A simulation and calculation method for seismic dynamic response of a three-barrel foundation of an offshore wind turbine in sandy soil layers

Abstract

The present invention discloses a method for simulating and calculating the seismic dynamic response of a three-barrel foundation of an offshore wind turbine in sandy soil layers, which relates to the technical field of testing the dynamic response of offshore wind turbine structures. The method includes obtaining construction data, preprocessing the construction data to generate an initial data set, establishing a three-dimensional digital model of the soil body for initial in-situ stress balance to obtain an initial in-situ stress field, setting the three-dimensional digital model of the soil body to the SANISAND constitutive model, introducing the initial in-situ stress field to obtain the soil body model after secondary balance, introducing the wind turbine model to establish a three-dimensional digital model of the three-barrel foundation of the offshore wind turbine, setting the contact surface parameters, and performing final balance to obtain an initial stress response model. An environmental load is input from the upper part, a seismic wave is input from the bottom, a free-field boundary is set, output commands are written for the obtained model for post-processing, and a dynamic analysis of the three-barrel foundation of the offshore wind turbine is carried out. The present invention can accurately and efficiently calculate the seismic dynamic response of the three-barrel foundation of an offshore wind turbine in sandy soil foundation.

Description

Technical Field

[0001] The present invention relates to the technical field of structural dynamic response testing of offshore wind turbines, and particularly relates to a method for simulating and calculating the seismic dynamic response of a tripod foundation of an offshore wind turbine in sandy soil layers. Background Art

[0002] In recent years, suction bucket foundations of offshore wind turbines have been favored by the industry due to their advantages such as low cost and convenient installation. Suction bucket foundations are divided into single bucket foundations and multi-bucket foundations. Multi-bucket foundations have a higher anti-overturning bearing capacity, which makes them more suitable for installation in deep water (25 - 50 m) to support offshore wind turbines. In addition to being subjected to environmental loads such as wind and waves for a long time, the offshore wind turbine system is also threatened by seismic loads. During the operation of the wind turbine system, it must meet the requirements of the serviceability limit state (SLS) that dominates its foundation design.

[0003] Different from single bucket foundations, multi-bucket foundations resist overturning moments through the vertical compression - extraction behavior of individual buckets. Many offshore wind turbines at home and abroad are installed in earthquake-prone areas. Under the action of strong earthquakes, sandy soil foundations are prone to liquefaction, resulting in excessive settlement or rotational displacement of the offshore wind turbine foundations installed in sandy soil, affecting the normal operation of the upper wind turbine structure, and even leading to the overall overturning failure of the wind turbine.

[0004] How to effectively calculate the seismic dynamic response of a tripod foundation of an offshore wind turbine in sandy soil, including the displacement, rotation of the tripod foundation under seismic action, and the liquefaction situation of the soil around the foundation, etc., is crucial for the seismic design of the tripod foundation of an offshore wind turbine.

[0005] Therefore, proposing a method for simulating and calculating the seismic dynamic response of a tripod foundation of an offshore wind turbine in sandy soil layers to solve the problem that the seismic dynamic response of a tripod foundation of an offshore wind turbine in sandy soil cannot be calculated in the prior art is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a method for simulating and calculating the seismic dynamic response of a tripod foundation of an offshore wind turbine in sandy soil layers, which can accurately and efficiently calculate the seismic dynamic response of a tripod foundation of an offshore wind turbine in sandy soil.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for simulating and calculating the seismic dynamic response of a tripod foundation of an offshore wind turbine in sandy soil layers includes the following steps:

[0009] Data acquisition step: acquiring construction data and preprocessing the construction data to generate an initial data set;

[0010] Model building steps: Establish a wind turbine model and a three-dimensional digital soil model using the initial dataset, and perform initial in-situ stress balancing to obtain the initial in-situ stress field;

[0011] Soil setting steps: Set the three-dimensional digital soil model to the SANISAND constitutive model, introduce the initial in-situ stress field into the SANISAND constitutive model for secondary balancing, and obtain the soil model after secondary balancing;

[0012] Model generation steps: Introduce the wind turbine model into the soil model after secondary balancing, establish a three-dimensional digital model of the three-bar foundation of the offshore wind turbine, set the contact surface parameters, and perform final balancing to obtain the initial stress response model;

[0013] Loading steps: Input wind and wave environmental loads to the upper part of the initial stress response model, input seismic waves to the bottom, and set the free field boundary to obtain the set stress response model;

[0014] Output analysis steps: Write output commands for post-processing and perform dynamic analysis of the three-bar foundation of the offshore wind turbine.

