Asphalt mixture coarse aggregate gradation design method based on micromechanical properties, computer equipment and storage medium

Abstract

The present invention discloses a method, computer equipment and storage medium for designing the gradation of coarse aggregate of asphalt mixture based on microscopic mechanical properties, and relates to the field of asphalt mixture. The design method comprises: constructing a stacking model; the stacking model comprises a second rigid wall arranged at the radial periphery; the second rigid wall is replaced by a flexible confining pressure wall, and a three-dimensional discrete element model is obtained by servo; the flexible confining pressure wall comprises a plurality of spherical particles that can transmit pressure in the radial direction; a preset radial load and a preset axial load are applied, and the normal contact force, tangential contact force, normal vector, tangential vector and branch vector of each contact are extracted; the principal axis anisotropy coefficient is constructed; the optimal gradation of each level of coarse aggregate is determined according to the relationship between the principal axis anisotropy coefficient of the second coarse aggregate assembly and its axial strain under the preset axial load and radial load. The present invention solves the problem of poor correlation between the volume design method and road performance, and the designed gradation has excellent mechanical properties.

Description

Technical Field

[0001] The invention relates to the field of asphalt mixtures, and in particular to a coarse aggregate gradation design method for asphalt mixtures based on microscopic mechanical properties, a computer device and a storage medium. Background Art

[0002] Asphalt mixture gradation is directly related to its road performance. If the gradation is too fine, flow deformation is likely to occur at high temperature, which will then evolve into rutting disease; if the gradation is too coarse, the void ratio is large, which is not only easy to segregate during construction, but also prone to water damage disease in later use. Therefore, the best design gradation should have excellent mechanical properties, and the gradation design should be carried out based on the mechanical properties.

[0003] However, the current gradation design is mainly carried out based on volume indicators or experience, which can be divided into the following categories:

[0004] 1. Design using the CAVF method. The basic idea of ​​the CAVF method is to use asphalt mortar as a filler to fill the voids of the main aggregate, so that the sum of the volume of fine aggregate, the volume of asphalt, the volume of mineral powder and the void volume of the designed mixture is equal to the measured void volume of the main skeleton. The idea is that the main aggregate plays an interlocking role, the fine aggregate plays a filling role, and the proportion of each grade of coarse aggregate is determined by the packing density with different dosages. The default is that the packing density is the largest and the interlocking effect is the best. Its disadvantages are: (1) The repeatability error of the packing density test is large; (2) A large packing density does not mean the best interlocking effect; (3) This method is actually designed using the volume method. Whether the designed gradation mechanical properties are optimal is worth discussing.

[0005] 2. Design using the Bailey method. The Bailey method is based on the interference theory and adopts the plane circle model assumption. It is believed that the maximum particle size of the next-level aggregate cannot interfere with the particle aggregate of the previous level. It controls the passing percentage ratio of the key sieve hole size of the coarse aggregate and the fine aggregate to obtain a good skeleton structure for the gradation of the mineral material. Its disadvantages are: (1) The plane circle assumption is far from the three-dimensional aggregate particles, and the design results have a large deviation; (2) It is only applicable to continuous grading; (3) The volume filling effect of the mineral powder is not considered.

[0006] 3. Design using the Marshall method. The core of the Marshall method design is the volume index, which is to find a gradation curve that meets the volume parameter requirements within a given gradation range. Its disadvantages are: (1) The gradation curve is not unique. There are several gradation curves that meet the volume parameter requirements within the gradation range. Therefore, the selection of the gradation curve is highly subjective; (2) The road performance of the asphalt mixture obtained by the gradation curve that meets the volume index is not necessarily the best. The correlation between the volume index and the road performance needs to be discussed. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a design method, computer equipment and storage medium for asphalt mixture gradation, which have a strong correlation with road performance and the designed gradation has excellent mechanical properties.

[0008] In order to solve the technical problem of the present invention, the present invention provides a method for designing the gradation of coarse aggregate of asphalt mixture based on microscopic mechanical properties, which comprises:

[0009] Constructing a stacking model of coarse aggregates with different gradation ratios; the stacking model includes a first coarse aggregate assembly, a first rigid wall disposed at the axial end of the first coarse aggregate assembly, and a second rigid wall disposed at the radial periphery of the first coarse aggregate assembly;

[0010] The second rigid wall is replaced by a flexible confining pressure wall, and the stacking model is servoed to a preset target void ratio according to a preset contact stiffness, and the first rigid wall is removed to obtain a three-dimensional discrete element model; the three-dimensional discrete element model includes a second coarse aggregate assembly and a flexible confining pressure wall, and the flexible confining pressure wall is composed of a plurality of spherical particles, each of which can transmit pressure in a radial direction;

[0011] Applying a preset radial load and a preset axial load to the three-dimensional discrete element model to obtain a mechanical response model; the coarse aggregate particles in the mechanical response model form a plurality of contacts under the action of the radial load and the axial load, and extracting the normal vector of each contact;

[0012] Constructing a principal axis anisotropy coefficient representing the degree of anisotropy in each principal axis direction according to the normal vector;

[0013] The optimal gradation of each level of coarse aggregate is determined according to the relationship between the principal axial anisotropy coefficient of the second coarse aggregate assembly and its axial strain under the preset axial load and radial load, and the coarse aggregate mixture is prepared with the optimal grade.

[0014] As an improvement of the above technical solution, the step of constructing a principal axis anisotropy coefficient characterizing the degree of anisotropy in each principal axis direction according to the normal vector includes:

[0015] Extract the projection size of the normal vector of each contact of the second coarse aggregate in the local coordinate system in the three directions of x, y and z;

[0016] Construct variables to store the structured tensor and construct the structured tensor matrix;

[0017] Constructing a second-order structure tensor matrix according to the composition tensor matrix;

[0018] The principal axis anisotropy coefficients are constructed based on the second-order structure tensor matrix.

[0019] As an improvement of the above technical solution, the structure tensor matrix is ​​as follows:

[0020]

[0021] The calculation method of each parameter in the structure tensor matrix is ​​as follows:

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028] in, is the fabric tensor of the second coarse aggregate, , , , , , , , , All of them are variables that store structured tensors. tensor1, tensor2, tensor3, tensor4, tensor5, and tensor6 are all storage variables. is a variable representing the projection length of the normal vector in the x direction, is a variable representing the projection length of the normal vector in the y direction, is the variable representing the projection length of the normal vector in the z direction, is the total contact number of coarse aggregate particles in the mechanical response model;

[0029] The second-order structure tensor matrix is ​​as follows:

[0030]

[0031] in, is the second-order structure tensor of the second coarse aggregate , , , , , , , , They are all variables storing the configuration tensor, λ2 is the second constant;

[0032] Among them, the principal axis anisotropy coefficient is calculated according to the following formula group:

[0033]

[0034]

[0035]

[0036] Among them, P is the principal axis anisotropy coefficient, x 1. x 2. x 3 is a cubic equation The three real roots of A, B, and C are cubic equations of one variable The coefficient of is a cubic equation The minimum value of the real root of is a cubic equation The maximum value of the real root of ;

[0037] Among them, A, B, and C are calculated according to the following formula group:

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053] Among them, A, B, and C are cubic equations of one variable. The coefficient of , , , , , , , , , , , are the first intermediate coefficients, and λ2 is the second constant.

[0054] As an improvement of the above technical solution, a preset radial load and a preset axial load are applied to the three-dimensional discrete element model to obtain a mechanical response model; the coarse aggregate particles in the mechanical response model form multiple contacts under the action of the radial load and the axial load, and the step of extracting the normal vector of each contact also includes extracting the contact motion coefficient between each contact; the contact motion coefficient includes a single sliding coefficient, a single rolling coefficient, a sliding-rolling composite coefficient and a non-motion coefficient;

[0055] The step of constructing the principal axis anisotropy coefficient characterizing the degree of anisotropy in each principal axis direction according to the normal vector also includes the step of constructing a redundancy ratio according to the contact motion coefficient;

[0056] The step of determining the optimal gradation of each grade of coarse aggregate according to the relationship between the principal axial anisotropy coefficient of the second coarse aggregate assembly and its axial strain under preset axial load and radial load, and mixing the coarse aggregate mixture with the optimal grade includes determining the optimal gradation of each grade of coarse aggregate according to the relationship between the principal axial anisotropy coefficient and redundancy ratio of the second coarse aggregate assembly and its axial strain under preset axial load and radial load, and mixing the coarse aggregate mixture with the optimal grade.

