Slurry recovery and in-situ solidification device for offshore wind turbine single-pile foundation construction period

Abstract

The invention relates to the technical field of offshore wind turbine single-pile foundation construction, in particular to an offshore wind turbine single-pile foundation construction period slurry recovery and in-situ solidification device which comprises a pile foundation, an inner cylinder, an outer cylinder and a bottom frame, and the circumferential outer side area of the lower portion of the pile foundation is divided into an inner ring solidification area and an outer ring solidification area through the inner cylinder and the outer cylinder; stirring units used for stirring and mixing and grouting units used for conveying a curing agent are arranged in the inner ring curing area and the outer ring curing area, and partition stirring and partition grouting are conducted in the inner ring curing area and the outer ring curing area through the stirring units and the grouting units correspondingly. According to the method, closed recovery and in-situ solidification of the slurry in the construction period of the offshore wind turbine single-pile foundation are achieved, the annular solidified soil body with the anti-scouring and foundation enhancing functions is formed, the slurry treatment and anti-scouring construction process is simplified, and the material utilization rate and the overall stress performance of the foundation are improved.

Description

Technical Field

[0001] This invention relates to the field of offshore wind turbine monopile foundation construction technology, specifically to a mud recovery and in-situ solidification device for offshore wind turbine monopile foundation construction. Background Technology

[0002] In recent years, with the continuous expansion of offshore wind farms, large-diameter monopile foundations have become the mainstream type of wind turbine foundations in nearshore shallow to medium-deep waters due to their mature construction technology and well-defined stress performance. Offshore wind turbine monopile foundations are generally constructed using drilling, impact drilling, rotary drilling, or a combination of drilling and sinking techniques. During the pile formation process, a large amount of mud containing fine-grained soil and drill cuttings are generated. This mud typically has high water content, high fluidity, fine solid particles, and complex composition. If not controlled and discharged into the sea, it can easily increase local water turbidity and alter the properties of seabed sediments, which is detrimental to marine environmental protection. Therefore, how to ensure the efficiency of monopile construction while rationally controlling and utilizing the mud during the construction period is one of the important engineering problems that offshore wind power projects urgently need to solve.

[0003] On the other hand, during their service life, offshore wind turbine monopile foundations are often subjected to the influence of waves and tides, leading to varying degrees of localized scouring of the seabed around the piles. This creates scour pits, weakening the lateral restraint of the surrounding soil and increasing the exposed length of the pile, thus affecting the overall stability and structural safety of the pile foundation. To address pile scouring, engineering practice often employs methods such as riprap placement, laying blocks, or flexible scour blankets to create scour protection layers. Some solutions also use solidified soil or concrete to form a ring-shaped or plate-like protective structure around the piles to reduce near-bottom shear stress and improve the scour resistance of the surrounding foundation. However, existing scour protection measures are mostly implemented as "separate post-construction," relatively separate from the monopile construction process. The material sources and placement procedures are often independent of the mud treatment process during construction. The materials are often separately sourced silt or soil, with weak correlation to the mud generated during monopile construction. This fails to fully utilize the resource value of the mud generated during construction, and the mud generated during construction still requires additional collection, transportation, or separate treatment.

[0004] For mud generated during pile foundation construction, existing technologies propose using baffles, guide components, or collection troughs on the outside of the casing to guide overflowing mud into mud tanks or sedimentation ponds, followed by further treatment through processes such as pressure filtration, dewatering, and concentration to reduce the impact of mud spillage on the marine environment. These mud treatment devices focus more on mud collection and volume reduction; the treated mud cake or concentrated slurry is typically disposed of as solid waste, without being organically integrated with the formation of anti-scour structures around the piles. The treatment process is lengthy, the equipment system relatively complex, and the overall construction cost is high.

