Construction methods

Abstract

To provide a construction method capable of efficiently surveying piles. [Solution] A construction method 1 for constructing an offshore structure 20 supported by piles 10 comprises a first survey tower placement step of placing a survey tower 30 at a first position P1 on the sea S, and a second survey tower placement step of moving the survey tower 30 from the first position P1 and placing the survey tower 30 at a second position P2 on the sea S.

Description

[Technical Field]

[0001] The present disclosure relates to an installation method. [Background technology]

[0002] When constructing marine structures in offshore construction work, the construction status of the marine structures is surveyed. Patent Document 1 discloses a surveying system that uses a total station and a GPS to measure the driving position of a steel pipe pile. In Patent Document 1, the steel pipe pile is sighted using a plurality of total stations. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-14877 Summary of the Invention [Problem to be solved by the invention]

[0004] When multiple steel pipe piles are installed at sea, the installation status is surveyed for each installation location of the steel pipe pile. In the surveying system of Patent Document 1, when multiple steel pipe piles are installed at sea, a surveying system is constructed for each installation location of the steel pipe pile, which takes time and effort and is inefficient.

[0005] The present disclosure aims to provide a construction method that can efficiently survey piles. [Means for solving the problem]

[0006] A construction method according to one aspect of the present disclosure is a construction method for constructing an offshore structure supported by piles, and includes a first survey tower placement step of placing a survey tower at a first position on the sea, and a second survey tower placement step of moving the survey tower from the first position and placing the survey tower at a second position on the sea. [Effects of the Invention]

[0007] According to the present disclosure, piles can be efficiently surveyed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram illustrating a construction method according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram for explaining a method for surveying piles. [Figure 3] FIG. 3 is a schematic diagram showing the manner in which the survey tower is transported. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Note that the drawings are schematic for easy understanding, and the dimensions and proportions of each component may be changed as appropriate.

[0010] A construction method 1 according to this embodiment will be described with reference to FIGS. 1 to 3. FIG. Fig. 1 is a schematic diagram of a construction method 1 according to this embodiment, viewed from a vertical direction. Fig. 2 is a schematic diagram of a pile surveying method, viewed from a horizontal direction. Fig. 3 is a schematic diagram showing how a survey tower 30 is transported.

[0011] Construction method 1 is a method for constructing an offshore structure 20 supported by piles 10. The piles 10 are, for example, steel pipe piles. In FIG. 1, the offshore structure 20 supported by the piles 10 is constructed at a first construction position X1 on the sea S.

[0012] The pile 10 is made of steel and has a cylindrical shape. The pile 10 is driven vertically into the ground on the seabed Sa. The pile 10 is suspended, for example, by a crane 51 provided on a crane ship 50, and after the lower part of the pile 10 is sunk into the seabed Sb, it is driven into the ground.

[0013] The marine structure 20 is supported by piles 10. FIG. 1 illustrates a configuration in which the marine structure 20 is supported by four piles 10 (10A, 10B, 10C, 10D). The number of piles 10 is not limited to four. The number of piles 10 may be, for example, one to three, or five or more. In the embodiment shown in FIG. 1, the marine structure 20 is a fixed-bottom foundation that supports a wind turbine for an offshore power generator. FIG. 1 illustrates a case in which the fixed-bottom foundation is a jacket type. The fixed-bottom foundation may also be a monopile type having a single pile 10.

[0014] The survey tower 30 is an offshore scaffolding used to survey piles in offshore construction work. The survey tower 30 is made of steel and mainly includes a bottom slab (mud mat) 31, a frame member 32, and a stage 33. The bottom slab 31 is a member provided at the lower end of the frame member 32, and is in contact with the seabed Sa. The frame member 32 extends in the vertical direction, and a stage 33 can be installed on it. The stage 33 is provided horizontally at the upper end of the frame member 32. The stage 33 is a work area where an operator (not shown) performs surveying, and is located in the air AR. In addition to the stage 33 (33A) provided at the upper end of the frame member 32, another stage 33 (33B) may be provided on the frame member 32.

