Offshore wind turbine three-layer composite scour-resistant anticorrosion pile foundation and construction method thereof

Abstract

The application discloses a kind of offshore wind turbine three-layer composite scouring-resistant anticorrosion pile foundation and its construction method.The pile foundation includes flexible hollow protective outer layer, center concrete connecting layer and steel pipe pile core layer arranged in turn from outside to inside, flexible hollow protective outer layer includes wall body in cylindrical shape and flexible energy dissipation skirt in flared shape, the wall body and flexible energy dissipation skirt are hollow inside, a cavity is enclosed by two, and cavity two ends are respectively provided with several exhaust air vents, water inlet hole.Down flexible hollow protective outer layer, seawater enters water through water inlet hole, exhaust air vent exhausts, and naturally sinks to seabed under the action of dead weight, then install steel pipe pile core layer, lay out inclinometer in the annular cavity formed, and pour underwater concrete to form center concrete connecting layer.The application can realize scouring-resistant, anticorrosion, installation positioning and bending deformation monitoring of offshore wind turbine pile foundation, improve the overall stability and long-term service safety of pile foundation in marine environment.

Description

Technical Field

[0001] This invention relates to the field of offshore wind power foundations, specifically a three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines and its construction method. Background Technology

[0002] As offshore wind power gradually develops towards deeper waters, larger capacity, and higher power, the foundation structure of offshore wind turbines is constantly exposed to a complex marine dynamic environment, subject to the combined effects of wind loads, wave loads, ocean current loads, tidal forces, and vibration loads from the operation of the upper turbine. Steel pipe pile foundations, as a widely used foundation type for offshore wind turbines, offer advantages such as high construction efficiency, good load-bearing capacity, and strong adaptability. However, during long-term service, offshore wind turbine steel pipe pile foundations typically face problems such as seabed erosion around the piles, seawater corrosion, bending deformation caused by horizontal loads, and degradation of overall foundation stability.

[0003] First, under the combined action of waves and ocean currents, a complex three-dimensional flow structure forms around the pile foundation, including a horseshoe-shaped vortex in front of the pile, an accelerated flow along the pile side, a wake vortex behind the pile, and a downward flow developing along the pile wall. This hydrodynamic structure continuously disturbs the surface soil of the seabed around the pile, causing sediment particles to be activated, suspended, and transported, thus forming localized scour pits around the pile. As the scour depth gradually increases, the effective embedment depth of the pile foundation decreases, and the horizontal restraint provided by the shallow soil around the pile reduces, leading to a decrease in the horizontal bearing capacity and overturning resistance of the pile foundation. In severe cases, this may cause excessive foundation displacement, cumulative tilting, or even structural instability.

[0004] Secondly, chloride ions, dissolved oxygen, sulfates, marine microorganisms, and repeated wet-dry cycles in the marine environment can significantly corrode steel pipe piles. Especially in the splash zone, tidal zone, and near-seabed scouring zone, the protective layer on the steel structure surface is easily damaged by wave impact, sand abrasion, and collisions with floating debris. Once the anti-corrosion layer is locally damaged, corrosive media in the seawater can quickly penetrate the steel surface, inducing pitting corrosion, crevice corrosion, and electrochemical corrosion, thereby weakening the load-bearing capacity and durability of the steel pipe pile section.

[0005] Furthermore, offshore wind turbine pile foundations are prone to bending deformation under long-term horizontal cyclic loads. Existing pile foundation structures typically only monitor foundation displacement or wind turbine tower tilt through external monitoring methods after construction is completed. They lack internal deformation monitoring structures integrated with the pile foundation structure itself, making it difficult to promptly grasp the attitude changes, bending deformation, and long-term service status of the pile body and composite foundation structure during installation and operation.

[0006] Existing scour protection measures for offshore wind turbine foundations mainly include rockfill protection, sand sheet protection, concrete facing blocks, scour pads, and scour sleeves. While these measures can reduce scour around the piles to some extent, they still have the following shortcomings: First, most protective measures are post-installed structures with a low degree of integration with the main pile foundation, making them prone to local erosion, slippage, or failure under long-term wave and current action; second, conventional scour protection structures are mostly rigid protections, which are insufficiently adaptable to seabed deformation and the evolution of scour pits; third, scour protection, corrosion prevention, and deformation monitoring functions are independent of each other, resulting in complex construction procedures and high overall maintenance costs; and fourth, existing structures cannot simultaneously address pile foundation positioning, protective layer formation, and long-term monitoring during service life in the initial installation phase. Summary of the Invention

[0007] The purpose of this invention is to provide a three-layer composite anti-erosion and corrosion-resistant pile foundation for offshore wind turbines, comprising a flexible hollow protective outer layer, a central concrete connecting layer, and a steel pipe pile core layer.

[0008] The flexible hollow protective outer layer is a rotating structure with an internal hollow structure and open top and bottom ends. The inner hole of the flexible hollow protective outer layer is referred to as the receiving hole.

[0009] The flexible hollow protective outer layer includes a cylindrical wall in the upper part and a trumpet-shaped flexible energy-dissipating skirt in the lower part. Both the wall and the flexible energy-dissipating skirt are hollow, forming a cavity. The end of the wall away from the flexible energy-dissipating skirt has several vent holes at intervals, and the end of the flexible energy-dissipating skirt away from the wall has several water inlet holes at intervals. The vent holes and water inlet holes are all connected to the cavity.

[0010] When the flexible hollow protective outer layer is deployed, seawater enters the cavity of the flexible hollow protective outer layer through the water inlet hole and exhausts air through the vent hole, thereby balancing the pressure.

[0011] The inner wall of the wall is provided with a serrated structure.

[0012] The steel pipe pile core layer is coaxially disposed within the receiving hole of the flexible hollow protective outer layer. An annular cavity is formed between the outer wall of the steel pipe pile core layer and the hole wall of the flexible hollow protective outer layer, and the annular cavity is filled with concrete to form a central concrete connecting layer.

