Method for generating random three-dimensional irregular concrete aggregate

Abstract

A method for generating random three-dimensional irregular concrete aggregate comprises the following steps: S1, performing three-dimensional grid division on a cubic area in which aggregate is not generated, and assigning values to all grid areas; s2, randomly generating a plurality of ellipsoids in the three-dimensional grid region; s3, generating a plurality of uniformly distributed points on the ellipsoid surface, randomly selecting a part of the points as vertexes of an irregular polyhedron, and generating the irregular polyhedron; s4, optimizing the irregular polyhedron to improve the calculation efficiency and precision; and S5, aiming at the obtained irregular polyhedron, generating a bonding interface corresponding to the irregular polyhedron. According to the method for generating the random three-dimensional irregular concrete aggregate, provided by the invention, the generation speed of a single new aggregate can be gradually increased along with the increase of the number of the generated aggregate, the newly generated aggregate can be effectively prevented from overlapping with the existing aggregate, and the calculation efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the field of concrete microscopic numerical simulation, and in particular relates to a method for generating random three-dimensional irregular concrete aggregate. Background Art

[0002] Concrete has the advantages of high strength, good durability and low cost. It is currently the most widely used building material. At the microscopic scale, concrete can be regarded as a multiphase composite material composed of aggregate, mortar and interface transition zone. With the rapid development of computer technology, numerical simulation has been widely used in the study of concrete mesomechanics. Through concrete mesoscopic numerical simulation, we can conduct in-depth research on the interaction and damage mechanism of each component of concrete, understand the influence of the material properties of each component, aggregate distribution, pore structure, etc. in concrete on its macroscopic mechanical properties, and replace traditional test methods to a certain extent, thereby providing an effective supplement for the performance evaluation and structural design of concrete materials. Therefore, the simulation of concrete mesoscopic numerical values ​​is of great theoretical and practical significance.

[0003] The establishment of random aggregate model of concrete is the basis of mesoscopic numerical simulation. At present, many scholars at home and abroad have conducted research on the modeling of random aggregate model of concrete. Existing research mainly models random aggregate model of concrete based on MATLAB, FORTRAN, C+, PYTHON, etc., and then imports the established model into commercial finite element software such as ANSYS and ABAQUS for numerical simulation; however, this type of method requires the established random aggregate model of concrete to be converted between different software, which has the disadvantages of large workload, cumbersome operation and weak feasibility. Some scholars have also conducted secondary development of ANSYS based on APDL language and compiled a program for generating random aggregate model of concrete, which avoids importing the model from different software into finite element software for calculation; however, most of these methods are only suitable for the establishment of simple two-dimensional random aggregate model of concrete, and it is difficult to successfully apply it to the three-dimensional random aggregate modeling with a large number of aggregates and complex models.

[0004] Since traditional methods usually need to continuously judge the distance relationship between newly generated aggregates and existing aggregates, as new aggregates are continuously generated, the algorithm may become redundant, resulting in a significant decrease in efficiency when new aggregates are continuously generated in the later stage. Therefore, in order to improve the calculation efficiency, a new algorithm is needed that gradually increases the generation speed of a single new aggregate as the number of generated aggregates increases. The present invention solves this technical problem. Summary of the invention

[0005] The present invention provides a method for generating random three-dimensional irregular concrete aggregates, which can gradually increase the generation speed of a single new aggregate as the number of generated aggregates increases, and can also effectively avoid the overlap of the newly generated aggregates with the existing aggregates, thereby improving the calculation efficiency.

[0006] A method for generating random three-dimensional irregular concrete aggregates comprises the following steps:

[0007] S1. Perform three-dimensional meshing on the area where no aggregate is generated, divide it into a number of cubes, and assign values ​​to all mesh areas;

[0008] S2, randomly generate several ellipsoids in the three-dimensional grid area;

[0009] S3, generating a number of evenly distributed points on the surface of the ellipsoid, randomly selecting some of the points as vertices of an irregular polyhedron, and generating an irregular polyhedron;

[0010] S4, optimizing irregular polyhedrons to improve computational efficiency and accuracy;

[0011] S5. For the obtained irregular polyhedron, generate the corresponding bonding interface.