[0057] As an improvement of the above technical solution, the redundancy ratio is calculated according to the following formula group:

[0058]

[0059]

[0060]

[0061]

[0062]

[0063] in, is the redundancy ratio of the second coarse aggregate, is the single sliding coefficient of the second coarse aggregate, is the single rolling coefficient of the second coarse aggregate, is the sliding-rolling composite coefficient of the second coarse aggregate, is the non-movement coefficient of the second coarse aggregate, is the single rolling coefficient of the cth contact, is the single sliding coefficient of the cth contact, is the sliding-rolling composite coefficient of the cth contact, is the non-kinematic coefficient of the cth contact, is the total contact number of coarse aggregate particles in the mechanical response model.

[0064] As an improvement of the above technical solution, a preset radial load and a preset axial load are applied to the three-dimensional discrete element model to obtain a mechanical response model; the coarse aggregate particles in the mechanical response model form a plurality of contacts under the action of the radial load and the axial load, and the step of extracting the normal vector of each contact also includes the step of extracting the normal contact force, tangential contact force, tangential vector and branch vector of each contact;

[0065] The step of constructing a principal axis anisotropy coefficient characterizing the degree of anisotropy in each principal axis direction according to the normal vector also includes the step of constructing a structural anisotropy coefficient according to the normal contact force, the tangential contact force, the normal vector, the tangential vector and the branch vector;

[0066] The step of determining the optimal gradation of each grade of coarse aggregate according to the relationship between the principal axial anisotropy coefficient of the second coarse aggregate assembly and its axial strain under preset axial load and radial load, and mixing the coarse aggregate mixture with the optimal grade includes determining the optimal gradation of each grade of coarse aggregate according to the relationship between the principal axial anisotropy coefficient, the structural anisotropy coefficient of the second coarse aggregate assembly and its axial strain under preset axial load and radial load, and mixing the coarse aggregate mixture with the optimal grade.

[0067] As an improvement of the above technical solution, the step of constructing the structural anisotropy coefficient according to the normal contact force, the tangential contact force, the normal vector, the tangential vector and the branch vector comprises:

[0068] The projection magnitudes of the tangent vector, branch vector, normal contact force in the x, y, and z directions, as well as the magnitudes of the normal contact force and the tangent contact force of each contact of the second coarse aggregate in the local coordinate system are extracted respectively;

[0069] Constructing the stress deviator tensor matrix, the deviator tensor matrix of the normal contact force structure tensor, and the deviator tensor matrix of the tangential contact force structure tensor;

[0070] Constructing the second-order structure tensor matrix of normal contact force and the second-order structure tensor matrix of tangential contact force;

[0071] Construct anisotropy coefficient, normal fabric anisotropy coefficient and tangential fabric anisotropy coefficient;

[0072] Construct the structural heterogeneity coefficient;

[0073] Among them, the stress deviator tensor matrix is:

[0074]

[0075] The calculation method of each parameter in the stress deviator tensor matrix is ​​as follows:

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083]

[0084]

[0085]

[0086] in, is the stress deviator of the second coarse aggregate, , , , , , , , , are variables storing stress tensors; λ1 is the first constant, is the variable that represents the projection of the normal contact force of the cth contact in the x direction, is the variable that represents the projection of the normal contact force of the cth contact in the y direction, is the variable that characterizes the projection of the normal contact force of the cth contact in the z direction, is the variable representing the projection length of the c-th contact branch vector in the x direction, is the variable representing the projection length of the c-th contact branch vector in the y direction, is the variable representing the projection length of the c-th contact branch vector in the z direction, V is the volume of the second coarse aggregate, N c is the total contact number of coarse aggregate particles in the mechanical response model;

[0087] Among them, the partial tensor matrix of the normal contact force structure tensor is:

[0088]

[0089] The parameters in the deviator matrix of the normal contact force structure tensor are calculated by the following formula group:

[0090]

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097]

[0098] in, is the deviator of the normal contact force structure tensor of the second coarse aggregate assembly, F 11n 、F 12n 、F 13n 、F 22n 、F 23n 、F 33n All of them are variables storing the normal contact force structure tensor, λ3 is the third constant, fn11, fn12, fn13, fn22, fn23, fn33 are all intermediate variables storing the normal contact force structure tensor, is a variable representing the projection length of the normal vector in the x direction, is a variable representing the projection length of the normal vector in the y direction, is a variable representing the projection length of the normal vector in the z direction, tensor1, tensor2, tensor3, tensor4, tensor5, and tensor6 are all storage variables, and akl is a variable representing the contact number. is the normal contact force of the cth contact, N c is the total contact number of coarse aggregate particles in the mechanical response model, , , , , , , , , All are first intermediate coefficients;

[0099] Among them, the partial tensor matrix of the tangential contact force structure tensor is:

[0100]

[0101] The parameters in the deviator matrix of the tangential contact force structure tensor are calculated by the following formula group:

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] in, is the deviator of the tangential contact force structure tensor of the second coarse aggregate assembly, F 11t 、F 12t 、F 13t 、F 22t 、F 23t 、F 33t are all variables storing the tangential contact force structure tensor, λ4 is the fourth constant, ft11, ft12, ft13, ft22, ft23, ft33 are all intermediate variables storing the tangential contact force structure tensor, is a variable representing the projection length of the normal vector in the x direction, is a variable representing the projection length of the normal vector in the y direction, is the variable representing the projection length of the normal vector in the z direction, is the variable representing the projection length of the tangent vector in the x direction, is the variable representing the projection length of the tangent vector in the y direction, is a variable representing the projection length of the tangent vector in the z direction, tensor1, tensor2, tensor3, tensor4, tensor5, and tensor6 are all storage variables, and akl is a variable representing the number of contacts. is the magnitude of the tangential contact force of the cth contact, N c is the total contact number of coarse aggregate particles in the mechanical response model, , , , , , , , , , are the first intermediate coefficients;

[0111] Among them, the second-order structural tensor matrix of normal contact force is:

[0112]

[0113] The parameters in the contact force second-order structure tensor matrix are calculated by the following formula group:

[0114]

[0115]

[0116]

[0117]

[0118]

[0119]

[0120] in, is the second-order structure tensor of the normal contact force of the second coarse aggregate, a 11n 、a 12n 、a 13n 、a 22n 、a 23n 、a 33n are variables storing the second-order structure tensor of the normal contact force, F 11n 、F 12n 、F 13n 、F 22n 、F 23n 、F 33n They are all variables storing the normal contact force structure tensor, and λ3 is the third constant;

[0121] Among them, the second-order structural tensor matrix of the tangential contact force is:

[0122]

[0123] The parameters in the second-order structure tensor matrix of the tangential contact force are calculated by the following formula group:

[0124]

[0125]

[0126]

[0127]

[0128]

[0129]

[0130] in, is the second-order structure tensor of the tangential contact force of the second coarse aggregate, a 11t 、a 12t 、a 13t 、a 22t 、a 23t 、a 33t are variables storing the second-order structure tensor of the tangential contact force, F 11t 、F 12t 、F 13t 、F 22t 、F 23t 、F 33t Both are variables that store the tangential contact force structure tensor, and λ4 is the fourth constant.