[0013] Multiple inclinometer tubes I are pre-embedded in the central concrete connecting layer. Multiple inclinometer tubes II are spaced apart in the cavity of the flexible hollow protective outer layer.

[0014] Furthermore, the wall and the flexible energy-dissipating skirt are integrally formed structures.

[0015] Furthermore, the flexible hollow protective outer layer is made of modified high-density polyethylene, reinforced polymer composite material, or seawater corrosion-resistant flexible composite material.

[0016] Furthermore, the serrated structure is arranged in a circumferential, vertical, or spiral direction along the wall.

[0017] Furthermore, the flexible energy-dissipating skirt 104 is provided with circumferential reinforcing rings I, II, and III at intervals on its outer or inner wall. The circumferential reinforcing rings I, II, and III are respectively located at the upper, middle, and bottom of the flexible hollow protective outer layer.

[0018] Furthermore, the central concrete bonding layer is an underwater non-dispersible concrete layer, a chloride-resistant concrete layer, a fiber-reinforced concrete layer, or a high-durability marine concrete layer.

[0019] Furthermore, the steel pipe pile core layer includes a coaxially arranged anti-corrosion sealing layer, a high-strength steel pipe pile body, and an impact-resistant protective layer.

[0020] The high-strength steel pipe pile is a hollow steel pipe pile with open top and bottom ends. The inner wall of the steel pipe pile is coated with an anti-corrosion sealing layer, and the outer wall is fixed with an impact-resistant protective layer. The impact-resistant protective layer is in contact with the central concrete bonding layer.

[0021] Furthermore, during the installation of the flexible hollow protective outer layer, the end of the flexible energy-dissipating skirt away from the wall needs to be in contact with the target seabed surface.

[0022] Furthermore, the inclinometer probe is fixed in the guide groove of inclinometer tube II to monitor the tilting state of the flexible hollow protective outer layer during installation.

[0023] After the installation of the three-layer composite anti-erosion and anti-corrosion pile foundation for the offshore wind turbine is completed, and during operation, the probe of the inclinometer is lowered to the bottom of the inclinometer tube I along the guide groove of inclinometer tube I. After the probe reaches the bottom, the probe is pulled up and the reading is taken at a fixed point to monitor the overall bending deformation after the pile foundation is installed and during operation.

[0024] Another objective of this invention is to provide a construction method for a three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines, comprising the following steps:

[0025] S1. Based on the design location of the offshore wind turbine pile foundation, the flexible hollow protective outer layer is hoisted or deployed to the target sea area.

[0026] S2. Lower the flexible hollow protective outer layer. Seawater enters the flexible hollow protective outer layer through the water inlet hole and air is discharged through the vent hole, so that the flexible hollow protective outer layer naturally sinks to the seabed surface under its own weight and the weight increase from the water inlet.

[0027] The flexible hollow protective outer layer is equipped with a clinometer tube II. During the lowering and installation process, the sinking attitude and tilting state of the flexible hollow protective outer layer are monitored by the clinometer probe fixed in the guide groove of the clinometer tube II.

[0028] S3. The steel pipe pile core layer is coaxially assembled into the inner hole of the flexible hollow protective outer layer, and the steel pipe pile core layer is pressed into or sunk into the seabed.

[0029] S4. Several layers of inclinometer tubes I are installed at intervals in the annular cavity formed between the steel pipe pile core layer and the flexible hollow protective outer layer.

[0030] S5. Pour underwater concrete into the annular cavity to form a central concrete connecting layer.

[0031] S6. After the central concrete connecting layer has solidified and hardened, a three-layer composite anti-erosion and anti-corrosion pile foundation is formed, consisting of a flexible hollow protective outer layer, a central concrete connecting layer, and a steel pipe pile core layer.

[0032] The technical effects of this invention are undeniable, and its beneficial effects are as follows:

[0033] 1. Forming a three-layer composite load-bearing and protection system

[0034] This invention comprises a three-layer composite structure consisting of a flexible hollow protective outer layer, a central concrete connecting layer, and a steel pipe pile core. The outer layer is responsible for scour prevention, energy dissipation, and seabed adhesion; the middle layer is responsible for connection, force transmission, and overall reinforcement; and the inner layer is responsible for the main load-bearing capacity and providing bending stiffness. The three layers work together to significantly improve the load-bearing stability and service durability of offshore wind turbine pile foundations in complex marine environments.

[0035] 2. It has both erosion resistance and overturning resistance functions.

[0036] The trumpet-shaped flexible energy-dissipating skirt increases the contact area between the bottom of the pile foundation and the seabed, and gradually adheres to the seabed surface under the action of waves and currents. This structure can weaken the disturbance of horseshoe vortices, wake vortices and downflows on the seabed soil, reduce the local scour intensity around the pile, and improve the stability of the pile foundation bottom by compacting the seabed, thereby enhancing the overturning resistance of the pile foundation.

[0037] 3. Improve the corrosion resistance and impact resistance of steel pipe piles.

[0038] The steel pipe pile core layer is equipped with an anti-corrosion sealing layer and an impact-resistant protective layer, which can simultaneously improve the steel pipe pile's resistance to seawater corrosive media, sand abrasion, wave impact and construction collisions, delay the development of steel structure corrosion damage, and improve the durability of offshore wind turbine foundations throughout their entire life cycle.

[0039] 4. Integrated construction positioning and structural protection

[0040] The flexible hollow protective outer layer allows water to enter through the bottom water inlet and air to escape through the venting holes. It can sink naturally under its own weight and the added weight from the water injection, and after sinking to the seabed, it provides auxiliary positioning for the installation of the steel pipe pile core layer. Compared to the traditional method of driving piles first and then installing the scour protection structure, this invention combines the positioning, protection, and structural forming processes, reducing construction steps and improving the efficiency of offshore construction.

