Method, apparatus and program product for automatically generating a two-dimensional geological finite element model grid

Abstract

The present invention discloses a method, device and program product for automatically generating a mesh of a two-dimensional geological finite element model, which includes steps such as pixelating and dividing a two-dimensional geological profile image into multiple square blocks, determining the mesh size within each square block, identifying and dividing transition elements, and surface supplementation; the present invention determines the mesh size of different geotechnical materials in the two-dimensional geological profile according to the shear wave velocity of the medium, and pixelates the two-dimensional geological profile image according to the global minimum mesh size, laying the foundation for subsequent mesh generation; by dividing the two-dimensional geological profile and determining the local mesh size of each part after division, it is possible to minimize the number of elements in the finite element model while meeting the requirements of calculation accuracy; then, by identifying and dividing transition elements, the requirements of the finite element method for a two-dimensional spatial discrete mesh are met; finally, through the supplementation setting at the surface, the calculation error that appears at the surface steep slope caused by pixelation is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of finite element preprocessing in geotechnical engineering, and particularly relates to a method, device and program product for automatically generating a mesh of a two-dimensional geological finite element model. Background Art

[0002] Numerical simulation of dynamic responses of large-scale two-dimensional non-uniform sites is a problem frequently encountered in seismic and anti-explosion performance evaluations of long linear projects such as bridges and tunnels. Due to the high adaptability, flexibility and calculation accuracy of the finite element method, which can adapt to various complex geometric shapes and boundary conditions, it has become the primary choice for numerical analysis of dynamic responses of large-scale non-uniform sites. However, in the process of meshing a two-dimensional geological finite element model, it is necessary to simultaneously handle the geometric irregularities and mesh transition problems caused by material non-uniformity in order to balance calculation accuracy and efficiency. At present, existing finite element preprocessing software (such as ANSA, Hypermesh, Truegrid, etc.) does not have a dedicated module for this application scenario; moreover, when processing, it is necessary to manually optimize and adjust the generated mesh to ensure mesh quality, so it takes a long time and has a high technical threshold. The present invention proposes a method for automatically generating a two-dimensional finite element mesh based on a geological profile, which greatly reduces the time and difficulty required for finite element dynamic analysis modeling of large-scale two-dimensional complex sites. Summary of the Invention

[0003] The present invention provides a method, device and program product for automatically generating a mesh of a two-dimensional geological finite element model to solve technical problems such as pixelation, block division, identification and division of transition elements, and surface supplementation in automatic finite element meshing of a two-dimensional geological profile.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for automatically generating a mesh of a two-dimensional geological finite element model, characterized in that the specific steps are as follows:

[0006] Step 1: Determine the mesh size of different geotechnical materials in the two-dimensional geological profile according to the shear wave velocity;

[0007] Step 2: Pixelate the two-dimensional geological profile image according to the global minimum mesh size;

[0008] Step 3: Uniformly divide the pixelated two-dimensional geological profile into multiple square blocks of the same size according to the global maximum mesh size;

[0009] Step 4: Determine the initial mesh size S1 of each square block according to the distribution of different geotechnical materials within the square block;

[0010] Step 5: Determine the final grid size S2 of each square block according to the initial grid sizes of itself and the surrounding square blocks, so as to ensure that the final grid size does not exceed the initial grid size and the ratio of the final grid sizes of adjacent square blocks does not exceed 2;

[0011] Step 6: Uniformly divide each square block into multiple square units of the same size according to the final grid size, and identify the transition units and transition edges;

[0012] Step 7: Further divide the transition units according to the number and relative positions of the transition edges, and supplement triangular units and / or square units at the surface steep slopes to ensure a smooth transition of the surface; thus, generate the final two-dimensional geological finite element model grid.