[0012] Furthermore, the step S1 includes the following steps:

[0013] S11. Assume that the calculation area before the first generation of aggregate is filled with cement mortar, add a layer of boundary around the calculation area as a boundary condition, and assign it a value of 0;

[0014] S12, dividing the calculation area into a plurality of three-dimensional grids, and treating the grids containing cement mortar as cement mortar grids;

[0015] S13, assigning an initial value of d=0.5 to all cement mortar grids, and using the value of d as the radius of the maximum inscribed sphere;

[0016] S15. If all grids within a distance of d+0.5 from a cement mortar grid have cement mortar, then the d value of this cement mortar grid is increased by 0.5, otherwise the d value remains unchanged;

[0017] S16, repeat the above process until the d values ​​of all cement mortar grids are calculated, and the d value distribution of the calculation area can be obtained;

[0018] S17, the maximum value d max Indicates the maximum inscribed sphere radius, and the semi-major axis of the aggregate generated subsequently is no greater than d max .

[0019] Furthermore, the step S15 includes the following steps:

[0020] S151, the coordinates of the grid to be determined are expressed as (i, j, k), where i represents the horizontal coordinate of the grid to be determined, j represents the vertical coordinate of the grid to be determined, and k represents the vertical coordinate of the grid to be determined;

[0021] S152, half of the side length of the cubic grid area of ​​the aggregate to be generated is expressed as D, the initial value of D is 1, and the above cubic area is expressed as:

[0022] (iD≤I≤i+D; jD≤J≤j+D; kD≤K≤k+D);

[0023] Among them, I, J, and K are the coordinates of the cube in the x, y, and z directions respectively;

[0024] S153, the distance between the grid to be determined and the three-dimensional grid in the cube area is expressed as dist. If all grids satisfying dist≤d+0.5 are filled with cement mortar, the d value of the grid to be determined is increased by 0.5, and the D value of the cube area is increased by 1.

[0025] Furthermore, the step S2 includes the following steps:

[0026] S21. Randomly select the major and minor semi-axes a and b of the ellipse, find the cubic regions where the dmax value is greater than or equal to a, select the center point (h, k) of the ellipse in these regions, and randomly select the inclination angle of the ellipse

[0027] S22, the ellipse polar coordinate parameter equation is:

[0028]

[0029] Among them, (rx, ry, rz) are the coordinates of the center of the ellipsoid, a, b and c are the semi-axis lengths of the ellipsoid on the x-axis, y-axis and z-axis respectively, and θ is the polar angle. is the azimuth;

[0030] S23. The matrix Rx of the ellipsoid rotating around the x-axis is:

[0031]

[0032] S24, matrix Ry rotated around the y axis:

[0033]

[0034] S25, matrix Rz rotated around the z axis:

[0035]

[0036] S26. The rotation matrix of the ellipsoid as a whole is:

[0037] R=R x R y R z

[0038] S27. The coordinates (x, y, z) of any point in the ellipsoid are rotated by the rotation matrix R to obtain new coordinates (x', y', z'). The specific expression is as follows:

[0039]

[0040] Furthermore, the step S3 includes the following steps:

[0041] S31, generating 2N points on the surface of the ellipsoid, and randomly selecting N of the points to generate an irregular polyhedron;

[0042] S32. For the i-th point (i∈[1,N]) generated on the ellipsoid surface, its polar angle and azimuth are expressed as:

[0043]

[0044] S33. The expression for mapping a point to the surface of an ellipsoid is:

[0045]

[0046] S34, obtaining three-dimensional irregular aggregate.

[0047] Further, the step S4 includes the following steps:

[0048] S41. For the obtained irregular polyhedron, three aspects of optimization need to be performed: flattening, removing triangular faces with very short sides, and removing triangular faces with extremely small internal angles;

[0049] S42. In order to avoid obtaining flat aggregates, sphericity is used to describe the flattening degree of the aggregates. When the sphericity of the generated aggregate exceeds the set minimum sphericity, the corresponding aggregate can be generated. The sphericity B is expressed as:

[0050]

[0051] Among them, L l , L i , L s are the longest, middle and shortest dimensions respectively;

