An optimized partitioning method of structure and foundation grid in SSI computation

Abstract

The application belongs to the technical field of building structure, and particularly relates to a method for optimizing and dividing structure and foundation grid in SSI calculation, which comprises the following steps: establishing an overall calculation model of SSI; performing equivalent linearization processing on the one-dimensional horizontal layer of the soil layer of a building site to obtain the characteristics of the soil layer; when the underground structure is a buried structure, establishing a transition soil body to form at least two layers of structures wrapped outside the buried structure; when the underground structure is a pile foundation, in the vertical direction, the entity between the bottom surface of the bearing structure of the pile foundation and the top surface of the bottom plate of the above-ground structure is divided into at least three layers of structures from top to bottom. According to the application, the unit grid of the structure part in the overall calculation model does not need to be divided in accordance with the soil body, the number of nodes in the finite element simulation is greatly reduced, a new software version does not need to be replaced, the calculation result accuracy requirement is met on the basis of the existing calculation software version, the calculation time is significantly reduced, and significant economic benefits are obtained.

Description

Technical Field

[0001] This invention belongs to the field of building structure technology, and in particular relates to an optimized mesh partitioning method for structure and foundation in SSI (soil-structure interaction) calculation. Background Technology

[0002] In numerical simulation calculations of nuclear power plant and nuclear chemical engineering plant structures, it is necessary to establish a finite element mesh for the plant structure. The wave problem in the finite element discrete mesh model is different from the wave problem in the original continuous medium. Waves in the discrete mesh have a propagation frequency cutoff. Waves propagating in the discrete mesh need to meet certain conditions, namely the size of the finite element mesh and the foundation.

[0003] Specifically, the finite element mesh is related to the shear wave velocity of the soil. When the soil is soft and the shear wave velocity is low, the finite element mesh of the soil and structure will be relatively small, increasing the total number of elements and nodes in the soil-structure interaction system. This is especially true in calculations of embedded structures and pile-soil interactions, where the total number of nodes can be enormous, potentially exceeding 100,000. The computation time for finite element numerical simulations increases with the number of nodes, leading to longer computation times and higher demands on computer performance. In some cases, when the number of nodes in the finite element mesh reaches a certain threshold, the computational software may become unable to meet the computational requirements.

[0004] Given the above situation, how to reasonably divide the finite element mesh in the numerical simulation calculation of the plant structure of nuclear power engineering and nuclear chemical engineering has become an urgent technical problem to be solved. Summary of the Invention

[0005] This invention provides an optimized meshing method for structure and foundation grids in SSI calculations, which can effectively solve the above-mentioned problems.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An optimized mesh generation method for structure and foundation grids in SSI calculations, comprising:

[0008] Based on the factory building structure drawings, an overall calculation model of SSI was established, and the above-ground structure was meshed according to the calculation accuracy requirements.

[0009] The soil layers of the building site are subjected to one-dimensional horizontal stratification equivalent linearization to obtain the characteristics of the soil layers.

[0010] For the underground structure in the overall calculation model, when it is a buried structure, the following steps are performed:

[0011] A transition soil body is established at the boundary where the buried structure contacts the soil layer, and the transition soil body is given the same material properties as the equivalent linearized soil layer.

[0012] The transition soil is divided into at least two layers that cover the outside of the buried structure, with the inner layer in contact with the buried structure and the outer layer in contact with the surrounding soil.

[0013] In the vertical direction, the buried structure and the surrounding soil are cut according to the boundary of the actual geological soil layer. The transition soil is divided into grids in each geological soil layer, and the grid density gradually transitions from large to small from the outside to the inside.

[0014] For the underground structure in the overall calculation model, when it is a pile foundation, the following steps are performed:

[0015] In the vertical direction, the pile foundation and the surrounding soil are cut according to the boundary of the actual geological soil layer. The solid between the bottom surface of the bearing structure of the pile foundation and the top surface of the bottom plate of the above-ground structure is divided into at least three layers from top to bottom, and the grid density gradually transitions from small to large from top to bottom.

