JP5670128B2 - Floating structure for offshore facilities and construction method of offshore facilities - Google Patents

Description

  The present invention relates to a floating structure for offshore facilities, such as a floating offshore wind power generation facility that mounts a windmill on a floating structure floating on the ocean and performs offshore wind power generation, and a method for constructing the offshore facility.

  In recent years, wind power generation has attracted attention. However, suitable land on land has decreased, and it is considered that location development on the ocean will proceed in the future. Japan has a long coastline and is expected to promote offshore wind power development. However, the sea conditions are severe because it faces the open ocean such as the Pacific Ocean, and the floating bodies supporting the wind power generation facilities themselves are large, and the high difficulty of construction makes them expensive.

  In particular, in the construction of a floating-type offshore wind power generation facility, the cost of a mooring line for mooring a floating body and an anchor for fixing this to the seabed is high. In addition, the mooring method for floating bodies is a loose mooring method, which is a catenary mooring method using a steel chain, etc., and a tension mooring method, which is a tension leg mooring method in which steel pipes, steel bars, cables, etc. are tensioned and fixed firmly. A system is known (for example, refer to Patent Documents 1 to 6).

JP 2001-248535 A JP 2002-285951 A JP 2002-285951 A JP 2010-64648 A JP 2010-30379 A Japanese Patent Laid-Open No. 4-197887

  By the way, the tension mooring floating body (TLP: tension leg platform) using the above-mentioned tension mooring method is attracting attention because there is little possibility of floating the floating body and it is possible to mount a windmill for land as it is, but sea conditions are severe. In the sea area, since the anchor weight becomes huge, the construction difficulty level increases, and there is a risk that the construction cost increases.

  This invention is made | formed in view of the above, Comprising: It aims at providing the construction method of the floating structure for offshore facilities which can reduce the construction cost of an anchor, and an offshore facility.

In order to solve the above-described problems and achieve the object, a floating structure for an offshore facility according to claim 1 of the present invention has a central floating body as an offshore facility foundation, and a diameter from the vertical center of the central floating body. A floating structure for offshore facilities that is arranged on the outer side and includes a plurality of outer floating bodies respectively connected to the central floating body, and for mooring the main body to the sea floor with a tension mooring line A gravitational anchor that can be lowered; a removable temporary floating body that offsets the underwater weight of the anchor; and a position holding means that holds the position of the anchor when the anchor is lowered and installed on the seabed. The position holding means includes a position holding float that can be connected to the anchor and can adjust a buoyancy acting on the anchor by ballast adjustment .

State also, offshore facilities for floating construction according to claim 2 of the present invention, the Oite in claim 1 described above, provided the temporary floating body to the outer floating body and connected by tether to the anchor to the temporary floating It is possible to descend by.

Moreover, the floating structure for offshore facilities according to claim 3 of the present invention is a semi-sub floating structure according to claim 1 or 2 described above.

Moreover, the construction method of the offshore facility which concerns on Claim 4 of this invention is a method of constructing an offshore facility using the floating structure for offshore facilities as described in any one of Claims 1-3 mentioned above, The floating structure for offshore facilities produced in the production yard is towed to the offshore facility installation sea area, the anchor is lowered from the main body and settled on the seabed, the draft of the main body is increased, and the mooring line is An initial tension is generated in the mooring line by fixing to the main body and reducing the draft of the main body, and the temporary floating body is removed.

  According to the floating structure for an offshore facility according to the present invention, a central floating body as an offshore facility foundation, and a plurality of the central floating body that are arranged radially outward from the vertical axis of the central floating body and are respectively connected to the central floating body. A floating structure for an offshore facility comprising a main body composed of an outer floating body, and a descent gravity anchor for mooring the main body to the seabed with a tension mooring line, and offsetting the underwater weight of the anchor In addition to the provisional floating body that can be removed, the anchors are pre-installed in the floating structure so that the number of anchor construction days on the local ocean can be shortened, and the anchor construction cost can be reduced. There is an effect that can be. In addition, if the anchor is provided in advance in the floating structure, the floating structure requires a large buoyancy, and the floating structure main body may be increased in size. However, by providing a removable temporary floating body, the large size of the floating structure main body is provided. Can be prevented.

