Construction method of on-water structure

Abstract

To provide a construction method of an on-water structure capable of efficiently constructing the on-water structure by reducing work man-hours required to construct the on-water structure in a construction water area.SOLUTION: In driving work of support piles 2 constituting an on-water structure 1, driving guide jigs 20 having a plurality of pile insertion parts 21 arranged at intervals each other in a plan view are arranged on a water bottom ground SB, and the plurality of support piles 2 are driven into the water bottom ground SB with the pile insertion parts 21 as a guide. In work for constructing a superstructure 3 constituting the on-water structure 1, a superstructure panel unit 4 having a floor structure 5 extending over the plurality of support piles 2 and a plurality of receiving girders 8 arranged at intervals each other in a plan view at a lower part of the floor structure 5 is produced in advance, and the superstructure 3 is constructed by installing each of the receiving girders 8 constituting the superstructure panel unit 4 on the plurality of support piles 2, and fixing the superstructure panel unit 4 to an upper part of the plurality of support piles 2.SELECTED DRAWING: Figure 29

Description

[Technical Field]

[0001] The present invention relates to a method for constructing an offshore structure, and more particularly to a method for constructing an offshore structure that reduces the number of work steps required to construct an offshore structure in a construction water area and enables the efficient construction of the offshore structure. [Background technology]

[0002] Various methods have been proposed for constructing floating structures such as piers, in which multiple support piles are driven into the waterbed and a superstructure is constructed on top of the multiple support piles (for example, Patent Document 1). The work of driving support piles into the waterbed is affected by water currents, waves, and the like, making it difficult to accurately drive the multiple support piles according to a pre-planned arrangement, and errors are likely to occur in the relative positional relationships between the support piles. Therefore, in the invention described in Patent Document 1, beam assemblies are installed on each of multiple support piles (joint piles) driven into the waterbed, and the beams are constructed by filling the gaps between adjacent beam assemblies with poured concrete. The superstructure is then constructed by installing a deck slab on top of the beams.

[0003] This construction method has the advantage that it is possible to construct the superstructure even if there is an error in the installation position of the support piles, resulting in variations in the relative positional relationship between the support piles, but it requires a lot of work in the construction water area, such as installing beam assemblies for each support pile and pouring concrete to connect adjacent beam assemblies.With this construction method, there are limits to how much work efficiency can be improved because the number of complicated work steps in the construction water area is high. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-123633 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a method for constructing an offshore structure that can reduce the number of work steps required to construct an offshore structure in a construction water area and efficiently construct the offshore structure. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a method for constructing an offshore structure in which a plurality of support piles are erected on the waterbed ground, and a superstructure construction work is carried out to construct an offshore structure in which a plurality of support piles and a superstructure are integrated together. In the pile driving work, a driving guide jig having a plurality of pile insertion portions arranged at intervals from each other in a plan view is placed on the waterbed ground, and the plurality of support piles are driven into the waterbed ground using the pile insertion portions as guides. The piles are driven into the bottom ground at intervals from each other in a plan view, and in the superstructure construction work, a superstructure panel unit is prepared in advance, which has a floor structure extending across the multiple support piles and multiple support girders arranged at intervals from each other in a plan view below the floor structure, and each of the support girders that make up the superstructure panel unit is erected on top of the multiple support piles, and the superstructure is constructed by fixing the superstructure panel unit to the top of the multiple support piles.

[0007] In order to achieve the above object, another method for constructing an offshore structure of the present invention comprises carrying out pile driving work for erecting a plurality of support piles on the water bottom ground, and superstructure construction work for constructing a superstructure on top of the plurality of support piles, thereby constructing an offshore structure in which the plurality of support piles and the superstructure are integrated, wherein in the reference pile driving step for driving the support piles to be used as a reference for positioning in the pile driving work, a self-elevating barge having lifting legs, a barge body that can be raised and lowered relative to the lifting legs, and a crane mounted on the barge body is placed in front of the water bottom ground. The barge is stopped in a jacked-up state with the lifting legs touching the bottom, and a driving auxiliary device is mounted on the barge body, the device comprising a pile guide section through which the support pile is inserted and a movement mechanism for moving the pile guide section relative to the barge body, the pile guide section is positioned outside the barge body by the movement mechanism, the support pile used as a reference for positioning is inserted into the pile guide section, and the support pile used as a reference for positioning is driven into the bottom ground, and in a post-driving step of driving other support piles after the reference pile driving step in the pile driving work, the self-lifting barge The ship is stopped in the jacked-up state, and a driving guide jig having a plurality of pile insertion portions arranged at intervals from each other in a plan view is lowered from above the support piles that serve as a reference for positioning, and the driving guide jig is placed on the bottom ground with the support pile that serves as a reference for positioning inserted into one of the pile insertion portions, and the other pile insertion portions into which the support pile that serves as a reference for positioning has not been inserted are used as guides to drive the support piles other than the support pile that serves as a reference for positioning at intervals from each other in a plan view, and in the superstructure construction work, The method is characterized in that a superstructure panel unit having a floor structure extending over the support piles and a plurality of support girders arranged at intervals from each other in a plan view below the floor structure is prepared in advance, and the superstructure panel unit is placed on the barge body, and then the crane is used to place the superstructure panel unit on top of the plurality of support piles that have been driven into the bottom ground, so that each of the support girders that make up the superstructure panel unit is erected on top of the plurality of support piles, and the superstructure is constructed by fixing the superstructure panel unit to the top of the plurality of support piles. [Effects of the Invention]

[0008] In the former and latter methods of constructing an offshore structure of the present invention, during pile driving work, a driving guide jig having multiple pile insertion sections spaced apart from one another in a plan view is placed on the waterbed, and multiple support piles are driven into the waterbed using the pile insertion sections as guides, thereby enabling the multiple support piles to be driven accurately in a pre-planned arrangement. During superstructure construction work, a superstructure panel unit is pre-fabricated, which includes a floor structure extending across the multiple support piles and multiple support girders arranged at intervals from one another in a plan view below the floor structure. In the construction waters, the superstructure extending across the multiple support piles can be constructed simply by erecting each support girder constituting the superstructure panel unit on top of the multiple support piles and securing the superstructure panel unit to the top of the multiple support piles. Using the driving guide jig to drive the multiple support piles accurately in a pre-planned arrangement prevents misalignment between the support girders and support piles constituting the pre-fabricated superstructure panel unit. Therefore, the number of man-hours required to construct an offshore structure in the construction water area can be reduced, and the offshore structure can be constructed efficiently.

