Single-machine double-hook combined hoisting construction method for offshore wind turbine single-pile foundation

Abstract

The invention discloses a single-machine double-hook combined hoisting construction method for a single-pile foundation of an offshore wind turbine, which belongs to the technical field of offshore wind power engineering and comprises the following steps of: (1) positioning a crane ship and entering a steel pipe pile transport ship; (2) pile turning stress calculation; (3) preparing a sling; (4) hanging the steel pipe piles; and (5) hoisting and turning over the steel pipe pile. The offshore wind turbine foundation double-hook combined lifting process can be achieved only through a single crane and a sling, one main hook is used for being connected with a lifting beam and a single-pile main lifting lug, the other main hook is used for being connected with a single-pile tail sliding steel wire rope, and through double-hook combined retracting and releasing, moving and turning over of a steel pipe pile are achieved; according to the technology, a triangular stress system during overturning is built, the overturning process is safer and more stable, the number of input construction machines is small, the work efficiency is high, the economic benefit is high, and the problems that the input equipment amount is large, cross operation is much, and the construction period is difficult to control in an existing double-machine hoisting technology are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of offshore wind power engineering, and particularly to a method for hoisting and constructing a single-pile foundation of an offshore wind turbine. Background Art

[0002] The single-pile foundation of an offshore wind turbine uses a steel pipe pile as the main structure, which has large external dimensions and heavy weight, and has high requirements for transportation conditions. To solve this problem, the manufacturer uses a large transport ship for transportation, arranges a U-shaped transport tooling longitudinally along the transport ship, and places the steel pipe pile horizontally on the tooling. After the steel pipe pile is transported to the wind farm, it finally needs to be driven into the pile in an upright state, which involves the turning over and hoisting of the steel pipe pile. The conventional method for turning over and hoisting the steel pipe pile is to set a main lifting point and an auxiliary lifting point on the steel pipe pile, and use the method of double-crane lifting and delivery, which has the defects of large amount of equipment input, many cross operations, and difficult construction period control. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for single-crane double-hook combined hoisting construction of a single-pile foundation of an offshore wind turbine with less construction machinery input, high work efficiency and high economic benefits.

[0004] To solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A method for single-crane double-hook combined hoisting construction of a single-pile foundation of an offshore wind turbine, comprising the following steps:

[0006] ① Positioning the crane ship and the approach of the steel pipe pile transport ship;

[0007] ② Calculating the force for pile turning;

[0008] ③ Preparing the slings: Before hoisting, it is necessary to calculate the weight of the steel pipe pile, the forces on the main lifting point and the tailing lifting point, the distance between the main lifting ear of the steel pipe pile and the pile top, and the required lifting height, and select the main lifting beam sling assembly and the tailing sling. The main lifting beam sling assembly includes a transverse lifting beam, an upper connecting left wire loop, an upper connecting right wire loop, a lower connecting left wire loop, and a lower connecting right wire loop. Upper shackles are provided on the upper surfaces at both ends of the transverse lifting beam, and lower shackles are provided on the lower surfaces at both ends of the transverse lifting beam; a first main hook and a second main hook are arranged at the upper end of the crane boom. The first main hook is used to hang the main lifting beam sling assembly, and the second main hook is used to hang the tailing sling;

[0009] ④ Hanging connection of steel pipe piles: Main lifting lugs are arranged on both sides of the front of the steel pipe pile, and a tailing lifting lug is arranged on the upper surface of the rear of the steel pipe pile; the lower ends of the lower connecting left wire loops and the lower ends of the lower connecting right wire loops in the main lifting beam rigging assembly are respectively connected to the main lifting lugs on both sides of the front end of the steel pipe pile, the upper ends of the lower connecting left wire loops and the upper ends of the lower connecting right wire loops are respectively connected to the lower shackles at both ends of the transverse lifting beam, the upper ends of the upper connecting left wire loops and the upper ends of the upper connecting right wire loops in the main lifting beam rigging assembly are respectively connected to the left hook head and the right hook head on the first main hook, and the lower ends of the upper connecting left wire loops and the lower ends of the upper connecting right wire loops are respectively connected to the upper shackles at both ends of the transverse lifting beam; the tailing steel wire rope passes through the shackle, both ends of the tailing steel wire rope are connected to the second main hook, and the shackle is hung into the tailing lifting lug on the upper surface of the rear of the steel pipe pile;

[0010] ⑤ Lifting and turning over of steel pipe piles: The first main hook and the second main hook of the crane lift, horizontally lift the steel pipe pile. After lifting to a certain height, the transport ship withdraws; the crane enters the turning-over working condition, slowly increases the lifting weight of the first main hook, and at the same time slowly reduces the lifting weight of the second main hook, so that the main lifting lug of the steel pipe pile slowly rises and the tailing lifting lug slowly descends until the steel pipe pile turns over and stands upright. After the steel pipe pile turns over and stands upright, select a suitable position to pull out the pin of the shackle at the tailing lifting lug.