  According to the construction method of the offshore facility according to the present invention, it is a method of constructing the offshore facility using the offshore facility floating structure, and the offshore facility floating structure manufactured at the production yard is installed in the offshore facility installation sea area. Towed, and the anchor is lowered from the main body to the bottom of the sea, the draft of the main body is increased to fix the mooring line to the main body, and the draft of the main body is decreased to reduce the initial draft to the mooring line. Since tension is generated and the temporary floating body is removed, anchors are provided in advance in the floating structure, so that it is possible to reduce the number of anchor construction days on the local ocean and reduce anchor construction costs. There is an effect that can be done. In addition, if the anchor is provided in advance in the floating structure, the floating structure requires a large buoyancy, and the floating structure main body may be increased in size. However, by providing a removable temporary floating body, the large size of the floating structure main body is provided. Can be prevented.

FIG. 1 is a perspective view showing an example of a floating structure for offshore facilities according to the present invention. FIG. 2 is a side view showing an example of a floating structure for offshore facilities according to the present invention. FIG. 3 is a top view showing an example of a floating structure for offshore facilities according to the present invention. FIG. 4 is a flowchart of the construction method for offshore facilities according to the present invention. FIG. 5 is a diagram showing step 1 of the construction method for offshore facilities according to the present invention. FIG. 6 is a diagram showing step 2 of the construction method for offshore facilities according to the present invention. FIG. 7 is a diagram showing step 3 of the construction method for offshore facilities according to the present invention. FIG. 8 is a diagram showing step 4 of the construction method for offshore facilities according to the present invention. FIG. 9 is a diagram showing step 5 of the construction method for offshore facilities according to the present invention. FIG. 10: is a figure which shows the process 6 of the construction method of the offshore facility which concerns on this invention. FIG. 11 is a diagram showing a first modification of the construction method for offshore facilities of the present invention. FIG. 12 is a diagram showing a second modification of the construction method for offshore facilities according to the present invention.

  Embodiments of a floating structure for an offshore facility and a construction method for an offshore facility according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  As shown in FIGS. 1 to 3, a floating structure for offshore facilities according to the present invention (hereinafter referred to as “floating structure”) 10 includes a columnar central floating body 12 as an offshore facility foundation, and a central floating body 12. This is a semi-sub-type (semi-submersible) floating body structure including a main body 16 including three cylindrical outer floating bodies 14 that are connected and arranged radially outward from the vertical axis Z.

  The central floating body 12 is used as a wind turbine base on which the wind turbine for wind power generation and the tower 4 are mounted. One end of three slanted first connecting members 18 extending obliquely is fixed to the outer peripheral surface on the upper side of the central floating body 12, and 3 extending horizontally on the lower outer peripheral surface of the central floating body 12. One end of the rod-shaped second connecting member 20 is fixed.

  The three outer floating bodies 14 are arranged at equal intervals in the circumferential direction of a circle centering on the axis Z of the central floating body 12, and are connected to the central floating body 12 via the first connecting member 18 and the second connecting member 20. Has been.

  The floating structure 10 further includes three disk-shaped gravity anchors 22, three columnar temporary floating bodies 24, and three rhombus-shaped position holding floating bodies 26 (position holding means). Yes.

  The anchor 22 is disposed on the lower surface side of the three outer floating bodies 14 and can be lowered separately from the outer floating body 14 when the floating structure main body 16 is moored on the sea floor with a tension mooring line such as tendon. It is configured. When the anchor 22 is lowered, the anchor 22 is lowered while being connected and fixed to the temporary floating body 24 by a mooring line such as tendon. Thus, it becomes possible to aim at shortening of the anchor construction days on the sea by making the anchor 22 into the structure which can be previously attached to the floating structure main body 16 at a production yard or the like.

