A wall surface crack grid model construction method for optimizing constrained delaunay triangulation

Abstract

The application discloses a wall crack network grid model construction method of optimizing constrained Delaunay partition, comprising the following steps: S1, extracting all crack node coordinates and line segment number information; S2, performing smoothing treatment on the cracks; S3, drawing the smooth crack curve in the modeling software; the crack curve is stretched in the direction perpendicular to the wall surface, is converted into a plurality of curved surfaces, the intersection of the curved surfaces and the wall surface grid is obtained, and the real curve shape of the cracks on the wall surface is obtained; S4, obtaining the stretching vector of the cracks; S5, bidirectional stretching of the crack surface; S6, modeling by using the vertex coordinate information of the crack grid; S7, converting the crack surface into a grid and cutting; combining the grid of the required part after cutting with the wall surface grid; and S8, re-dividing the finite element grid of the whole geometric model. The application generates a crack surface which is more in line with the actual situation and has a specified tendency, an inclination angle and a depth while simplifying the crack curve, so that the precision and efficiency of numerical simulation are remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of soil crack simulation, and in particular relates to a method for constructing a wall crack grid model by optimizing constrained Delaunay subdivision. Background Art

[0002] As archaeologists excavate the soil, cracks in the soil will pose a serious safety hazard to the protection of the site, so soil cracks are an issue that cannot be ignored. In addition, during the long-term development process of geological formation and human factors, cracks will inevitably appear in the soil after excavation.

[0003] Therefore, studying soil cracks in related projects is extremely important, and a common approach currently involves modeling soil cracks. Numerical simulation research presents a significant challenge: establishing a realistic crack model—that is, constructing a crack model that can realistically represent the shape and development direction of wall cracks. For example, Chinese patent CN108090313B discloses a method for modeling and identifying complex rock cracks. Initially, the method utilizes ProE's superior modeling capabilities to model the complex model. In the mid-term, it utilizes ANSYS's powerful mesh processor for meshing. Finally, Flac3D is used for simulation calculations. These complementary approaches leverage each other's strengths and overcome their weaknesses, achieving a seamless link between ProE, ANSYS, and Flac3D. While this method avoids the significant time and effort researchers must devote to studying the complex FISH language in Flac3D and avoids the inability to model and mesh complex models in geotechnical engineering problems, it fails to fully consider the spatial development of cracks, focusing solely on the radial direction. Therefore, a numerical simulation model for cracks that investigates the development of cracks in three dimensions is needed to overcome issues such as the discrepancy between the results obtained from numerical simulations of regular cracks and the actual irregular cracks. Summary of the Invention

[0004] The purpose of the present invention is to provide a wall crack mesh model construction method based on optimized constrained Delaunay partitioning, so as to solve the technical problems in the prior art of not considering the strike and dip angle of the cracks in the process of crack modeling research, and of difficulty in generating high-quality meshes.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A method for constructing a wall crack mesh model by optimizing constrained Delaunay triangulation includes the following steps:

[0007] Step S1: Based on the known fracture line segment data, all fracture node coordinates and line segment number information are extracted and stored in a file. This file not only contains the key fracture geometry information, but also provides the necessary basic data for subsequent processing.

[0008] Step S2: Use the 3D Douglas Peucker algorithm to smooth the fracture data file. This eliminates curve irregularities while ensuring the rationality of the fracture, ensuring that the surface geometry of the fracture is more continuous and realistic, and avoiding errors caused by numerical calculations.

[0009] Step S3: Using the drawing function, a smooth crack curve is drawn in the modeling software based on the data removed in step S2. The crack curve is then stretched perpendicular to the wall surface to form a polyhedron, which is then meshed. The stretched mesh surface intersects with the mesh wall surface, and the coordinate information of all nodes on the intersection line is obtained to obtain the true curve shape of the crack on the wall surface.

[0010] Step S4: Based on the number, strike, and dip of each crack, the tensile vector of the corresponding crack is obtained, providing directional data support for the subsequent accurate modeling of the crack surface.

[0011] Step S5: Based on the stretching vector obtained in step S4 and the depth information of the corresponding crack, the surface is bidirectionally stretched to form a crack surface; and the coordinate information of the vertices of all crack surfaces in the surface mesh is obtained, which will play a key role in the subsequent modeling stage.

[0012] Step S6: Modeling is performed using the vertex coordinate information of the crack, and a data file is exported. This file contains the geometric information of the crack surface, providing a basis for the next step of model cutting.

