10A, 10B) and keep the water level WL2 in the hollow portion of the monopile 3 constant while moving it. Since the monopile 3 may tilt or sway due to the resistance of the water or the influence of waves while moving, it is advisable to move the monopile 3 gradually at a relatively slow speed using the crane 43 to prevent the tilting or swaying of the monopile 3 from becoming excessive.

[0075] As illustrated in Figures 11 and 12, after the monopile 3 is moved by the crane 43 to the position of the pile guide unit 51 of the driving auxiliary device 50, the switching mechanism 51b of the pile guide unit 51 is remotely operated to close the opening / closing unit 51a, as illustrated in Figures 12 to 15. Then, the monopile 3 is inserted into the cylindrical pile guide unit 51. Thereafter, as illustrated in Figure 16, while the pile guide unit 51 restrains the horizontal movement of the monopile 3, the crane 43 moves the monopile 3 downward until the monopile 3 lands on the waterbed SB. When moving the monopile 3 downward, it is advisable to gradually open the inner plugs 10 (10A, 10B) installed inside the monopile 3 to gradually flow water from the water body into the hollow space inside the monopile 3.

[0076] When the pile guide unit 51 is provided with a plurality of advancing and retracting sections 51c and is configured to be able to grip the monopile 3 as in this embodiment, the monopile 3 may be placed on the water bottom ground SB in the following procedure. As illustrated in Figures 12 to 15, when the opening / closing sections 51a of the pile guide unit 51 are closed, the tip ends of the advancing and retracting sections 51c are brought into contact with the side surfaces of the monopile 3, and the monopile 3 is gripped by the pile guide unit 51 (the plurality of advancing and retracting sections 51c). At this time, the pile guide unit 51 is positioned at a high position by the movement mechanism 52 (the up-down movement mechanism 55).

[0077] Thereafter, the inner plug 10 installed inside the monopile 3 is opened to allow water to flow into the hollow space inside the monopile 3. Next, as illustrated in FIG. 16 , with the monopile 3 held by the pile guide unit 51, the crane 43 moves the monopile 3 downward while reducing the lifting force of the crane 43, and the pile guide unit 51 holding the monopile 3 is also moved downward, so that the monopile 3 lands on the water bottom SB. In this embodiment, the pile guide unit 51 can be moved downward by moving the lifting unit 57 constituting the up-down movement mechanism 55 downward relative to the support unit 58. When the monopile 3 lands on the water bottom SB, the monopile 3 is slightly submerged (sinks) from the water bottom SB.

[0078] In this way, by moving the monopile 3 downward with the crane 43 while also moving the pile guide part 51 holding the monopile 3 downward, the pile guide part 51 can be moved downward in a very stable state. In addition, since the driving auxiliary device 50 supports part of the weight of the monopile 3, the load on the crane 43 when moving the monopile 3 downward can be reduced.

[0079] After the monopile 3 has landed on the water bottom SB, the connection between the upper end 3a of the monopile 3 and the hoisting device 44 of the crane 43 is released. Since the horizontal movement of the monopile 3 is restrained by the pile guide part 51, the monopile 3 remains in a state where it has sunk from the water bottom SB (a state where the lower end 3b is sunk into the water bottom SB and stands upright). The hoisting device 44 is removed from the wire rope 43a of the crane 43, and a driving device 45 is attached to the wire rope 43a of the crane 43. The inner plug 10 installed inside the monopile 3 is removed from the monopile 3.

[0080] The upper and lower inner plugs 10A, 10B installed inside the monopile 3 are connected by a connecting member 15. Therefore, as illustrated in Figure 3(b), when the multiple arms 12 constituting each inner plug 10A, 10B are shortened and the expansion / contraction section 13 is contracted, each inner plug 10A, 10B can be removed from the monopile 3 to the outside through the upper opening of the monopile 3.

[0081] Next, as illustrated in Figure 17, a driving device 45 is attached to the upper end 3a of the monopile 3. When the monopile 3 is being held by the pile guide parts 51, the advancing and retreating parts 51c are moved away from the monopile 3 to release the monopile 3 from being held by the pile guide parts 51. Then, while the horizontal movement of the monopile 3 is restrained by the pile guide parts 51, the monopile 3 is driven into the waterbed ground SB using the crane 43 and the driving device 45, thereby constructing the monopile foundation 2.