[0015] For the above method, optionally, in the data acquisition step, data preprocessing includes adjusting and calibrating parameters using triaxial tests combined with construction data.

[0016] For the above method, optionally, in the model building step, use a linear elastic model to perform initial in-situ stress balancing on the three-dimensional digital soil model.

[0017] For the above method, optionally, after each in-situ stress balancing is completed, set the initial displacement and velocity of the element nodes to 0.

[0018] For the above method, optionally, in the model generation step, the part where the wind turbine model contacts the soil model after secondary balancing is used as the contact surface, and the parameters defined for the contact surface include normal stiffness and shear stiffness. The normal stiffness k n and the shear stiffness k s are expressed as follows:

[0019]

[0020] where k n is the normal stiffness, k s is the shear stiffness, K is the bulk modulus, G is the shear modulus, and Δz min is the minimum size of the mesh in the normal connection area of the contact surface.

[0021] For the above method, optionally, in the loading step, perform filtering and baseline correction processing on the seismic waves.

[0022] As can be seen from the above technical solutions, compared with the prior art, the present invention provides a method for simulating and calculating the seismic dynamic response of a three-barrel foundation of an offshore wind turbine in sandy soil layers, which can accurately analyze the displacement, stress of the three-barrel foundation of the offshore wind turbine and the liquefaction situation of the soil around the foundation, achieving the purpose of saving calculation time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0024] Figure 1 It is a flow chart of a method for simulating and calculating the seismic dynamic response of a three-barrel foundation of an offshore wind turbine in sandy soil layers disclosed by the present invention;

[0025] Figure 2 It is a three-dimensional digital model diagram of the three-barrel foundation of the offshore wind turbine disclosed by the present invention;

[0026] Figure 3 It is a diagram of the vertical effective stress of the soil after the initial in-situ stress balance disclosed by the present invention;

[0027] Figure 4 It is a cross-sectional view of the barrel-soil contact surface disclosed by the present invention;

[0028] Figure 5a It is a time history diagram of the simulated random wind load disclosed by the embodiment of the present invention;

[0029] Figure 5b It is a time history diagram of the simulated random wave load disclosed by the embodiment of the present invention;

[0030] Figure 6a It is a cloud diagram of the pore pressure cross-section at the position of the right barrel in the three-barrel foundation disclosed by the embodiment of the present invention;

[0031] Figure 6b It is a cloud diagram of the pore pressure cross-section at the position of the left barrel in the three-barrel foundation disclosed by the embodiment of the present invention;

[0032] Figure 7a It is a cloud diagram of the displacement cross-section at the position of the right barrel in the three-barrel foundation disclosed by the embodiment of the present invention;

[0033] Figure 7b It is a cloud diagram of the displacement cross-section at the position of the left barrel in the three-barrel foundation disclosed by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] In this application, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. The terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or device including the element.

[0036] Referring to Figure 1 As shown, the present invention discloses a method for simulating and calculating the seismic dynamic response of a three-barrel foundation of an offshore wind turbine in sandy soil layers, including the following steps:

[0037] Data acquisition step: Acquire construction data and preprocess the construction data to generate an initial data set;

[0038] Model construction step: Use the initial data set to establish a wind turbine model and a three-dimensional digital model of the soil body, and perform an initial in-situ stress balance to obtain an initial in-situ stress field;

[0039] Soil body setting step: Set the three-dimensional digital model of the soil body to the SANISAND constitutive model, introduce the initial in-situ stress field into the SANISAND constitutive model for secondary balance, and obtain a soil body model after secondary balance;

[0040] Model generation step: Introduce the wind turbine model into the soil body model after secondary balance, establish a three-dimensional digital model of the three-barrel foundation of the offshore wind turbine, set the contact surface parameters, and perform a final balance to obtain an initial stress response model;

[0041] Load application step: Input wind and wave environmental loads to the upper part of the initial stress response model, input seismic waves to the bottom, and set the free field boundary to obtain a set stress response model;

[0042] Output analysis step: Compile output commands for post-processing and perform dynamic analysis of the three-barrel foundation of the offshore wind turbine.

