Coarse Aggregate Gradation Design Method, Computer Equipment and Storage Medium in Asphalt Mixture

Abstract

The present invention discloses a method for designing the coarse aggregate gradation in asphalt mixture, a computer device and a storage medium, which relate to the field of asphalt mixture. Among them, the design method includes: constructing a stacking model; the stacking model includes a second rigid wall disposed on the outer periphery of the diameter; replacing the second rigid wall with a flexible confining wall and servoing to obtain a three-dimensional discrete element model; the flexible confining wall includes a plurality of spherical particles capable of transmitting pressure in the radial direction; applying a preset radial load and a preset axial load, and extracting the normal contact force, tangential contact force, normal vector, tangential vector, branch vector, normal branch vector and tangential branch vector of each contact; constructing a fabric anisotropy coefficient; determining the optimal gradation of each grade of coarse aggregate according to the relationship between the weighted fabric stress coefficient of the second coarse aggregate aggregate and its axial strain under the preset axial load and radial load. The present invention solves the disadvantage of poor correlation between the volume design method and the road performance, and the designed gradation has excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to the field of asphalt mixtures, and particularly to a method for designing the coarse aggregate gradation in asphalt mixtures, a computer device, and a storage medium. Background Art

[0002] The gradation of asphalt mixtures is directly related to their road performance. If the gradation is too fine, it is prone to flow deformation at high temperatures, which will further evolve into rutting diseases; if the gradation is too coarse, the void ratio is large, and during the construction process, it is not only prone to segregation, but also prone to water damage diseases during later use. Therefore, the optimal designed gradation should have excellent mechanical properties, and the gradation design should be carried out according to the mechanical properties.

[0003] However, at present, the gradation design mainly carries out the design work according to volume indicators or experience, which is mainly divided into the following types:

[0004] I. Design by 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 volume of voids in the designed mixture is equal to the measured volume of voids in the main skeleton. Its concept is that the main aggregate plays an interlocking role, and the fine aggregate plays a filling role. However, the proportion of each grade of coarse aggregate is determined by the compacted density at different dosages, and it is defaulted that the compacted density is the largest and the interlocking is the best. Its disadvantages are: (1) The repeatability error of the compacted density test is large; (2) A large compacted density does not mean the best interlocking effect; (3) This method actually uses the volume method for design, and whether the designed gradation has the best mechanical properties is debatable.

[0005] II. Design by the Bailey method. The Bailey method is based on the interference theory and adopts the plane circle model hypothesis, believing that the maximum particle size of the next-level aggregate cannot interfere with the aggregate particle assembly of the previous level. Its main feature is to control the percentage ratio relationship of the passing rates of the key sieve hole sizes of coarse aggregate and fine aggregate, so that the mineral aggregate gradation obtains a good skeleton structure. Its disadvantages are: (1) The plane circle hypothesis is very different from the three-dimensional solid aggregate particles, and there are large deviations in the design results; (2) It is only applicable to continuous gradations; (3) The influence of the volume filling of mineral powder is not considered.

[0006] III. Design by the Marshall method. The core of the Marshall method design is the volume index, and a gradation curve that meets the volume parameter requirements is found within the given gradation range. Its disadvantages are: (1) The gradation curve is not unique, and there are several gradation curves that meet the volume parameter requirements within the gradation range. Therefore, the subjective awareness of selecting the gradation curve is strong; (2) The road performance of the asphalt mixture designed by the gradation curve that meets the volume index is not necessarily the most excellent, and the correlation between the volume index and the road performance is debatable. Summary of the Invention

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

[0008] To solve the technical problem of the present invention, the present invention provides a method for designing the coarse aggregate gradation in asphalt mixtures, which includes:

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

[0010] Replacing the second rigid wall with a flexible confining wall and servoing to a preset target void ratio according to a preset contact stiffness, and removing the first rigid wall to obtain a three-dimensional discrete element model; the three-dimensional discrete element model includes a second coarse aggregate aggregate and a flexible confining wall, and the flexible confining wall is composed of a plurality of spherical particles, and each spherical particle can transmit pressure in the 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 extract the normal contact force, tangential contact force, normal vector, tangential vector, branch vector, normal branch vector, and tangential branch vector of each contact;

[0012] Constructing a fabric anisotropy coefficient according to the normal contact force, tangential contact force, normal vector, tangential vector, branch vector, normal branch vector, and tangential branch vector;

[0013] Constructing a weighted fabric anisotropy coefficient of the second coarse aggregate aggregate according to the fabric anisotropy coefficient;

[0014] Determining the optimal gradation of each size of coarse aggregate according to the relationship between the weighted fabric anisotropy coefficient of the second coarse aggregate aggregate and its axial strain under the preset axial load and radial load, and synthesizing a coarse aggregate mixture with the optimal gradation.

