BIM and finite element analysis based foundation pit stability analysis method

Abstract

The application 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, which comprises the following steps: determining intersection characteristic values based on the number of all vertex indexes of each supporting grid unit appearing in a vertex index intersection set; determining angle characteristic values based on the included angles between each supporting grid unit and all adjacent supporting grid units thereof; determining distance characteristic values by analyzing the distances from each supporting grid unit to all foundation pit external corner grid units and all foundation pit internal corner grid units, and combining the intersection characteristic values and the angle characteristic values to determine grid refinement characteristic values of each supporting grid unit, so as to refine a finite element model of the foundation pit. The application solves the problem of inaccurate grid division of the finite element model of the foundation pit, intelligently identifies key areas for grid refinement, and improves the overall efficiency and accuracy of the foundation pit stability analysis.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foundation pit engineering stability analysis, and particularly relates to a foundation pit stability analysis method based on BIM and finite element analysis. BACKGROUND

[0002] A foundation pit is an important component of underground engineering such as underground railways, underground stations, underground municipal facilities, and the like. The stability of the foundation pit directly affects the construction quality and safety during construction of these underground engineering projects. The finite element analysis method is a commonly used method for analyzing the stability of a foundation pit. A foundation pit BIM model established by BIM technology is converted into a three-dimensional finite element model to simulate the stress and displacement changes during the construction process of the foundation pit, and the stability coefficient of the foundation pit is calculated based on the strength reduction method.

[0003] When converting the foundation pit BIM model into a three-dimensional finite element model, an overall grid group is usually generated. In order to improve the engineering authenticity of the subsequent finite element simulation results, the model needs to be subjected to grid division processing. However, existing grid division methods often fail to take into account the differentiated needs of different regions of the foundation pit, resulting in excessive refinement of non-critical regions, which significantly increases the consumption of computing resources and time costs. At the same time, insufficient refinement of critical regions affects the simulation accuracy, ultimately reducing the overall efficiency and accuracy of the foundation pit stability analysis. SUMMARY

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

[0005] The foundation pit stability analysis method based on BIM and finite element analysis of the present application adopts the following technical solutions:

[0006] obtaining a finite element model of a foundation pit and coordinates and indices of all vertices of each grid element in the finite element model, wherein all grid elements include support grid elements and soil grid elements;

[0007] counting the intersection of the vertex indices of all support grid elements and all soil grid elements, and determining an intersection characteristic value of each support grid element based on the number of occurrences of all vertex indices of each support grid element in the intersection of vertex indices;

[0008] determine an angle feature value of each supporting grid unit based on the included angle between each supporting grid unit and all adjacent supporting grid units thereof, to screen out corner grid units from all supporting grid units; construct a simple polygon based on the barycentres of all corner grid units using a geometric algorithm; obtain projection points of each corner grid unit, and divide all corner grid units into a foundation pit positive corner grid unit and a foundation pit negative corner grid unit based on the position distribution of the projection points relative to the simple polygon; determine a distance feature value of each supporting grid unit by analyzing the distance of each supporting grid unit to all foundation pit positive corner grid units and all foundation pit negative corner grid units, and determine a grid refinement feature value of each supporting grid unit in combination with the intersection feature value and the angle feature value;

[0009] screen out a grid unit to be refined from all supporting grid units based on the grid refinement feature value, and refine the grid unit to be refined to obtain a finite element model of a refined foundation pit for foundation pit stability analysis.

[0010] Preferably, the intersection feature value of each supporting grid unit is a proportion of the number of vertex index intersections of all vertex indices of each supporting grid unit.

[0011] Preferably, the angle feature value of each supporting grid unit is a maximum value in the included angles between each supporting grid unit and all adjacent supporting grid units thereof.

[0012] Preferably, the corner grid unit is a supporting grid unit with an angle feature value greater than 0.

[0013] Preferably, the obtaining of the projection points of each corner grid unit comprises:

[0014] In all adjacent grid units of each supporting grid unit, the adjacent grid unit with the largest included angle with the supporting grid unit is recorded as a feature grid unit, and the projection point of the intersection line between each supporting grid unit and its feature 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 corner grid unit.