[0131] As an improvement of the above technical solution, the anisotropy coefficient is calculated according to the following formula:

[0132]

[0133] in, is the anisotropy coefficient of the second coarse aggregate, , , , , , , , , All are first intermediate coefficients;

[0134] The normal structural anisotropy coefficient is calculated according to the following formula group:

[0135]

[0136]

[0137]

[0138]

[0139]

[0140] in, is the normal structural anisotropy coefficient of the second coarse aggregate, , , , , , are variables storing stress tensors, a 11n 、a 12n 、a 13n 、a 22n 、a 23n 、a 33n are variables storing the second-order structure tensor of the normal contact force, V is the volume of the second coarse aggregate, λ1 is the first constant, , , are the second intermediate coefficients, sign() is the sign function, when >0,sign( )=1; when <0, sign( )=-1, is the standard value of the first double dot product;

[0141] The tangential structural anisotropy coefficient is calculated according to the following formula group:

[0142]

[0143]

[0144]

[0145]

[0146]

[0147] in, is the tangential structural anisotropy coefficient of the second coarse aggregate, , , , , , are variables storing stress tensors, a 11t 、a12t 、a 13t 、a 22t 、a 23t 、a 33t are variables storing the second-order structure tensor of the tangential contact force, V is the volume of the second coarse aggregate, is a constant, , , are the third intermediate coefficients, sign() is the sign function, when >0,sign( )=1; when <0, sign( )=-1, is the standard value of the second double dot product;

[0148] The structural anisotropy coefficient is calculated according to the following formula:

[0149]

[0150] Where p is the structural anisotropy coefficient of the second coarse aggregate, is the anisotropy coefficient of the second coarse aggregate, is the normal structural anisotropy coefficient of the second coarse aggregate, is the tangential structural anisotropy coefficient of the second coarse aggregate.

[0151] Correspondingly, the present invention also discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above-mentioned design method when executing the computer program.

[0152] Correspondingly, the present invention also discloses a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the design method steps of the above method are implemented.

[0153] The implementation of the present invention has the following beneficial effects:

[0154] In the asphalt mixture coarse aggregate gradation design method based on micro-mechanical properties of the present invention, a three-dimensional discrete element model, a three-dimensional flexible confining pressure, a servo control, a principal axis anisotropy coefficient, a redundancy ratio, and a structural anisotropy coefficient are combined to form a coarse aggregate gradation design process that is consistent with road performance and what you see is what you get, which effectively solves the shortcoming of the poor correlation between the volume design method and road performance, and the designed gradation has excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0155] Figure 1 is a three-dimensional schematic diagram of a 4.75-9.5 mm coarse aggregate scanned in Example 1 of the present invention;

[0156] Figure 2 is a three-dimensional schematic diagram of a 9.5-13.2 mm coarse aggregate scanned in Example 1 of the present invention;

[0157] Figure 3 is a schematic diagram of a confined space in Example 1 of the present invention;

[0158] Figure 4 is a schematic diagram of a flexible confining pressure wall in Example 1 of the present invention;

[0159] Figure 5 It is a schematic diagram of the numbering rules of the head balls, regular balls and tail balls of the even-numbered layers when the spherical particles are arranged in an interlaced manner in Example 1 of the present invention;

[0160] Figure 6 It is a schematic diagram of the numbering rules of the head balls, regular balls and tail balls of the odd-numbered layers when the spherical particles are arranged in an interlaced manner in Example 1 of the present invention;

[0161] Figure 7 Schematic diagram of the numbering rules of the head ball, the regular ball and the tail ball when the spherical particles are symmetrically arranged in Example 1 of the present invention;

[0162] Figure 8 Schematic diagram of the calculation rule of unit area when spherical particles are arranged in an interlocking manner in Example 1 of the present invention;

[0163] Fig. 9 is a schematic diagram of the calculation rule of the unit area when the spherical particles are symmetrically arranged in Example 1 of the present invention;

[0164] Fig.10 is a relationship diagram between the principal axis anisotropy coefficient and the axial strain under a confining pressure of 0.2 MPa in Example 1 of the present invention;

[0165] Fig.11 is a relationship diagram between the principal axis anisotropy coefficient and the axial strain under a confining pressure of 0.4 MPa in Example 1 of the present invention;

[0166] Fig.12 is a relationship diagram between the redundancy ratio and the axial strain under a confining pressure of 0.2 MPa in Example 1 of the present invention;

[0167] Fig.13 is a relationship diagram between the redundancy ratio and the axial strain under a confining pressure of 0.4 MPa in Example 1 of the present invention;

[0168] Fig.14 is a relationship diagram between the structural anisotropy coefficient and the axial strain under a confining pressure of 0.2 MPa in Example 1 of the present invention;

[0169] Fig.15 4 is a relationship diagram between the structural anisotropy coefficient and the axial strain under a confining pressure of 0.4 MPa in Example 1 of the present invention. DETAILED DESCRIPTION

[0170] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with specific implementation methods.

[0171] Example 1

[0172] This embodiment provides a method for designing the gradation of coarse aggregate of asphalt mixture based on micromechanical properties, including:

[0173] S1: Construct the stacking model of coarse aggregate with different grading ratios;

[0174] Specifically, in one embodiment, coarse aggregate refers to aggregate with a particle size ≥ 4.75 mm.

[0175] Specifically, step S1 includes:

[0176] S11: Scanning coarse aggregates of different particle sizes in each batch using a 3D scanner to form an STL format file, and forming a template with the 3D scanning files of different particle sizes;

[0177] Specifically, in one embodiment, taking asphalt mixture AC-13 as an example, its coarse aggregate includes two grades of 4.75~9.5mm and 9.5~13.2mm, and the stl files after three-dimensional scanning are as follows: Figure 1 , Figure 2 shown.

[0178] S12: Generate top, bottom and side rigid walls to form a confined space (see Figure 3 ), calculate the volume of the confined space;

[0179] S13: Use clump distribute to read coarse aggregate particles of different particle sizes in the template in sequence, determine the generation volume of each level of coarse aggregate particles according to the preset gradation ratio, and calculate the number of coarse aggregate particles required to generate each level of coarse aggregate according to the volume of a single coarse aggregate particle; the generation order is to generate coarse aggregate particle models in order from large to small particle sizes;

[0180] S14: randomly placing the generated coarse aggregate particle model into a predetermined area of ​​a preset closed space to obtain a stacking model;

[0181] Specifically, in one embodiment, steps S12 to S14 are completed in the three-dimensional discrete element software PFC.

[0182] S2: replacing the second rigid wall with a flexible confining pressure wall, servoing the stacking model to a preset target void ratio according to a preset contact stiffness, removing the first rigid wall, and obtaining a three-dimensional discrete element model;

[0183] Specifically, in one embodiment, step S2 includes:

[0184] S21: Replace the second rigid wall with a flexible confining pressure wall;

[0185] It should be noted that it is difficult to effectively apply radial loads (confining pressure) in traditional three-dimensional discrete element models, which makes it difficult to effectively simulate the stress effects on asphalt mixtures during actual road use. Based on this, the present invention replaces the second rigid wall with a flexible confining pressure wall (see Figure 4 ), in order to simulate the influence of radial load on the coarse aggregate. Specifically, the flexible confining wall is composed of multiple spherical particles, each of which can transmit pressure in the radial direction, thereby transmitting the radial load applied to the model to the coarse aggregate particles through the spherical particles. In order to accurately evaluate the above simulation, it is necessary to specify the specific number, diameter, and numbering rules of the spherical particles in the flexible confining wall in detail to achieve accurate extraction of the confining pressure on each spherical particle. The details are as follows:

[0186] In one embodiment, the flexible confining pressure wall includes multiple layers of spherical particles distributed along the axial direction;

[0187] The radius of the spherical particles in each spherical particle layer is calculated according to the following formula:

[0188]

[0189] Among them, r i is the radius of the spherical particles in the i-th spherical particle layer, R i is the radius of the first coarse aggregate in the accumulation model, N i is the number of spherical particles in the i-th spherical particle layer; specifically, for the convenience of calculation, the number of spherical particles in each spherical particle layer is set to 10 n , where n is a positive integer greater than or equal to 2. Further, the radii of all spherical particles in the flexible confining pressure wall are set to be the same.

[0190] The number of spherical particle layers in the flexible confining pressure wall is calculated according to the following formula:

[0191]

[0192] Among them, C i is the number of spherical granular layers in the flexible confining pressure wall, H i is the height of the flexible confining wall, r i is the radius of the spherical particles in the i-th spherical particle layer.

