Construction method

Abstract

To provide a construction method capable of reducing the construction period when driving a monopile into the sea by hoisting the same using two crane ships.SOLUTION: The construction method is a method of installing a monopile MP by hanging using a first crane C1 of a first ship S1 and a second crane C2 of a second ship S2. The method includes: a double-hanging step of hanging a monopile MP using the first crane C1 and the second crane C2; a lifting step of lifting one end of the monopile MP with the first crane C1 so that the monopile MP tube axis is aligned vertically; and a driving step of attaching a pile driver hanged by the second crane C2 onto one end and driving the monopile MP.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a construction method.

Background Art

[0002] Conventionally, monopiles have been lifted by two crane vessels. Patent Document 1 discloses lifting a monopile steel pipe pile using a first crawler crane for driving a foundation pile and a second crawler crane for transporting the pile, lifting the monopile steel pipe pile with the axis parallel to the vertical direction by the first crawler crane, and starting driving the monopile steel pipe pile with a pile driving device attached to the first crawler crane for driving a foundation pile.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in Patent Document 1, after the monopile steel pipe pile is lifted with the axis parallel to the vertical direction by the first crawler crane, the same first crawler crane drives the monopile steel pipe pile with a pile driving device. Therefore, after the monopile steel pipe pile is lifted with the axis parallel to the vertical direction, it is necessary to once remove the first crawler crane from the monopile steel pipe pile and attach a pile driving device to the first crawler crane. Therefore, during the operation, since the monopile steel pipe pile is in a standby state, there is room for shortening the construction period.

[0005] The present disclosure has been made in view of the above-described circumstances, and an object thereof is to provide a construction method capable of shortening the construction period when a monopile is lifted by two crane ships and driven in.

Means for Solving the Problems

[0006] <1>The construction method according to Embodiment 1 of the present disclosure is a construction method for lifting a monopile using a first crane of a first ship and a second crane of a second ship, the method including: a lifting step of lifting the monopile with the first crane and the second crane; a lifting step of lifting one end of the monopile with the first crane so that the pipe axis of the monopile is along the vertical direction; and a driving step of disposing a pile driver suspended by the second crane at one end of the monopile and driving the monopile.

Effects of the Invention

[0007] According to the present disclosure, it is possible to provide a construction method capable of shortening the construction period when a monopile is lifted by two crane ships and driven in.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Mode for Carrying Out the Invention

[0009] Hereinafter, with reference to the drawings, a construction method according to an embodiment of the present disclosure will be described. The construction method according to the present embodiment is a construction method for driving a monopile into the seabed ground. The monopile is, for example, a steel pipe for supporting an offshore windmill (not shown) by being connected to the lower end of the offshore windmill. The monopile is connected to the lower end of the offshore windmill via, for example, a transition piece (not shown). That is, the monopile supports the offshore windmill via, for example, a transition piece. Alternatively, the monopile may be directly connected to the lower end of the offshore windmill without passing through the transition piece. That is, the monopile may support the offshore windmill without passing through the transition piece. The monopile is, for example, a cylindrical member. Hereinafter, in the present embodiment, the monopile will be described as a cylindrical member. Alternatively, the monopile may be, for example, a square tubular member. Accordingly, each configuration described later may be appropriately corresponded.