  The temporary floating body 24 is for canceling the underwater weight of the anchor 22 and is detachably provided on the upper surface side of the three outer floating bodies 14. Since the anchor 22 is a gravity type and has an extremely large weight, if the anchor 22 is attached to the floating structure main body 16 in advance, a large buoyancy is required for the main body 16. However, it is possible to prevent the size of the main body 16 from increasing by attaching the removable temporary floating body 24 together to the main body 16. That is, the anchor 22 can be lowered from the main body 16 to install the anchor 22 on the seabed, and the temporary floating body 24 can be removed from the main body 16 to maintain the buoyancy balance of the main body 16.

  The position-maintaining floating body 26 is for holding the planar arrangement position of the anchor 22 when the anchor 22 is lowered and installed on the seabed, and the buoyancy acting on itself can be adjusted by ballast adjustment. The position holding floating body 26 is arranged in contact with the upper surfaces of the two anchors 22 via the connection portions 28 on the lower surfaces of the recesses formed at both ends.

  Here, since the anchor 22 of the present embodiment is expected to be uneven on the seabed, a plurality of (three in the present embodiment) individual anchors are employed instead of a monolithic anchor. doing. If individual anchors are employed, installation accuracy is required and the construction difficulty level increases, so that each anchor 22 is suspended from the seabed with a temporary floating body 24 fixed via a mooring line. When the anchor 22 is suspended, the position holding floating body 26 sinks together with the anchor 22 while applying a ballast weight from the upper surface of the anchor 22. In this case, it is used as a position holding means for preventing the anchor 22 from swinging and holding its position. After the anchor 22 reaches the bottom of the sea, the position holding floating body 26 can be lifted by removing the ballast.

  Thus, according to the floating structure 10 for offshore facilities of the present invention, it is possible to reduce the number of anchor construction days on the local ocean, and to reduce the anchor construction cost. Further, if the anchor 22 is provided in the floating structure 10 in advance, the floating structure 10 needs a large buoyancy, and the floating structure main body 16 may be increased in size. The size of the structure body 16 can be prevented from being increased, and the floating structure body 16 can be reduced to a minimum size. Furthermore, the anchor installation accuracy when the anchor 22 is suspended from the seabed can be ensured by the action of the position holding floating body 26.

  Next, an offshore facility construction method according to the present invention will be described with reference to FIGS.

As shown in the flowchart of FIG. 4, the offshore facility construction method according to the present invention is a method of constructing an offshore wind power generation facility, and a floating structure 10 for offshore facilities is manufactured by a dog (floating body production yard). (Process 1), water is poured into the dog and floated (Process 2), and towed to the offshore facility installation sea area (Process 3). Then, the anchor 22 is lowered from the main body 16 to land on the seabed BL, the draft of the main body 16 is increased to fix the mooring line 30 to the main body 16 (step 4), and the mooring is performed by reducing the draft of the main body 16. Initial tension is generated in the cable 30 (step 5), and the temporary floating body 24 is removed (step 6).
Below, the content of each process 1-6 is explained in full detail.

[Step 1: Production of floating structure and mounting of windmill]
As shown in FIG. 5, the floating structure body 16, the anchor 22, the temporary floating body 24, the position holding floating body 26, and the windmill are assembled in the dog to manufacture the floating structure 10.

[Step 2: Water injection to the dog]
Next, as shown in FIG. 6, water is poured into the dog to float the floating structure 10 to the surface of the water and pull it out.

[Process 3: Local towing]
Next, as shown in FIG. 7, the floating structure 10 is towed to an offshore facility installation point by a ship or the like.

[Process 4: Anchor descent and seabed installation]
Next, as shown in FIG. 8, the fixation of the floating structure 10 and the anchor 22 is released. Water is poured into the position maintaining floating body 26 to increase the weight of the ballast, and the ballast is lowered together with the anchor 22 to land on the seabed BL. Here, the anchor 22 descends in a state where it is connected to the temporary floating body 24 and the mooring line 30.