[0015] The survey tower 30 is assembled and disassembled, for example, near a quay or in a manufacturing factory. The survey tower 30 is assembled by, for example, using an aerial work platform (not shown) or a crane (not shown) to assemble frame members 32 onto a bottom slab 31 that has been assembled on the ground, and then attaching a stage 33 to the upper end of the frame member 32. The assembled survey tower 30 is transported to the sea S by a crane barge 50 and installed at a predetermined position on the seabed Sa. Alternatively, the assembled survey tower 30 may be transported by a barge (not shown).

[0016] <Construction method> In this embodiment, marine structures 20 are constructed at multiple locations on the sea S. In FIG. 1, the marine structure 20 is constructed at a first construction position X1 on the sea S. In this embodiment, a case will be described in which, after the marine structure 20 is constructed at the first construction position X1, a marine structure 20-1 (20) is also constructed at X2 (second construction position) indicated by a two-dot chain line in FIG. 1. In FIG. 1, the piles 10-1 and the marine structure 20-1 constructed at the second construction position X2 are indicated by a two-dot chain line. In FIG. 1, a configuration in which the marine structure 20-1 is supported by four piles 10-1 (10-1A, 10-1B, 10-1C, 10-1D) is illustrated as an example. However, like the piles 10 constructed at the first construction position X1, the number of piles 10-1 is not limited to four. The number of piles 10-1 may be, for example, one to three, or may be five or more. In Figure 1, the construction locations of the marine structure 20 (20-1) are shown as two locations, the first construction position X1 and the second construction position X2, but the number of construction locations of the marine structure 20 is not limited to two. The marine structure 20 may be constructed at three or more locations.

[0017] Construction method 1 according to this embodiment includes a first survey tower placement step, a first pile driving step, a second survey tower placement step, and a second pile driving step. Construction method 1 is carried out in the order of the first survey tower placement step, the first pile driving step, the second survey tower placement step, and the second pile driving step.

[0018] <First survey tower placement step> The first survey turret placement step is a step of placing the survey turret 30 at a first position P1 on the sea S. In the first survey turret placement step, for example, the survey turret 30 assembled near a quay is transported to the first position P1 by a ship (e.g., a crane ship 50). The exact position of the first position P1 is measured using a GPS or the like after the survey turret 30 is placed. The first position P1 is a position from which a worker working on the stage 33 of the survey turret 30 can sight the pile 10 placed at the first construction position X1. The distance between the first position P1 and the first construction position X1 is, for example, 10 m to 150 m.

[0019] <Second survey tower placement step> After surveying the piles 10 installed at the first installation position X1 in the first survey tower placement step, the survey tower 30 is moved from the first position P1 to the second position P2. In Figure 1, the survey tower 30-1 installed at the second position P2 is shown by a two-dot chain line. The second survey tower placement step is a step in which the survey tower 30 is moved from the first position P1 and the survey tower 30-1 (30) is placed at a second position P2 on the sea S. The exact position of the second position P2 is measured using a GPS or the like after the survey tower 30-1 is placed. The second position P2 is a position from which a worker working on the stage 33 of the survey tower 30-1 can sight the pile 10-1 placed at the second construction position X2. The distance between the second position P2 and the second construction position X2 is, for example, 10 m to 150 m.

[0020] Construction method 1 is configured to move the survey turret 30 from a first position P1 to a second position P2. As a result, when constructing the marine structure 20 at multiple locations, the survey turret 30 is moved to each location where the marine structure 20 is constructed to survey each pile 10, eliminating the need to manufacture a new survey turret 30. For example, when constructing the marine structure 20 (20-1) at two locations, a first construction position X1 and a second construction position X2, there is no need to manufacture two survey turrets 30 to survey the piles 10 (10-1) at two locations. When surveying piles 10 (10-1) at two locations, the first pile 10 can be surveyed with the survey turret 30, and then the survey turret 30 can be moved to survey the second pile 10-1. As described above, according to the construction method 1 of this embodiment, when constructing the marine structure 20 (20-1) at multiple locations, the survey turret 30 (30-1) can be moved to survey the piles 10 (10-1) at each location from the survey turret 30 (30-1). Therefore, the construction method 1 can efficiently survey the piles 10 (10-1).