[0010] FIG. 1 is a plan view of the lifting process according to the embodiment. FIG. 2 is a side view of the lifting process according to the embodiment. FIG. 3 is a cross-sectional view taken along the III-III direction of FIG. 2. FIG. 4 is a view taken in the direction of arrow IV of FIG. 2. In this embodiment, as shown in FIG. 1, a first ship S1 and a second ship S2 are used for the construction of the monopile MP. The first ship S1 is a ship having a lifting capacity. That is, the first ship S1 is, for example, a crane ship (floating crane) including a fixed crane ship or a revolving crane ship. The second ship S2 is, for example, a revolving crane ship. In this embodiment, a crane ship refers to a ship equipped with a crane. A fixed crane ship refers to a ship equipped with a crane in which the mounted crane cannot revolve. A revolving crane ship refers to a ship equipped with a crane in which the mounted crane can revolve. As shown in FIG. 1, the first ship S1 has a first crane C1. The second ship S2 has a second crane C2. In this embodiment, the first crane C1 may be able to revolve or may not be able to revolve. In this embodiment, the second crane C2 is able to revolve. In this embodiment, when driving the monopile MP into the seabed ground with a hammer, as shown in FIGS. 1 to 4, two cranes are used. That is, for example, as shown in FIG. 2, the monopile MP is hoisted by using the first crane C1 of the first ship S1 and the second crane C2 of the second ship S2. This enables handling of relatively large monopiles MP. In this embodiment, the lifting load of the first crane C1 is equal to or greater than the lifting load of the second crane C2. Further, when the monopile MP is hoisted by the first crane C1 and the second crane C2, it is preferable to keep the distance between the first crane C1 and the second crane C2, that is, the distance between the first ship S1 and the second ship S2 constant, so that the monopile MP can be stably hoisted. For this reason, as shown in FIG. 1, it is preferable to arrange a bar B between the first ship S1 and the second ship S2. Arranging the bar B between the first ship S1 and the second ship S2 in this way is particularly suitable, for example, when the length of the monopile MP is relatively long.

[0011] In this embodiment, as shown in FIGS. 2 and 3, one end of the monopile MP is suspended by the first crane C1. Also, as shown in FIGS. 2 and 4, the other end of the monopile MP is suspended by the second crane C2. More specifically, the first crane C1 suspends one end of the monopile MP by suspending a gripping tool BH that grips one end of the monopile MP. Also, the second crane C2 suspends the other end of the monopile MP by suspending a suspension stand HF that supports the vicinity of the other end of the monopile MP. In this embodiment, the vicinity of the other end of the monopile MP refers to, for example, a region of 20% of the length of the monopile MP from the other end of the monopile MP. In this case, when the monopile MP is suspended, the bending moment acting on the monopile MP can be suppressed. Alternatively, the vicinity of the other end of the monopile MP may be a region of 10% of the length of the monopile MP from the other end of the monopile MP. In this case, when the monopile MP is suspended, the monopile MP can be stably suspended by the first ship S1 and the second ship S2. Details of the gripping tool BH and the suspension stand HF will be described below.

[0012] (Regarding the gripping tool) The gripping tool BH is attached to one end of the monopile MP. The gripping tool BH is suspended by the first crane C1. As shown in FIG. 2, the gripping tool BH has a gripping portion BHa that grips one end of the monopile MP so as to sandwich it from the outside. The gripping tool BH is attached to one end of the monopile MP by the gripping portion BHa. In this embodiment, the gripping tool BH is a known vibrohammer. The gripping tool BH, which is a vibrohammer, penetrates the other end of the monopile MP into the seabed by vibrating one end of the monopile MP. That is, the gripping tool BH is first used to connect one end of the monopile MP and the wire of the first crane C1 when the monopile MP is suspended by the first crane C1 and the second crane C2. Then, after the monopile MP is erected on the ocean, the gripping tool BH vibrates one end of the monopile MP. By doing this, the other end of the monopile MP is penetrated into the seabed ground.

