WO2024007618A1

WO2024007618A1 - Apparatus and method for reinforcing and rectifying offshore wind turbine monopile foundation

Info

Publication number: WO2024007618A1
Application number: PCT/CN2023/081776
Authority: WO
Inventors: 李小娟; 竺明星; 王丽艳; 吴思麟; 陈哲衡; 席爽; 刘静; 凌晨; 刘宏远
Original assignee: 江苏科技大学
Priority date: 2022-07-04
Filing date: 2023-03-16
Publication date: 2024-01-11
Also published as: CN115110591B; CN115110591A

Abstract

An apparatus and method for reinforcing and rectifying an offshore wind turbine monopile foundation. The apparatus comprises a steel casing (11) fixedly sleeved on the wind turbine monopile foundation, and a plurality of steel frame structures (12) are uniformly fixed on the steel casing (11) in the circumferential direction; a composite foundation (4) is provided around the wind turbine monopile foundation, and the composite foundation (4) is formed by injecting cement into a soil body and performing stirring and reinforcement; a plurality of precast piles (3) used as ground anchors are provided in the composite foundation (4), and the plurality of precast piles (3) are annularly and uniformly arranged by using the wind turbine monopile foundation as a center; the steel frame structures (12) are connected to the precast piles (3) by means of anchor cables (2). During operation, the specific anchor cables (2) are tensioned in a graded manner to apply an external pulling force to the wind turbine monopile foundation, thereby realizing deviation rectification. The apparatus can solve the problems that a local scouring pit is enlarged and the mechanical property of a soil body is weakened, and can also realize comprehensive improvement of the vertical, horizontal and torsional bearing capacity of an original wind turbine monopile foundation.

Description

A device and method for reinforcing and correcting deviations of offshore wind power single pile foundations

Technical field

The invention relates to pile foundation reinforcement, and in particular to a device and method for strengthening and correcting deviations of offshore wind power single pile foundations.

Background technique

The offshore wind power monopile foundation needs to withstand multiple lateral cyclic loads such as wind, waves, and ocean currents during the service life of the wind turbine. Tens of millions of cycles of these multi-directional coupled cyclic loads are enough to cause cumulative displacement of the foundation and weakening of the surrounding soil, thus Affects the load-bearing performance of the wind turbine foundation. On the other hand, local scour of the seabed caused by ocean currents widely exists in my country's offshore wind farm areas, and the maximum scour depth has far exceeded the design scour depth, seriously threatening the safety of wind turbines. The accumulated displacement and scour pits during normal service of offshore wind turbines are the main factors that reduce the bearing capacity of the foundation and threaten the overall stability of the structure.

Contents of the invention

Purpose of the invention: The purpose of the invention is to propose a method for reinforcing and correcting deviations of offshore wind power single pile foundations in order to solve the problem of reduced foundation bearing capacity and weakened overall structural stability caused by cumulative displacement and local erosion during normal service of offshore wind turbines. device, the second object of the present invention is to provide a method for strengthening and correcting deviations of offshore wind power monopile foundations.

Technical solution: On the one hand, the present invention provides a device for reinforcing and correcting deviations of offshore wind power monopile foundations, which includes a steel casing that is sleeved and fixed on the wind power monopile foundation. A number of steel casings are evenly fixed on the steel casing along the circumferential direction. A frame structure; a composite foundation is provided around the wind power single pile foundation. The composite foundation is formed by injecting cement into the soil and mixing and strengthening it; the composite foundation is provided with several prefabricated piles used as ground anchors, and multiple prefabricated piles are The wind power single pile foundation is the center and is evenly arranged in a ring; the steel frame structure and the prefabricated piles are connected through anchor cables.

Among them, the steel frame structure includes connected steel trusses and steel plates. Guide holes are reserved on the steel plates to guide the anchor cable tension to the center of the wind power monopile foundation; the anchor cables pass through the guide holes and are fixed to the steel trusses through anchors. superior. In order to ensure that the tension direction of the anchor cable points to the center of the wind power monopile foundation, the plane provided by the steel plate and steel truss should be consistent with the tangent direction of the steel casing.

