An equivalent load application method for numerical simulation

Abstract

An equivalent load application method for numerical simulation is disclosed. This method involves dividing the established numerical model into a grid, obtaining the number and size of each grid at the top of the model, and extracting the coordinates of the center points of each grid. Then, elevation data of the corresponding surface above the top of the model is collected and digitized into a surface grid. By setting the geometric parameters of the surface grid, a one-to-one correspondence is established between the surface grid and the grid nodes at the top of the model. The thickness of the strata between each grid at the top of the model and the surface above it is obtained. The self-weight stress generated by the overlying rock layer at each grid at the top of the model is calculated using a formula. Finally, the solved self-weight stress is equivalently applied to the corresponding grids at the top of the model. This invention achieves refined, non-uniform equivalent load application at the top of the model, fully reflecting the influence of undulating surfaces on the model, greatly improving the reliability of numerical simulation results, and offering strong operability.

Description

Technical Field

[0001] This invention relates to an equivalent load application method for numerical simulation, belonging to the field of simulation technology for geotechnical engineering and mining engineering. Background Technology

[0002] With the rapid development of computer technology and numerical simulation technology, numerical simulation is becoming an irreplaceable method for modern engineering analysis and theoretical research. Given the long computation time for large numerical models, they are often not built to the Earth's surface. Instead, the influence of the geological strata between the top of the model and the surface is treated by applying an equivalent load.

[0003] This method calculates the self-weight stress generated by this part of the strata based on the average distance from the model to the ground surface, and then applies this stress directly to the top of the model, resulting in a uniform stress value in the top region of the model. However, for areas with significant surface undulations, this method is clearly too coarse, failing to reflect the impact of undulating surfaces on the model and reducing the reliability of the numerical simulation results. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides an equivalent load application method for numerical simulation. This method is applicable to areas with large surface undulations, can reflect the impact of undulating surfaces on the model, and improves the reliability of numerical simulation results.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: an equivalent load application method for numerical simulation, comprising the following steps:

[0006] (1) Determine the area to be studied based on the geological conditions and mining situation of the mine, establish a numerical model for its coal-bearing characteristics and complete the model mesh division; determine the material parameters of the model based on the physical and mechanical properties of coal and rock mass measured in the laboratory;

[0007] (2) Based on the model mesh divided in step (1), obtain the number of meshes at the top of the model and the size of each mesh; at the same time, extract the coordinates of the center point of each mesh at the top of the model;

[0008] (3) Collect the elevation data of the corresponding ground surface located above the top of the model, and convert the elevation data into the form of three-dimensional coordinates;

[0009] (4) Import the three-dimensional elevation coordinates obtained in step (3) into software with interpolation function for grid data conversion to obtain the surface grid; set the geometric parameters of the surface grid, including its maximum and minimum values ​​in the X and Y directions, the number of grids and the side length and number of nodes of each grid, to ensure that the geometric parameters are consistent with the top grid of the model and realize a one-to-one correspondence with the nodes of the top grid of the model.

[0010] (5) Divide the z' of each grid center in the surface grid into ij Coordinate minus the z-axis of the corresponding top mesh center of the model ij Coordinates are used to obtain the stratigraphic thickness h between each grid at the top of the model and the surface above it. ij Then, the self-weight stress σ generated by the overlying rock layers of each grid at the top of the model is obtained. ij Where i represents the i-th row of the grid, and j represents the j-th column of the grid;

[0011] (6) Using the built-in function language of the simulation software, the self-weight stress σ obtained in step (5) is expressed as... ij It is applied equivalently to the corresponding meshes at the top of the model.

[0012] Furthermore, in step (1), the physical and mechanical properties of the coal and rock mass include the coal and rock mass density, shear modulus, bulk modulus, cohesion, internal friction angle and tensile strength.

[0013] Furthermore, in step (1), the model mesh is divided into equal-sized meshes, that is, each mesh is a square mesh with equal side length.

