Method for calculating horizontal bearing capacity of single pile of offshore wind turbine

Abstract

The invention discloses a method for calculating the horizontal bearing capacity of a single pile of an offshore wind turbine. The method comprises the steps that microscopic parameters of soil particles are calibrated through a discrete element method; generating a foundation by adopting a sand rain method in a supergravity environment based on the friction force and the rolling friction force of the microscopic parameters of the soil body particles; generating a single-pile grid by using a finite difference method and penetrating the single-pile grid into a soil body; applying a monotonous horizontal load to the top surface of the single pile; all the data are exported, and the data are processed and analyzed according to the similarity ratio law of centrifugal simulation. According to the method for preparing the foundation through the sand rain method under the high gravity field, the preparation process of a microscopic foundation soil body is simulated based on the real physical experiment foundation preparation process, and the foundation with the porosity capable of meeting the specified requirement and uniform force chain can be generated.

Description

Technical Field

[0001] The present application relates to the technical field of calculating the horizontal bearing capacity of a single pile of an offshore wind turbine, and in particular to a method for calculating the horizontal bearing capacity of a single pile of an offshore wind turbine. Background Art

[0002] In the design of single piles, the horizontal ultimate bearing capacity of the pile is an extremely important part. In traditional engineering, when analyzing the stress and deformation of the pile body, it is often necessary to first calculate the horizontal ultimate bearing capacity of the pile (such as the py curve method). However, there are disputes in the academic community about the specific definition of the failure mode of single piles, the distribution mode of the pile side soil pressure of large-diameter single piles under the limit state, and the displacement failure mode of the soil around the pile. One of the reasons for the controversy is that it is difficult to analyze and understand the stress mechanism of single piles from a microscopic scale at the current technical level. If it is possible to analyze and calculate from a microscopic perspective, it will promote theoretical progress and eliminate some disputes. Therefore, the industry has proposed a numerical simulation method, namely the discrete element method, which can simulate soil particles from a microscopic scale.

[0003] The discrete element method is a numerical simulation method specifically used to solve discontinuous medium problems. This method regards soil particles as composed of discrete spheres, allowing the spheres to translate and rotate. Therefore, the soil is regarded as a discontinuous discrete medium. Large displacement, rotation and sliding can exist inside it, so that the nonlinear large deformation characteristics in the cleaved soil can be simulated more realistically. The general solution process of the discrete element method is: discretize the solution space into a discrete element unit array, and connect the two adjacent units with a reasonable release relationship according to the actual problem; the relative displacement between the units is the basic variable, and the normal and tangential forces between the two units can be obtained from the relationship between force and relative displacement; the resultant force and torque of the external force between the unit and other units in all directions and other physical fields acting on the unit are calculated, and the acceleration of the unit can be obtained according to Newton's second law of motion; it is time-integrated to obtain the velocity and displacement of the unit. Thus, the physical quantities such as velocity, acceleration, angular velocity, linear displacement and rotation angle of all units at any time are obtained.

[0004] The current problem in the industry is that the microscopic simulation method provided by the discrete element method is difficult to connect with the macroscopic one; the discrete element method can discretize the soil into separate spherical particles, but if the discrete element method is used directly to simulate actual projects, the number of simulated particles may reach trillions, and the current computer performance cannot meet this level of calculation. The use of the discrete element method in the industry is generally limited to small unit tests, and few people use the discrete element method to simulate large projects.

[0005] In the existing technology, finite element method or finite difference method is used for analysis. There are few studies on offshore wind turbine pile foundations at the micro level. Among them, YuPeng et al. (2023) also used the DEM-FDM (discrete element-finite difference method coupling) method to calibrate the parameters of the soil by directly comparing the centrifuge test results and carry out a series of suction tube foundation simulations under different working conditions such as torsion and horizontal load. The technical problems of this scheme are: the scheme takes a long time to calculate the horizontal bearing capacity; the calculation is difficult; and the computer requirements are high. Therefore, a method for calculating the horizontal bearing capacity of a single offshore wind turbine pile is needed. Summary of the invention

[0006] The present application provides a method for calculating the horizontal bearing capacity of a single pile of an offshore wind turbine.