There is a connecting ring on the top of the prefabricated pile. The anchor cable passes through the connecting ring and is folded in half and tightened by a fixed buckle. The prefabricated piles are provided with grooves to prevent the anchor cables from slipping. Welding can be used between the connecting ring and the prefabricated pile, and the strength and stiffness of the welding joint should meet the tensile requirements. The precast piles arranged in an annular manner are one or more layers, depending on actual needs. The radial and circumferential intervals of the precast piles should meet the requirements of ignoring pile group effects stipulated in relevant specifications. The steel casing and the wind power monopile foundation are fixedly connected with high-strength bolts to ensure that the strength and stiffness of the steel casing and its connection meet local tensile requirements. The anchor cable uses steel ropes, steel wire bundles or CFRP bars, which are made of materials with high strength, high elastic modulus and high load-bearing performance. Prefabricated piles use steel pipe piles, PC or PHC pipe piles. The pile diameter, wall thickness and driving depth need to resist the pull-out force and horizontal force generated by the anchor cable tension, and avoid damage to the structure itself.

On the other hand, the present invention also provides a method for strengthening and correcting deviations of offshore wind power single pile foundations, which includes the following steps:

(1) Use a mixture of sand and gravel to fill the scour pit;

(2) Within the designed reinforcement range of the wind power single pile foundation, use a mixing pile machine to spray cement into the soil and stir it thoroughly. The cement and soil will harden to form a composite foundation to improve the strength of the soil around the wind power single pile foundation; in the cement not sufficiently hardened to the soil In practice, several prefabricated piles are driven into the designed location;

(3) Install steel casings on the wind power single pile foundation and use high-strength bolts to connect them;

(4) Install anchor cables to connect the prefabricated piles and the steel frame structure on the surface of the steel casing;

(5) Tension specific anchor cables to exert external pulling force on the wind turbine single pile foundation to achieve deviation correction;

During the deviation correction process, the tensioning sequence of the anchor cables is: the two anchor cables in the direction perpendicular to the horizontal displacement w are tensioned first, and then the anchor cables adjacent to the two anchor cables and capable of providing the opposite pulling force in the w direction are sequentially Symmetrical tensioning, the anchor cable that is consistent with the w direction and passes through the center of the wind turbine single pile foundation is the last tension, ensuring that the direction of the resultant tensile force provided by the specific anchor cable points to the center of the wind turbine single pile foundation and is opposite to the horizontal displacement w direction of the wind turbine single pile foundation. ;

(6) After the correction is completed, tension and fix the remaining anchor cables in sequence so that all anchor cables maintain a certain tension and the resultant force is zero.

Among them, in step (2), the reinforcement depth of the composite foundation needs to be greater than twice the diameter of the wind power single pile foundation, and the reinforcement radius needs to be greater than the mechanical transmission influence range around the wind power single pile foundation, which can be determined based on numerical simulation.

In step (5), the pulling force exerted by each anchor cable (2) is the same, and the pulling force is calculated using the following formula:

Q is the tensile force exerted by each anchor cable; E is the elastic modulus of the anchor cable; A is the cross-sectional area of the anchor cable; w is the horizontal displacement of the connection position between the wind turbine single pile foundation and the steel casing; i is the direction with w Starting from the vertical direction to the i-th anchor cable within the range of 90°, i=0,1,2...n; θ=90°/n; j is the number of layers of prefabricated piles from outside to inside, j=1,2 , 3,...,m; l _j is the length of the j-th layer anchor cable; α _j is the angle between the anchor cable corresponding to the j-th layer prefabricated pile and the sea level.

In the present invention, after the correction is completed, the vertical, horizontal and torsional bearing capacity of the original wind power single pile foundation can be comprehensively improved.

Beneficial effects: Compared with the existing technology, the present invention has the following significant advantages: the present invention solves the problems of local scour pit expansion and soil mechanical properties weakening by reinforcing the soil around the wind power single pile foundation; by arranging the reinforcement area in an annular shape The prefabricated piles are connected to the main body of the foundation through anchor cables to achieve the purpose of correcting the deviation of the wind power single pile foundation and improving its load-bearing performance; the device of the present invention has a simple structure, and the deviation correction and reinforcement scheme is efficient and feasible.