[0009] Furthermore, in the latter method of constructing an offshore structure of the present invention, in the reference pile driving process in which support piles that serve as a reference for positioning in pile driving work are driven, the self-lifting barge is stopped in a jacked-up position, the pile guide section of the driving auxiliary device mounted on the barge body of the self-lifting barge is positioned on the outside of the barge body, and the support pile that serves as a reference for positioning is inserted through the pile guide section, and the support pile that serves as a reference for positioning is driven into the bottom ground, thereby allowing the support pile that serves as a reference for positioning to be driven efficiently and with high precision at the pre-planned driving position. In the post-driving process following the reference pile driving process in pile driving work, the driving guide jig is lowered from above the support pile that is to be used as the positioning reference, and the driving guide jig is placed on the bottom ground with the support pile that is to be used as the positioning reference inserted into one of the pile insertion sections.The other pile insertion sections that are not passed through by the support pile that is to be used as the positioning reference are used as guides, and the support piles other than the support pile that is to be used as the positioning reference are driven at intervals from each other in a planar view, allowing the support piles other than the support pile that is to be used as the positioning reference to be driven accurately in a pre-planned position. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an explanatory diagram showing a schematic front view of an offshore structure constructed in accordance with the present invention. [Figure 2] FIG. 2 is an explanatory diagram illustrating the above-ground structure of FIG. 1 in a plan view. [Figure 3] 2 is an explanatory diagram showing a schematic plan view of the arrangement of support piles that constitute the above-water structure of FIG. 1. FIG. [Figure 4] 1 is an explanatory diagram illustrating a concrete pouring guide jig used in the present invention in a plan view. FIG. [Figure 5] 5 is an explanatory diagram illustrating the pouring guide jig of FIG. 4 as viewed from the side. FIG. [Figure 6] 2 is an explanatory diagram showing a schematic front view of an upper structure panel unit that constitutes the above-water structure of FIG. 1. FIG. [Figure 7] This is an explanatory diagram showing a schematic plan view of the state in which the integrated girder and support girder that make up the superstructure panel unit in Figure 6 and the deck slab that makes up the superstructure panel unit have been separated. [Figure 8] This is an explanatory diagram showing a schematic plan view of a self-lifting barge with a crane and a concrete driving auxiliary device mounted on the barge body, and with a concrete driving guide jig, support piles, superstructure panel unit, top plate, support members and pile driving equipment loaded on the barge body. [Figure 9] 9 is an explanatory diagram showing a cross-sectional view of the pile guide portion of the driving auxiliary device of FIG. 8 arranged on the barge body. [Figure 10] 10 is an explanatory diagram showing a schematic plan view of the pile guide portion of the driving auxiliary device after it has been moved to the outside of the barge body from the state shown in FIG. 9, with the opening / closing portion of the pile guide portion opened. FIG. [Figure 11] This is an explanatory diagram showing a schematic plan view of the state in which the pile guide section of the driving auxiliary device is moved further toward the outside of the barge body from the state shown in Figure 10, and the support pile is inserted through the pile guide section to close the opening / closing section. [Figure 12] 12 is an explanatory diagram illustrating a cross-sectional view of the driving auxiliary device and the support pile in the state shown in FIG. 11. FIG. [Figure 13] FIG. 9 is an explanatory diagram showing a schematic plan view of the state in which the first support pile, which serves as a reference for positioning, is being driven using the driving assistance device of FIG. 8 and a pile driving device suspended by a crane on a self-lifting barge. [Figure 14] 14 is an explanatory diagram illustrating the state of FIG. 13 in cross section. FIG. [Figure 15] This is an explanatory diagram showing a schematic plan view of the state in which a second support pile, which serves as a positioning reference, is being driven using a driving assistance device and a pile driving device suspended by a crane from the state shown in Figures 13 and 14. [Figure 16] This is an explanatory diagram showing a schematic plan view of the state in which, after the third support pile used as the positioning reference has been driven from the state shown in Figure 15, a driving guide jig is lowered using a crane from above the three support piles used as the positioning reference, and the support piles are inserted into each of the three pile insertion portions of the driving guide jig. [Figure 17] 17 is an explanatory diagram illustrating the state of FIG. 16 in cross section. FIG. [Figure 18]This is an explanatory diagram showing a schematic cross-sectional view of the state in which the casting guide jig is placed on the bottom ground from the state shown in Figures 16 and 17, and the fourth support pile is being cast using the pile insertion section in which no support pile has been inserted as a guide. [Figure 19] 19 is an explanatory diagram illustrating the state of FIG. 18 in a plan view. [Figure 20] This is an explanatory diagram showing a schematic plan view of the state in which, after the driving of the fourth to sixth support piles from the state shown in Figures 18 and 19 has been completed, the driving guide jig is moved and the seventh support pile is being driven. [Figure 21] This is an explanatory diagram showing a schematic plan view of the state in which the eighth and ninth support piles have been driven from the state shown in Figure 20, the driving guide jig has been removed, they have been loaded onto a self-lifting barge, and top plates have been installed on the top ends of each support pile driven into the bottom ground. [Figure 22] 22 is an explanatory diagram illustrating the state of FIG. 21 in cross section. FIG. [Figure 23] This is an explanatory diagram showing a schematic plan view of the state in which, after top plates have been installed on each of the support piles driven into the waterbed from the state shown in Figures 21 and 22, a crane is used to install the first set of superstructure panel units on top of multiple support piles. [Figure 24] FIG. 24 is an explanatory diagram illustrating the state of FIG. 23 in cross section. [Figure 25] This is an explanatory diagram showing a schematic plan view of the situation in which, after the installation of the first set of superstructure panel units from the state shown in Figures 23 and 24 has been completed, the second load of components is loaded onto the self-lifting barge, the self-lifting barge is moved and stopped, and then the tenth support pile, which will serve as the positioning reference, is driven using a driving assistance device and a pile driving device suspended by a crane. [Figure 26] This is an explanatory diagram showing a schematic plan view of the state in which, after the driving of the 11th to 13th support piles, which serve as positioning references from the state shown in Figure 25, has been completed, the driving guide jig is placed on the bottom ground with a support pile inserted into each of the two pile insertion portions of the driving guide jig, and the 14th support pile is driven using the pile insertion portion into which no support pile has been inserted as a guide. [Figure 27]This is an explanatory diagram showing a schematic plan view of the state in which, after the driving of the 15th to 21st support piles and the installation of the top plate have been completed from the state shown in Figure 26, a second set of superstructure panel units is being installed on top of multiple support piles using a crane. [Figure 28] This is an explanatory diagram that shows a schematic plan view of the state in which, from the state shown in Figure 27, the third set of superstructure panel units is installed on top of several support piles, the third load of components is loaded onto the self-lifting barge, the self-lifting barge is moved and stopped, and then the 22nd and 23rd support piles that will serve as the positioning reference are driven, followed by the driving of the 24th support pile that will serve as the positioning reference. [Figure 29] This is an explanatory diagram showing a schematic plan view of the state in which, after the 24th support pile, which serves as the positioning reference from the state shown in Figure 28, has been driven, the 22nd to 24th support piles are inserted into the three pile insertion portions of the driving guide jig, and the driving guide jig is positioned on the bottom ground. [Figure 30] This is an explanatory diagram showing a schematic plan view of the state in which all support piles have been driven and top plates installed from the state shown in Figure 29, the fourth set of superstructure panel units have been installed on top of multiple support piles, and then the fifth set of superstructure panel units have been installed on top of multiple support piles. [Figure 31] FIG. 10 is an explanatory diagram showing a schematic front view of another embodiment of an on-water structure constructed according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a method for constructing an offshore structure according to the present invention will be described based on the embodiment shown in the drawings.

[0012] As shown in Figures 1 and 2, this method for constructing an offshore structure is a method for constructing an offshore structure 1 in a body of water such as the sea, a lake, a river, etc. The offshore structure 1 constructed by this construction method can be used, for example, as a temporary offshore structure for temporarily placing and assembling assembly parts for a wind power generation device used in the construction of a floating offshore wind power generation facility, or as a pier.

[0013] In this construction method, pile driving work, in which multiple support piles 2 are erected into the waterbed SB, and superstructure construction work, in which a superstructure 3 is constructed on top of the multiple support piles 2, are performed consecutively to construct an overwater structure 1 in which multiple support piles 2 and the superstructure 3 are integrated. In this construction method, the superstructure construction work involves installing superstructure panel units 4 on top of the multiple support piles 2 driven into the waterbed SB, thereby constructing the superstructure 3. In this embodiment, a top plate 9 is installed on the top end of each support pile 2, and a superstructure panel unit 4 is installed on top of the top plate 9. The top plate 9 can be installed anywhere. As illustrated in FIG. 2, this embodiment illustrates the case in which the superstructure 3 is constructed using six sets of superstructure panel units 4. In the figure, the left-right direction in a plan view of the overwater structure 1 is the X direction, the front-to-back direction in a plan view of the overwater structure 1 is the Y direction, and the up-down direction is the Z direction.

[0014] As illustrated in Figure 1, this construction method is particularly suitable for constructing an offshore structure 1 in a relatively deep body of water, with a water depth D1 of, for example, 8 m or more and 20 m or less, but can also be used in waters where the water depth D1 exceeds 20 m or where the water depth D1 is less than 8 m. The insertion depth D2 of the support piles 2 into the waterbed ground SB can be determined appropriately depending on the strength of the waterbed ground SB and the load-bearing capacity required of the offshore structure 1. The insertion depth D2 of the support piles 2 is, for example, 10 m or more and 30 m or less.

[0015] As shown in Figure 3, in the pile driving work of this construction method, multiple support piles 2 are driven into the waterbed ground SB at intervals from each other in a plan view. As the support piles 2, for example, steel pipe piles with an outer diameter of 500 mm to 3000 mm and a thickness of 10 mm to 50 mm can be used. Other prefabricated piles, such as concrete piles, can also be used as the support piles 2. The length (height) of the support piles 2 can be determined appropriately depending on the strength of the waterbed ground SB and the height of the above-water structure 1 to be constructed, but it is recommended to set it to, for example, 20 m to 60 m.

[0016] As shown in FIG. 3, this embodiment illustrates a case in which the support piles 2 are arranged in seven rows in the X direction with a distance L1 between them and five rows in the Y direction with a distance L2 between them. The distance L1 between adjacent support piles 2 in the X direction and the distance L2 in the Y direction are each set to, for example, 10 m or more and 30 m or less, more preferably 13 m or more and 27 m or less, and even more preferably 15 m or more and 25 m or less. In this embodiment, the distance L1 between adjacent support piles 2 in the X direction and the distance L2 in the Y direction are set to the same distance. The number and arrangement of the support piles 2 driven into the waterbed SB are not particularly limited as long as the distances (L1, L2) between adjacent support piles 2 are predetermined constant distances, and can be determined appropriately depending on the size and shape of the floating structure 1 to be constructed. For example, the distance L1 between adjacent support piles 2 in the X direction and the distance L2 in the Y direction can be set to different distances.

[0017] The support pile 2a illustrated in FIG. 3 indicates the first support pile 2 to be driven first and serves as a reference for positioning the floating structure 1, and support pile 2b indicates the second support pile 2 to be driven next. Support piles 2c to 2x indicate the third to twenty-fourth support piles 2 to be driven thereafter. In this embodiment, the support piles 2 are driven in the alphabetical order assigned to each support pile 2. The other support piles 2 without alphabets indicate the twenty-fifth to thirty-fifth support piles 2 to be driven thereafter. In this embodiment, the third support pile 2 from the left in the X direction in the first row in the Y direction is the first support pile 2a, which serves as a reference for positioning, the support pile 2 immediately to the left of that is the second support pile 2b, and the support pile 2 immediately to the left of that is the third support pile 2c. The order in which the support piles 2 are driven is not limited to this embodiment and can be determined appropriately depending on the construction conditions.