[0082] When the lower end 3b of the monopile 3 is inserted to a certain extent into the waterbed ground SB, the monopile 3 will be in a stable upright state, and therefore the restriction on the horizontal movement of the monopile 3 by the pile guide part 51 may be released once the driving work of the monopile 3 has progressed to a certain extent. In this embodiment, the restriction on the monopile 3 by the pile guide part 51 can be released by opening the opening / closing part 51a of the pile guide part 51 and moving the pile guide part 51 away from the monopile 3 using the front-rear moving mechanism 53.

[0083] As shown in Figure 18, the construction of the monopile foundation 2 is completed when the driving of the monopile 3 is completed. If multiple monopile foundations 2 are to be constructed next, the SEP vessel 40 is moved to the planned driving position for the next monopile 3 to be driven, and the SEP vessel 40 is stopped in a jacked-up state. Then, the transport barge 20 is moored near the SEP vessel 40. Thereafter, the monopile foundations 2 are constructed using the same work procedure.

[0084] As described above, in this construction method, the load of the lower portion 3b of the monopile 3 that is laid sideways and loaded on the transport barge 20 is supported by the erection device 30 provided on the transport barge 20. Then, the crane 43 of the SEP vessel 40, which is parked in a jacked-up state near the transport barge 20, lifts the upper end portion 3a of the monopile 3 above the erection device 30, and rotates the monopile 3 around the rotation mechanism 36 of the erection device 30 as a fulcrum.

[0085] This allows the monopile 3 to be erected while the load of the monopile 3 is supported by the crane 43 and the erection device 30 of the SEP vessel 40. Therefore, the load on the crane 43 of the SEP vessel 40 can be reduced, and even when constructing a large monopile foundation 2, it becomes possible to stably erect the monopile 3 using the crane 43 of a smaller SEP vessel 40 (medium-sized SEP vessel 40), which was not possible in the past.

[0086] Furthermore, by submerging the lower end 3b of the monopile 3 in the water area near the transport barge 20 and erecting it, buoyancy acts on the monopile 3, reducing the load of the monopile 3 on the crane 43 of the SEP vessel 40. Therefore, even when constructing a large monopile foundation 2, the crane 43 of a small-scale SEP vessel 40, which could not be used in the past, can be used to stably move the monopile 3 erected in the water area from the erecting device 30 to the pile guide section 51 that constitutes the driving auxiliary device 50 located outside the barge body 41 of the SEP vessel 40.

[0087] Thereafter, by moving the monopile 3 downward using the crane 43 while restraining the horizontal movement of the monopile 3 using the pile guide unit 51, the monopile 3 can be placed stably on the water bottom ground SB. Then, by driving the monopile 3 into the water bottom ground SB using the crane 43 and the driving device 45 while restraining the horizontal movement of the monopile 3 using the pile guide unit 51, the monopile 3 can be driven stably and accurately. Therefore, with this construction method, a large monopile foundation 2 can be constructed safely without using an appropriately large SEP vessel 40 or self-propelled work vessel.

[0088] As in this embodiment, the support frame 31 constituting the erection device 30 supports the lower side of the monopile 3 lying sideways and the lower end of the monopile 3, and the upper end 3a of the monopile 3 is lifted upward by the crane 43 toward the top of the erection device 30, and the support frame 31 is rotated using the rotation mechanism 36 as a fulcrum, which is advantageous for rotating the monopile 3 in a stable state.

[0089] Furthermore, if the support frame 31 is rotationally driven by the drive unit 36b provided in the rotation mechanism 36, the load on the crane 43 when rotating the monopile 3 can be reduced. Also, by controlling the rotation of the support frame 31 with the drive unit 36b, the monopile 3 can be rotated at a stable speed. Note that the drive unit 36b is not an essential component and can be provided as needed. For example, a damper can be provided in the rotation mechanism 36 instead of the drive unit 36b. Even when a damper is provided in the rotation mechanism 36, it is advantageous for rotating the monopile 3 at a stable speed.

[0090] As in this embodiment, if the inner plug 10 is installed in the hollow portion of the monopile 3 that is laid on its side and loaded on the transport barge 20, when the monopile 3 is erected in the water area near the transport barge 20, the water level WL2 in the hollow portion of the monopile 3 can be adjusted by opening and closing the inner plug 10, thereby adjusting the magnitude of the buoyancy acting on the monopile 3 with its lower end 3b submerged.