[0013] (Regarding the suspension pedestal) FIG. 5 is an enlarged view of the suspension pedestal HF. As shown in FIG. 2, the suspension pedestal HF is attached near the other end of the monopile MP. As shown in FIG. 4, the suspension pedestal HF is suspended by the second crane C2. As shown in FIG. 5, the suspension pedestal HF has a substantially U-shaped cross section. In the present embodiment, the substantially U-shaped means a shape including a bottom extending in an arbitrary direction and side portions extending from both ends of the bottom in a direction intersecting the arbitrary direction. As shown in FIG. 5, the suspension pedestal HF includes a bottom HFa and side portions HFb. The suspension pedestal HF forms an opening HFc by the bottom HFa and the side portions HFb. Shackles Sh are provided at the ends of the side portions HFb on the side not connected to the bottom HFa, as shown in FIG. 5. Wires of the second crane C2 are connected to the shackles Sh. The suspension pedestal HF accommodates the vicinity of the other end of the monopile MP inside the opening HFc formed by the bottom HFa and the side portions HFb. At this time, the suspension pedestal HF only supports the weight of the monopile MP by coming into contact with the monopile MP, and is not fixed by means such as bolt fastening or welding. With the vicinity of the other end of the monopile MP accommodated in the opening HFc, the suspension pedestal HF is suspended by the second crane C2. Thus, the vicinity of the other end of the monopile MP is suspended by the second crane C2 and the suspension pedestal HF.

[0014] (Regarding the lid) In the present embodiment, as shown in FIG. 5, a lid MPC is provided at the other end of the monopile MP. By doing this, when lifting one end of the monopile MP by the first crane C1, water is prevented from entering the monopile MP, thereby generating buoyancy in the monopile MP. Thereby, the weight added to the first crane C1 when lifting one end of the monopile MP is reduced. Also, it facilitates the removal process described later.

[0015] The lid MPC is, for example, disk-shaped and contacts the inner peripheral surface of the monopile MP, which is cylindrical. The outer diameter of the lid MPC is smaller than the inner peripheral circle of the monopile MP. Thus, the lid MPC is arranged to fit inside the monopile MP. On the outer peripheral edge of the lid MPC, for example, a sealing mechanism (not shown) that can be expanded or contracted by hydraulic pressure or pneumatic pressure is provided. For example, with the lid MPC arranged inside the monopile MP, the sealing mechanism is brought into close contact with the inside of the monopile MP by hydraulic pressure or pneumatic pressure. That is, the sealing mechanism is pressed against the inner peripheral surface of the monopile MP. This suppresses the entry of water into the monopile MP while fixing the lid MPC and the monopile MP. Also, for example, with the lid MPC and the monopile MP fixed, the lid MPC can be removed by reducing the hydraulic pressure or pneumatic pressure of the sealing mechanism. The sealing mechanism of the lid MPC is preferably operated, for example, by remote control. This can eliminate the need for an operator to directly remove the lid MPC, for example.

[0016] (Construction method) Hereinafter, the construction method of the monopile MP according to this embodiment will be described. The construction method of the monopile MP according to this embodiment includes a phase-lifting step, a removal step, a lifting step, and a driving step. Each of these steps is performed, for example, as shown in FIG. 1, after transporting the monopile MP to the construction site by the transport ship S3.

[0017] (Regarding the phase-lifting step) The phase-lifting step is a step of phase-lifting the monopile MP with the first crane C1 and the second crane C2. More specifically, as shown in FIGS. 1 and 2, the phase-lifting step suspends a gripping tool BH that grips one end of the monopile MP with the first crane C1 and suspends a suspension gantry HF that supports the vicinity of the other end of the monopile MP with the second crane C2. Thus, the monopile MP is lifted from the transport ship S3 in a lying state. After lifting the monopile MP from the transport ship S3, by moving the transport ship S3, the other end of the monopile MP can be moved downward.