[0041] 5. Enhance the overall synergistic effect of the three-layer structure.

[0042] The interlocking sawtooth structure on the inner wall forms a mechanical interlocking connection with the central concrete connecting layer, and multiple circumferential reinforcing rings further restrict the deformation of the flexible hollow protective outer layer, so that a reliable force transmission system is formed between the flexible outer layer, the concrete connecting layer and the steel pipe pile core layer, thereby improving the overall stiffness and bending resistance of the composite pile foundation.

[0043] 6. Implement deformation monitoring during installation and operation.

[0044] Inclined tube I and inclined tube II are used to monitor the attitude changes of the flexible hollow protective outer layer and the overall structure of the composite pile foundation, respectively. They can determine the verticality of sinking and the center alignment status in real time during installation, and continuously monitor the bending deformation and tilting development of the pile foundation during the operation phase, providing data support for the safety assessment and operation and maintenance decision-making of offshore wind turbine foundations. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the overall structure of the three-layer composite anti-erosion and corrosion-resistant pile foundation for offshore wind turbines according to the present invention;

[0046] Figure 2 This is a cross-sectional view of the overall structure of the three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines according to the present invention;

[0047] Figure 3 This is a schematic diagram of the internal reinforcement structure of the flexible hollow protective outer layer and the arrangement of the inclinometer tubes of the present invention;

[0048] Figure 4 This is a top view of the three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines according to the present invention;

[0049] Figure 5 This is a schematic diagram showing the arrangement of the bottom water inlet and the trumpet-shaped flexible energy dissipation skirt of the present invention.

[0050] Figure 6 The diagram shows the multi-layer protective structure of the steel pipe pile core layer of this invention:

[0051] In the diagram: 1. Flexible hollow protective outer layer; 2. Central concrete connecting layer; 3. Steel pipe pile core layer; 4. Inclinometer tube I; 5. Inclinometer tube II; 6. Circumferential reinforcing ring I; 7. Circumferential reinforcing ring II; 8. Circumferential reinforcing ring III; 101. Wall; 102. Vent hole; 103. Serrated structure; 104. Flexible energy dissipation skirt; 105. Water inlet / injection hole; 301. Anti-corrosion sealing layer; 302. High-strength steel pipe pile main body; 303. Impact-resistant protective layer. Detailed Implementation

[0052] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0053] Example 1:

[0054] See Figures 1-5 A three-layer composite anti-erosion and corrosion-resistant pile foundation for offshore wind turbines includes a flexible hollow protective outer layer 1, a central concrete connecting layer 2, and a steel pipe pile core layer 3.

[0055] The flexible hollow protective outer layer 1 is a rotating structure with an internal hollow structure and open top and bottom ends. The inner hole of the flexible hollow protective outer layer 1 is referred to as the receiving hole.

[0056] The flexible hollow protective outer layer 1 includes a cylindrical wall 101 in the upper half and a trumpet-shaped flexible energy-dissipating skirt 104 in the lower half. The small end of the flexible energy-dissipating skirt 104 is transitionally connected to the wall 101.

[0057] The wall 101 and the flexible energy-dissipating skirt 104 are hollow, forming a cavity together. The end of the wall 101 away from the flexible energy-dissipating skirt 104 is provided with a plurality of vent holes 102 at intervals, and the end of the flexible energy-dissipating skirt 104 away from the wall 101 is provided with a plurality of water inlet holes 105 at intervals. The vent holes 102 and the water inlet holes 105 are all connected to the cavity.

[0058] When the flexible hollow protective outer layer 1 is lowered, seawater enters the cavity of the flexible hollow protective outer layer 1 through the water inlet hole 105 and exhausts air through the vent hole 102, thereby balancing the pressure. Until the bottom of the flexible hollow protective outer layer 1, the large end of the flexible energy-dissipating skirt 104 contacts the seabed and gradually spreads and adheres to the seabed surface, forming the initial protection zone for erosion protection of the foundation perimeter.

[0059] The inner wall of the wall 101 is provided with a sawtooth structure 103.

[0060] The steel pipe pile core layer 3 is coaxially disposed within the receiving hole of the flexible hollow protective outer layer 1. An annular cavity is formed between the outer wall of the steel pipe pile core layer 3 and the wall of the receiving hole of the flexible hollow protective outer layer 1. The annular cavity is filled with concrete, thus forming a central concrete connecting layer 2. The central concrete connecting layer 2 serves as a connecting and filling layer between the flexible hollow protective outer layer 1 and the steel pipe pile core layer 3, and also as a force transmission transition layer and a stiffness enhancement layer, enabling the external flexible protective structure and the internal steel pipe pile bearing structure to form an integral composite foundation.

[0061] Multiple inclinometer tubes I4 are pre-embedded in the central concrete connecting layer 2. Multiple inclinometer tubes II5 are spaced apart in the cavity of the flexible hollow protective outer layer 1.

[0062] Example 2:

[0063] The main structure of this embodiment is the same as that of embodiment 1. Furthermore, the wall 101 and the flexible energy-dissipating skirt 104 are integrally formed.

[0064] Example 3:

[0065] The main structure of this embodiment is the same as any one of embodiments 1 to 2. Furthermore, the flexible hollow protective outer layer 1 is made of modified high-density polyethylene, reinforced polymer composite material or seawater corrosion resistant flexible composite material.

[0066] The modified high-density polyethylene typically has a density of 0.941–0.965 g / cm³, which is about 3%–6% higher than that of ordinary low-density polyethylene.

[0067] The detailed component ratios of the reinforced polymer composite material are shown in Table 1.

[0068] The detailed component ratios of the seawater corrosion-resistant flexible composite material are shown in Table 2.