[Step 5: Floating / removing floating body for position maintenance]
Next, as shown in FIG. 9, after the anchor 22 has settled, the ballast water in the position holding floating body 26 is drained, air is injected to float, and the position holding floating body 26 is removed. Subsequently, ballast water is poured into the main body 16 (for example, the inside of the outer floating body 14) to submerge the main body 16 from the water surface WL to a predetermined draft, and the upper end of the mooring line 30 is set to the main body 16 (for example, the upper end of the outer floating body 14). ). After fixing the mooring line 30, the ballast water inside the main body 16 is drained and an initial tension is applied to the mooring line 30 only by the buoyancy of the main body 16.

[Step 6: Removal of temporary floating body]
Finally, as shown in FIG. 10, the temporary floating body 24 is removed. By doing so, the offshore wind power generation facility 100 can be constructed.

  Thus, according to the construction method of the offshore facility which concerns on this invention, shortening of the construction days of an anchor on a local ocean can be aimed at, and the construction cost of an anchor can be reduced. Further, if the anchor 22 is provided in the floating structure 10 in advance, the floating structure 10 needs a large buoyancy, and the floating structure main body 16 may be increased in size. The size of the structure body 16 can be prevented from being increased, and the floating structure body 16 can be reduced to a minimum size. Furthermore, the anchor installation accuracy when the anchor 22 is suspended from the seabed can be ensured by the action of the position holding floating body 26.

  Next, modifications 1 and 2 of the construction method for offshore facilities according to the present invention will be described with reference to FIGS. 11 and 12. The following modifications 1 and 2 are construction methods that take into consideration the weight and stability when the position holding floating body 26 is pulled up, and can be appropriately selected according to the construction conditions at the site.

[Modification 1]
First, Modification 1 will be described.
As shown in FIG. 11, the offshore facility construction method according to Modification 1 of the present invention is provided with a winch 32 in the main body 16 of the floating structure for offshore facilities, leaving the air in the position holding floating body 26. Is suspended by a winch 32. Here, an overhanging base 34 is provided on each temporary floating body 24, a winch 32 is provided on the base 34, and a wire rope 36 from the winch 32 is fixed to the upper surface of both ends of the position holding floating body 26. Wind it up.

A specific construction procedure of the first modification will be described.
In the above-described step 4 (FIG. 8), after the floating structure 10 and the anchor 22 are released, the air in the position holding floating body 26 is left, and the suspended weight of the anchor 22 and the position holding floating body 26 is reduced. Then, the anchor 22 is lowered together with the position holding floating body 26 by the winch 32 to land on the seabed BL.

  After bottoming, air is discharged from the position holding floating body 26 to reduce buoyancy, the position holding floating body 26 is lifted by the winch 32, and air is injected again into the position holding floating body 26 near the water surface WL. The holding floating body 26 is removed.

  Subsequently, in the same manner as in Steps 5 and 6 described above, ballast water is poured into the main body 16 to submerge the main body 16 from the water surface WL to a predetermined draft, and the upper end of the mooring line 30 is fixed to the main body 16. The initial tension is generated on the mooring line 30 only by the buoyancy of the main body 16 by draining the ballast water inside the main body 16 and reducing the draft. Finally, the temporary floating body 24 is removed.

[Modification 2]
Next, Modification 2 will be described.
As shown in FIG. 12, the construction method of the offshore facility according to the modified example 2 of the present invention is provided with a winch 32 or the like as in the modified example 1 and injects water into the position-maintaining floating body 26, which is then submerged. To be left behind.

  Specifically, in the above step 4 (FIG. 8), the anchoring of the floating structure 10 and the anchor 22 is released, and the anchor 22 is lowered together with the position holding floating body 26 to land on the seabed BL. After landing, ballast water is poured into the position holding floating body 26, and the position holding floating body 26 is left on the seabed BL as it is.

  Subsequently, in the same manner as in Steps 5 and 6 described above, ballast water is poured into the main body 16 to submerge the main body 16 from the water surface WL to a predetermined draft, and the upper end of the mooring line 30 is fixed to the main body 16. The ballast water inside the main body 16 is drained and an initial tension is generated on the mooring line 30 only by the buoyancy of the main body 16. In the case of the second modification, it is not necessary to remove the temporary floating body 24 as in step 6 described above.