[0052] S43, optimize the edge length, calculate the length of each edge of the irregular aggregate, when the shortest edge in a triangular plane of the aggregate is less than the preset minimum length L min , then remove one vertex of the edge and continue to optimize the new aggregate determined by the remaining vertices until all edge lengths are greater than Lmin ;

[0053] S44, performing internal angle optimization, calculating the internal angle of each triangular face of the aggregate, when the minimum internal angle of one of the triangular faces is less than the preset value β, comparing the sizes of the other two internal angles, removing the vertex corresponding to the larger internal angle, and continuing to optimize the new aggregate formed by the remaining vertices until all internal angles are greater than β;

[0054] S45. After geometric optimization of all aggregates, several aggregates with ideal shapes are obtained.

[0055] Furthermore, the step S5 includes the following steps:

[0056] S51. Calculate the center of gravity of the polyhedron. The center of gravity is the average value of all vertex coordinates:

[0057]

[0058] Among them, (centroid x , centroid y , centroid z ) is the barycentric coordinate, N is the number of vertices, X i ,Y i ,Z i are the coordinates of the i-th vertex.

[0059] S52. Calculate the distance d from each vertex to the center of gravity i :

[0060]

[0061] S53. Assuming that the thickness of the bonding interface is l, the distance from the new vertex to the center of gravity after shrinkage is:

[0062] d' i =d i -l

[0063] S54, the new vertex (X' i , Y' i , Z' i ) coordinates are:

[0064]

[0065]

[0066] The technical effects of the present invention are as follows:

[0067] (1) This method can calculate the area in the region where ellipsoidal aggregates can be generated by assigning values ​​to the three-dimensional grid area and calculating the d value, so that new aggregates can be generated in the area not occupied by the ellipsoidal aggregates. In addition, since the calculation process of the d value is related to whether the surrounding area is cement mortar, when the area is cement mortar but not aggregates, it can be generated. Therefore, this scheme saves the amount of calculation through the above method, does not need to calculate the size of the area occupied by the aggregate, reduces the possibility of algorithm redundancy, saves calculation time, and improves calculation efficiency.

[0068] (2) Since this method only needs to calculate the cement mortar area, the area occupied by the generated aggregate will be excluded from the subsequent calculation of the generated aggregate, which can effectively avoid the overlap of the newly generated aggregate with the existing aggregate. This not only ensures that the generated aggregate does not overlap as a whole, but also saves the amount of calculation, greatly improving the calculation efficiency;

[0069] (3) This scheme generates a number of points on the surface of the ellipsoid as the vertices of the irregular polygon, and randomly selects a portion of the points as the vertices of the irregular polyhedron to generate the irregular polyhedron, thereby ensuring the randomness of the generated polyhedron shape;

[0070] (4) This scheme can optimize the sphericity, side length and internal angle of irregular polyhedral aggregates. In this way, not only can polyhedral aggregates with ideal shapes and no overlap be generated, but also the computational efficiency and accuracy of the simulation process can be improved;

[0071] (5) After simulating the shape of the irregular polyhedron aggregate, this scheme will generate the bonding interface of the aggregate by shrinking, so that when generating the bonding interface, it will be generated within the originally simulated polyhedron, and will not occupy more additional area, thereby ensuring that there is enough space to generate the aggregate and the bonding interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 It is a flowchart of the present invention.

[0073] Figure 2 It is a flowchart of the d value distribution in the present invention.

[0074] Figure 3 It is a schematic diagram of a simple model of a cubic region in the present invention.

[0075] Figure 4 It is a schematic diagram of the d value distribution of cement mortar on the grid in the present invention.

[0076] Figure 5 It is a comparison diagram of the edge length optimization of the polyhedron in the present invention.

[0077] Figure 6 It is a comparison diagram of the internal angle optimization of the polyhedron in the present invention.

[0078] Figure 7 Schematic diagram of the bonding interface in the present invention.

[0079] Figure 8 A line graph showing the amount of aggregate produced versus the time required. DETAILED DESCRIPTION

[0080] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments and drawings.