[0069] Table 1. Detailed Distribution Ratio of Each Component in Reinforced Polymer Composites

[0070]

[0071] Table 2. Detailed breakdown of component proportions in seawater corrosion-resistant flexible composite materials.

[0072]

[0073] Example 4:

[0074] The main structure of this embodiment is the same as any one of embodiments 1 to 3. Furthermore, the sawtooth structure 103 is arranged in the circumferential, vertical or spiral direction along the wall 101.

[0075] Example 5:

[0076] The main structure of this embodiment is the same as any one of embodiments 1 to 4. Further, see [link to embodiment 1]. Figure 3 The flexible energy-dissipating skirt 104 has circumferential reinforcing rings I6, II7, and III8 spaced apart on its outer or inner wall. These circumferential reinforcing rings I6, II7, and III8 are respectively positioned at the upper, middle, and bottom of the flexible hollow protective outer layer 1. Each circumferential reinforcing ring is used to improve the circumferential stiffness of the flexible hollow protective outer layer 1, limiting its excessive deformation during water injection and sinking, installation of the steel pipe pile core layer 3, and underwater concrete pouring.

[0077] Example 6:

[0078] The main structure of this embodiment is the same as any one of embodiments 1 to 5. Furthermore, the central concrete connecting layer 2 is an underwater non-dispersible concrete layer, a chloride-resistant concrete layer, a fiber-reinforced concrete layer, or a high-durability marine concrete layer.

[0079] The high-durability marine concrete layer refers to a low-permeability, highly chloride-resistant concrete protective layer designed for seawater, tidal zones, splash zones, and chloride-erosion environments. Its design strength grade should preferably be no lower than C40–C50, the water-cement ratio should preferably be controlled between 0.35–0.40, and the cementitious material dosage should preferably be 420–500 kg / kg. Furthermore, the density of the matrix and its resistance to chloride ion penetration are improved by incorporating mineral admixtures such as mineral powder, fly ash, and silica fume.

[0080] Furthermore, the components and their mass fractions of the underwater non-dispersible concrete layer, chloride-resistant concrete layer, fiber-reinforced concrete layer, and high-durability marine concrete layer are as follows:

[0081] The underwater non-dispersible concrete layer includes cement, mineral powder, silica fume, water, sand, crushed stone, underwater non-dispersant agent and water-reducing agent, with the following mass fractions: 350:100:20:175:750:930:4:5.

[0082] The chloride-resistant concrete layer consists of cement, mineral powder, fly ash, silica fume, water, sand, crushed stone, water-reducing agent, nano silica, steel reinforcement corrosion inhibitor, silane water-repellent agent, and basalt fiber, with the following mass fractions: 350:80:50:25:165:740:920:5:12:10:5:2.

[0083] The fiber-reinforced concrete layer includes cement, mineral powder, fly ash, silica fume, water, sand, crushed stone, water-reducing agent, basalt fiber, polypropylene fiber, nano silica, expansion agent and silane coupling agent, with the following mass fractions: 340:70:40:20:165:760:900:5:6:2:10:15:4.

[0084] The high-durability marine concrete layer includes cement, mineral powder, fly ash, silica fume, water, sand, crushed stone, water-reducing agent, nano-silica, metakaolin, air-entraining agent and basalt fiber, with the following mass fractions: 330:100:60:25:160:730:930:5:12:20:1:3.

[0085] Example 7:

[0086] The main structure of this embodiment is the same as any one of embodiments 1 to 6. Further, see [link to embodiment 1-6]. Figure 6 The steel pipe pile core layer 3 includes a corrosion-resistant sealing layer 301, a high-strength steel pipe pile body 302, and an impact-resistant protective layer 303, which are coaxially arranged.

[0087] The high-strength steel pipe pile body 302 is a hollow steel pipe pile with open upper and lower ends. The inner wall of the steel pipe pile is coated with an anti-corrosion sealing layer 301 to prevent the intrusion of corrosive media such as seawater, chloride salts and dissolved oxygen. The outer wall is fixed with an impact-resistant protective layer 303 to improve the ability of the steel pipe pile core layer 3 to resist mechanical impact, sand abrasion and local collision during transportation, hoisting, pile driving and service.

[0088] The impact-resistant protective layer 303 is in contact with the central concrete connecting layer 2.

[0089] Furthermore, in this embodiment, the high-strength steel pipe pile body 302 is made of S420 / S460 grade high-strength marine structural steel, with a yield strength of not less than 420 MPa / 460 MPa. Before applying the anti-corrosion sealing layer 301, the inner wall of the high-strength steel pipe pile body 302 needs to be sandblasted. The impact-resistant protective layer 303 uses a prefabricated segmented sheath or arc-shaped protective plate, mechanically secured with 316L stainless steel clamps and bolts, and the upper and lower ends of the prefabricated segmented sheath or arc-shaped protective plate and the longitudinal joints are sealed with seawater-resistant sealant.

[0090] Example 8:

[0091] The main structure of this embodiment is the same as any one of embodiments 1 to 7. Furthermore, during the installation of the flexible hollow protective outer layer 1, the end of the flexible energy dissipation skirt 104 away from the wall 101 needs to be in contact with the target seabed surface.

[0092] Example 9:

[0093] The main structure of this embodiment is the same as any one of embodiments 1 to 8. Furthermore, the inclinometer probe is fixed in the guide groove of the inclinometer tube II 5 and is used to monitor the tilting state of the flexible hollow protective outer layer 1 during the installation process.

[0094] After the installation of the three-layer composite anti-erosion and anti-corrosion pile foundation for the offshore wind turbine is completed, and during operation, the probe of the inclinometer is lowered to the bottom of the inclinometer tube I4 along the guide groove of the inclinometer tube I4. After the probe reaches the bottom, the probe is pulled up and the reading is taken at a fixed point to monitor the overall bending deformation after the pile foundation is installed and during operation.