[0013] Step S7: Mesh the crack surface and combine it with the wall mesh to form the entire crack geometry model to ensure the integrity and stability of the overall model.

[0014] Step S8: Re-divide the finite element mesh of the entire fracture geometry model to further optimize the model mesh structure and ensure that it can provide efficient and accurate results in numerical simulation.

[0015] Further optimization, in step 1, the number of the crack curve and the three-dimensional coordinates of each point are exported to a data file through a loop function.

[0016] Further optimization, in step S2, the process of smoothing the crack curve is as follows:

[0017] S2.1: Setting Thresholds D , find and connect the two vertices of the crack curve as the initial line segment;

[0018] S2.2: Calculate the maximum distance d between a point on the crack curve and a line segment max And determine whether it is less than the threshold D ;

[0019] S2.2.1: When the maximum distance is greater than D , then connect the point corresponding to the maximum distance on the crack curve and the vertices of the two segments to form a new broken line segment; re-judge whether the maximum distance between the two segments in the newly formed broken line segment and the points on the corresponding crack curve is less than the threshold D :

[0020] S2.2.1.1 If the maximum distance d max Greater than D , then repeat step S2.2.1 until the maximum distance d between the two line segments in the newly formed broken line segment and the points on the corresponding fracture curve is max Less than or equal to D ;

[0021] S2.2.2: When the maximum distance is less than or equal to D , the crack smoothing process ends;

[0022] S2.3: Repeat steps S2.1 and S2.2 until all fractal curves are smoothed.

[0023] Further optimization, in step S3, the process of obtaining the three-dimensional wall crack curve is as follows: the crack curve after smoothing in step 2 is stretched into a polyhedron in a direction perpendicular to the wall, so that it passes through the wall mesh, and then the polyhedron is converted into a mesh, and finally the wall mesh and the stretched mesh are intersected by software to obtain the intersection line.

[0024] Further optimization, in step S4, the process of obtaining the fracture stretch vector is as follows: call the Python script to convert the fracture number, depth, and dip angle data in Excel into a dictionary, traverse each row of data, and store the name, depth, and dip angle of each set of data in a list, calculate the vector projection and unit vector, and then obtain the strike unit vector, loop each fracture to export the stretch vector pkl file.

[0025] Further optimization, in step S5, the process of obtaining the coordinate information of the crack mesh vertices is as follows: according to the stretching vector obtained in step S4, the crack curve is bidirectionally stretched to form a crack surface, and the vertex information of the crack surface is recorded through a loop function and exported as a dat file.

[0026] Further optimization, in step S6, the process of fracture surface modeling is as follows: read the data file of step S5, organize the fracture information and cyclically generate multiple components, use the midpoints of the two nodes of the fracture edge as the keywords of the edge, create the crack surface after generating the components, merge the components and delete the temporary fracture curve, and export the fracture surface geometry file.

[0027] Further optimization, in step S7, the process of combining the crack and the wall is as follows: converting the crack surface into a mesh, cutting the crack mesh through software, and combining the required part of the mesh after cutting with the wall mesh by small triangular faces.

[0028] For further optimization, the re-meshing process in step S8 is as follows: the entire fracture geometry model is resh-ed, and the mesh edge length and mesh shape are re-set to generate a well-uniform mesh model. A fully triangular surface mesh is generated with a mesh size of 0.05 m and a ridge angle of 20°. Mesh quality directly affects key properties of numerical simulations, such as stability, accuracy, and convergence speed. Therefore, a high-quality mesh is crucial in the simulation process.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention can generate fracture grids with arbitrary development angles and change the fracture development depth to more accurately describe the fractures. In addition, the present invention can ensure the generation of high-quality grids, thereby improving the efficiency and accuracy of numerical simulations, providing a valuable reference for future fracture modeling, and having extremely strong guiding significance for actual archaeological engineering construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of a method for constructing a wall crack mesh model using optimized constrained Delaunay triangulation according to the present invention;

[0032] Figure 2 Schematic diagram of the crack smoothing process;

[0033] Figure 3 Schematic diagram of plane wall crack in Example 1;

[0034] Figure 4 Schematic diagram of the intersection of the wall grid and the stretched grid in Example 1;

[0035] Figure 5 Schematic diagram of the three-dimensional wall crack curve in Example 1;

[0036] Figure 6 Schematic diagram for solving the stretching vector in Example 1;

[0037] Figure 7 Schematic diagram of the fracture surface modeling in Example 1;