[0014] Furthermore, in step (1), the model mesh is divided into unequal-sized meshes. Specifically, the unequal-sized meshes refer to the fact that each mesh at the top of the model is still a square mesh of equal size. The meshes of other parts of the model, excluding the meshes at the top of the model, change in size according to their distance from the key research area. That is, the mesh size closer to the key research area is smaller than the mesh size farther away from the key research area.

[0015] Furthermore, in step (3), there are two methods for collecting surface elevation data: one is to extract the surface contour coordinates corresponding to the study area using the list command in CAD based on the three-dimensional surface and downhole comparison map; the other is to select multiple borehole columnar diagrams near the study area, and use the surface elevation coordinates recorded in the diagrams to obtain the surface elevation data in the area by interpolation.

[0016] Furthermore, in step (5), the self-weight stress σ ij The calculation formula is σ ij =ρgh ij In the formula, ρ is the average density of the overlying rock layer, and g is the gravitational acceleration.

[0017] Furthermore, the simulation method for the numerical model is FLAC. 3D FLAC 2D One of the following finite element or discrete element analysis methods: UDEC, 3DEC, PFC.

[0018] This invention involves dividing the established numerical model into a grid, obtaining the number and size of each grid at the top of the model, and extracting the coordinates of the center points of each grid at the top of the model. Then, it collects elevation data of the corresponding surface above the top of the model and converts it into a grid, resulting in a surface grid. By setting the geometric parameters of the surface grid, a one-to-one correspondence is achieved between the surface grid and the grid nodes at the top of the model, obtaining the stratigraphic thickness between each grid at the top of the model and the surface above it. The self-weight stress generated by the overlying rock layer at each grid at the top of the model is calculated using a formula. Finally, the solved self-weight stress is applied equivalently to the corresponding grid at the top of the model. Compared with existing technologies, this invention achieves refined, non-uniform equivalent load application to the top of the model, fully reflecting the influence of undulating surfaces on the model, greatly improving the reliability of numerical simulation results, and offering strong operability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the area studied in the embodiments of the present invention;

[0020] Figure 2 This is a model mesh diagram in an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram illustrating the correspondence between the top grid of the model and the surface grid in an embodiment of the present invention;

[0022] Figure 4 This is an embodiment of the present invention in FLAC 3D Screenshots showing the application effect of the software. Detailed Implementation

[0023] The invention will now be further described with reference to the accompanying drawings.

[0024] A method for applying an equivalent load in numerical simulation includes the following steps:

[0025] (1) Determine the area to be studied based on the geological conditions and mining situation of the mine, establish a numerical model for its coal-bearing characteristics and complete the model mesh division; determine the material parameters of the model based on the physical and mechanical properties of coal and rock mass measured in the laboratory;

[0026] (2) Based on the model mesh divided in step (1), obtain the number of meshes at the top of the model and the size of each mesh; at the same time, extract the coordinates of the center point of each mesh at the top of the model;

[0027] (3) Collect the elevation data of the corresponding ground surface located above the top of the model, and convert the elevation data into the form of three-dimensional coordinates;

[0028] (4) Import the three-dimensional elevation coordinates obtained in step (3) into software with interpolation function for grid data conversion to obtain the surface grid; set the geometric parameters of the surface grid, including its maximum and minimum values ​​in the X and Y directions, the number of grids and the side length and number of nodes of each grid, to ensure that the geometric parameters are consistent with the top grid of the model and realize a one-to-one correspondence with the nodes of the top grid of the model.

[0029] (5) Divide the z' of each grid center in the surface grid into ij Coordinate minus the z-axis of the corresponding top mesh center of the model ij Coordinates are used to obtain the stratigraphic thickness h between each grid at the top of the model and the surface above it. ij Then, the self-weight stress σ generated by the overlying rock layers of each grid at the top of the model is obtained. ij Where i represents the i-th row of the grid, and j represents the j-th column of the grid;

[0030] (6) Using the built-in function language of the simulation software, the self-weight stress σ obtained in step (5) is expressed as... ij It is applied equivalently to the corresponding meshes at the top of the model.

[0031] Furthermore, in step (1), the physical and mechanical properties of the coal and rock mass include the coal and rock mass density, shear modulus, bulk modulus, cohesion, internal friction angle and tensile strength.