[0043] Further, in the data acquisition step, data preprocessing includes adjusting and calibrating parameters by combining triaxial tests with construction data.

[0044] Specifically, the soil from the actual construction site is taken for monotonic / cyclic drained / undrained triaxial tests, which are combined with numerical simulations of triaxial tests to adjust and calibrate the parameters of the SANISAND constitutive model, and to determine the dimensions and material parameters of the offshore wind turbine, etc.

[0045] Further, in the data acquisition step, the initial data set includes SANISAND constitutive model parameters, model dimensions, model material parameters, etc.

[0046] Further, in the model construction step, since it is difficult to establish a three-dimensional digital model in FLAC 3D, software such as ABAQUS and Rhino is used to establish the three-dimensional digital model. As shown in Figure 2 When using the finite element software ABAQUS to model the offshore wind turbine and the soil, the "Tools"-"Sets" function is used to group and name the offshore wind turbine, foundation, and soil parts respectively, and the overall model is meshed. The minimum mesh size is calculated according to the following formula:

[0047]

[0048] where λ is the wavelength corresponding to the maximum frequency, and the models of the soil and the offshore wind turbine are exported as ".inp" files respectively.

[0049] Specifically, when modeling the upper structure of the wind turbine, the wind turbine tower needs to be segmented and cut at the positions where environmental loads such as wind and waves are applied.

[0050] Further, the ".inp" format file is imported into FLAC 3D, and the linear elastic model is used to perform the initial in-situ stress balance on the three-dimensional digital model of the soil.

[0051] Specifically, the parameters used in the linear elastic model are kept consistent with those used in the SANISAND constitutive model.

[0052] Further, for the initial in-situ stress balance, the corresponding initial pore water pressure is set according to the required sea level height, and the corresponding force is applied to the ground to simulate the gravity of the seawater. The specific method is as follows: First, the soil part is imported into the FLAC 3D software, the "elastic" constitutive model is assigned to the soil, and the corresponding soil parameters are set; the water depth is determined, the "isotropic" constitutive model is assigned to the seawater, the fluid density is set to 1, and the initial pore water pressure field is set; the boundary conditions are set, the horizontal displacements of the four boundaries of the model are fixed, and the vertical displacement of the bottom of the model is fixed; finally, gravity is applied to the model, the equilibrium conditions are set, and the equilibrium calculation is performed to obtain the equilibrium result asFigure 3 as shown

[0053] Further, after each in-situ stress balance is completed, set the initial displacements and velocities of the element nodes to 0.

[0054] Further, in the soil setting step, clear the displacements and velocities generated by the initial in-situ stress balance, set the soil to the "dafalias" constitutive model, i.e., the SANISAND constitutive model, and assign corresponding soil parameters to the soil. Define the initial stress field through the following commands:

[0055]

[0056] Apply the initial in-situ stress to the soil. After setting, select appropriate equilibrium conditions for secondary equilibrium.

[0057] Further, in the model generation step, the part where the wind turbine model contacts the soil model after secondary equilibrium is used as the contact surface. Define the parameters of the contact surface including the normal stiffness and shear stiffness. The normal stiffness k n and the shear stiffness k s The expressions are as follows:

[0058]

[0059] where k n is the normal stiffness, k s is the shear stiffness, K is the bulk modulus, G is the shear modulus, and Δz min is the minimum size of the mesh in the normal connection area of the contact surface.

[0060] Specifically, as Figure 4 shown, clear the displacements and velocities generated during secondary equilibrium, import the offshore wind turbine model into FLAC 3D, delete the part where the soil overlaps with the offshore wind turbine foundation, move the wind turbine and foundation parts upward, use the "zoneface skin" command to perform surface meshing on the model to obtain the contact surface. Since no operations are performed on the upper structure, for better display, only the half model of the foundation, soil, and bucket-soil contact surface is shown here. During calculation, the values of K and G are both taken as the larger stiffness value of the elements adjacent to the contact surface; set the contact surface as an impermeable boundary, use the "attach" command to connect at the segmented positions of the wind turbine. This connection method will treat different segments as the same object, move the offshore wind turbine downward to the correct position, and perform the final stress balance.

