A structural analysis method for arch foundation based on rock and soil sub-surface

Abstract

The present invention relates to the technical field of arch bridge construction and design, and in particular to an arch seat foundation structure analysis method based on rock and soil stratification, which combines a finite element numerical simulation method with the rock and soil stratification obtained from drilling geological survey data to accurately simulate the rock and soil stratification of the arch seat and foundation, accurately simulate the physical action of the foundation and the interaction between the foundation and the arch seat foundation, so that the simulated physical behavior of the foundation is more consistent with the actual situation, can be better used to analyze the stress and deformation of the arch seat and the foundation under interaction, provide a scientific and reasonable reference for the design and construction of the arch bridge, and can provide a reasonable reference for the actual design and construction of the arch seat foundation structure based on the analysis results.

Description

Technical Field

[0001] The present invention relates to the technical field of arch bridge construction and design, and in particular to an arch seat foundation structure analysis method based on rock and soil sub-surface layers. Background Art

[0002] The arch seat is an important structure that transfers the upper load to the foundation. With the continuous improvement of arch bridge construction technology, the applicable scope and span of arch bridge types are also increasing. The analysis and design of the arch seat and arch seat foundation are often the basic basis for the feasibility of the arch bridge plan and are a key link in the construction of arch bridges.

[0003] Existing structural analysis methods for arch foundations generally adopt a model that expands the foundation force and calculation. This model does not perform structural analysis on arch foundations with special structures, such as arch foundations with a "toothed ridge" structure. The arch foundation is embedded in the slope of the foundation rock mass. During the structural analysis process, the constraint effect of the foundation on the arch foundation is often not considered, resulting in the structural analysis results not being able to truly demonstrate the interaction between the foundation and the arch foundation, and unable to obtain the stress and deformation characteristics of the foundation during actual construction and use, affecting the safe construction and use of arch bridges.

[0004] Therefore, there is an urgent need for a technical solution to solve the technical problem that the existing arch base structure analysis does not fully consider the interaction between the foundation and the arch base, cannot safely guide the construction of arch bridges, and affects the safe construction and use of arch bridges. Summary of the Invention

[0005] The purpose of the present invention is to provide an arch abutment foundation structure analysis method based on rock and soil sub-surface layering to address the technical problem that the existing arch abutment foundation structure analysis does not fully consider the interaction between the foundation and the arch abutment foundation, cannot safely guide the construction of arch bridges, and affects the safe construction and use of arch bridges.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for analyzing an arch foundation structure based on rock and soil sub-surface layers comprises the following steps:

[0008] S1. Establish a foundation space geometric model. According to the outer contour characteristics of the abutment, use solid units to divide the foundation space geometric model to obtain a number of grid units and contact units. The contact units are located on the contact surface between the abutment and the foundation.

[0009] S2. Divide the foundation space geometric model into a number of grid areas according to the plane projection, and use the least squares method to fit the coordinates of the corner points of each grid area to obtain the interface equation of the stratum material in each grid area;

[0010] S3. Based on the interface equations of the stratum materials in each grid area and the geotechnical layer information provided by the drilling geological exploration data, geotechnical material properties and physical properties are assigned to the grid cells and contact cells at the corresponding locations of the foundation, and contact properties are assigned to the contact cells at the corresponding locations to obtain a finite element model of the layered foundation;

[0011] S4. Apply loads and boundary constraints to the finite element model of the layered foundation, and perform calculations and analysis to obtain the stress conditions of the abutment under the interaction between the abutment and the foundation.

[0012] The present invention provides an arch seat foundation structure analysis method based on rock and soil stratification, combined with a finite element numerical simulation method, based on the rock and soil stratification obtained from drilling geological survey data, accurately simulates the rock and soil stratification of the arch seat and foundation, accurately simulates the physical action of the foundation and the interaction between the foundation and the arch seat foundation, so that the simulated physical behavior of the foundation is more consistent with the actual situation, can be better used to analyze the stress and deformation of the arch seat and the foundation under interaction, provide a scientific and reasonable reference for the design and construction of arch bridges, and can provide a reasonable reference for the actual design and construction of the arch seat foundation structure based on the analysis results.