[0193] Specifically, in one embodiment, the spherical particles in each spherical particle layer in the flexible confining pressure wall are numbered from large to small. For example, in one embodiment, if the number of spherical particles in each spherical particle layer is 100, the starting number of the spherical particles in the layer can be set to 100000, the last spherical particle is numbered 100099, and so on.

[0194] Furthermore, in order to facilitate the calculation of the confining pressure of each spherical particle after the radial load is applied later, it is also necessary to stipulate the numbering rules between adjacent layers. Specifically, the spherical particles of adjacent spherical particle layers are arranged in an interlocking arrangement or a symmetrical arrangement; when the spherical particles are arranged in an interlocking arrangement, six spherical particles are arranged around each spherical particle; when the spherical particles are arranged in a symmetrical arrangement, four spherical particles are arranged around each spherical particle (see Figure 5~Figure 7 ). The following is a detailed description of the numbering rules between adjacent layers in each arrangement mode:

[0195] 1. When spherical particles are arranged in an interlocking manner, the numbering rules of spherical particles in even-numbered layers and odd-numbered layers are different;

[0196] When spherical particles are arranged in an interlaced manner, they are divided into head balls, regular balls, and tail balls. The head ball is the ball that starts numbering in each layer of balls. Its number N0 can be an integer, and N0 ≥ 10 n (n is a positive integer ≥ 3), such as 10000 or 100000; the tail ball is the ball at the end of each layer of balls, and its number is N e Can be an integer, and N e =N0+N i -1(N i is the total number of spherical particles in the i-th layer), exemplarily 10099 or 100099; the conventional balls are small balls between the head ball and the tail ball, numbered N0+1~N e -1, illustratively, 10001~10098 or 100001~100098 (taking 100 spherical particles in each layer as an example, but not limited to this); the numbering rules for even-numbered layers and odd-numbered layers are different. The details are as follows:

[0197] (I) See Figure 5 , the numbering rule for spherical particles in even layers is:

[0198] (1) See Figure 5 In (a), when it is an even-numbered header (the first ball), the ball is numbered bid, then

[0199] The number of the ball to the right of the ball is bid+1.

[0200] The number of the ball to the left of the ball is bid-1+N i ,

[0201] The number of the ball on the upper right side of the ball is bid+1+N i ,

[0202] The number of the ball on the upper left side of the ball is bid+N i ,

[0203] The number of the ball to the lower right of the ball is bid+1-N i ,

[0204] The number of the ball on the lower left side of the ball is bid-N i .

[0205] (2) See Figure 5 In (c), when it is the last ball of an even layer, the ball number is bid, then

[0206] The number of the ball to the right of the ball is bid+1-N i ,

[0207] The ball to the left of the ball is numbered bid-1.

[0208] The number of the ball on the upper right side of the ball is bid+1.

[0209] The number of the ball on the upper left side of the ball is bid+N i ,

[0210] The number of the ball to the lower right of the ball is bid+1-N i -N i ,

[0211] The number of the ball on the lower left side of the ball is bid-N i .

[0212] (3) See Figure 5 (b) in the figure is an even-numbered layer of regular balls (the 2nd to the Nth i -1 ball (the ordinary ball), record the ball number as bid, then

[0213] The number of the ball to the right of the ball is bid+1.

[0214] The ball to the left of the ball is numbered bid-1.

[0215] The number of the ball on the upper right side of the ball is bid+1+N i ,

[0216] The number of the ball on the upper left side of the ball is bid+N i ,

[0217] The number of the ball to the lower right of the ball is bid+1-Ni ,

[0218] The number of the ball on the lower left side of the ball is bid-N i .

[0219] It should be noted that Figure 5 N i = 100 for legend illustration, but N i The value of is not limited to this.

[0220] (ii) See Figure 6 , the numbering rule for odd-numbered layers of spherical particles is:

[0221] (1) See Figure 6 In (a), when it is the first ball in an odd layer, the ball is numbered as bid, then

[0222] The number of the ball to the right of the ball is bid+1.

[0223] The number of the ball to the left of the ball is bid-1+N i ,

[0224] The number of the ball on the upper right side of the ball is bid+N i ,

[0225] The number of the ball on the upper left side of the ball is bid-1+N i +N i ,

[0226] The number of the ball on the lower right side of the ball is bid-N i ,

[0227] The small ball on the lower left side of the ball is numbered bid-1.

[0228] (2) See Figure 6 In (c), when it is the last ball of an odd layer, the ball number is bid, then

[0229] The number of the ball to the right of the ball is bid+1-N i ,

[0230] The ball to the left of the ball is numbered bid-1.

[0231] The number of the ball on the upper right side of the ball is bid+N i ,

[0232] The number of the ball on the upper left side of the ball is bid-1+N i ,

[0233] The number of the ball on the lower right side of the ball is bid-N i ,

[0234] The ball on the lower left side of the ball is numbered bid-1-N i .

[0235] (3) See Figure 6 (b) in the figure is an odd-numbered layer of regular balls (the 2nd to Nth i -1 ball (the ordinary ball), record the ball number as bid, then

[0236] The number of the ball to the right of the ball is bid+1.

[0237] The ball to the left of the ball is numbered bid-1.

[0238] The number of the ball on the upper right side of the ball is bid+N i ,

[0239] The number of the ball on the upper left side of the ball is bid-1+N i ,

[0240] The number of the ball on the lower right side of the ball is bid-N i ,

[0241] The ball on the lower left side of the ball is numbered bid-1-N i .

[0242] It should be noted that Figure 6 N i = 100 for legend illustration, but N i The value of is not limited to this.

[0243] 2. When the spherical particles are arranged symmetrically, the numbering rule of the spherical particles is:

[0244] When the spherical particles are arranged symmetrically, they are divided into head balls, regular balls, and tail balls. The head ball is the ball that starts numbering in each layer of balls. Its number N0 can be an integer, and N0 ≥ 10 n (n is a positive integer ≥ 3), such as 10000 or 100000; the tail ball is the ball at the end of each layer of balls, and its number is N e Can be an integer, and N e =N0+N i -1(N i is the total number of spherical particles in the i-th layer), exemplarily 10099 or 100099; the conventional balls are small balls between the head ball and the tail ball, numbered N0+1~N e -1, illustratively, 10001-100098 or 100001~100098 (taking 100 spherical particles in each layer as an example, but not limited to this); the numbering rules of even-numbered layers and odd-numbered layers are the same, such as Figure 7As shown, more specific as follows:

[0245] (1) See Figure 7 In (a), when it is the first ball of each layer, the ball number is bid, then

[0246] The number of the ball to the right of the ball is bid+1.

[0247] The number of the ball to the left of the ball is bid-1+N i ,

[0248] The number of the ball directly above the ball is bid+N i ,

[0249] The number of the ball directly below the ball is bid-N i .

[0250] (2) See Figure 7 In (c), when it is the last ball of each layer, the ball number is bid, then

[0251] The number of the ball to the right of the ball is bid+1-N i ,

[0252] The ball to the left of the ball is numbered bid-1.

[0253] The number of the ball directly above the ball is bid+N i ,

[0254] The number of the ball directly below the ball is bid-N i .

[0255] (3) See Figure 7 (b) in the figure, when the regular balls in each layer (the 2nd to the Nth i -1 ball (the ordinary ball), let the ball be numbered bid, then

[0256] The number of the ball to the right of the ball is bid+1.

[0257] The ball to the left of the ball is numbered bid-1.

[0258] The number of the ball directly above the ball is bid+N i ,

[0259] The number of the ball directly below the ball is bid-N i .

[0260] It should be noted that Figure 7 N i = 100 for legend illustration, but N iThe value of is not limited to this.

[0261] S22: using a linear model to assign contact stiffness to each coarse aggregate particle in the first coarse aggregate assembly, and servo stacking model to a preset target void ratio;

[0262] Specifically, a linear contact bonding model may be used for simulation, and the stacking model may be servoed to a preset target void ratio under a given contact stiffness.