[0018] Here, as described above, when suspending the monopile MP in tandem, it is preferable to keep the distance between the first crane C1 and the second crane C2, that is, the distance between the first ship S1 and the second ship S2, constant. Therefore, the tandem suspension process includes an arrangement process for adjusting the distance between the first ship S1 and the second ship S2. In the arrangement process, before suspending the monopile MP in tandem, as shown in FIGS. 1 and 2, the first ship S1 and the second ship S2 are arranged so as to sandwich the barge B so that the distance between the first hook C1f of the first crane C1 and the second hook C2f of the second crane C2 substantially matches the length of the monopile MP. Note that the distance between the first hook C1f and the second hook C2f is, for example, the distance between the first hook C1f and the second hook C2f in the horizontal direction. Alternatively, the distance between the first hook C1f and the second hook C2f may be the distance in a state where the first hook C1f and the second hook C2f are at the same height in the vertical direction (the vertical direction). Further, the distance between the first hook C1f and the second hook C2f means the distance in a state where either one or both of the first crane C1 and the second crane C2 are in the initial position in the turning direction when either one or both of the first crane C1 and the second crane C2 are of the turning type. In the present embodiment, "substantially match" means that the error in the mutual distance or length is within about 5%. That is, in the arrangement process, the distance between the first hook C1f of the first crane C1 and the second hook C2f of the second crane C2 is adjusted so as to be at least within ±5% of the length of the monopile MP. Here, depending on the size of the barge B arranged between the first ship S1 and the second ship S2, the distance between the first ship S1 and the second ship S2, that is, the distance between the first hook C1f of the first crane C1 and the second hook C2f of the second crane C2 may not be appropriate. In such a case, a spacer (not shown) may be appropriately arranged between the first ship S1 and the second ship S2 and the barge B. Alternatively, a fender (not shown) may be arranged between the first ship S1 and the second ship S2 and the barge B.

[0019] (Regarding the removal process) FIG. 6 is a plan view of the removal process according to the embodiment. FIG. 7 is a side view of the removal process according to the embodiment. The removal process is a process of automatically removing the suspension frame HF from near the other end of the monopile MP by suspending the suspension frame HF with the second crane C2. When performing the removal process, as shown in FIGS. 6 and 7, the transport ship S3 is not positioned below the monopile MP. In the removal process, first, by suspending the suspension frame HF with the second crane C2, the suspension frame HF and the vicinity of the other end of the monopile MP supported by the suspension frame HF are submerged in water. Here, as described above, a lid MPC is provided at the other end of the monopile MP. And the suspension frame HF only supports the weight of the monopile MP by coming into contact with the monopile MP, and is not fixed by bolt fastening or welding. Therefore, when the vicinity of the other end of the monopile MP sinks into the water along with the suspension frame HF, buoyancy is generated in the vicinity of the other end of the monopile MP. By this, the vicinity of the other end of the monopile MP becomes unnecessary to be supported by the suspension frame HF, and automatically separates from the suspension frame HF. By this, the removal process is performed.

[0020] Note that the second crane C2 is used in the driving-in process described later after the removal process is performed. For this reason, in the second crane C2, it is preferable that the work of exchanging the lifting target from the suspension frame HF to the pile driver IH is performed while the lifting process described below is performed by the first crane C1.

[0021] (Regarding the lifting process) The lifting process is a process of lifting one end of the monopile MP with the first crane C1 so that the pipe axis of the monopile MP is along the vertical direction. By this, the monopile MP is erected on the sea. The lifting process includes an erection process, a guiding process, a temporary driving-in process, and a removal process.

[0022] FIG. 8 is a side view of the erection process according to the embodiment. The erection process is a process of erecting the monopile MP on the sea by lifting one end of the monopile MP with the first crane C1 as shown in FIG. 8. This enables the monopile MP to be driven into the seabed ground. In addition, after erecting the monopile MP and when the monopile MP is in a state close to vertical, the lid MPC may be removed from the monopile MP by reducing the hydraulic pressure or pneumatic pressure of the sealing mechanism of the lid MPC. By allowing water to enter the interior of the monopile MP in this way, the other end of the monopile MP can be made more likely to sink towards the seabed. Also, in the temporary driving process and the driving process described later, it is possible to make it easier to penetrate the other end of the monopile MP into the seabed ground. Note that, in order to make it easier to lift the removed lid MPC onto the sea, a rope may be attached to the lid MPC in advance before the erection process.