[0015] Preferably, the division of all corner grid units into a foundation pit positive corner grid unit and a foundation pit negative corner grid unit comprises:

[0016] The corner grid unit whose projection point is not in the simple polygon is recorded as a foundation pit positive corner grid unit, and all the remaining corner grid units are recorded as foundation pit negative corner grid units.

[0017] Preferably, the distance feature value of each supporting grid unit is a result of the minimum distance of each supporting grid unit to all foundation pit negative corner grid units divided by the minimum distance of the corresponding supporting grid unit to all foundation pit positive corner grid units.

[0018] Preferably, the grid refinement characteristic value of each supporting grid unit is a result of positive fusion of a normalized value of the intersection characteristic value, a normalized value of the angle characteristic value and a normalized value of the distance characteristic value of each supporting grid unit.

[0019] Preferably, the screening of the grid units to be refined from all supporting grid units and the refinement of the grid units to be refined to obtain the finite element model of the refined foundation pit comprise:

[0020] Taking the grid refinement characteristic values of all supporting grid units as inputs of a threshold segmentation algorithm, outputting a segmentation threshold value, and taking the supporting grid units with grid refinement characteristic values greater than the segmentation threshold value as the grid units to be refined;

[0021] Taking all the grid units to be refined as inputs of an adaptive grid refinement algorithm, outputting the refined grid units, and obtaining the finite element model of the refined foundation pit.

[0022] Preferably, the method for the stability analysis of the foundation pit comprises:

[0023] Using the finite element strength reduction method to numerically simulate the finite element model of the refined foundation pit to obtain the stability coefficient of the foundation pit supporting structure in the finite element model when the foundation pit supporting structure is destroyed.

[0024] An embodiment of the present application provides a method for the stability analysis of a foundation pit based on BIM and finite element analysis, and the present application has at least the following beneficial effects:

[0025] The present application quantifies the close degree of the contact between the supporting grid units and the soil body by calculating the intersection characteristic value of each supporting grid unit through the statistics of the intersection of the vertex index of the supporting grid unit and the vertex index of the soil body grid unit, intelligently judges the grid refinement requirement, helps to more accurately simulate the stress and displacement distribution in the contact area in the finite element analysis, improves the calculation precision of the stability coefficient of the foundation pit, and avoids the excessive refinement of the non-key area, thereby optimizing the calculation efficiency; further, the present application constructs the angle characteristic value and the distance characteristic value, combines the intersection characteristic value to comprehensively calculate the grid refinement characteristic value, intelligently identifies the stress concentration effect of the foundation pit external corner and internal corner area, realizes the refined grid division of the key area, significantly improves the calculation precision of the stability coefficient of the foundation pit in the finite element analysis, optimizes the allocation of the calculation resources, and avoids the redundant refinement of the non-key area; finally, the present application intelligently identifies and finely divides the grid of the key area of the foundation pit by comprehensively combining the BIM and the finite element analysis technology and the grid refinement characteristic value, effectively improves the calculation precision of the stability coefficient of the foundation pit, avoids the excessive refinement of the non-key area, significantly reduces the consumption of the calculation resources, optimizes the analysis efficiency, and further improves the overall efficiency and accuracy of the stability analysis of the foundation pit. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the accompanying drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0027] Figure 1 The step flow chart of the foundation pit stability analysis method based on BIM and finite element analysis provided by an embodiment of the present application is shown in the following table.

[0028] Figure 2 The grid refinement feature value extraction process flow chart provided by an embodiment of the present application is shown in the following table. DETAILED DESCRIPTION

[0029] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined purpose of the application, the following describes the specific implementation, structure, features and effects of the foundation pit stability analysis method based on BIM and finite element analysis according to the present application in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0030] 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 the present application belongs.

[0031] The specific scheme of the foundation pit stability analysis method based on BIM and finite element analysis provided by the present application is described in detail below in combination with the accompanying drawings.