[0007] In the first aspect, the present application provides a method for calculating the horizontal bearing capacity of a single pile of an offshore wind turbine, which adopts the following technical solution:

[0008] A method for calculating the horizontal bearing capacity of a single offshore wind turbine pile comprises the following steps:

[0009] A. Use discrete element method to calibrate soil particle microscopic parameters;

[0010] B. The friction and rolling friction based on the microscopic parameters of soil particles are used to generate the foundation using the sand rain method in a hypergravity environment;

[0011] C uses the finite difference method to generate a single pile grid and penetrates it into the soil;

[0012] D. applying a monotonic horizontal load to the top surface of the single pile to obtain contact information of the pile body, wherein the contact information of the pile body includes contact coordinates, contact-connected particles and pile body unit information, magnitudes and directions of all contact forces on each contact, and coordinate positions of each node of the pile body;

[0013] E. Derive the contact information of the pile body contact and process and analyze the data according to the similarity law of centrifugal simulation.

[0014] Furthermore, in step A, the contact model between particles uses a nonlinear loading contact model, and the nonlinear loading contact model is established and verified using particle experiments. The force-displacement relationship between the contacts can be generally expressed by the formula:

[0015] F t =F l +F d ,

[0016] M c =M r

[0017] The calculation of the forces between particles includes normal force, tangential force, rotational resistance, and damping force. The calculation formula for normal force is:

[0018] Where: Fl is the nonlinear contact force, Fd is the viscous force, Mr is the rotational resistance moment;

[0019] It can be expressed as follows:

[0020]

[0021] In the formula, is the normal contact force in the contact model, is the normal vector of the contact surface between contacts, is the tangential contact force in the contact model;

[0022] k 1 With k 2 The relationship is given by the following formula:

[0023]

[0024] Among them, k 1 represents the initial stiffness of the loading section, k 2 represents the initial stiffness of the unloading section, λ p is the plasticity ratio. When the plasticity ratio is close to 0, the model will not show plastic response. Let λ p = 0.01, it is considered that k 1 =k 2 With k 2 Basically equal;

[0025] Among them, k 1 The calculation formula is as follows:

[0026]

[0027] In the formula, E * is the effective Young's modulus between contacts, and

[0028]

[0029] R 1 , R 2 is the radius of the two contact objects. If one of the contact objects is a wall unit, then R P is the radius of the contact particle;

[0030] In the nonlinear loading model, the normal contact displacement between particles is recorded in real time. The model stores and remembers the maximum normal displacement value δ of the relative motion between each particle. max, in k 2 In the unloading stage, δ max =δ n , that is, in k 2 When calculating the unloading segment, the maximum displacement during the last loading is recorded, so that the unloading starts from the maximum displacement;

[0031] Effective Young's modulus E between contacts * Calculate as follows:

[0032]

[0033] In the formula, the superscripts (1) and (2) represent the Poisson's ratio and shear modulus of the two contacting objects, respectively; the calculation formula of the tangential force is:

[0034] Tangential Contact Force in Contact Models It can be updated with:

[0035]

[0036] In the formula, is the tangential contact force at the beginning of each time step, Δδ s is the relative tangential displacement increment, and the tangential stiffness is the normal displacement δ n Function:

[0037]

[0038] G * is the effective tangent modulus and k sf Is the scaling factor, the default scaling factor k sf =1;

[0039] The calculated upper and lower limits are shown in the formula:

[0040]

[0041] The calculation formula for rotation resistance is:

[0042] Rotational resistance moment M in contact model c It can be updated with:

[0043]

[0044] In the formula is the rotational stiffness, Δθ b is the relative rotation angle between the contact surfaces; the rotational stiffness is defined as:

[0045]

[0046] The upper and lower limits of the rotational resistance moment are specified as:

[0047]

[0048] The damping force is calculated as:

[0049] The damping force consists of two parts: normal force and tangential force:

[0050]

[0051] In the normal direction:

[0052]

[0053] In the formula, is the effective contact mass between two contacting particles, is the normal translational velocity, and β n is the normal damping coefficient;

[0054] The damping force in the tangential direction is given by:

[0055]

[0056] Furthermore, the method for generating a foundation by using the sand rain method in a hypergravity environment includes:

[0057] Under the hypergravity field, the falling sand method was used to generate a foundation model with a set porosity, the gravity value was reduced to 0g, and the gravity field with a variation range of foundation porosity less than 3% was screened;

[0058] In a hypergravity field, non-overlapping particles are generated within a fixed height, and this process is repeated by free falling from a fixed height to generate an initial sample;

[0059] The initial sample weight is reduced to 0g, and the porosity screening is performed to obtain a sample whose foundation porosity is greater than the porosity of the final sample to obtain a secondary sample;

[0060] Under the condition of zero gravity, a confining pressure of less than 5 kPa is applied to the secondary sample to generate a uniform force chain.

