Offshore wind power pile foundation scouring protection construction method and device based on energy dissipation net

Abstract

The invention discloses an offshore wind power pile foundation scouring protection construction method and device based on an energy dissipation net. The offshore wind power pile foundation scouring protection construction device comprises an offshore wind power pile foundation, solidified soil arranged at the bottom of the offshore wind power pile foundation and a support arranged in the middle of the offshore wind power pile foundation. A plurality of upper fixers are arranged on the support with the pile foundation as the circle center in a circumferential array mode, and a plurality of lower fixers are arranged on the solidified soil with the pile foundation as the circle center in a circumferential array mode. An energy dissipation net is connected between the upper fixer and the lower fixer; the energy dissipation net comprises a surface energy dissipation net body, an inner energy dissipation net body and a viscous damper connected with the surface energy dissipation net body and the inner energy dissipation net body. Through the flexible structure of the double-layer energy dissipation net, the water flow speed is effectively reduced, the scouring depth is reduced, and the structural adaptability and stability are enhanced; and meanwhile, the seabed around the pile foundation is further consolidated through the synergistic effect of the solidified soil and the energy dissipation net, the overall protection effect is improved, the service life of the system is prolonged, and the maintenance cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of underwater structures, and particularly to the technical field of preventing soil or water erosion. Specifically, it is a construction method and device for scour protection of offshore wind turbine foundations based on an energy dissipation net. Background Art

[0002] As an important part of clean energy, offshore wind power has developed rapidly globally. However, offshore wind power facilities face many challenges during construction, and one of the important challenges is the scour problem of the foundations; scour refers to the phenomenon that the substances on the seabed surface are eroded under the action of water flow or waves, resulting in the loss of soil around the wind turbine foundations.

[0003] As a key structure for supporting wind power equipment, the stability of offshore wind turbine foundations is directly related to the safe operation of the entire wind farm. However, under the combined action of waves and water flow, the seabed soil near the foundations is prone to scour, resulting in a decrease in the penetration depth of the foundations and an increase in the cantilever length, thereby reducing the bearing capacity and stability of the foundations; once the foundations become unstable, it may trigger serious accidents such as the overturning of wind turbines, causing huge economic losses and safety hazards. Therefore, it is very necessary to carry out scour protection for offshore wind turbine foundations.

[0004] An energy dissipation net is a technical means for reducing the energy of water flow and preventing or slowing down seabed scour; it is usually made of high-strength materials and designed into a specific shape and structure, which can effectively disperse the water flow and reduce its erosive force on the seabed; by laying an energy dissipation net around the foundation, a protective barrier can be formed to prevent the water flow from directly impacting the seabed, thereby achieving the purpose of protecting the foundation from scour.

[0005] Therefore, it is necessary to improve the existing scour protection method and device for offshore wind turbine foundations based on an energy dissipation net to solve the above problems. Summary of the Invention

[0006] The present invention overcomes the deficiencies of the prior art and provides a construction method and device for scour protection of offshore wind turbine foundations based on an energy dissipation net, aiming to solve the problems of poor scour protection effect and high maintenance cost of offshore wind turbine foundations in the prior art.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a scour protection device for offshore wind turbine foundations based on an energy dissipation net, comprising: an offshore wind turbine foundation,

[0008] solidified soil provided at the bottom of the offshore wind turbine foundation, and a bracket provided in the middle of the offshore wind turbine foundation; a plurality of upper fixators are circumferentially arranged around the foundation as the center on the bracket, and a plurality of lower fixators are circumferentially arranged around the foundation as the center on the solidified soil; an energy dissipation net is connected between the upper fixator and the lower fixator;

[0009] The energy dissipation net includes: a surface energy dissipation net, an inner energy dissipation net, and viscous dampers connecting the surface energy dissipation net and the inner energy dissipation net; the aperture of the surface energy dissipation net is 40 - 80 mm, and the aperture of the inner energy dissipation net is 20 - 40 mm; the material of the surface energy dissipation net is corrosion-resistant; the material of the inner energy dissipation net is wear-resistant and impact-resistant.

[0010] In a preferred embodiment of the present invention, the main material used for the solidified soil is natural silt, mixed with an inorganic composite solidifying material and an additive. The inorganic composite solidifying material includes: cement, lime, fly ash, and gypsum.

[0011] Among them, the mass ratio of the natural silt, the cement, the lime, the fly ash, the gypsum, and the additive is: 1: 0.05 - 0.15: 0.01 - 0.05: 0.1 - 0.3: 0.01 - 0.02: 0.05 - 0.01.

[0012] In a preferred embodiment of the present invention, the material of the surface energy dissipation net is one or a mixture of polypropylene, polyester fiber, and nylon.

[0013] The material of the inner energy dissipation net is one or a mixture of high-density polyethylene and glass fiber reinforced plastic.