[0013] Furthermore, for Step 1, determine the grid sizes of different geotechnical materials in the two-dimensional geological profile according to the shear wave velocity: Sort the different geotechnical materials in the two-dimensional geological profile in ascending order of the shear wave velocity, and their shear wave velocities are denoted as V s1 、V s2 、V s3 、...V sn , where n is the number of types of geotechnical materials included in the profile. Then, calculate the global minimum grid size, that is, the grid size L1 of the first type of geotechnical material, according to the following formula:

[0014] L1 = k1×V s1 / f max

[0015] f max is the upper limit of the frequency band of interest; k1 is an empirical constant, and its value is 1 / 8 to 1 / 12;

[0016] Next, determine the grid sizes of other geotechnical materials according to the following formula;

[0017]

[0018] L i and V si respectively represent the grid size and shear wave velocity of the i-th type of geotechnical material, where i ranges from 2 to n, denotes rounding down; the grid size L n of the n-th type of geotechnical material is the global maximum grid size.

[0019] Furthermore, for Step 2, pixelate the two-dimensional geological profile according to the global minimum grid size:

[0020] Pixelate the two-dimensional geological profile image at a resolution of m1×n1. The side length corresponding to each pixel is L1, and the corresponding material is the material corresponding to the pixel center in the original two-dimensional geological profile. The pixels corresponding to the blank areas in the two-dimensional geological profile are called blank pixels, and other pixels are called non-blank pixels.

[0021] The calculation formulas for m1 and n1 are as follows:

[0022]

[0023] W and H respectively represent the width and height of the two-dimensional geological profile. Denotes rounding up.

[0024] Furthermore, for step three, according to the global maximum grid size, the pixelated two-dimensional geological profile is evenly divided into multiple square blocks of the same size:

[0025] Add a column of blank pixels on each side of the pixelated profile, and then evenly divide it into m2×n2 square blocks with a side length of L n For the insufficient part, blank pixels can be added to the right side and the upper part. The calculation formulas for m2 and n2 are as follows:

[0026]

[0027] Furthermore, for step four, determine the initial grid size S1 of each square block according to the distribution of different geotechnical materials within the square block:

[0028] Among them, if the square block contains blank pixels, the initial grid size S1 is equal to the global minimum grid size L1;

[0029] If the square block does not contain blank pixels, the square block is evenly divided into multiple square grids of the same size. The initial side length of the square grid is the minimum grid size of different geotechnical materials within the square block. If it satisfies that all square grids within the square block contain only one geotechnical material, the initial grid size S1 is equal to the side length of the square grid; if it does not satisfy that all square grids contain only one geotechnical material, the side length of the square grid is halved until all square grids satisfy containing only one geotechnical material.

[0030] Furthermore, for step five, determine the final grid size S2 of each square block according to the following formula to ensure that the final grid size does not exceed the initial grid size, and the ratio of the final grid sizes of adjacent square blocks does not exceed 2:

[0031] S2=min[S g (d)×2^(d / L n)]d = 0, L n , 2L n , 3L n , …, d max

[0032] Among them, d represents the Manhattan distance between the centers of two square blocks, which is equal to the sum of the horizontal and vertical distances between two points; S g (d) represents the minimum initial grid size corresponding to all square blocks that satisfy the Manhattan distance of d from the considered square block; min is the symbol for taking the minimum value; d max is the maximum Manhattan distance to be considered.

[0033] Furthermore, the d max is calculated by the following formula:

[0034] d max = log2(S g (0) / L1) × L n

[0035] Among them, S g (0) is the initial grid size of the considered square block itself.

[0036] Furthermore, for step six, each square block is evenly divided into multiple square units of the same size according to the final grid size, and the transition units and transition edges are identified:

[0037] Each square block is evenly divided into multiple square units of the same size according to the final grid size, then the units corresponding to the blank pixels are removed, and then it is determined whether there are nodes of adjacent units at the midpoints of the four sides of each square unit; if so, the side where it is located is the transition edge, and the unit is the transition unit.

[0038] Furthermore, for step seven, according to the number and relative positions of the transition edges, the transition units are further divided into grids according to the following five cases:

[0039] Case 1:

[0040] The number of transition edges is 1, and the transition unit is divided into an isosceles right triangle and two trapezoids;

[0041] Case 2:

[0042] The number of transition edges is 2, and the transition edges are adjacent, and the transition unit is divided into a square and two trapezoids;

[0043] Case 3:

[0044] The number of transition edges is 2, and the transition edges are not adjacent, and the transition unit is divided into two rectangles;

[0045] Case 4:

[0046] The number of transition edges is 3, and the transition element is divided into three equilateral right-angled triangles and two squares;

[0047] Case 5:

[0048] The number of transition edges is 4, and the transition element is divided into four squares.