[0016] Furthermore, the transition soil is divided into two layers that cover the outside of the buried structure.

[0017] Furthermore, in the vertical direction, the outer layer is meshed according to the shear wave velocity of the corresponding geological soil layer, and the inner layer is meshed according to the calculation accuracy requirements.

[0018] Furthermore, in the vertical direction, the maximum cell size of the outer layer is calculated according to the following formula:

[0019] h = V s / 5f max

[0020] In the formula: Vs is the shear wave velocity of the foundation soil layer;

[0021] f max This is the highest frequency of earthquake vibrations.

[0022] Furthermore, in the horizontal direction, the grid size of the transition soil is 1.3 to 1.7 times the grid size in the vertical direction.

[0023] Furthermore, in the vertical direction, the grids of the transition soil are aligned in columns at each height, and the horizontal dimensions of each grid in each column are the same.

[0024] Furthermore, the solid between the bottom surface of the bearing structure of the pile foundation and the top surface of the bottom plate of the above-ground structure is divided into three layers from top to bottom.

[0025] Furthermore, in the vertical direction, each layer of the structure is divided into grids according to the shear wave velocity of the corresponding geological soil layer.

[0026] Furthermore, the top layer is divided according to the structural units of the base plate, and the bottom layer is divided into uneven units with cylindrical pile foundations.

[0027] Furthermore, in the vertical direction, the solid between the bottom surface of the bearing structure of the pile foundation and the top surface of the base plate of the above-ground structure is aligned into columns at each height, and the horizontal dimensions of each grid in each column are the same.

[0028] Furthermore, the overall computational model includes:

[0029] The walls and floors in the factory building structure are simulated using elastic shell elements, the floor slab is simulated using 3D structural solid elements, beams and columns are simulated using 3D elastic beam elements, and equipment with a mass above a set threshold on the concrete structure of the factory building is simulated using structural mass point elements.

[0030] The technical solution of this invention can achieve the following technical effects:

[0031] The optimized meshing method in this invention is an optimized method for finite element meshing in numerical simulation of factory structures. By adopting this meshing method, it is not necessary to divide the unit mesh of the structural part in the overall calculation model to be consistent with the soil, which greatly reduces the number of nodes in the finite element simulation and does not require changing to a new software version. Based on the existing calculation software version, it not only meets the requirements of calculation result accuracy, but also significantly reduces the calculation time, which has significant economic benefits. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A flowchart for optimizing the partitioning method for embedded structures;

[0034] Figure 2 This is a schematic diagram illustrating the optimized partitioning method for embedded structures.

[0035] Figure 3A flowchart for optimizing the partitioning method for pile foundations;

[0036] Figure 4 This is a schematic diagram illustrating the optimized partitioning method for pile foundations.

[0037] Reference numerals in the attached drawings: 1. Above-ground structure; 2. Embedded structure; 3. Inner layer; 4. Outer layer; 5. Pile foundation; 6. Top layer; 7. Middle layer; 8. Bottom layer. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0040] An optimized mesh generation method for structure and foundation grids in SSI calculations, comprising:

[0041] Based on the factory building structure drawings, an overall calculation model of SSI is established, and the above-ground structure is meshed according to the calculation accuracy requirements. The mesh unit is a polygonal unit with a side length of 1 to 2m. In the implementation process, the walls and floors in the factory building structure are often simulated by elastic shell units in the above-ground structure. Quadrilateral units can be used as much as possible for the mesh unit, and a small number of triangular units can be used in the transition area.

[0042] The soil layers of the building site are subjected to one-dimensional horizontal stratification and equivalent linearization to obtain the soil layer characteristics. This step simplifies and simulates the soil layer characteristics of the building site, making structural analysis and vibration response prediction easier. The soil layers of the site are divided into multiple horizontal layers, each with uniform geotechnical properties. This division is based on the actual site's geological data and the variation characteristics of the soil layers; each layer is considered homogeneous and equivalent. In reality, the nonlinear properties of soil layers are often difficult to handle directly. Therefore, linearization is used to simplify the problem. This means that in the equivalent treatment, parameters such as stiffness and damping of the soil layers are assumed to be linear. This approach simplifies the calculation of soil layer response under earthquakes or other external excitations.