[0014] In a preferred embodiment of the present invention, the angle range between the inner energy dissipation net and the surface energy dissipation net is between 10° and 30°.

[0015] In a preferred embodiment of the present invention, the distance h between the inner energy dissipation net and the surface energy dissipation net is 0.5 - 1 m.

[0016] In a preferred embodiment of the present invention, the viscous dampers are evenly distributed in the energy dissipation net; the density change of the viscous dampers from top to bottom is: from large density to small density and then to large density; the density of the viscous dampers at the top of the energy dissipation net is 10 - 12 per m 2 , and it decreases by 1 per m every 20 - 30 cm downward 2 , until it reaches 5 - 6 per m 2 , and then it increases by 1 per m every 20 - 30 cm downward 2 , until it reaches 10 - 12 per m 2 .

[0017] The present invention provides a construction method for scour protection of offshore wind power pile foundations based on an energy dissipation net, including:

[0018] S1. Collect the geological conditions of the seabed where the offshore wind power pile foundation is located, and simulate the scour of the underwater offshore wind power pile foundation.

[0019] S2. According to the simulation results, corresponding solidified soil reinforcement treatment is carried out around the base of the offshore wind power pile;

[0020] S3. According to the simulation results, design and prepare an energy dissipation net, and simulate the water flow scouring under the protection of the energy dissipation net;

[0021] S4. According to the design requirements, transport the prepared energy dissipation net to the location of the offshore wind power pile foundation for installation;

[0022] S5. Regularly check the energy dissipation net and the solidified soil, and real-time detect the water flow and sediment conditions around the offshore wind power pile foundation.

[0023] In a preferred embodiment of the present invention, in step S1, a hydrodynamic model is established to simulate the scouring of the seabed where the offshore wind power pile foundation is located by water flow;

[0024] Mesh generation is carried out on the flow field around the pile foundation through CFD;

[0025] Set the initial water depth and flow velocity field according to the collected address condition data;

[0026] Describe the turbulent characteristics of the water flow through the k-ε turbulence model;

[0027] k equation: Where, ui is the component of the water flow velocity in the i-th direction, k is the turbulent kinetic energy, xi, xj are the components of the spatial coordinates in the i-th and j-th directions, ν is the molecular viscosity, νt is the turbulent viscosity, σk is the Prandtl number of the turbulent kinetic energy, pk is the generation term of the turbulent kinetic energy, ρ is the fluid density, and τ is the turbulent kinetic energy dissipation rate;

[0028] ε equation: Where, στ is the Prandtl number of the turbulent kinetic energy dissipation rate, C 1τ , C 2τ are model constants;

[0029] The suspended sediment concentration of the suspended load carried by the sediment is Where, qs is the suspended sediment flux per unit width, u* is the friction velocity, and H is the water depth;

[0030] The local scouring depth around the offshore wind power pile foundation is Where, K 1 is the soil property coefficient, g is the acceleration due to gravity, s is the ratio of the sediment density to the water density, and dp is the sediment particle diameter.

[0031] In a preferred embodiment of the present invention, in step S3, the simulation of the water flow scouring under the protection of the energy dissipation net is carried out based on the hydrodynamic model in step S1, and the influence of the energy dissipation net is increased;

[0032] The calculation of the influence of the energy dissipation net is as follows:

[0033] The deceleration of water flow velocity by the energy dissipation net Among them, v in is the water flow velocity flowing into the energy dissipation net, vout is the water flow velocity flowing out of the energy dissipation net, κ is the deceleration coefficient of the energy dissipation net, and L x is the path length of the water flow passing through the energy dissipation net;

[0034] Calculating the deceleration coefficient of the energy dissipation net requires considering the characteristics of the double-layer reticulated shell structure, including the relative position and angle between the two layers of the net, and the influence of different porosity; the calculated deceleration coefficient is Among them, Cd 1 , Cd 2 are the resistance coefficients of the surface layer and the inner layer of the energy dissipation net, A 1 , A 2 are the effective areas of the surface layer and the inner layer of the energy dissipation net, V 1 , V 2 are the volumes of the surface layer and the inner layer of the energy dissipation net, is the interaction deceleration coefficient between the two layers of the net, and θ is the included angle between the normal directions of the two layers of the net at the contact point;

[0035] The influence of the energy dissipation net on the water flow pressure is Among them, p out is the water flow pressure flowing into the energy dissipation net, p in is the water flow pressure flowing out of the energy dissipation net, Δp is the pressure drop caused by the energy dissipation net, and ρ w is the density of seawater;

[0036] The influence of the energy dissipation net on sediment deposition is Among them, C out , C in are the sediment concentrations flowing into and out of the energy dissipation net.

