Foundation pit stability analysis method based on BIM and finite element analysis

Abstract

The invention relates to the technical field of foundation pit engineering stability analysis, in particular to a foundation pit stability analysis method based on BIM and finite element analysis, and the method comprises the steps: determining an intersection feature value based on the number of vertex indexes of each support grid unit appearing in a vertex index intersection; determining an angle characteristic value based on the included angles between each support grid unit and all adjacent support grid units; distance characteristic values are determined by analyzing the distances from the supporting grid units to all the foundation pit external corner grid units and all the foundation pit internal corner grid units, and grid refining characteristic values of the supporting grid units are determined by combining the intersection characteristic values and the angle characteristic values, so that the finite element model of the foundation pit is refined. According to the method, the problem of inaccurate mesh division of the foundation pit finite element model is solved, mesh refinement is performed by intelligently identifying the key area, and the overall efficiency and accuracy of foundation pit stability analysis are improved.

Description

Technical Field

[0001] This application relates to the field of stability analysis technology for foundation pit engineering, specifically to a method for foundation pit stability analysis based on BIM and finite element analysis. Background Technology

[0002] Excavation pits are an important component of underground engineering projects such as subways, underground stations, and underground municipal facilities. The stability of the excavation pit directly affects the construction quality and safety of these underground projects. Finite element analysis is a commonly used method for excavation pit stability analysis. It simulates stress and displacement changes during construction by converting the BIM model of the excavation pit created using BIM technology into a three-dimensional finite element model, and calculates the stability coefficient of the excavation pit based on the strength reduction method.

[0003] When converting a foundation pit BIM model into a 3D finite element model, a single, unified mesh is typically generated. To improve the engineering realism of subsequent finite element simulation results, this model needs to be meshed. However, existing meshing methods often struggle to accommodate the differentiated needs of different areas within the foundation pit, leading to over-refinement of non-critical areas, significantly increasing computational resource consumption and time costs. Simultaneously, insufficient refinement of critical areas affects simulation accuracy, ultimately reducing the overall efficiency and accuracy of foundation pit stability analysis. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a foundation pit stability analysis method based on BIM and finite element analysis to solve the existing issues.

[0005] The foundation pit stability analysis method based on BIM and finite element analysis in this application adopts the following technical solution: Obtain the finite element model of the foundation pit and the coordinates and indices of all vertices of each mesh element, including support mesh elements and soil mesh elements; The intersection of vertex indices of all support grid elements and all soil grid elements is counted. Based on the number of times all vertex indices of each support grid element appear in the intersection of vertex indices, the intersection characteristic value of each support grid element is determined. Based on the angle between each support grid unit and all its adjacent support grid units, the angular feature value of each support grid unit is determined to filter out the pit corner grid units from all support grid units. Based on the centroid of all pit corner grid units, a simple polygon is constructed using a geometric algorithm. The projection points of each pit corner grid unit are obtained, and based on the positional distribution of the projection points relative to the simple polygon, all pit corner grid units are divided into pit convex corner grid units and pit concave corner grid units. By analyzing the distances of each support grid unit to all pit convex corner grid units and all pit concave corner grid units, the distance feature value of each support grid unit is determined. Combined with the intersection feature value and the angular feature value, the mesh refinement feature value of each support grid unit is determined. Based on the aforementioned mesh refinement feature values, mesh elements to be refined are selected from all support mesh elements and refined to obtain a refined finite element model of the foundation pit, which is used for foundation pit stability analysis.

[0006] Preferably, the intersection feature value of each support grid cell is the percentage of all vertex indices of each support grid cell in the intersection of vertex indices.

[0007] Preferably, the angular characteristic value of each support grid unit is the maximum value among the angles between each support grid unit and all its adjacent support grid units.

[0008] Preferably, the pit corner grid unit is a support grid unit with an angle feature value greater than 0.