[0043] For underground structures in the overall calculation model, when they are buried structures, the following steps are performed:

[0044] A transition soil body is established at the boundary where the buried structure contacts the soil layer, and the transition soil body is given the same material properties as the equivalent linearized soil layer. The transition soil body includes the portion in contact with the sidewall of the buried structure and the portion in contact with the bottom of the buried structure. The transition soil body is divided into at least two layers that cover the outside of the buried structure, with the inner layer in contact with the buried structure and the outer layer in contact with the surrounding soil. In the vertical direction, the buried structure and the surrounding soil are cut according to the boundaries of the actual geological soil layers, such as clay layers, gravelly sand layers, and strongly weathered rock layers. The transition soil body is meshed in each geological soil layer, with the mesh density gradually decreasing from the outside to the inside. In specific implementation, it can be optimized so that in the vertical direction, the outer layer is meshed according to the shear wave velocity of the corresponding geological soil layer, and the inner layer is meshed according to the calculation accuracy requirements.

[0045] For the underground structure in the overall calculation model, when it is a pile foundation, perform the following steps:

[0046] In the vertical direction, the pile foundation and surrounding soil are divided according to the actual geological soil layer boundaries. The solid between the bottom surface of the bearing structure of the pile foundation and the top surface of the base plate of the above-ground structure is divided into at least three layers from top to bottom, and the grid density gradually transitions from small to large from top to bottom, that is, the bottom grid density is the largest and the grid is the smallest. The bearing structure may be a pile cap. In this case, the solid refers to the pile cap and the base plate. In the nuclear power field, since the base plate is often set relatively thick, it may be directly used as the bearing structure. In this case, the solid is only the base plate. As a preferred method, the top part of the above at least three layers is divided according to the structural unit of the base plate, and the bottom part is divided into non-uniform units with cylindrical pile foundations.

[0047] The optimized meshing method in this invention is an optimized method for finite element meshing in numerical simulation of factory structures. By adopting this meshing method, it is not necessary to divide the unit mesh of the structural part in the overall calculation model to be consistent with the soil, which greatly reduces the number of nodes in the finite element simulation and does not require changing to a new software version. Based on the existing calculation software version, it not only meets the requirements of calculation result accuracy, but also significantly reduces the calculation time, which has significant economic benefits.

[0048] The transition soil adopts the same material properties as the equivalent linearized soil layer. This treatment allows the transition soil to better simulate the interaction between the structure and the soil, while ensuring the consistency of the simulation. This includes key properties such as the elastic modulus, shear modulus, and density of the soil. This consistency ensures that there are no inconsistent mechanical properties between the equivalent linearized soil layer and the transition soil in the simulation. Due to the linearization of the soil, the effect of the structure on the soil can be more easily derived in the simulation, and vice versa, thus more accurately predicting the response of the structure under external excitations such as earthquakes.

[0049] The transition soil forms at least two layers covering the outside of the buried structure, ensuring that the transition soil exists in all areas where interaction may occur, thus more comprehensively considering the contact between the structure and the soil. The fine stratification of the transition soil ensures that the simulation more realistically reflects the complex interaction between the soil and the buried structure. Since the sidewalls and bottom of the structure are effectively covered, the simulation results more accurately reflect the soil response around the structure, including key factors such as soil deformation and stress transfer.

[0050] During implementation, the detailed layered design of the transition soil, combined with the soil material properties after equivalent linearization, more accurately captured the details of soil-structure interaction, further improving the accuracy and reliability of the calculation. This made the numerical simulation results closer to the actual scenario and provided a more reliable technical basis for engineering decisions.