[0061] Furthermore, a single pile model with grids divided is generated above the foundation, and a constant speed is applied to the top surface of the single pile, wherein the speed is 0.2-0.5 m / s.

[0062] Furthermore, during the process of pushing the pile with a monotonic horizontal load applied to the top surface of the single pile, the difference between the resultant force calculated from the finite grids of the pile body and the pile body subjected to the contact of discrete soil bodies is no more than 5%.

[0063] In a second aspect, the present application provides a computer device, which adopts the following technical solution:

[0064] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the method described in the first aspect when executing the program.

[0065] In a third aspect, the present application provides a computer-readable storage medium, which adopts the following technical solution:

[0066] A computer-readable storage medium stores a computer program that can be loaded by a processor and execute any one of the methods in the first aspect.

[0067] In summary, the present application includes at least one of the following beneficial technical effects:

[0068] (1) The present invention provides a method for simulating large-scale engineering projects using the discrete element method through the complete digital centrifuge simulation technology of the present invention, thereby overcoming the difficulty of traditional discrete element methods in extending from microscopic scale to macroscopic scale;

[0069] (2) The present invention can simulate various working conditions of large-scale engineering at a small scale through the complete digital centrifugal simulation technology of the present invention, and further solve engineering problems from a microscopic perspective; (3) The present invention simulates the preparation process of microscopic foundation soil based on the preparation process of foundation by the sand rain method under the supergravity field of the present invention, and can generate a foundation with a porosity that meets the specified requirements and a uniform force chain;

[0070] (4) The present invention can directly gain insight into the soil displacement field, stress field, and velocity field that are difficult to monitor in reality from a microscopic perspective, thus providing a basis for the advancement of related theories; BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 It is a schematic flow chart of a method for calculating the horizontal bearing capacity of a single pile of an offshore wind turbine in an embodiment of the present invention;

[0072] Figure 2 It is a schematic diagram of the falling sand method under the super gravity field of the present invention;

[0073] in Figure 2 (a) Flow chart of the falling sand method under high gravity field; Figure 2 (b) Schematic diagram of step 2 in the falling sand method: generation-falling-generation-falling; Figure 2 (c) Generate a specimen with a uniform force chain;

[0074] Figure 3 A diagram showing a discrete element triaxial test and expected results in an embodiment of the present invention;

[0075] in Figure 3 (a) is the expected result diagram of the triaxial test; Figure 3 (b) is the simulation diagram of triaxial test;

[0076] Figure 4 A schematic diagram of loading of a nonlinear loading model in an embodiment of the present invention;

[0077] in Figure 4 (a) Particle experiment and main components of contact force; Figure 4 (b) Normal force curve of nonlinear loading model;

[0078] Figure 5 A flow chart for confirming the supergravity field G in an embodiment of the present invention;

[0079] in Figure 5 (a) Confirmation of the G value of the supergravity field Figure 5 (b) Schematic diagram of digital centrifuge simulation technology case;

[0080] Figure 6 It is a schematic diagram of an example of the invention in the implementation mode of the present invention;

[0081] Figure 7 This is a schematic diagram of step B in an embodiment of the present invention;

[0082] Figure 8 This is a schematic diagram of step C in an embodiment of the present invention;

[0083] Fig. 9 This is the final effect diagram of step D in the implementation mode of the present invention;

[0084] Fig.10 It is a schematic diagram of the forces on the inner and outer surfaces of the pile at different depths in an embodiment of the present invention. DETAILED DESCRIPTION

[0085] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0086] The present application embodiment discloses a method for calculating the horizontal bearing capacity of a single pile of an offshore wind turbine, which adopts the following technical solution:

[0087] A method for calculating the horizontal bearing capacity of a single offshore wind turbine pile comprises the following steps:

[0088] The discrete element-finite difference method coupled single pile horizontal bearing capacity calculation method of the present invention comprises: 1. a foundation composed of soil particles simulated by the discrete element method; 2. a single pile continuum simulated by the finite difference method.

[0089] The characteristic of discrete element method is that the movement of particles can be described by Newton's second law, so that the movement between particles is presented more clearly and intuitively. Therefore, the foundation simulation using discrete element method can reflect the pile-soil mechanism from the real physical mechanism, and then understand the displacement field, stress field, and velocity field distribution pattern of the soil around the horizontally loaded single pile from a microscopic perspective, and more accurately calculate the horizontal bearing capacity of the foundation. The present invention can utilize different particle shapes and microscopic parameters to simulate the soil in different foundation environments. The pile body analysis uses the finite difference method to divide the grid, which is suitable for the calculation of the contact force between single piles of different sizes and soil particles at any position, especially the horizontal bearing capacity analysis of super-large diameter single piles. It should be noted that the calculation methods of the present invention are all secondary developments carried out on the discrete element PFC developed by itasca.