[0032] The foundation pit stability analysis method based on BIM and finite element analysis provided by an embodiment of the present application is described in detail as follows. Please refer to Figure 1 The method comprises the following steps:

[0033] Step S1: Obtain the finite element model of the foundation pit and the coordinates and indexes of all vertices of each grid element in the finite element model, wherein all grid elements include supporting grid elements and soil body grid elements.

[0034] According to the parameters of the supporting structure actually used in the foundation pit engineering and the soil parameters in the influence range during the excavation of the foundation pit, a BIM model of the foundation pit is constructed by using a BIM software, and the parameters of the supporting structure at least include the names, sizes and materials of various supporting components used in the foundation pit engineering, such as the diaphragm wall body and the reinforcement cage in the diaphragm wall support, the crown beam body and the crown beam reinforcement cage in the pile support, and the waist beam and the steel strand in the pile-anchor support, and the soil parameters at least include the cohesion, friction angle and thickness of the soil, and each component unit in the BIM model of the foundation pit is divided into a supporting component unit and a soil unit. In this embodiment, the BIM software is Revit software, and in the actual application process, as other implementation manners, the implementer can also use Bentley, CATIA and other software according to the specific circumstances, and the present embodiment does not make special limitation.

[0035] The process of constructing the BIM model of the foundation pit by using the BIM software and combining the collected parameters of the foundation pit is a known technology, and details are not described again.

[0036] The BIM model of the foundation pit is converted into a three-dimensional finite element model of the foundation pit by using the FEMTransfer software, and the finite element model is coarsely meshed by using a finite element analysis software to obtain the three-dimensional finite element model of the foundation pit after coarse meshing.

[0037] It should be noted that there are many commonly used finite element analysis software, and the ABAQUS software is used in this embodiment, and in the actual application process, as other implementation manners, the implementer can also use MSC or ANSYS and other finite element analysis software according to the specific circumstances, and the selection of the finite element analysis software is not specially limited in this embodiment.

[0038] In addition, the mesh type used for meshing in this embodiment is a tetrahedral mesh, and in the actual application process, as other implementation manners, the implementer can also use other mesh division types such as hexahedral mesh according to the specific circumstances, and the present embodiment does not make special limitation.

[0039] The vertex coordinates and vertex indexes of each mesh unit in the finite element model are obtained in the ABAQUS software, and the mesh unit is a triangle, the mesh units belonging to the supporting component unit are recorded as supporting mesh units, and the mesh units belonging to the soil unit are recorded as soil mesh units.

[0040] The construction of the BIM model and the process of converting the BIM model of the foundation pit into the finite element model of the foundation pit by using the FEMTransfer software are known technologies, and details are not described again.

[0041] Step S2: Determine the intersection feature value by intersecting the support and the soil grid element vertex index, calculate the angle feature value by combining the adjacent grid element angle, screen the pit angle grid element by using the pit angle barycenter to construct a polygon to divide the pit positive angle and pit negative angle element; Determine the grid refinement feature value of each support grid element by comprehensively considering the intersection, angle and distance feature values.

[0042] S2.1 Count the intersection of all support grid elements and all soil grid elements, and determine the intersection feature value of each support grid element based on the number of all vertex indexes of each support grid element appearing in the vertex index intersection.

[0043] During the excavation of the foundation pit, with the continuous excavation of the internal earthwork of the foundation pit, and the influence of the building load on the edge of the foundation pit, the earth pressure of the foundation pit support structure facing the inside of the foundation pit gradually decreases, while the earth pressure and building load facing the outside of the foundation pit remain unchanged, thereby causing the earth pressure difference inside and outside the foundation pit support structure to be more obvious, thereby causing the foundation pit support structure to have horizontal displacement and deformation facing the inside of the foundation pit, affecting the stability of the foundation pit during its excavation process.

