A calculation method for the horizontal bearing capacity of a monopile of an offshore wind turbine

Abstract

This application discloses a method for calculating the horizontal bearing capacity of a single offshore wind turbine pile, comprising calibrating the microscopic parameters of soil particles using the discrete element method; generating a foundation using the sand-rain method in a hypergravity environment based on the friction and rolling friction of the soil particles' microscopic parameters; generating a single pile grid using the finite difference method and penetrating the soil; applying a monotonic horizontal load to the top surface of the single pile; and deriving all data and processing and analyzing the data based on the similarity law of centrifugal simulation. The present invention simulates the microscopic foundation soil preparation process based on the foundation preparation process of a real physical experimental test by using the sand-rain method in a hypergravity field to generate a foundation with a porosity that meets specified requirements and a uniform force chain.

Description

Technical Field

[0001] The present application relates to the technical field of calculating the horizontal bearing capacity of a single offshore wind turbine pile, and in particular to a method for calculating the horizontal bearing capacity of a single offshore wind turbine pile. 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 single pile failure mode, the pile side soil pressure distribution pattern 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 a single pile 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 (DEM) is a numerical simulation method specifically designed to solve problems involving discontinuous media. This method treats soil particles as composed of discrete spheres, which are allowed to translate and rotate. Therefore, soil is considered a discontinuous, discrete medium. Large displacements, rotations, and sliding can occur within it, allowing for a realistic simulation of the nonlinear large deformation characteristics of cleaved soils. The general DEM solution process is as follows: the solution space is discretized into a matrix of discrete element units, and adjacent units are connected using appropriate release relationships based on the actual problem. The relative displacement between units is the fundamental variable, and the relationship between force and relative displacement yields the normal and tangential forces between the two units. The resultant forces and torques acting on the units in all directions, as well as the external forces caused by other physical fields acting on the units, are calculated. Newton's second law of motion is used to determine the unit acceleration. This is then integrated over time to obtain the unit velocity and displacement. This yields physical quantities such as velocity, acceleration, angular velocity, linear displacement, and rotation angle for all units at any given moment.

[0004] A current challenge in the industry is that the microscopic simulation methods provided by the discrete element method (DEM) are difficult to relate to the macroscopic model. The DEM can discretize soil into discrete spherical particles, but if the DEM is used directly to simulate actual projects, the number of simulated particles could reach trillions, and current computer performance cannot meet this level of computation. The industry's use of the DEM is generally limited to small unit tests, and few people use it to simulate large-scale projects.

[0005] The existing technology uses the finite element method or finite difference method for analysis. There are relatively few studies on offshore wind turbine pile foundations at the microscopic level. Among them, YuPeng et al. (2023) also used the DEM-FDM (discrete element-finite difference method coupling) method to calibrate soil parameters by directly comparing centrifuge test results and to carry out a series of suction tube foundation simulations under different working conditions such as torsion and horizontal loading. The technical problems with this solution are: it 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 offshore wind turbine pile.

[0007] In a first aspect, the present application provides a method for calculating the horizontal bearing capacity of a single offshore wind turbine pile, using 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 foundation is generated by the sand rain method under hypergravity environment based on the friction and rolling friction of soil particles microscopic parameters;

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

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

[0013] E. Deriving the contact information of the pile body and processing the data according to the similarity law of the centrifugal simulation and analyzing it.

[0014] Furthermore, 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:

[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, and Mr is the rotational resistance bending moment;

[0019] It can be expressed as follows:

[0020]

[0021] Where, 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] The relationship between k1 and k2 is given by the following formula:

[0023]

[0024] Where 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 and k2 are basically equal;

[0025] The calculation formula of k1 is as follows:

[0026]

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

[0028]

[0029] R1, R2 are the radii of the two contact objects. If one of the contact objects is a wall element, 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 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 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 forces in contact models It can be updated using the following formula:

[0035]

[0036] Where, 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 rotational resistance is:

[0042] Rotational resistance moment M in contact model c It can be updated using the following formula:

[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 follows:

[0047]

[0048] The calculation formula of damping force is:

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

[0050]

[0051] In the normal direction:

[0052]

[0053] Where, 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 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 at a fixed height, and this process is repeated by free falling from a fixed height to generate an initial sample;

[0059] The initial sample gravity is reduced to 0g, and the porosity screening is performed to obtain a secondary sample whose foundation porosity is greater than the porosity of the final 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 gridded single pile model 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.