[0011] Further, in the step ①, the positioning method of the crane barge is as follows: The crane barge enters the site against the current, and two groups of cross anchors are thrown at the bow and stern respectively. Calculate the anchor point coordinates of the crane barge in advance, and use the anchor boat to throw the anchors to the designated positions. According to the DGPS software carried by the crane barge, position it by winching the anchors; the approach method of the steel pipe pile transport ship is as follows: After the transport ship enters the site against the current, it berths against the crane barge, stops at the position where the center of gravity of the steel pipe pile is aligned with the center of the crane, uses the cable to tie up with the crane barge, and the main ship releases the anchor rope interfering with the transport ship.

[0012] Further, in the step ②, the specific method of the force calculation for turning over the pile is as follows:

[0013] Step 1. According to the principle of the intersection of three forces, establish a calculation model through geometric calculation;

[0014] Step 2. Set parameters for the steel pipe pile:

[0015] Take 97m from the top of the crane to the center of the steel pipe pile. Among them, F1 is the force on the No. 1 main hook, unit: kN; F2 is the force on the No. 2 main hook, unit: kN; G is the weight of the steel pipe pile, unit: kN; O1 is the fulcrum 1; O2 is the fulcrum 2; L1 is the lever arm of F1 with O1 as the fulcrum, unit: m; L2 is the lever arm of F2 with O1 as the fulcrum, unit: m; L3 is the lever arm of G with O1 as the fulcrum, unit: m; L4 is the lever arm of F1 with O2 as the fulcrum, unit: m; L5 is the lever arm of G with O2 as the fulcrum, unit: m; ∠1 is the outward swing angle of the No. 1 main hook; ∠2 is the outward swing angle of the No. 2 main hook;

[0016] Step 3. Obtain L1, L2, L3, L4, and L5 according to the turning angle of the steel pipe pile and the actual size of the steel pipe pile;

[0017] Step 4. Establish a moment conservation equation:

[0018] Establish a moment conservation equation with O1 as the fulcrum: F1*L1 + F2*L2 = G*L3; establish a moment conservation equation with O2 as the fulcrum: F1*L4 = G*L5;

[0019] Step 5. Calculate the forces on the No. 1 main hook and the No. 2 main hook during the turning process:

[0020] Assume the weight of the main sling is G1, then the estimated weight Fmain of the No. 1 main hook: Fmain = F1 + G1 / cos∠1; assume the weight of the tailing sling is G2, then the estimated weight Faux of the No. 2 main hook: Faux = F2 + G2 / cos∠2; sequentially calculate the forces on the No. 1 main hook and the No. 2 main hook when the steel pipe pile is in the horizontal state, turned by 15°, 30°, 45°, 60°, 75°, and 85°.

[0021] Further, in the step ④, the operation sequence of hanging the steel pipe pile is as follows: (1) Personnel board near the tailing lifting lug at the tail of the steel pipe pile; (2) Swing the crane boom so that the tailing steel wire rope is directly opposite the tailing lifting lug; (3) Lower the second main hook, and the staff inserts the pin at the shackle into the tailing lifting lug and locks it. After the installation is completed, the personnel withdraw to the main ship; (4) Swing the crane boom so that the lifting beam is directly opposite the main lifting lug of the steel pipe pile, lower the first main hook, and respectively put the left wire loop and the right wire loop connected below the lifting beam onto the main lifting lug of the steel pipe pile; (5) Swing the crane boom so that the crane boom is above the center of gravity of the steel pipe pile.