[0044] In order to better simulate the stress and displacement distribution of the contact area between the foundation pit support structure and the foundation pit soil in the subsequent finite element analysis of the foundation pit, it is necessary to more carefully divide the grid elements corresponding to the contact area between the foundation pit support structure and the foundation pit soil in the finite element model of the foundation pit, thereby more accurately calculating the stability coefficient of the foundation pit, therefore, the embodiment determines the intersection feature value of each support grid element by counting the intersection of all support grid elements and all soil grid elements, based on the number of all vertex indexes of each support grid element appearing in the vertex index intersection, to determine whether the support grid element needs to be refined, specifically:

[0045] In this embodiment, the intersection of all support grid elements and all soil grid elements is counted, and the intersection of vertex indexes is used to represent the set of all grid element vertex indexes of the contact area between the support member and the soil in the finite element model of the foundation pit.

[0046] Further, the proportion of the number of all vertex indexes of each support grid element in the vertex index intersection is taken as the intersection feature value of each support grid element.

[0047] According to the intersection characteristic value of each supporting grid unit, it can be understood that the first characteristic value quantifies the tightness of the contact between the supporting grid unit and the soil body. If the proportion of the number of all vertex indexes of the current supporting grid unit in the vertex index intersection is larger, the first characteristic value is larger, which means that the current supporting grid unit has a higher degree of coincidence with the contact surface in the geometric topology, and almost all the vertices of the current supporting grid unit participate in the contact interface, which means that the current supporting grid unit is located in the core area of the contact between the supporting structure and the soil body, and more meticulous grid division is needed to more accurately simulate the contact stress and displacement distribution.

[0048] On the contrary, if the proportion of the number of all vertex indexes of the current supporting grid unit in the vertex index intersection is smaller, the first characteristic value is smaller, which means that the current supporting grid unit has a lower degree of coincidence with the contact surface in the geometric topology, and only a few vertices of the current supporting grid unit participate in the contact interface, which means that the current supporting grid unit is located in the edge area or non-contact area of the contact between the supporting structure and the soil body, and grid refinement is not needed, and coarse grid can meet the simulation accuracy, thereby avoiding unnecessary computational overhead.

[0049] So far, by counting the vertex index intersection of the supporting grid unit and the soil grid unit, the intersection characteristic value of each supporting grid unit is calculated, the tightness of the contact between the supporting grid unit and the soil body is quantified, the grid refinement requirement is intelligently judged, which is helpful to more accurately simulate the stress and displacement distribution in the contact area in the finite element analysis, improve the calculation accuracy of the stability coefficient of the foundation pit, and avoid excessive refinement in the non-critical area, thereby optimizing the calculation efficiency.

[0050] S2.2. Determine the angle characteristic value of each supporting grid unit based on the angle between each supporting grid unit and all adjacent supporting grid units, to screen out pit corner grid units from all supporting grid units; based on the barycenter of all pit corner grid units, a simple polygon is constructed using a geometric algorithm; obtain the projection points of each pit corner grid unit, and based on the position distribution of the projection points relative to the simple polygon, all pit corner grid units are divided into foundation pit positive corner grid units and foundation pit negative corner grid units; by analyzing the distance from each supporting grid unit to all foundation pit positive corner grid units and all foundation pit negative corner grid units, the distance characteristic value of each supporting grid unit is determined, and the grid refinement characteristic value of each supporting grid unit is determined in combination with the intersection characteristic value and the angle characteristic value.

[0051] During the excavation of the foundation pit, there is a significant corner effect: the soil pressure and horizontal displacement of the supporting structure near the foundation pit negative corner are smaller than those in the middle, while those near the foundation pit positive corner are larger than those in the middle. This difference makes the stability of the foundation pit positive corner area better than that in the middle, while the stability of the foundation pit negative corner area is relatively poor, thereby affecting the overall stability of the foundation pit.