[0051] The embedded structure within the transition soil body, and the surrounding soil outside the transition soil body, are cut according to the boundaries of the actual geological soil layers. The transition soil body sandwiched in between, through the difference in grid density between the inner and outer layers, can capture the details of the interaction between the structure and the soil more precisely, especially when there are complex changes or transitions between the structure and the soil. Overall, the above optimization scheme can achieve a comprehensive consideration of computational efficiency and the key areas of interest, improving the accuracy of the simulation while maintaining computational efficiency.

[0052] Specifically, this invention provides a method for meshing transitional soils within geological soil layers. This is because the shear wave velocity of geological soil layers is typically related to the soil's physical properties and density, which can vary significantly in actual sites. Therefore, in the vertical direction, the outer layer is layered according to the shear wave velocity of the corresponding geological soil layer, which better reflects the variations in actual geological conditions. This allows the numerical simulation to more realistically reflect the differences in geological soil layers. By layering according to shear wave velocity, the vertical variations of the geological soil layers can be more accurately characterized, thereby improving the accuracy of the simulation. Since different geological soil layers exhibit significant differences in shear wave velocity, the preferred method described above, by layering according to this difference, introduces layers with different mesh densities into the outer layer of the transitional soil, more accurately reflecting the properties of the soil under different geological conditions. This layered design helps simulate more complex and realistic interactions between underground structures and soil.

[0053] For pile foundations, dividing the solid between the bottom surface of the load-bearing structure and the top surface of the above-ground structure's base slab into at least three layers from top to bottom can improve the accuracy of the simulation. Actual geological conditions may vary significantly in the vertical direction, such as different geological layers and soil types. By dividing the structure according to the boundaries of the actual geological soil layers, the changes in the underground structure can be more realistically reflected. This division method allows for a more precise simulation of the interaction between the structure and the soil. The different layers allow for a more detailed consideration of the complex interactions between the bottom of the structure and the soil, including deformation and stress transfer. A gradually transitioning mesh density design from top to bottom allows for a reasonable distribution of the number of nodes and elements in the simulation based on actual conditions. This design maintains computational efficiency while better focusing on the key areas of structure-soil interaction, thus improving the accuracy of the simulation.

[0054] The interaction between underground structures and the surrounding soil usually occurs at the interface between the structure and the soil. Cutting the pile foundation and the surrounding soil according to the boundary of the actual geological soil layer can more accurately simulate this critical area. Considering the changes in soil properties in the vertical direction can more accurately reflect the complex interaction between the structure and the soil. The physical properties of the soil may vary significantly in the vertical direction, such as density and hardness. Cutting according to the boundary of the actual geological soil layer helps to better capture these changes and improve the realism of the simulation.

[0055] The solid structure between the load-bearing bottom surface and the base plate of the above-ground structure is divided into at least three layers from top to bottom. This layered design takes into account the complexity of deformation and stress transfer at the bottom of the structure. This layered design allows for a more accurate simulation of the interaction between the bottom of the structure and the soil, including key factors such as deformation and stress distribution. The top layer is divided according to the structural units of the base plate, which helps maintain consistency with the above-ground structure. This design can better capture the impact of the deformation at the bottom of the structure on the above-ground structure, ensuring that the simulation results match the actual project. The non-uniform unit division of the bottom layer takes into account the presence of pile foundations and uses a division method with cylindrical pile foundations to more closely resemble the actual situation. This helps to more accurately simulate the complex interaction between the pile foundation and the soil. The gradually transitioning grid density design from top to bottom controls the computational complexity while maintaining simulation accuracy. A larger grid density is used in the bottom layer to capture deformation and stress transfer in greater detail, while the density gradually decreases in the upper layers to improve computational efficiency.