[0005] Overall, current scour-resistant soil construction systems and construction-phase mud treatment systems for monopile foundations are mostly two independent systems. Scour-resistant materials often need to be sourced and prepared separately, making it difficult to fully utilize the large amount of mud resources generated on-site during monopile construction, resulting in low material utilization. Furthermore, existing scour-resistant soil-stabilizing methods often employ centralized mixing on ships followed by pumping to the pile perimeter, which is highly dependent on sea conditions and construction windows, involves numerous process steps, and still carries the risk of leakage and diffusion of mud during transportation, hindering the achievement of closed-loop mud treatment and simplified on-site management. Therefore, a technology is needed that can collect and solidify mud on-site during monopile construction in a closed manner. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a mud recycling and in-situ solidification device for the construction of offshore wind turbine monopile foundations. This device aims to simultaneously achieve closed collection and in-situ solidification of mud during monopile construction. This method integrates the mud disposal process with the construction of the pile perimeter scour-resistant structure, effectively reducing environmental pollution and significantly improving construction and material utilization efficiency. It also helps enhance the overall mechanical properties of the pile perimeter foundation and the foundation system. This invention solves the problems of low material utilization, significant dependence on sea conditions and construction windows, numerous process steps, and the risk of mud leakage and diffusion during transportation in existing technologies.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A device for mud recycling and in-situ solidification during the construction period of a single pile foundation for an offshore wind turbine includes a pile foundation vertically installed on the seabed and a collection cylinder surrounding the lower circumferential outer area of ​​the pile foundation. The collection cylinder encloses the lower circumferential outer area of ​​the pile foundation to form a solidification zone. During the construction period, the mud is concentrated and deposited in the solidification zone. The solidification zone is equipped with a mixing unit for stirring and mixing and a grouting unit for conveying the solidifying agent. There are multiple mixing units and grouting units, which are spaced apart around the circumference of the pile foundation. The mixing unit stirs and mixes the original soil, construction mud and solidifying agent in the solidification zone to form in-situ solidified soil.

[0008] Furthermore, the collection cylinder includes an inner cylinder disposed on the lower circumferential outer side of the pile foundation, an outer cylinder disposed on the circumferential outer side of the inner cylinder, and a base frame connected to the bottom of the inner cylinder and the outer cylinder. The base frame abuts against the seabed. The solidification zone is divided into an inner solidification zone and an outer solidification zone by the inner cylinder and the outer cylinder. Both the inner solidification zone and the outer solidification zone are equipped with a mixing unit and a grouting unit. The mixing unit and the grouting unit respectively perform zoned mixing and zoned grouting in the inner solidification zone and the outer solidification zone.

[0009] Furthermore, the upper part of the inner cylinder and the outer cylinder are connected to a top beam, and the stirring unit includes a stirring shaft rotatably connected to the top beam. The stirring shaft extends vertically to above the near-seabed, and the lower part of the stirring shaft is provided with stirring blades. The stirring unit also includes a drive mechanism disposed on the top beam for driving the stirring shaft to rotate.

[0010] Furthermore, the base frame is provided with a limiting sleeve for limiting the rotational swing angle of the stirring shaft.

[0011] Furthermore, the grouting unit includes a grouting nozzle disposed above the near-seabed. The grouting nozzle is connected to the grout storage source through a delivery pipe. The grouting nozzle in the inner solidification zone is disposed on the inner cylinder, and the grouting nozzle in the outer solidification zone is disposed on the outer cylinder.

[0012] Furthermore, both the inner and outer cylinders are provided with exhaust ports at their upper parts. The exhaust ports are connected to the water pumping assembly through exhaust pipes, and a filter screen is provided inside the exhaust ports.

[0013] Furthermore, there are multiple drainage ports, which are spaced apart around the circumference of the pile foundation.

[0014] Furthermore, shearing teeth are provided on the contact surface between the base frame and the seabed.

[0015] Furthermore, a negative pressure chamber is provided in the circumferential direction of the outer cylinder, and the negative pressure chamber is connected to a suction unit for suctioning seawater in the area covered by the negative pressure chamber.

[0016] Furthermore, the lower part of the pile foundation has a groove in the circumferential direction.