[0081] See also Figure 1-Figure 8 , a method for generating random three-dimensional irregular concrete aggregates, comprising the following steps:

[0082] S1. Perform three-dimensional meshing on the area where no aggregate is generated, divide it into a number of cubes, and assign values ​​to all mesh areas;

[0083] S2, randomly generate several ellipsoids in the three-dimensional grid area;

[0084] S3, generating a number of evenly distributed points on the surface of the ellipsoid, randomly selecting some of the points as vertices of an irregular polyhedron, and generating an irregular polyhedron;

[0085] S4, optimizing irregular polyhedrons to improve computational efficiency and accuracy;

[0086] S5. For the obtained irregular polyhedron, generate the corresponding bonding interface.

[0087] Further, step S1 includes the following steps:

[0088] S11. Assume that the calculation area before the first generation of aggregate is filled with cement mortar, add a layer of boundary around the calculation area as a boundary condition, and assign it a value of 0;

[0089] S12, dividing the calculation area into a plurality of three-dimensional grids, and treating the grids containing cement mortar as cement mortar grids;

[0090] S13, assigning an initial value of d=0.5 to all cement mortar grids, and using the value of d as the radius of the maximum inscribed sphere, that is, the value of each grid represents the radius of the maximum aggregate that can be stored when the point is used as the center of the aggregate;

[0091] S15. If all grids within a distance of d+0.5 from a cement mortar grid have cement mortar, then the d value of this cement mortar grid is increased by 0.5, otherwise the d value remains unchanged;

[0092] S16, repeat the above process until the d values ​​of all cement mortar grids are calculated, and the d value distribution of the calculation area can be obtained;

[0093] S17, the maximum value d max Indicates the maximum inscribed sphere radius, and the semi-major axis of the aggregate generated subsequently is no greater than d max .

[0094] Further, step S15 includes the following steps:

[0095] S151, the coordinates of the grid to be determined are expressed as (i, j, k), where i represents the horizontal coordinate of the grid to be determined, j represents the vertical coordinate of the grid to be determined, and k represents the vertical coordinate of the grid to be determined;

[0096] S152, half of the side length of the cubic grid area of ​​the aggregate to be generated is expressed as D, the initial value of D is 1, and the above cubic area is expressed as:

[0097] (iD≤I≤i+D; jD≤J≤j+D; kD≤K≤k+D);

[0098] Among them, I, J, and K are the coordinates of the cube in the x, y, and z directions respectively;

[0099] S153. The distance between the grid to be determined and the three-dimensional grid in the cube area is expressed as dist. If all grids satisfying dist≤d+0.5 contain cement mortar, the d value of the grid to be determined is increased by 0.5, and the D value of the cube area is increased by 1.

[0100] The calculation formula of dist in this scheme is:

[0101]

[0102] Further, step S2 includes the following steps:

[0103] S21. Randomly select the major and minor semi-axes a and b of the ellipse, find the cubic regions where the dmax value is greater than or equal to a, select the center point (h, k) of the ellipse in these regions, and randomly select the inclination angle of the ellipse

[0104] S22, the ellipse polar coordinate parameter equation is:

[0105]

[0106] Among them, (rx, ry, rz) are the coordinates of the center of the ellipsoid, a, b and c are the semi-axis lengths of the ellipsoid on the x-axis, y-axis and z-axis respectively, and θ is the polar angle. is the azimuth;

[0107] S23. The matrix Rx of the ellipsoid rotating around the x-axis is:

[0108]

[0109] S24, matrix Ry rotated around the y axis:

[0110]

[0111] S25, matrix Rz rotated around the z axis:

[0112]

[0113] S26. The rotation matrix of the ellipsoid as a whole is:

[0114] R=R x R y R z

[0115] S27. The coordinates (x, y, z) of any point in the ellipsoid are rotated by the rotation matrix R to obtain new coordinates (x', y', z'). The specific expression is as follows:

[0116]

[0117] Further, step S3 includes the following steps:

[0118] S31, generating 2N points on the surface of the ellipsoid, and randomly selecting N of the points to generate an irregular polyhedron;

[0119] S32. For the i-th point (i∈[1,N]) generated on the ellipsoid surface, its polar angle and azimuth are expressed as:

[0120]

[0121] S33. The expression for mapping a point to the surface of an ellipsoid is:

[0122]

[0123] S34, obtaining three-dimensional irregular aggregate.