[0038] Figure 8 Schematic diagram of the small triangle face welding model for the mesh in Example 1;

[0039] Figure 9Schematic diagram of the overall model of the re-meshed wall crack mesh in Example 1;

[0040] Figure 10 Schematic diagram of the local model of the wall crack mesh after re-meshing in Example 1;

[0041] Figure 11 Schematic diagram of the comparison between the real picture and the simulated picture in Example 1, where 11 (a) is a knowledge photo of the wall, Figure 11 (b) is a model diagram generated using the method described in the present invention. DETAILED DESCRIPTION

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention. Example 1:

[0043] like Figure 1 As shown in FIG, a method for constructing a wall crack mesh model by optimizing constrained Delaunay meshing includes the following steps:

[0044] Step S1: Based on the known fracture line segment data, a loop function is called to store its node coordinates and line segment numbers in a dat file.

[0045] In this embodiment, the numbers and information of the wall crack curves are extracted based on the studied wall CAD file.

[0046] Step S2: Call the 3D Douglas Peucker algorithm to smooth the obtained crack dat file. In order to make the generated crack curve more realistic, set the threshold D The distance between the two ends of each crack curve is 0.001 m, and the points at both ends of each crack curve are found and connected as the initial line segment; then, the maximum distance between the point on the crack curve and the initial line segment is calculated. d max And determine whether it is less than the threshold D :when d max > D , the maximum distance on the connecting crack curve d max The corresponding points and the points on the two segments of the line segment are re-judged whether the maximum distance between the two segments and the points on the corresponding crack curve is less than the threshold. If the condition is not met, repeat this step until it is met; when d ≤ D, the crack smoothing process ends, and the next crack curve is detected until all crack curves are traversed; then, the vertex information of the smoothed crack curve number is exported as a dat file. Figure 2 Schematic diagram of crack smoothing using the 3D Douglas Peucker algorithm.

[0047] Due to space limitations, only part of the data is shown here, as shown in Tables 1, 2, 3, and 4. Table 1 shows the coordinate values ​​of each node on the original crack curve of number L149; Table 2 shows the coordinate values ​​of the nodes after the crack curve of number L149 is smoothed; Table 3 shows the coordinate values ​​of each node on the original crack curve of number L150; Table 4 shows the coordinate values ​​of the nodes after the crack curve of number L150 is smoothed.

[0048] Table 1 Coordinate values ​​of nodes on the original crack curve of No. L149

[0049]

[0050] Table 2 Coordinate values ​​of each node of the crack curve No. L149 after smoothing

[0051]

[0052] Table 3 Coordinate values ​​of nodes on the original crack curve of No. L150

[0053]

[0054] Table 4 Coordinate values ​​of each node of the crack curve No. L150 after smoothing

[0055]

[0056] Step S3: Using the drawing function, a smooth crack curve is drawn in the modeling software based on the data removed in step S2. The crack curve is then stretched perpendicular to the wall surface to form a polyhedron, which is then meshed. The stretched mesh surface intersects with the mesh wall surface, and the coordinate information of all nodes on the intersection line is obtained to obtain the true curve shape of the crack on the wall surface. Figure 3 Schematic diagram of plane wall crack in Example 1; Figure 4 Schematic diagram of the intersection of the wall mesh and the stretched mesh in Example 1. The yellow line in the figure represents the curve obtained by the intersection of the mesh surface and the mesh wall; Figure 5 Schematic diagram of the three-dimensional wall crack curve obtained by intersection in Example 1.

[0057] Step 4: The Python script converts the fracture number, depth, and dip angle data in Excel into a dictionary, iterates through each row of data, and stores the number, depth, and dip angle of each set of data in a list. It calculates the vector projection and unit vector, and then obtains the strike unit vector. It loops through each fracture to export the stretch vector pkl file.

[0058] Combine Figure 6 , the calculation process of the stretch vector is as follows:

[0059] ;

[0060] It turns out that: For cracks The stretch vector

[0061] in: With point A as the center, is the arc of radius; are all unit vectors;

[0062] is the angle between the crack and the strike direction, The projection of the crack segment on the strike vector.

[0063] Due to space limitations, only part of the data is presented here, such as the data of the two crack curves numbered L149 and L150 as shown in Tables 5, 6, and 7.