[0013] As a preferred solution of the present invention, in S1, the foundation space geometric model is separated into a foundation geometric model with contact surfaces and an abutment foundation geometric model before division, so that the abutment and the foundation are two different planes on the same boundary to facilitate application of contact elements.

[0014] As a preferred solution of the present invention, the separation includes copying the abutment foundation elsewhere, deleting the original abutment foundation geometric elements, and then moving the copied abutment foundation back to its original location to form an independent abutment foundation geometric model and foundation geometric model.

[0015] As a preferred solution of the present invention, in S1, the boundary between the coarse and fine meshes is set 5 meters from the outer contour of the abutment. The area within the boundary is the fine mesh unit area, and the area outside the boundary is the coarse mesh unit area. The abutment foundation geometry model is located within the fine mesh unit area. This allows for regularized meshing throughout the model, effectively reducing the number of mesh units and improving computational efficiency.

[0016] As a preferred embodiment of the present invention, in S1, the transverse, longitudinal, and vertical scales of the foundation spatial geometric model are initially estimated based on terrain conditions and excavation conditions. These scales are then adjusted based on the results of the computational analysis until the impact of the structural scale changes on the computational analysis results falls within an acceptable range. This provides a computational model of reasonable scale, improving computational efficiency and accuracy.

[0017] As a preferred solution of the present invention, in S1, if the abutment does not bear lateral loads or the force exerted by the arch ribs on the abutment is longitudinal and has no inclination, the transverse bridge dimension of the foundation spatial geometry model is initially set to be greater than 1 times the abutment transverse width on one side; otherwise, it is initially set to 2-3 times the abutment transverse width on one side. If the foundation is a step-back foundation, the longitudinal bridge dimension of the foundation spatial geometry model is initially set to be 2-3 times the abutment longitudinal width; otherwise, it is initially set to be 0.5 times the abutment longitudinal width. The vertical dimension of the foundation spatial geometry model below the abutment is initially set to be 2-3 times the abutment vertical dimension. This allows for model establishment of appropriate scale, reduces the number of units, and improves computational efficiency.

[0018] As a preferred solution of the present invention, in S2, the plane projection coordinates of the three corner points of each grid area are set to (x1, y1), (x2, y2) and (x3, y3). Combined with the rock and soil layer information, the elevations of the corresponding points are fitted to z1, z2 and z3 respectively. Assuming that the grid area is small enough and the interface is approximately a plane, the equation group is solved. The unknown coefficients ABC and the interface equations of the stratum materials in each square grid area can be obtained.

[0019] As a preferred solution of the present invention, in S3, the ground is considered to be the interface between air and soil. Mesh cells with centroids above the ground are assigned to air cells, while mesh cells below the ground are assigned to foundation cells. The geotechnical material properties of the foundation cells are determined by combining the interface equations of the adjacent strata. Mesh cells that are air cells are deleted. During the numerical simulation, air is treated as a linear elastic element.

[0020] As a preferred solution of the present invention, in S3, the contact properties of the inclined surface, vertical surface and horizontal contact surface are limited to consider the contact properties of separability, limited slip and non-intrusion, and the contact friction coefficient of limited slip is determined according to the properties of the structural material.

[0021] As a preferred solution of the present invention, in S4, the load application includes selecting a node group of the corresponding action area of ​​the arch rib or selecting several nodes at corresponding positions to apply the load of the arch rib acting on the arch seat; the boundary constraint condition includes applying a normal constraint to the model.

[0022] As a preferred solution of the present invention, in S4, the stress conditions include vertical stress at the base interface, horizontal stress at the platform back interface, vertical deformation of the base foundation, and horizontal deformation of the platform back foundation.