[0032] In one implementation, in step (1), the model mesh is divided into equal-sized meshes, that is, each mesh is a square mesh with equal side length.

[0033] As another implementation method, in step (1), the model mesh is divided into unequal-sized meshes. Specifically, the unequal-sized meshes refer to the fact that each mesh at the top of the model is still a square mesh of equal size; the meshes of other parts of the model, except for the meshes at the top of the model, change in size according to their distance from the key research area, that is, the mesh size closer to the key research area is smaller than the mesh size farther away from the key research area.

[0034] As a preferred embodiment, in step (2), the method for extracting the coordinates of the center points of each grid at the top of the model is as follows: based on the number of top grids or the size of each top grid in the established numerical model, the coordinates of the center points of each grid are listed using Excel software.

[0035] Alternatively, you can use the built-in functions of the simulation software to filter out the z-axis within each grid by traversing all grid nodes. ij The node with the largest coordinates is used to determine the top grid of the model, and then the coordinates of the center point of each grid are calculated based on the grid size.

[0036] As a preferred implementation method, there are two methods for collecting surface elevation data: one is to extract the surface contour coordinates corresponding to the study area using the list command in CAD based on the three-dimensional surface and downhole comparison map; the other is to select multiple borehole columnar sections near the study area and use the surface elevation coordinates recorded in the sections to obtain the surface elevation data of the area by interpolation.

[0037] In step (5), the self-weight stress σ ij The calculation formula is σ ij =ρgh ij In the formula, ρ is the average density of the overlying rock layer, and g is the gravitational acceleration.

[0038] As one implementation method, the simulation method for the numerical model is FLAC. 3D FLAC 2D One of the following finite element or discrete element analysis methods: UDEC, 3DEC, PFC.

[0039] Example:

[0040] For a specific mine, via FLAC 3D A numerical model is established using simulation methods, and an equivalent load is applied to the numerical model using the method of this invention. The specific steps are as follows:

[0041] (1) As Figure 1 As shown, the area under study is determined based on the geological conditions and mining situation of the mine. The coordinates of the corner points of this area are determined to be A(497132,890879), B(497932,890879), C(497132,890079), and D(497932,890079). The coordinates of the centers of the equilateral square grids where the corner points of this area are located are then... m is the side length of the grid;

[0042] (2) A numerical model was established based on the characteristics of this coal-bearing system. The model mesh is a square mesh of equal size, with each mesh having a side length of m = 10 meters. The coordinate range of the numerical model in the X direction is determined to be 497132–497932 m, the coordinate range in the Y direction is 890079–890879 m, and the coordinate range in the Z direction is 350–700 m. That is, the model size is 800 m × 800 m × 350 m. The model mesh diagram is shown below. Figure 2 As shown in Table 1; the mechanical parameters of the coal and rock strata are as follows:

[0043] Table 1 Mechanical parameters of coal and rock strata

[0044]

[0045] (3) Based on the model and its mesh size, extract the center coordinates AA of each mesh at the top of the model. ij As shown in Table 2:

[0046] Table 2 Coordinates of the center of the top grid of the model

[0047]

[0048] (4) Based on the 3D surface and downhole comparison map, the coordinates of the surface contour lines corresponding to the study area are extracted using the list command in CAD, forming a txt or excel file. This file is then imported into Surfer for meshing. The minimum value for the X' direction is set to 497132, and the maximum value to 497932. The minimum value for the Y' direction is set to 890079, and the maximum value to 890879. The mesh spacing is 10. The correspondence between these values ​​and the top mesh of the model is as follows: Figure 3 As shown; the coordinates B of the surface grid center obtained after grid data conversion. ij As shown in Table 3:

[0049] Table 3 Coordinates of the Center of the Surface Grid

[0050]

[0051] (5) z' of the surface grid center ij Coordinates minus the z-axis of the corresponding top grid center of the model ij Coordinates are used to obtain the formation thickness h between each grid at the top of the model and the corresponding surface grid. ij And then through the formula σ ij =ρgh ij Obtain the self-weight stress σ generated by the overlying rock strata of the model. ij ρ is the average density of the overlying rock, taken as 2500 kg / m³. 3 g is the acceleration due to gravity, taken as 10 m / s². 2 ;

[0052] (6) Using FLAC 3D The built-in FISH language's matrix() function creates a matrix to store information about the center of the top mesh of the model. The matrix has 6400 rows and 4 columns. The first column is the x-coordinate of the center of the top mesh, the second column is the y-coordinate, the third column is the z-coordinate, and the fourth column is the equivalent load that should be applied to the mesh.