[0124] Preferably, an aggregate generation strategy of first placing large-size aggregates and then placing small-size aggregates can be adopted, which can better fill the gaps between coarse aggregates and improve the density of concrete. This can ensure the uniform distribution of various components in the concrete and improve the workability and workability of the concrete. The small-size aggregates added subsequently can further fill the gaps, reduce the void ratio, and improve the density and durability of the concrete.

[0125] The Golden Section Spiral method has been widely used and verified in science and engineering, and has a good theoretical basis and practical effect. Because the points it generates have good uniformity and distribution characteristics, the Golden Section Spiral method is widely used in computer graphics, scientific computing, materials science and other fields. Its theoretical basis is solid and has been verified and applied by many studies. The Golden Section Spiral method is easy to expand and can generate points on spheres, ellipsoids and other geometric bodies. Its application is not limited to specific geometric shapes. The Golden Section Spiral method is simple and effective, and can generate large-scale point sets with a small amount of calculation. It avoids complex iteration and optimization processes. The Golden Section Spiral method can generate uniformly distributed points on a sphere or ellipsoid. Uniform distribution means that the intervals between points are as equal as possible, avoiding clustering and sparse areas.

[0126] In order to avoid the occurrence of colinear or coplanar situations, this scheme uses the Golden Section Spiral method to generate 2N evenly distributed points on the surface of the ellipsoid, and randomly selects N of these points to generate an irregular polyhedron, so as to ensure the randomness of the generated polyhedron shape.

[0127] Furthermore, although irregular aggregates can be generated using the above method, the generated aggregates need to be optimized before they can be used for numerical calculations. Step S4 includes the following steps:

[0128] S41. For the obtained irregular polyhedron, three aspects of optimization need to be performed: flattening, removing triangular faces with very short sides, and removing triangular faces with extremely small internal angles;

[0129] S42. In order to avoid obtaining flat aggregates, sphericity is used to describe the flattening degree of the aggregates. When the sphericity of the generated aggregate exceeds the set minimum sphericity, the corresponding aggregate can be generated. The sphericity B is expressed as:

[0130]

[0131] Among them, L l , L i , L s are the longest, middle and shortest dimensions respectively;

[0132] This paper uses sphericity to describe the degree of flattening of aggregates;

[0133] S43, optimize the edge length, calculate the length of each edge of the irregular aggregate, when the shortest edge in a triangular plane of the aggregate is less than the preset minimum length Lmin , then remove one vertex of the edge and continue to optimize the new aggregate determined by the remaining vertices until all edge lengths are greater than L min ;

[0134] See also Figure 5 , Figure 5 The left picture in the middle is a schematic diagram of the aggregate before optimization, and the right picture is a schematic diagram after optimization. It can be seen that the triangle where one of the vertices is located is optimized. Preferably, L in this scheme min is set to one-tenth the maximum edge length of the aggregate;

[0135] S44, perform internal angle optimization, calculate the internal angle of each triangular face of the aggregate, and when the minimum internal angle of one of the triangular faces is less than the preset value β, compare the sizes of the other two internal angles, remove the vertex corresponding to the larger internal angle, and continue to optimize the new aggregate formed by the remaining vertices until all internal angles are greater than β, and β in this embodiment is 10°;

[0136] See also Figure 6 , Figure 6 The middle left picture is a schematic diagram of the aggregate before optimization, and the right picture is a schematic diagram after optimization. It can be seen that one of the triangles has been optimized away;

[0137] S45. After geometric optimization of all aggregates, several aggregates with ideal shapes are obtained.

[0138] The above contents respectively optimize the irregular polyhedron in three aspects: flattening, removing triangular faces with very short edges, and removing triangular faces with extremely small internal angles.

[0139] Flat polyhedrons, especially those with complex geometric shapes, may have overlapping or crossing vertices or edges, or the faces of the polyhedron may intersect or overlap on the plane. Aggregates with very short edges or extremely small internal angles will have an adverse effect on the computational efficiency and accuracy of numerical simulations. Therefore, this scheme has been optimized in these aspects.