[0049] Furthermore, for step seven, triangular elements and / or square elements are supplemented at the surface steep slope:

[0050] In the case of a steep slope on one side, an equilateral right-angled triangular element with a side length of L1 is supplemented at the bottom of the step; if steep slopes appear on both the left and right sides simultaneously, a square element with a side length of L1 is supplemented in the depression; the material of the supplemented element is the same as that of the element directly below it.

[0051] Furthermore, a two-dimensional geological finite element model mesh automatic generation device includes an image acquisition module, a processing module connected to the image acquisition module, and an output module connected to the processing module:

[0052] Among them, the image acquisition module is used to read the two-dimensional geological profile and the shear wave velocity of different geotechnical materials;

[0053] The processing module is used to determine the mesh size of different geotechnical materials in the two-dimensional geological profile according to the shear wave velocity; pixelate the two-dimensional geological profile image according to the global minimum mesh size; evenly divide the pixelated two-dimensional geological profile into multiple square blocks of the same size according to the global maximum mesh size; determine the initial mesh size of each square block according to the distribution of different geotechnical materials within the square block; determine the final mesh size of each square block according to the initial mesh sizes of itself and its surrounding square blocks; evenly divide each square block into multiple square elements of the same size according to the final mesh size, and identify the transition elements and transition edges; further divide the transition elements according to the number and relative positions of the transition edges, and supplement triangular elements and / or square elements at the surface steep slope to ensure a smooth transition of the surface; thus, generate the final two-dimensional geological finite element model mesh.

[0054] The output module is used to automatically generate a file containing all node coordinates and element information, and display the finally generated two-dimensional finite element model.

[0055] Furthermore, a computer program product includes a computer program / instructions, and when the computer program / instructions are executed by a processor, the steps of the above two-dimensional geological finite element model mesh automatic generation method are implemented.

[0056] The beneficial effects of the present invention are reflected in:

[0057] 1) The present invention determines the grid size of different geotechnical materials in a two-dimensional geological profile according to the shear wave velocity of the medium, and pixelates the two-dimensional geological profile image according to the global minimum grid size, laying the foundation for subsequent grid generation;

[0058] 2) The present invention realizes minimizing the number of elements in the finite element model while meeting the requirements of calculation accuracy by dividing the two-dimensional geological profile and determining the local grid size of each part after division;

[0059] 3) The present invention meets the requirements of the finite element method for a two-dimensional spatial discrete grid by identifying and dividing transition elements;

[0060] 4) The present invention reduces the calculation error that appears at the surface steep slope caused by pixelation through the supplementary setting at the surface.

[0061] Other features and advantages of the present invention will be described in the subsequent specification, and will be partially obvious from the specification, or will be understood by implementing the present invention; the main purpose and other advantages of the present invention can be achieved and obtained through the solutions specifically pointed out in the specification. Description of the Drawings

[0062] Figure 1 is the original picture of a two-dimensional geological profile containing two materials;

[0063] Figure 2 is an example diagram of pixelation of a two-dimensional geological profile;

[0064] Figure 3 is an example diagram of dividing a two-dimensional geological profile into square blocks;

[0065] Figure 4 is an example diagram of determining the initial grid size of a square block;

[0066] Figure 5 is an example diagram of the distribution of the initial grid size of a square block;

[0067] Figure 6 is an example diagram of square blocks corresponding to different Manhattan distances;

[0068] Figure 7 is an example diagram of determining the final grid size of a square block;

[0069] Figure 8 is an example diagram of a grid composed of square elements and identified transition elements;

[0070] Figure 9 is the first case of the classification of the division of transition elements;

[0071] Figure 10It is the second classification of the transition unit division;

[0072] Figure 11 It is the third classification of the transition unit division;

[0073] Figure 12 It is the fourth classification of the transition unit division;

[0074] Figure 13 It is the fifth classification of the transition unit division;

[0075] Figure 14 It is the mesh after dividing the transition unit;