[0023] FIG. 9 is a plan view of the guiding process according to the embodiment. FIG. 10 is a side view of the guiding process according to the embodiment. As shown in FIGS. 9 and 10, the guiding process is a process of aligning the monopile MP with the installation location on the seabed ground. Specifically, the guiding process is a process of guiding the monopile MP to the positioning marine structure G installed on the sea in advance. The positioning marine structure G is arranged on the sea in advance according to the installation location of the monopile MP. The positioning marine structure G is formed, for example, by appropriately combining steel pipes as shown in FIGS. 9 and 10. The positioning marine structure G is formed, for example, in a U shape in plan view as shown in FIG. 9. In the guiding process, the monopile MP erected in the erection process is appropriately aligned so that the monopile MP enters the opening Ga of the positioning marine structure G, thereby guiding the monopile MP to the positioning marine structure G. In addition, the positioning marine structure G may have a function of supporting the monopile MP before it is installed on the seabed ground, in addition to the function of guiding the monopile MP.

[0024] FIG. 11 is a side view of the temporary driving process according to the embodiment. The temporary driving process is a process of driving the other end of the monopile MP into the seabed ground. Here, when the guiding process is completed, a gripping tool BH is attached to one end of the monopile MP as shown in FIG. 11. As described above, the gripping tool BH is a vibro hammer. In the temporary driving process, while the first crane C1 lifts the monopile MP via the gripping tool BH, the gripping tool BH which is a vibro hammer is vibrated. By doing this, the other end of the monopile MP is driven into the seabed ground. In the temporary driving process, for example, it is preferable to drive the other end of the monopile MP toward the seabed ground to such an extent that the monopile MP can stand on its own on the seabed ground.

[0025] The removal process is a process of removing the first crane C1 from one end of the monopile MP. That is, in the removal process, by removing the gripping part BHa, the gripping tool BH is removed from one end of the monopile MP. By doing this, an obstacle to the driving process described below is removed.

[0026] (Regarding the driving process) FIG. 12 is a side view of the driving process. The driving process is a process in which the second crane C2 arranges a pile driver IH at one end and drives the monopile MP. In the present embodiment, the pile driver IH is an impact hammer including a so-called impact hydraulic hammer. That is, the pile driver IH drives the monopile MP into the seabed ground by dropping a hammer to strike one end of the monopile MP downward. Through the above respective processes, the construction of the monopile MP according to the present embodiment is performed.

[0027] As described above, according to the construction method according to this embodiment, it includes a phase suspension step, a lifting step, and a driving step. More specifically, first, in the phase suspension step, the monopile MP is phase-suspended by the first crane C1 and the second crane C2. Next, in the lifting step, one end of the monopile MP is lifted by the first crane C1 so that the pipe axis of the monopile MP is along the vertical direction. Then, in the driving step, the second crane C2 arranges the pile driver IH hanging at one end and drives the monopile MP. That is, after the phase suspension step is performed by the first crane C1 and the second crane C2, the lifting step is performed by the first crane C1 without using the second crane C2. By this, while the lifting step is being performed by the first crane C1, preparations for the driving step, such as arranging the pile driver IH on the second crane C2, can be made. Therefore, the time required for switching between the lifting step and the driving step can be shortened. Thus, the construction period can be shortened.

[0028] Also, in the phase suspension step, the gripping tool BH that grips one end of the monopile MP is suspended by the first crane C1, and the suspension gantry HF that supports the vicinity of the other end of the monopile MP is suspended by the second crane C2. And the suspension gantry HF has a substantially U-shaped cross section. Since the cross section of the suspension gantry HF is substantially U-shaped, when the suspension gantry HF supports the vicinity of the other end of the monopile MP, the vicinity of the other end of the monopile MP can be stabilized only by placing it on the suspension gantry HF without performing fixation by bolt fastening or the like. Also, by this, for example, when buoyancy is generated due to the vicinity of the other end of the monopile MP sinking into the water, the suspension gantry HF can automatically come off from the vicinity of the other end of the monopile MP without performing special work. Therefore, for example, it is possible to eliminate the need to perform the work of removing the suspension gantry HF from the vicinity of the other end of the monopile MP by a diver or the like. Furthermore, while the lifting step is being performed by the first crane C1, it is possible to quickly perform the replacement from the suspension gantry HF to the pile driver IH in the second crane C2. Thus, the construction period can be shortened.