[0056] Specifically, the following examples, with reference to the attached diagrams, illustrate optimized classification methods for embedded structures and pile foundations:

[0057] For buried structures, such as Figure 1 and 2 As shown, the optimized partitioning method includes the following steps:

[0058] S1: Based on the factory building structure drawings, establish the overall calculation model of SSI, and perform mesh division for the above-ground structure 1 according to the calculation accuracy requirements;

[0059] S2: Perform one-dimensional horizontal stratification of the soil layers at the construction site to obtain the characteristics of the soil layers;

[0060] S3: Establish a transition soil body at the boundary where the buried structure 2 contacts the soil layer, and assign the transition soil body the same material properties as the equivalent linearized soil layer.

[0061] S4: Divide the transition soil to form at least two layers covering the outside of the buried structure 2, with the inner layer 3 in contact with the buried structure 2 and the outer layer 4 in contact with the surrounding soil.

[0062] S5: In the vertical direction, the buried structure 2 and the surrounding soil are cut according to the boundary of the actual geological soil layer. The transition soil is divided into grids in each geological soil layer, and the grid density gradually transitions from large to small from the outside to the inside.

[0063] For pile foundations, such as Figure 3 and 4 As shown, the optimized partitioning method includes the following steps:

[0064] A1: Based on the factory building structure drawings, establish the overall calculation model of SSI, and perform mesh division for the above-ground structure 1 according to the calculation accuracy requirements;

[0065] A2: Perform one-dimensional horizontal stratification of the soil layers at the construction site to obtain the characteristics of the soil layers;

[0066] A3: In the vertical direction, the pile foundation 5 and the surrounding soil are cut according to the boundary of the actual geological soil layer. The solid between the bottom surface of the bearing structure of the pile foundation 5 and the top surface of the bottom plate of the above-ground structure 1 is divided into at least three layers from top to bottom. The top layer 6 is divided according to the structural unit of the bottom plate, the bottom layer 8 is divided into uneven units with cylindrical pile foundations, and the rest is the middle layer 7. The grid density gradually transitions from small to large from top to bottom.

[0067] As a preferred embodiment of the above, the transition soil is divided into two layers to form a two-layer structure covering the outside of the buried structure. In this preferred embodiment, the optimal number of layers for the transition soil is determined to be two, which achieves the above-mentioned objectives of the present invention while obtaining optimal computational efficiency.

[0068] Preferably, in the vertical direction, the maximum cell size of the outer layer mesh is calculated according to the following formula:

[0069] h = V s / 5f max

[0070] In the formula: Vs is the shear wave velocity of the foundation soil layer;

[0071] f max This is the highest frequency of earthquake vibration; it is generally taken as 33Hz.

[0072] In this preferred embodiment, by limiting the maximum cell size of the transition soil in the vertical direction—that is, the cell size must be less than or equal to this maximum cell size—sufficient spatial resolution is ensured to capture high-frequency components. This is crucial for simulating high-frequency fluctuations and short-period structural responses. Using a smaller cell size effectively reduces dispersion effects in numerical simulations, ensuring more accurate wave propagation. Dispersion effects are a type of error in numerical simulations, particularly significant when dealing with high-frequency fluctuations. Controlling the maximum cell size reduces this error; a smaller cell size helps to more accurately capture the wave behavior in soil and structural responses, especially at higher vibration frequencies. This is of critical importance for simulations in fields such as earthquake engineering.

[0073] During implementation, although reducing the mesh cell size helps improve the accuracy of the simulation, a balance needs to be struck between computational efficiency and resource consumption. Using V... s / 5f max The formula can be adjusted according to specific engineering needs to meet the requirements of calculation accuracy and efficiency.