[0076] Figure 15 It is the final mesh example diagram after supplementing the unit at the ground surface;

[0077] Figure 16 It is the two-dimensional geological profile of the site where a certain tunnel is located and the partial enlarged view of the automatically generated finite element model mesh;

[0078] Figure 17 It is the comparison diagram and partial enlarged view of the calculation results of the finite element model meshes automatically generated and manually divided by the present invention. Specific embodiments

[0079] Combined with Figures 1 to 15 As shown, this embodiment is described by a two-dimensional geological profile containing two materials, sandy silt and engineering bedrock. The method for automatically generating the two-dimensional geological finite element model mesh is as follows:

[0080] Step 1: Determine the mesh sizes of different geotechnical materials in the two-dimensional geological profile according to the shear wave velocity:

[0081] Sort the different geotechnical materials in the two-dimensional geological profile in ascending order of shear wave velocity, and their shear wave velocities are recorded as V s1 、V s2 、V s3 、...V sn , where n is the number of types of geotechnical materials included in the two-dimensional geological profile. Then, calculate the global minimum mesh size, that is, the mesh size L1 of the first type of geotechnical material, according to the following formula:

[0082] L1 = k1 × V s1 / f max

[0083] f max is the upper limit of the frequency band of interest; k1 is an empirical constant, and its value is 1 / 8 to 1 / 12;

[0084] Next, determine the mesh sizes of other geotechnical materials according to the following formula;

[0085]

[0086] L i and V si respectively represent the grid size and shear wave velocity of the i-th geotechnical material, where i ranges from 2 to n, denotes rounding down; the grid size L of the n-th geotechnical material n is the global maximum grid size.

[0087] In this embodiment, as Figure 1 shown, the shear wave velocities of silty sand (Material 1) and engineering bedrock (Material 2) are V s1 = 200 m / s and V s2 = 900 m / s respectively; k1 takes 1 / 10; f max takes 10 Hz. From the above formula, L1 = 2 m and L2 = 8 m are obtained.

[0088] Step 2: Pixelate the two-dimensional geological profile image according to the global minimum grid size:

[0089] Pixelate the two-dimensional geological profile image at a resolution of m1×n1. The side length corresponding to each pixel is L1, and the corresponding geotechnical material is the geotechnical material corresponding to the pixel center in the original two-dimensional geological profile. The pixels corresponding to the blank areas in the two-dimensional geological profile are called blank pixels, and other pixels are called non-blank pixels.

[0090] The calculation formulas for m1 and n1 are as follows:

[0091]

[0092] W and H respectively represent the width and height of the two-dimensional geological profile, denotes rounding up.

[0093] As Figure 2 shown, the width and height of the two-dimensional geological profile are W = 100 m and H = 45.5 m respectively; m1 = 50 and n1 = 23. Thus, the two-dimensional geological profile image is pixelated at a resolution of 50×23, and the scale corresponding to each pixel is 2 m×2 m.

[0094] Step 3: Evenly divide the pixelated two-dimensional geological profile into multiple square blocks of the same size:

[0095] Supplement one column of blank pixels on both sides of the pixelated two-dimensional geological profile, and then evenly divide it into m2×n2 square blocks with a side length of L n . For the insufficient part, blank pixels can be supplemented to the right and upper parts. The calculation formulas for m2 and n2 are as follows:

[0096]

[0097] In this embodiment, m2 = 13 and n2 = 6. First, a row of blank pixels is supplemented on both sides and above the section in sequence, and then the section is divided into 13×6 square blocks with a side length of 8 meters, as Figure 3 shown.

[0098] Step Four: Determine the initial grid size S1 of each square block according to the distribution of different geotechnical materials in the square block. Among them, if the square block contains blank pixels, the initial grid size S1 is equal to the global minimum grid size L1;

[0099] If the square block does not contain blank pixels, the square block is evenly divided into multiple square grids of the same size. The initial side length of the square grid is taken as the minimum grid size of different geotechnical materials in the square block. If it is satisfied that all square grids in the square block contain only one kind of geotechnical material, the initial grid size S1 is equal to the side length of the square grid; if it is not satisfied that all square grids contain only one kind of geotechnical material, the side length of the square grid is reduced by half until all square grids satisfy containing only one kind of geotechnical material.