[0029] Here, when the construction method according to this embodiment is carried out overseas, due to high waves, it may be difficult to keep the distance between the first ship S1 and the second ship S2 constant. Therefore, the phase-hoisting process includes the placement process. In the placement process, the first ship S1 and the second ship S2 are arranged so as to sandwich the barge B so that the distance between the first hook C1f of the first crane C1 and the second hook C2f of the second crane C2 substantially matches the length of the monopile MP. In this way, by sandwiching the barge B between the first ship S1 and the second ship S2, it is possible to easily maintain the distance between the first ship S1 and the second ship S2.

[0030] Furthermore, it further includes a removal process. In the removal process, the suspension frame HF is automatically removed from the vicinity of the other end of the monopile MP by suspending the suspension frame HF with the second crane C2. In this way, by automatically removing the suspension frame HF from the vicinity of the other end of the monopile MP, it is possible to eliminate the need for an operation to remove the suspension frame HF from the vicinity of the other end of the monopile MP by a diver or the like. Furthermore, while the lifting process is being performed by the first crane C1, the second crane C2 can quickly replace the pile driver IH from the suspension frame HF. Therefore, the construction period can be shortened.

[0031] Furthermore, the lifting process includes a removal process. In the removal process, the first crane C1 is removed from one end of the monopile MP. Thereby, when the driving process is performed, an object that obstructs the driving process can be removed from one end of the monopile MP. By this, in the driving process, it is possible to easily drive one end of the monopile MP with the pile driver IH suspended by the second crane C2 of the second ship S2. Therefore, the construction work can be made more efficient. Thus, it can contribute to shortening the construction period.

[0032] Moreover, the lifting process includes a guiding process. In the guiding process, the monopile MP is guided by the positioning offshore structure G. This makes it possible to easily position the monopile MP such that the pipe axis of the monopile MP is along the vertical direction. Also, in the driving process, the second crane C2 of the second ship S2 can be easily used to drive one end of the monopile MP by the pile hammer IH suspended by it. Therefore, the construction work can be made more efficient. Thus, it can contribute to shortening the construction period.

[0033] Also, the second ship S2 is a revolving crane ship. This makes it easy to align the position of the second hook C2f of the second crane C2 with respect to the object to be lifted. That is, it can be easily arranged for the pile hammer IH suspended by the second crane C2 to be at one end of the monopile MP. Also, for example, when performing the work of replacing what is suspended by the second crane C2 from the suspension pedestal HF with the pile hammer IH, the second crane C2 can be easily brought close to the pile hammer IH. Therefore, the construction work can be made more efficient. Thus, it can contribute to shortening the construction period.

[0034] Also, a lid MPC is provided at the other end of the monopile MP. This can prevent water from entering the inside of the monopile MP. Therefore, when lifting one end of the monopile MP with the first crane C1, buoyancy can be generated in the monopile MP by submerging the other end of the monopile MP in water. Thus, for example, even when the lifting capacity of the first crane C1 is lower than the weight of the monopile MP, one end of the monopile MP can be lifted.

[0035] Note that the technical scope of the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure. For example, the first ship S1 and the second ship S2 are not limited to the above-described crane ships, and may be a SEP (Self-Elevating Platform).

[0036] In addition, within the scope not departing from the gist of the present disclosure, it is possible to appropriately replace the components in the above-described embodiment with well-known components, and the above-described modified examples may be appropriately combined.

[0037] (Appendix) The construction method according to the above-described embodiment is grasped as follows, for example. <1> A construction method according to an aspect of the present disclosure is a construction method of suspending a monopile using a first crane of a first ship and a second crane of a second ship, the method including: a suspending step of suspending the monopile with the first crane and the second crane; a lifting step of lifting one end of the monopile with the first crane so that the pipe axis of the monopile is along the vertical direction; and a driving step of disposing a pile driver suspended by the second crane at one end of the monopile and driving the monopile.