[0037] In a preferred embodiment of the present invention, the truncation calculation of the energy dissipation net: Let the spherical shell radius of the inner layer of the energy dissipation net be R 1 , among which, R 1 ≥4r, where r is the pile foundation radius; set the truncation height h c as the height H subtracted from the center of the sphere by the support plus an additional safety margin d safe , the truncation height

[0038]

[0039] The present invention solves the defects existing in the background technology, and the present invention has the following beneficial effects:

[0040] (1) The present invention provides a construction method and device for scour protection of offshore wind power pile foundations based on an energy dissipation net. The device includes an offshore wind power pile foundation, solidified soil provided at the bottom of the pile foundation, a bracket in the middle, and a double-layer energy dissipation net connected to the bracket and the solidified soil. The energy dissipation net consists of a surface energy dissipation net, an inner energy dissipation net, and a viscous damper. By collecting seabed geological conditions, establishing a hydrodynamic model to simulate the scour situation, performing solidified soil reinforcement treatment, designing and preparing the energy dissipation net, and finally installing and regularly monitoring and maintaining it. The present invention effectively reduces the water flow velocity through the flexible structure of the double-layer energy dissipation net, reduces the scour depth, enhances the structural adaptability and stability. At the same time, the synergistic effect of the solidified soil and the energy dissipation net further consolidates the seabed around the pile foundation, improves the overall protection effect, extends the service life of the system, and reduces the maintenance cost.

[0041] (2) By simulating the water flow scour situation, the present invention accurately designs the solidified soil reinforcement treatment and the energy dissipation net structure, effectively improving the scour protection ability of the offshore wind power pile foundation. The solidified soil forms a stable protection layer, while the double-layer energy dissipation net further enhances the protection effect through multiple mechanisms such as slowing down the water flow velocity, dispersing the water flow energy, and promoting sediment deposition. Compared with the prior art, the present invention can more effectively resist the impact of strong water flows and waves, reduce soil erosion, and ensure the stability and safety of the pile foundation.

[0042] (3) The energy dissipation net of the present invention adopts a double-layer spherical reticulated shell structure. Different materials and pore sizes are selected for the surface layer and the inner layer respectively, which not only ensures flexibility but also enhances wear resistance. At the same time, the addition of the viscous damper mimics the flexible damping effect of aquatic plants, not only improving the energy dissipation effect but also enhancing the adaptability of the energy dissipation net to complex marine environments. This design makes the energy dissipation net not easily age and damage during long-term use, reducing the maintenance cost.

[0043] (4) By collecting the geological conditions of the seabed where the offshore wind power pile foundation is located, establishing a hydrodynamic model, simulating the scour situation of the water flow on the seabed, and combining with further scour simulation of the solidified soil and the energy dissipation net, data support is provided for the anti-scour protection of the energy dissipation net and the solidified soil, and the optimal solution is selected, which can effectively resist water flow scour and improve the stability of the pile foundation.

[0044] (5) The solidified soil protection layer in the present invention forms a bottom protection structure with saturation, strong water stability, anti-scour property, integral plate property, and boundary ductility through specific material ratios and construction processes. The protection layer is combined with the energy dissipation net to form a double protection system, further improving the scour protection effect. Since the corresponding protective solidified soil is selected according to the scour depth, the effectiveness of the protection layer is ensured. The solidified soil and the energy dissipation net support each other and jointly resist water flow scour, realizing the superposition and enhancement of the protection effect and improving the reliability of the entire protection system. Description of the Drawings

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings;

[0046] Figure 1 is a three-dimensional structure diagram of a preferred embodiment of the present invention;

[0047] Figure 2 is a diagram of the pore size of the inner and outer energy dissipation nets of a preferred embodiment of the present invention;

[0048] Figure 3 is a connection diagram of the inner and outer energy dissipation nets of a preferred embodiment of the present invention;

[0049] Figure 4 is a shape diagram of the energy dissipation net of a preferred embodiment of the present invention;

[0050] Figure 5 is a simple installation diagram of a preferred embodiment of the present invention;

[0051] In the figure: 1, offshore wind power pile foundation; 2, energy dissipation net; 3, bracket; 4, upper fixator; 5, solidified soil; 6, lower fixator; 7, surface energy dissipation net; 8, inner energy dissipation net; 9, viscous damper. Detailed implementation manners

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0053] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0054] In the description of the present application, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the protection scope of the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0055] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "coupled" shall be construed broadly. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood through specific circumstances.

[0056] Application Overview:

[0057] With the increasing global demand for renewable energy, offshore wind power, as a clean and sustainable energy form, is developing rapidly. The construction of offshore wind power facilities involves a large number of complex engineering technologies. Among them, the pile foundation, as a key structure to support wind turbines, its stability and safety are crucial. However, due to the particularity of the marine environment, especially the continuous action of waves and currents, the seabed around the pile foundation is prone to scouring, resulting in soil loss, which affects the bearing capacity and overall stability of the pile foundation. To solve this problem, the commonly used scour protection methods at present include rock riprap, concrete block riprap, and rigid energy dissipation nets;

[0058] Although the existing scour protection methods can alleviate the scour problem to a certain extent, they still have some obvious deficiencies: 1. Rigid protection methods such as rock riprap and concrete block riprap are prone to displacement or damage under strong water flow and wave impacts, and cannot provide continuous and effective protection; 2. Although the rigid energy dissipation net can disperse the water flow, its fixed structure and single material properties are difficult to adapt to the complex marine environment, and it is prone to aging and damage during long-term use, resulting in high maintenance costs.