[0009] Preferably, obtaining the projection points of each corner grid cell includes: Among all adjacent grid elements of each support grid element, the adjacent grid element with the largest included angle with each support grid element is denoted as the characteristic grid element. The projection point of the intersection line between each support grid element and its characteristic grid element on the XOY plane of the three-dimensional coordinate system of the finite element model is taken as the projection point of each pit corner grid element.

[0010] Preferably, dividing all pit corner mesh units into pit external corner mesh units and pit internal corner mesh units includes: The pit corner mesh element whose projection point is not within the simple polygon is denoted as the pit external corner mesh element, and all other pit corner mesh elements are denoted as the pit internal corner mesh element.

[0011] Preferably, the distance characteristic value of each support grid unit is the result of the minimum distance from each support grid unit to all pit inside corner grid units divided by the minimum distance from the corresponding support grid unit to all pit outside corner grid units.

[0012] Preferably, the mesh refinement feature value of each support grid unit is the result of a positive fusion of the normalized value of the intersection feature value, the normalized value of the angle feature value, and the normalized value of the distance feature value of each support grid unit.

[0013] Preferably, the step of selecting the mesh elements to be refined from all support mesh elements and refining them to obtain the refined finite element model of the foundation pit includes: The mesh refinement feature values ​​of all support mesh elements are used as input to the threshold segmentation algorithm, and the segmentation threshold is output. Support mesh elements whose mesh refinement feature values ​​are greater than the segmentation threshold are taken as mesh elements to be refined. All the mesh elements to be refined are used as input to the adaptive mesh refinement algorithm, and the refined mesh elements are output to obtain the refined finite element model of the foundation pit.

[0014] Preferably, the method for foundation pit stability analysis includes: Numerical simulation of the refined finite element model of the foundation pit was performed using the finite element strength reduction method to obtain the stability coefficient of the foundation pit support structure when it is damaged in the finite element model.

[0015] One embodiment of this application provides a method for foundation pit stability analysis based on BIM and finite element analysis. This application has at least the following beneficial effects: This application calculates the intersection characteristic value of each support grid unit by statistically analyzing the vertex index intersection of the support grid unit and the soil grid unit. This quantifies the tightness of the contact between the support grid unit and the soil, thereby intelligently determining the mesh refinement requirement. This helps to more accurately simulate the stress and displacement distribution in the contact area in finite element analysis, improving the accuracy of the foundation pit stability coefficient calculation, while avoiding excessive refinement in non-critical areas and optimizing computational efficiency. Furthermore, this application constructs angle characteristic values ​​and distance characteristic values, and combines them with intersection characteristic values ​​to comprehensively calculate mesh refinement characteristic values. This intelligently identifies the positive and negative corner areas of the foundation pit and their stress concentration effects, achieving refined mesh division for critical areas. This significantly improves the accuracy of the foundation pit stability coefficient calculation in finite element analysis, while optimizing computational resource allocation and avoiding redundant refinement in non-critical areas. Finally, this application integrates BIM and finite element analysis technologies, combined with mesh refinement characteristic values, to achieve intelligent identification and refined mesh division of critical areas of the foundation pit. This effectively improves the accuracy of the foundation pit stability coefficient calculation, while avoiding excessive refinement in non-critical areas, significantly reducing computational resource consumption, optimizing analysis efficiency, and thus improving the overall efficiency and accuracy of foundation pit stability analysis. Attached Figure Description

[0016] To more clearly illustrate the technical solutions and advantages in the embodiments of this application 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 of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A flowchart illustrating the steps of a foundation pit stability analysis method based on BIM and finite element analysis provided in one embodiment of this application; Figure 2 This is a flowchart illustrating the mesh refinement feature value extraction process provided in one embodiment of this application. Detailed Implementation

[0018] To further illustrate the technical means and effects adopted by this application to achieve the intended purpose of the invention, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of the foundation pit stability analysis method based on BIM and finite element analysis proposed in this application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0019] 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 application pertains.

[0020] The following description, in conjunction with the accompanying drawings, details the specific scheme of the foundation pit stability analysis method based on BIM and finite element analysis provided in this application.