[0062] Furthermore, during the pushing process of the single pile with a monotonic horizontal load applied to the top surface, the difference between the resultant forces 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 that 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 according to 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 capable of being loaded by a processor and executing any one of the methods in the first aspect.

[0067] In summary, this 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, 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 projects 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 the foundation by the sand rain method under the hypergravity 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) From a microscopic perspective, the present invention can directly gain insight into the soil displacement field, stress field, and velocity field that are difficult to monitor in reality, providing a basis for the advancement of related theories; BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 Schematic diagram of the flow 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 Schematic diagram of the falling sand method under a high gravity field of the present invention;

[0073] in Figure 2 (a) Flowchart 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 the 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 This is a flow chart for confirming the hypergravity field G in an embodiment of the present invention;

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

[0080] Figure 6 A schematic diagram of a calculation example in an embodiment 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] Figure 9 This is the final effect diagram of step D in the embodiment of the present invention;

[0084] Figure 10 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 solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0086] The present application discloses a method for calculating the horizontal bearing capacity of a single offshore wind turbine pile, 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 includes: 1. soil particles simulated by discrete element method to form a foundation; 2. a single pile continuum simulated by 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 calculate the horizontal bearing capacity of the foundation more accurately. 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 method of the present invention is a secondary development 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 the soil;

[0094] D. Select an appropriate rate to apply a monotonic horizontal load to the top surface of the 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 the figure below. Figure 4 If the axial strain-stress curve obtained from the triaxial test is consistent with the curve obtained from the test (the error is generally not greater than 10%, such as Figure 2 It is considered 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 sample preparation process, the present invention adopts an innovative sand rain method under a high gravity field to prepare the sample. The flow chart of the method for preparing the foundation under a high 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, and the difference from the specified porosity is too large, making it 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 high gravity 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 from a fixed height under the action of gravity. This process is repeated continuously to generate the initial sample. The generation process is as follows: Figure 2 (b)

[0100] 3. Reduce gravity to 0g and observe the porosity of the sample after it has fallen. The porosity of the resulting foundation should be slightly greater than that of the final sample, as the confining pressure applied in step 4 will reduce the porosity somewhat. This should allow for a margin. There are two main particle parameters that control porosity: friction and rolling resistance friction. Higher friction results in a looser sample, meaning a higher porosity, and vice versa. If the resulting foundation porosity 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 5kPa 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 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 Equation 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 viscous force, M r is the rotational resisting bending moment.

[0110]

[0111] Where, 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] k1 represents the initial stiffness of the loaded section, and k2 represents the initial stiffness of the unloaded section. The relationship between k1 and k2 is given by Equation 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. In the nonlinear loading contact model mentioned in this invention, let λ p =0.01, it is considered that k1=k2 and k2 are basically equal.

[0116] The calculation formula of k1 is as follows:

[0117]

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

[0119]

[0120] R1, R2 are the radii of the two contact objects. If one of the contact objects is a wall element, 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 , which will be used in the k2 unloading section. The model stipulates that in the k2 unloading section in Equation 1.3, δ max =δ n , that is, when calculating the k2 unloading section, the maximum displacement during the last loading will be recorded, so that unloading starts from the maximum displacement.

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

[0123]

[0124] Where, 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 formula (1.2), the tangential contact force in the contact model is It can be updated using the following formula:

[0127]

[0128] Where, 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 torque M in the contact model is c It can be updated using the following formula:

[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 follows:

[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] Where, 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 of the nonlinear loading model between particles and the particle test are shown in the figure. 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] Digital centrifuge simulation technology, based on the principles of centrifuge testing, applies similarity ratios of physical quantities in centrifuge testing to discrete element and finite difference simulations. Geotechnical centrifuge testing utilizes the centrifugal force provided by a centrifuge to simulate gravity. Using similarity criteria, the prototype geometry is scaled down and a model is constructed using soil with the same physical properties. This ensures that the stress state in the centrifugal field is consistent with that of the prototype in the gravitational field. This allows for the study of engineering properties.