[0059] This application proposes a construction method and device for scour protection of offshore wind power pile foundations based on an energy dissipation net, aiming to solve the deficiencies in the prior art through a double-layer flexible energy dissipation net.

[0060] Exemplary method:

[0061] A construction method for scour protection of offshore wind power pile foundations based on an energy dissipation net, comprising the steps of:

[0062] S1. Collect the geological conditions of the seabed where the offshore wind power pile foundation is located, and simulate the scour of the underwater offshore wind power pile foundation;

[0063] S2. According to the simulation results, perform corresponding solidified soil reinforcement treatment around the base of the offshore wind power pile;

[0064] S3. According to the simulation results, design and prepare the energy dissipation net, and simulate the water flow scour under the protection of the energy dissipation net;

[0065] S4. According to the design requirements, transport the prepared energy dissipation net to the location of the offshore wind power pile foundation for installation;

[0066] S5. Regularly inspect the energy dissipation net and the solidified soil, and real-time detect the water flow and sediment conditions around the offshore wind power pile foundation.

[0067] In step S1, the geological condition data includes: seabed topography, water flow velocity, soil type, density, particle size distribution; the geological condition data can be obtained through on-site exploration, historical data review, and remote sensing technology;

[0068] In step S1, establish a hydrodynamic model to simulate the scour of the seabed where the offshore wind power pile foundation is located by water flow;

[0069] Perform grid division on the flow field around the pile foundation through CFD;

[0070] Set the initial water depth and velocity field according to the collected geological condition data;

[0071] Describe the turbulent characteristics of the water flow through the k-ε turbulence model;

[0072] k equation: Where, ui is the component of the water flow velocity in the i-th direction, k is the turbulent kinetic energy, xi, xj are the components of the spatial coordinates in the i-th and j-th directions, ν is the molecular viscosity, νt is the turbulent viscosity, σk is the Prandtl number of the turbulent kinetic energy, pk is the generation term of the turbulent kinetic energy, ρ is the fluid density, and τ is the turbulent kinetic energy dissipation rate;

[0073] ε equation: Where, στ is the Prandtl number of the turbulent kinetic energy dissipation rate, C 1τ ,C 2τ are model constants;

[0074] The suspended sediment concentration of the sediment transport suspended load is where qs is the suspended sediment flux per unit width, u* is the friction velocity, and H is the water depth;

[0075] The local scour depth around the offshore wind turbine pile foundation is where K 1 is the soil property coefficient, g is the acceleration due to gravity, s is the ratio of sediment density to water density, and dp is the sediment particle diameter.

[0076] According to the simulation, the water flow becomes turbulent and disordered around the pile foundation, generating a horseshoe vortex in front of the structure and shedding behind the structure. The turbulence intensifies, increasing the shear stress at the bottom of the wind power foundation and the sediment transport rate, thus causing scour of the wind turbine foundation; an erosion pit is likely to form on the seabed where the offshore wind turbine pile foundation is located, reducing the embedded depth of the pile foundation and seriously endangering the safety and stability of offshore structures.

[0077] In step S2, the solidified soil protection forms a bottom protection structure through the saturation, strong water stability, erosion resistance, integral plate property, and boundary ductility of the silt solidified soil.

[0078] The silt solidified soil is obtained by adding an inorganic composite solidifying material to natural silt, causing a series of hydrolysis and hydration reactions between the silt and the solidifying material, generating a large amount of gelling substances and crystalline substances.

[0079] The main material used for the silt solidified soil is natural silt, mixed with an inorganic composite solidifying material and an additive. The inorganic composite solidifying material includes: cement, lime, fly ash, and gypsum;

[0080] where the mass ratio of natural silt, cement, lime, fly ash, gypsum, and additive is: 1: 0.05 - 0.15: 0.01 - 0.05: 0.1 - 0.3: 0.01 - 0.02: 0.05 - 0.01;

[0081] Mix the above materials evenly and inject them into the predetermined position, i.e., around the offshore wind turbine pile foundation;

[0082] When the solidified soil is first injected into the seabed, the solidified soil is in a fluid state. Affected by the water flow washout, only a part of it adheres naturally, and the grouting rate is 1 - 2 m 3 / min to avoid excessive washout of the solidified soil by the water flow;

[0083] After the solidified soil is injected into the seabed, part of the solidified soil will naturally adhere to the seabed, forming a preliminary protection layer. When the accumulated thickness is 20 - 50 cm, the solidified soil can adhere well;

[0084] After the initial attachment of the solidified soil, continue to inject the solidified soil until the required thickness of the protective layer is reached, with the grouting rate at 4 - 6m 3 / min;

[0085] After the filling is completed, let the solidified soil flow naturally and start to initially harden. After 5 - 7 hours, the solidified soil will gradually form an aggregate of "granules - bound water - cementing agent", with a certain anti - scouring ability;

[0086] 4 - 6 hours after the initial hardening, the solidified soil will further harden to form a protective layer with integral plate property and certain strength.