[0052] To improve the accuracy of the stability coefficient calculation, a fine analysis of the stress and displacement distribution in the area of the support structure near the external corner is required. Therefore, the embodiment determines the angle characteristic value of each support grid element based on the angle between each support grid element and all of its adjacent support grid elements, to screen out the pit corner grid elements from all support grid elements; constructs a simple polygon based on the barycentres of all pit corner grid elements using a geometric algorithm; obtains the projection points of each pit corner grid element, and divides all pit corner grid elements into pit external corner grid elements and pit internal corner grid elements based on the position distribution of the projection points relative to the simple polygon; determines the distance characteristic value of each support grid element by analyzing the distance from each support grid element to all pit external corner grid elements and all pit internal corner grid elements, and determines the grid refinement characteristic value of each support grid element in combination with the intersection characteristic value and the angle characteristic value, to implement more meticulous grid division of the support grid elements in the finite element model, and the specific process is as follows:

[0053] Firstly, the embodiment determines the angle characteristic value of each support grid element based on the angle between each support grid element and all of its adjacent support grid elements, to screen out the pit corner grid elements from all support grid elements, and the specific process is as follows:

[0054] In the embodiment, the maximum value of the angle between each support grid element and all of its adjacent support grid elements is taken as the angle characteristic value of each support grid element.

[0055] It should be noted that the specific method for obtaining the adjacent support grid elements is as follows: in all support grid elements, all support grid elements having a common vertex index value with each support grid element are taken as the adjacent support grid elements of each support grid element.

[0056] Since the calculation method of the angle between planes is a known technology, the specific calculation process of the angle between each support grid element and its adjacent support grid elements is not described again.

[0057] According to the angle characteristic value of each support grid element, it can be understood that the angle characteristic value is used to evaluate whether the local area composed of the support grid element and its adjacent support grid elements is a plane, i.e., whether it is in the external corner or internal corner area of the foundation pit. If the angle between the current support grid element and its adjacent support grid elements is larger, i.e., the angle characteristic value is larger, it means that the bending degree of the local area where the current support grid element is located is larger, i.e., it is more likely to be an external corner or internal corner, and the grid needs to be refined to more accurately simulate the stress concentration phenomenon at the corner;

[0058] Conversely, if the angle between the current supporting grid unit and its adjacent supporting grid unit is smaller, i.e. the angle characteristic value is smaller, it indicates that the bending degree of the local area where the current supporting grid unit is located is smaller, i.e. it is closer to a planar area, the stress distribution is more uniform, and the grid does not need to be refined, the coarse grid can already satisfy the simulation accuracy, thereby effectively reducing the calculation cost.

[0059] Further, in the embodiment, the corner grid unit is a supporting grid unit with an angle characteristic value greater than 0.

[0060] Further, in the embodiment, based on the barycenters of all pit corner grid units, a simple polygon is constructed by using a geometric algorithm; projection points of the pit corner grid units are obtained, and based on the position distribution of the projection points relative to the simple polygon, all pit corner grid units are divided into pit positive corner grid units and pit negative corner grid units, specifically:

[0061] The specific process of constructing the simple polygon by using the geometric algorithm is as follows: the projection points of the barycenters of all pit corner grid units in the XOY plane of the three-dimensional coordinate system of the finite element model are calculated, i.e. only the x coordinate value and the y coordinate value of the barycenter coordinates are retained, and the z coordinate value is ignored, the centroid of all the projection points is calculated, the polar angle of each projection point relative to the centroid is calculated, all the projection points are sorted in ascending order of the polar angle, the projection points are sequentially connected in the sorted order, and finally the first and last points are connected to form a simple polygon.

[0062] Secondly, in the embodiment, among all the adjacent grid units of each supporting grid unit, the adjacent grid unit with the largest included angle with the supporting grid unit is recorded as a characteristic grid unit, and the projection point of the intersection line between the supporting grid unit and the 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.

[0063] The pit corner grid unit whose projection point is not in the simple polygon is recorded as a pit positive corner grid unit, and the remaining all pit corner grid units are recorded as pit negative corner grid units, which are respectively used to represent the areas in the pit finite element model that are in the pit positive corner and the pit negative corner.

[0064] Further, in the embodiment, the distance characteristic value of each supporting grid unit is determined by analyzing the distances of each supporting grid unit to all pit positive corner grid units and all pit negative corner grid units, and the grid refinement characteristic value of each supporting grid unit is determined in combination with the intersection characteristic value and the angle characteristic value, specifically:

[0065] In the embodiment, the minimum value of the distance of each supporting grid unit to all pit negative corner grid units is divided by the minimum value of the distance of the corresponding supporting grid unit to all pit positive corner grid units, and the result is taken as the distance characteristic value of each supporting grid unit.