[0022] The beneficial effects of the present invention are as follows:

[0023] The double-hook combined lifting process for the offshore wind turbine foundation of the present invention can be realized only by a single crane and slings. Use one of the main hooks to connect the lifting beam and connect it to the main lifting lug of the single pile, and use the other main hook to connect the tailing steel wire rope of the single pile. Through the combined retraction and release of the double hooks, the movement and turning of the steel pipe pile are realized. This process constructs a triangular force system during turning, and the turning process is safer and more stable. Moreover, the construction machinery invested is less, the work efficiency is high, and the economic benefit is high, solving the problems existing in the existing double-crane lifting process, such as large investment in equipment, many cross operations, and difficult control of the construction period. Description of the Drawings

[0024] The present invention is further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation to the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the following drawings:

[0025] Figure 1 Process flow chart of the construction method of the present invention

[0026] Figure 2 Calculation model established by the present invention through geometric calculation

[0027] Figure 3 For the present invention Figure 2 Force analysis diagram shown

[0028] Figure 4 Front view of the spreader installation of the present invention

[0029] Figure 5 For Figure 4 Side view of the installation of the main lifting beam and rigging assembly shown

[0030] In the figure: 1. First main hook; 2. Second main hook; 3. Main lifting beam and rigging assembly; 4. Steel pipe pile; 5. Main lifting ear; 6. Tail-lifting ear; 7. Tail-lifting steel wire rope; 8. Shackle; 9. Transverse lifting beam; 10. Upper connecting left wire loop; 11. Upper connecting right wire loop; 12. Lower connecting left wire loop; 13. Lower connecting right wire loop; 14. Upper shackle; 15. Lower shackle. Detailed implementation manners

[0031] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments may be combined with each other.

[0032] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper surface", "lower surface", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "forward rotation", "reverse rotation", "axial direction", "radial direction", "circumferential direction", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0033] As Figure 1 shown, a method for the combined lifting of a single-pile foundation of an offshore wind turbine by a single machine with double hooks includes the following steps:

[0034] A method for the combined lifting of a single-pile foundation of an offshore wind turbine by a single machine with double hooks includes the following steps:

[0035] ① Positioning of the crane ship and arrival of the steel pipe pile transport ship

[0036] The positioning method of the crane ship is as follows: The crane ship approaches against the current. Two groups of spread anchors are cast at the bow and stern respectively. Calculate the anchor point coordinates of the crane ship in advance, and use the anchor boat to cast the anchors to the designated positions. According to the DGPS software carried by the crane ship, position it by winching the anchors; The approach method of the steel pipe pile transport ship is as follows: After the transport ship approaches against the current, it berths alongside the crane ship and stops at the position where the center of gravity of the steel pipe pile aligns with the center of the crane. Use the cable to tie up with the crane ship, and the main ship releases the anchor rope that interferes with the transport ship.

[0037] ② Calculation of the force during pile turning

[0038] The specific method for calculating the force during pile turning is as follows:

[0039] Step 1. According to the principle of the intersection of three forces, establish a calculation model through geometric calculation. Figure 2 Among them, F1 is the force on the No. 1 main hook, unit: kN; F2 is the force on the No. 2 main hook, unit: kN; G is the weight of the steel pipe pile, unit: kN; O1 is the fulcrum 1; O2 is the fulcrum 2; P is the line of action of gravity; V is the starting point of the No. 2 main hook; C is the starting point of the No. 1 main hook.

[0040] Step 2. Set parameters for the steel pipe pile:

[0041] The floating crane ship "Zhongtian 9" adopts a lifting height of 97m, which is determined according to the actual lifting height for different working surfaces. The distance from the top of the crane to the center of the steel pipe pile is taken as 97m; L1 is the lever arm of F1 with O1 as the fulcrum, unit: m; L2 is the lever arm of F2 with O1 as the fulcrum, unit: m; L3 is the lever arm of G with O1 as the fulcrum, unit: m; L4 is the lever arm of F1 with O2 as the fulcrum, unit: m; L5 is the lever arm of G with O2 as the fulcrum, unit: m; ∠1 is the outward swing angle of the No. 1 main hook; ∠2 is the outward swing angle of the No. 2 main hook, as Figure 3 shown.

[0042] Step 3. According to the turning angle of the steel pipe pile and the actual dimensions of the steel pipe pile, obtain L1, L2, L3, L4, and L5.

[0043] Step 4. Establish an equation of moment conservation:

[0044] Establish an equation of moment conservation with O1 as the fulcrum: F1*L1 + F2*L2 = G*L3;

[0045] Establish an equation of moment conservation with O2 as the fulcrum: F1*L4 = G*L5.