[0018] As illustrated in Figures 4 and 5, in this construction method, a driving guide jig 20 is used in the pile driving work. The driving guide jig 20 has a plurality of pile insertion sections 21 that are arranged at intervals from one another in a plan view. The pile insertion sections 21 are configured as cylindrical bodies with through holes through which the support piles 2 can be inserted in the Z direction. The inner diameter of the through holes of the pile insertion sections 21 is set to be slightly (for example, about 5 cm to 30 cm) larger than the outer diameter of the support piles 2, and when the support piles 2 are inserted into the pile insertion sections 21, vertical movement of the support piles 2 relative to the pile insertion sections 21 is not restricted, but horizontal movement of the support piles 2 relative to the pile insertion sections 21 is restricted.

[0019] In this embodiment, the driving guide jig 20 has pile insertion portions 21 arranged in two rows in the front-to-back direction (Y direction) and three rows in the left-to-right direction (X direction) in a plan view. The pile insertion portions 21 adjacent to each other in the X direction are connected by connecting portions 25 extending in the X direction, and the pile insertion portions 21 adjacent to each other in the Y direction are connected by connecting portions 25 extending in the Y direction. The pile insertion portions 21 are fixed in a predetermined arrangement by the connecting portions 25. The distance L1 between the pile insertion portions 21 adjacent to each other in the X direction (the centers of the pile insertion portions 21 in a plan view) is set to be the same as the distance L1 between the support piles 2 adjacent to each other in the X direction (the centers of the support piles 2 in a plan view) that are driven into the waterbed ground SB. The distance L2 between adjacent pile insertion portions 21 in the Y direction (the centers of the pile insertion portions 21 in a planar view) is set to the same distance as the distance L2 between adjacent support piles 2 in the Y direction (the centers of the support piles 2 in a planar view) that are driven into the waterbed ground SB.

[0020] That is, the intervals L1 and L2 between adjacent pile insertion portions 21 are set to the same distance as the intervals L1 and L2 between the support piles 2 to be driven into the submerged ground SB as planned in advance. In this embodiment, the interval L1 between adjacent pile insertion portions 21 in the X direction and the interval L2 between adjacent pile insertion portions 21 in the Y direction are set to the same distance. In this embodiment, the connecting portion 25 is configured with a truss-structured frame as an example, but the connecting portion 25 may also have an extendable structure such as a telescopic structure. If the connecting portion 25 has an extendable structure, the intervals L1 and L2 between the pile insertion portions 21 can be changed to a desired distance by changing the length of the connecting portion 25 depending on the construction conditions, thereby increasing versatility.

[0021] 4 and 5, in this embodiment, a cylindrical expanded head portion 22 is provided above each pile insertion portion 21, the diameter of which increases in a tapered manner from the upper end of the pile insertion portion 21 toward the top. A cylindrical expanded bottom portion 23 is provided below each pile insertion portion 21, the diameter of which increases in a tapered manner from the lower end of the pile insertion portion 21 toward the bottom. In this embodiment, a subsidence suppression portion 24 is further provided below the expanded bottom portion 23 to suppress the casting guide jig 20 (pile insertion portion 21) from sinking into the water bottom ground SB.

[0022] The pouring guide jig 20 of this embodiment is provided with a hoisting tool 26 used to hoist the pouring guide jig 20. The hoisting tool 26 is configured to be connectable to a wire rope 33a of a crane 33, which will be described later. The pouring guide jig 20 is also provided with a receiving tool 27 on which the hoisting tool 26 is placed when not connected to the wire rope 33a of the crane 33.

[0023] Considering workability, it is preferable to use a driving guide jig 20 in which the pile insertion sections 21 are arranged in two rows in the front-to-back direction and three rows in the left-to-right direction in a plan view, as in this embodiment, but the number and arrangement of the pile insertion sections 21 that make up the driving guide jig 20 are not limited to this embodiment. In the driving guide jig 20, the enlarged head section 22, the enlarged base section 23, the subsidence suppression section 24, the lifting device 26, and the receiving device 27, other than the pile insertion sections 21 and the connecting section 25, are not essential components and can be provided as needed. Details of pile driving work using the driving guide jig 20 will be explained later.

[0024] As illustrated in Figures 1, 2, and 6, the superstructure panel unit 4 used in constructing the superstructure 3 has a floor structure 5 extending across multiple support piles 2, and multiple support girders 8 arranged at intervals from each other in a plan view below the floor structure 5. In this embodiment, the superstructure panel unit 4 used extends across a total of nine support piles 2 arranged in three rows in each of the X and Y directions.

[0025] As shown in Fig. 6, in this embodiment, a plurality of support girders 8 extending in the Y direction are arranged at intervals L1 in the X direction. The interval L1 between adjacent support girders 8 (the centers of the support girders 8 in the width direction) is set to the same separation distance as the interval L1 between adjacent support piles 2 in the X direction (the centers of the support piles 2 in a plan view) that are driven into the waterbed ground SB. The interval L1 in the X direction between adjacent support girders 8 may be set to, for example, 10 m or more and 30 m or less, more preferably 13 m or more and 27 m or less, and even more preferably 15 m or more and 25 m or less, similar to the interval L1 between adjacent support piles 2 in the X direction.

[0026] The floor structure 5 of this embodiment is composed of multiple girder members 6 arranged on support girders 8 and a deck slab 7 (covering plate 7a) fixed onto the girder members 6. Each girder member 6 extends across multiple support girders 8. The sizes (dimensions) of the support girders 8 and the girder members 6 can be determined appropriately, but the support girders 8 and the girder members 6 should preferably be composed of I-beams with a height of 700 mm to 2000 mm and a width of 300 mm to 800 mm. The support girders 8 and the girder members 6 can also be composed of other steel materials, such as H-beams or channel steel. In this embodiment, the deck slab 7 is composed of multiple covering plates 7a, but the deck slab 7 can also be composed of, for example, metal plate-like members.

[0027] FIG. 7 shows the superstructure panel unit 4, which is composed of a single unit of girders 6 and support girders 8, separated from the deck slab 7. When the superstructure panel unit 4 is assembled, the deck slab 7 is fixed on top of the single unit of girders 6 and support girders 8. As illustrated in FIG. 7, in this embodiment, multiple girders 6 extending in the X direction are arranged on top of the support girders 8 at intervals in the Y direction, forming a lattice frame. Each overlapping support girder 8 and multiple girders 6 are joined by welding, bolts, or the like. The Y-direction spacing between adjacent girders 6 (the centers of the girders 6 in the width direction) is, for example, between 1 m and 5 m, and is preferably set to match the Y-direction width of the lining slab 7a that constitutes the deck slab 7. Details of the superstructure construction work using the superstructure panel unit 4 will be described later.

[0028] As shown in Figure 8, this embodiment illustrates the case where pile driving work and superstructure construction work are performed using a self-elevating barge 30 (hereinafter referred to as SEP vessel 30). The SEP vessel 30 has lifting legs 32, a barge body 31 that can be raised and lowered relative to the lifting legs 32, and a crane 33 mounted on the barge body 31. It is preferable to use a self-propelled SEP vessel 30 equipped with a propulsion device on the barge body 31, but it is also possible to use a non-self-propelled SEP vessel 30 that does not have a propulsion device and is moved by towing.

[0029] In this embodiment, a pile driving device 34 used in pile driving work is loaded onto the SEP vessel 30 (barge body 31). The pile driving device 34 is a device that drives the support piles 2 into the waterbed ground SB by applying impacts or vibrations to the pile heads of the support piles 2. As the pile driving device 34, for example, a known device such as a vibro hammer, hydraulic hammer, drop hammer, or static press-in machine is used.

[0030] As shown in Figure 8, in this embodiment, the SEP vessel 30 is equipped with an auxiliary concrete driving device 40 used to drive the support piles 2 that serve as a positioning reference. The auxiliary concrete driving device 40 is disposed near the side of the barge main body 31 of the SEP vessel 30. A space is provided on the barge main body 31 of the SEP vessel 30 in which the support piles 2, superstructure panel units 4, top plate 9, support members 10, driving guide jigs 20, and pile driving device 34 used to construct the floating structure 1 can be loaded.

[0031] As illustrated in Figures 9 to 12, the driving auxiliary device 40 includes a pile guide section 41 through which the support pile 2 is inserted, and a movement mechanism 42 that moves the pile guide section 41 relative to the barge body 31 of the SEP vessel 30. As illustrated in Figures 10 and 11, the pile guide section 41 of this embodiment is provided with a pair of opening / closing sections 41a at the front, and the front section (opening / closing sections 41a) of the pile guide section 41 can be opened and closed by a switching mechanism 41b.