[0017] Compared with existing technologies, this invention achieves closed-loop recycling and in-situ solidification of mud during the construction of offshore wind turbine monopile foundations, forming a ring-shaped solidified soil with both erosion protection and foundation reinforcement functions. This simplifies the mud treatment and erosion protection construction process, improves material utilization and the overall load-bearing performance of the foundation. Specifically: This invention involves installing an annular mud collection cylinder on the lower circumferential outer side of the monopile foundation for offshore wind turbines. This confines the mud and drill cuttings generated during drilling or sinking to a specific area around the pile in an underwater saturated environment. Simultaneously, an inner and outer cylinder divide the solidification zone into an inner and outer solidification zone. Each solidification zone is equipped with a mixing and grouting unit, allowing the mud within the solidification zone to undergo in-situ chemical solidification under underwater saturation without drainage. This ultimately forms an annular solidified soil mass with different functional zones around the lower perimeter of the pile foundation. Furthermore, by creating circumferential grooves on the pile foundation, a mechanical interlocking connection is formed between the solidified inner high-strength soil mass and the pile body. This incorporates the solidified soil mass into the monopile foundation system from a stress mechanism perspective, effectively transferring horizontal loads and bending moments. The annular solidified soil mass not only acts as an anti-erosion agent but also actively participates in the foundation's stress, significantly improving the lateral stiffness and overall stability of the foundation around the pile.

[0018] From a holistic system perspective, this invention couples and integrates three previously independent processes—environmentally friendly disposal of construction mud during offshore monopile construction, construction of anti-scour structures around the piles, and foundation reinforcement—within the same space and time window. This forms a continuous technical chain of "mud deposition—underwater in-situ solidification—solidified body participating in load-bearing," achieving an in-situ integrated effect that is difficult to achieve in existing technologies. Construction mud is no longer treated as waste requiring external transportation or disposal. Instead, it is transformed into raw materials for scour prevention and foundation reinforcement through a ring-shaped collection cylinder and solidifying agent supply system, achieving closed-loop utilization of mud resources, reducing dependence on external soil sources or gravel materials, and avoiding large-scale mud diffusion and multiple transfers. Simultaneously, the solidification process takes place entirely in an underwater saturated environment, eliminating the need for large cofferdams or pumping to create a dry working surface. By appropriately controlling the mud solids content and solidifying agent dosage within the collection cylinder, solidified soil meeting design strength and scour resistance requirements can be obtained. This makes the invention highly adaptable to construction in deep waters with significant tidal ranges. Because the ring-shaped solidified soil is arranged coaxially with the pile foundation in terms of location, and functionally it is interlocked with the pile body through the inner high-strength zone and resisted by water flow through the outer thickened zone, a composite foundation system of "pile foundation - solidified ring - original soil" working together is finally formed. Compared with the scheme that simply relies on the soil on the pile side or external riprap protection, it has better comprehensive performance in terms of overall structural stiffness, deformation control and controllability of scour development. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a top-view structural diagram of the present invention.