[0053] (7) Using the LOOP statement in the FISH language, apply the corresponding equivalent loads to each mesh at the top of the model defined by the first three columns of the matrix. The final effect is as follows: Figure 4 As shown.

Claims

1. A method for applying an equivalent load in numerical simulation, characterized in that, Includes the following steps: (1) Determine the area to be studied based on the geological conditions and mining situation of the mine, establish a numerical model for its coal-bearing characteristics and complete the model mesh division; determine the material parameters of the model based on the physical and mechanical properties of coal and rock mass measured in the laboratory; (2) Based on the model mesh divided in step (1), obtain the number of meshes at the top of the model and the size of each mesh; at the same time, extract the coordinates of the center point of each mesh at the top of the model; (3) Collect the elevation data of the corresponding ground surface located above the top of the model, and convert the elevation data into the form of three-dimensional coordinates; (4) Import the three-dimensional elevation coordinates obtained in step (3) into software with interpolation function for grid data conversion to obtain the surface grid; set the geometric parameters of the surface grid, including its maximum and minimum values ​​in the X and Y directions, the number of grids and the side length and number of nodes of each grid, to ensure that the geometric parameters are consistent with the top grid of the model and realize a one-to-one correspondence with the nodes of the top grid of the model. (5) Divide the z' of each grid center in the surface grid into ij Coordinate minus the z-axis of the corresponding top mesh center of the model ij Coordinates are used to obtain the stratigraphic thickness h between each grid at the top of the model and the surface above it. ij Then, the self-weight stress σ generated by the overlying rock layers of each grid at the top of the model is obtained. ij Where i represents the i-th row of the grid, and j represents the j-th column of the grid; (6) Using the built-in function language of the simulation software, the self-weight stress σ obtained in step (5) is expressed as... ij It is applied equivalently to the corresponding meshes at the top of the model.

2. The method for applying an equivalent load in numerical simulation according to claim 1, characterized in that, In step (1), the physical and mechanical properties of the coal and rock mass include coal and rock mass density, shear modulus, bulk modulus, cohesion, internal friction angle and tensile strength.

3. The method for applying an equivalent load in numerical simulation according to claim 1, characterized in that, In step (1), the model mesh is divided into equal-sized meshes, that is, each mesh is a square mesh with equal side length.

4. The method for applying an equivalent load in numerical simulation according to claim 1, characterized in that, In step (1), the model mesh is divided into unequal-sized meshes. Specifically, the unequal-sized meshes refer to the fact that each mesh at the top of the model is still a square mesh of equal size. The meshes of other parts of the model, except for the meshes at the top of the model, change in size according to their distance from the key research area. That is, the mesh size closer to the key research area is smaller than the mesh size farther away from the key research area.

5. The method for applying an equivalent load in numerical simulation according to claim 1, characterized in that, In step (3), there are two methods for collecting surface elevation data: one is to extract the surface contour coordinates corresponding to the study area using the list command in CAD based on the three-dimensional surface and downhole comparison map; the other is to select multiple borehole columnar diagrams near the study area and use the surface elevation coordinates recorded in the diagrams to obtain the surface elevation data of the area by interpolation.

6. The method for applying an equivalent load in numerical simulation according to claim 1, characterized in that, In step (5), the self-weight stress σ ij The calculation formula is σ ij =ρgh ij In the formula, ρ is the average density of the overlying rock layer, and g is the gravitational acceleration.

7. The method for applying an equivalent load in numerical simulation according to claim 1, characterized in that, The simulation method for the numerical model is FLAC. 3D FLAC 2D One of the following finite element or discrete element analysis methods: UDEC, 3DEC, PFC.

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