Description of the drawings

Figure 1 is a schematic diagram of a wind power monopile foundation;

Figure 2 is a schematic structural diagram of the present invention;

Figure 3 is a schematic diagram of the steel frame structure layout;

Figure 4 is a side view of the steel frame structure;

Figure 5 is a front view of the steel frame structure;

Figure 6 is a top view of prefabricated piles and composite foundation;

Figure 7 is a schematic diagram of the connection structure between the anchor cable and the prefabricated pile;

Figure 8 is a schematic diagram of the tensioning sequence during correction;

Figure 9 is a schematic diagram of the tensioning sequence after correction;

Reference signs: 1-wind power monopile foundation, 11-steel casing, 111-high-strength bolts, 12-steel frame structure, 121-guide hole, 122-steel plate, 123-steel truss, 2-anchor cable, 21-anchor Connector, 22-fixed buckle, 3-prefabricated pile, 31-connecting ring, 4-composite foundation.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, the target wind power single pile foundation 1 to be reinforced and corrected has a diameter of 6.5m and a burial depth of 40m. The site is covered with a thick soft clay layer, and a quasi-conical local scour pit is formed around the pile. The maximum scour depth is 10m. The diameter is 15m. By measuring the corresponding rotation angle of the pile top, it is determined that the horizontal displacement of the connection between the single pile and the tower is w=50mm.

As shown in Figures 2 to 5, a device for strengthening and correcting offshore wind power monopile foundations is provided with a steel casing 11 at the connection point between the wind power monopile foundation 1 and the tower. The steel casing 11 is connected to the wind power monopile foundation 1. Use high-strength bolts 111 to connect. A number of steel frame structures 12 are uniformly distributed on the surface of the steel sheath 11 and welded and fixed. The steel frame structure 12 includes a steel plate 122 with reserved guide holes 121, and a steel truss 123. The steel truss 123 is used to support and fix the anchor cable 2. A connecting ring 31 is welded on the top of the prefabricated pile 3, and a groove is provided on the connecting ring 31 to prevent the anchor cable 2 from sliding. After one end of the anchor cable 2 passes through the guide hole 121, it is anchored on the steel truss 122 through the anchor 21. The other end passes through the connecting ring 31 on the top of the prefabricated pile 3 and is then folded in half and tightened by the fixing buckle 22 to achieve hinged connection. , see Figure 7. There are no special requirements for the design of the steel truss 123 and the guide hole 121, but it is necessary to ensure that the pulling force direction of the anchor cable 2 points to the center of the wind power monopile foundation 1, and the plane provided by the steel plate 122 and the steel truss 123 should be in the tangent direction of the steel casing 11 Keep it consistent, and the guide hole 121 needs to guide the pulling force of the anchor cable 2 toward the center of the foundation 1.

As shown in Figure 6, several prefabricated piles 3 are driven into the composite foundation 4 around the wind power single pile foundation 1 to form ground anchors. In this embodiment, the prefabricated piles 3 are in two layers, with the wind power single pile foundation 1 as the center. Evenly arranged in a ring. The composite foundation 4 is made by injecting cement into the soil and mixing and strengthening it. The prefabricated piles 3 are driven into the composite foundation 4 to form a reaction system. In this embodiment, the reinforcement depth of the composite foundation 4 is 15m, and the radius of the reinforcement area is 40m. Prefabricated pile 3 uses a steel pipe pile with a diameter of 0.6m, a wall thickness of 0.03m, and a burial depth of 12m. The radius of the outer ring of prefabricated piles 3 from the center of the wind power single pile foundation 1 is 30m, and the radius of the inner ring is 24m.