[0095] Example 10:

[0096] A construction method for a three-layer composite scour-resistant and corrosion-resistant pile foundation for an offshore wind turbine, based on any one of embodiments 1 to 9, includes the following steps:

[0097] S1. Based on the design location of the offshore wind turbine pile foundation, the flexible hollow protective outer layer 1 is hoisted or deployed to the target sea area.

[0098] S2. Lower the flexible hollow protective outer layer 1. Seawater enters the flexible hollow protective outer layer 1 through the water inlet hole 105 and exhausts air through the vent hole 102, causing the flexible hollow protective outer layer 1 to sink naturally to the seabed surface under its own weight and the weight increase from the water inlet.

[0099] The flexible hollow protective outer layer 1 is equipped with an inclinometer tube II 5 inside. During the lowering and installation process, the sinking attitude and tilting state of the flexible hollow protective outer layer 1 are monitored by the inclinometer probe fixed in the guide groove of the inclinometer tube II 5.

[0100] S3. The steel pipe pile core layer 3 is coaxially assembled into the inner hole of the flexible hollow protective outer layer 1, and the steel pipe pile core layer 3 is pressed into or sunk into the seabed.

[0101] S4. Several layers of inclinometer tubes I4 are installed at intervals in the annular cavity formed by the steel pipe pile core layer 3 and the flexible hollow protective outer layer 1.

[0102] S5. Pour underwater concrete into the annular cavity to form the central concrete connecting layer 2.

[0103] S6. After the central concrete connecting layer 2 has solidified and hardened, a three-layer composite anti-erosion and anti-corrosion pile foundation is formed, consisting of a flexible hollow protective outer layer 1, a central concrete connecting layer 2, and a steel pipe pile core layer 3.

[0104] Example 11:

[0105] The main structure of this embodiment is the same as any one of embodiments 1 to 10. Furthermore, the present invention forms a three-layer composite structure system arranged sequentially from the outside to the inside by setting a central concrete connecting layer 2 and a flexible hollow protective outer layer 1 outside the steel pipe pile core layer 3, so that the pile foundation can simultaneously have multiple functions such as flexible scour prevention, steel structure corrosion prevention, concrete connection reinforcement, installation positioning and deformation monitoring.

[0106] To achieve the above objectives, the present invention adopts the following technical solution:

[0107] A three-layer composite anti-erosion and corrosion-resistant pile foundation for offshore wind turbines includes a flexible hollow protective outer layer 1, a central concrete connecting layer 2, and a steel pipe pile core layer 3 arranged sequentially from the outside to the inside.

[0108] The flexible hollow protective outer layer 1 is set on the outermost side of the pile foundation, which is used to directly contact the seawater and seabed, and plays a role in preventing erosion, protecting, buffering and dissipating energy and assisting in positioning of the internal structure.

[0109] The flexible hollow protective outer layer 1 includes a wall 101, an exhaust vent, a sawtooth structure 103, a trumpet-shaped flexible energy-dissipating skirt 104, and a bottom water inlet.

[0110] The flexible hollow protective outer layer 1 is preferably made of modified high-density polyethylene, reinforced polymer composite material or seawater corrosion resistant flexible composite material, and has certain flexibility, wear resistance, impact resistance and seawater corrosion resistance.

[0111] The flexible hollow protective outer layer 1 has a hollow structure, with a cylindrical structural wall 101 on the upper part and an outwardly extending trumpet-shaped flexible energy-dissipating skirt 104 on the lower part.

[0112] The exhaust vent is located on the upper part or the upper side of the flexible hollow protective outer layer 1, and is used to discharge the internal air during the sinking process of the flexible hollow protective outer layer 1, and to balance the pressure between the internal cavity and the external seawater.

[0113] The bottom water inlet hole is located at or near the bottom of the flexible hollow protective outer layer 1, and is used to allow seawater to enter the internal cavity of the flexible hollow protective outer layer 1, so that the flexible hollow protective outer layer 1 gradually sinks to the seabed surface under its own weight and the weight increase effect of the water inlet.

[0114] The trumpet-shaped flexible energy-dissipating skirt 104 is disposed at the bottom outer edge of the flexible hollow protective outer layer 1, extending radially outward and forming a large contact area with the seabed surface. When waves and ocean currents act around the pile foundation, the horseshoe-shaped vortex formed in front of the pile, the flow around the pile side, the wake vortex behind the pile, and the downflow developing along the pile body are weakened in velocity and vortex intensity after contacting the trumpet-shaped flexible energy-dissipating skirt 104. At the same time, the hydrodynamic action exerts a downward pressing effect on the trumpet-shaped flexible energy-dissipating skirt 104, causing it to gradually conform to the seabed surface, thereby inhibiting the initiation of soil movement around the pile, reducing the development of local scour pits, and improving the overall stability of the seabed around the pile foundation.

[0115] The flexible hollow protective outer layer 1 has a sawtooth structure 103 inside. The sawtooth structure 103 can be arranged in a circumferential, vertical, or spiral direction along the inner wall of the flexible hollow protective outer layer 1. After the central concrete connecting layer 2 is poured and cured, a mechanical interlocking effect is formed between the central concrete connecting layer 2 and the sawtooth structure 103, thereby enhancing the connection strength between the flexible hollow protective outer layer 1 and the central concrete connecting layer 2 and improving the overall coordinated load-bearing performance of the three-layer composite pile foundation.

[0116] The flexible hollow protective outer layer 1 may also be provided with an upper circumferential reinforcing ring I6, a middle circumferential reinforcing ring II7, and a lower circumferential reinforcing ring III8 on its outer side or inside.