[0263] S3: applying a preset radial load and a preset axial load to the three-dimensional discrete element model to obtain a mechanical response model;

[0264] When a radial load is applied, the confining pressure exerted on the spherical particles in the spherical particle layer near the middle is calculated according to the area equivalence principle. Specifically, the center coordinates of each spherical particle are extracted according to the number of each spherical particle, the center vector of each spherical particle is calculated, and the preset area is calculated according to the center vector, and then the confining pressure exerted on each spherical particle is calculated;

[0265] Exemplarily, the nested arrangement is as follows Figure 8 As shown, the regular hexagon is the calculation unit area, and the regular hexagon is composed of six equilateral triangles. The force applied to the area of ​​the regular hexagon is equivalent to the force applied to the target ball BP_0, F=P*(S1+S2+S3+S4+S5+S6), where P is the confining pressure value, S1, S2, S3, S4, S5, and S6 are the areas of the six equilateral triangles respectively.

[0266] Taking the triangle S1 composed of balls BP_0, BP_UR, and BP_R as an example, the center coordinates of the three balls are extracted, the center vector is calculated, S1 is calculated based on the cross product of the center vectors, and then the force applied to S1 is calculated. When extracting the center coordinates of each ball, the extraction is performed according to the number of each ball. The numbering rules of the balls refer to Figure 5 and Figure 6 .

[0267] Symmetrical arrangement Fig. 9 As shown, the square is the calculation unit area, and the square is composed of four small squares. The force applied to the square area is equivalent to being applied to the target ball BP_0, F=P*(S1+S2+S3+S4), where P is the test confining pressure value, and S1, S2, S3, and S4 are the areas of the four squares respectively.

[0268] Take the square of (S1+S2+S3+S4) enclosed by the balls BP_R, BP_L, BP_U, and BP_D as an example, by extracting the center coordinates of the three balls BP_0, BP_L, and BP_U, calculate the center vector, calculate S1 based on half of the cross product of the center vector, and then calculate the force applied to S1. When extracting the center coordinates of each ball, extract them according to the number of each ball. The numbering rules of the balls refer to Figure 7 .

[0269] Specifically, after applying a preset radial load and a preset axial load to the three-dimensional discrete element model, the coarse aggregate particles form multiple contacts under the action of the radial load and the axial load, and the discrete element software PFC is used for simulation, and then the normal vector of each contact is extracted. It should be noted that the contact here is different from the coarse aggregate particles, and each coarse aggregate particle may form multiple contacts under the action of multiple coarse aggregate particles around it.

[0270] Preferably, in one embodiment, the normal contact force, tangential contact force, normal vector, tangential vector and branch vector of each contact are also extracted. More preferably, the contact motion coefficient is also extracted, which includes a single sliding coefficient, a single rolling coefficient, a sliding-rolling composite coefficient and a non-motion coefficient.

[0271] S4: construct the principal axis anisotropy coefficient representing the degree of anisotropy in each principal axis direction according to the normal vector;

[0272] Preferably, in one embodiment of the present invention, step S4 includes:

[0273] S411: extracting the projection size of the normal vector of each contact of the second coarse aggregate in the local coordinate system in the three directions of x, y and z;

[0274] Specifically, the contact.normal.x (cp), contact.normal.y (cp), and contact.normal.z (cp) functions are used to traverse and extract the projection size of the normal vector of each contact in the second coarse aggregate in the local coordinate system in the x, y, and z directions; the extraction algorithm is as follows:

[0275] cn1=contact.normal.x(cp)

[0276] cn2=contact.normal.y(cp)

[0277] cn3=contact.normal.z(cp).

[0278] S412: construct a variable for storing a composition tensor, and construct a composition tensor matrix;

[0279] Specifically, the tensor matrix is ​​constructed as follows:

[0280]

[0281] The calculation method of each parameter in the structure tensor matrix is ​​as follows:

[0282]

[0283]

[0284]

[0285]

[0286]

[0287]

[0288] in, is the fabric tensor of the second coarse aggregate, , , , , , , , , All of them are variables that store structured tensors. tensor1, tensor2, tensor3, tensor4, tensor5, and tensor6 are all storage variables. is a variable representing the projection length of the normal vector in the x direction, is a variable representing the projection length of the normal vector in the y direction, is the variable representing the projection length of the normal vector in the z direction, is the total contact number of coarse aggregate particles in the mechanical response model;

[0289] S413: constructing a second-order structure tensor matrix according to the structure tensor matrix;

[0290] Specifically, the second-order structure tensor matrix is ​​as follows:

[0291]

[0292] in, is the second-order structure tensor of the second coarse aggregate, , , , , , , , , Both are variables for storing configuration tensors, and λ2 is the second constant.

[0293] S414: construct principal axis anisotropy coefficients based on the second-order structure tensor matrix;

[0294] Specifically, the principal axis anisotropy coefficient is calculated according to the following formula group:

[0295]

[0296]

[0297]

[0298] Among them, P is the principal axis anisotropy coefficient, x 1. x 2. x 3 is a cubic equation The three real roots of A, B, and C are cubic equations of one variable The coefficient of is a cubic equation The minimum value of the real root of is a cubic equation The maximum value of the real root of ;

[0299] Among them, A, B, and C are calculated according to the following formula group:

[0300]

[0301]

[0302]

[0303]

[0304]

[0305]

[0306]

[0307]

[0308]

[0309]

[0310]

[0311]

[0312]

[0313]

[0314]

[0315] Among them, A, B, and C are cubic equations of one variable. The coefficient of , , , , , , , , , , , are the first intermediate coefficients, and λ2 is the second constant.

[0316] Preferably, in an embodiment of the present invention, step S4 also includes the step of constructing a redundancy ratio.

[0317] Specifically, the redundancy ratio is calculated according to the following formula group:

[0318]

[0319]

[0320]

[0321]

[0322]

[0323] in, is the redundancy ratio of the second coarse aggregate, is the single sliding coefficient of the second coarse aggregate, is the single rolling coefficient of the second coarse aggregate, is the sliding-rolling composite coefficient of the second coarse aggregate, is the non-movement coefficient of the second coarse aggregate, is the single rolling coefficient of the cth contact, is the single sliding coefficient of the cth contact, is the sliding-rolling composite coefficient of the cth contact, is the non-kinematic coefficient of the cth contact, is the total contact number of coarse aggregate particles in the mechanical response model.

[0324] Preferably, in an embodiment of the present invention, step S4 further includes the step of constructing a structural anisotropy coefficient according to the normal contact force, the tangential contact force, the normal vector and the tangential vector; specifically including:

[0325] S421: extracting the projection size of the tangential vector of each contact of the second coarse aggregate in the local coordinate system in the three directions of x, y and z, as well as the normal contact force and the tangential contact force;

[0326] Specifically, the contact.shear.x(cp), contact.shear.y(cp), and contact.shear.z(cp) functions are used to traverse and extract the projection lengths of the tangent vectors of each contact of the second coarse aggregate assembly in the local coordinate system in the x, y, and z directions.

[0327] cs1=contact.shear.x(cp)

[0328] cs2=contact.shear.y(cp)

[0329] cs3=contact.shear.z(cp)

[0330] Specifically, the contact.force.local.x(cp), contact.force.local.y(cp), and contact.force.local.z(cp) functions are used to traverse and extract the projection size of the normal contact force of each contact of the second coarse aggregate in the local coordinate system in the x, y, and z directions; the extraction algorithm is as follows:

[0331] foc1= contact.force.local.x(cp)

[0332] foc2= contact.force.local.y(cp)

[0333] foc3= contact.force.local.z(cp)

[0334] Specifically, the contact.branch.x(cp), contact.branch.y(cp), and contact.branch.z(cp) functions are used to traverse and extract the projection lengths of each contact branch vector in the x, y, and z directions of the second coarse aggregate in the local coordinate system. The extraction algorithm is as follows:

[0335] bra1 = contact.branch.x(cp)

[0336] bra2 = contact.branch.x(cp)

[0337] bra3 = contact.branch.x(cp)

[0338] Specifically, the contact.force.normal (cp) function is used to extract the magnitude of the normal contact force of each contact of the second coarse aggregate aggregate in the local coordinate system; the contact.force.shear (cp) function is used to extract the magnitude of the tangential contact force of each contact of the second coarse aggregate aggregate in the local coordinate system.