[0023] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0024] The present invention provides an arch seat foundation structure analysis method based on rock and soil stratification, combined with a finite element numerical simulation method, based on the rock and soil stratification obtained from drilling geological survey data, accurately simulates the rock and soil stratification of the arch seat and foundation, accurately simulates the physical action of the foundation and the interaction between the foundation and the arch seat foundation, so that the simulated physical behavior of the foundation is more consistent with the actual situation, can be better used to analyze the stress and deformation of the arch seat and the foundation under interaction, provide a scientific and reasonable reference for the design and construction of arch bridges, and can provide a reasonable reference for the actual design and construction of the arch seat foundation structure based on the analysis results. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 1 is a flow chart of a method for analyzing an abutment foundation structure based on rock and soil sub-surface layers according to Example 1;

[0026] Figure 2 1 is a schematic structural diagram of a certain abutment foundation according to Example 1;

[0027] Figure 3 is a side view of a certain abutment foundation of Example 1;

[0028] Figure 4 Schematic diagram of the structure of the foundation space geometric model of Example 1;

[0029] Figure 5 Schematic diagram of the foundation space geometry model divided into coarse and fine grid areas according to Example 1;

[0030] Figure 6 Schematic diagram of the foundation space geometric model divided by solid unit gridding in Example 1;

[0031] Figure 7 This is a schematic diagram of ground contour lines related to the example of Example 1;

[0032] Figure 8 This is a schematic diagram of the ground shape related to the example of Example 1;

[0033] Figure 9 is the finite element model of the layered foundation of Example 1;

[0034] Figure 10 1 is a schematic diagram of the calculation results of the vertical stress on the substrate interface obtained by example calculation in Example 1;

[0035] Figure 11 2. This is a schematic diagram of the calculation results of the horizontal stress on the platform back interface obtained by example calculation in Example 1;

[0036] Figure 12 1 is a schematic diagram of the calculation results of the vertical deformation of the base foundation obtained by example calculation in Example 1;

[0037] Figure 13 This is a schematic diagram of the calculation results of the horizontal deformation of the platform back foundation obtained by the example calculation in Example 1.

[0038] icon:

[0039] 1-arch foundation, 2-foundation, 21-soil mass 1, 22-soil mass 2, 23-rock mass. DETAILED DESCRIPTION

[0040] The present invention will be described in detail below with reference to the accompanying drawings.

[0041] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0042] Example 1

[0043] like Figure 1 As shown, a method for analyzing abutment foundation structure based on rock and soil sub-surface layers includes the following steps:

[0044] S1. Establish a foundation space geometry model. According to the outer contour features of the abutment, use solid units to divide the ground space geometry model to obtain a number of grid units and contact units. The contact units are located on the contact surface between the abutment and the foundation.

[0045] Specifically, considering the influence of boundary effects, a foundation space geometry model is established. If the abutment does not bear lateral loads or the force exerted by the arch rib on the abutment is along the longitudinal direction of the bridge and has no inclination, the transverse bridge dimension of the ground space geometry model is initially planned to be set to be greater than 1 times the transverse width of the abutment on one side; otherwise, it is initially planned to be set to 2-3 times the transverse width of the abutment on one side.

[0046] It should be noted that when the arch seat foundation is embedded in the mountain structure, the lateral rock mass and / or soil will impose transverse loads on the arch seat foundation. Therefore, during the numerical simulation process, when the arch seat is not subjected to transverse loads or the arch ribs do not impose transverse loads on the arch seat foundation, the transverse dimension of the initially proposed foundation space geometry model is smaller, so as to reduce the number of units that need to be analyzed in the numerical simulation and improve the calculation efficiency. When the arch seat is subjected to transverse loads or the force exerted by the arch ribs on the arch seat foundation has an inclination angle, for example, when the arch seat foundation is applied to a basket arch, the transverse scale of the foundation space geometry model is appropriately expanded relative to the arch seat foundation. The transverse scale of the foundation space geometry model is initially set to 2-3 times the transverse width of the arch seat foundation on one side, so as to facilitate the diffusion of stress during the numerical simulation process.

[0047] Specifically, if the foundation is a platform back foundation, the longitudinal bridge dimension of the foundation space geometry model is initially set to 2-3 times the longitudinal width of the arch seat; otherwise, it is initially set to 0.5 times the longitudinal width of the arch seat.