[0020] The attached diagram is described below: 1. Pile foundation; 11. Groove; 21. Inner cylinder; 22. Outer cylinder; 23. Base frame; 232. Limiting sleeve; 24. Top beam; 31. Mixing shaft; 32. Mixing blades; 33. Mixing motor; 41. Grouting nozzle; 42. Conveying pipe; 43. Grouting source; 51. Exhaust port; 52. Filter screen; 61. Negative pressure chamber; 62. Suction unit. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0022] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0023] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0025] For easier understanding, please refer to Figure 1 and Figure 2This embodiment provides a mud recovery and in-situ solidification device for offshore wind turbine monopile foundation construction. The device is entirely installed in an underwater saturated environment, eliminating the need to pump out the seawater. It achieves concentrated sedimentation of mud during construction through structural constraints, followed by in-situ mixing and solidification underwater to form a ring-shaped solidified soil mass. The device includes a pile foundation 1 vertically installed on the seabed and a collection cylinder. The collection cylinder includes an inner annular cylinder 21 located circumferentially outside the lower part of the pile foundation 1, and an outer annular cylinder 22 located circumferentially outside the inner cylinder 21. A perforated base frame 23 is fixedly connected to the bottom of the inner and outer cylinders 21 and is fixedly installed on the seabed. The inner and outer cylinders 21 and 22 are connected by the base frame 23 to form the collection cylinder. Preferably, the collection cylinder segments are prefabricated using corrosion-resistant steel plates with a thickness of 10 to 30 mm or reinforced concrete with good impermeability. Under its own weight and external water pressure, the collection cylinder adheres to the seabed surface, forming a relatively closed annular mud collection space (solidification zone). This confines most of the mud and drill cuttings generated during the construction of pile foundation 1 within the collection cylinder, while seawater slowly seeps in and out through soil pores and the pores of the base frame 23. The circumferential outer area of ​​the lower part of pile foundation 1 is divided into an inner solidification zone and an outer solidification zone by the inner cylinder 21 and the outer cylinder 22. Both the inner and outer solidification zones are equipped with mixing and grouting units, which perform zoned mixing and grouting in the inner and outer solidification zones respectively. Specifically, a high-dosage curing agent slurry is delivered to the inner solidification zone through the grouting unit within the inner solidification zone. This slurry, along with most of the mud and drill cuttings generated during the construction of pile foundation 1, is then mixed with the high-dosage curing agent slurry to form a high-strength mud-curing agent mixture that wraps around the lower circumferential outer side of pile foundation 1. Similarly, a low-dosage curing agent slurry is delivered to the outer solidification zone through the grouting unit within the outer solidification zone. This slurry, along with a small portion of the mud and drill cuttings generated during the construction of pile foundation 1, is then mixed with the low-dosage curing agent slurry to form a solidification layer that wraps around the lower circumferential outer side of the inner cylinder 21, primarily for erosion prevention and energy dissipation. More specifically, the curing agent can be selected from ordinary silicate cement with mineral admixtures and additives, depending on the type of seabed soil, design strength and durability requirements. Alternatively, a special curing agent system suitable for marine environments can be selected. It is not limited to the specific material ratios mentioned above. As long as the requirements for mud curing and marine environment durability are met, it can be used.

[0026] The inner cylinder 21 and the outer cylinder 22 are connected to a top beam 24, which can be annular, composed of multiple radial steel beams, or a truss structure. The mixing unit includes a mixing shaft 31 and a drive mechanism. The upper end of the mixing shaft 31 is rotatably connected to the top beam 24, and the lower end of the mixing shaft 31 extends vertically downwards to above the seabed. Near the lower end of the mixing shaft 31, there are mixing blades 32, which can be paddle-shaped, folded-plate-shaped, or spiral-shaped, preferably turbine-type. The arrangement height of the mixing blades 32 is preferably close to the seabed elevation, so that the effective range of the mixing blades 32 covers the mud layer near the base frame 23. The drive mechanism is fixedly installed on the top beam 24 and drives the mixing shaft 31 to rotate. Preferably, the drive mechanism for the mixing blades 32 is a mixing motor 33. Specifically, the top beam 24 has vertical mounting holes, and sealed bearings are installed in the mounting holes. The upper end of the stirring shaft 31 is rotatably connected to the top beam 24 through the sealed bearings. The output shaft of the stirring motor 33 is connected to the upper end of the stirring shaft 31 through a coupling. The drive mechanism and related transmission components are all waterproof and sealed to ensure normal operation in seawater. There are multiple stirring units in both the inner and outer solidification zones, which are spaced apart from each other around the circumference of the pile foundation 1 to ensure that the mixing action covers the entire solidification zone and improves the solidification effect. Multiple limiting sleeves 232 corresponding to the stirring shaft 31 are fixedly installed on the base frame 23. The stirring shaft 31 and the limiting sleeves 232 are coaxially arranged, with the bottom of the stirring shaft 31 extending into the limiting sleeve 232. There is a certain gap between the stirring shaft 31 and the limiting sleeve 232, that is, the limiting sleeve 232 does not form a rigid connection with the stirring shaft 31. The limiting sleeve 232 restricts the rotation and swing angle of the stirring shaft 31, preventing the stirring shaft 31 from swinging too much during operation. Furthermore, the top beam 24 has an outwardly protruding flange (not shown in the figure) on the connection surface with the inner cylinder 21 and the outer cylinder 22, and the inner cylinder 21 and the outer cylinder 22 respectively have inwardly recessed pits (not shown in the figure) on the connection surface with the top beam 24. During the installation of the top beam 24 from top to bottom, the flange and the pit are matched to achieve the alignment connection, ensuring that the bottom of the stirring shaft 31 extends into the limiting sleeve 232.