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

[0152] Table 1 Similarity criteria for commonly used physical quantities under the condition that the 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 100g conditions, 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 a gravity condition of 1g, the number of simulated sand particles will reach trillions, and the current computer performance does not support simulation calculations of this order of magnitude. Therefore, with reference 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, 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. This 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 centrifugal simulation technology, it is necessary to determine a suitable 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 centrifugal 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 hypergravity 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 in the present invention can automatically calculate the number of particles required for a specified porosity ratio, and realize automatic falling and automatic sampling. This step can be completed using the foundation generation function in the present invention. The schematic diagram of the sand rain method and the generation effect diagram are shown in the figure below. 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 allow the pile to 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 process diagram of step C 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 body 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 calculation of the next step. After replacing the parameters, the calculation of the mechanical properties of the pile-soil interaction can be carried out; a suitable rate is selected, and a constant speed to the right is given to the top of the pile to simulate the process of horizontal loading of the pile (the selection of the speed should be based on the calculation efficiency. 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 under the action of discrete soil is no more 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 shown in FIG. Figure 8 As shown:

[0159] Generating a foundation function for a meshed monopile model above the foundation involves the following steps:

[0160] 1. Input the initial guess value of gravity and the guess value of 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 guess to be reasonable and you can proceed to the next step or return to re-enter the guess and continue to try a higher gravity value.

[0163] 4. After determining the gravity value, the program continues running (at this point the program has already used the input gravity value), and now enter the estimated values of friction and rolling resistance friction;

[0164] 5. Based on the two guessed friction values entered, 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) and re-enters the two friction guess values.

[0166] 7. After determining the estimated friction value, the program automatically controls the six surfaces to servo-pressurize the sample. If the porosity after servo stabilization is equal to the specified porosity, the program exits and outputs the friction value. If not, return to step 4, re-enter the estimated value, and repeat trial and error until a reasonable friction value is found.

[0167] Step E: Figure 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 Figure 10 :

[0168] Figure 6A schematic diagram of a calculation example of the present invention is shown. The present invention develops a DEM-FDM (discrete element-finite difference method) simulation test method for large-diameter single piles subjected to monotonic horizontal loading. By using digital centrifugal simulation technology, the evolution law of soil pressure around large-diameter single piles subjected to horizontal loading and the displacement field, velocity field, and stress field variation pattern of the soil around the pile can be revealed from a microscopic perspective under a hypergravity field. This simulation method is not only applicable to large-diameter single piles for 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 offshore wind turbine pile. Through the embodiments of the present application, any of the above methods for calculating the horizontal bearing capacity of a single offshore wind turbine pile 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 merely illustrative; for example, the division of a certain 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 one 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 that can be used by or in combination 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. 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 scope of protection of this application. Unless otherwise stated, any feature disclosed in this specification (including the abstract and drawings) may be replaced by other equivalent or similar features. In other words, unless otherwise stated, each feature is merely 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 foundation is generated by the sand rain method under hypergravity environment based on the friction and rolling friction of soil particles microscopic parameters; C uses the finite difference method to generate a single pile grid and penetrates the soil; D. applying a monotonic horizontal load to the top surface of a single pile to obtain contact information of the pile body, wherein the contact information of the pile body includes contact coordinates, information of particles and pile body units connected by contact, magnitudes and directions of all contact forces on each contact, and coordinates of each node of the pile body; E. deriving contact information of the pile body and processing and analyzing the data according to the similarity law of centrifugal simulation; In step A, the contact model between particles uses a novel 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 viscous force, M r is the rotational resisting bending moment; It can be expressed as follows: Where, 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: Where 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 and k2 are basically equal; The calculation formula of k1 is as follows: Where, 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 wal l element, 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 unloading starts from the maximum displacement; Effective Young's modulus E between contacts * Calculate as follows: In the formula, superscripts (1) and (2) represent the Poisson's ratio and shear modulus of the two contacting objects, respectively; The calculation formula for tangential force is: Tangential contact forces in contact models It can be updated using the following formula: Where, is the tangential contact force at the beginning of each time step, δ 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 rotational resistance is: Rotational resistance moment M in contact model c It can be updated using the following formula: In the formula is the rotational stiffness, θ 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 follows: The calculation formula of damping force is: The damping force consists of two parts: normal force and tangential force: In the normal direction: Where, 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: Where, 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; The method for generating a foundation by using the sand rain method under a 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 at a fixed height, and this process is repeated by free falling from a fixed height to generate an initial sample; The initial sample gravity is reduced to 0g, and the porosity screening is performed to obtain a secondary sample whose foundation porosity is greater than the porosity of the final 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.

2. The method for calculating the horizontal bearing capacity of a single offshore wind turbine pile according to claim 1, wherein: A single pile model with mesh division is generated above the foundation, and a constant velocity of 2-5 m / s is applied to the top surface of the single pile.

3. The method for calculating the horizontal bearing capacity of a single offshore wind turbine pile according to claim 1, wherein: During the pile pushing process when a monotonic horizontal load is 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 action of discrete soil is no more than 10%.

4. 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 3.

5. A computing device, characterized in that The computing device includes 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 3 is implemented.

Images