[0339] S422: construct the stress deviator tensor matrix, the deviator tensor matrix of the normal contact force structure tensor, and the deviator tensor matrix of the tangential contact force structure tensor;

[0340] Among them, the stress deviator tensor matrix is:

[0341]

[0342] The calculation method of each parameter in the above stress deviator tensor matrix is ​​as follows:

[0343]

[0344]

[0345]

[0346]

[0347]

[0348]

[0349]

[0350]

[0351]

[0352]

[0353] in, is the stress deviator of the second coarse aggregate, , , , , , , , , are variables storing stress tensors; λ1 is the first constant, is the variable that represents the projection of the normal contact force of the cth contact in the x direction, is the variable that represents the projection of the normal contact force of the cth contact in the y direction, is the variable that characterizes the projection of the normal contact force of the cth contact in the z direction, is the variable representing the projection length of the c-th contact branch vector in the x direction, is the variable representing the projection length of the c-th contact branch vector in the y direction, is the variable representing the projection length of the c-th contact branch vector in the z direction, V is the volume of the second coarse aggregate, N c is the total contact number of coarse aggregate particles in the mechanical response model;

[0354] Among them, the partial tensor matrix of the normal contact force structure tensor is:

[0355]

[0356] The parameters in the deviator matrix of the normal contact force structure tensor are calculated by the following formula group:

[0357]

[0358]

[0359]

[0360]

[0361]

[0362]

[0363]

[0364]

[0365] in, is the deviator of the normal contact force structure tensor of the second coarse aggregate assembly, F 11n 、F 12n 、F 13n 、F 22n 、F 23n 、F 33n All of them are variables storing the normal contact force structure tensor, λ3 is the third constant, fn11, fn12, fn13, fn22, fn23, fn33 are all intermediate variables storing the normal contact force structure tensor, is a variable representing the projection length of the normal vector in the x direction, is a variable representing the projection length of the normal vector in the y direction, is a variable representing the projection length of the normal vector in the z direction, tensor1, tensor2, tensor3, tensor4, tensor5, and tensor6 are all storage variables, and akl is a variable representing the contact number. is the normal contact force of the cth contact, N c is the total contact number of coarse aggregate particles in the mechanical response model, , , , , , , , , All are first intermediate coefficients;

[0366] Among them, the partial tensor matrix of the tangential contact force structure tensor is:

[0367]

[0368] The parameters in the deviator matrix of the tangential contact force structure tensor are calculated by the following formula group:

[0369]

[0370]

[0371]

[0372]

[0373]

[0374]

[0375]

[0376]

[0377] in, is the deviator of the tangential contact force structure tensor of the second coarse aggregate assembly, F 11t 、F 12t 、F 13t 、F 22t 、F 23t 、F 33tare all variables storing the tangential contact force structure tensor, λ4 is the fourth constant, ft11, ft12, ft13, ft22, ft23, ft33 are all intermediate variables storing the tangential contact force structure tensor, is a variable representing the projection length of the normal vector in the x direction, is a variable representing the projection length of the normal vector in the y direction, is the variable representing the projection length of the normal vector in the z direction, is the variable representing the projection length of the tangent vector in the x direction, is the variable representing the projection length of the tangent vector in the y direction, is a variable representing the projection length of the tangent vector in the z direction, tensor1, tensor2, tensor3, tensor4, tensor5, and tensor6 are all storage variables, and akl is a variable representing the number of contacts. is the magnitude of the tangential contact force of the cth contact, N c is the total contact number of coarse aggregate particles in the mechanical response model, , , , , , , , , Both are first intermediate coefficients.

[0378] S423: Construct the second-order structure tensor matrix of normal contact force and the second-order structure tensor matrix of tangential contact force;

[0379] Among them, the second-order structural tensor matrix of normal contact force is:

[0380]

[0381] Each parameter in the second-order structure matrix of the normal contact force is calculated by the following formula group:

[0382]

[0383]

[0384]

[0385]

[0386]

[0387]

[0388] in, is the second-order structure tensor of the normal contact force of the second coarse aggregate, a 11n 、a 12n 、a 13n 、a 22n 、a 23n 、a 33n are variables storing the second-order structure tensor of the normal contact force, F 11n 、F 12n 、F 13n 、F 22n 、F 23n 、F 33n They are all variables storing the normal contact force structure tensor, and λ3 is the third constant;

[0389] Among them, the second-order structural tensor matrix of the tangential contact force is:

[0390]

[0391] The parameters in the second-order structure tensor matrix of the tangential contact force are calculated by the following formula group:

[0392]

[0393]

[0394]

[0395]

[0396]

[0397]

[0398] in, is the second-order structure tensor of the tangential contact force of the second coarse aggregate, a 11t 、a 12t 、a 13t 、a 22t 、a 23t 、a 33t are variables storing the second-order structure tensor of the tangential contact force, F 11t 、F 12t 、F 13t 、F 22t 、F 23t 、F 33t Both are variables that store the tangential contact force structure tensor, and λ4 is the fourth constant.

[0399] S424: construct anisotropy coefficient, normal anisotropy coefficient and tangential anisotropy coefficient;

[0400] The anisotropy coefficient is calculated according to the following formula:

[0401]

[0402] in, is the anisotropy coefficient of the second coarse aggregate, , , , , , , , , All are first intermediate coefficients;

[0403] The normal structural anisotropy coefficient is calculated according to the following formula group:

[0404]

[0405]

[0406]

[0407]

[0408]

[0409] in, is the normal structural anisotropy coefficient of the second coarse aggregate, , , , , , are variables storing stress tensors, a 11n 、a 12n 、a 13n 、a 22n 、a 23n 、a 33n are variables storing the second-order structure tensor of the normal contact force, V is the volume of the second coarse aggregate, λ1 is the first constant, , , are the second intermediate coefficients, sign() is the sign function, when >0,sign( )=1; when <0, sign( )=-1, is the standard value of the first double dot product;

[0410] The tangential structural anisotropy coefficient is calculated according to the following formula group:

[0411]

[0412]

[0413]

[0414]

[0415]

[0416] in, is the tangential structural anisotropy coefficient of the second coarse aggregate, , , , , , are variables storing stress tensors, a 11t 、a 12t 、a 13t 、a 22t 、a 23t 、a 33t are variables storing the second-order structure tensor of the tangential contact force, V is the volume of the second coarse aggregate, λ1 is the first constant, , , are the third intermediate coefficients, sign() is the sign function, when >0,sign( )=1; when <0, sign( )=-1, is the standard value of the second double dot product;

[0417] S425: construct the structural heterogeneity coefficient;

[0418] The structural anisotropy coefficient is calculated according to the following formula:

[0419]

[0420] Where p is the structural anisotropy coefficient of the second coarse aggregate, is the anisotropy coefficient of the second coarse aggregate, is the normal structural anisotropy coefficient of the second coarse aggregate, is the tangential structural anisotropy coefficient of the second coarse aggregate.

[0421] S5: Determine the optimal gradation of each level of coarse aggregate according to the relationship between the principal axis anisotropy coefficient of the second coarse aggregate assembly and its axial strain under the preset axial load and radial load.

[0422] Specifically, in one embodiment, the optimal gradation of each level of coarse aggregate can be determined according to the relationship between the principal axis anisotropy coefficient, the redundancy ratio and the structural anisotropy coefficient of the second coarse aggregate assembly and its axial strain under the preset axial load and radial load. More specifically, the optimal gradation can be determined by the relationship between any one of the principal axis anisotropy coefficient, the redundancy ratio and the structural anisotropy coefficient and the axial strain, or by the relationship between the combination of any two of the three and the axial strain, and optimally, the optimal gradation can be determined by the relationship between the combination of the three and the axial strain.

[0423] For example, in one embodiment of the present invention, the relationship between the principal axis anisotropy coefficient, the redundancy ratio, and the structural anisotropy coefficient under the confining pressure of 0.2 MPa and 0.4 MPa is as follows: Figure 10~Figure 15 shown.

[0424] according to Figure 10~Figure 15 When 9.5~13.2mm:4.75~9.5mm=4:6, the mechanical properties of the coarse aggregate assembly are the best, so the ratio of coarse aggregate 9.5~13.2mm and 4.75~9.5mm is determined to be 4:6.