[0061] Further, in the load application step, refer to Figure 5a and Figure 5bAs shown, appropriate wind and wave loads are selected. The free-field boundary is opened, and the corresponding damping is input. Here, local damping or Rayleigh damping can be selected. The seismic wave is filtered and baseline corrected. The filtering and baseline correction can be performed through software such as OriginPro and SeismoSignal, or the FISH function FFT.fis provided by FLAC 3D can be used. The filtering operation is to filter out the high-frequency part in the seismic wave to reduce the influence of high-frequency noise on the numerical simulation results, and by this method, the maximum frequency of the seismic wave is reduced, thereby increasing the minimum grid required for calculation and reducing the number of elements, which can achieve the purpose of saving calculation time. The baseline correction is to add a low-frequency waveform to the original acceleration time history, which can prevent residual displacement and velocity from appearing at the bottom of the model at the end of the dynamic calculation. The seismic wave is loaded to the bottom of the model using the following commands:

[0062] table 'acc-x' import 'SeismicLoad.txt'

[0063] zone gridpoint free velocity-x range position-z a b

[0064] zone face apply acc-x 9.8 table 'acc-x' range position-z a b

[0065] Then, the wind and wave loads are applied to the contact surface established using the "attach" command in the form of uniform loads. The "history interval" command is used to set the historical interval for data recording.

[0066] Furthermore, in the output analysis step, the "history" command is used to output the required data. If parameters not mentioned in the manual are involved, they can be output by writing a fish function. The operation duration is set for dynamic analysis, and the output data is post-processed.

[0067] The implementation results of the present invention are as Figure 6a , Figure 6b , Figure 7a and Figure 7b shown. It is not difficult to conclude that the triple-barrel foundation can improve the liquefaction resistance of the soil, and the pore pressure inside the suction bucket is significantly greater than that outside the suction bucket; the triple-barrel foundation rotates significantly in the positive x-axis direction.

[0068] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for a system or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple. For the relevant parts, reference can be made to the partial description of the method embodiment. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without creative efforts.

[0069] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for simulating and calculating the seismic dynamic response of a three-barrel foundation of an offshore wind turbine in a sand layer, characterized in that: The following steps are involved: Data acquisition step: obtain construction data and preprocess the construction data to generate an initial data set; Model construction steps: Use the initial data set to build a wind turbine model and a three-dimensional soil digital model, perform initial geostress balance, and obtain the initial geostress field; Soil setting steps: Set the three-dimensional digital model of the soil as the SANISAND constitutive model, introduce the initial geostress field into the SANISAND constitutive model for secondary balance, and obtain the soil model after secondary balance; Model generation steps: introduce the wind turbine model into the soil model after secondary balance, establish a three-dimensional digital model of the offshore wind turbine three-barrel foundation, set the contact surface parameters, and perform final balance to obtain the initial stress response model; Load application steps: input wind and wave environmental loads to the upper part of the initial stress response model, input seismic waves to the bottom, and set the free field boundary to obtain the set stress response model; Output analysis steps: Write output commands for post-processing and conduct dynamic analysis of the three-barrel foundation of offshore wind turbines; The construction data refers to the soil data of the actual construction site; Data preprocessing includes adjusting and correcting parameters using triaxial tests combined with construction data.

2. The method for simulating and calculating the seismic dynamic response of a three-barrel foundation of an offshore wind turbine in a sand layer according to claim 1 is characterized in that: In the model building step, the linear elastic model is used to perform initial geostress balance on the three-dimensional digital model of the soil.

3. The method for simulating and calculating the seismic dynamic response of a three-barrel foundation of an offshore wind turbine in a sand layer according to claim 2 is characterized in that: After each ground stress equilibrium is completed, the initial displacement and velocity of the unit node are set to 0.

4. The method for simulating and calculating the seismic dynamic response of a three-barrel foundation of an offshore wind turbine in a sand layer according to claim 1 is characterized in that: In the model generation step, the part where the wind turbine model contacts the soil model after secondary equilibrium is used as the contact surface. The parameters defining the contact surface include normal stiffness and shear stiffness. and shear stiffness The expression is as follows: ， in, is the normal stiffness, is the shear stiffness, K is the bulk modulus, G is the shear modulus, is the minimum size of the mesh on the normal connection area of ​​the contact surface.

5. The method for simulating and calculating the seismic dynamic response of a three-barrel foundation of an offshore wind turbine in a sand layer according to claim 1 is characterized in that: During the load application step, the seismic waves are filtered and baseline corrected.

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