[0064] Table 5 Data of two crack curves numbered L149 and L150 in the Excel data table

[0065]

[0066] Table 6 Dictionary data of the two crack curves numbered L149 and L150

[0067]

[0068] Table 7 PKL files of two crack curves numbered L149 and L150

[0069]

[0070] Step 5: Based on the stretch vector obtained in step S4, perform bidirectional stretching on the crack curve to form a crack surface. Use a loop function to obtain the coordinate information of all crack vertices in the surface mesh and export the data as a .dat file. Tables 8 and 9 show the coordinate data of each vertex on the two crack surfaces numbered L149 and L150.

[0071] Table 8 Coordinate data of each vertex of the crack surface numbered L149

[0072]

[0073] Table 9 Coordinate data of each vertex of the crack surface numbered L150

[0074]

[0075] Step 6: Read the dat file from step S5, organize the crack information and generate multiple parts in a loop. Use the midpoints of the two nodes on the edge where each crack is located as the keyword of the edge. After generating the parts, create the crack surface, merge the parts and delete the temporary crack curve, and export the crack surface as an igs file. Figure 7 Schematic diagram of importing the igs file into the software for fracture surface modeling in Example 1.

[0076] Step 7: Convert the fracture surface generated in step 6 into a fracture mesh, cut the fracture mesh through software, and connect the required mesh to the wall mesh with small triangles. Figure 8 Schematic diagram of the model for connecting small triangular surfaces between the crack and the wall mesh in Example 1.

[0077] Step 8: The mesh quality directly affects the key properties of the numerical simulation, such as stability, accuracy, and convergence speed. Therefore, the mesh size is set to 0.05 m and the ridge angle is set to 20° to generate a full triangular surface mesh and mesh the model. Figure 9 Schematic diagram of the overall model of the re-meshed wall crack mesh in Example 1; Figure 10 Schematic diagram of the local model of the re-meshed wall crack mesh in Example 1.

[0078] Figure 11 Schematic diagram of the comparison between the real picture and the simulated picture in Example 1, where 11 (a) is a real picture of the wall, Figure 11 (b) is a model diagram generated using the method described in the present invention. This diagram demonstrates that the present invention can generate fracture meshes at any angle, with very high simulation accuracy. This provides a valuable reference for future fracture modeling and has strong guiding significance for actual archaeological engineering construction.

[0079] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A method for constructing a wall crack mesh model using optimized constrained Delaunay meshing, characterized in that: The following steps are involved: Step S1: Extract all crack node coordinates and line segment number information based on known crack line segment data and store them in a file; Step S2: Using the 3D Douglas Peucker algorithm to smooth the cracks and remove a large number of redundant graphic data points in the file; Step S3: Using a drawing function, a smooth crack curve is drawn in the modeling software based on the data removed in step S2. The crack curve is then stretched perpendicular to the wall surface to form a polyhedron, which is then meshed. The stretched meshed surface intersects with the meshed wall surface, and the coordinate information of all nodes on the intersection line is obtained to obtain the true curve shape of the crack on the wall surface. Step S4: according to the number, strike and dip of each crack, obtain the stretching vector of the corresponding crack; Step S5: Based on the stretching vector obtained in step S4 and the depth information of the corresponding crack, the surface is bidirectionally stretched to form a crack surface; and the coordinate information of the vertices of all crack surfaces in the surface mesh is obtained; Step S6: Modeling is performed using the vertex coordinate information of the fracture surface, and the data file is exported. The process of fracture surface modeling is as follows: Read the data file generated in step S5 and generate corresponding components based on each crack information; create a crack surface for each component using the midpoints of the two nodes on the edge where the crack is located as the key of the edge; finally, merge these components and delete the temporary crack curve, and export the crack surface geometry file; Step S7: Meshing the fracture surface and combining it with the wall mesh to form the entire fracture geometry model. The process of combining the fracture and the wall is as follows: Meshing the fracture surface and cutting the fracture mesh; connecting the required mesh of the cut portion with the wall mesh using small triangular faces to ensure the integrity and stability of the overall model. Step S8: Re-mesh the entire fracture geometry model using the finite element mesh. The re-meshing process is as follows: remesh the entire fracture geometry model, reset the mesh side length, and generate a mesh model with good uniformity. The mesh size is set to 0.05 m and the ridge angle is set to 20° to generate a full triangular surface mesh.

2. The wall crack mesh model construction method of optimized constrained Delaunay decomposition according to claim 1 is characterized in that: In step S1, the process of extracting crack information is as follows: traverse each crack curve, number all cracks, and obtain the coordinate information of each node of the corresponding crack curve according to the number.

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