[0087] In step S2, select the corresponding protective solidified soil according to the scouring depth, and the filling depth of the solidified soil is equal to the local scouring depth;

[0088] According to the different scouring pit ranges and depths, four levels of protection forms are adopted;

[0089] Level - 1 protection is applicable to the local scouring depth d m ≤1m, the filling depth of the solidified soil is greater than 0.8m. Continue to inject the solidified soil on the filled surface until the horizontal protection range of the solidified soil reaches 2 - 3 times the pile diameter;

[0090] Level - 2 protection is applicable to the local scouring depth 1m < d m ≤3m. Continue to inject the solidified soil on the filled surface, and the upper part of the solidified soil forms a natural slope until the horizontal protection range of the solidified soil reaches 2 - 3 times the pile diameter;

[0091] Level - 3 protection is applicable to the local scouring depth d m > 3m, and the scouring depth is long and narrow, and the scouring range is small. Continue to inject the solidified soil on the filled surface, and the upper part of the solidified soil forms a natural slope until the horizontal protection range of the solidified soil reaches 2 - 3 times the pile diameter;

[0092] Level - 4 protection is applicable to the local scouring depth d m > 3m, and when the scouring range is large; directly inject the solidified soil with a horizontal protection range of 2 - 3 times the pile diameter; after the filling is completed, the surface height of the solidified soil is 2.0m lower than the surrounding seabed;

[0093] As Figure 1 、 Figure 2 and Figure 3 shown, in step S3, the energy - dissipation net is designed as a double - layer spherical reticulated shell structure, with viscous dampers arranged between the reticulated shells, imitating the flexible damping effect of aquatic plants, reducing the water flow velocity, promoting sediment deposition, and reducing scouring;

[0094] Aquatic plants have the effect of slowing down the water flow speed in the natural environment because the stems and leaves of aquatic plants swing in the water flow, increasing the frictional resistance between the water and the plants. The energy dissipation net imitates this flexible structure and can absorb part of the kinetic energy through its own deformation when the water flow passes, thereby reducing the water flow speed and reducing the erosion of the pile foundation.

[0095] The energy dissipation net is designed as a double-layer spherical reticulated shell structure;

[0096] The surface energy dissipation net selects materials with a higher porosity, flexibility, and corrosion resistance, including: one or a mixture of polypropylene, polyester fiber, and nylon;

[0097] The inner energy dissipation net selects materials with a lower porosity, wear resistance, and impact resistance, including: one or a mixture of high-density polyethylene and glass fiber reinforced plastic;

[0098] The aperture of the surface energy dissipation net is 40 - 80 mm, and the aperture of the inner energy dissipation net is 20 - 40 mm; the distance h between the two layers of nets is 0.5 - 1 m;

[0099] The distance between the two layers of reticulated shells is adjusted according to the water flow speed and the turbulence intensity to ensure the best energy dissipation effect; h = β·v a ·(Tu) b , where β is the energy dissipation net coefficient, v is the water flow speed, Tu is the turbulence intensity, and a, b are exponents, reflecting the influence degree of the water flow speed and the turbulence intensity on the optimal distance.

[0100] A number of viscous dampers are connected between the surface energy dissipation net and the inner energy dissipation net. The flexible structure and the viscous dampers work together to reduce the water flow speed and promote sediment deposition.

[0101] The working principle of the viscous damper is to generate a damping force through the flow of liquid in the small holes of the sealed oil cavity; the damping force is related to the viscosity μ of the liquid and the geometric characteristics of the channel, , where L is the channel length of the viscous damper, and dh is the aperture of the viscous damper.

[0102] The spherical shell radius of the inner energy dissipation net is R 1 , where R is required 1 ≥4r, where r is the pile foundation radius;

[0103] The spherical shell radius of the surface energy dissipation net is R 2 =R 1 +h;

[0104] Then, to ensure that the energy dissipation net can effectively cover the area around the pile foundation and considering the function of the energy dissipation net, the cut-off height hc is set as the height from the center of the sphere minus the height H of the support plus an additional safety margin dsafe. The safety margin is to ensure that even under extreme conditions, the energy dissipation net can maintain effective protection for the pile foundation. Therefore, the cut-off height is

[0105] The angle range between the two layers of nets is between 10° - 30°. This angle refers to the included angle between the normal directions of the two layers of nets at the contact point, which can help better disperse the water flow, reduce the local impact force, and maintain the stability of the structure.