[0425] The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A method for designing coarse aggregate gradation of asphalt mixture based on micromechanical properties, characterized in that: include: Constructing a stacking model of coarse aggregates with different gradation ratios; the stacking model includes a first coarse aggregate assembly, a first rigid wall disposed at the axial end of the first coarse aggregate assembly, and a second rigid wall disposed at the radial periphery of the first coarse aggregate assembly; The second rigid wall is replaced by a flexible confining pressure wall, and the stacking model is servoed to a preset target void ratio according to a preset contact stiffness, and the first rigid wall is removed to obtain a three-dimensional discrete element model; the three-dimensional discrete element model includes a second coarse aggregate assembly and a flexible confining pressure wall, and the flexible confining pressure wall is composed of a plurality of spherical particles, each of which can transmit pressure in a radial direction; Applying a preset radial load and a preset axial load to the three-dimensional discrete element model to obtain a mechanical response model; the coarse aggregate particles in the mechanical response model form a plurality of contacts under the action of the radial load and the axial load, and extracting the normal vector of each contact; Constructing a principal axis anisotropy coefficient representing the degree of anisotropy in each principal axis direction according to the normal vector; The optimal gradation of each level of coarse aggregate is determined according to the relationship between the principal axial anisotropy coefficient of the second coarse aggregate assembly and its axial strain under the preset axial load and radial load, and the coarse aggregate mixture is prepared with the optimal grade.

2. The asphalt mixture coarse aggregate gradation design method based on micromechanical properties according to claim 1, characterized in that: The step of constructing a principal axis anisotropy coefficient characterizing the degree of anisotropy in each principal axis direction according to the normal vector comprises: Extract the projection size of the normal vector of each contact of the second coarse aggregate in the local coordinate system in the three directions of x, y and z; Construct variables to store the structured tensor and construct the structured tensor matrix; Constructing a second-order structure tensor matrix according to the composition tensor matrix; The principal axis anisotropy coefficients are constructed based on the second-order structure tensor matrix.

3. The asphalt mixture coarse aggregate gradation design method based on micromechanical properties according to claim 2, characterized in that: The structure tensor matrix is ​​as follows: The calculation method of each parameter in the structure tensor matrix is ​​as follows: in, is the fabric tensor of the second coarse aggregate, All of them are variables that store structured tensors. tensor1, tensor2, tensor3, tensor4, tensor5, and tensor6 are all storage variables. is a variable representing the projection length of the normal vector in the x direction, is a variable representing the projection length of the normal vector in the y direction, is the variable representing the projection length of the normal vector in the z direction, N c is the total contact number of coarse aggregate particles in the mechanical response model; The second-order structure tensor matrix is ​​as follows: in, is the second-order structure tensor of the second coarse aggregate, They are all variables storing the configuration tensor, λ2 is the second constant; Among them, the principal axis anisotropy coefficient is calculated according to the following formula group: Ax 3 +Bx 2 +Cx=0 Among them, P is the principal axis anisotropy coefficient, x1, x2, x3 are the cubic equation Ax 3 +Bx 2 +Cx=3 real roots of 0, A, B, C are the cubic equation Ax 3 +Bx 2 +Cx=0 coefficient, Ax is a cubic equation of one variable. 3 +Bx 2 + The minimum value of the real root of Cx = 0, Ax is a cubic equation of one variable. 3 +Bx 2 +The maximum value of the real root of Cx=0; Among them, A, B, and C are calculated according to the following formula group: A=I1 2 -3I2 B=I1·I2-9I3 C=I2 2 -3I1·I2 Among them, A, B, and C are cubic equations Ax 3 +Bx 2 +Cx=0 coefficient, I1, I2, and I3 are all first intermediate coefficients, and λ2 is the second constant.

4. The asphalt mixture coarse aggregate gradation design method based on mesomechanical properties according to claim 1, characterized in that: The mechanical response model is obtained by applying a preset radial load and a preset axial load to the three-dimensional discrete element model; the coarse aggregate particles in the mechanical response model form a plurality of contacts under the action of the radial load and the axial load, and the step of extracting the normal vector of each contact also includes extracting the contact motion coefficient between each contact; the contact motion coefficient includes a single sliding coefficient, a single rolling coefficient, a sliding-rolling composite coefficient and a non-motion coefficient; The step of constructing the principal axis anisotropy coefficient characterizing the degree of anisotropy in each principal axis direction according to the normal vector also includes the step of constructing a redundancy ratio according to the contact motion coefficient; The step of determining the optimal gradation of each grade of coarse aggregate according to the relationship between the principal axial anisotropy coefficient of the second coarse aggregate assembly and its axial strain under preset axial load and radial load, and mixing the coarse aggregate mixture with the optimal grade includes determining the optimal gradation of each grade of coarse aggregate according to the relationship between the principal axial anisotropy coefficient and redundancy ratio of the second coarse aggregate assembly and its axial strain under preset axial load and radial load, and mixing the coarse aggregate mixture with the optimal grade.

5. The asphalt mixture coarse aggregate gradation design method based on micromechanical properties according to claim 4, characterized in that: The redundancy ratio is calculated according to the following formula group: <h2 style=";text-align:left;direction:ltr">R<h2 style=";text-align:left;direction:ltr"> f <h2 style=";text-align:left;direction:ltr"> <5N<h2 style=";text-align:left;direction:ltr"> s <h2 style=";text-align:left;direction:ltr"> +3N<h2 style=";text-align:left;direction:ltr"> r <h2 style=";text-align:left;direction:ltr"> +3N<h2 style=";text-align:left;direction:ltr"> rr <h2 style=";text-align:left;direction:ltr"> +N<h2 style=";text-align:left;direction:ltr"> rs Among them, R f is the redundancy ratio of the second coarse aggregate, N s is the single sliding coefficient of the second coarse aggregate, N r is the single rolling coefficient of the second coarse aggregate, N rr is the sliding-rolling composite coefficient of the second coarse aggregate, N rs is the non-movement coefficient of the second coarse aggregate, is the single rolling coefficient of the cth contact, is the single sliding coefficient of the cth contact, is the sliding-rolling composite coefficient of the cth contact, is the non-kinematic coefficient of the cth contact, N c is the total contact number of coarse aggregate particles in the mechanical response model.

6. The asphalt mixture coarse aggregate gradation design method based on micromechanical properties according to claim 3, characterized in that: The step of applying a preset radial load and a preset axial load to the three-dimensional discrete element model to obtain a mechanical response model; the coarse aggregate particles in the mechanical response model form a plurality of contacts under the action of the radial load and the axial load, and the step of extracting the normal vector of each contact also includes the step of extracting the normal contact force, tangential contact force, tangential vector and branch vector of each contact; The step of constructing a principal axis anisotropy coefficient characterizing the degree of anisotropy in each principal axis direction according to the normal vector also includes the step of constructing a structural anisotropy coefficient according to the normal contact force, the tangential contact force, the normal vector, the tangential vector and the branch vector; The step of determining the optimal gradation of each grade of coarse aggregate according to the relationship between the principal axial anisotropy coefficient of the second coarse aggregate assembly and its axial strain under preset axial load and radial load, and mixing the coarse aggregate mixture with the optimal grade includes determining the optimal gradation of each grade of coarse aggregate according to the relationship between the principal axial anisotropy coefficient, the structural anisotropy coefficient of the second coarse aggregate assembly and its axial strain under preset axial load and radial load, and mixing the coarse aggregate mixture with the optimal grade.