[0117] The circumferential reinforcing ring I6 is disposed in the upper region of the flexible hollow protective outer layer 1, the circumferential reinforcing ring II7 is disposed in the middle region of the flexible hollow protective outer layer 1, and the circumferential reinforcing ring III8 is disposed in the lower region of the flexible hollow protective outer layer 1 or near the trumpet-shaped flexible energy dissipation skirt 104. Each circumferential reinforcing ring is used to improve the circumferential stiffness of the flexible hollow protective outer layer 1 and limit its excessive deformation during water injection sinking, installation of steel pipe pile core layer 3, and underwater concrete pouring.

[0118] The central concrete connecting layer 2 is disposed within the annular space between the flexible hollow protective outer layer 1 and the steel pipe pile core layer 3. The central concrete connecting layer 2 is preferably formed by casting underwater non-dispersible concrete, chloride-resistant concrete, fiber-reinforced concrete, or high-durability marine concrete. This layer serves as both a connecting and filling layer between the flexible hollow protective outer layer 1 and the steel pipe pile core layer 3, and a force-transfer transition layer and a stiffness-enhancing layer, thus forming an integral composite foundation between the external flexible protective structure and the internal steel pipe pile bearing structure.

[0119] The steel pipe pile core layer 3 is located inside the pile foundation and serves as the main load-bearing component.

[0120] The steel pipe pile core layer 3 includes an anti-corrosion sealing layer 301, a high-strength steel pipe pile body 302, and an impact-resistant protective layer 303.

[0121] The anti-corrosion sealing layer 301 is disposed inside the high-strength steel pipe pile body 302 to prevent the intrusion of corrosive media such as seawater, chloride salts and dissolved oxygen; the high-strength steel pipe pile body 302 is used to bear vertical loads, horizontal loads and bending moments; the impact-resistant protective layer 303 is used to improve the ability of the steel pipe pile core layer 3 to resist mechanical impact, sand abrasion and local collision during transportation, hoisting, pile driving and service.

[0122] The flexible hollow protective outer layer 1 is equipped with an inclinometer tube II 5, which is used to monitor the tilt state, verticality, and deformation of the inner and outer layer structures during the sinking and installation process of the flexible hollow protective outer layer 1.

[0123] Several inclinometer tubes I4 are installed in the annular space between the central concrete connecting layer 2 or the flexible hollow protective outer layer 1 and the steel pipe pile core layer 3 to monitor the overall bending deformation, pile body tilt and structural service status after the composite pile foundation is installed and during long-term operation.

[0124] A construction method for a three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines, as described above, includes the following steps:

[0125] S1. According to the design location of the offshore wind turbine pile foundation, the flexible hollow protective outer layer 1 is hoisted or deployed to the target sea area;

[0126] S2. Seawater enters the internal cavity of the flexible hollow protective outer layer 1 through the bottom water inlet hole, and the internal air is discharged through the exhaust vent hole, so that the flexible hollow protective outer layer 1 naturally sinks to the seabed surface under its own weight and the weight increase of water inlet.

[0127] S3. Monitor the sinking attitude and tilting state of the flexible hollow protective outer layer 1 through inclinometer tube II5 to ensure that the flexible hollow protective outer layer 1 maintains the predetermined installation attitude with the seabed after sinking.

[0128] S4. Install the steel pipe pile core layer 3 at the center of the flexible hollow protective outer layer 1, and press or sink the steel pipe pile core layer 3 into the seabed so that the steel pipe pile core layer 3 is aligned with the central axis of the flexible hollow protective outer layer 1.

[0129] S5. Install several inclinometer tubes I4 in the annular space between the flexible hollow protective outer layer 1 and the steel pipe pile core layer 3.

[0130] S6. Pour underwater concrete into the annular cavity between the flexible hollow protective outer layer 1 and the steel pipe pile core layer 3 to form the central concrete connection layer 2.

[0131] S7. After the central concrete connecting layer 2 has solidified and hardened, a three-layer composite anti-erosion and anti-corrosion pile foundation is formed, consisting of a flexible hollow protective outer layer 1, a central concrete connecting layer 2, and a steel pipe pile core layer 3.

[0132] In step S2, the flexible energy-dissipating skirt 104 gradually contacts the seabed surface during the sinking of the flexible hollow protective outer layer 1, and adheres to the seabed under the action of seawater and its own weight.

[0133] In step S6, after the central concrete connecting layer 2 is poured, it forms a mechanical interlocking connection with the sawtooth structure 103 to improve the overall connection strength between the flexible hollow protective outer layer 1, the central concrete connecting layer 2 and the steel pipe pile core layer 3.

[0134] Example 12:

[0135] The main structure of this embodiment is the same as any one of embodiments 1 to 11, and further, as follows: Figure 1 As shown in the figure, this embodiment provides a three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines. The pile foundation includes a flexible hollow protective outer layer 1, a central concrete connecting layer 2, and a steel pipe pile core layer 3. The flexible hollow protective outer layer 1 is located on the outermost side, the central concrete connecting layer 2 is located in the middle, and the steel pipe pile core layer 3 is located at the inner center. Together, these three elements form a composite pile foundation structure that is flexible on the outside and rigid on the inside, with a synergistic effect of rigidity and flexibility, integrating load-bearing and protection.

[0136] like Figure 2 As shown, an annular cavity is reserved between the flexible hollow protective outer layer 1 and the steel pipe pile core layer 3. This annular cavity is used for pouring the central concrete connecting layer 2. After the central concrete connecting layer 2 has cured, it wraps around the steel pipe pile core layer 3 on one hand, and connects to the inner side of the flexible hollow protective outer layer 1 on the other hand, thus forming an integral composite structure. The inclinometer tube I 4 can be arranged in this annular cavity and is wrapped and fixed after the concrete is poured, for long-term monitoring of the overall bending deformation of the pile foundation.

[0137] like Figure 3 As shown, a clinometer tube II 5 is installed inside the flexible hollow protective outer layer 1, and an upper circumferential reinforcing ring, a middle circumferential reinforcing ring and a lower circumferential reinforcing ring are installed.