[0090] The calculation process is as follows Figure 1 As shown: The calculation process of the present invention includes:

[0091] A. Use discrete element method to calibrate soil particle microscopic parameters;

[0092] B. Using the sand-rain method to generate foundation in a hypergravity environment;

[0093] C uses the finite difference method to generate a single pile grid and penetrates it into the soil;

[0094] D. Select an appropriate rate to apply a monotonic horizontal load to the top surface of the single pile;

[0095] E Export all data and process and analyze the data according to the similarity law of centrifugation simulation.

[0096] Step A: Use the discrete element method to calibrate the microscopic parameters of soil particles: The foundation material is a discrete particle, and the mechanical behavior of the particle material requires additional triaxial testing for calibration and analysis. The contact model between particles in the present invention uses a nonlinear loading contact model. The simulation diagram and expected result diagram of step A are shown in Figure 2. Figure 4 If the axial strain-stress curve obtained from the triaxial test is consistent with the curve obtained from the test (the general error is not more than 10%, such as Figure 2 As shown in the figure, it is believed that this parameter can better simulate the mechanical properties of the soil.

[0097] In step A, in order to improve the calculation efficiency, in the process of preparing the sample, the present invention adopts an innovative sand rain method under a super gravity field to prepare the sample. The flow chart of the method for preparing the foundation by the sand rain method under a super gravity field is as follows: Figure 2 The specific operations are as follows:

[0098] 1. Determine the gravity value of the hypergravity field. If under normal gravity (i.e. 1g conditions), the calculation process of the discrete element program is slow, so the present invention adopts the method of increasing gravity (i.e. hypergravity field) to improve the calculation efficiency. First, the specific gravity value of the hypergravity field must be confirmed. The confirmation method is: use the falling sand method to generate a foundation model with a specified porosity under the hypergravity field, such as porosity = 0.4; theoretically, the foundation generated by the falling sand method under the hypergravity field will be relatively dense; then reduce the g value to 0g, measure the foundation porosity value, and calculate whether the range of variation is too large. If the range of variation is within an acceptable range (within 3%), it is considered that the gravity field can meet the requirements of falling sand. A higher gravity field will improve the calculation efficiency, but it will also make the foundation denser, which is too different from the specified porosity, and it is difficult to generate a foundation model that meets the requirements. Therefore, the g value should be determined while comprehensively considering the calculation efficiency and model accuracy;

[0099] 2. Using the falling sand method in a supergravity field to generate several layers of samples, such as the present invention generates non-overlapping particles within a specified height under 600g, and then allows them to fall freely at a fixed height under the action of gravity, and repeatedly repeats this process to generate the initial sample. The generation process is as follows: Figure 2 (b)

[0100] 3. Reduce the gravity to 0g, and observe whether the porosity of the sample after falling meets the requirements. The porosity of the generated foundation should be slightly larger than the porosity of the final sample, because the process of adding confining pressure in step 4 will reduce part of the porosity, and a margin should be left for this step. There are two main particle parameters that control the porosity: friction and rolling resistance friction. The higher the friction, the looser the generated sample, that is, the higher the porosity, and vice versa. If the porosity of the generated foundation does not meet the requirements, set new parameters and repeat steps 2-3.

[0101] 4. Apply a small confining pressure to the sample so that the sample generates a uniform force chain. In step 3, since the gravity is 0, the generated foundation is as follows Figure 2 As shown in the non-contact diagram in (c), in order to make the sample have a uniform force chain and facilitate subsequent calculations, the method of servo pressurization is adopted to the six surfaces of the sample. The size of the confining pressure is generally within 5 kPa until the sample generates a uniform force chain and reaches the specified porosity.

[0102] Finally, the particle friction-porosity relationship obtained by trial and error in steps 2-3 can be further applied to the preparation of foundation samples in step B.

[0103] In step A and subsequent steps, a new type of inter-particle contact model and nonlinear loading model written by ourselves are used.