7. The asphalt mixture coarse aggregate gradation design method based on micromechanical properties according to claim 6, characterized in that: The step of constructing the structural anisotropy coefficient according to the normal contact force, the tangential contact force, the normal vector, the tangential vector and the branch vector comprises: The projection magnitudes of the tangent vector, branch vector, normal contact force in the x, y, and z directions, as well as the magnitudes of the normal contact force and the tangent contact force of each contact of the second coarse aggregate in the local coordinate system are extracted respectively; Constructing the stress deviator tensor matrix, the deviator tensor matrix of the normal contact force structure tensor, and the deviator tensor matrix of the tangential contact force structure tensor; Constructing the second-order structure tensor matrix of normal contact force and the second-order structure tensor matrix of tangential contact force; Construct anisotropy coefficient, normal fabric anisotropy coefficient and tangential fabric anisotropy coefficient; Construct the structural heterogeneity coefficient; Among them, the stress deviator tensor matrix is: The calculation method of each parameter in the stress deviator tensor matrix is ​​as follows: Among them, σ i ' j is the stress deviator of the second coarse aggregate, σ 11 , σ 12 , σ 13 , σ 21 , σ 22 , σ 23 , σ 31 , σ 32 , σ 33 are variables storing stress tensors; λ1 is the first constant, foc 1c foc is a variable that represents the projection of the normal contact force of the cth contact in the x direction. 2c foc is the variable that represents the projection of the normal contact force of the cth contact in the y direction. 3c is a variable that represents the projection of the normal contact force of the cth contact in the z direction, bra 1c is a variable representing the projection length of the c-th contact branch vector in the x direction, bra 2c is a variable representing the projection length of the c-th contact branch vector in the y direction, bra 3c is the variable representing the projection length of the c-th contact branch vector in the z direction, V is the volume of the second coarse aggregate, N c is the total contact number of coarse aggregate particles in the mechanical response model; Among them, the partial tensor matrix of the normal contact force structure tensor is: The parameters in the deviator matrix of the normal contact force structure tensor are calculated by the following formula group: F 11n =fn11 / akl F 12n =fn12 / akl F 13n =fn13 / akl F 22n =fn22 / akl <h2 style=";text-align:left;direction:ltr">F<h2 style=";text-align:left;direction:ltr"> 23n <h2 style=";text-align:left;direction:ltr"> =fn23 / akl <h2 style=";text-align:left;direction:ltr">F<h2 style=";text-align:left;direction:ltr"> 33n <h2 style=";text-align:left;direction:ltr"> =fn33 / akl in, is the deviator of the normal contact force structure tensor of the second coarse aggregate assembly, F 11n 、F 12n 、F 13n 、F 22n 、F 23n 、F 33n All of them are variables storing the normal contact force structure tensor, λ3 is the third constant, fn11, fn12, fn13, fn22, fn23, fn33 are all intermediate variables storing the normal contact force structure tensor, is a variable representing the projection length of the normal vector in the x direction, is a variable representing the projection length of the normal vector in the y direction, is a variable representing the projection length of the normal vector in the z direction, tensor1, tensor2, tensor3, tensor4, tensor5, and tensor6 are all storage variables, and akl is a variable representing the contact number. is the normal contact force of the cth contact, N c is the total contact number of coarse aggregate particles in the mechanical response model, All are first intermediate coefficients; Among them, the partial tensor matrix of the tangential contact force structure tensor is: The parameters in the deviator matrix of the tangential contact force structure tensor are calculated by the following formula group: F 11t =ft11 / akl F 12t =ft12 / akl F 13t =ft13 / akl F 22t =ft22 / akl <h2 style=";text-align:left;direction:ltr">F<h2 style=";text-align:left;direction:ltr"> 23t <h2 style=";text-align:left;direction:ltr"> <ft23 / akl <h2 style=";text-align:left;direction:ltr">F<h2 style=";text-align:left;direction:ltr"> 33t <h2 style=";text-align:left;direction:ltr"> <ft33 / akl in, is the deviator of the tangential contact force structure tensor of the second coarse aggregate assembly, F 11t 、F 12t 、F 13t 、F 22t 、F 23t 、F 33t are all variables storing the tangential contact force structure tensor, λ4 is the fourth constant, ft11, ft12, ft13, ft22, ft23, ft33 are all intermediate variables storing the tangential contact force structure tensor, is a variable representing the projection length of the normal vector in the x direction, is a variable representing the projection length of the normal vector in the y direction, is the variable representing the projection length of the normal vector in the z direction, is the variable representing the projection length of the tangent vector in the x direction, is the variable representing the projection length of the tangent vector in the y direction, is a variable representing the projection length of the tangent vector in the z direction, tensor1, tensor2, tensor3, tensor4, tensor5, and tensor6 are all storage variables, akl is a variable representing the contact number, and f t c is the magnitude of the tangential contact force of the cth contact, N c is the total contact number of coarse aggregate particles in the mechanical response model, All are first intermediate coefficients; Among them, the second-order structural tensor matrix of normal contact force is: The parameters in the second-order structure tensor matrix of the normal contact force are calculated by the following formula group: in, is the second-order structure tensor of the normal contact force of the second coarse aggregate, a 11n 、a 12n 、a 13n 、a 22n 、a 23n 、a 33n are variables storing the second-order structure tensor of the normal contact force, F 11n 、F 12n 、F 13n 、F 22n 、F 23n 、F 33n They are all variables storing the normal contact force structure tensor, and λ3 is the third constant; Among them, the second-order structural tensor matrix of the tangential contact force is: The parameters in the second-order structure tensor matrix of the tangential contact force are calculated by the following formula group: in, is the second-order structure tensor of the tangential contact force of the second coarse aggregate, a 11t 、a 12t 、a 13t 、a 22t 、a 23t 、a 33t are variables storing the second-order structure tensor of the tangential contact force, F 11t 、F 12t 、F 13t 、F 22t 、F 23t 、F 33t Both are variables that store the tangential contact force structure tensor, and λ4 is the fourth constant.

8. The asphalt mixture coarse aggregate gradation design method based on micromechanical properties according to claim 7, characterized in that: The anisotropy coefficient is calculated according to the following formula: Among them, a c is the anisotropy coefficient of the second coarse aggregate, All are first intermediate coefficients; The normal structural anisotropy coefficient is calculated according to the following formula group: θ1=a 11n 2 +a 22n 2 +a 33n 2 +a 12n 2 +a 13n 2 +a 23n 2 ω1=(σ 11 -λ1) 2 +(s 22 -λ1) 2 +(s 33 -λ1) 2 +s 12 ·s 12 +s 23 ·s 23 +s 13 ·s 13 Among them, a n is the normal structural anisotropy coefficient of the second coarse aggregate, σ 11 , σ 12 , σ 13 , σ 22 , σ 23 , σ 33 are variables storing stress tensors, a 11n 、a 12n 、a 13n 、a 22n 、a 23n 、a 33n are variables storing the second-order structure tensor of the normal contact force, V is the volume of the second coarse aggregate, λ1 is the first constant, τ1, θ1, ω1 are the second intermediate coefficients, sign() is the sign function, when S r_an >0,sign(S r_an )=1; when S r_an <0,sign(S r_an )=-1,S r_an is the standard value of the first double dot product; The tangential structural anisotropy coefficient is calculated according to the following formula group: θ2=a 11t 2 +a 22t 2 +a 33t 2 +a 12t 2 +a 13t 2 +a 23t 2 ω2=(σ 11 -λ1) 2 +(s 22 -λ1) 2 +(s 33 -λ1) 2 +s 12 ·s 12 +s 23 ·s 23 +s 13 ·s 13 Among them, a t is the tangential structural anisotropy coefficient of the second coarse aggregate, σ 11 , σ 12 , σ 13 , σ 22 , σ 23 , σ 33 are variables storing stress tensors, a 11t 、a 12t 、a 13t 、a 22t 、a 23t 、a 33t are variables storing the second-order structure tensor of the tangential contact force, V is the volume of the second coarse aggregate, λ1 is the first constant, τ2, θ2, ω2 are the third intermediate coefficients, sign() is the sign function, when S r_at >0,sign(S r_at )=1; when S r_an <0,sign(S r_at )=-1,S r_at is the standard value of the second double dot product; The structural anisotropy coefficient is calculated according to the following formula: p=0.4(a c +a n +1.5a t ) Among them, p is the structural anisotropy coefficient of the second coarse aggregate, a c is the anisotropy coefficient of the second coarse aggregate, a n is the normal structural anisotropy coefficient of the second coarse aggregate, a t is the tangential structural anisotropy coefficient of the second coarse aggregate.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the design method according to any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the design method steps according to any one of claims 1 to 8 are implemented.

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