[0106] The viscous dampers should be evenly distributed between the two layers of nets to ensure the stability of the entire reticulated shell structure and a uniform energy dissipation effect; at the key positions with large water flow impacts, including the leading edge and trailing edge of the reticulated shell, the density of the viscous dampers increases to enhance the support and energy dissipation effect at these positions; the density of the viscous dampers is 10 - 12 per m at the top of the energy dissipation net 2 , decreasing by 1 per m every 20 - 30 cm downward 2 , until it reaches 5 - 6 per m 2 , then increasing by 1 per m every 20 - 30 cm downward 2 , until it reaches 10 - 12 per m 2 .

[0107] And the viscous dampers should be distributed not only radially but also circumferentially to ensure sufficient support for the reticulated shell in all directions, that is, the viscous dampers all point to the center of the spherical shell.

[0108] Steps for preparing the energy dissipation net:

[0109] Use the selected materials to weave or manufacture the reticulated shell, ensure that the mesh holes meet the design requirements, and prepare it into an energy dissipation net shape as Figure 4 shown;

[0110] When laying the two layers of nets, first spread out the inner layer of the energy dissipation net on a flat surface, then gradually tighten it towards the center, tightly fit and fix both sides of the energy dissipation net through fasteners, and gradually form a hemispherical shape by using the supporting effect of the viscous dampers. Connect the outer layer of the energy dissipation net in the same way, and then connect the two energy dissipation nets through the viscous dampers at the required angle;

[0111] To ensure the formation of an accurate hemispherical shape, use a hemispherical mold or support to assist in the forming of the reticulated shell; after forming, remove the mold or support;

[0112] When a rough hemispherical shape is formed, fine-tune the shape of the reticulated shell by adjusting the tension of the viscous dampers;

[0113] As Figure 5As shown, to ensure stability, the upper truncated part of the double-layer energy dissipation net is hooked to the upper fixator of the pile foundation support, and the lower part of the double-layer energy dissipation net is hooked to the lower fixator on the solidified soil;

[0114] And to maintain the hemispherical structure of the energy dissipation net in water, several upper fixators on the support are circularly arrayed with the pile foundation as the center, and several lower fixators on the solidified soil are also circularly arrayed with the pile foundation as the center;

[0115] Through the support and tension of the upper and lower fixators and the viscous damper, they work together to construct the double-layer spherical shell shape of the energy dissipation net.

[0116] In step S3, the simulation of the water flow scouring under the protection of the energy dissipation net is based on the hydrodynamic model in step S1, but the influence of the energy dissipation net is added;

[0117] The influence of the energy dissipation net is calculated as follows:

[0118] The slowdown of the water flow velocity by the energy dissipation net where, v in is the water flow velocity flowing into the energy dissipation net, vout is the water flow velocity flowing out of the energy dissipation net, κ is the slowdown coefficient of the energy dissipation net, and L x is the path length of the water flow passing through the energy dissipation net;

[0119] Calculating the slowdown coefficient of the energy dissipation net needs to consider the characteristics of the double-layer reticulated shell structure, including the relative position and angle between the two layers of the net, and the influence of different porosity; the calculated slowdown coefficient is where, Cd 1 , Cd 2 are the drag coefficients of the surface and inner layer energy dissipation nets, A 1 , A 2 are the effective areas of the surface and inner layer energy dissipation nets, V 1 , V 2 are the volumes of the surface and inner layer energy dissipation nets, is the interaction slowdown coefficient between the two layers of the net, and θ is the angle between the normal directions of the two layers of the net at the contact point;

[0120] The influence of the energy dissipation net on the water flow pressure is where, pout is the water flow pressure flowing into the energy dissipation net, pin is the water flow pressure flowing out of the energy dissipation net, Δp is the pressure drop caused by the energy dissipation net, and ρ w is the density of seawater;

[0121] The influence of the energy dissipation net on the sediment deposition is where, C out , C in are the sediment concentrations flowing into and out of the energy dissipation net.

[0122] In step S4,

[0123] Ensure that all energy dissipation net components have been prepared according to the design requirements, and check whether the solidified soil protective layer around the offshore wind power pile foundation has been completely hardened and reached the required strength;

[0124] Connect the double-layer energy dissipation net to the pile foundation support through the upper fixator, ensuring a firm connection and adaptability to water flow impact; evenly distribute the lower fixator on the solidified soil protective layer and connect it to the lower part of the double-layer energy dissipation net to form a stable support structure;

[0125] By adjusting the tension and position of the viscous damper, ensure that the energy dissipation net can maintain the designed hemispherical structure in water.

[0126] In step S5, install equipment such as water flow velocity monitors and sediment concentration monitors around the energy dissipation net to monitor the water flow and sediment conditions in real time. According to the monitoring results and actual situation, regularly inspect and maintain the energy dissipation net.