[0027] The grouting unit includes a grouting nozzle 41, a delivery pipe 42, and a grout storage source 43. The grouting nozzle 41 is fixedly installed above the seabed of the inner cylinder 21 and outer cylinder 22 (near the installation position of the stirring blades 32). The grouting nozzle 41 is connected to the grout storage source 43 through the delivery pipe 42. Specifically, the grout storage source 43 is fixedly installed on the construction vessel or work platform. The grout storage source 43 includes a storage tank and a metering pump. The inner and outer curing zones are two relatively independent grout pipeline delivery systems. The storage tank corresponding to the inner curing zone contains grout with a high dosage of curing agent, while the storage tank corresponding to the outer curing zone contains grout with a low dosage of curing agent or other suitable binding materials. The valve opening and pump flow rate of the two pipelines are adjusted by a controller to achieve independent control of the curing agent dosage in the inner and outer curing zones. A delivery pump is installed on the delivery pipe 42 to provide delivery power. The grouting nozzles 41 and corresponding delivery pipes 42 in the inner ring curing zone are fixedly installed on the inner cylinder 21, with the openings of the grouting nozzles 41 facing inwards. Similarly, the grouting nozzles 41 and corresponding delivery pipes 42 in the outer ring curing zone are fixedly installed on the outer cylinder 22, with the openings of the grouting nozzles 41 facing inwards. Multiple grouting nozzles 41 are present in both the inner and outer ring curing zones, and they are spaced apart around the circumference of the pile foundation 1 to ensure that the curing agent delivery range covers the entire curing zone, thus improving the curing effect.

[0028] The bottom of the base frame 23 (i.e., the surface in contact with the seabed) is equipped with shearing teeth. Specifically, the shearing teeth are made of steel of the same or similar material as the collection cylinder or pile foundation 1 to ensure welding performance and durability. During the hoisting and lowering of the collection cylinder, the shearing teeth penetrate into the surface soil of the seabed to a certain depth, improving the overall anti-slip ability of the collection cylinder and reducing lateral loss of mud. Furthermore, rubber strips can be attached to the bottom and side edges of the shearing teeth. The rubber strips are made of seawater-resistant rubber material, which increases the friction between the base frame 23 of the collection cylinder and the surface soil of the seabed, further improving the stability of the collection cylinder installation and deployment. An annular negative pressure chamber 61 is fixedly provided on the circumference of the outer cylinder 22. A suction unit 62 is connected to the negative pressure chamber 61. The suction unit 62 is used to suction seawater from the area covered by the negative pressure chamber 61. Specifically, the suction unit 62 includes a suction pipeline and a suction pump. A sand-proof net is installed inside the suction pipeline to prevent mud and sand particles from entering the suction pipeline and to protect the pumping equipment. The suction pipeline can be fixedly installed on the outer wall of the outer cylinder 22, and the pump can be installed on a platform on the water. Preferably, the negative pressure chamber 61 is a flexible structure made of wear-resistant rubber, polyurethane, or composite fabric to adapt to seabed undulations and improve sealing performance. After the entire device is lowered to the seabed and settled, the lower part of the negative pressure chamber 61 initially adheres to the seabed surface under its own weight and external water pressure, forming an initial sealing boundary. The pump is then activated to suction seawater from inside the negative pressure chamber 61, reducing the pressure within it. This, combined with the external water pressure, further presses the sides of the negative pressure chamber 61 tightly against the seabed surface. Simultaneously, during suction, the surface soil in the area covered by the negative pressure chamber 61 contracts and accumulates, eliminating the bottom micro-cracks and achieving a lock-edge seal. In real-world conditions, it is difficult to achieve a long-term absolute seal between the inner and outer zones near the seabed. Uneven seabed conditions, device settlement, and the periodic pressure differences and eddies generated by grouting and mixing can cause the bottom micro-cracks to become the primary cross-zone flow channels, especially prone to backflow and flooding during pump and mixing stoppages or pressure reversals. The aforementioned structure prevents mud from escaping and diffusing at the bottom edge of the cylinder during construction, improving mud sealing and collection efficiency, and providing better adaptability to uneven seabeds and particle accumulation. Furthermore, the inner ring usually undertakes key curing control. If the material in the inner ring leaks outward, it will cause the outer ring to become locally too hard, unevenly cured and waste materials, and destroy the zonal curing target. Therefore, an annular negative pressure chamber 61 can also be fixed in the circumferential direction of the inner cylinder 21 to improve the stability and controllability of zonal curing.