[0038] According to the above construction method, a suspending step, a lifting step, and a driving step are provided. More specifically, first, in the suspending step, the monopile is suspended by the first crane and the second crane. Next, in the lifting step, one end of the monopile is lifted by the first crane so that the pipe axis of the monopile is along the vertical direction. Then, in the driving step, a pile driver suspended by the second crane is disposed at one end, and the monopile is driven. That is, after the suspending step is performed by the first crane and the second crane, the lifting step is performed by the first crane without using the second crane. By this, while the lifting step is being performed by the first crane, preparations for the driving step, such as disposing a pile driver on the second crane, can be made. Therefore, the time required for switching between the lifting step and the driving step can be shortened. Therefore, the construction period can be shortened.

[0039] <2>In the construction method according to <1>, in the phase hoisting process, a gripping tool for gripping one end of the monopile is suspended by the first crane, and a suspension gantry having a substantially U-shaped cross section and supporting the vicinity of the other end of the monopile is suspended by the second crane. A configuration characterized by this may be adopted.

[0040] Also, in the phase hoisting process, a gripping tool for gripping one end of the monopile is suspended by the first crane, and a suspension gantry for supporting the vicinity of the other end of the monopile is suspended by the second crane. The suspension gantry has a substantially U-shaped cross section. Since the cross section of the suspension gantry is substantially U-shaped, when the suspension gantry supports the vicinity of the other end of the monopile, the vicinity of the other end of the monopile can be stabilized only by placing the vicinity of the other end of the monopile on the suspension gantry without performing fixation by bolt fastening or the like. Further, by this, for example, when buoyancy is generated due to the vicinity of the other end of the monopile sinking into the water, the suspension gantry automatically detaches from the vicinity of the other end of the monopile without performing special work. Therefore, for example, it is possible to eliminate the need to perform work to remove the suspension gantry from the vicinity of the other end of the monopile by a diver or the like. Furthermore, while the lifting process is being performed by the first crane, the second crane can quickly change the attachment to the pile driver from the suspension gantry. Therefore, the construction period can be shortened.

[0041] <3>In the construction method according to <1> or <2>, the phase hoisting process includes an arrangement process of arranging the first ship and the second ship so as to sandwich a bar so that the distance between the first hook of the first crane and the second hook of the second crane substantially matches the length of the monopile. A configuration characterized by this may be adopted.

[0042] Here, when the construction method according to the present embodiment is carried out in the open sea, due to high waves, it may be difficult to keep the distance between the first ship and the second ship constant. Therefore, the counterweight process includes the placement process. In the placement process, the first ship and the second ship are arranged so as to sandwich the bar so that the distance between the first hook of the first crane and the second hook of the second crane substantially matches the length of the monopile. In this way, by sandwiching the bar between the first ship and the second ship, it is possible to easily maintain the distance between the first ship and the second ship.

[0043] <4>In the construction method according to any one of the above <1> to <3> aspects, it may further employ a configuration characterized by further comprising a removal process of automatically removing the suspension bracket from the vicinity of the other end by suspending the suspension bracket with the second crane.

[0044] Also, a removal process is further provided. In the removal process, the suspension bracket is automatically removed from the vicinity of the other end of the monopile by suspending the suspension bracket with the second crane. In this way, by automatically removing the suspension bracket from the vicinity of the other end of the monopile, it is possible to eliminate the need for an operation to remove the suspension bracket from the vicinity of the other end of the monopile by a diver or the like. Furthermore, while the lifting process is being performed by the first crane, the second crane can quickly replace the pile hammer on the suspension bracket. Therefore, the construction period can be shortened.

[0045] <5>In the construction method according to any one of the above <1> to <4> aspects, it may further employ a configuration characterized in that the lifting process includes a removal process of removing the first crane from one end.