[0048] It should be noted that the longitudinal bridge-direction scale of the abutment foundation is an important factor in simulating the stress of the abutment foundation. Compared with the foundation close to the mid-span of the arch rib, by appropriately expanding the longitudinal bridge-direction scale of the initially proposed foundation space geometry model, the analysis results can be made more accurate, more reference analysis results can be obtained, and a more suitable reference basis can be provided for the actual construction of the abutment foundation.

[0049] Specifically, the vertical scale of the foundation space geometry model below the abutment is initially planned to be set to 2-3 times the vertical scale of the abutment.

[0050] It should be noted that the vertical scale above the foundation should be determined based on the actual terrain, excavation conditions, and the orthogonal relationship between the scales in the other two directions. Compared with the vertical scale above the arch foundation, the vertical scale below the arch foundation is an important factor in simulating the stress on the arch foundation. Therefore, in numerical simulation, appropriate expansion of the vertical scale is conducive to obtaining more calculation and analysis results, providing more valuable reference factors for the construction of arch bridges.

[0051] Preferably, in S1, the transverse, longitudinal, and vertical scales of the foundation spatial geometric model are initially estimated based on the terrain conditions and excavation conditions, and are adjusted based on the calculation and analysis results until the impact of the structural scale changes of the foundation spatial geometric model on the calculation and analysis results is within an acceptable range. This provides a calculation model of reasonable scale and improves calculation efficiency and accuracy.

[0052] Preferably, in S1, after the foundation space geometry model is established, the arch seat foundation is divided into several rectangular blocks according to the projection plane based on the geometric shape of the arch seat foundation, so that the upper and lower surfaces of the rectangular block of each arch seat foundation are both single planes, and then combined with the geometry divided by the arch seat foundation, the entire foundation space geometry model is divided into regions using orthogonal planes, and the coarse and fine grid dividing line is set at 5m from the outer contour of the arch seat, the area within the coarse and fine grid dividing line is the fine grid unit area, and the area outside the coarse and fine grid dividing line is the coarse grid unit area, so that the arch seat foundation geometry model is located in the fine grid unit area, so as to effectively reduce the number of grid units and improve calculation efficiency.

[0053] Furthermore, after the grid area is divided, the foundation space geometry model is separated into a foundation geometry model with a contact surface and an abutment foundation geometry model to ensure that the foundation space geometry model can be regularly meshed everywhere, improve the calculation accuracy, and make the abutment and the foundation two different planes on the same boundary so that contact units can be applied.

[0054] Specifically, the separation includes copying the abutment foundation elsewhere, deleting the original abutment foundation geometric elements, and then moving the copied abutment foundation back to its original location to form a relatively independent abutment foundation geometric model and foundation geometric model.

[0055] Furthermore, according to the divided grid lines, the foundation space geometric model is meshed as a whole using solid units to obtain a number of grid units and contact units. The contact units are located on the contact surface between the abutment foundation geometric model and the foundation geometric model, providing a structural basis for the subsequent finite element calculation and analysis.

[0056] It should be noted that the contact units are several units located at the contact surface between the arch seat foundation and the foundation. Since in actual construction, the rock and soil of the slope where the arch seat is located is actually a composite of multiple soil bodies on the slope surface, the material properties, physical properties and contact properties of different contact units are different. Therefore, this technical solution distinguishes the contact units from other grid units, so as to facilitate the use of the rock and soil layer information provided by the drilling geological survey data to assign material properties and contact properties that match the actual situation to the contact units at each elevation, so as to realize the assignment of corresponding foundation materials to multiple soil bodies, improve the accuracy of finite element calculation, and enable the calculation and analysis results to fully consider the interaction between the foundation and the arch seat foundation. The specific assignment process is described in the following steps.

[0057] S2. Divide the spatial geometric model into several grid areas according to the plane projection, and use the least squares method to fit the coordinates of the corner points of each grid area to obtain the interface equation of the stratum material in each grid area.

[0058] S3. Based on the interface equations of the stratum materials in each grid area and the geotechnical layer information provided by the drilling geological exploration data, the geotechnical material properties and physical properties of the grid units and contact units at the corresponding positions of the foundation are assigned, and the contact properties of the contact units at the corresponding positions are assigned to obtain the finite element model of the layered foundation.