[0046] Step 5. Calculate the forces on the No. 1 main hook and the No. 2 main hook during the turning process:

[0047] Let the weight of the main sling be G1, then the estimated lifting weight F_main of the No. 1 main hook: F_main = F1 + G1 / cos∠1; Let the weight of the tailing sling be G2, then the estimated lifting weight F_aux of the No. 2 main hook: F_aux = F2 + G2 / cos∠2; Calculate the forces on the No. 1 main hook and the No. 2 main hook of the steel pipe pile in the horizontal state, when it is flipped by 15°, 30°, 45°, 60°, 75°, and 85° in sequence.

[0048] ③ Sling preparation

[0049] Before hoisting, it is necessary to calculate the weight of the steel pipe pile 4, the forces on the main lifting point and the tailing lifting point, the distance between the main lifting ear of the steel pipe pile and the pile top, and the required lifting height. Select the main lifting beam sling assembly 3 and the tailing sling. Set the first main hook 1 and the second main hook 2 at the upper end of the crane boom. The first main hook 1 is used to hang the main lifting beam sling assembly 3, and the second main hook 2 is used to hang the tailing sling. Set the main lifting ears 5 on both sides of the front part of the steel pipe pile 4, and set the tailing lifting ear 6 on the upper surface of the rear part of the steel pipe pile 4. The tailing sling includes a tailing steel wire rope 7 and a shackle 8. The tailing steel wire rope 7 passes through the shackle 8, and both ends of the tailing steel wire rope 7 are connected to the second main hook 2. The shackle 8 is hung into the tailing lifting ear 6 on the upper surface of the rear part of the steel pipe pile 4, as Figure 4 shown.

[0050] ④ Hanging connection of the steel pipe pile

[0051] The main lifting beam sling assembly includes a transverse lifting beam 9, an upper connecting left wire loop 10, an upper connecting right wire loop 11, a lower connecting left wire loop 12, and a lower connecting right wire loop 13. Upper shackles 14 are provided on the upper surfaces at both ends of the transverse lifting beam 5, and lower shackles 15 are provided on the lower surfaces at both ends of the transverse lifting beam 5; Connect the lower ends of the lower connecting left wire loop 12 and the lower connecting right wire loop 13 in the main lifting beam sling assembly to the main lifting ears 5 on both sides of the front end of the steel pipe pile 4 respectively, and connect the upper ends of the lower connecting left wire loop 12 and the lower connecting right wire loop 13 to the lower shackles 15 at both ends of the transverse lifting beam 9 respectively. Connect the upper ends of the upper connecting left wire loop 10 and the upper connecting right wire loop 11 in the main lifting beam sling assembly to the left hook head and the right hook head on the first main hook 1 respectively, and connect the lower ends of the upper connecting left wire loop 10 and the upper connecting right wire loop 11 to the upper shackles 14 at both ends of the transverse lifting beam 9 respectively, as Figure 5 shown.

[0052] The operation sequence of the steel pipe pile hanging is as follows: (1) a person climbs onto the tail end of the steel pipe pile near the lug; (2) the arm is rotated so that the tail end wire rope is facing the lug; (3) the second main hook is lowered, and the staff inserts the pin at the shackle into the lug and locks it. After the installation is completed, the staff withdraws to the main ship; (4) the arm is rotated so that the lifting beam faces the main lug of the steel pipe pile, the first main hook is lowered, and the lower left wire ring and the lower right wire ring connected under the lifting beam are respectively inserted into the main lug of the steel pipe pile; (5) the arm is rotated so that the arm is located above the center of gravity of the steel pipe pile.

[0053] ⑤ Lifting and turning of steel pipe piles

[0054] The first and second main hooks of the crane are raised to lift the steel pipe pile horizontally. After lifting it to a certain height, the transport ship withdraws. The crane enters the turning condition, slowly increases the lifting weight of the first main hook, and slowly reduces the lifting weight of the second main hook, so that the main lifting lug of the steel pipe pile slowly rises and the tail lifting lug slowly decreases until the steel pipe pile turns over and stands upright. After the steel pipe pile turns over and stands upright, select a suitable position to pull out the pin of the shackle at the tail lifting lug.