The following introduces the method of using the above-mentioned reinforcement and correction devices to strengthen and correct offshore wind power single pile foundations, including the following steps:

(1) Clarify the correction target, ascertain the scope and shape of the scour pits around the wind power single pile foundation 1, as well as the horizontal displacement and inclination of the wind power single pile foundation 1, and design a correction and reinforcement plan;

(2) Treat the scour pit and fill it with a mixture of sand and gravel;

(3) Within the designed foundation reinforcement range, use a mixing pile driver to spray cement into the soil and stir it thoroughly. The cement and soil will harden to form a composite foundation 4;

(4) When the cement and soil are not fully hardened, drive several prefabricated piles 3 at the designed position to form ground anchors, and weld the connecting rings 31 on the tops of the prefabricated piles 3;

(5) Set a steel casing 11 at the connection point between the wind power monopile foundation 1 and the tower. The steel casing 11 and the wind power monopile foundation 1 are connected with high-strength bolts. The surface of the steel casing 11 is evenly distributed in an annular shape and several steel frames are welded and fixed. structure12;

(6) Install anchor cables 2 to connect prefabricated piles 3 and the corresponding steel frame structure 12;

(7) Tension specific anchor cables 2 in a graded and sequential manner, and ensure that the direction of the resultant tensile force provided by the anchor cables 2 points to the center of the foundation and is opposite to the original horizontal displacement direction of the wind power single pile foundation 1;

As shown in Figure 8, by tensioning a specific anchor cable 2, an external tensile force is provided to the wind power monopile foundation 1 to achieve the purpose of correction. The tensile force exerted by each anchor cable 2 is the same, and its size is calculated using the following formula:

Q is the tensile force exerted by each anchor cable 2; E is the elastic modulus of the anchor cable 2; A is the cross-sectional area of the anchor cable 2; w is the horizontal displacement of the connection between the wind power monopile foundation 1 and the tower; i is From the direction perpendicular to the w direction to the i-th anchor cable within the range of 90°, in this embodiment, i=4; θ=22.5°; j is the number of layers of prefabricated piles 3 from outside to inside. In this embodiment, Arrange two layers, j = 1, 2; α _j is the angle between the anchor cable 2 corresponding to the j-th layer pile and the sea level, l _j is the length of the j-th layer anchor cable 2; α ₁ is the outermost anchor cable 2 The angle between the anchor cable 2 and the sea level, α ₂ is the angle between the innermost anchor cable 2 and the sea level.

The tensioning sequence of anchor cable 2 is: the two anchor cables A in the direction perpendicular to the horizontal displacement w are first stretched, then the adjacent anchor cable B that can provide the opposite pulling force in the w direction is symmetrically stretched, and then in sequence For C and D, the anchor cable E, which is consistent with the w direction and passes through the center of the foundation, is finally tensioned. During the correction process of the wind power single pile foundation 1, the direction of the resultant pulling force provided by the anchor cables A, B, C, D, and E must point to the center of the foundation and be opposite to the original horizontal displacement w direction of the wind power single pile foundation 1.

(8) After the correction is completed, tension and fix the remaining anchor cables 2 in sequence so that all anchor cables 2 maintain a certain tension and the resultant force is zero. As shown in Figure 9, A ₁ is stretched first, then B ₁ , and again is C ₁ , and finally tensions D ₁ .

Claims

A device for reinforcing and correcting deviations of offshore wind power monopile foundations, which is characterized by: including a steel casing (11) that is sleeved and fixed on the wind power monopile foundation (1). The steel casing (11) has a circumferential edge. A number of steel frame structures (12) are evenly fixed; a composite foundation (4) is provided around the wind power single pile foundation (1), and the composite foundation (4) is formed by injecting cement into the soil and stirring to reinforce it; the composite foundation (4) 4) is provided with several prefabricated piles (3) used as ground anchors. The plurality of prefabricated piles (3) are centered on the wind power single pile foundation (1) and evenly arranged in a ring; the steel frame structure (12) and the prefabricated piles ( 3) Connected by anchor cable (2);

The steel frame structure (12) includes a connected steel truss (123) and a steel plate (122). A guide hole (121) is reserved on the steel plate (122) to guide the tensile force of the anchor cable (2) toward the wind power monopile foundation. (1) Center; the anchor cable (2) passes through the guide hole (121) and is fixed on the steel truss (123) through the anchor connector (21);