[0100] As Figure 4 shown, the square blocks can be divided into four categories, which are respectively:

[0101] Type A: Blocks containing blank pixels

[0102] Type B: Blocks that do not contain blank pixels and contain only Material 1

[0103] Type C: Blocks that do not contain blank pixels and contain only Material 2

[0104] Type D: Blocks that do not contain blank pixels and contain Material 1 and Material 2

[0105] According to Step Four, for Type A: S1 = L1 = 2m

[0106] For Type B and C: S1 is equal to L1 and L2 respectively;

[0107] For Type D: Taking L1 as the initial side length to divide the grid, and satisfying that each grid contains only one kind of geotechnical material, so S1 = L1 = 2m; Thus, the distribution diagram of the initial grid size of the square block is as Figure 5 shown.

[0108] Step Five: Determine the final grid size S2 of each square block according to the following formula, so as to ensure that the final grid size does not exceed the initial grid size, and the ratio of the final grid sizes of adjacent square blocks does not exceed 2:

[0109] S2 = min[S g (d) × 2^(d / L n )] where d = 0, L n , 2L n , 3L n , …, d max

[0110] Among them, d represents the Manhattan distance between the centers of two square blocks, which is equal to the sum of the horizontal and vertical distances between two points; S g (d) represents the minimum initial grid size of all square blocks that satisfy the Manhattan distance of d from the considered square block; min is the symbol for taking the minimum value; d max is the maximum Manhattan distance to be considered.

[0111] Furthermore, the d max is calculated by the following formula:

[0112] d max = log2(S g (0) / L1) × L n

[0113] Among them, S g (0) is the initial grid size of the considered square block itself.

[0114] Figure 6 are the schematic diagrams of the square blocks corresponding to the Manhattan distances of 0, L n、 2L n、 3L n ; and in this embodiment, the grid sizes of 14 square blocks are changed from the initial 8 meters to the final 4 meters to ensure that the ratio of the final grid sizes of adjacent square blocks does not exceed 2, as Figure 7 shown.

[0115] Step Six: Evenly divide each square block into multiple square units of the same size according to the final grid size, and identify the transition units and transition edges:

[0116] Evenly divide each square block into multiple square units of the same size according to the final grid size, then remove the units corresponding to the blank pixels, and then determine whether there are nodes of adjacent units at the midpoints of the four sides of each square unit; if so, the side where it is located is the transition edge, and the unit is the transition unit. After the transition units are identified, as Figure 8 shown.

[0117] In Step Seven, as Figure 14 shown, classify the transition units and perform further grid division. Among them, as Figures 9 to 13As shown, according to the number and relative positions of the transition edges, the transition elements are further meshed according to the following five cases:

[0118] Case 1:

[0119] The number of transition edges is 1, and the transition element is divided into an isosceles right triangle and two trapezoids;

[0120] Case 2:

[0121] The number of transition edges is 2, and the transition edges are adjacent. The transition element is divided into a square and two trapezoids;

[0122] Case 3:

[0123] The number of transition edges is 2, and the transition edges are not adjacent. The transition element is divided into two rectangles;

[0124] Case 4:

[0125] The number of transition edges is 3, and the transition element is divided into three isosceles right triangles and two squares;

[0126] Case 5:

[0127] The number of transition edges is 4, and the transition element is divided into four squares.

[0128] In addition, triangular elements and / or square elements are supplemented at the surface steep slopes: in the case of a steep slope on one side, an isosceles right triangle element with a side length of L1 is supplemented at the bottom of the step; if steep slopes appear on both the left and right sides, a square element with a side length of L1 is supplemented in the depression; the material of the supplemented element is the same as that of the element directly below it. In this embodiment, isosceles right triangle elements are supplemented at the surface steep slopes to ensure a smooth transition of the surface; thus, the final two-dimensional finite element mesh is obtained, as Figure 15 shown.