[0032] 11 and 12, when the opening / closing part 41a is closed, the pile guide part 41 is cylindrical. When the support pile 2 is inserted into the pile guide part 41, the vertical movement of the support pile 2 relative to the pile guide part 41 is not restricted, but the horizontal movement of the support pile 2 relative to the pile guide part 41 is restricted. When the opening / closing part 41a is opened by the switching mechanism 41b, the constraint of the support pile 2 by the pile guide part 41 is released.

[0033] The moving mechanism 42 in this embodiment is composed of a first moving mechanism 43 that moves the pile guide section 41 in the width direction (Y direction) of the SEP vessel 30, a second moving mechanism 45 that moves the pile guide section 41 in the up and down direction (Z direction), and a third moving mechanism 50 that moves the pile guide section 41 in the length direction (X direction) of the SEP vessel 30.

[0034] The first movement mechanism 43 is composed of an actuator 44 extending in the ship's width direction. The actuator 44 is composed of, for example, a hydraulic cylinder or a pneumatic cylinder in which a rod 44b is extendable (movable forward and backward) relative to a cylinder 44a. In this embodiment, the rod 44b has a telescopic structure. The rear end of the pile guide part 41 is connected to the front end of the actuator 44 (rod 44b).

[0035] The second movement mechanism 45 is composed of a rotating part 46 to which the rear end of the actuator 44 is fixed, a lifting part 47 to which the rotating part 46 is rotatably connected, a support part 48 that supports the lifting part 47 so that it can move up and down in the vertical direction, and a lifting guide 49 that guides the lifting part 47's lifting and lowering movement relative to the support part 48. The third movement mechanism 50 is composed of a longitudinal movement rail 51 that extends in the longitudinal direction and is laid on the barge main body 31, and a movable base 52 that is movable in the longitudinal direction on the longitudinal movement rail 51. The support part 48 is fixed onto the movable base 52. The longitudinal movement rail 51 is laid near the side of the barge main body 31.

[0036] 9 and 12, in this embodiment, by rotating the rotating part 46 relative to the lifting part 47, the actuator 44 can be switched between a state in which it extends in the vertical direction (Z direction) and a state in which it extends in the width direction of the ship (Y direction). As shown in FIG. 9, when the concrete driving auxiliary device 40 is not in use, the protruding length of the rod 44b relative to the cylinder 44a of the actuator 44 is shortened to set the actuator 44 to a state in which it extends in the Z direction, thereby setting the pile guide part 41 to a state in which it is positioned near the side of the ship above the barge main body 31 (stored state).

[0037] As illustrated in FIG. 12, when using the driving assist device 40 for pile driving work, the rotating unit 46 is rotated relative to the lifting unit 47 to extend the actuator 44 in the Y direction. In this state, the pile guide unit 41 can be moved in the Y direction by changing the projection length of the rod 44b relative to the cylinder 44a of the actuator 44. Furthermore, by vertically raising and lowering the lifting unit 47 relative to the support unit 48, the pile guide unit 41 can be moved in the Z direction relative to the barge main body 31. Furthermore, by moving the movable platform 52 in the ship's longitudinal direction (X direction) along the ship's longitudinal movement rail 51, the pile guide unit 41 can be moved in the X direction relative to the barge main body 31. The opening and closing operation of the opening / closing unit 41a by the switching mechanism 41b and the movement of the pile guide unit 41 by the first movement mechanism 43, the second movement mechanism 45, and the third movement mechanism 50 can be remotely controlled by a controller from on board the SEP vessel 30.

[0038] The pile guide unit 41 is not limited to the configuration of this embodiment and can have various other configurations as long as it is configured to restrict horizontal movement without restricting vertical movement of the support pile 2 when the support pile 2 is inserted. The opening / closing unit 41a and the switching mechanism 41b are not essential components of the pile guide unit 41 and can be optionally provided. The moving mechanism 42 is not limited to the configuration of this embodiment and can have various other configurations as long as it is configured to move the pile guide unit 41 to a desired position outside the SEP vessel 30. This embodiment illustrates a case where the crane 33 and the concrete driving auxiliary device 40 are arranged side by side in the longitudinal direction of the SEP vessel 30, but the arrangement of the crane 33 and the concrete driving auxiliary device 40 on the barge main body 31 is not particularly limited. For example, the crane 33 and the concrete driving auxiliary device 40 can be arranged side by side in the width direction of the vessel.

[0039] Next, the specific work procedures for this construction method will be explained. The following will use as an example the case of constructing an overwater structure 1 using a total of 35 support piles 2 and six sets of superstructure panel units 4, as shown in Figures 1 and 2. In the following explanation, the area in which one set of superstructure panel units 4 is installed in plan view will be considered one section of the overwater structure 1.

[0040] In this embodiment, an example is shown in which the driving assist device 40 is used in the reference pile driving step in which a support pile 2 is driven to serve as a reference for positioning in pile driving work, and the driving guide jig 20 is used in the post-driving step in which other support piles 2 are driven after the reference pile driving step. In the construction method of the present invention, the reference pile driving step can also be performed using the driving guide jig 20 without using the driving assist device 40, but this case will be described later.

[0041] In the first voyage, the SEP vessel 30 will construct the section at the top left of the floating structure 1 shown in Figure 2. As shown in Figure 8, an auxiliary concrete driving device 40 is mounted on the barge body 31 of the SEP vessel 30, and a pile driving device 34 and a driving guide jig 20 are loaded on the barge body 31. Also loaded on the barge body 31 are the support piles 2, superstructure panel units 4, top plate 9, and support members 10 used to construct one section of the floating structure 1. It is advisable to prepare the superstructure panel units 4 in advance, on land or on board, before the SEP vessel 30 moves to the construction waters.

[0042] In this embodiment, nine support piles 2, one set of superstructure panel units 4, nine top plates 9, and 36 support members 10 are loaded on the barge main body 31. The support piles 2 can be stacked one on top of the other while lying on their side. Some of the loaded support piles 2 may protrude outside the barge main body 31. In this embodiment, the superstructure panel units 4 are placed on the barge main body 31, and a pouring guide jig 20 is placed on top of the superstructure panel units 4. The SEP barge 30 loaded with the above-mentioned materials is moved to the construction waters where the floating structure 1 will be constructed. When moving the SEP barge 30, the pile guide unit 41 of the pouring auxiliary device 40 should be stored on the barge main body 31.

[0043] Next, as illustrated in FIGS. 13 and 14 , in the reference pile driving step of the pile driving work, the SEP vessel 30 is stopped in a jacked-up state near the position where the support piles 2 (2a-2c) that serve as the positioning reference will be driven. As illustrated in FIG. 14 , when stopping the SEP vessel 30 in a jacked-up state, the lifting legs 32 are moved downward relative to the barge main body 31 floating in the water, so that the lower ends of the lifting legs 32 are seated on the water bottom SB. From this state, the barge main body 31 is moved upward relative to the lifting legs 32, so that the barge main body 31 is moved to a position higher than the water surface level WL, and the lifting legs 32 support the barge main body 31 in midair. By raising the barge main body 31 to a height out of the reach of waves, the barge main body 31 is no longer affected by waves.

[0044] In waters with a water depth D1 of 8 m or more and 40 m or less, the SEP vessel 30 can be stably moored in a jacked-up state. If the water bottom ground SB does not have sufficient strength to stably moor the SEP vessel 30 in a jacked-up state, it is advisable to carry out simple ground improvement work in advance to increase the strength of the water bottom ground SB.

[0045] 13 and 14, the pile guide unit 41 is positioned above the water at the planned driving position of the first support pile 2 (2a), which serves as a positioning reference, by the movement mechanism 42 of the driving assist device 40. As illustrated in FIGS. 11 and 12, in this embodiment, the pivoting unit 46 is pivoted relative to the lifting unit 47 to extend the actuator 44 in the Y direction, and the actuator 44 is operated to move the pile guide unit 41 in the Y direction, thereby moving the pile guide unit 41 above the water to the planned driving position of the first support pile 2 (2a). The position of the pile guide unit 41 in the X direction is adjusted by moving the movable base 52 in the X direction relative to the ship's longitudinal movement rail 51. The position of the pile guide unit 41 in the Z direction is adjusted by moving the lifting unit 47 in the Z direction relative to the support unit 48. The opening / closing unit 41a of the pile guide unit 41 is closed.

[0046] Next, the crane 33 is used to move the first support pile 2 loaded on the SEP vessel 30 in an upright position above the pile guide unit 41. The support pile 2 is then lowered so that it is inserted into the pile guide unit 41, and the lower end of the support pile 2 is placed on the waterbed ground SB. After that, the crane 33 releases the support pile 2 from its suspended state, and the crane 33 resumes suspending the pile driving device 34. The pile driving device 34, suspended by the crane 33, then applies vibration or impact to the head of the support pile 2, thereby driving the support pile 2 (2a) into the waterbed ground SB. While the support pile 2 is being driven, the pile guide unit 41 restricts horizontal movement of the support pile 2.