There is a connecting ring (31) on the top of the prefabricated pile (3). The anchor cable (2) passes through the connecting ring (31) and is folded in half and tightened by the fixed buckle (22);

The connecting ring (31) is provided with a groove to prevent the anchor cable (2) from sliding;

Tension specific anchor cables (2) to exert external pulling force on the wind power monopile foundation (1) to achieve deviation correction;

During the correction process, the tensioning sequence of the anchor cables (2) is: the two anchor cables (2) in the direction perpendicular to the horizontal displacement w are tensioned first, and then the two anchor cables (2) are adjacent and can provide The anchor cables (2) with opposite tensile force in the w direction are tensioned symmetrically in sequence. The horizontal component force is opposite to the w direction and passes through the center of the wind power monopile foundation (1). The anchor cable (2) is finally tensioned to ensure the specific anchor cable (2). ) The direction of the resultant tensile force provided by the wind power monopile foundation (1) points to the center of the wind power monopile foundation (1) and is opposite to the horizontal displacement w direction of the wind power monopile foundation (1);

After the correction is completed, the remaining anchor cables (2) are sequentially stretched and fixed so that all anchor cables (2) maintain a certain tension and the resultant force is zero.
The device for offshore wind power single pile foundation reinforcement and deviation correction according to claim 1, characterized in that: the annularly arranged prefabricated piles (3) are one or more layers.
The device for strengthening and correcting offshore wind power monopile foundations according to claim 1, characterized in that: the steel casing (11) and the wind power monopile foundation (1) are fixedly connected using high-strength bolts (111).
A method for strengthening and correcting deviations of offshore wind power single pile foundations, characterized by adopting the device for strengthening and correcting deviations of offshore wind power single pile foundations according to claim 1, and the method includes the following steps:

(1) Fill the scour pit;

(2) Within the designed reinforcement range of the wind power single pile foundation (1), use a pile mixing machine to spray cement into the soil and stir it thoroughly. The cement and soil will harden to form a composite foundation (4); when the cement and soil are not fully When hardening occurs, drive several prefabricated piles (3) at the designed location;

(3) Set a steel casing (11) on the wind power monopile foundation (1) and connect it with high-strength bolts (111);

(4) Install anchor cables (2) to connect the steel frame structure (12) on the surface of the prefabricated piles (3) and the steel casing (11);

(5) Tension specific anchor cables (2) to exert external pulling force on the wind power monopile foundation (1) to achieve deviation correction;

During the correction process, the tensioning sequence of the anchor cables (2) is: the two anchor cables (2) in the direction perpendicular to the horizontal displacement w are tensioned first, and then the two anchor cables (2) are adjacent and can provide The anchor cables (2) with opposite tension in the w direction are tensioned symmetrically in sequence, The horizontal component force is opposite to the w direction and passes through the final tension of the anchor cable (2) at the center of the wind power monopile foundation (1), ensuring that the direction of the resultant tensile force provided by the specific anchor cable (2) points to the center of the wind power monopile foundation (1) and The horizontal displacement w direction of the wind power monopile foundation (1) is opposite;

(6) After the correction is completed, tension and fix the remaining anchor cables (2) in sequence so that all anchor cables (2) maintain a certain tension and the resultant force is zero.
The method for strengthening and correcting offshore wind power single pile foundations according to claim 4, characterized in that in step (5), the pulling force exerted by each anchor cable (2) is the same, and the pulling force is calculated using the following formula:

Q is the tensile force exerted by each anchor cable (2); E is the elastic modulus of the anchor cable (2); A is the cross-sectional area of the anchor cable (2); w is the wind power monopile foundation (1) and the steel casing (11) Horizontal displacement of the connection position; i is the i-th anchor cable within the range of 90° from the direction perpendicular to the w direction, i=1,2,…,n; θ=90°/n; j is The number of layers of prefabricated piles (3) from outside to inside, j=1, 2, 3,..., m; l j is the length of the anchor cable (2) on the jth layer; α j is the corresponding prefabricated pile (3) on the jth layer The angle between the anchor cable (2) and the sea level.