[0091] Furthermore, by providing inner plugs 10A, 10B at both the upper end 3a and the lower end 3b of the monopile 3, it becomes possible to precisely adjust the magnitude of buoyancy acting on the monopile 3 with the lower end 3b submerged. By providing a pressure adjustment mechanism 14 to the inner plug 10A installed inside the upper end 3a of the monopile 3, it becomes possible to more precisely adjust the magnitude of buoyancy acting on the monopile 3. For example, it is also possible to provide an inner plug 10 only on one side of the upper end 3a or the lower end 3b of the monopile 3. In this case too, it is possible to adjust the magnitude of buoyancy acting on the monopile 3 with a single inner plug 10.

[0092] Furthermore, if it is confirmed in advance by simulation or the like that the buoyancy acting on the monopile 3 is sufficient when the monopile 3 is erected without adjusting the water level WL2 in the inner hollow portion of the monopile 3, the monopile 3 can be configured without an inner plug 10.

[0093] In the operation of landing the monopile 3 on the water bottom ground SB, as in this embodiment, if the monopile 3 is moved downward by the crane 43 while the pile guide part 51 holding the monopile 3 is moved downward so that the monopile 3 is landed on the water bottom ground SB, this is advantageous for moving the monopile 3 downward in a stable manner. In this embodiment, the monopile 3 is held by the advancing and retreating part 51c provided on the pile guide part 51, but the structure of the pile guide part 51 holding the monopile 3 is not limited to this embodiment and can have various other configurations.

[0094] The pile guide unit 51 may have any configuration as long as it can restrain the horizontal movement of the monopile 3, and the pile guide unit 51 may also be configured without the function of gripping the monopile 3. Furthermore, for example, the concrete driving auxiliary device 50 may be configured without the up-and-down movement mechanism 55 that moves the pile guide unit 51 up and down. Even when the concrete driving auxiliary device 50 does not have the up-and-down movement mechanism 55 or when the movable distance of the up-and-down movement of the pile guide unit 51 by the up-and-down movement mechanism 55 is small, this construction method can safely perform the work of landing the monopile 3 on the water bottom ground SB, as exemplified in Figures 15 and 16. In the above-mentioned case, as illustrated in Figure 16, with the horizontal movement of the monopile 3 restrained by the pile guide unit 51, the buoyancy acting on the monopile 3 is adjusted to a magnitude required to land the monopile 3 on the water bottom ground SB, and the monopile 3 is moved downward by the crane 43 while adjusting the lifting force of the crane 43, thereby allowing the monopile 3 to land safely on the water bottom ground SB. In this case, the driving auxiliary device 50 does not need to have the function of supporting part of the weight of the monopile 3. The structures of the pile guide unit 51 and the moving mechanism 52 are not limited to the embodiment exemplified above, and various other configurations are also possible.

[0095] As in this embodiment, if the transport barge 20 is provided with a maneuvering device 23 and a thruster 23a to maintain the transport barge 20 in a fixed position, unintended movement or shaking of the transport barge 20 when erecting the monopile 3 can be suppressed, which is more advantageous for stably carrying out the erection work of the monopile 3. The maneuvering device 23 and the thruster 23a are not essential components and can be provided optionally as needed.

[0096] The inner plug 10 can also be configured, for example, as shown in (a) to (c) of Figure 19. The inner plug 10 of this embodiment differs from the inner plug 10 illustrated in Figure 3 in the configuration of the expansion / contraction section 13. The other configurations are the same as those of the inner plug 10 illustrated in Figure 3.

[0097] The expansion / contraction unit 13 in this embodiment is composed of an expandable / contractable fan section 13b. The fan section 13b is composed of a plurality of fan-shaped plate members. The plurality of plate members are connected below the central control unit 11 so that they can move relative to one another. The plurality of plate members are stacked in a spiral shape, and the central control unit 11 moves the plurality of plate members relative to one another, thereby enabling the expansion / contraction of the fan section 13b.

[0098] As illustrated in (a) of Figure 19, when the multiple arms 12 are retracted, the inner plug 10 can be moved relative to the monopile 3, and as illustrated in (b) and (c) of Figure 19, when the multiple arms 12 are extended, the inner plug 10 (central control unit 11) can be fixed to the monopile 3. As illustrated in (a) and (b) of Figure 19, when the fan section 13b is retracted, a gap is created between the fan section 13b and the inner circumferential surface of the monopile 3, and the inner hollow section of the monopile 3 is open.

[0099] 19(c), when the fan section 13b is expanded, the gap between the central control unit 11 and the inner peripheral surface of the monopile 3 is blocked by the fan section 13b, and the inner space of the monopile 3 is closed. By adjusting the degree of expansion or contraction of the fan section 13b, the size of the gap between the outer peripheral end of the fan section 13b and the inner peripheral surface of the monopile 3 can also be adjusted.