[0047] After completing the driving of the first support pile 2 (2a), which serves as a reference for positioning, the second moving mechanism 45 of the driving auxiliary device 40 is used to move the pile guide unit 41 above the upper end of the support pile 2 driven into the waterbed ground SB, thereby removing the pile guide unit 41 from the support pile 2 (2a). If the pile guide unit 41 is provided with an opening / closing unit 41a and a switching mechanism 41b, as in this embodiment, the opening / closing unit 41a can be opened by the switching mechanism 41b, and the pile guide unit 41 can be moved toward the SEP vessel 30 by the first moving mechanism 43 (actuator 44), thereby removing the pile guide unit 41 from the support pile 2.

[0048] Next, as illustrated in Figure 15, the movement mechanism 42 of the driving assist device 40 is used to position the pile guide unit 41 above the water at the planned driving position of the second support pile 2 (2b), which will serve as the positioning reference. In this embodiment, the movable platform 52 that constitutes the third movement mechanism 50 is moved in the X direction along the ship's longitudinal movement rail 51, so that the pile guide unit 41 is positioned at a distance L1 in the X direction from the first support pile 2a that has been driven into the waterbed ground SB. The opening / closing unit 41a of the pile guide unit 41 is kept in a closed state.

[0049] Then, similar to the driving operation of the first support pile 2a, the second support pile 2 loaded on the SEP vessel 30 is inserted into the pile guide unit 41, and the second support pile 2b is driven into the waterbed ground SB by the pile driving device 34. After the driving operation of the second support pile 2b is completed, the pile guide unit 41 is removed from the support pile 2b. Similarly, the movement mechanism 42 of the driving auxiliary device 40 is used to position the pile guide unit 41 on the water at the planned driving position of the third support pile 2 (2c), which will serve as the positioning reference. Then, the third support pile 2 is inserted into the pile guide unit 41, and the third support pile 2c is driven into the waterbed ground SB by the pile driving device 34. After the driving of the third support pile 2c is completed, the pile guide unit 41 is removed from the support pile 2c, and the pile guide unit 41 is stored on the barge main body 31. The above work completes the reference pile driving process for the pile driving work on the first voyage.

[0050] In the post-driving step of the subsequent pile driving work, as illustrated in Figures 16 and 17, the driving guide jig 20 loaded on the SEP vessel 30 is suspended by a crane 33. Then, the crane 33 is operated to move the driving guide jig 20 above the first to third support piles 2a to 2c, which serve as references for positioning the piles driven into the waterbed SB. In this embodiment, the driving guide jig 20 is suspended with the wire rope 33a of the crane 33 connected to the hoisting tool 26 attached to the driving guide jig 20.

[0051] Next, the driving guide jig 20 is lowered by the crane 33, and the support piles 2a to 2c, which serve as positioning references, are inserted into each of the three pile insertion sections 21 located on the SEP vessel 30 side. In this embodiment, a bottom expansion section 23 is provided below each pile insertion section 21, so that the support piles 2 can be guided into each pile insertion section 21 using the bottom expansion section 23 as a guide.

[0052] 18, the pouring guide jig 20 is lowered into the water so that it is placed on the water bottom ground SB. In this embodiment, by providing the pouring guide jig 20 with a subsidence suppression section 24, it is possible to prevent the pouring guide jig 20 from sinking into the water bottom ground SB even when the water bottom ground SB is soft. After the pouring guide jig 20 has been placed on the water bottom ground SB, the connection between the wire rope 33a of the crane 33 and the hoisting tool 26 is released, and the hoisting tool 26 is placed on the receiving tool 27.

[0053] By leaving the support piles 2a to 2c inserted through the three pile insertion portions 21 of the driving guide jig 20, the remaining three pile insertion portions 21 are arranged at the planned driving positions of the fourth to sixth support piles 2 (2d to 2f) to be driven subsequently. Also, by having the support piles 2a to 2c driven into the waterbed ground SB inserted through the three pile insertion portions 21, respectively, the horizontal movement of the driving guide jig 20 is restricted.

[0054] Next, as illustrated in Figures 18 and 19, the driving work of the fourth support pile 2 (2d) loaded on the SEP vessel 30 is carried out. In the driving work of the fourth support pile 2d, a crane 33 is used to move the fourth support pile 2d above the pile insertion section 21 into which the first to third support piles 2a to 2c have not yet been inserted. The fourth support pile 2d is then lowered so that the support pile 2d is inserted into the pile insertion section 21, and the lower end of the support pile 2d is placed on the waterbed ground SB. In this embodiment, the enlarged head section 22 is provided above the pile insertion section 21, and the support pile 2 (2d) can be guided into the pile insertion section 21 using the enlarged head section 22 as a guide. If necessary, the support pile 2 can be guided into the pile insertion section 21 using an ROV (remotely operated underwater vehicle) or seabed visual sonar, but since the pile insertion section 21 is positioned at the pre-planned installation position of the support pile 2, it is also possible to insert the support pile 2 into the expansion head section 22 and the pile insertion section 21 by guiding it on the water.

[0055] Next, a pile driving device 34 suspended by a crane 33 applies vibration or impact to the pile head of the support pile 2d, thereby driving the support pile 2d into the waterbed ground SB. While the support pile 2d is being driven, the horizontal movement of the support pile 2d is restricted by the pile insertion part 21. By performing similar operations, the fifth support pile 2e and the sixth support pile 2f are driven into the waterbed ground SB, as shown in Figure 20.

[0056] During the subsequent driving of the seventh support pile 2g, the crane 33 is used to move the driving guide jig 20 above the upper ends of the six support piles 2a-2f that have been driven into the waterbed SB, and the driving guide jig 20 is removed from the six support piles 2a-2f. Then, as shown in FIG. 20, the driving guide jig 20 is moved in the direction away from the SEP vessel 30 (Y direction), so that the already-driven fourth to sixth support piles 2d-2f are inserted into the three pile insertion sections 21 located on the SEP vessel 30 side, respectively, and the driving guide jig 20 is placed on the waterbed SB with the already-driven support piles 2 not inserted into the remaining three pile insertion sections 21. The pile insertion sections 21 that have not yet had a support pile 2 inserted are now positioned at the planned driving positions for the seventh to ninth support piles 2g-2i that will be driven next.

[0057] In the driving work of the seventh to ninth support piles 2g to 2i, similar to the driving work of the fourth to sixth support piles 2d to 2f, the seventh to ninth support piles 2g to 2i are driven into the waterbed ground SB with the pile insertion sections 21 inserted, respectively. Then, as shown in Figure 21, after the driving work of the seventh to ninth support piles 2g to 2i is completed, a crane 33 is used to remove the driving guide jigs 20 from the six support piles 2d to 2i, and the driving guide jigs 20 are placed on the barge body 31 of the SEP vessel 30. By performing the above post-driving process, the pile driving work for the first voyage of the SEP vessel 30 is completed, and a total of nine support piles 2 (2a to 2i) are installed in the construction waters, in three rows each in the X and Y directions.

[0058] When pile driving work is performed without using the driving auxiliary device 40, the planar position of the pile insertion portion 21 of the driving guide jig 20 is positioned to match the planned driving position of the support pile 2, and the driving guide jig 20 is placed on the water bottom ground SB. Then, the first support pile 2a is driven with the first support pile 2a inserted into one of the pile insertion portions 21 of the driving guide jig 20. Thereafter, the second support pile 2b and the third support pile 2c are driven with the support piles 2 inserted into the pile insertion portions 21 that the first support pile 2a has not yet passed through. Thereafter, the fourth and subsequent support piles 2d to 2i are driven using the same work procedure as in the post-driving process described above.

[0059] As illustrated in Figures 21 and 22, after the pile driving work is completed, pile head processing is performed to adjust the top height of each support pile 2 (2a-2i) driven into the waterbed ground SB. In pile head processing, leveling adjustment is performed to align the top heights of the support piles 2 (2a-2i), and then multiple support members 10 are attached to the inside of the pile head of each support pile 2 by welding or the like. In this embodiment, the support members 10 are attached radially in plan view to four locations on the pile head of each support pile 2. Then, using a crane 33 or the like, a top plate 9 is placed on the top ends of the support piles 2 and the support members 10, and the top plate 9 is joined to the support pile 2 by welding or the like. By performing pile head processing, the heights of the top ends (top plate 9) of the support piles 2 are aligned, and a level foundation is constructed on which the superstructure panel units 4 are installed.

[0060] In this embodiment, the outer dimensions (outer diameter) of the top plate 9 are set to be slightly larger than the outer diameter of the support pile 2. In this embodiment, a top plate 9 that is circular in plan view is used, but the shape of the top plate 9 is not particularly limited, and for example, a top plate 9 that is square in plan view may be used. The top plate 9 is made of, for example, a flat metal plate member, and the support member 10 is made of, for example, a metal plate-shaped member or rod-shaped member.