[0104] The model was established and verified using particle experiments. The force-displacement relationship between contacts can be generally expressed by formula 1:

[0105] F t =F l +F d ,

[0106] M c =M r (1.1)

[0107] In this model, the calculation of the force between particles can be divided into four parts: 1. Normal force; 2. Tangential force; 3. Rotational resistance; 4. Damping force, where

[0108] 1. Normal force

[0109] F l is the nonlinear contact force, F d is the viscosity, M r is the rotational resisting moment. Where:

[0110]

[0111] In the formula, is the normal contact force in the contact model, is the normal vector of the contact surface between contacts, is the tangential contact force in the contact model. It can be expressed as follows:

[0112]

[0113] k 1 represents the initial stiffness of the loading section, k 2 represents the initial stiffness of the unloading section, k 1 With k 2 The relationship is given by formula 1.4:

[0114]

[0115] Among them, λ p is the plasticity ratio. When the plasticity ratio is close to 0, the model will not show plastic response. p = 0.01, it is considered that k 1 =k 2 With k 2 Basically equal.

[0116] Among them, k 1 The calculation formula is as follows:

[0117]

[0118] In the formula, E * is the effective Young's modulus between contacts, and

[0119]

[0120] R 1 , R 2 is the radius of the two contact objects. If one of the contact objects is a wall unit, then R P is the radius of the contacting particle.

[0121] In the nonlinear loading model, the normal contact displacement between particles is a real-time record value. The model stores and remembers the maximum normal displacement value δ of the relative motion between each particle. max , the value will be in k 2 Used in the unloading stage. This model stipulates that k in Equation 1.3 2 Unloading section, δ max =δ n , that is, in k 2 When calculating the unloading segment, the maximum displacement during the last loading is recorded so that the unloading starts from the maximum displacement.

[0122] In formula 1.5, the effective Young's modulus E between contacts is * Calculate as follows:

[0123]

[0124] Wherein, the superscripts (1) and (2) represent the Poisson's ratio and shear modulus of the two contacting objects, respectively.

[0125] 2. Tangential force:

[0126] In equation (1.2), the tangential contact force in the contact model is It can be updated with:

[0127]

[0128] In the formula, is the tangential contact force at the beginning of each time step, Δδ s is the relative tangential displacement increment, and the tangential stiffness is the normal displacement δ n Function:

[0129]

[0130] G * is the effective tangent modulus and k sf is the scaling factor. The default scaling factor k sf=1;

[0131] The upper and lower limits calculated by formula (1.8) are shown in formula (1.10):

[0132]

[0133] 3. Rotational resistance:

[0134] In formula (1.2), the rotational resistance moment M in the contact model is c It can be updated with:

[0135]

[0136] In the formula is the rotational stiffness, Δθ b is the relative rotation angle between the contact surfaces; the rotational stiffness is defined as:

[0137]

[0138] The upper and lower limits of the rotational resistance moment are specified as:

[0139]

[0140] 4. Damping force:

[0141] The damping force consists of two parts: normal force and tangential force:

[0142]

[0143] In the normal direction:

[0144]

[0145] In the formula, is the effective contact mass between two contacting particles, is the normal translational velocity, and β n is the normal damping coefficient.

[0146] The damping force in the tangential direction is given by:

[0147]

[0148] The final result diagram of the nonlinear loading model simulation and the simulation diagram of the triaxial test are as follows: Figure 3 As shown in the figure, the normal force-displacement relationship between the nonlinear loading model and the particle test is as follows Figure 4 As shown:

[0149] In step B and thereafter, namely steps B, C, D, and E, the innovative digital centrifugal simulation technology of the present invention needs to be used.

[0150] The so-called digital centrifuge simulation technology is based on the principle of centrifuge test, and applies the similar ratio relationship of physical quantities in centrifuge test to discrete element-finite difference method simulation. Geotechnical centrifuge test is to use the centrifugal force provided by the centrifuge to simulate gravity. According to the similarity criterion, the geometric shape of the prototype is scaled down, and the model is made of soil with the same physical properties, so that its stress state in the centrifugal field is consistent with that of the prototype in the gravity field, so as to study the testing technology of engineering properties.