[0074] As a preferred embodiment of the above, the grid size of the transition soil in the horizontal direction is 1.3 to 1.7 times that in the vertical direction. Within this range, 1.5 times can be further selected as a preferred implementation. During the simulation calculation, a smaller size in the vertical direction is to more finely simulate the changes of soil and structure in the vertical direction and more accurately capture the interaction details between structure and soil. Underground geological soil layers often exhibit heterogeneity in the vertical direction. By setting a smaller size in the vertical direction, this heterogeneity can be better considered, improving the accuracy of the simulation. In nuclear power engineering, a smaller size in the vertical direction can provide a more accurate numerical solution, ensuring that the simulation results meet the engineering requirements of the actual site. Appropriately increasing the grid size in the horizontal direction, compared to the vertical direction, can reduce the number of grids in the horizontal direction. This helps to reduce the number of nodes and elements in the overall finite element model, thereby reducing the computational cost of numerical simulation and improving computational efficiency. Although the grid size is increased in the horizontal direction, a moderate density is still maintained to ensure the stability of the numerical simulation. Therefore, in this preferred embodiment, maintaining a moderate horizontal grid size by limiting the range can reduce computational costs while maintaining accurate simulation of the horizontal response of the structure.

[0075] As a preferred embodiment of the above embodiments, in the vertical direction, the grids of the transition soil at each height are aligned in columns, with each grid in each column having the same horizontal dimension. In the horizontal direction, the properties of the structure and soil are generally relatively homogeneous, and the horizontal characteristics of the soil and structure may be relatively consistent. Therefore, the grids in the horizontal direction can use the same size to better match the homogeneity of the structure and soil. Seismic waves typically propagate more significantly in the horizontal direction; therefore, the seismic excitation experienced by the soil and structure is relatively uniform in the horizontal direction, and the speed and characteristics of seismic wave propagation vary less in the horizontal direction. Conversely, in the vertical direction, due to the characteristics of seismic wave propagation underground, soil layers at different depths may experience different seismic excitations. Therefore, a more detailed grid is needed to reflect this depth variation. This means that in the vertical direction, the grid size may need to be adjusted according to the characteristics of soil layers at different depths to more accurately simulate the response of soil at different depths to earthquakes.

[0076] For the same reason as selecting two layers for the optimal number of layers in the transition soil, the solid between the bottom surface of the bearing structure of the pile foundation and the top surface of the bottom slab of the above-ground structure is divided into three layers from top to bottom; in the vertical direction, each layer is meshed according to the shear wave velocity of the corresponding geological soil layer, and the maximum element size of the mesh can also be calculated according to the following formula:

[0077] h = V s / 5f max

[0078] In the formula: Vs is the shear wave velocity of the foundation soil layer;

[0079] f max This is the highest frequency of earthquake vibration; it is generally taken as 33Hz.

[0080] As another preferred method, in the vertical direction, the solid between the bottom surface of the bearing structure of the pile foundation and the top surface of the bottom plate of the above-ground structure are aligned into columns at various heights, and the horizontal dimensions of each grid in each column are the same. The effect achieved is as described in the above embodiments, and will not be repeated here.

[0081] During implementation, the overall calculation model includes:

[0082] The walls and floors in the factory building structure are simulated using elastic shell elements, the floor slab is simulated using 3D structural solid elements, beams and columns are simulated using 3D elastic beam elements, and equipment with a mass above a set threshold on the concrete structure of the factory building is simulated using structural mass point elements.

[0083] In the implementation process, the above steps specifically use the ANSYS finite element model. More specifically, the 4-node elastic shell element SHELL181 can be used to simulate the walls and floors in the factory structure; the 3D 8-node structural solid element SOLID45 can be used to simulate the base plate in the factory structure; the 3D elastic beam element BEAM188 can be used to simulate the beams, columns and other components of the factory structure; and the structural mass point element MASS21 can be used to simulate the large-mass equipment on the concrete structure of the factory structure.

[0084] In practice, the following examples illustrate this:

[0085] When the underground structure is a buried structure, transition elements are created using the SOLID45 element, and the surrounding soil is given realistic properties, including density, elastic modulus, and damping ratio. The outer layer of the transition soil has a smaller mesh, while the inner layer has a larger mesh; tetrahedral elements are used when dividing the transition soil into elements.