[0059] S4. Apply loads and boundary constraints to the finite element model of the layered foundation, and perform calculations and analysis to obtain the stress conditions of the foundation and / or abutment under the interaction between the abutment and the foundation.

[0060] The adaptability and specific calculation and analysis steps of this embodiment are described below using a certain arch foundation as an example.

[0061] like Figure 2 The figure shows a certain arch foundation structure, the outer contour dimensions of which are 40m in the longitudinal direction of the bridge × 40m in the transverse direction of the bridge × 31m in height.

[0062] Corresponding to S1, first, as Figure 4As shown in the figure, a foundation space geometry model is established according to the size of the arch base. The scale of the foundation space geometry model is 140m along the bridge direction × 80m across the bridge direction × 160m in height.

[0063] Then, if Figure 3 As shown in the figure, according to the outer contour position of the arch seat, the arch seat foundation is divided into several rectangular parallelepipeds according to the projection plane, so that the upper and lower surfaces of each rectangular parallelepiped of the arch seat foundation are both single planes, as shown in the figure. Figure 5 As shown in the figure, combined with the geometry of the arch seat foundation, the entire foundation space geometry model is divided into regions using orthogonal planes, and the coarse-fine grid boundary line is set at 5m from the outer contour of the arch seat. The area within the coarse-fine grid boundary line is the fine grid unit area, and the area outside the coarse-fine grid boundary line is the coarse grid unit area, so that the arch seat foundation geometry model is located in the fine grid unit area. Then, the foundation space geometry model is separated into the foundation geometry model and the arch seat foundation geometry model with contact surfaces, so that the arch seat and the foundation are two different planes on the same boundary, so that the contact unit can be applied.

[0064] Then, if Figure 6 As shown, the foundation space geometric model is divided into solid units. The fine grid unit area is divided first, and then the coarse grid unit area is divided to obtain a number of grid units. The surface where the arch seat contacts the foundation is divided into contact units. In this embodiment, the maximum unit size in the fine grid unit area is 1.5m, the maximum unit size in the coarse grid unit area is 8m, and the maximum size of the contact unit is 1.5m.

[0065] Corresponding to S2, the foundation space geometric model is divided into several 2m×2m grid areas according to the plane projection. According to the model scale, the plane projection of the foundation space geometric model in this embodiment is divided into 70×40 areas. Combined with the coordinates of the corner points of each grid area, the least squares method is used to fit the interface equation of the stratum material in each grid area.

[0066] Specifically, we take the interface between air and foundation as an example. The interfaces of other materials are similar. First, we obtain the following information based on geological survey data: Figure 7 The ground contour diagram shown in the figure and Figure 8 The ground shape diagram shown in the figure is used to obtain the ground contour data. Then, the plane projection coordinates of the three corner points of each grid area are extracted, such as (x1, y1), (x2, y2), and (x3, y3). Substituting them into the ground contour data, the elevations of the corresponding points can be fitted to be z1, z2, and z3, respectively. Assuming that the grid area is small enough and the interface is approximately a plane, that is, the points on the interface satisfy Ax+By+Cz=1, substituting the coordinates of the three corner points of the grid area into the coordinates, we get:

[0067] Solving this set of equations can obtain the unknown coefficients A, B, C, and the interface equation of the grid area, thereby establishing the interface equation of each grid area.

[0068] Preferably, in numerical simulation, air can be regarded as a linear elastic unit with very small mass and stiffness. By treating air as a unit, it is possible to avoid simulating the ground as an irregular geometric surface.

[0069] Corresponding to S3, through each interface equation, the grid unit of the foundation space geometry model is selected according to the position, and all grid areas are traversed and judged. The grid units with the centroid above the ground are assigned to air units and deleted. The grid units with the centroid below the ground are foundation units, which belong to the foundation material. The specific foundation material is determined according to the interface equation of the adjacent stratum material. Finally, the foundation part in the foundation space geometry model is classified into multiple unit families according to the position. Each unit family consists of several grid units with the same rock and soil properties, and the following is obtained: Figure 9 The layered foundation finite element model shown in the figure, in which the abutment foundation 1 is embedded in the foundation 2, the bottom layer of the foundation 2 is rock mass 23, and the upper part along the slope has soil mass 1 21 and soil mass 2 22, and the materials of soil mass 1 21 and soil mass 2 22 are different.