[0021] This application provides an embodiment of a foundation pit stability analysis method based on BIM and finite element analysis. Specifically, the method is described below. Please refer to [link to relevant documentation]. Figure 1 The method includes the following steps: Step S1: Obtain the finite element model of the foundation pit and the coordinates and indices of all vertices of each mesh element, where all mesh elements include support mesh elements and soil mesh elements.

[0022] Based on the support structure parameters used in the actual foundation pit project and the soil parameters within the influence range during foundation pit excavation, a foundation pit BIM model is constructed using BIM software. The support structure parameters must include at least the names, dimensions, and materials of various support components used in the foundation pit project, such as: diaphragm wall and reinforcing cage in diaphragm wall support; capping beam and capping beam reinforcing cage in pile support; and waist beam and steel strand in pile anchor support. The soil parameters must include at least the cohesion, friction angle, and thickness of the soil. The various component units in the foundation pit BIM model are divided into support component units and soil units. In this embodiment, the BIM software is Revit. In actual applications, as other implementation methods, implementers may also use software such as Bentley and CATIA depending on the specific circumstances. This embodiment does not impose any special restrictions.

[0023] The process of using BIM software and combining it with the collected foundation pit parameters to construct a foundation pit BIM model is a well-known technology and will not be described in detail here.

[0024] The BIM model of the foundation pit was converted into a three-dimensional finite element model of the foundation pit using FEMTransfer software, and then coarse meshing was performed on the finite element model using finite element analysis software to obtain the three-dimensional finite element model of the foundation pit after coarse meshing.

[0025] It should be noted that there are many commonly used finite element analysis software programs. In this embodiment, ABAQUS software is used. In actual applications, as other implementation methods, implementers may also use finite element analysis software such as MSC or ANSYS depending on the specific circumstances. This embodiment does not impose any special restrictions on the selection of finite element analysis software.

[0026] Furthermore, the mesh type used for mesh division in this embodiment is a tetrahedral mesh. In practical applications, as other implementation methods, implementers may also use other mesh division types such as hexahedral networks depending on the specific circumstances. This embodiment does not impose any special restrictions.

[0027] In ABAQUS software, obtain the vertex coordinates and vertex index of each mesh element in the finite element model. The mesh element is triangular. Mesh elements belonging to the support component element are denoted as support mesh elements, and mesh elements belonging to the soil element are denoted as soil mesh elements.

[0028] The construction of the BIM model and the process of converting the BIM model of the foundation pit into a finite element model of the foundation pit using FEMTransfer software are well-known technologies and will not be described in detail here.

[0029] Step S2: Determine the intersection feature value by statistically analyzing the intersection of the vertex indices of the support and soil grid units, calculate the angle feature value by combining the angle between adjacent grid units, and screen the pit corner grid units. Use the centroid of the pit corner to construct polygons to divide the pit into positive and negative corner units. Determine the grid refinement feature value of each support grid unit by comprehensively considering the intersection, angle, and distance feature values.

[0030] S2.1 Calculate the intersection of vertex indices of all support grid elements and all soil grid elements. Based on the number of times all vertex indices of each support grid element appear in the intersection of vertex indices, determine the intersection characteristic value of each support grid element.

[0031] During the excavation of the foundation pit, as the soil inside the pit is continuously excavated and the load of the adjacent buildings is affected, the soil pressure on the inside of the foundation pit support structure gradually decreases, while the soil pressure and building load on the outside of the foundation pit remain unchanged. This results in an increasingly significant difference in soil pressure between the inside and outside of the foundation pit support structure, which in turn causes horizontal displacement and deformation of the foundation pit support structure on the inside of the foundation pit, affecting the stability of the foundation pit during the excavation process.