[0061] As illustrated in Figures 23 and 24, in the subsequent superstructure construction work, a crane 33 is used to move the superstructure panel unit 4 loaded on the SEP vessel 30 to above the multiple support piles 2 (2a to 2i) driven into the waterbed ground SB. The superstructure panel unit 4 is then lowered from above the support piles 2, and each of the support girders 8 that make up the superstructure panel unit 4 is placed on top of the multiple support piles 2. In this embodiment, the superstructure panel unit 4 extending across a total of nine support piles 2 arranged in three rows in each of the X and Y directions is placed on top of the nine support piles 2, and each of the three support girders 8 that make up the superstructure panel unit 4 is placed on top of three support piles 2.

[0062] In this embodiment, the support girders 8 that make up the superstructure panel units 4 are placed on the top plates 9 provided at the top ends of the respective support piles 2. The load of one set of superstructure panel units 4 is then supported by nine support piles 2. Thereafter, the superstructure panel units 4 are fixed to the respective support piles 2 (top plates 9) by welding, bolting, or the like, as necessary. In this embodiment, the support girders 8 and top plates 9 that make up the superstructure panel units 4 are joined by welding, thereby fixing the superstructure panel units 4 onto the support piles 2. With the above work, the superstructure construction work for the first voyage by the SEP vessel 30 is completed, and the construction of one section on the upper left of the page of the floating structure 1 illustrated in Figure 2 is completed.

[0063] In the second voyage, the SEP vessel 30 constructs two sections, one in the center and one on the right side of the upper part of the page, of the floating structure 1 illustrated in Fig. 2. As illustrated in Fig. 25, in the second voyage, the barge body 31 of the SEP vessel 30 is loaded with the support piles 2, superstructure panel units 4, top plates 9, and support members 10 used to construct the two sections of the floating structure 1. In this embodiment, 12 support piles 2, two sets of superstructure panel units 4, 12 top plates 9, and 48 support members 10 are loaded onto the barge body 31.

[0064] The SEP vessel 30 loaded with the materials described above is moved to the construction waters where the floating structure 1 will be constructed, and is parked in a jacked-up state near the positions where the 10th to 13th support piles 2j to 2m, which will serve as positioning references, will be driven. The materials to be newly loaded onto the SEP vessel 30 (support piles 2, superstructure panel units 4, top plate 9, and support members 10) may be transported by moving the SEP vessel 30 out of the construction waters, or the materials transported by another transport vessel may be transferred onto the SEP vessel 30 while the SEP vessel 30 is parked in the construction waters.

[0065] As shown in Figure 25, in the reference pile driving process for the pile driving work on the second voyage, the tenth support pile 2j, which serves as a positioning reference, is driven at a distance L1 in the X direction (to the right) from the first support pile 2a, using the auxiliary driving device 40 and pile driving device 34, in the same way as the first to third support piles 2a to 2c. Thereafter, as shown in Figure 26, the auxiliary driving device 40 and pile driving device 34 are used to sequentially drive the eleventh to thirteenth support piles 2k to 2m, which serve as positioning references. This completes the reference pile driving process for the pile driving work on the second voyage.

[0066] In the post-driving step of the subsequent pile driving work, the fourteenth to twenty-first support piles 2n to 2u are driven using a driving guide jig 20, as shown in Figure 26. Specifically, the driving guide jig 20 is arranged so that the pile insertion sections 21 are lined up in three rows in the Y direction and two rows in the X direction, and the tenth support pile 2j and the eleventh support pile 2k are inserted into the two pile insertion sections 21 located on the SEP vessel 30 side of the driving guide jig 20. Then, the fourteenth to seventeenth support piles 2n to 2q are driven using the four pile insertion sections 21 that have not yet been inserted with the support piles 2j and 2k.

[0067] The driving guide jig 20 is then moved in the X direction (to the right), and the twelfth support pile 2l and the thirteenth support pile 2m are inserted into the two pile insertion portions 21 located on the SEP vessel 30 side of the driving guide jig 20. Then, the eighteenth to twenty-first support piles 2r to 2u are driven using the four pile insertion portions 21 through which the support piles 2l and 2m have not yet been driven. By performing the above post-driving process, the pile driving work for the second voyage of the SEP vessel 30 is completed. A total of 12 support piles 2j to 2u are erected in the construction waters, in four rows in the X direction and three rows in the Y direction, next to one section of the floating structure 1 constructed in the first voyage. The ninth to twelfth support piles 2j to 2m can also be driven using the driving guide jig 20 without using the driving auxiliary device 40, for example.

[0068] As shown in Figure 27, after the pile driving work for the second voyage is completed, pile head processing is performed to adjust the top height of each of the support piles 2j to 2u that have been driven into the seabed ground SB. In the subsequent superstructure construction work, a crane 33 is used to install and secure a set of superstructure panel units 4 that were loaded on the SEP vessel 30 on top of the nine support piles 2 (2a, 2d, 2g, 2j, 2k, 2n to 2q) that have been driven next to the first section of the floating structure 1. This completes the construction of the second section of the floating structure 1.

[0069] Next, using a crane 33, another set of superstructure panel units 4 that had been loaded onto the SEP vessel 30 is installed and fixed onto the nine support piles 2 (2k, 2l, 2m, 2o, 2q to 2u) that have been driven into the ground next to the second section of the floating structure 1. This completes the construction of the third section of the floating structure 1. With the above work, the superstructure construction work for the second voyage by the SEP vessel 30 is complete.

[0070] In the third voyage, the SEP vessel 30 constructs the three sections of the floating structure 1 shown in the lower part of the drawing. As shown in FIG. 28, in the third voyage, the support piles 2, superstructure panel units 4, top plates 9, and support members 10 used to construct the three sections of the floating structure 1 are loaded onto the barge body 31 of the SEP vessel 30. In this embodiment, 14 support piles 2, three sets of superstructure panel units 4, 14 top plates 9, and 56 support members 10 are loaded onto the barge body 31. The SEP vessel 30 loaded with the materials described above is moved to the construction waters where the floating structure 1 will be constructed, and the SEP vessel 30 is stopped in a jacked-up state near the positions where the 22nd to 24th support piles 2v to 2x, which will serve as the positioning reference, will be driven, with the crane 33 positioned on the floating structure 1 side.

[0071] Then, as shown in Figure 28, in the reference pile driving process for the pile driving work on the third voyage, the 22nd to 24th support piles 2v to 2x, which will serve as references for positioning, are driven using the auxiliary driving device 40 and pile driving device 34 in the same way as the 1st to 3rd support piles 2a to 2c were driven. With the above work, the reference pile driving process for the pile driving work on the third voyage is completed.

[0072] In the post-driving step of the subsequent pile driving work, the 24th to 35th support piles 2 are driven using a driving guide jig 20, as illustrated in Figure 29. Specifically, the driving guide jig 20 is arranged so that the pile insertion sections 21 are lined up in two rows in the Y direction and three rows in the X direction, and the 22nd to 24th support piles 2v to 2x are inserted into the three pile insertion sections 21 located on the SEP vessel 30 side of the driving guide jig 20. Then, the 25th to 27th support piles 2 are driven using the three pile insertion sections 21 through which the support piles 2v to 2x have not been inserted.

[0073] Thereafter, the driving guide jig 20 is moved to the left of the 22nd support pile 2v, and with two support piles 2 inserted into the two pile insertion portions 21 on the right side of the driving guide jig 20, the 28th to 31st support piles 2 are driven using the four pile insertion portions 21 through which no support piles 2 are inserted. Next, the driving guide jig 20 is moved to the right of the 24th support pile 2x, and with two support piles 2 inserted into the two pile insertion portions 21 on the left side of the driving guide jig 20, the 32nd to 35th support piles 2 are driven using the four pile insertion portions 21 through which no support piles 2 are inserted.

[0074] By carrying out the above post-casting process, the pile driving work for the third voyage of the SEP vessel 30 is completed. A total of 14 support piles 2 are erected in the construction waters below the three sections of the floating structure 1 constructed in the first and second voyages, with seven rows in the X direction and two rows in the Y direction. Note that the 22nd to 24th support piles 2v to 2x can also be driven using the driving guide jig 20 without using the driving auxiliary device 40, for example.

[0075] As shown in Figure 30, after the pile driving work for the third voyage is completed, pile head processing is performed to adjust the height of the top end of each support pile 2 driven into the seabed ground SB. In the subsequent superstructure construction work, a crane 33 is used to install and fix the superstructure panel units 4 loaded on the SEP vessel 30 on top of the nine support piles 2 driven into the underside of the first section of the floating structure 1, the nine support piles 2 driven into the underside of the second section, and the nine support piles 2 driven into the underside of the third section.

[0076] The above work completes the construction of the six sections of the floating structure 1. In this embodiment, the support girders 8 of the superstructure panel units 4 that make up each section are placed adjacent to each other on the support piles 2 located on the boundaries of adjacent sections of the floating structure 1.

[0077] For example, when the floating structure 1 is used as a temporary floating structure 1 for temporarily placing and assembling assembly parts of a wind power generation device to be used in the construction of a floating offshore wind power generation facility, mooring equipment and protective equipment can be installed near the floating structure 1 so that a transport ship carrying the assembly parts of the wind power generation device can dock at the floating structure 1.