[0029] A ring-shaped groove 11 is formed in the lower part of the pile foundation 1 in the circumferential direction. After solidification, the solidified soil is filled into the groove 11 in the lower part of the pile foundation 1 to form a mechanical interlock. Through the above structure, the ring-shaped solidified soil not only shares the load with the original seabed soil, but also forms a good interlocking connection with the pile foundation 1 itself through the ring-shaped groove 11, transferring some of the shear force and bending moment from the superstructure to the ring-shaped solidified soil, thereby improving the overall stiffness of the foundation around the pile and the stability under scour conditions. Furthermore, there can be multiple grooves 11, which are spaced apart from each other in the axial direction of the pile foundation 1.

[0030] Both the inner cylinder 21 and the outer cylinder 22 have exhaust ports 51 at their upper parts. The exhaust ports 51 are connected to the pumping components located on the construction vessel or work platform through exhaust pipes. There are multiple exhaust ports 51, which are arranged at intervals around the circumference of the pile foundation 1. A filter screen 52 is fixedly installed inside the exhaust port 51. The filter screen 52 is made of rubber, stainless steel or engineering plastic material that is resistant to seawater corrosion. The pumping pipeline system allows for adjustments to the mud moisture content or reduction of the mud surface height within the collection cylinder under certain working conditions. Specifically, after the installation of pile 1 and the collection cylinder, the mud inside the collection cylinder will settle under static conditions, forming a lower layer of high-solids mud and an upper layer of relatively clean water. At this point, the pumping unit can be activated as needed to extract some of the water from the upper part of the collection cylinder through the pumping pipeline at the pumping port 51. Large particles of mud and flocs are then trapped by the filter screen 52, thereby appropriately increasing the solids content of the mud in the collection cylinder without changing the underwater saturated environment, and reserving some space for the subsequent injection and mixing of the solidifying agent. Since the collection cylinder is entirely underwater and there is still slow seepage between it and the outside seawater, the above-mentioned pumping action is only an optional control measure to reduce excessive dilution and optimize construction conditions, and is not necessary for the solidification reaction. The entire solidification process is always completed in an underwater saturated state.

[0031] Furthermore, this embodiment achieves adaptive adjustment of the curing process and long-term autonomous monitoring after curing through an integrated intelligent control system. The intelligent control system includes a controller, a torque sensor installed on the output shaft of the mixing motor 33, and a temperature sensor installed at the lower part of the mixing shaft 31. During the construction of the pile foundation 1, the torque sensor and temperature sensor monitor the mixing torque and the exothermic reaction of the curing reaction in real time. When the torque increase rate and temperature change rate are detected to be relatively flat and reach a preset threshold, it is determined that the mud has reached the initial setting state. Then, the controller stops the mixing and grouting actions, thereby improving the curing uniformity and construction reliability without the need for complex tests. Furthermore, strain gauges or fiber optic sensors are pre-embedded in the formed annular solidified soil, and water level or pressure sensors are set on the periphery to monitor the stress state of the solidified soil and the development of surrounding scour during the long-term operation of the offshore wind turbine. When the data is abnormal and exceeds the safety threshold, an early warning will be issued to the controller, prompting maintenance measures to be taken. This embodiment organically combines mud treatment during construction, construction of the pile perimeter anti-scour structure, and monitoring and early warning during operation without changing the basic device structure, forming a closed-loop protection system of "construction-curing-monitoring".

[0032] Implementation steps of the present invention: Step S1: Prefabrication of pile foundation 1 and collection cylinder.