[0140] Further, step S5 includes the following steps:

[0141] S51. Calculate the center of gravity of the polyhedron. The center of gravity is the average value of all vertex coordinates:

[0142]

[0143] Among them, (centroid x , centroid y , centroid z ) is the barycentric coordinate, N is the number of vertices, X i ,Y i ,Zi are the coordinates of the i-th vertex.

[0144] S52. Calculate the distance d from each vertex to the center of gravity i :

[0145]

[0146] S53. Assuming that the thickness of the bonding interface is l, the distance from the new vertex to the center of gravity after shrinkage is:

[0147] d' i =d i -l

[0148] S54, the new vertex (X' i , Y' i , Z' i ) coordinates are:

[0149]

[0150] Figure 7 The vertices of the larger polyhedron are the original vertices of the polyhedron, the vertices of the smaller polyhedron are the vertices of the indented polyhedron, and the part between the two polyhedrons is the bonding interface.

[0151] The working principle of the present invention is as follows:

[0152] First, the area without aggregate is divided into a number of cube-shaped three-dimensional grids, and the area is assigned a value. Then, the d value is calculated to calculate the d value of each grid. The d value represents the maximum aggregate radius that can be stored when the grid is used as the center of the aggregate, so as to facilitate the subsequent calculation of the ellipsoid.

[0153] Then, the ellipsoid with a larger major semi-axis b can be generated first. It is necessary to find the area where the d value is greater than or equal to the minor semi-axis a, and then select the center point of the ellipse in these areas, and then generate the ellipsoid. After generating several ellipsoids, the Golden Section Spiral method can be used to generate 2N evenly distributed points on the surface of the ellipsoid, and N of them are randomly selected as vertices to generate irregular polyhedrons, so as to ensure the randomness of the generated polyhedron shape. After the irregular polyhedron aggregate is generated, it needs to be optimized, specifically for the flattening of the polyhedron, the removal of triangular faces with very short sides, and the removal of triangular faces with extremely small internal angles. Through these three optimization methods, an ideal-shaped, non-overlapping irregular polyhedron aggregate is obtained, and then the corresponding bonding interface is generated by shrinking, thereby completing the generation of the aggregate.

[0154] The above embodiments are only preferred embodiments of the present invention. Those skilled in the art can derive other embodiments from the above embodiments without creative work. Therefore, this application protects not only the above embodiments, but also the scope consistent with the principles and features of this application.

Claims

1. A method for generating random three-dimensional irregular concrete aggregates, characterized in that: The following steps are involved: S1. Perform three-dimensional meshing on the area where no aggregate is generated, divide it into a number of cubes, and assign values ​​to all mesh areas; S2, randomly generate several ellipsoids in the three-dimensional grid area; S3, generating a number of evenly distributed points on the surface of the ellipsoid, randomly selecting some of the points as vertices of an irregular polyhedron, and generating an irregular polyhedron; S4, optimizing irregular polyhedrons to improve computational efficiency and accuracy; S5. For the obtained irregular polyhedron, generate the corresponding bonding interface.

2. The method for generating random three-dimensional irregular concrete aggregate according to claim 1, characterized in that: The step S1 comprises the following steps: S11. Assume that the calculation area before the first generation of aggregate is filled with cement mortar, add a layer of boundary around the calculation area as a boundary condition, and assign it a value of 0; S12, dividing the calculation area into a plurality of three-dimensional grids, and treating the grids containing cement mortar as cement mortar grids; S13, assigning an initial value of d=0.5 to all cement mortar grids, and using the value of d as the radius of the maximum inscribed sphere; S15. If all grids within a distance of d+0.5 from a cement mortar grid have cement mortar, then the d value of this cement mortar grid is increased by 0.5, otherwise the d value remains unchanged; S16, repeat the above process until the d values ​​of all cement mortar grids are calculated, and the d value distribution of the calculation area can be obtained; S17, the maximum value d max Indicates the maximum inscribed sphere radius, and the semi-major axis of the aggregate generated subsequently is no greater than d max .