[0138] Inclinometer II5 can provide real-time feedback on the attitude of the flexible hollow protective outer layer 1 during its sinking process, determining whether it has deviated. The upper, middle, and lower circumferential reinforcing rings are used to enhance the circumferential constraint capacity of the flexible hollow protective outer layer 1 at different heights, preventing local bulging or excessive deformation during water injection sinking, pile driving, and concrete pouring.

[0139] like Figure 4 and Figure 5 As shown, the bottom of the flexible hollow protective outer layer 1 is equipped with a trumpet-shaped flexible energy-dissipating skirt 104 and a bottom water inlet. The trumpet-shaped flexible energy-dissipating skirt 104 extends radially outward along the pile foundation, covering the seabed surface within a certain range around the pile foundation. When the ocean current bypasses the pile foundation, the trumpet-shaped flexible energy-dissipating skirt 104 can change the flow field near the bed surface around the pile, weakening the direct impact of the downflow on the bed surface and reducing the entrapment effect of the horseshoe vortex on the bottom sediment. The bottom water inlet is used for seawater to enter the interior of the flexible hollow protective outer layer 1 during the initial installation phase, promoting its natural settling; after installation, the bottom water inlet can also balance the internal and external water pressure.

[0140] like Figure 6As shown, the steel pipe pile core layer 3 includes an anti-corrosion sealing layer 301, a high-strength steel pipe pile body 302, and an impact-resistant protective layer 303. The anti-corrosion sealing layer 301 can be an epoxy zinc-rich coating, epoxy glass flake coating, polyurea coating, rubber protective layer, or multi-layer composite anti-corrosion coating, used to enhance the seawater corrosion resistance of the steel pipe pile core layer 3. The high-strength steel pipe pile body 302, as the main load-bearing component, is used to withstand the vertical loads, horizontal loads, and bending moments transmitted by the upper wind turbine structure. The impact-resistant protective layer 303 can be installed on the outside or inside of the high-strength steel pipe pile body 302 to improve the steel pipe pile's resistance to mechanical impact and abrasion during hoisting, pile driving, and service.

[0141] During construction, the flexible hollow protective outer layer 1 is first hoisted or deployed to the designed location using a construction vessel, based on the design coordinates of the offshore wind turbine foundation. After the flexible hollow protective outer layer 1 is submerged in seawater, seawater enters its internal cavity through the bottom water inlet, while internal air is discharged through the exhaust vent. As seawater gradually fills the internal cavity of the flexible hollow protective outer layer 1, its overall weight increases, and it gradually sinks to the seabed surface under the influence of gravity.

[0142] During the sinking process of the flexible hollow protective outer layer 1, its attitude change is monitored in real time by inclinometer II 5. When the monitoring results show that the flexible hollow protective outer layer 1 is tilted, its attitude can be adjusted by hoisting equipment, temporary traction device or local counterweight to keep it in the predetermined vertical state or the designed installation posture.

[0143] When the bottom of the flexible hollow protective outer layer 1 comes into contact with the seabed, the trumpet-shaped flexible energy-dissipating skirt 104 gradually spreads out and adheres to the seabed surface, forming the initial protection zone for scour protection on the outer perimeter of the foundation.

[0144] Subsequently, the steel pipe pile core layer 3 is hoisted to the center position inside the flexible hollow protective outer layer 1, and then driven into the designed depth of the seabed using methods such as pile driving, vibratory pile driving, static pressure pile driving, or drill-assisted pile driving. During the installation of the steel pipe pile core layer 3, the geometric positioning effect of the flexible hollow protective outer layer 1 ensures that the central axis of the steel pipe pile core layer 3 is basically consistent with the central axis of the flexible hollow protective outer layer 1, thereby improving the positioning accuracy of the pile foundation construction.

[0145] After the steel pipe pile core layer 3 is installed, several inclinometer tubes I4 are installed in the annular space between the flexible hollow protective outer layer 1 and the steel pipe pile core layer 3. The inclinometer tubes I4 can be evenly arranged along the circumference of the pile foundation, or they can be arranged in a focused manner according to the direction of the dominant wave current and the main stress direction. After the inclinometer tubes I4 are installed, underwater concrete is poured into the annular space by means of tremie pipe method, pumping method or underwater concrete pouring process to form the central concrete connecting layer 2.

[0146] During the underwater concrete pouring process, the concrete gradually fills the annular cavity and interlocks with the sawtooth structure 103 of the inner wall of the flexible hollow protective outer layer 1. After the concrete sets and hardens, the central concrete connecting layer 2 forms a reliable mechanical interlocking connection with the flexible hollow protective outer layer 1, while simultaneously wrapping the outside of the steel pipe pile core layer 3, so that the three layers together form an integral composite pile foundation.

[0147] During the long-term operation of offshore wind turbines, when waves and ocean currents act on the pile foundation, the trumpet-shaped flexible energy-dissipating skirt 104 can disturb and dissipate the flow field near the sea surface, allowing the local high-speed water flow around the pile to diffuse and reducing the scouring of the seabed soil by horseshoe vortices, wake vortices, and downdrafts. At the same time, the flexible hollow protective outer layer 1 can buffer the impact of external hydrodynamic forces and floating objects, the central concrete connecting layer 2 improves the overall stiffness, and the steel pipe pile core layer 3 bears the main load. The three work together to improve the foundation's resistance to scouring, corrosion, and bending deformation.

[0148] In addition, inclinometers II5 and I4 can continue to operate after construction and during operation, respectively monitoring the attitude changes of the flexible hollow protective outer layer 1 and the overall composite pile foundation. When monitoring data indicates that the pile foundation exhibits abnormal tilting, excessive bending, or a significant increase in deformation rate, timely maintenance, reinforcement, or operational adjustment measures can be taken, thereby improving the safety early warning capability and operation and maintenance management level of offshore wind turbine foundations.