[0066] According to the distance characteristic value of each supporting grid unit, it can be understood that the distance characteristic value is used to evaluate the degree of the supporting grid unit close to the sun corner area of the foundation pit and far away from the shadow corner area. If the distance from the current supporting grid unit to all the shadow corner grid units of the foundation pit is smaller, and the distance from the current supporting grid unit to all the sun corner grid units is larger, the corresponding distance characteristic value is smaller, which indicates that the current supporting grid unit is closer to the shadow corner or the middle part, and is farther away from the sun corner area of the foundation pit, indicating that the grid unit is farther away from the sun corner of the foundation pit, and is 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, and the refined grid cannot significantly improve the accuracy, but increases the calculation amount. Therefore, the grid unit does not need to be refined.

[0067] On the contrary, if the distance from the current supporting grid unit to all the shadow corner grid units of the foundation pit is larger, and the distance from the current supporting grid unit to all the sun corner grid units is smaller, the corresponding distance characteristic value is larger, which indicates that the current supporting grid unit is closer to the sun corner area, and is farther away from the shadow corner or the middle part of the foundation pit, indicating that the grid unit is closer to the sun corner of the foundation pit, and is more affected by stress concentration, and the stress changes sharply and is unevenly distributed. In this area, the grid needs to be refined to more accurately simulate the stress concentration and deformation behavior, and the coarse grid cannot meet the accuracy requirement. Therefore, the grid unit must be refined.

[0068] Further, the result of forward fusion of the normalized value of the intersection characteristic value, the normalized value of the angle characteristic value and the distance characteristic value of each supporting grid unit is taken as the grid refinement characteristic value of each supporting grid unit.

[0069] It should be understood that forward fusion refers to combining two or more indicators together through addition or multiplication, so as to obtain a comprehensive indicator, so as to more comprehensively and accurately evaluate a phenomenon or problem. This fusion method is not limited to simple arithmetic operation, but can also include more complex statistical models and analysis methods, and the implementer can select them according to the specific circumstances, and the present embodiment does not make special limitations.

[0070] Preferably, as an implementation manner, the average of the normalized value of the intersection characteristic value, the normalized value of the angle characteristic value and the distance characteristic value of each supporting grid unit is taken as the grid refinement characteristic value of each supporting grid unit in the present embodiment. In actual application process, as other implementation manners, the implementer can also use other forward fusion methods such as product or sum value according to the specific circumstances, and the present embodiment does not make special limitations.

[0071] Preferably, the grid refinement characteristic value extraction process flowchart provided by the present embodiment is as shown in Figure 2

[0072] ​According to the mesh refinement characteristic value of each supporting grid unit, it can be understood that the mesh refinement characteristic value is used to comprehensively evaluate whether the grid unit needs to be refined, and reflects the comprehensive importance of the grid unit in contact, corner, and spatial distribution. If the intersection characteristic value of the current supporting grid unit is larger, it means that the current grid unit is in the contact core area, and the grid needs to be refined, and the corresponding mesh refinement characteristic value is larger. At the same time, if the angle characteristic value of the current supporting grid unit is larger, it means that the current grid unit is in the external corner or internal corner area, and if the distance characteristic value of the current supporting grid unit is larger, it means that the current grid is closer to the external corner area, and the grid needs to be refined, and the corresponding mesh refinement characteristic value is larger.

[0073] On the contrary, if the intersection characteristic value of the current supporting grid unit is smaller, it means that the current grid unit is in the contact edge or non-contact area, and the grid does not need to be refined, and the corresponding mesh refinement characteristic value is smaller. At the same time, if the angle characteristic value of the current supporting grid unit is smaller, it means that the current grid unit is in the plane area, and if the distance characteristic value of the current supporting grid unit is smaller, it means that the current grid is closer to the internal corner or middle area, and the grid does not need to be refined, and the corresponding mesh refinement characteristic value is smaller. Therefore, in the case of low mesh refinement characteristic value, coarse grid can be reasonably used for simulation, thereby effectively reducing the calculation cost while ensuring the overall analysis accuracy.