[0021] <First pile driving step> Construction method 1 includes a first pile driving step of driving a pile 10, which is surveyed from a survey turret 30 located at a first position P1, into the seabed Sa. In the first pile driving step, as shown in FIG. 1, the pile 10 is installed at a first installation position X1 on the sea S. The predetermined first installation position X1 is accurately determined using, for example, a GPS or a total station. The first pile driving step is performed after the first survey turret placement step.

[0022] <Second pile driving step> After the survey tower 30-1 is placed at the second position P2 in the second survey tower placement step, the pile 10 is driven into the second construction position X2. In FIG. 1, the second construction position X2 is indicated by a two-dot chain line. Construction method 1 includes a second pile driving step in which the pile 10-1, which is measured from the survey tower 30-1 located at the second position P2, is driven into the seabed Sa. The predetermined second construction position X2 is accurately determined using, for example, a GPS or a total station. The second pile driving step is executed after the second survey tower placement step.

[0023] In the first pile driving step and the second pile driving step, the pile 10 is driven by a vibro hammer, a hydraulic hammer, or the like (not shown). The vibro hammer, hydraulic hammer, or the like is provided, for example, on a crane 51 of a crane ship 50. The vibro hammer, hydraulic hammer, or the like supports the pile head 11 of the pile 10 (or a temporary pile 15, which will be described later), and the pile 10 is lowered in the vertical direction. The pile 10 is driven vertically into the ground of the seabed Sa by the vibration of the vibro hammer, hydraulic hammer, or the like.

[0024] A worker surveys the piles 10 from the stage 33 of the survey tower 30 (pile surveying step). That is, the construction method 1 includes a pile surveying step for surveying the piles 10. This surveying is, for example, a transit surveying. If the pile head 11 of the pile 10 is located above sea level Sc (air AR), the pile head 11 of the pile 10 is surveyed in the pile surveying step. Specifically, for example, the verticality of the pile 10 and the pile head elevation of the pile head 11 are surveyed. Markings are made on the pile 10, and an operator conducts the survey by aiming at the markings. The pile 10 may be provided with a temporary pile (so-called pliers) 15. The temporary pile 15 is connected to the pile head 11 of the pile 10 and is used to drive the pile 10 into the seabed Sa. The temporary pile 15 is removed from the pile head 11 once the pile 10 has been driven to a predetermined depth. Figure 3 shows a case in which the temporary pile 15 is connected to the pile head 11 of the pile 10. As shown in Figure 2, the upper end 16 of the temporary pile 15 is located above the sea level Sc (air AR). If the pile 10 is provided with a temporary pile 15, the pile surveying step surveys the temporary pile 15 of the pile 10. Specifically, for example, the verticality of the temporary pile 15 and the pile head elevation of the upper end 16 of the temporary pile 15 are surveyed. Markings are made on the temporary pile 15, and the worker surveys by aiming at the markings.

[0025] In the second survey tower placement step, the survey tower 30 may be moved by a ship. Specifically, the survey tower 30 may be moved by a crane ship 50 for driving the piles 10. FIG. 3 shows an example of a mode in which the survey tower 30 is transported by a crane ship 50. The upper end of the survey tower 30 is lifted by a crane 51 of the crane ship 50. At this time, it is preferable to lift the survey tower 30 by the crane 51 so that the lower end (e.g., the slab 31) of the survey tower 30 is positioned above the sea surface Sc (in the air AR). If the survey tower 30 is moved with its lower end positioned in the sea Sb, it will be subjected to resistance from seawater and waves, causing the survey tower 30 to sway, which is undesirable. In this way, by using the crane ship 50 used for driving the piles 10 to move the survey turret 30, there is no need to prepare a ship separate from the crane ship 50.

[0026] Alternatively, the survey tower 30 may be moved by a ship other than the crane ship 50 for driving the piles 10. The other ship may be, for example, a barge (not shown) or a self-propelled ship (not shown). In this way, by using a vessel other than the crane ship 50 used to drive the piles 10 to move the survey turret 30, the crane ship 50 does not need to be used for a long period of time.