Claims

1. A three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines, characterized in that: It includes a flexible hollow protective outer layer (1), a central concrete connecting layer (2), and a steel pipe pile core layer (3). The flexible hollow protective outer layer (1) is a rotating structure with a hollow interior and open top and bottom ends; the inner hole of the flexible hollow protective outer layer (1) is referred to as the receiving hole; The flexible hollow protective outer layer (1) includes a cylindrical wall (101) in the upper part and a trumpet-shaped flexible energy-dissipating skirt (104) in the lower part; the wall (101) and the flexible energy-dissipating skirt (104) are hollow inside, and together they enclose a cavity, and the end of the wall (101) away from the flexible energy-dissipating skirt (104) is provided with a number of exhaust vent holes (102) at intervals, and the end of the flexible energy-dissipating skirt (104) away from the wall (101) is provided with a number of water inlet holes (105) at intervals. The exhaust vent (102) and water inlet (105) are both connected to the cavity; When the flexible hollow protective outer layer (1) is lowered, seawater enters the cavity of the flexible hollow protective outer layer (1) through the water inlet hole (105) and exhausts air through the exhaust vent hole (102), thereby balancing the pressure; The inner wall of the wall (101) is provided with a sawtooth structure (103). The steel pipe pile core layer (3) is coaxially arranged in the receiving hole of the flexible hollow protective outer layer (1); an annular cavity is formed between the outer wall of the steel pipe pile core layer (3) and the hole wall of the flexible hollow protective outer layer (1), and the annular cavity is filled with concrete to form a central concrete connecting layer (2). Multiple inclinometer tubes I (4) are pre-embedded in the central concrete connecting layer (2); multiple inclinometer tubes II (5) are spaced apart in the cavity of the flexible hollow protective outer layer (1).

2. The three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines according to claim 1, characterized in that: The wall (101) and the flexible energy-dissipating skirt (104) are integrally formed structures.

3. The three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines according to claim 1, characterized in that: The flexible hollow protective outer layer (1) is made of modified high-density polyethylene, reinforced polymer composite material or seawater corrosion resistant flexible composite material.

4. The three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines according to claim 1, characterized in that: The sawtooth structure (103) is arranged in a circumferential, vertical or spiral direction along the wall (101).

5. The three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines according to claim 1, characterized in that: The flexible energy-dissipating skirt (104) is provided with circumferential reinforcing rings I (6), II (7), and III (8) at intervals on its outer or inner wall; the circumferential reinforcing rings I (6), II (7), and III (8) are respectively located on the upper, middle, and bottom parts of the flexible hollow protective outer layer (1).

6. The three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines according to claim 1, characterized in that: The central concrete bonding layer (2) is an underwater non-dispersible concrete layer, a chloride-resistant concrete layer, a fiber-reinforced concrete layer, or a high-durability marine concrete layer.

7. The three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines according to claim 1, characterized in that: The steel pipe pile core layer (3) includes a corrosion-resistant sealing layer (301), a high-strength steel pipe pile body (302), and an impact-resistant protective layer (303) arranged coaxially. The high-strength steel pipe pile body (302) is a hollow steel pipe pile with open upper and lower ends. The inner wall of the steel pipe pile is coated with an anti-corrosion sealing layer (301), and the outer wall is fixed with an impact-resistant protective layer (303). The impact-resistant protective layer (303) is in contact with the central concrete connection layer (2).

8. The three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines according to claim 1, characterized in that: During the installation process, the flexible hollow protective outer layer (1) requires that the end of the flexible energy dissipation skirt (104) away from the wall (101) be in contact with the target seabed surface.

9. The three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines according to claim 1, characterized in that: The inclinometer probe is fixed in the guide groove of the inclinometer tube II (5) and is used to monitor the tilting state of the flexible hollow protective outer layer (1) during the installation process. After the installation of the three-layer composite anti-erosion and anti-corrosion pile foundation for offshore wind turbines is completed and during operation, the probe of the inclinometer is lowered to the bottom of the inclinometer tube I (4) along the guide groove. After the probe reaches the bottom, the probe is pulled up and the reading is taken at a fixed point to monitor the overall bending deformation after the pile foundation is installed and during operation.

10. A construction method for a three-layer composite erosion-resistant and corrosion-resistant pile foundation for offshore wind turbines based on any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Based on the design location of the offshore wind turbine pile foundation, the flexible hollow protective outer layer (1) is hoisted or deployed to the target sea area; S2. Lower the flexible hollow protective outer layer (1). Seawater enters the flexible hollow protective outer layer (1) through the water inlet hole (105) and exhausts air through the exhaust vent hole (102), so that the flexible hollow protective outer layer (1) naturally sinks to the seabed surface under its own weight and the weight increase from the water inlet. The flexible hollow protective outer layer (1) is equipped with an inclinometer tube II (5). During the lowering and installation process, the sinking attitude and tilting state of the flexible hollow protective outer layer (1) are monitored by the inclinometer probe fixed in the guide groove of the inclinometer tube II (5). S3. The steel pipe pile core layer (3) is coaxially assembled into the inner hole of the flexible hollow protective outer layer (1), and the steel pipe pile core layer (3) is pressed into or sunk into the seabed. S4. In the annular cavity sandwiched between the steel pipe pile core layer (3) and the flexible hollow protective outer layer (1), several layers of inclinometer tubes I (4) are set at intervals. S5. Pour underwater concrete into the annular cavity to form a central concrete connection layer (2). S6. After the central concrete connecting layer (2) has solidified and hardened, a three-layer composite anti-erosion and anti-corrosion pile foundation is formed, consisting of a flexible hollow protective outer layer (1), a central concrete connecting layer (2), and a steel pipe pile core layer (3).

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