[0129] As Figure 16 and Figure 17 shown, in this application, a two-dimensional geological profile of the site where a certain tunnel project is located is selected as an example. The length of this two-dimensional geological profile is 6000 meters, the maximum surface elevation is 81 meters, and the two-dimensional geological profile includes a total of six materials, namely clay, clayey sand, gravelly clayey sand, silt, sand, and bedrock, and the shear wave velocities are 100 m / s, 190 m / s, 220 m / s, 270 m / s, 380 m / s, and 1000 m / s respectively. k1 and f maxTake 1 / 10 and 10 Hz respectively. Then, through Step 1, the grid sizes of these six materials can be determined to be 1 m, 1 m, 2 m, 2 m, 2 m, and 8 m respectively. Through the calculation in Step 2, the resolution of the pixelated profile can be obtained as 6000×81. Through the calculation in Step 3, the pixelated profile can be divided into 751×11 square blocks with a side length of 8 m. After subsequent processing steps, the grid of the final two-dimensional finite element model can be generated. This model has a total of 233882 elements, including 5605 triangular elements and 228577 quadrilateral elements. The finite element grid manually divided by ANSA software has a total of 306199 elements, including 4882 triangular elements and 301317 quadrilateral elements. The material structure adopts a viscoelastic constitutive model, the boundary condition is vertical constraint, and the ground motion uses the ground motion record in the east-west direction at the bedrock underground of the KSRH01 station in Kitami, Japan during the magnitude 5.0 earthquake on June 4, 2015 and is adjusted to 1 m / s 2 ; Through comparison, it can be seen that the peak ground accelerations obtained from the grids divided by the two methods are basically the same, and the average absolute relative error is slightly lower than 5%. Thus, it can be seen that the method proposed in the present invention can significantly reduce the time spent on preprocessing and numerical calculation on the premise of ensuring the accuracy of the calculation results.

[0130] In addition, in this embodiment, the two-dimensional geological finite element model grid automatic generation device includes an image acquisition module, a processing module connected to the image acquisition module, and an output module connected to the processing module:

[0131] Among them, the image acquisition module is used to read the two-dimensional geological profile and the shear wave velocity of different geotechnical materials;

[0132] The processing module is used to determine the grid sizes of different geotechnical materials in the two-dimensional geological profile according to the shear wave velocity; pixelate the two-dimensional geological profile image according to the global minimum grid size; evenly divide the pixelated two-dimensional geological profile into multiple square blocks of the same size according to the global maximum grid size; determine the initial grid size of each square block according to the distribution of different geotechnical materials within the square block; determine the final grid size of each square block according to the initial grid sizes of itself and its surrounding square blocks; evenly divide each square block into multiple square units of the same size according to the final grid size, and identify the transition units and transition edges; further divide the transition units according to the number and relative positions of the transition edges, and supplement triangular units and / or square units at the surface steep cliffs to ensure a smooth transition of the surface; thereby, generate the grid of the final two-dimensional geological finite element model.

[0133] The output module is used to automatically generate a file containing all node coordinates and element information, and display the finally generated two-dimensional finite element model.

[0134] The image acquisition module of the present application can read and convert images in formats such as bmp, jpg, png, tif, gif, pcx, tga, etc., and convert them into the formats required by the processing module; the processing module is formed by program modules in programming languages such as Java, Smalltalk, C++, etc., and it can execute the processing method of the present application. The output module includes the visual display and editing of each node of the processing module.

[0135] In this embodiment, computer program code for performing the operations of the present invention can be written in one or more programming languages or combinations thereof. The programming languages include object-oriented programming languages such as Java, Smalltalk, C++, and also include conventional procedural programming languages such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, executed as an independent software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computer (for example, by using an Internet service provider to connect through the Internet).