[0074] So far, by constructing the angle characteristic value and the distance characteristic value, and combining the intersection characteristic value to comprehensively calculate the mesh refinement characteristic value, the external corner, internal corner area and stress concentration effect thereof are intelligently identified, the fine grid division of the key area is realized, the calculation accuracy of the foundation pit stability coefficient in the finite element analysis is significantly improved, the calculation resource allocation is optimized, and the redundant refinement of the non-key area is avoided.

[0075] Step S3: Based on the mesh refinement characteristic value, the grid units to be refined are screened from all supporting grid units, and the refined finite element model of the foundation pit is obtained by refining the grid units, which is used for foundation pit stability analysis.

[0076] Further, based on the mesh refinement characteristic value obtained in step S2, the grid units to be refined are screened from all supporting grid units, and the refined finite element model of the foundation pit is obtained by refining the grid units, which is used for foundation pit stability analysis. The specific process is as follows:

[0077] In this embodiment, the mesh refinement characteristic values of all supporting grid units are taken as the input of the threshold segmentation algorithm, and the segmentation threshold is output. The supporting grid units with mesh refinement characteristic values greater than the segmentation threshold are taken as the grid units to be refined;

[0078] All the grid units to be refined are taken as the input of the adaptive mesh refinement algorithm, and the refined grid units are output to obtain the finite element model of the refined foundation pit.

[0079] It should be noted that there are many commonly used threshold segmentation algorithms, and in the embodiment, the maximum inter-class variance algorithm is used to screen and divide the support grid units. In actual application, as other implementation manners, the implementer can also use other threshold segmentation algorithms according to specific conditions, and the embodiment does not make special limitations.

[0080] Among them, the maximum inter-class variance algorithm and the adaptive grid refinement algorithm are all known technologies, and the specific process of screening the support grid units by using the maximum inter-class variance algorithm and the specific process of refining the grid units to be refined by using the adaptive grid refinement algorithm will not be repeated.

[0081] Further, the finite element strength reduction method is used to numerically simulate the finite element model of the refined foundation pit to obtain the stability coefficient of the foundation pit support structure when it is destroyed, that is, in the embodiment, the load F is applied to the finite element model of the foundation pit by using the ABAQUS software, and the reduction coefficient H is iteratively simulated to obtain the stability coefficient of the foundation pit support structure when it is destroyed in the finite element model of the foundation pit.

[0082] For example, it is assumed that the value of the load F applied to the finite element model of the foundation pit in the embodiment is 100 , and the value of the reduction coefficient H is set to 2.41, and the obtained stability coefficient is about 2.42. In actual application, the implementer can also set the load and the reduction coefficient according to specific conditions, and the embodiment does not make special limitations.

[0083] Among them, the foundation pit stability analysis based on the finite element strength reduction method is all known technology, and its specific process will not be repeated.

[0084] So far, the embodiment realizes intelligent identification and fine grid division of the key area of the foundation pit by comprehensively combining BIM and finite element analysis technology and combining with the grid refinement characteristic value, effectively improves the calculation precision of the stability coefficient of the foundation pit, avoids excessive refinement of the non-key area, significantly reduces the consumption of computing resources, optimizes the analysis efficiency, and further improves the overall efficiency and accuracy of the stability analysis of the foundation pit.

[0085] It should be noted that the above sequence of the embodiments of the present application is only for description, and does not represent the advantages and disadvantages of the embodiments. The above describes specific embodiments of the present specification. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multi-task processing and parallel processing are also possible or can be advantageous.

[0086] The various embodiments in the specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the difference from other embodiments.

[0087] The above-described embodiments are only used to illustrate the technical solutions of the present application, but not limit them; the technical solutions recorded in the foregoing embodiments are modified, or some technical features are replaced equivalently, and the essence of the corresponding technical solutions does not deviate from the scope of the technical solutions of the embodiments of the present application, which should be included in the protection scope of the present application.