[0032] To better simulate the stress and displacement distribution in the contact area between the foundation pit support structure and the foundation pit soil in subsequent finite element analysis of the foundation pit, it is necessary to perform more detailed meshing of the corresponding mesh elements in the foundation pit finite element model for the contact area between the foundation pit support structure and the foundation pit soil. This will enable more accurate calculation of the foundation pit stability coefficient. Therefore, this embodiment determines the intersection characteristic value of each support mesh element by statistically analyzing the intersection of vertex indices of all support mesh elements and all soil mesh elements. This is based on the number of times all vertex indices of each support mesh element appear in the intersection of vertex indices, in order to determine whether the support mesh elements need to be refined. Specifically: In this embodiment, the intersection of vertex indices of all support grid cells and all soil grid cells is statistically analyzed. The vertex index intersection is used to characterize the set of vertex indices of all grid cells in the contact area between the support components and the soil in the finite element model of the foundation pit.

[0033] Furthermore, the proportion of all vertex indices of each support grid cell in the intersection of vertex indices is used as the intersection feature value of each support grid cell.

[0034] Based on the intersection eigenvalues ​​of each support grid unit, it can be understood that the first eigenvalue quantifies the tightness of the contact between the support grid unit and the soil. If the proportion of all vertex indices of the current support grid unit in the intersection of vertex indices is larger, the first eigenvalue is larger, indicating that the current support grid unit has a higher degree of overlap with the contact surface of the soil in terms of geometric topology. If almost all vertices of the current support grid unit participate in the contact interface, it indicates that the current support grid unit is located in the core area of ​​the contact between the support structure and the soil, and more detailed meshing is required to more accurately simulate the contact stress and displacement distribution. Conversely, if the proportion of all vertex indices of the current support grid element in the intersection of vertex indices is smaller, and the first eigenvalue is smaller, it indicates that the current support grid element has a lower degree of overlap with the soil contact surface in terms of geometric topology. The current support grid element has only a few vertices participating in the contact interface, indicating that the current support grid element is located in the edge region or non-contact region of the contact between the support structure and the soil. In this case, there is less need for mesh refinement, and the coarse mesh can be sufficient to meet the simulation accuracy, thereby avoiding unnecessary computational overhead.

[0035] Thus, this embodiment calculates the intersection characteristic value of each support grid unit by statistically analyzing the intersection of the vertex indices of the support grid unit and the soil grid unit, thereby quantifying the tightness of the contact between the support grid unit and the soil. This allows for intelligent judgment of the grid refinement requirements, which helps to more accurately simulate the stress and displacement distribution in the contact area in finite element analysis, improve the accuracy of the foundation pit stability coefficient calculation, and avoid excessive refinement in non-critical areas, thus optimizing calculation efficiency.

[0036] S2.2 Based on the angle between each support grid unit and all its adjacent support grid units, determine the angular feature value of each support grid unit to filter out the pit corner grid units from all support grid units; based on the centroid of all pit corner grid units, construct a simple polygon using a geometric algorithm; obtain the projection points of each pit corner grid unit, and based on the positional distribution of the projection points relative to the simple polygon, divide all pit corner grid units into pit convex corner grid units and pit concave corner grid units; by analyzing the distances of each support grid unit to all pit convex corner grid units and all pit concave corner grid units, determine the distance feature value of each support grid unit, and combine the intersection feature value and the angular feature value to determine the mesh refinement feature value of each support grid unit.

[0037] Significant corner effects exist during foundation pit excavation: the soil pressure and horizontal displacement of the support structure near the inside corner of the foundation pit are less than those in the middle, while those near the outside corner are greater than those in the middle. This difference makes the stability of the outside corner area better than that of the middle, while the stability of the inside corner area is relatively poor, thus affecting the overall stability of the foundation pit.