[0070] Furthermore, contact elements at corresponding locations are selected based on the equations for each interface, and properties are assigned to the contact elements. In this embodiment, for conservative calculations, the normal stress of the contact material of the inclined and vertical surfaces is ignored, that is, only the contact properties of separability, slippage, and non-intrusion are considered. The contact properties of horizontal contact surfaces are limited to separability, limited slippage, and non-intrusion based on the material. The friction coefficient of limited slip contact is determined based on the structural material properties.

[0071] Specifically, in this embodiment, the properties of the rock foundation and structural materials are shown in Table 1. The material properties in Table 1 can be used to define the contact properties of each contact unit.

[0072] Table 1. List of properties of rock foundation and structural materials

[0073]

[0074] Corresponding to S4, normal constraints are applied to the two side surfaces, front and back surfaces, and bottom surfaces of the layered foundation finite element model. The forces transmitted by the arch ribs and the vertical forces transmitted by the junction piers are also applied. The forces transmitted by the arch ribs are divided into horizontal forces of 315060 kN, vertical forces of 335504 kN, and bending moments of 1161464 kN·m. The vertical forces of the junction piers are 117956 kN. The calculation and analysis results include the following: Figure 10 The calculation results of vertical stress on the base interface are shown in Figure 11 The calculation results of horizontal stress on the backside interface are shown in Figure 12 The calculation results of the vertical deformation of the base foundation shown in Figure 13 The calculation results of the horizontal deformation of the abutment foundation are shown. Based on the force and deformation results, and in comparison with relevant specifications and engineering safety requirements, it can be judged whether the arch foundation design is reasonable. If it is unreasonable, the design should be modified and S1-S4 should be repeated until the calculation results meet the requirements. The arch foundation can then be constructed based on the calculation results that meet the requirements.

[0075] It should be noted that the intersection surface between the arch rib and the abutment foundation is equivalent to the cross-section of the arch rib. By applying the load of the arch rib on the abutment foundation to the abutment foundation node group in the corresponding action area of ​​the arch rib, the force characteristics of the abutment foundation under the corresponding load, as well as the physical characteristics such as displacement and stress of each interface can be analyzed and obtained.

[0076] Specifically, when the forces near the junction of the arch seat foundation and the arch rib are not of concern in the numerical simulation, only several nodes at the corresponding positions can be selected for load application.

[0077] Specifically, the bending moment effect of the arch rib on the abutment foundation is decomposed into a pair of opposing forces with relative distances during numerical simulation.

[0078] The present embodiment provides an arch seat foundation structure analysis method based on rock and soil stratification, combined with a finite element numerical simulation method, by forming regularized grid units and contact units, accurately assigning values ​​to the grid units and contact units according to the rock and soil stratification conditions obtained from drilling geological survey data, reflecting the contact surface between the foundation and the arch seat of soil of different materials through the contact units, and realizing accurate assignment of foundation space geometric models under various soil environments, accurately simulating the physical effects of the foundation and the interaction between the foundation and the arch seat foundation, making the simulated physical behavior of the foundation more consistent with the actual situation, and can be better used to analyze the stress and deformation conditions of the arch seat and the foundation under interaction, providing a scientific and reasonable reference for the design and construction of arch bridges, and can provide a reasonable reference for the actual design and construction of the arch seat foundation structure based on the analysis results.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for analyzing abutment foundation structure based on rock and soil sub-surface, characterized in that: The steps include: S1. Establish a foundation space geometric model. According to the outer contour characteristics of the abutment, use solid units to divide the foundation space geometric model to obtain a number of grid units and contact units. The contact units are located on the contact surface between the abutment and the foundation. S2. Divide the foundation space geometry model into several grid areas according to the plane projection. Combine the coordinates of the corner points of each grid area and use the least squares method to fit the interface equation of the stratum material in each grid area. This includes setting the plane projection coordinates of the three corner points of each grid area to (x1, y1), (x2, y2) and (x3, y3). Combined with the rock and soil layer information, the elevations of the corresponding points are fitted to z1, z2 and z3 respectively. Assuming that each grid area is small enough and the interface is approximately a plane, solve the equation group , we can obtain the unknown coefficients ABC and the interface equation of the stratum materials in each grid area; S3. Based on the interface equations of the stratum materials in each grid area and the geotechnical layer information provided by the drilling geological exploration data, geotechnical material properties and physical properties are assigned to the grid cells and contact cells at the corresponding locations of the foundation, and contact properties are assigned to the contact cells at the corresponding locations to obtain a finite element model of the layered foundation; S4. Apply loads and boundary constraints to the finite element model of the layered foundation, and perform calculations and analysis to obtain the stress conditions of the abutment under the interaction between the abutment and the foundation.