[0027] <Preparation steps> The height (m) of the survey tower 30 is determined taking into consideration the water depth at the location where the survey tower 30 is installed. The height of the survey tower 30 is the length in the vertical direction from the bottom end of the survey tower 30 (e.g., the base 31) to the top end of the survey tower 30 (e.g., the stage 33). When the water depth at the first position P1 and the water depth at the second position P2 are approximately the same, survey turrets 30 of the same height are used. On the other hand, when the water depth at the first position P1 and the water depth at the second position P2 are different, it is preferable to use survey turrets 30 of different heights. In this way, construction method 1 may include a preparation step of preparing multiple survey turrets 30 of different heights.

[0028] <Selection Step> If the difference in water depth between the first position P1 and the second position P2 is small, survey turrets 30 of the same height may be used. In this way, construction method 1 may include a selection step for selecting the survey turret 30 to be used from a plurality of survey turrets 30 depending on the water depth. The selection of survey turrets 30 of the same height or different heights is determined by taking into consideration, in addition to the water depth at the position where the survey turret 30 is to be installed, factors such as wave height and the amount of sinking of the bottom slab 31 into the seabed Sa.

[0029] In this way, by providing the construction method 1 with a preparation step and a selection step, it is possible to use a plurality of survey turrets 30 depending on the water depth.

[0030] 1 is a bottom-fixed foundation that supports a wind turbine for offshore power generation. A plurality of such bottom-fixed foundations may be provided in the same wind farm or sea area.

[0031] When multiple bottom-fixed foundations are installed in the same wind farm or sea area, the survey tower 30 can be reused.

[0032] FIG. 1 shows a case where the bottom-fixed foundation is a jacket type. In this case, the bottom-fixed foundation is supported by multiple piles 10. In FIG. 1, four piles 10 (10A, 10B, 10C, and 10D) support an offshore structure 20. Multiple piles 10 may be surveyed from a survey turret 30 located at the same location. For example, as shown in FIG. 1, four piles 10 (10A, 10B, 10C, and 10D) are surveyed from a survey turret 30 located at a first position P1. Similarly, for example, four piles 10-1 (10-1A, 10-1B, 10-1C, and 10-1D) are surveyed from a survey turret 30-1 located at a second position P2.

[0033] If the survey tower 30 is placed at a position corresponding to the fixed foundation, the survey of the plurality of piles 10 (10A, 10B, 10C, 10D) can be carried out from the survey tower 30 at that position.

[0034] In addition to surveying from the survey tower 30, the pile 10 may be surveyed from a position other than the survey tower 30 (additional survey position M1). That is, the pile 10 may be surveyed from two different positions. For example, the pile 10 may also be surveyed from a ship located at a position other than the survey tower 30 or from a survey tower other than the survey tower 30. For example, as shown in FIG. 1 , the pile 10 may be surveyed from an additional survey position M1 on a crane ship 50 in addition to surveying from the survey tower 30. Or, the pile 10 may be surveyed from the survey tower 30 located at the first position P1 and a survey tower other than the survey tower 30 located at the first position P1. In this way, the pile 10 is surveyed from the first position P1 on the sea S and an additional survey position M1 different from the first position P1 (the additional survey position M1 on the crane ship 50 mentioned above or a survey turret other than the survey turret 30).

[0035] In this embodiment, the pile 10 is surveyed from the survey turret 30 located at the first position P1 and from a ship or a survey turret other than the survey turret 30 located at a different position from the survey turret 30. This makes it possible to survey the pile 10 from different directions when viewed from the vertical direction. In this way, by surveying the pile 10 from two different positions, the verticality of the pile 10 can be determined. Furthermore, the pile 10 may be surveyed from two or more different positions in addition to the survey from the survey tower 30. That is, the pile 10 may be surveyed from three or more different positions. For example, in addition to the survey from the survey tower 30, the pile 10 may also be surveyed from a ship located at a position other than the survey tower 30 and from a survey tower other than the survey tower 30. Or, in addition to the survey from the survey tower 30, the pile 10 may also be surveyed from two or more survey towers other than the survey tower 30. In this way, by surveying the pile 10 from three or more different positions, the verticality of the pile 10 can be determined more accurately.