[0038] To improve the accuracy of stability coefficient calculation, a refined analysis of stress and displacement distribution in the support structure area near the external corner is required. Therefore, this embodiment determines the angular characteristic value of each support grid unit based on the angle between each support grid unit and all its adjacent support grid units, in order to screen out the pit corner grid units from all support grid units. Based on the centroid of all pit corner grid units, a simple polygon is constructed using a geometric algorithm. The projection points of each pit corner grid unit are obtained, and based on the positional distribution of the projection points relative to the simple polygon, all pit corner grid units are divided into pit external corner grid units and pit internal corner grid units. By analyzing the distances of each support grid unit to all pit external corner grid units and all pit internal corner grid units, the distance characteristic value of each support grid unit is determined. Combined with the intersection characteristic value and the angular characteristic value, the mesh refinement characteristic value of each support grid unit is determined, so as to implement a more refined mesh division of the support grid units in the finite element model. The specific process is as follows: First, in this embodiment, the angular characteristic value of each support grid unit is determined based on the angle between each support grid unit and all its adjacent support grid units, so as to filter out the pit corner grid units from all support grid units. Specifically: In this embodiment, the maximum value of the angle between each support grid unit and all its adjacent support grid units is taken as the angular characteristic value of each support grid unit.

[0039] It should be noted that the specific method for obtaining adjacent support grid cells is as follows: among all support grid cells, all support grid cells that share a common vertex index value with each other are considered as adjacent support grid cells.

[0040] Since the method for calculating the angle between planes is a well-known technique, the specific calculation process for the angle between each support grid unit and its adjacent support grid units will not be elaborated here.

[0041] Based on the angular characteristic values ​​of each support grid unit, it can be understood that the angular characteristic values ​​are used to evaluate whether the local area formed by the support grid unit and its adjacent support grid units is a plane, that is, whether it is located in the corner or inside corner area of ​​the foundation pit. If the angle between the current support grid unit and its adjacent support grid units is larger, that is, the angular characteristic value is larger, it indicates that the curvature of the local area where the current support grid unit is located is greater, that is, it is more likely to be a corner or inside corner, and the grid needs to be refined to more accurately simulate the stress concentration phenomenon at the corner. Conversely, if the angle between the current support grid cell and its adjacent support grid cells is smaller, that is, the smaller the angle characteristic value, it indicates that the curvature of the local area where the current support grid cell is located is smaller, that is, it is closer to a planar area, and the stress distribution is more uniform. There is no need to refine the grid, and the coarse grid is sufficient to meet the simulation accuracy, thereby effectively reducing the computational cost.

[0042] Furthermore, in this embodiment, the corner mesh unit is a support mesh unit with an angle feature value greater than 0.

[0043] Furthermore, in this embodiment, a simple polygon is constructed using a geometric algorithm based on the centroid of all pit corner mesh elements; the projection points of each pit corner mesh element are obtained, and based on the positional distribution of the projection points relative to the simple polygon, all pit corner mesh elements are divided into pit convex corner mesh elements and pit concave corner mesh elements. Specifically: The specific process of constructing a simple polygon using a geometric algorithm is as follows: Calculate the projection points of the centroids of all corner mesh elements onto the XOY plane of the finite element model's three-dimensional coordinate system, i.e., retain only the x and y coordinate values ​​of the centroids and ignore the z coordinate value; calculate the centroids of all projection points; calculate the polar angle of each projection point relative to the centroid; sort all projection points according to their polar angles from smallest to largest; connect the projection points in the sorted order; and finally connect the first and last points to form a simple polygon.

[0044] Secondly, in this embodiment, among all the adjacent grid units of each support grid unit, the adjacent grid unit with the largest included angle with each support grid unit is denoted as the characteristic grid unit. The projection point of the intersection line between each support grid unit and its characteristic grid unit on the XOY plane of the three-dimensional coordinate system of the finite element model is taken as the projection point of each pit corner grid unit.

[0045] The pit corner mesh elements whose projection points are not within the simple polygon are denoted as pit yang corner mesh elements, and all other pit corner mesh elements are denoted as pit yin corner mesh elements, which are used to characterize the regions in the pit finite element model that are located at the pit yang corner and pit yin corner, respectively.

[0046] Furthermore, this embodiment analyzes the distances from each support grid unit to all external corner grid units and all internal corner grid units of the foundation pit to determine the distance characteristic value of each support grid unit. Combining the intersection characteristic value and the angle characteristic value, the mesh refinement characteristic value of each support grid unit is determined, specifically: In this embodiment, the minimum distance from each support grid unit to all pit inside corner grid units is divided by the minimum distance from the corresponding support grid unit to all pit outside corner grid units, and the result is used as the distance feature value of each support grid unit.