[0055] Scope of application: The present invention is suitable for lifting operations in unsheltered sea areas with a water depth of 0-50m, and is particularly suitable for lifting and turning over large steel pipe piles.

[0056] The construction principle of the present invention: The steel pipe piles used as the foundation of offshore wind turbines weigh thousands of tons and are nearly 100 meters long. The pile turning operation needs to be achieved through at least two forces, including the main force on the upper part of the pile body and the auxiliary force on the lower part of the pile body. The main force is achieved by hanging the main lifting lug with a sling. The auxiliary force is achieved by hanging the tail lifting lug with a sling or directly clamping the pile tail with a tail clamp.

[0057] The present invention adopts a method of lifting and turning piles with double hooks of a single crane. The double main hooks are both mountain-shaped hooks, which are arranged symmetrically on the top of the crane, and can swing outward in a direction perpendicular to the boom. The double main hooks each hang on the main lifting lug and the tail lifting lug of the steel pipe pile. When the force on the steel pipe pile is stable, the main lifting point and the force direction of the tail and the line of action of the center of gravity converge at one point, forming a stable triangular force system. The turning of the steel pipe pile is achieved through the joint cooperation of the double main hooks.

[0058] The following points should be noted during the turning process of the present invention: (1) at least one lifting commander and one deputy lifting commander should be provided; (2) the lifting force of the hook should be controlled with reference to the calculation data of the turning of the steel pipe pile; (3) the outward swing angle of the main hook should not exceed the maximum value designed by the crane; (4) the steel pipe pile should not touch the seabed.

[0059] Benefit analysis after applying the present invention: Taking the Rudong Offshore Wind Farm Project as an example, the application of this construction method improves the construction efficiency and safety factor, and saves the construction cost. For the single foundation pile driving operation, the construction period using this construction method is 2 days, and the construction resources occupied are 1 main ship and 2 anchor boats; the construction period using the conventional process is 3 days, and the construction resources occupied are 1 main ship, 1 auxiliary crane ship, and 4 anchor boats. Taking the construction of a 4MW offshore wind turbine foundation as an example: the main construction ship is calculated at 300,000 yuan per day, the anchor boat is calculated at 20,000 yuan per day, and the labor (offshore personnel) is calculated at 700 yuan per day.

[0060]

[0061] As can be seen from the above table: Using this construction method for a single machine position saves 1,524,000 - 722,000 = 802,000 yuan in construction cost compared with other construction methods.

[0062] In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for single-machine double-hook joint lifting construction of an offshore wind turbine single pile foundation, characterized in that: The following steps are involved: ① Positioning of crane ship and entry of steel pipe pile transport ship; ② Calculation of pile force; ③ Preparation of rigging: Before lifting, it is necessary to calculate the weight of the steel pipe pile, the forces on the main lifting point and the tail lifting point, the distance between the main lifting ear of the steel pipe pile and the pile top, and the required lifting height, and select the main lifting beam rigging assembly and the tail rigging. The main lifting beam rigging assembly includes a transverse lifting beam, an upper left wire ring, an upper right wire ring, a lower left wire ring, and a lower right wire ring. The upper surfaces of both ends of the transverse lifting beam are provided with upper shackles, and the lower surfaces of both ends of the transverse lifting beam are provided with lower shackles; the first main hook and the second main hook are arranged at the upper end of the crane boom, the first main hook is used to hang the main lifting beam rigging assembly, and the second main hook is used to hang the tail rigging; ④ Steel pipe pile hanging: main lifting ears are set on both sides of the front part of the steel pipe pile, and tail lifting ears are set on the upper surface of the rear part of the steel pipe pile; the lower ends of the lower left wire ring and the lower ends of the lower right wire ring in the main lifting beam rigging assembly are respectively connected to the main lifting ears on both sides of the front end of the steel pipe pile, and the upper ends of the lower left wire ring and the upper ends of the lower right wire ring are respectively connected to the lower shackles at both ends of the transverse lifting beam, and the upper ends of the upper left wire ring and the upper ends of the upper right wire ring in the main lifting beam rigging assembly are respectively connected to the left hook head and the right hook head on the first main hook, and the lower ends of the upper left wire ring and the lower ends of the upper right wire ring are respectively connected to the upper shackles at both ends of the transverse lifting beam; the tail wire rope passes through the shackle, and the two ends of the tail wire rope are connected to the second main hook, and the shackle is hung in the tail lifting ears on the upper surface of the rear part of the steel pipe pile; ⑤ Lifting and turning over of steel pipe piles: the first main hook and the second main hook of the crane are lifted, and the steel pipe pile is lifted horizontally. After it is lifted to a certain height, the transport ship withdraws; the crane enters the turning condition, slowly increases the lifting weight of the first main hook, and slowly reduces the lifting weight of the second main hook, so that the main lifting lug of the steel pipe pile is slowly lifted, and the tail lifting lug is slowly lowered until the steel pipe pile is turned over and erected. After the steel pipe pile is turned over and erected, select a suitable position to pull out the pin of the shackle at the tail lifting lug.