[0151] The digital centrifuge simulation technology uses the same physical quantity similarity criteria as the geotechnical centrifuge test, but does not rely on centrifugal force to simulate gravity. Instead, it directly sets the environmental gravity in the numerical simulation to generate a hypergravity field. The commonly used physical quantity similarity criteria in centrifuge tests are shown in Table 1:

[0152] Table 1 Similarity criteria for commonly used physical quantities under the condition that gravitational acceleration is Ng

[0153]

[0154] It can be seen that the similarity ratio of displacement is N, and the similarity ratio of particles is 1, which means that under the condition of 100g, 1m in the geotechnical centrifuge test is equivalent to 100m in reality, but the size of the particles does not change. If the sand in the ocean is simulated under the gravity condition of 1g, the number of simulated sand particles will reach the trillion level, and the current computer performance does not support simulation calculations of this magnitude. Therefore, referring to the geotechnical centrifuge test technology, the present invention innovatively uses digital centrifuge simulation technology, that is, in a hypergravity field, a smaller size is used to simulate a larger-scale actual project. For example, to simulate a foundation with a length, width and height of 10m in reality, a digital centrifuge simulation technology is used to increase the gravity to 1000g. In the numerical simulation, the relative foundation size is length, width and height equal to 10m / 1000=1cm, which will greatly reduce the size of the particles, and the conversion of various physical quantities in the model can achieve the simulation of large-scale projects with a small model scale.

[0155] When using digital centrifuge simulation technology, it is necessary to determine an appropriate gravity G value. If the G value is too high, the size of the particles will be too large compared to the actual project scale, and the simulation accuracy will not be high; if the G value is too small, the simulated project size will be too large, the required number of particles will be too high, and the computer will be difficult to run. Therefore, the determination of a reasonable G value is the key to digital centrifuge simulation technology, and the selection of the G value needs to be determined based on the actual project. After calculation, the present invention believes that the maximum simulated G value should not exceed 3000g, and the number of simulated particles should not be less than 200,000, which can meet the needs of large-scale projects. The flow chart for confirming the ultra-gravity field G is as follows. Figure 5 As shown:

[0156] Step B: Generate foundation using the sand rain method in a hypergravity environment: Use the appropriate soil parameters obtained in step A (specifically friction and rolling resistance friction), and repeat the sand dropping process in step A to generate the foundation. In this process, the built-in function of the present invention can automatically calculate the number of particles required for a specified porosity ratio, and realize automatic falling and automatic sample preparation. This step can be completed using the foundation generation function of the present invention. The schematic diagram of the sand rain method and the generation effect diagram are shown in the figure. Figure 6 As shown;

[0157] Step C: Generate a single pile grid using the finite difference method and penetrate the soil: Plan the appropriate grid size and number (it is recommended that the length, width and height of the grid be about one time the particle size), divide the single pile foundation into a finite number of grids, and generate them above the foundation; after the grid is generated, simulate the actual engineering situation and apply a constant downward speed on the top of the single pile to make the pile penetrate slowly; it is recommended to select a slower speed as much as possible while taking into account the time cost, so that the disturbance to the foundation will be minimized. The schematic diagram of the step C process is as follows Figure 7 As shown:

[0158] Step D: Figure 8 As shown, a suitable rate is selected to apply a monotonic horizontal load to the top surface of a single pile: after the pile is penetrated, the soil parameters should be replaced with the final calibrated parameters, that is, replaced with the soil parameters calibrated in step A, so as to facilitate the next step of calculation. After replacing the parameters, the calculation of the mechanical properties of the pile-soil interaction can be performed; a suitable rate is selected to give the top of the pile a constant speed to the right to simulate the process of horizontal loading of the pile (the selection of the speed should be based on the calculation efficiency, and a slower speed should be selected as much as possible to better simulate static loading). The algorithm of the present invention has a built-in program for determining the speed selection, that is, during the pile pushing process, the difference between the resultant force calculated by the finite number of grids of the pile body and the pile body subjected to the contact of the discrete soil body is not greater than 5%, and the speed selection can be considered reasonable; the appropriate top surface loading speed should ensure that the resultant force of all contact forces is consistent with the unbalanced force of the top surface grid points, and the error cannot exceed 2MN on the prototype scale; the schematic diagram of step D and the final simulation effect are as shown in FIG. Figure 8 As shown:

[0159] When generating the foundation function for a meshed monopile model above the foundation, the following steps are involved:

[0160] 1. Input the initial guess value of gravity, friction and rolling resistance friction, and the function will automatically generate the initial foundation;

[0161] 2. Automatically adjust the gravity value to 0g, and then automatically calculate the porosity under the estimated gravity value and the rate of change of porosity under 0g conditions;

[0162] 3. If the change rate is within 3%, the program considers the guessed value reasonable and you can proceed to the next step or return to re-enter the guessed value and continue to try a higher gravity value;

[0163] 4. After the gravity value is determined, the program continues to run (at this time the program has already used a certain gravity value entered), and now enter the estimated values ​​of friction and rolling resistance friction;

[0164] 5. Based on the two guessed friction values ​​input, the program generates the foundation;

[0165] 6. Automatically calculate whether the porosity under this friction guess value is slightly greater than the specified porosity; (not exceeding 5% of the specified porosity); if not, the program returns to (step 4) to re-enter the two friction guess values;

[0166] 7. After determining the estimated friction value, the program automatically controls the 6 surfaces to servo-pressurize the sample. If the porosity after the servo is stabilized is equal to the specified porosity, the program exits and outputs the friction value; if it is not satisfied, return to step 4, re-enter the estimated value, and try again until a reasonable friction value is found.