[0127] Specific test examples:

[0128] This experiment aims to verify the effectiveness of the offshore wind power pile foundation scour protection method based on the double-layer flexible energy dissipation net. By simulating the water flow scour conditions under different parameter conditions, evaluate the performance of the energy dissipation net in reducing the scour depth, lowering the water flow velocity, and promoting sediment deposition;

[0129] Table 1 Experimental parameters

[0130] Parameter Name Unit Range / Value Pile Foundation Radius m 6.0 Surface Energy Dissipation Net Aperture mm 40-80 Inner Energy Dissipation Net Aperture mm 20-40 Distance between Two Layers of Nets m 0.5-1 Angle between Two Layers of Nets Degree 10-30 Inflow Velocity m / s 2.6 Scouring Time s 200

[0131] Table 2 Simulation data

[0132]

[0133] The size of the surface layer pore diameter directly affects the water flow penetration ability. When the pore diameter increases from 55mm to 65mm, part of the water flow forms turbulent disturbances through the mesh holes, and the remaining kinetic energy is absorbed by the flexible deformation of the net body, effectively reducing the flow velocity and reducing scour. However, when the pore diameter is too large, the water flow directly penetrates the surface layer net, the energy dissipation effect weakens, and at the same time, the structural vibration intensifies the turbulent energy, resulting in the rebound of the scour depth. Therefore, a moderate pore diameter can not only disperse the water flow impact but also dissipate energy through turbulent disturbances.

[0134] The inner layer net, as the second barrier, needs to have both wear resistance and resistance characteristics. When the inner layer pore diameter increases from 20mm to 35mm, the dense mesh holes further slow down the flow velocity, and at the same time, the viscous damper converts the remaining kinetic energy into heat energy. However, too small a pore diameter will cause the water flow to form local high-pressure areas by bypassing, weakening the overall energy dissipation effect; while too large a pore diameter will reduce the barrier density and the scour depth will rebound. A moderate inner layer pore diameter can balance the resistance and energy dissipation efficiency.

[0135] The distance and angle between the two layers of nets jointly affect the water flow path and energy dissipation. When the distance is 0.7 m, the water flow experiences multiple deflections between the double-layer nets, prolonging the energy dissipation time and reducing the scouring depth to 0.65 m. If the distance is too large, the water flow will regain its kinetic energy and the energy dissipation effect will be weakened. When the angle is 20°, the water flow is evenly dispersed, avoiding local impacts. If the angle is too large, separated eddies will be induced and the scouring depth will increase.

[0136] In addition, the viscous damper converts the kinetic energy of the water flow into heat energy through the viscous resistance of the liquid, reducing the flow velocity. Its density is distributed as "high at the top - low in the middle - high at the bottom", adapting to the velocity gradient of the water flow from top to bottom.

[0137] Based on the ideal embodiments of the present invention as inspiration, through the above description, relevant personnel can make various changes and modifications within the scope not deviating from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. An offshore wind power pile foundation scour protection device based on an energy dissipation net, characterized in that: include: A solidified soil is arranged at the bottom of the offshore wind power pile foundation, and a bracket is arranged in the middle of the offshore wind power pile foundation; the bracket is provided with a plurality of upper fixtures in a circular array with the pile foundation as the center, and the solidified soil is provided with a plurality of lower fixtures in a circular array with the pile foundation as the center; an energy dissipation net is connected between the upper fixture and the lower fixture; The energy dissipation network includes: a surface energy dissipation network, an inner energy dissipation network, and a viscous damper connecting the surface energy dissipation network and the inner energy dissipation network; The aperture of the surface energy dissipation net is 40-80mm, the aperture of the inner energy dissipation net is 20-40mm, the material of the surface energy dissipation net is corrosion-resistant material; the material of the inner energy dissipation net is wear-resistant and impact-resistant material.

2. The offshore wind power pile foundation scour protection device based on the energy dissipation net according to claim 1 is characterized by: The main material used for the solidified soil is natural silt mixed with inorganic composite solidifying materials and additives, wherein the inorganic composite solidifying materials include cement, lime, fly ash and gypsum; Wherein, the mass ratio of the natural sludge, the cement, the lime, the fly ash, the gypsum and the additive is: 1: 0.05-0.15: 0.01-0.05: 0.1-0.3: 0.01-0.02: 0.05-0.

01.

3. The offshore wind power pile foundation scour protection device based on the energy dissipation net according to claim 1 is characterized by: The material of the surface energy dissipation net is one or a mixture of polypropylene, polyester fiber and nylon; the material of the inner energy dissipation net is one or a mixture of high-density polyethylene and glass fiber reinforced plastic.

4. The offshore wind power pile foundation scour protection device based on the energy dissipation net according to claim 1 is characterized by: The angle between the inner energy dissipation net and the surface energy dissipation net ranges from 10° to 30°.