[0036] <Positioning member placement step> The construction of the piles 10 requires that they be driven into the seabed Sa at appropriate positions with high precision. For example, when the pile 10 is driven into the seabed Sa while suspended from a vibro hammer or hydraulic hammer attached to the crane 51, the pile 10 may rotate in the circumferential direction or may sway due to waves. For this reason, it may be difficult to drive the pile 10 into the seabed Sa at an accurate position. Furthermore, when driving a plurality of piles 10 into the seabed Sa, it is required to accurately drive the adjacent piles 10 (for example, piles 10A and 10B in FIG. 1) with a distance therebetween.

[0037] Therefore, it is preferable to place a positioning member 40 for positioning the driving position of the pile 10. The construction method 1 may include a positioning member placing step of placing the positioning member 40. The positioning member placement step is performed before the first pile driving step. The positioning member 40 is placed on the seabed Sa at the exact position where the pile 10 is to be driven. In the positioning member placement step, the positioning member can be placed at the exact position using, for example, a GPS, a total station, or the like. The positioning member 40 is, for example, a template (guide member) placed on the seabed Sa. The positioning member 40 is provided with through holes 41 through which the piles 10 can pass in the vertical direction. The piles 10 are driven into the seabed Sa by having their lower ends pass through the through holes 41 of the positioning member 40 placed on the seabed Sa. In this embodiment, as shown in FIG. 1 , the positioning member 40 is rectangular, and through holes 41 are provided at each corner of a frame body 42 of the positioning member 40. The shape of the positioning member 40 is not limited to a rectangular shape, and may be any geometric shape, such as a triangular shape or another polygonal shape, depending on, for example, the number of piles 10 to be installed.

[0038] In this way, the construction method 1 includes the positioning member arranging step, which allows for accurate positioning of the driving positions of the piles 10. Furthermore, when driving multiple piles 10 into the seabed Sa, the distance between adjacent piles 10 (for example, piles 10A and 10B in FIG. 1) can be accurately determined.

[0039] <Movement step> If the positioning member 40 is placed at the first construction position X1 in the positioning member placement step, the positioning member 40 is moved to the second construction position X2 in the movement step. In detail, after the pile 10 is driven into the first construction position X1 in the first pile driving step, the positioning member 40 is moved to the second construction position X2 together with the survey turret 30-1, which is placed at the second position P2 in the second survey turret placement step. Construction method 1 includes a movement step in which the positioning member 40 is moved to another position on the sea S together with the survey turret 30. In FIG. 1, the positioning member 40-1 (40) moved to the second construction position X2 is shown by a two-dot chain line.

[0040] The positioning member 40 is configured to be removable after driving the pile 10. When the positioning member 40 is a template, the positioning member 40 can be removed from the pile 10 by using, for example, a crane ship 50 to pull the positioning member 40 vertically upward along the pile 10.

[0041] In this way, by including the moving step in construction method 1, the positioning member 40 and the survey tower 30 can be moved at the same time. It is also possible to move the positioning member 40 and the survey tower 30 separately. In this case, the positioning member 40 may be moved before the second survey tower placement step.

[0042] <Stage> The survey tower 30 may be provided with multiple stages 33 (33A, 33B) located at different positions in the vertical direction. In FIG. 2, the first stage 33A is provided at the top end of the survey tower 30, and the second stage 33B is provided in the middle part of the survey tower 30 in the vertical direction. The number of multiple stages 33 is not limited to two. The number of multiple stages 33 may be three or more, taking into consideration the depth of the seabed Sa at the position where the survey tower 30 is to be placed, etc. The vertical positions at which the multiple stages 33 are installed can be determined taking into consideration the water depth and the like at the location where the survey turret 30 is installed. The water depth and the like at which the survey turret 30 is installed are measured in advance, and the stages 33 are installed so as to be located above the sea level Sc, for example.

[0043] For example, in deep water locations, the stage 33 (first stage 33A) installed at the upper end of the survey turret 30 can be used, and in shallow water locations, the stage 33 (second stage 33B) installed in the middle part of the survey turret 30 can be used. In the state shown in Figure 2, the stage 33A is located above the sea surface Sc, and the stage 33B is located underwater Sb. In this state, the stage 33A is used.