  As described above, according to the floating structure for an offshore facility according to the present invention, a central floating body as an offshore facility foundation and the central floating body are disposed radially outward from the vertical axis of the central floating body. A floating structure for offshore facilities having a main body composed of a plurality of outer floating bodies connected to each other, and a descent gravity anchor for mooring the main body to the sea floor with a tension mooring line, and the anchor In addition, a temporary floating body that can be removed to offset the underwater weight of the ship is further provided, so by providing the anchor in advance in the floating structure, it is possible to reduce the number of anchor construction days on the local ocean. The construction cost can be reduced. In addition, if the anchor is provided in advance in the floating structure, the floating structure requires a large buoyancy, and the floating structure main body may be increased in size. However, by providing a removable temporary floating body, the large size of the floating structure main body is provided. Can be prevented.

  Moreover, according to the construction method of the offshore facility according to the present invention, the offshore facility is constructed using the offshore facility floating structure, and the offshore facility floating structure produced at the production yard is used as the offshore facility. Tow to the installation sea area, descend the anchor from the main body to land on the seabed, increase the draft of the main body to fix the mooring line to the main body, and reduce the draft of the main body to reduce the mooring line The initial tension is generated and the temporary floating body is removed, so that the anchors are provided in advance in the floating structure, so that it is possible to reduce the number of anchor construction days on the local ocean and reduce the anchor construction cost. There is an effect that can be. In addition, if the anchor is provided in advance in the floating structure, the floating structure requires a large buoyancy, and the floating structure main body may be increased in size. However, by providing a removable temporary floating body, the large size of the floating structure main body is provided. Can be prevented.

  As described above, the floating structure for offshore facilities according to the present invention includes a floating structure for floating offshore wind power generation in which a windmill is mounted on the floating structure floating on the ocean and a construction method for the offshore facility. In particular, it is suitable for a floating structure for offshore wind power generation moored on the seabed by a tension mooring method and a construction method of an offshore wind power generation facility.

4 towers 10 floating structures for offshore facilities 12 central floating bodies 14 outer floating bodies 16 main bodies 18 first connecting members 20 second connecting members 22 anchors 24 temporary floating bodies 26 position holding floating bodies (position holding means)
28 Connecting portion 30 Mooring line 32 Winch 34 Mounting base 36 Wire rope 38 Pulley 100 Offshore wind power generation facility (offshore facility)
WL Water surface BL Sea floor Z Axis center

Claims (4)

For offshore facilities provided with a main body comprising a central floating body as an offshore facility foundation and a plurality of outer floating bodies arranged radially outward from the vertical axis of the central floating body and connected to the central floating body, respectively. A floating structure,
A descent-type gravity anchor for mooring the main body to the seabed with a tension mooring line, a removable temporary floating body for offsetting the underwater weight of the anchor, and when the anchor is lowered and installed on the seabed Position holding means for holding the position of the anchor ,
A floating structure for offshore facilities characterized in that the position holding means comprises a position holding floating body that can be connected to the anchor and can adjust the buoyancy acting on itself by ballast adjustment . The floating structure for offshore facilities according to claim 1, wherein the temporary floating body is provided on the outer floating body, and the anchor can be lowered in a state where the anchor is connected to the temporary floating body with a mooring line. The floating structure for offshore facilities according to claim 1 or 2 , wherein the floating structure is a semi-sub floating structure. A method for constructing an offshore facility using the floating structure for an offshore facility according to any one of claims 1 to 3 ,
Tow the floating structure for offshore facilities produced in the production yard to the offshore facility installation area,
The anchor is lowered from the main body and settled on the seabed, the draft of the main body is increased to fix the mooring line to the main body, and the draft of the main body is reduced to generate initial tension on the mooring line. The construction method of the offshore facility characterized by removing the temporary floating body.

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