[0167] Step E: Fig. 9 As shown, all data are exported and processed and analyzed according to the similarity law of centrifugal simulation: the relevant data are obtained using the DEM-FDM (discrete element-finite difference method) solver; the present invention is equipped with a method for processing data based on Python, which can easily obtain the final result and obtain the horizontal bearing capacity. On the basis of obtaining the horizontal bearing capacity, the soil pressure on the pile body at different depths can also be obtained (both the inner and outer surfaces of the pile body can be calculated); the bending moment borne by the pile body at different depths; the deformation of the pile body at different depths; the soil displacement field and stress field during the pile pushing process, etc. Part of the final processed results are shown in Fig.10 :

[0168] Figure 6A schematic diagram of a calculation example of the present invention is shown. The present invention has developed a DEM-FDM (discrete element-finite difference method) simulation test method for monotonic horizontal loading of a large-diameter single pile, which uses digital centrifuge simulation technology to reveal the evolution law of soil pressure around a large-diameter single pile under horizontal loading and the displacement field, velocity field, and stress field change pattern of the soil around the pile from a microscopic perspective under a hypergravity field. This simulation method is not only applicable to large-diameter single piles of offshore wind turbines, but also to various types of single pile foundations, such as building single pile foundations, onshore wind turbine single pile foundations, and so on. In simulation, the discrete element method can intuitively display the stress field and strain field of the soil under different working conditions, and simulate the mutual movement between particles with real physical relationships under microscopic conditions, providing a basis for theoretical progress.

[0169] As can be seen from the above, the present application provides a method for calculating the horizontal bearing capacity of a single pile of an offshore wind turbine. Through the embodiments of the present application, any of the above methods for calculating the horizontal bearing capacity of a single pile of an offshore wind turbine can be implemented. In the several embodiments provided in the present application, it should be understood that the provided methods and devices can be implemented in other ways. For example, the system embodiments described above are only schematic; for example, the division of a component is only a logical function division, and there may be other division methods in actual implementation, such as multiple components can be combined or integrated into another system, or some features can be ignored or not executed.

[0170] The embodiment of the present application also discloses a computer device.

[0171] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the above-mentioned non-performing asset valuation method is implemented.

[0172] The embodiment of the present application also discloses a computer-readable storage medium.

[0173] A computer-readable storage medium stores a computer program that can be loaded by a processor and execute any of the above-mentioned non-performing asset valuation methods.

[0174] Among them, computer-readable storage media can be any tangible medium that contains or stores a program, which can be used by or in conjunction with an instruction execution system, apparatus or device; the program code contained on the computer-readable medium can be transmitted using any appropriate medium, including but not limited to wireless, wire, optical cable, RF, etc., or any suitable combination of the above.

[0175] It should be noted that in the above embodiments, the description of each embodiment has different emphases, and for parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0176] The above are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Any feature disclosed in this specification (including the abstract and drawings), unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes. That is, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

Claims

1. A method for calculating the horizontal bearing capacity of a single offshore wind turbine pile, characterized in that: The following steps are involved: A. Use discrete element method to calibrate soil particle microscopic parameters; B. The friction and rolling friction based on the microscopic parameters of soil particles are used to generate the foundation using the sand rain method in a hypergravity environment; C uses the finite difference method to generate a single pile grid and penetrates it into the soil; D. applying a monotonic horizontal load to the top surface of the single pile to obtain contact information of the pile body, wherein the contact information of the pile body includes contact coordinates, contact-connected particles and pile body unit information, magnitudes and directions of all contact forces on each contact, and coordinate positions of each node of the pile body; E. Derive the contact information of the pile body contact and process and analyze the data according to the similarity law of centrifugal simulation.