[0086] When the underground structure is a pile foundation, the solid between the bottom surface of the bearing structure of the pile foundation and the top surface of the bottom plate of the above-ground structure is simulated using the SOLID45 element. The upper part is adjacent to the structure and is divided into a regular hexahedral element mesh according to the accuracy requirements of the structural calculation results. The bottom part is connected to the pile foundation and is divided into a smaller mesh together with the pile foundation according to the shear wave velocity requirements of the soil, which is an irregular tetrahedral element. The middle part is automatically divided into tetrahedral elements.

[0087] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for optimizing the mesh generation of structure and foundation in SSI calculations, characterized in that, include: Based on the factory building structure drawings, an overall calculation model of SSI was established, and the above-ground structure was meshed according to the calculation accuracy requirements. The soil layers of the building site are subjected to one-dimensional horizontal stratification equivalent linearization to obtain the characteristics of the soil layers. For the underground structure in the overall calculation model, when it is a buried structure, the following steps are performed: A transition soil body is established at the boundary where the buried structure contacts the soil layer, and the transition soil body is given the same material properties as the equivalent linearized soil layer. The transition soil is divided into at least two layers that cover the outside of the buried structure, with the inner layer in contact with the buried structure and the outer layer in contact with the surrounding soil. In the vertical direction, the buried structure and the surrounding soil are cut according to the boundary of the actual geological soil layer. The transition soil is divided into grids in each geological soil layer, and the grid density gradually transitions from large to small from the outside to the inside. For the underground structure in the overall calculation model, when it is a pile foundation, the following steps are performed: In the vertical direction, the pile foundation and the surrounding soil are cut according to the boundary of the actual geological soil layer. The solid between the bottom surface of the bearing structure of the pile foundation and the top surface of the bottom plate of the above-ground structure is divided into at least three layers from top to bottom, and the grid density gradually transitions from small to large from top to bottom.

2. The method for optimizing the mesh generation of structure and foundation in SSI calculation according to claim 1, characterized in that, The transition soil is divided to form a two-layer structure that covers the outside of the buried structure.

3. The method for optimizing the mesh generation of structure and foundation in SSI calculation according to claim 2, characterized in that, In the vertical direction, the outer layer is meshed according to the shear wave velocity of the corresponding geological soil layer, and the inner layer is meshed according to the calculation accuracy requirements.

4. The method for optimizing the mesh generation of structure and foundation in SSI calculation according to claim 3, characterized in that, In the vertical direction, the maximum cell size of the outer layer is calculated according to the following formula: h=V s / 5f max In the formula: Vs is the shear wave velocity of the foundation soil layer; f max This is the highest frequency of earthquake vibrations.

5. The method for optimizing the mesh generation of structure and foundation in SSI calculation according to claim 3 or 4, characterized in that, In the horizontal direction, the grid size of the transition soil is 1.3 to 1.7 times that of the grid size in the vertical direction.

6. The method for optimizing the mesh generation of structure and foundation in SSI calculation according to claim 3 or 4, characterized in that, In the vertical direction, the transition soil is arranged in columns at each height, with each grid in each column having the same horizontal dimension.

7. The method for optimizing the mesh generation of structure and foundation in SSI calculation according to claim 1, characterized in that, The solid structure between the bottom surface of the bearing structure of the pile foundation and the top surface of the bottom plate of the above-ground structure is divided into three layers from top to bottom.

8. The method for optimizing the mesh generation of structure and foundation in SSI calculation according to claim 7, characterized in that, In the vertical direction, each layer of the structure is divided into grids according to the shear wave velocity of the corresponding geological soil layer.

9. The method for optimizing the mesh generation of structure and foundation in SSI calculation according to claim 7 or 8, characterized in that, The top layer is divided according to the structural units of the base plate, and the bottom layer is divided into uneven units with cylindrical pile foundations.

10. The method for optimizing the mesh generation of structure and foundation in SSI calculation according to claim 7 or 8, characterized in that, In the vertical direction, the solid between the bottom surface of the bearing structure of the pile foundation and the top surface of the base plate of the above-ground structure is aligned with a grid at each height, and the horizontal dimensions of each grid in each column are the same.

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