[0078] When the use of the offshore structure 1 is finished and it is to be removed, the support piles 2 (top plate 9) are disconnected from the superstructure panel units 4, and each superstructure panel unit 4 is detached from the support piles 2 using a crane 33 or the like of the SEP vessel 30. Then, each support pile 2 is extracted from the waterbed ground SB using a crane 33 or the like of the SEP vessel 30, and the holes in the waterbed ground SB where the support piles 2 were inserted are backfilled, restoring the waterbed ground SB to its state before the construction of the offshore structure 1. The removed support piles 2 and superstructure panel units 4 can be reused when constructing an offshore structure 1 in another construction water area. In other words, the offshore structure 1 can be moved to a different location and reinstalled and removed many times in a relatively short period of time.

[0079] As described above, in the method for constructing this floating structure 1, in the pile driving work, a driving guide jig 20 having a plurality of pile insertion sections 21 arranged at intervals (L1, L2) from each other in a plan view is placed on the water bottom ground SB, and a plurality of support piles 2 are driven into the water bottom ground SB using the pile insertion sections 21 as guides. Because the driving of the support piles 2 can be performed with the horizontal movement of the support piles 2 restricted by the pile insertion sections 21, the driving of the support piles 2 can be performed using the plurality of pile insertion sections 21 of the driving guide jig 20, allowing the plurality of support piles 2 to be driven with high precision in a pre-planned arrangement.

[0080] In the superstructure construction work, a superstructure panel unit 4 is fabricated in advance, which includes a floor structure 5 extending over multiple support piles 2 and multiple support girders 8 arranged at intervals (L1) from each other in a plan view below the floor structure 5. In other words, the superstructure panel units 4 are fabricated in advance to match the pre-planned arrangement of the support piles 2. As a result, in the construction waters, it is possible to construct a superstructure 3 extending over multiple support piles 2 simply by erecting each of the support girders 8 that make up the superstructure panel unit 4 on top of the multiple support piles 2 and fixing the superstructure panel units 4 to the top of the multiple support piles 2.

[0081] This construction method uses a driving guide jig 20 to accurately drive multiple support piles 2 in a pre-planned arrangement, preventing misalignment between the support girders 8 that make up the pre-fabricated superstructure panel units 4 and the support piles 2. Therefore, this construction method reduces the labor hours required to construct the offshore structure 1 in the construction waters, allowing for efficient construction of the offshore structure 1. This construction method eliminates the need for steel frame assembly work or diving work at the water's edge, making it possible to construct and remove the offshore structure 1 in a short period of time, even in relatively deep waters (e.g., between 8 and 20 meters deep) or in waters with severe wave conditions. It also makes it possible to reuse (reuse) the components that make up the offshore structure 1 multiple times.

[0082] Furthermore, in this construction method, the support piles 2 are driven while inserted into the pile insertion portions 21 of the driving guide jig 20, thereby preventing the support piles 2 from being driven in an inclined state or from wobbling during driving. Therefore, even when the waterbed ground SB is relatively soft, the support piles 2 can be driven with precision in the correct orientation. This is therefore extremely advantageous in preventing misalignment between the support girders 8 that make up the superstructure panel unit 4, which have been fabricated in advance, and the pile heads of the support piles 2 driven into the waterbed ground SB.

[0083] Although not provided in the concrete pouring guide jig 20 of this embodiment, for example, the concrete pouring guide jig 20 may be provided with a height adjustment mechanism that enables the relative height positions of the lower ends of the pile insertion portions 21 (subsidence suppression portions 24) to be changed. By providing the height adjustment mechanism described above, even when the concrete pouring guide jig 20 is placed on an undulating or sloping water bottom ground SB, it becomes possible to place each pile insertion portion 21 on the water bottom ground SB without tilting by adjusting the height position of the lower ends of the pile insertion portions 21 to match the topography of the water bottom ground SB.

[0084] As in this embodiment, in pile driving work, the SEP vessel 30, which has lifting legs 32, a barge body 31, and a crane 33, is stopped in a jacked-up state with the lifting legs 32 resting on the bottom of the water SB. Then, by using a pile driving device 34 suspended by the crane 33 to drive the support piles 2 into the bottom of the water SB, pile driving work can be efficiently performed in a stable state free from the influence of waves. Furthermore, in superstructure construction work, by using the crane 33 to install the superstructure panel units 4 placed on the barge body 31 of the SEP vessel 30 on top of the multiple support piles 2, superstructure construction work can be efficiently performed in a stable state free from the influence of waves. The construction method using the SEP vessel 30 is particularly suitable for constructing an offshore structure 1 in waters with a water depth D1 of 8 m or more and 40 m or less.

[0085] As in this embodiment, in the reference pile driving step in pile driving work, the SEP vessel 30 is stopped in a jacked-up state, and the pile guide section 41 of the driving auxiliary device 40 mounted on the barge body 31 of the SEP vessel 30 is positioned outside the barge body 31. Then, when the support pile 2 serving as the positioning reference is inserted into the pile guide section 41 and driven into the waterbed ground SB, the support pile 2 serving as the positioning reference can be driven efficiently and accurately into the pre-planned driving position. In the post-driving step following the reference pile driving step in pile driving work, the driving guide jig 20 is lowered from above the support pile 2 serving as the positioning reference, and the driving guide jig 20 is positioned on the waterbed ground SB with the support pile 2 serving as the positioning reference inserted into one of the pile insertion sections 21. Then, by using the other pile insertion portions 21 into which the support pile 2 serving as the positioning reference has not been inserted as guides, the support piles 2 other than the support pile 2 serving as the positioning reference are driven at intervals (L1, L2) from each other in a plan view, and the support piles 2 other than the support pile 2 serving as the positioning reference can also be driven with precision in a pre-planned arrangement.

[0086] Furthermore, as in this embodiment, in the reference pile driving step, a plurality of support piles 2 that serve as positioning references are driven using the driving auxiliary device 40. Then, in the post-driving step, if the driving guide jig 20 is placed on the water bottom ground SB with the support piles 2 that serve as positioning references inserted into two or more pile insertion portions 21, respectively, the driving guide jig 20 does not rotate horizontally in the process of placing the driving guide jig 20 on the water bottom ground SB, and the pile insertion portions 21 that have not had a support pile 2 inserted therein can be easily and accurately positioned at the pre-planned driving positions of the support piles 2.

[0087] In this construction method, for example, one support pile 2 serving as a positioning reference can be driven, and the second support pile 2 can be driven in a state in which the support pile 2 serving as a positioning reference is inserted into one pile insertion portion 21 constituting the driving guide jig 20. In this case, since there is a possibility that the driving guide jig 20 will rotate horizontally in the process of placing the driving guide jig 20 on the waterbed ground SB, it is preferable to configure the driving guide jig 20 to be guided by an ROV, seabed visual sonar, or the like so that the pile insertion portion 21 into which the support pile 2 is not inserted is placed in the preplanned driving position for the support pile 2.

[0088] In this construction method, for example, the support pile 2 serving as the positioning reference can be driven using the driving auxiliary device 40 and the driving guide jig 20. In this case, the driving guide jig 20 is placed on the bottom ground SB, and the support pile 2 serving as the positioning reference is driven with the pile guide portion 41 of the driving auxiliary device 40 and the pile insertion portion 21 of the driving guide jig 20. In this case, the support pile 2 serving as the positioning reference can be driven with high precision at the pre-planned driving position of the support pile 2. However, by using only either the driving auxiliary device 40 or the driving guide jig 20, the support pile 2 serving as the positioning reference can be driven with high precision at the pre-planned driving position of the support pile 2. Therefore, when using the driving auxiliary device 40 in the reference pile driving process, it is recommended to perform the reference pile driving process using only the driving auxiliary device 40 without using the driving guide jig 20 within the reach of the driving auxiliary device 40. It is advisable to use the casting guide jig 20 in the post-casting step.

[0089] As in this embodiment, when a casting guide jig 20 is used in which two rows of pile insertion portions 21 are arranged in the front-to-back direction when viewed from above and three rows of pile insertion portions 21 are arranged in the left-to-right direction, the size of the casting guide jig 20 does not become excessive, and it becomes easier to align each pile insertion portion 21 of the casting guide jig 20 with the support piles 2 cast into the waterbed ground SB.

[0090] In this construction method, for example, it is possible to use a casting guide jig 20 in which the pile insertion sections 21 are arranged in two rows in the front-to-back direction in a plan view and in two rows in the left-to-right direction, or a casting guide jig 20 in which the pile insertion sections 21 are arranged in three locations, but in such cases the casting guide jig 20 will have four or three pile insertion sections 21. Therefore, compared to using a casting guide jig 20 having six pile insertion sections 21 as exemplified in the above-mentioned embodiment, there is a disadvantage in that the casting guide jig 20 needs to be moved more frequently.