2. The method for single-machine double-hook joint lifting construction of a single pile foundation of an offshore wind turbine according to claim 1 is characterized in that: In step ①, the positioning method of the crane ship is as follows: the crane ship approaches the site upstream, and two sets of figure-eight anchors are dropped at the bow and stern respectively. The anchor point coordinates of the crane ship are calculated in advance, and the anchors are dropped to the designated positions by the anchor boat. According to the DGPS software of the crane ship, the anchors are positioned by winding the anchors; the approach method of the steel pipe pile transport ship is as follows: after the transport ship approaches the site upstream, it berths at the crane ship and stops at the position where the center of gravity of the steel pipe pile is aligned with the center of the crane. It is moored with the crane ship using cables, and the main ship loosens the anchor ropes that interfere with the transport ship.

3. The method for single-machine double-hook joint lifting construction of a single pile foundation of an offshore wind turbine according to claim 2 is characterized in that: In step ②, the specific method for calculating the pile turning force is as follows: Step 1. According to the principle of three-force intersection, establish a calculation model through geometric calculation; Step 2. Set the parameters of the steel pipe pile: the distance from the top of the crane to the center of the steel pipe pile is 97m, where F1 is the force on the No. 1 main hook, unit: kN; F2 is the force on the No. 2 main hook, unit: kN; G is the weight of the steel pipe pile, unit: kN; O1 is the fulcrum 1; O2 is the fulcrum 2; L1 is the lever arm with O1 as the fulcrum F1, unit: m; L2 is the lever arm with O1 as the fulcrum F2, unit: m; L3 is the lever arm with O1 as the fulcrum G, unit: m; L4 is the lever arm with O2 as the fulcrum F1, unit: m; L5 is the lever arm with O2 as the fulcrum G, unit: m; ∠1 is the outward swing angle of the No. 1 main hook; ∠2 is the outward swing angle of the No. 2 main hook; Step 3. According to the steel pipe pile flip angle and the actual size of the steel pipe pile, obtain L1, L2, L3, L4, and L5; Step 4. Establish the torque conservation equation: Take O1 as the fulcrum to establish the torque conservation equation: F1*L1+F2*L2=G*L3; take O2 as the fulcrum to establish the torque conservation equation: F1*L4=G*L5; Step 5. Calculate the forces on the No. 1 and No. 2 main hooks during the flipping process: Assuming the weight of the main lifting rigging is G1, the lifting weight Fmain of main hook No. 1 is estimated as: Fmain=F1+G1 / cos∠1; Assuming the weight of the tail lifting rigging is G2, the lifting weight Faux of main hook No. 2 is estimated as: Faux=F2+G2 / cos∠2; calculate the forces on main hook No. 1 and main hook No. 2 when the steel pipe pile is in horizontal state, flipped by 15°, 30°, 45°, 60°, 75° and 85° respectively.

4. The method for single-machine double-hook joint lifting construction of a single pile foundation of an offshore wind turbine according to claim 1 is characterized in that: In step ④, the operation sequence of the steel pipe pile hanging is as follows: (1) a person climbs onto the tail end of the steel pipe pile near the lug; (2) the arm is rotated so that the tail end wire rope is facing the lug; (3) the second main hook is lowered, and the staff inserts the pin at the shackle into the lug and locks it. After the installation is completed, the staff withdraws to the main ship; (4) the arm is rotated so that the hanging beam faces the main lug of the steel pipe pile, the first main hook is lowered, and the lower connecting left wire ring and the lower connecting right wire ring connected under the hanging beam are respectively inserted into the main lug of the steel pipe pile; (5) the arm is rotated so that the arm is located above the center of gravity of the steel pipe pile.

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