2. The method for analyzing abutment foundation structure based on rock and soil sub-surface according to claim 1, characterized in that: In S1, the foundation space geometry model is separated into a foundation geometry model with a contact surface and an abutment foundation geometry model before partitioning.

3. The method for analyzing abutment foundation structure based on rock and soil sub-surface according to claim 2, characterized in that: In S1, the coarse-fine grid boundary is set at 5m outside the outer contour of the arch seat. The area within the coarse-fine grid boundary is the fine grid unit area, and the area outside the coarse-fine grid boundary is the coarse grid unit area. The geometric model of the arch seat foundation is located in the fine grid unit area.

4. The method for analyzing abutment foundation structure based on rock and soil sub-surface according to claim 1, characterized in that: In S1, the transverse, longitudinal, and vertical scales of the foundation spatial geometric model are initially estimated based on the terrain conditions and excavation conditions, and are adjusted based on the calculation and analysis results until the impact of the structural scale changes of the foundation spatial geometric model on the calculation and analysis results is within an acceptable range.

5. The method for analyzing abutment foundation structure based on rock and soil sub-surface according to claim 4, characterized in that: In S1, if the abutment does not bear lateral loads or the force exerted by the arch rib on the abutment is along the longitudinal bridge direction and has no inclination, the transverse bridge dimension of the foundation space geometry model is initially planned to be set to more than 1 times the transverse width of the abutment on one side; otherwise, it is initially planned to be set to 2-3 times the transverse width of the abutment on one side; if the foundation is a back-of-platform foundation, the longitudinal bridge dimension of the foundation space geometry model is initially planned to be set to 2-3 times the longitudinal width of the abutment; otherwise, it is initially planned to be set to 0.5 times the longitudinal width of the abutment; the vertical dimension of the foundation space geometry model below the abutment is initially planned to be set to 2-3 times the vertical dimension of the abutment.

6. The method for analyzing abutment foundation structure based on rock and soil sub-surface according to claim 1, characterized in that: In S3, the ground is regarded as the interface between air and rock and soil. The grid cells whose centroids are above the ground are assigned to air cells, and the grid cells below the ground are assigned to foundation cells. The rock and soil material properties of the foundation cells are determined in combination with the interface equations of the adjacent stratum materials. If the grid cell is an air cell, it is deleted.

7. The method for analyzing abutment foundation structure based on rock and soil sub-surface according to claim 1, characterized in that: In S3, the contact properties of the inclined surface, vertical surface and horizontal contact surface are limited to consider the contact properties of separability, limited slip and non-intrusion. The contact friction coefficient of limited slip is determined according to the structural material properties.

8. The method for analyzing abutment foundation structure based on rock and soil sub-surface according to any one of claims 1 to 7, characterized in that: In S4, the load application includes selecting a node group in the corresponding action area of ​​the arch rib or selecting several nodes at corresponding positions to apply the load of the arch rib acting on the arch seat; the boundary constraint condition includes applying a normal constraint to the model.

9. The method for analyzing abutment foundation structure based on rock and soil sub-surface according to claim 8, characterized in that: In S4, the stress conditions include vertical stress at the base interface, horizontal stress at the platform back interface, vertical deformation of the base foundation, and horizontal deformation of the platform back foundation.

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