[0033] Based on parameters such as the pile diameter of the monopile foundation, seabed strata conditions, design scour protection range, and water depth, the dimensions (including inner diameter, outer diameter, and height) of the inner cylinder 21, outer cylinder 22, and base frame 23 of the annular mud collection cylinder are determined. The prefabrication and connection of components such as the collection cylinder segments, top beam 24, mixing unit, and grouting unit are completed, and anti-corrosion and waterproofing processes are applied.

[0034] Step S2: Installation of pile foundation 1 and collection cylinder.

[0035] Using lifting equipment, pile 1 is hoisted and lowered to the design position, and pile 1 is initially installed and fixed on the seabed. Then, using lifting equipment, the collection cylinder (including the components installed on the collection cylinder) is hoisted and lowered to the design position, so that the collection cylinder is basically coaxially fitted around pile 1, and gradually lowered until the shearing teeth are inserted into the surface soil of the seabed, so as to achieve the initial embedding and sealing of the collection cylinder and the seabed.

[0036] Step S3: Install top beam 24.

[0037] Using lifting equipment, the top beam 24 (including components installed on the top beam 24) is hoisted and lowered to the designed position. Through the alignment connection of the flange and the recess, the top beam 24 is installed above the collection cylinder, while the bottom of the stirring shaft 31 is accurately inserted into the limiting sleeve 232. The conveying pipe 42 is led down from the hollow part of the top beam 24 to connect with the corresponding inner ring grouting nozzle 41 and outer ring grouting nozzle 41.

[0038] Step S4: Single pile construction and concentrated mud deposition and collection.

[0039] During the single-pile construction process, the mud generated is collected in a collection cylinder.

[0040] Step S5 (optional): Settle the mud in the cylinder and pump out the water from the top.

[0041] Before solidification, the mud can be allowed to settle and settle. If necessary, the upper water body can be pumped out to adjust the mud concentration.

[0042] Step S6: First stage - Inner ring high-volume grouting and mixing.

[0043] Only the grout pipeline delivery system of the inner ring curing zone is turned on, and high-dosage curing agent grout is injected into the mud area near the lower part of the pile foundation 1 through the grouting nozzle 41 of the inner ring. At the same time, the mixing unit of the inner ring curing zone is started to make the mud and high-dosage curing agent in the inner ring curing zone fully mixed. During this process, the mixing unit of the outer ring curing zone can be turned off or run at a lower speed to avoid or reduce the diffusion of curing agent outward.

[0044] Step S7: Second stage - low-dosage grouting and mixing in the outer ring.

[0045] The slurry pipeline delivery system of the inner ring curing zone is closed, and the slurry pipeline delivery system of the outer ring curing zone is opened. A relatively low amount of curing agent slurry is injected into the mud area near the lower part of the inner cylinder 21 through the grouting nozzle 41 of the outer ring. At the same time, the mixing unit of the outer ring curing zone is started to fully mix the mud in the outer ring curing zone with the high amount of curing agent.

[0046] Step S8: Dismantle the mixing and grouting equipment.

[0047] After the grouting and mixing process is completed, all grout pipeline delivery systems are shut down, all mixing units are stopped, and the top beam 24 (including the components installed on the top beam 24) is lifted as a whole using lifting equipment, so that it is pulled out of the mixed slurry after the mixing process is completed.

[0048] Step S9: Underwater curing and solidification and ring-shaped solidification of soil.

[0049] The entire solidification process takes place in an underwater saturated environment. The mixed mud and seawater together serve as the water source in the solidification system. The solidifying agent reacts with the fine particles and water in the mud through hydration, hydrolysis and gelation. The resulting hydration products encapsulate the mud particles and form a spatial skeleton, gradually transforming the originally high-water-content mud into a solidified soil with certain compressive strength and erosion resistance.

[0050] Step S10: Form a composite foundation system.

[0051] The ring-shaped solidified soil on the outer side, the pile foundation 1 on the inner side, and the original seabed soil below together form a composite foundation system, realizing the integrated effect of underwater centralized treatment and resource utilization of mud during construction, as well as pile perimeter scour prevention and foundation reinforcement.

[0052] Although the present invention has been described using the above preferred embodiments, it is not intended to limit the scope of protection of the present invention. Any changes and modifications made by those skilled in the art to the above embodiments without departing from the spirit and scope of the present invention shall still fall within the scope of protection of the present invention.