[0046] Also, the lifting process includes a removal process. In the removal process, the first crane is removed from one end of the monopile. As a result, when performing the driving process, an object that obstructs the driving process can be removed from one end of the monopile. This makes it easier to drive one end of the monopile with the pile hammer suspended by the second crane of the second ship in the driving process. Therefore, the construction work can be made more efficient. Consequently, it can contribute to shortening the construction period.

[0047] <6>In the construction method according to any one of the above aspects <1> to <5>, the lifting step may adopt a configuration characterized by including a guiding step of guiding the monopile to the positioning offshore structure.

[0048] Further, the lifting step includes a guiding step. In the guiding step, the monopile is guided to the positioning offshore structure. Thereby, it is possible to easily position the monopile such that the pipe axis of the monopile is along the vertical direction. Also, in the driving step, it is possible to easily drive one end of the monopile by the pile driver suspended by the second crane of the second ship. Therefore, the construction work can be made more efficient. Thus, it can contribute to shortening the construction period.

[0049] <7>In the construction method according to any one of the above aspects <1> to <6>, the second ship may adopt a configuration characterized by being a slewing crane ship.

[0050] Also, the second ship is a slewing crane ship. Thereby, it is possible to easily align the position of the second hook with respect to the object to be lifted by the second crane. That is, it is possible to easily arrange the pile driver suspended by the second crane at one end of the monopile. Also, for example, when performing the work of replacing the object lifted by the second crane from the suspension gantry with the pile driver, it is possible to easily bring the second crane closer to the pile driver. Therefore, the construction work can be made more efficient. Thus, it can contribute to shortening the construction period.

[0051] <8>In the construction method according to any one of the above aspects <1> to <7>, a lid may be provided at the other end of the monopile, and a configuration characterized by this may be adopted.

[0052] Also, a lid is provided at the other end of the monopile. This can prevent water from entering the inside of the monopile. Therefore, when lifting one end of the monopile with the first crane, buoyancy can be generated in the monopile by submerging the other end of the monopile in water. Thus, for example, even when the lifting capacity of the first crane is lower than the weight of the monopile, one end of the monopile can be lifted.

Explanation of Signs

[0053] B version BH Gripping tool BHa Gripping part C1 First crane C1f First hook C2 Second crane C2f Second hook G Positioning marine structure Ga Opening HF Suspension stand HFa Bottom HFb Side HFc Opening IH Pile driver MP Monopile MPC Lid S1 First ship S2 Second ship S3 Transport ship Sh Shackle

Claims

1. A construction method for suspending a monopile using a first crane on a first ship and a second crane on a second ship, comprising: a suspending step of suspending the monopile with the first crane and the second crane; a lifting step of lifting one end of the monopile with the first crane so that the pipe axis of the monopile is along the vertical direction; a driving step of arranging a pile driver suspended by the second crane at one end of the monopile and driving the monopile; The construction method is characterized by comprising the above steps.

2. In the suspending step, a gripping tool for gripping one end of the monopile is suspended by the first crane, and a suspension gantry having a substantially U-shaped cross section and supporting the vicinity of the other end of the monopile is suspended by the second crane. The construction method according to claim 1, characterized by the above.

3. The suspending step includes an arranging step of arranging the first ship and the second ship so as to sandwich a bar so that the distance between the first hook of the first crane and the second hook of the second crane substantially matches the length of the monopile. The construction method according to claim 2, characterized by the above.

4. A removing step of automatically removing the suspension gantry from the vicinity of the other end by suspending and lowering the suspension gantry with the second crane. The construction method according to claim 2, further comprising the above step.

5. The lifting step includes a removing step of removing the first crane from the one end. The construction method according to claim 1, characterized by the above.

6. The lifting step includes a guiding step of guiding the monopile to a positioning marine structure. The construction method according to any one of claims 1 to 5, characterized by the above.

7. The second ship is a revolving crane ship. The construction method according to any one of claims 1 to 5, characterized by the above.

8. A lid is provided at the other end of the monopile. The construction method according to any one of claims 1 to 5, characterized by the above.

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