[0047] Based on the distance characteristic values ​​of each support grid unit, it can be understood that the distance characteristic values ​​are used to evaluate the degree to which the support grid unit is close to the external corner area of ​​the foundation pit and far away from the internal corner area. If the distance of the current support grid unit to all internal corner grid units of the foundation pit is smaller, and the distance of the current support grid unit to all external corner grid units is larger, the corresponding distance characteristic value is smaller, indicating that the current support grid unit is closer to the internal corner or the middle. The farther away from the external corner area of ​​the foundation pit, the farther the grid unit is from the external corner of the foundation pit, the less affected by stress concentration, and the stress distribution tends to be stable. In this area, the coarse grid can accurately simulate the mechanical behavior. Refining the grid will not significantly improve the accuracy, but will increase the amount of calculation. Therefore, there is no need to refine the grid units. Conversely, if the distance between the current support grid unit and all the internal corner grid units of the foundation pit is larger, and the distance between the current support grid unit and all the external corner grid units is smaller, and the corresponding distance characteristic value is larger, it indicates that the current support grid unit is closer to the external corner area. The farther away from the internal corner or the middle of the foundation pit, the closer the grid unit is to the external corner of the foundation pit, the greater the influence of stress concentration, and the more drastic and uneven the stress changes. In such areas, it is necessary to refine the grid to more accurately simulate stress concentration and deformation behavior. Coarse grids cannot meet the accuracy requirements. Therefore, the grid units must be refined.

[0048] Furthermore, the normalized values ​​of the intersection feature values, the normalized values ​​of the angle feature values, and the normalized values ​​of the distance feature values ​​of each support grid unit are positively fused and used as the grid refinement feature values ​​of each support grid unit.

[0049] It should be understood that positive fusion refers to combining two or more indicators through addition or multiplication to obtain a comprehensive indicator, thereby more comprehensively and accurately assessing a phenomenon or problem. This fusion method is not limited to simple arithmetic operations, but can also include more complex statistical models and analytical methods. Implementers can choose according to specific circumstances, and this embodiment does not impose any special restrictions.

[0050] Preferably, as one implementation method, in this embodiment, the average of the normalized values ​​of the intersection feature values, the normalized values ​​of the angle feature values, and the normalized values ​​of the distance feature values ​​of each support grid unit is used as the grid refinement feature value of each support grid unit. In practical applications, as other implementation methods, implementers may also use other positive fusion methods such as product or sum values ​​according to specific circumstances. This embodiment does not impose any special restrictions.

[0051] Preferably, the flowchart of the mesh refinement feature value extraction process provided in this embodiment is as follows: Figure 2 As shown.

[0052] Based on the mesh refinement characteristic values ​​of each support grid unit, it can be understood that the mesh refinement characteristic values ​​are used to comprehensively evaluate whether the grid unit needs to be refined. They reflect the comprehensive importance of the grid unit in terms of contact, cornering, and spatial distribution. If the intersection characteristic value of the current support grid unit is larger, it means that the current grid unit is in the contact core area and needs to be refined. The corresponding mesh refinement characteristic value is also larger. At the same time, if the angle characteristic value of the current support grid unit is larger, it means that the current grid unit is in the positive or negative corner area. Furthermore, if the distance characteristic value of the current support grid unit is larger, it means that the current grid is closer to the positive corner area and needs to be refined. The corresponding mesh refinement characteristic value is also larger. Conversely, the smaller the intersection eigenvalue of the current support mesh element, the more likely it is that the current mesh element is at the contact edge or in a non-contact region, and therefore does not require mesh refinement; the corresponding mesh refinement eigenvalue is also smaller. Simultaneously, the smaller the angle eigenvalue of the current support mesh element, the more likely it is in a planar region, and the smaller the distance eigenvalue, the closer the mesh is to a corner or central region, and the less likely it is to require mesh refinement; the corresponding mesh refinement eigenvalue is also smaller. Therefore, when the mesh refinement eigenvalue is low, a coarse mesh can be reasonably used for simulation, effectively reducing computational costs while ensuring overall analysis accuracy.