[0100] As described above, the expansion / contraction section 13 that constitutes the inner plug 10 is not limited to the embodiment exemplified above, and can have various other configurations. Also, in this embodiment, multiple arms 12 are provided as a means for fixing the inner plug 10 to the monopile 3, but the means for fixing the inner plug 10 to the monopile 3 is not limited to the embodiment exemplified above, and can have various other configurations. [Explanation of symbols]

[0101] 1. Monopile offshore wind power generation facility 2 Monopile foundation 3 Monopile 3a (of the monopile) upper end 3b Lower end (of monopile) 4. Wind power generation equipment 5. Tower 6 Nacelle hub 7 Blades 10 Inner plug 10A Inner plug (installed inside the top of the monopile) 10B Inner plug (installed inside the bottom of the monopile) 11 Central Control Unit 12 Arm 13. Expansion / contraction section 13a Bag part 13b Fan section 14 Pressure adjustment mechanism 15 Connecting member 20 Transport barge 21 Barge body 22 Mooring means 23 Navigation equipment 23a Thruster 24 Support stand 25 Multi-axle trolley 30 Standing device 31 Support frame 32 Side support part 32a abutting member 33 Lower end support part 33a Opening / closing mechanism 34 Connecting part 35 Base frame 36 Rotation mechanism 36a Rotation axis 36b Drive unit 40 Self-elevating platform (SEP) 41 Barge body 42 Lifting legs 43 Crane 43a Wire Rope 44 Hanging equipment 45 Concrete pouring device 50 Concrete pouring auxiliary device 51 Pile guide section 51a Opening / closing part 51b Switching mechanism 51c Advancement and retreat section 52 Moving mechanism 53 Back and forth movement mechanism 54 Actuator 54a cylinder 54b Rod 55 Up and down movement mechanism 56 Rotating part 57 Lifting section 58 Support part 59 Lifting guide 60 Left and right movement mechanism 61 Rail 62 Movable platform SB underwater ground WL1 Water surface position of water body WL2 Water level in the hollow part of the monopile

Claims

1. A construction method for a monopile foundation that constitutes a monopile offshore wind power generation facility, using a self-lifting barge equipped with a crane and a casting auxiliary device, and a transport barge equipped with an erection device, The self-elevating barge is parked in the water area where the monopile foundation is to be constructed, in a jacked-up state with its lifting legs resting on the bottom of the water, and the transport barge loaded with the monopiles that make up the monopile foundation and are laid down sideways is moored in the water area near the self-elevating barge. With the load of the lower part of the monopile lying sideways supported by the erection device, the upper end of the monopile is lifted by the crane toward above the erection device, and the monopile is rotated using the rotation mechanism of the erection device as a fulcrum, thereby submerging the lower end of the monopile in the waters near the transport barge and erecting it; The monopile erected in the water area is moved from the erection device to the pile guide part constituting the driving auxiliary device arranged outside the self-lifting barge using the crane, While the pile guide portion restrains the horizontal movement of the monopile, the crane moves the monopile downward to land the monopile on the bottom of the water. A construction method for a monopile foundation, characterized in that the monopile foundation is constructed by using the crane and driving device to drive the monopile into the waterbed while restraining the horizontal movement of the monopile with the pile guide section.

2. A construction method for a monopile foundation as described in claim 1, wherein the upper part of the monopile is lifted upward by the crane while the support frame constituting the erection device supports the side of the lower part of the monopile lying sideways and the lower end of the monopile, and the monopile is rotated by rotating the support frame around the rotation mechanism as a fulcrum.

3. 3. The method for constructing a monopile foundation according to claim 2, wherein the support frame is rotationally driven by a drive unit provided in the rotation mechanism.

4. A monopile foundation construction method as described in claim 1 or 2, in which an inner plug is installed in the hollow portion of the monopile that is laid sideways on the transport barge, and when the lower end of the monopile is submerged in water near the transport barge and erected, the water level in the hollow portion of the monopile is adjusted by opening and closing the inner plug, thereby adjusting the magnitude of buoyancy acting on the monopile.

5. 3. A monopile foundation construction method as described in claim 1 or 2, wherein, in the work of landing the monopile on the bottom of the water, the monopile is moved downward by the crane while the pile guide part holding the monopile is moved downward to land the monopile on the bottom of the water.

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