2. The method for calculating the horizontal bearing capacity of a single pile of an offshore wind turbine according to claim 1, characterized in that: In step A, the contact model between particles uses a nonlinear loading contact model. The nonlinear loading contact model is established and verified using particle experiments. The force-displacement relationship between the contacts can be generally expressed by the formula: F t =F l +F d , M c =M r The calculation of forces between particles includes normal force, tangential force, rotational resistance, and damping force, among which: The formula for calculating the normal force is: Among them: F l is the nonlinear contact force, F d is the viscosity, M r is the rotational resisting bending moment; It can be expressed as follows: In the formula, is the normal contact force in the contact model, is the normal vector of the contact surface between contacts, is the tangential contact force in the contact model; The relationship between k1 and k2 is given by the following formula: Among them, k1 represents the initial stiffness of the loading section, k2 represents the initial stiffness of the unloading section, and λ p is the plasticity ratio. When the plasticity ratio is close to 0, the model will not show plastic response. Let λ p =0.01, it is considered that k1=k2 is basically equal to k2; The calculation formula of k1 is as follows: In the formula, E * is the effective Young's modulus between contacts, and R1, R2 are the radii of the two contact objects. If one of the contact objects is a wall unit, then R P is the radius of the contact particle; In the nonlinear loading model, the normal contact displacement between particles is recorded in real time. The model stores and remembers the maximum normal displacement value δ of the relative motion between each particle. max , in the k2 unloading section, δ max =δ n , that is, when calculating the k2 unloading section, the maximum displacement during the last loading will be recorded, so that the unloading starts from the maximum displacement; Effective Young's modulus E between contacts * Calculate as follows: In the formula, the superscripts (1) and (2) represent the Poisson's ratio and shear modulus of the two contacting objects, respectively; The calculation formula of tangential force is: Tangential Contact Force in Contact Models It can be updated with: In the formula, is the tangential contact force at the beginning of each time step, Δδ s is the relative tangential displacement increment, and the tangential stiffness is the normal displacement δ n Function: G * is the effective tangent modulus and k sf Is the scaling factor, the default scaling factor k sf =1; The calculated upper and lower limits are shown in the formula: The calculation formula for rotation resistance is: Rotational resistance moment M in contact model c It can be updated with: In the formula is the rotational stiffness, Δθ b is the relative rotation angle between the contact surfaces; the rotational stiffness is defined as: The upper and lower limits of the rotational resistance moment are specified as: The damping force is calculated as: The damping force consists of two parts: normal force and tangential force: In the normal direction: In the formula, is the effective contact mass between two contacting particles, is the normal translational velocity, and β n is the normal damping coefficient; The damping force in the tangential direction is given by: In the formula, is the normal translational velocity, β s is the normal damping coefficient between contacts; s represents the contact state, and s=false represents the contact state without sliding; M d Indicates the selection of damping force mode, M d =0 means the damping force mode is no cut-off mode, M d =1 means contact cut-off when tangential sliding occurs, and the tangential damping force becomes 0 at this time.

3. The method for calculating the horizontal bearing capacity of a single pile of an offshore wind turbine according to claim 2, characterized in that: The method for generating a foundation by using the sand rain method under the hypergravity environment comprises: Under the hypergravity field, the falling sand method was used to generate a foundation model with a set porosity, the gravity value was reduced to 0g, and the gravity field with a variation range of foundation porosity less than 3% was screened; In a hypergravity field, non-overlapping particles are generated within a fixed height, and this process is repeated by free falling from a fixed height to generate an initial sample; The initial sample weight is reduced to 0g, and the porosity screening is performed to obtain a sample whose foundation porosity is greater than the porosity of the final sample to obtain a secondary sample; Under the condition of zero gravity, a confining pressure of less than 5 kPa is applied to the secondary sample to generate a uniform force chain.

4. The method for calculating the horizontal bearing capacity of a single pile of an offshore wind turbine according to claim 1, characterized in that: A single pile model with grids divided is generated above the foundation, and a constant speed of 0.2-0.5 m / s is applied to the top surface of the single pile.

5. The method for calculating the horizontal bearing capacity of a single pile of an offshore wind turbine according to claim 1, characterized in that: In the process of pushing the pile with a monotonic horizontal load applied to the top surface of the single pile, the difference between the resultant force calculated by the finite grids of the pile body and the pile body subjected to the contact of discrete soil bodies is no more than 5%.

6. A computer-readable storage medium, characterized in that: The computer-readable storage medium comprises a computer program for implementing the method according to any one of claims 1 to 5.

7. A computing device, characterized in that The computing device comprises a memory and a processor, wherein the memory is used to store a computer program, and when the computer program is executed by the processor, the method according to any one of claims 1 to 5 is implemented.

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