[0136] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for automatically generating a two-dimensional geological finite element model grid, characterized in that: The specific steps are as follows: Step 1: Determine the grid size of different geotechnical materials in the two-dimensional geological profile according to the shear wave velocity; Step 2: pixelate the two-dimensional geological profile according to the global minimum grid size; Step 3: Evenly divide the pixelated two-dimensional geological profile into multiple square blocks of the same size according to the global maximum grid size; Step 4: Determine the initial grid size S1 of each square block according to the distribution of different geotechnical materials in the square block; wherein, if the square block contains blank pixels, the initial grid size S1 is equal to the global minimum grid size L1; If there are no blank pixels in the square block, the square block is evenly divided into multiple square grids of the same size. The initial side length of the square grid is the minimum grid size of different geotechnical materials in the square block. If all square grids in the square block contain only one type of geotechnical material, the initial grid size S1 is equal to the side length of the square grid; if not all square grids contain only one type of geotechnical material, the side length of the square grid is reduced by half until all square grids contain only one type of geotechnical material. Step 5: Determine the final grid size S2 of each square block according to the initial grid size of itself and the surrounding square blocks, so as to ensure that the final grid size does not exceed the initial grid size and the ratio of the final grid sizes of adjacent square blocks does not exceed 2; Step 6: Divide each square block evenly into multiple square units of the same size according to the final grid size, and identify transition units and transition edges; Step 7: Further mesh the transition unit according to the number and relative position of the transition edges, and add triangular units and / or square units at the steep surface to ensure a smooth transition of the surface; thereby, the final two-dimensional geological finite element model mesh is generated.

2. The method for automatically generating a two-dimensional geological finite element model grid according to claim 1, characterized in that: For step 1, the mesh size of different geotechnical materials in the two-dimensional geological profile is determined according to the shear wave velocity: The different rock and soil materials in the two-dimensional geological profile are sorted in order from small to large shear wave velocity, and their shear wave velocities are denoted as V s1 、V s2 、V s3 ,...V sn , where n is the number of geomaterial types contained in the profile. Then, the global minimum grid size, i.e., the grid size L1 of the first geomaterial, is calculated according to the following formula: L1=k1×V s1 / f max f max is the upper limit of the frequency band of interest; k1 is an empirical constant with a value of 1 / 8 to 1 / 12; Next, determine the mesh size for other geotechnical materials according to the following formula; L i and V si Respectively represent the grid size and shear wave velocity of the i-th geomaterial, i ranges from 2 to n, represents rounding down; the grid size L of the nth geotechnical material n This is the global maximum grid size.

3. The method for automatically generating a two-dimensional geological finite element model grid according to claim 1, characterized in that: For step 2, pixelate the 2D geological profile according to the global minimum grid size: The two-dimensional geological profile is pixelated according to the resolution of m1×n1. The side length of each pixel is L1, and the corresponding material is the corresponding material in the original two-dimensional geological profile at the center of the pixel; the pixels corresponding to the blank space in the two-dimensional geological profile are called blank pixels, and the other pixels are called non-blank pixels; The calculation formulas for m1 and n1 are as follows: W and H represent the width and height of the two-dimensional geological profile, respectively. Indicates rounding up.

4. The method for automatically generating a two-dimensional geological finite element model grid according to claim 1, characterized in that: For step 3, the pixelated two-dimensional geological profile is evenly divided into multiple square blocks of the same size according to the global maximum grid size: a column of blank pixels is added on both sides of the pixelated two-dimensional geological profile, and then it is evenly divided into m2×n2 square blocks with a side length of L n The insufficient part can be supplemented with blank pixels on the right and top, where the calculation formulas of m2 and n2 are as follows:

5. The method for automatically generating a two-dimensional geological finite element model grid according to claim 1, characterized in that: In step 5, the final grid size S2 of each square block is determined according to the initial grid size of itself and the surrounding square blocks according to the following formula, so as to ensure that the final grid size does not exceed the initial grid size and the ratio of the final grid sizes of adjacent square blocks does not exceed 2: <h2 style=";text-align:left;direction:ltr">S2 = min[S<h2 style=";text-align:left;direction:ltr"> g <h2 style=";text-align:left;direction:ltr"> (d)×2^(d / L<h2 style=";text-align:left;direction:ltr"> n <h2 style=";text-align:left;direction:ltr"> )]d=0,L<h2 style=";text-align:left;direction:ltr"> n <h2 style=";text-align:left;direction:ltr"> 2L<h2 style=";text-align:left;direction:ltr"> n <h2 style=";text-align:left;direction:ltr"> 3L<h2 style=";text-align:left;direction:ltr"> n <h2 style=";text-align:left;direction:ltr"> ,…,d<h2 style=";text-align:left;direction:ltr"> max Where d represents the Manhattan distance between the centers of two square blocks, which is equal to the sum of the horizontal and vertical distances between the two points; S g (d) represents the minimum initial grid size corresponding to all square blocks with a Manhattan distance d between the square blocks under consideration; min is the symbol for taking the minimum value; d max is the maximum Manhattan distance to be considered.