5. The offshore wind power pile foundation scour protection device based on the energy dissipation net according to claim 1 is characterized by: The distance h between the inner energy dissipation net and the surface energy dissipation net is 0.5-1m.

6. The offshore wind power pile foundation scour protection device based on the energy dissipation net according to claim 1 is characterized by: The viscous dampers are evenly distributed in the energy dissipation net; the density of the viscous dampers changes from top to bottom: high density to low density and then to high density; the density of the viscous dampers at the top of the energy dissipation net is 10-12 pieces / m 2 , decreasing by 1 / m every 20-30 cm downwards 2 , up to 5-6 pieces / m 2 Then increase by 1 / m every 20-30 cm downwards 2 , up to 10-12 pieces / m 2 .

7. A construction method for offshore wind power pile foundation scour protection based on an energy dissipation net, based on an offshore wind power pile foundation scour protection device based on an energy dissipation net according to claims 1-6, characterized in that: include: S1. Collect the geological conditions of the seabed where the offshore wind turbine pile foundation is located and simulate the scouring of the underwater offshore wind turbine pile foundation; S2. According to the simulation results, corresponding soil reinforcement treatment is carried out around the offshore wind power pile base; S3. Design and prepare the energy dissipation net according to the simulation results, and simulate the water flow scouring under the protection of the energy dissipation net; S4. According to the design requirements, the prepared energy dissipation net is transported to the location of the offshore wind power pile foundation for installation; S5. Regularly inspect the energy dissipation net and solidified soil, and monitor the water flow and sediment conditions around the offshore wind turbine pile foundation in real time.

8. The offshore wind power pile foundation scour protection construction method based on the energy dissipation net according to claim 7 is characterized by: In step S1, a fluid dynamics model is established to simulate the scouring of the seabed where the offshore wind turbine pile foundation is located by water flow; Meshing the flow field around the pile foundation using CFD; Set the initial water depth and velocity field based on the collected address condition data; The turbulent characteristics of water flow are described by the k-ε turbulence model; k equation: Among them, u i is the component of water velocity in the i-th direction, k is the turbulent kinetic energy, x i ,x j is the component of the spatial coordinate in the i-th and j-th directions, ν is the molecular viscosity, and ν t is the turbulent viscosity, σ k is the Prandtl number of turbulent kinetic energy, p k is the generation term of turbulent kinetic energy, ρ is the fluid density, and τ is the turbulent kinetic energy dissipation rate; Epsilon equation: Among them, σ τ is the Prandtl number for the turbulent kinetic energy dissipation rate, C 1τ ,C 2τ is the model constant; The suspended sediment concentration of the sediment-carrying suspended load is Among them, q s Suspended sediment flux per unit width, u * is the friction velocity, H is the water depth; The local scouring depth around the offshore wind turbine pile foundation is Among them, K1 is the soil property coefficient, g is the gravitational acceleration, s is the ratio of sediment density to water density, d p is the diameter of sediment particles.

9. The offshore wind power pile foundation scour protection construction method based on the energy dissipation net according to claim 8 is characterized by: In step S3, the simulation of water flow scouring under the protection of the energy dissipation net is based on the fluid dynamics model in step S1, and the influence of the energy dissipation net is added; The impact of the energy dissipation network is calculated as follows: Energy dissipation net slows down water flow Among them, v in is the water velocity flowing into the energy dissipation network, v out is the water velocity flowing out of the energy dissipation network, κ is the mitigation coefficient of the energy dissipation network, L x is the path length of water flow through the energy dissipation network; The calculation of the mitigation coefficient of the energy dissipation network needs to consider the characteristics of the double-layer lattice shell structure, including the relative position and angle between the two layers of the network, and the influence of different porosities; the calculation of the mitigation coefficient is Among them, C d1 ,C d2 is the resistance coefficient of the surface and inner energy dissipation nets, A1, A2 are the effective areas of the surface and inner energy dissipation nets, V1, V2 are the volumes of the surface and inner energy dissipation nets, is the interaction mitigation coefficient between the two layers of mesh, θ is the angle between the normal directions of the two layers of mesh at the contact point; The influence of the energy dissipation network on the water flow pressure is Among them, p out is the water pressure flowing into the energy dissipation network, p in is the water pressure flowing out of the energy dissipation network, Δp is the pressure drop caused by the energy dissipation network, ρ w is the density of seawater; The effect of energy dissipation net on sediment deposition is Among them, C out ,C in is the sediment concentration flowing into and out of the energy dissipation network.

10. The offshore wind power pile foundation scour protection construction method based on the energy dissipation net according to claim 7, characterized in that: Truncation calculation of energy dissipation net: Assume that the spherical shell radius of the inner energy dissipation net is R1, where R1≥4r, where r is the pile foundation radius; set the truncation height h c Add an additional safety margin d to deduct the height H of the bracket from the center of the sphere safe , cut-off height

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