Claims

1. A method for analyzing the stability of a foundation pit based on BIM and finite element analysis, characterized by, The method comprises the following steps: obtaining a finite element model of a foundation pit and coordinates and indexes of all vertices of each mesh element in the finite element model, wherein all mesh elements include supporting mesh elements and soil body mesh elements; counting the intersection of vertex indexes of all supporting mesh elements and all soil body mesh elements, and determining intersection characteristic values of each supporting mesh element based on the number of all vertex indexes of each supporting mesh element appearing in the intersection of vertex indexes; determining angle characteristic values of each supporting mesh element based on the included angle between each supporting mesh element and all adjacent supporting mesh elements of the supporting mesh element, so as to screen out corner mesh elements from all supporting mesh elements; constructing a simple polygon based on the barycenters of all corner mesh elements by using a geometric algorithm; obtaining projection points of each corner mesh element, and dividing all corner mesh elements into foundation pit positive corner mesh elements and foundation pit negative corner mesh elements based on the position distribution of the projection points relative to the simple polygon; determining distance characteristic values of each supporting mesh element by analyzing the distances of each supporting mesh element to all foundation pit positive corner mesh elements and all foundation pit negative corner mesh elements, and determining mesh refinement characteristic values of each supporting mesh element in combination with the intersection characteristic values and the angle characteristic values; screening out mesh elements to be refined from all supporting mesh elements based on the mesh refinement characteristic values, and refining the mesh elements to be refined to obtain a refined finite element model of the foundation pit, which is used for foundation pit stability analysis; the method comprises the following steps: in all adjacent mesh elements of each supporting mesh element, the adjacent mesh element with the largest included angle with the supporting mesh element is recorded as a characteristic mesh element, and the projection point of the intersection line between the supporting mesh element and the characteristic mesh element on the XOY plane of the three-dimensional coordinate system of the finite element model is taken as the projection point of each corner mesh element; the method comprises the following steps: the corner mesh element whose projection point is not in the simple polygon is recorded as a foundation pit positive corner mesh element, and the remaining all corner mesh elements are recorded as foundation pit negative corner mesh elements; the distance characteristic value of each supporting mesh element is the minimum value of the distance of each supporting mesh element to all foundation pit negative corner mesh elements divided by the minimum value of the distance of the corresponding supporting mesh element to all foundation pit positive corner mesh elements; the mesh refinement characteristic value of each supporting mesh element is the positive fusion result of the normalized value of the intersection characteristic value, the normalized value of the angle characteristic value and the normalized value of the distance characteristic value of each supporting mesh element.

2. The BIM and finite element analysis based excavation stability analysis method of claim 1, wherein, the intersection characteristic value of each supporting mesh element is the proportion of the number of all vertex indexes of each supporting mesh element in the intersection of vertex indexes. 3.The BIM and finite element analysis based excavation stability analysis method of claim 1, wherein, the angle characteristic value of each supporting mesh element is the maximum value of the included angles between each supporting mesh element and all adjacent supporting mesh elements of the supporting mesh element.

4. The BIM and finite element analysis based excavation stability analysis method of claim 1, wherein, the corner mesh element is a supporting mesh element with an angle characteristic value greater than 0.

5. The BIM and finite element analysis based excavation stability analysis method of claim 1, wherein, the method comprises the following steps: The grid refinement characteristic values of all supporting grid units are taken as inputs of a threshold segmentation algorithm, and a segmentation threshold is output, and the supporting grid units with grid refinement characteristic values greater than the segmentation threshold are taken as grid units to be refined; All the grid units to be refined are taken as inputs of an adaptive grid refinement algorithm, and refined grid units are output, so as to obtain a finite element model of the refined foundation pit.

6. The BIM and finite element analysis based excavation stability analysis method of claim 1, wherein, The method for analyzing the stability of the foundation pit comprises: The finite element model of the refined foundation pit is simulated by using a finite element strength reduction method, so as to obtain a stability coefficient of the foundation pit supporting structure in the finite element model when the foundation pit supporting structure is destroyed.

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