3. The method for generating random three-dimensional irregular concrete aggregate according to claim 2, characterized in that: The step S15 comprises the following steps: S151, the coordinates of the grid to be determined are expressed as (i, j, k), where i represents the horizontal coordinate of the grid to be determined, j represents the vertical coordinate of the grid to be determined, and k represents the vertical coordinate of the grid to be determined; S152, half of the side length of the cubic grid area of ​​the aggregate to be generated is expressed as D, the initial value of D is 1, and the above cubic area is expressed as: (iD≤I≤i+D; jD≤J≤j+D; kD≤K≤k+D); Among them, I, J, and K are the coordinates of the cube in the x, y, and z directions respectively; S153, the distance between the grid to be determined and the three-dimensional grid in the cube area is expressed as dist. If all grids satisfying dist≤d+0.5 are filled with cement mortar, the d value of the grid to be determined is increased by 0.5, and the D value of the cube area is increased by 1.

4. The method for generating random three-dimensional irregular concrete aggregate according to claim 3, characterized in that: The step S2 comprises the following steps: S21. Randomly select the major and minor semi-axes a and b of the ellipse, find the cubic regions where the dmax value is greater than or equal to a, select the center point (h, k) of the ellipse in these regions, and randomly select the inclination angle of the ellipse S22, the ellipse polar coordinate parameter equation is: Among them, (rx, ry, rz) are the coordinates of the center of the ellipsoid, a, b and c are the semi-axis lengths of the ellipsoid on the x-axis, y-axis and z-axis respectively, and θ is the polar angle. is the azimuth; S23. The matrix Rx of the ellipsoid rotating around the x-axis is: S24, matrix Ry rotated around the y axis: S25, matrix Rz rotated around the z axis: S26. The rotation matrix of the ellipsoid as a whole is: R=R x R y R z S27. The coordinates (x, y, z) of any point in the ellipsoid are rotated by the rotation matrix R to obtain new coordinates (x', y', z'). The specific expression is as follows:

5. The method for generating random three-dimensional irregular concrete aggregate according to claim 4, characterized in that: The step S3 comprises the following steps: S31, generating 2N points on the surface of the ellipsoid, and randomly selecting N of the points to generate an irregular polyhedron; S32. For the i-th point (i∈[1,N)) generated on the ellipsoid surface, its polar angle and azimuth are expressed as: S33. The expression for mapping a point to the surface of an ellipsoid is: S34, obtaining three-dimensional irregular aggregate.

6. The method for generating random three-dimensional irregular concrete aggregate according to claim 5, characterized in that: The step S4 comprises the following steps: S41. For the obtained irregular polyhedron, three aspects of optimization need to be performed: flattening, removing triangular faces with very short sides, and removing triangular faces with extremely small internal angles; S42. In order to avoid obtaining flat aggregates, sphericity is used to describe the flattening degree of the aggregates. When the sphericity of the generated aggregate exceeds the set minimum sphericity, the corresponding aggregate can be generated. The sphericity B is expressed as: Among them, L l , L i , L s are the longest, middle and shortest dimensions respectively; S43, optimize the edge length, calculate the length of each edge of the irregular aggregate, when the shortest edge in a triangular plane of the aggregate is less than the preset minimum length L min , then remove one vertex of the edge and continue to optimize the new aggregate determined by the remaining vertices until all edge lengths are greater than L min ; S44, performing internal angle optimization, calculating the internal angle of each triangular face of the aggregate, when the minimum internal angle of one of the triangular faces is less than the preset value β, comparing the sizes of the other two internal angles, removing the vertex corresponding to the larger internal angle, and continuing to optimize the new aggregate formed by the remaining vertices until all internal angles are greater than β; S45. After geometric optimization of all aggregates, several aggregates with ideal shapes are obtained.

7. The method for generating random three-dimensional irregular concrete aggregate according to claim 6, characterized in that: The step S5 comprises the following steps: S51. Calculate the center of gravity of the polyhedron. The center of gravity is the average value of all vertex coordinates: Among them, (centroid x , centroid y , centroid z ) is the barycentric coordinate, N is the number of vertices, X i ,Y i ,Z i are the coordinates of the i-th vertex. S52. Calculate the distance d from each vertex to the center of gravity i : S53. Assuming that the thickness of the bonding interface is l, the distance from the new vertex to the center of gravity after shrinkage is: d’ i =d i -l S54, the new vertex (X' i , Y' i , Z' i ) coordinates are:

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