[0053] Thus, this embodiment constructs angular and distance feature values, combines them with intersection feature values ​​to comprehensively calculate mesh refinement feature values, and intelligently identifies the positive and negative corners of the foundation pit and their stress concentration effects. This achieves refined mesh division of key areas, significantly improves the calculation accuracy of the foundation pit stability coefficient in finite element analysis, and optimizes the allocation of computing resources to avoid redundant refinement of non-critical areas.

[0054] Step S3: Based on the mesh refinement feature value, select the mesh elements to be refined from all support mesh elements and refine them to obtain the refined finite element model of the foundation pit, which is used for foundation pit stability analysis.

[0055] Furthermore, based on the mesh refinement feature values ​​obtained in step S2, this embodiment selects the mesh elements to be refined from all support mesh elements and refines them to obtain a refined finite element model of the foundation pit, which is used for foundation pit stability analysis. The specific process is as follows: In this embodiment, the mesh refinement feature values ​​of all support mesh units are used as input to the threshold segmentation algorithm, and the segmentation threshold is output. Support mesh units with mesh refinement feature values ​​greater than the segmentation threshold are used as mesh units to be refined. All the mesh elements to be refined are used as input to the adaptive mesh refinement algorithm, and the refined mesh elements are output to obtain the refined finite element model of the foundation pit.

[0056] It should be noted that there are many commonly used threshold segmentation algorithms. In this embodiment, the maximum inter-class variance algorithm is used to screen and divide the support grid cells. In practical applications, as other implementation methods, implementers may also use other threshold segmentation algorithms according to specific circumstances. This embodiment does not impose any special restrictions.

[0057] Among them, the Otsu's inter-class variance algorithm and the adaptive mesh refinement algorithm are both well-known technologies. The specific process of using the Otsu's inter-class variance algorithm to select support mesh elements and the specific process of using the adaptive mesh refinement algorithm to refine the mesh elements to be refined will not be described in detail.

[0058] Furthermore, in this embodiment, the finite element strength reduction method is used to perform numerical simulation on the refined finite element model of the foundation pit to obtain the stability coefficient of the foundation pit support structure when it is damaged in the finite element model. That is, in this embodiment, the ABAQUS software is used to apply the load F to the finite element model of the foundation pit and iterative simulation is performed with the reduction coefficient H to obtain the stability coefficient of the foundation pit support structure when it is damaged in the finite element model of the foundation pit.

[0059] For example, suppose that in this embodiment, the load F applied to the finite element model of the foundation pit is 100. If the reduction factor H is set to 2.41, the resulting stability factor is approximately 2.42. In practical applications, implementers can also set the load and reduction factor according to specific circumstances. This embodiment does not impose any special restrictions.

[0060] Among them, the foundation pit stability analysis based on the finite element strength reduction method is a well-known technology, and its specific process will not be described in detail.

[0061] Thus, this embodiment, by integrating BIM and finite element analysis technologies and combining mesh refinement feature values, achieves intelligent identification and refined mesh division of key areas of the foundation pit, effectively improving the accuracy of foundation pit stability coefficient calculation, while avoiding excessive refinement of non-critical areas, significantly reducing computational resource consumption, optimizing analysis efficiency, and thereby improving the overall efficiency and accuracy of foundation pit stability analysis.

[0062] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments of this specification have been described above. Additionally, the processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired results. In some implementations, multitasking and parallel processing are possible or may be advantageous.