Claims

1. A device for mud recycling and in-situ solidification during the construction period of a single pile foundation for an offshore wind turbine, characterized in that, The system includes a pile foundation (1) installed vertically on the seabed and a collection cylinder wrapped around the lower circumferential outer side of the pile foundation (1). The collection cylinder encloses the lower circumferential outer area of ​​the pile foundation (1) to form a solidification zone. During construction, the mud is concentrated and deposited in the solidification zone. The solidification zone is equipped with a mixing unit for mixing and a grouting unit for conveying the curing agent. There are multiple mixing units and grouting units, which are spaced apart around the pile foundation (1). The mixing unit mixes the original soil, construction mud and curing agent in the solidification zone to form in-situ solidified soil.

2. The mud recycling and in-situ solidification device for offshore wind turbine monopile foundation construction period according to claim 1, characterized in that, The collection cylinder includes an inner cylinder (21) located on the lower circumferential outer side of the pile foundation (1), an outer cylinder (22) located on the circumferential outer side of the inner cylinder (21), and a base frame (23) connected to the bottom of the inner cylinder (21) and the outer cylinder (22). The base frame (23) abuts against the seabed. The solidification zone is divided into an inner solidification zone and an outer solidification zone by the inner cylinder (21) and the outer cylinder (22). Both the inner solidification zone and the outer solidification zone are equipped with a mixing unit and a grouting unit. The mixing unit and the grouting unit are used to perform zoned mixing and zoned grouting in the inner solidification zone and the outer solidification zone, respectively.

3. The mud recycling and in-situ solidification device for offshore wind turbine monopile foundation construction period according to claim 2, characterized in that, The upper part of the inner cylinder (21) and the outer cylinder (22) is connected to a top beam (24). The stirring unit includes a stirring shaft (31) rotatably connected to the top beam (24). The stirring shaft (31) extends vertically to above the near seabed. The lower part of the stirring shaft (31) is provided with stirring blades (32). The stirring unit also includes a drive mechanism set on the top beam (24) for driving the stirring shaft (31) to rotate.

4. The mud recycling and in-situ solidification device for offshore wind turbine monopile foundation construction period according to claim 3, characterized in that, The base frame (23) is provided with a limiting sleeve (232) for limiting the rotational swing angle of the stirring shaft (31).

5. The mud recycling and in-situ solidification device for offshore wind turbine monopile foundation construction period according to claim 2, characterized in that, The grouting unit includes a grouting nozzle (41) disposed above the near-seabed. The grouting nozzle (41) is connected to the grout storage source (43) through a delivery pipe (42). The grouting nozzle (41) of the inner ring solidification zone is disposed on the inner cylinder (21), and the grouting nozzle (41) of the outer ring solidification zone is disposed on the outer cylinder (22).

6. The mud recycling and in-situ solidification device for offshore wind turbine monopile foundation construction period according to claim 2, characterized in that, Both the inner cylinder (21) and the outer cylinder (22) are provided with a drain port (51) at the top. The drain port (51) is connected to the water pumping assembly through a drain pipe. A filter screen (52) is provided inside the drain port (51).

7. The mud recycling and in-situ solidification device for offshore wind turbine monopile foundation construction period according to claim 6, characterized in that, There are multiple drainage ports (51), which are spaced apart around the pile foundation (1).

8. The mud recycling and in-situ solidification device for offshore wind turbine monopile foundation construction period according to claim 2, characterized in that, The base frame (23) has shearing teeth on the contact surface with the seabed.

9. The mud recycling and in-situ solidification device for offshore wind turbine monopile foundation construction period according to claim 2 or 8, characterized in that, The outer cylinder (22) is provided with a negative pressure chamber (61) in the circumferential direction, and the negative pressure chamber (61) is connected to a suction unit (62) for suctioning seawater in the area covered by the negative pressure chamber (61).

10. The device for mud recycling and in-situ solidification during the construction period of a single pile foundation (1) for offshore wind turbines according to claim 1, characterized in that, The lower part of the pile foundation (1) has a groove (11) in the circumferential direction.

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