[0044] In this manner, in this embodiment, the survey tower 30 is provided with a plurality of stages 33 (33A, 33B) located at different positions in the vertical direction. This allows the plurality of stages 33 (33A, 33B) to be used depending on the water depth at the location where the survey tower 30 is placed, and eliminates the need to prepare a plurality of survey towers 30 of different heights.

[0045] The survey tower 30 may have a gravity foundation. A gravity foundation is a structure in which the base of the survey tower 30 is fixed to the seabed Sa and stability is ensured by its own weight against external forces such as waves and wind. By using a gravity-based survey tower 30 that is anchored to the seabed Sa, the center of gravity of the survey tower 30 can be lowered.

[0046] During construction of the survey tower 30, if the surface of the seabed Sa is soft, subsidence or the like may occur, making it difficult to maintain the stability of the survey tower 30. For this reason, the survey tower 30 has a mud mat 31 placed on the seabed Sa. The mud mat 31 is a wide iron plate. The mud mat 31 is attached to the lower end of the survey tower 30. A concrete block may be attached to the mud mat 31 to lower the center of gravity of the survey tower 30.

[0047] The technical scope of the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure. For example, construction method 1 does not need to include a preparation step of preparing multiple survey towers 30 of different heights. Also, construction method 1 does not need to include a selection step of selecting the survey tower 30 to be used from the multiple survey towers 30 according to the water depth. The marine structure 20 does not have to be a bottom-mounted foundation that supports a wind turbine for offshore power generation. It is not necessary to provide multiple bottom-fixed foundations in the same wind farm or sea area. The multiple piles 10 do not have to be surveyed from the survey tower 30 located at the same position. The stake 10 does not have to be surveyed from a ship located at a position other than the survey tower 30 or from a survey tower other than the survey tower 30. In the construction method 1, it is not necessary to place a positioning member 40 for determining the driving position of the pile 10. The positioning member 40 does not need to be moved to another position on the sea S together with the survey turret 30 . The survey tower 30 may be provided with only one stage 33. The frame member 32 may be configured to be extendable in the vertical direction. By making the frame member 32 extendable in the vertical direction, the position of the stage 33 can be adjusted in the vertical direction depending on the water depth at the location where the survey tower 30 is placed, etc. The survey tower 30 does not have to be a gravity foundation. The survey turret 30 does not necessarily have to have a mud mat 31 placed on the seabed Sa.

[0048] Furthermore, within the scope of the present disclosure, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modified examples may be combined as appropriate.

[0049] (Addendum) The embodiment can be understood, for example, as follows.

[0050] <1> A construction method according to one aspect of the present disclosure includes: A construction method for constructing a marine structure supported by piles, comprising: a first survey tower placement step of placing a survey tower at a first position on the sea; and a second survey turret placement step of moving the survey turret from the first position and placing the survey turret at a second position on the sea.

[0051] When constructing marine structures at multiple locations, the survey turret can be moved to survey the marine structures at each location. Therefore, the construction method can efficiently survey the piles.

[0052] <2> the above <1> The construction method according to the above aspect may employ a configuration in which the piles are moved by a crane ship for driving the piles.

[0053] To move the survey tower, the crane barge used for driving piles can be used, eliminating the need to prepare a separate vessel.

[0054] <3> the above <1> The construction method according to the above aspect may employ a configuration in which the survey tower is moved by a vessel separate from the crane vessel used to drive the piles.

[0055] The other vessel may be, for example, a barge or a self-propelled vessel. By using a vessel separate from the crane vessel used for driving piles to move the survey tower, it is possible to avoid using the crane vessel for a long period of time.

[0056] <4> the above <1> from <3> The construction method according to any one of the items is a preparation step of preparing a plurality of the survey towers having different heights; A configuration may be adopted that includes a selection step of selecting the survey turret to be used from among the plurality of survey turrets according to the water depth.

[0057] The construction method includes a preparation step and a selection step, allowing multiple survey towers to be used depending on the water depth.

[0058] <5> the above <1> from <4> The construction method according to any one of the items is the marine structure is a bottom-fixed foundation supporting a wind turbine for offshore power generation, A configuration may be adopted in which a plurality of the bottom-fixed foundations are provided in the same wind farm or sea area.

[0059] When multiple fixed-bottom foundations are installed in the same wind farm or sea area, the survey tower can be reused.