[0063] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0064] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions of some of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for analyzing the stability of foundation pits based on BIM and finite element analysis, characterized in that, The method includes the following steps: Obtain the finite element model of the foundation pit and the coordinates and indices of all vertices of each mesh element, including support mesh elements and soil mesh elements; The intersection of vertex indices of all support grid elements and all soil grid elements is counted. Based on the number of times all vertex indices of each support grid element appear in the intersection of vertex indices, the intersection characteristic value of each support grid element is determined. Based on the angle between each support grid unit and all its adjacent support grid units, the angular feature value of each support grid unit is determined to filter out the pit corner grid units from all support grid units. Based on the centroid of all pit corner grid units, a simple polygon is constructed using a geometric algorithm. The projection points of each pit corner grid unit are obtained, and based on the positional distribution of the projection points relative to the simple polygon, all pit corner grid units are divided into pit convex corner grid units and pit concave corner grid units. By analyzing the distances of each support grid unit to all pit convex corner grid units and all pit concave corner grid units, the distance feature value of each support grid unit is determined. Combined with the intersection feature value and the angular feature value, the mesh refinement feature value of each support grid unit is determined. Based on the aforementioned mesh refinement feature values, mesh elements to be refined are selected from all support mesh elements and refined to obtain a refined finite element model of the foundation pit, which is used for foundation pit stability analysis.

2. The foundation pit stability analysis method based on BIM and finite element analysis as described in claim 1, characterized in that, The intersection characteristic value of each support grid cell is the percentage of all vertex indices of each support grid cell in the intersection of vertex indices.

3. The foundation pit stability analysis method based on BIM and finite element analysis as described in claim 1, characterized in that, The angular characteristic value of each support grid unit is the maximum value of the angle between each support grid unit and all its adjacent support grid units.

4. The foundation pit stability analysis method based on BIM and finite element analysis as described in claim 1, characterized in that, The pit corner grid unit is a support grid unit with an angle feature value greater than 0.

5. The foundation pit stability analysis method based on BIM and finite element analysis as described in claim 1, characterized in that, The process of obtaining the projection points of each corner grid cell includes: Among all adjacent grid elements of each support grid element, the adjacent grid element with the largest included angle with each support grid element is denoted as the characteristic grid element. The projection point of the intersection line between each support grid element and its characteristic grid element on the XOY plane of the three-dimensional coordinate system of the finite element model is taken as the projection point of each pit corner grid element.

6. The foundation pit stability analysis method based on BIM and finite element analysis as described in claim 1, characterized in that, The process of dividing all pit corner mesh elements into pit external corner mesh elements and pit internal corner mesh elements includes: The pit corner mesh element whose projection point is not within the simple polygon is denoted as the pit external corner mesh element, and all other pit corner mesh elements are denoted as the pit internal corner mesh element.

7. The foundation pit stability analysis method based on BIM and finite element analysis as described in claim 1, characterized in that, The distance characteristic value of each support grid unit is the result of the minimum distance from each support grid unit to all pit inside corner grid units divided by the minimum distance from the corresponding support grid unit to all pit outside corner grid units.

8. The foundation pit stability analysis method based on BIM and finite element analysis as described in claim 1, characterized in that, The mesh refinement feature value of each support grid unit is the result of a positive fusion of the normalized values ​​of the intersection feature value, the normalized value of the angle feature value, and the normalized value of the distance feature value of each support grid unit.

9. The foundation pit stability analysis method based on BIM and finite element analysis as described in claim 1, characterized in that, The process of selecting the mesh elements to be refined from all support mesh elements and refining them to obtain the refined finite element model of the foundation pit includes: The mesh refinement feature values ​​of all support mesh elements are used as input to the threshold segmentation algorithm, and the segmentation threshold is output. Support mesh elements whose mesh refinement feature values ​​are greater than the segmentation threshold are taken as mesh elements to be refined. All the mesh elements to be refined are used as input to the adaptive mesh refinement algorithm, and the refined mesh elements are output to obtain the refined finite element model of the foundation pit.

10. The foundation pit stability analysis method based on BIM and finite element analysis as described in claim 1, characterized in that, The analysis used for foundation pit stability includes: Numerical simulation of the refined finite element model of the foundation pit was performed using the finite element strength reduction method to obtain the stability coefficient of the foundation pit support structure when it is damaged in the finite element model.

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