6. The method for automatically generating a two-dimensional geological finite element model grid according to claim 5, characterized in that: The d max Calculated by the following formula: d max =log2(S g (0) / L1)×L n Among them, S g (0) is the initial grid size of the considered square block itself.

7. The method for automatically generating a two-dimensional geological finite element model grid according to claim 1, characterized in that: In step 6, each square block is evenly divided into multiple square units of the same size according to the final grid size, and transition units and transition edges are identified: According to the final grid size, each square block is evenly divided into multiple square units of the same size, and then the units corresponding to the blank pixels are removed. It is then determined whether there are nodes of adjacent units at the midpoints of the four sides of each square unit; if so, the side where it is located is a transition side, and the unit is a transition unit.

8. The method for automatically generating a two-dimensional geological finite element model grid according to claim 1, characterized in that: In step 7, according to the number and relative position of the transition edges, the transition unit is further meshed according to the following five cases: Case 1: The number of transition edges is 1, and the transition unit is divided into an equilateral right triangle and two trapezoids; Case 2: The number of transition edges is 2, and the transition edges are adjacent. The transition unit is divided into a square and two trapezoids; Case 3: The number of transition edges is 2, and the transition edges are not adjacent, and the transition unit is divided into two rectangles; Case 4: The number of transition edges is 3, and the transition unit is divided into three equilateral right triangles and two squares; Case 5: The number of transition edges is 4, and the transition unit is divided into four squares.

9. The method for automatically generating a two-dimensional geological finite element model grid according to claim 1, characterized in that: For step 7, add triangle units and / or square units at the steep slopes of the ground: If a steep step appears on one side, an equilateral right triangle unit with a side length of L1 is added at the bottom of the step; if steep steps appear on both sides at the same time, a square unit with a side length of L1 is added in the depression; the material of the added unit is the same as that of the unit directly below it.

10. A two-dimensional geological finite element model grid automatic generation device, characterized in that: It includes an image acquisition module, a processing module connected to the image acquisition module, and an output module connected to the processing module: The image acquisition module is used to read the two-dimensional geological profile and the shear wave velocity of different geotechnical materials; The processing module is used to determine the grid size of different geotechnical materials in the two-dimensional geological profile according to the shear wave velocity; pixelate the two-dimensional geological profile according to the global minimum grid size; evenly divide the pixelated two-dimensional geological profile into a plurality of square blocks of the same size according to the global maximum grid size; determine the initial grid size of each square block according to the distribution of different geotechnical materials in the square block; wherein, if the square block contains blank pixels, the initial grid size is equal to the global minimum grid size; if the square block does not contain blank pixels, the square block is evenly divided into a plurality of square grids of the same size, and the initial side length of the square grid is the minimum grid size of different geotechnical materials in the square block, if all square grids in the square block are satisfied If all square grids contain only one kind of geotechnical material, the initial grid size is equal to the side length of the square grid; if not all square grids contain only one kind of geotechnical material, the side length of the square grid is reduced by half until all square grids contain only one kind of geotechnical material; according to the initial grid size of itself and the surrounding square blocks, the final grid size of each square block is determined; according to the final grid size, each square block is evenly divided into a plurality of square units of the same size, and the transition units and transition edges are identified; according to the number and relative positions of the transition edges, the transition units are further gridded, and triangular units and / or square units are supplemented at the steep slopes of the surface to ensure a smooth transition of the surface; thereby, the final two-dimensional geological finite element model grid is generated; The output module is used to automatically generate files containing all node coordinates and unit information, and display the final generated two-dimensional finite element model.

11. A computer program product comprising a computer program / instructions, characterized in that: When the computer program / instructions are executed by a processor, the method according to any one of claims 1 to 9 is implemented.

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