[0060] <6> the above <5> The construction method related to The bottom-mounted foundation is supported by a plurality of the piles, A configuration may be adopted in which a plurality of the stakes are surveyed from the survey tower located at the same position.

[0061] If a survey tower is placed at a position corresponding to the fixed foundation, it is possible to survey multiple piles from the survey tower at that position.

[0062] <7> the above <1> from <6> The construction method according to any one of the items is A configuration may be adopted in which the stakes are surveyed from a ship located at a position different from the survey tower or from a survey tower different from the survey tower.

[0063] The pile is surveyed from a survey tower located at the first position and from a boat or a survey tower located at a different position from the survey tower. In this way, by surveying the pile from two different positions, the verticality of the pile can be determined.

[0064] <8> the above <1> from <7> The construction method according to any one of the items is A configuration may be adopted that includes a positioning member placement step for placing a positioning member for determining the driving position of the pile.

[0065] By including the positioning member disposing step in the construction method, the pile driving position can be accurately positioned. Furthermore, when driving multiple piles into the seabed, the distance between adjacent piles can be accurately determined.

[0066] <9> the above <8> The construction method related to A configuration may be adopted that includes a moving step for moving the positioning member together with the survey turret to another position on the sea.

[0067] By including a moving step in the construction method, the positioning member and the survey tower can be moved at the same time.

[0068] <10> the above <1> from <9> The construction method according to any one of the items is The survey tower may have a configuration including a plurality of stages positioned at different positions in the vertical direction.

[0069] A plurality of stages can be used depending on the water depth at the location where the survey tower is placed, eliminating the need to prepare a plurality of survey towers of different heights.

[0070] <11> the above <1> from <10> The construction method according to any one of the items is The survey tower may be configured as a gravity foundation.

[0071] By using a gravity-based survey tower that rests on the seabed, the survey tower's center of gravity can be lowered.

[0072] <12> the above <1> from <11> The construction method according to any one of the items is The survey turret may have a mud mat placed on the seabed.

[0073] By providing the survey tower with a mud mat, the survey tower's center of gravity can be further lowered. [Explanation of symbols]

[0074] 1 Construction method 10, 10-1 pile 20,20-1 Marine structures 30,30-1 Survey Tower 31 Bottom plate (Mad Mat) 33 Stages 40,40-1 Positioning member 50 Hoist Ship M1 Additional survey position P1 1st position P2 2nd position X1 1st construction position X2 2nd construction position

Claims

1. A construction method for constructing a marine structure supported by piles, comprising: a first survey turret placement step of placing a survey turret at a first position on the sea; a second survey turret placement step of moving the survey turret from the first position and placing the survey turret at a second position on the sea; A construction method comprising: a positioning member placement step of placing a positioning member to position the driving position of the pile.

2. 2. The construction method according to claim 1, wherein the survey tower is moved by a crane ship for driving the piles.

3. 2. The construction method according to claim 1, wherein the survey tower is moved by a vessel separate from a crane vessel for driving the piles.

4. a preparation step of preparing a plurality of the survey towers having different heights; 2. The construction method according to claim 1, further comprising a selection step of selecting the survey tower to be used from among the plurality of survey towers according to the water depth.

5. the marine structure is a bottom-fixed foundation supporting a wind turbine for offshore power generation, The construction method according to claim 1 , wherein a plurality of the bottom-fixed foundations are provided in the same wind farm or sea area.

6. The bottom-mounted foundation is supported by a plurality of the piles, The construction method according to claim 5, wherein the plurality of piles are surveyed from the survey tower located at the same position.

7. 5. The construction method according to claim 1, wherein the piles are also surveyed from a ship located at a position different from the survey tower or from a survey tower different from the survey tower.

8. The construction method according to any one of claims 1 to 4, further comprising a moving step of moving the positioning member together with the survey turret to another position on the sea.

9. 5. The construction method according to claim 1, wherein the survey tower has a plurality of stages positioned at different positions in the vertical direction.

10. 5. The construction method according to claim 1, wherein the survey tower is a gravity foundation.

11. The construction method according to claim 10, wherein the survey turret has a mud mat placed on the seabed.

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