[0091] In this construction method, for example, it is possible to use a driving guide jig 20 having seven or more pile insertion portions 21. However, if the number of pile insertion portions 21 is seven or more, the size of the driving guide jig 20 becomes excessively large, making it difficult to secure space on the SEP vessel 30 to load the driving guide jig 20. Another disadvantage is that it becomes difficult to align each pile insertion portion 21 of the driving guide jig 20 with the support piles 2 driven into the bottom ground SB. Therefore, it is preferable to use a driving guide jig 20 having two rows of pile insertion portions 21 arranged in the front-to-back direction and three rows of pile insertion portions 21 arranged in the left-to-right direction in a plan view, as in the above-described embodiment.

[0092] If an I-beam with a height of 700 mm to 2000 mm and a width of 300 mm to 800 mm is used as the support girders 8 that make up the superstructure panel units 4, the load-bearing capacity of the support girders 8 can be made higher than when H-beams are used as the support girders 8, and therefore the spacing (L2) between the support piles 2 on which the support girders 8 are erected can be set to a very long span of, for example, 10 m to 30 m. Therefore, using an I-beam that meets the above-mentioned dimensional conditions as the support girders 8 is advantageous for reducing the number of support piles 2 that make up the offshore structure 1 and the number of members that make up the superstructure panel units 4, and is advantageous for reducing the number of work steps and construction costs required to build the offshore structure 1.

[0093] Figure 31 shows an example of an offshore structure 1 according to another embodiment constructed by the construction method of the present invention. In this embodiment, the offshore structure 1 is configured such that one support girder 8 constituting the superstructure 3 is installed for each support pile 2. Specifically, when a support girder 8 is installed at the other end (e.g., right end) of one superstructure panel unit 4 (e.g., left side) that is installed adjacent to the other in the X direction, no support girder 8 is installed at one end (e.g., left end) of the other superstructure panel unit 4 (e.g., right side). Even with this configuration, a stable offshore structure 1 can be constructed by placing the floor structure 5 (girders 6) constituting the other superstructure panel unit 4 on top of the support girder 8 installed at the other end of the one superstructure panel unit 4.

[0094] In the embodiment exemplified above, a case was illustrated in which superstructure panel units 4 were used that extended across a total of nine support piles 2, three rows in each of the X and Y directions, but it was also possible to use superstructure panel units 4 that extended across four or more rows of support piles 2 in at least either the X or Y direction. It was also possible to use superstructure panel units 4 that extended across two rows of support piles 2 in at least either the X or Y direction.

[0095] Increasing the size of the superstructure panel units 4 is advantageous in reducing the man-hours required for installing the superstructure panel units 4. On the other hand, increasing the size of the superstructure panel units 4 also increases the weight of the superstructure panel units 4, which requires securing a large space on the SEP vessel 30 to accommodate the superstructure panel units 4, which may make it difficult to load the superstructure panel units 4 onto the SEP vessel 30. Increasing the size of the superstructure panel units 4 also makes it difficult to align the support girders 8 with the support piles 2 when installing the superstructure panel units 4 relative to the support piles 2 driven into the bottom ground SB. Therefore, it is preferable to use superstructure panel units 4 that extend across a total of nine support piles 2, arranged in three rows in each of the X and Y directions, as in the above-described embodiment.

[0096] The number and arrangement of the support piles 2 and superstructure panel units 4 loaded on the SEP vessel 30 are not limited to those in the above-described embodiment, and can be determined appropriately depending on the sizes of the SEP vessel 30, the support piles 2, and the superstructure panel units 4. As in the above-described embodiment, it is preferable to use the SEP vessel 30 in this construction method, but it is also possible to perform pile driving work and superstructure construction work using, for example, a crane vessel other than the SEP vessel 30. Furthermore, when constructing the floating structure 1 near an existing floating structure or a quay, it is also possible to perform pile driving work and superstructure construction work using a crane placed on the existing floating structure or the quay.

[0097] In the above-described embodiment, an example has been given of constructing an overwater structure 1 that is rectangular in plan view, but this construction method can also be used to construct overwater structures 1 that have other planar shapes, such as an L-shape or a cross shape in plan view. The number and arrangement of the support piles 2 that make up the overwater structure 1 are not limited to the above-described embodiment, and various other configurations are possible. Furthermore, the positions and number of support piles 2 that serve as positioning references, the order in which the support piles 2 are driven, and the like are not limited to the above-described embodiment, and can be determined appropriately depending on the number and arrangement of the support piles 2 that make up the overwater structure 1. [Explanation of symbols]

[0098] 1 floating structures 2, 2a~2u support pile 3 Superstructure 4 Superstructure panel unit 5 floor structure 6 girder material 7 Floor slab 7a Lining board 8 Receiving beam 9. Top plate 10 Support member 20 Concrete guide jig 21 Pile insertion part 22 Head enlargement 23 Enlarged base 24 Subsidence control section 25 Connecting part 26 Hanging equipment 27 Receiver 30 Self-elevating platform (SEP) 31 Barge body 32 Lifting legs 33 Crane 33a Wire Rope 34 Pile driving equipment 40 Concrete pouring auxiliary device 41 Pile guide section 41a Opening / closing part 41b Switching mechanism 42 Moving mechanism 43 1st movement mechanism 44 Actuator 44a cylinder 44b Rod 45 Second movement mechanism 46 Rotating part 47 Lifting section 48 Support part 49 Lifting guide 50 Third movement mechanism 51 Rail for moving in the captain's direction 52 Movable platform SB underwater ground WL water surface position

Claims

1. A method for constructing an offshore structure in which a plurality of support piles are erected in the waterbed ground and a superstructure is constructed on top of the plurality of support piles, thereby constructing an offshore structure in which the plurality of support piles and the superstructure are integrated, In the pile driving work, a driving guide jig having a plurality of pile insertion portions arranged at intervals from each other in a plan view is placed on the bottom ground, and the plurality of support piles are driven into the bottom ground at intervals from each other in a plan view using the pile insertion portions as guides, In the superstructure construction work, a superstructure panel unit having a floor structure extending across a plurality of the support piles and a plurality of support girders arranged at intervals from each other in a plan view below the floor structure is prepared in advance, and each of the support girders that make up the superstructure panel unit is erected on top of a plurality of the support piles, and the superstructure is constructed by fixing the superstructure panel unit to the top of the plurality of the support piles.This method for constructing an overwater structure is characterized by the above.

2. In the pile driving work, a self-lifting barge having lifting legs, a barge body that can be raised and lowered relative to the lifting legs, and a crane mounted on the barge body is stopped in a jacked-up state with the lifting legs touching the bottom of the water, and the support piles are driven into the waterbed using a pile driving device suspended by the crane, A method for constructing an offshore structure as described in claim 1, wherein during the superstructure construction work, the superstructure panel unit placed on the barge body is installed on top of multiple support piles using the crane.

3. A method for constructing an offshore structure in which a plurality of support piles are erected in the waterbed ground and a superstructure is constructed on top of the plurality of support piles, thereby constructing an offshore structure in which the plurality of support piles and the superstructure are integrated, In the reference pile driving process for driving the support pile that serves as a reference for positioning in the pile driving work, a self-elevating barge having lifting legs, a barge body that can be raised and lowered relative to the lifting legs, and a crane mounted on the barge body is stopped in a jacked-up state with the lifting legs resting on the bottom of the water, and a driving auxiliary device equipped with a pile guide section through which the support pile is inserted and a movement mechanism for moving the pile guide section relative to the barge body is mounted on the barge body, and the pile guide section is positioned outside the barge body by the movement mechanism, and the support pile that serves as a reference for positioning is inserted into the pile guide section, and then the support pile that serves as a reference for positioning is driven into the bottom of the water, In the post-driving process of driving other support piles after the reference pile driving process in the pile driving work, the self-lifting barge is stopped in the jacked-up state, and a driving guide jig having a plurality of pile insertion portions arranged at intervals from each other in a planar view is lowered from above the support pile that is to be used as a reference for positioning, and the driving guide jig is placed on the bottom ground with the support pile that is to be used as a reference for positioning inserted into one of the pile insertion portions, and the other pile insertion portions into which the support pile that is to be used as a reference for positioning is not inserted are used as guides to drive the support piles other than the support pile that is to be used as a reference for positioning at intervals from each other in a planar view, In the superstructure construction work, a superstructure panel unit having a floor structure extending across a plurality of the support piles and a plurality of support girders arranged at intervals from each other in a plan view below the floor structure is prepared in advance, and the superstructure panel unit placed on the barge body is then placed on top of the plurality of support piles that have been driven into the bottom ground using the crane, so that each of the support girders that make up the superstructure panel unit is erected on top of the plurality of support piles, and the superstructure is constructed by fixing the superstructure panel unit to the top of the plurality of support piles.

4. A method for constructing an above-water structure as described in claim 3, wherein in the reference pile driving process, the driving auxiliary device is used to drive multiple support piles that serve as positioning references, and in the post-driving process, the driving guide jig is placed on the bottom ground with the support piles that serve as positioning references inserted into two or more pile insertion portions.

5. A method for constructing an aquatic structure according to any one of claims 1 to 4, wherein the pile insertion portions are arranged in two rows in the front-to-back direction in a plan view and in three rows in the left-to-right direction, using the driving guide jig.

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