[0015] As an improvement of the above technical solution, the step of constructing a stacking model of coarse aggregates with different gradation ratios includes:

[0016] Extracting the geometric parameters of the coarse aggregate particles;

[0017] Filling each size of coarse aggregate with a preset gradation ratio into the enclosed space formed by the first rigid wall and the second rigid wall to obtain a stacking model;

[0018] Replacing the second rigid wall with a flexible confining wall and servoing to a preset target void ratio according to a preset contact stiffness, and removing the first rigid wall to obtain a three-dimensional discrete element model includes the steps of:

[0019] Replacing the second rigid wall with a flexible confining wall;

[0020] Assigning contact stiffness to each coarse aggregate particle in the first coarse aggregate aggregate with a linear model and servoing to a preset target porosity;

[0021] Removing the first rigid wall to obtain a three-dimensional discrete element model.

[0022] As an improvement of the above technical solution, the flexible confining wall includes multiple layers of spherical particle layers distributed axially;

[0023] The radius of the spherical particles in each layer of spherical particle layer is calculated according to the following formula:

[0024]

[0025] where r i is the radius of the spherical particles in the i-th layer of spherical particle layer, R i is the radius of the first coarse aggregate aggregate in the packing model, and N i is the number of spherical particles in the i-th layer of spherical particle layer;

[0026] The number of layers of spherical particle layers in the flexible confining wall is calculated according to the following formula:

[0027]

[0028] where C i is the number of layers of spherical particle layers in the flexible confining wall, H i is the height of the flexible confining wall, and r i is the radius of the spherical particles in the i-th layer of spherical particle layer.

[0029] As an improvement of the above technical solution, in 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, when applying the radial load, the confining pressure received by the spherical particles in the spherical particle layer is calculated according to the area equivalence principle.

[0030] As an improvement of the above technical solution, the step of constructing the fabric anisotropy coefficient according to the normal contact force, tangential contact force, normal vector, branch vector, tangential vector, normal branch vector, and tangential branch vector includes the steps of calculating the stress tensor and fabric tensor according to the normal contact force, normal vector, tangential vector, and branch vector, and calculating the anisotropy coefficient according to the stress tensor and fabric tensor;

[0031] Among them, the stress tensor, fabric tensor, and anisotropy coefficient are calculated according to the following set of formulas:

[0032]

[0033]

[0034]

[0035]

[0036] is the stress tensor of the second coarse aggregate aggregate, is the fabric tensor of the second coarse aggregate aggregate, is the second-order structure tensor of the second coarse aggregate aggregate, is the anisotropy coefficient of the second coarse aggregate aggregate, is the normal contact force of the c-th contact, is the branch vector of the c-th contact, V is the volume of the second coarse aggregate aggregate, 、 are the projection lengths of the unit normal vector of the c-th contact in the k-direction and l-direction respectively, is the total number of contacts of the coarse aggregate particles in the mechanical response model.

[0037] As an improvement of the above technical solution, the step of constructing the fabric anisotropy coefficient according to the normal contact force, tangential contact force, normal vector, tangential vector, branch vector, normal branch vector and tangential branch vector further includes: calculating the structure tensor of the normal contact force, the structure tensor of the tangential contact force, the structure tensor of the normal branch vector, and the structure tensor of the tangential branch vector;

[0038] Among them, the calculation method of the structure tensor of the normal contact force is as follows:

[0039]

[0040] Among them, is the structure tensor of the normal contact force of the second coarse aggregate aggregate, is the magnitude of the normal contact force of the c-th contact, 、 are the projection magnitudes of the unit normal contact force of the c-th contact in the i-direction and j-direction respectively, is the second-order structure tensor of the second coarse aggregate aggregate, 、 are the projection lengths of the unit normal vector of the c-th contact in the k-direction and l-direction respectively, is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0041] The calculation method of the structural tensor of the tangential contact force is as follows:

[0042]

[0043] Among them, is the structural tensor of the tangential contact force of the second coarse aggregate aggregate, is the magnitude of the tangential contact force of the c-th contact, and are the projection magnitudes of the unit tangential contact force of the c-th contact in the i-direction and j-direction respectively, is the second-order structural tensor of the second coarse aggregate aggregate, and are the projection lengths of the unit normal vector of the c-th contact in the k-direction and l-direction respectively, is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0044] Among them, the calculation method of the structural tensor of the normal branch vector is as follows:

[0045]

[0046] Among them, is the structural tensor of the normal branch vector of the second coarse aggregate aggregate, is the length of the normal branch vector of the c-th contact, is the second-order structural tensor of the second coarse aggregate aggregate, and are the projection lengths of the unit normal branch vector of the c-th contact in the i-direction and j-direction respectively, and are the projection lengths of the unit normal vector of the c-th contact in the k-direction and l-direction respectively, is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0047] Among them, the calculation method of the structural tensor of the tangential branch vector is as follows:

[0048]

[0049] Among them, is the structural tensor of the tangential branch vector of the second coarse aggregate aggregate, is the length of the tangential branch vector of the c-th contact, and are the projection lengths of the unit tangential branch vector of the c-th contact in the i-direction and j-direction, is the second-order structural tensor of the second coarse aggregate aggregate, and They are the projection lengths of the unit normal vector of the c-th contact in the k direction and the l direction, respectively. is the total number of contacts of the coarse aggregate particles in the mechanical response model.

[0050] As an improvement to the above technical solution, the step of constructing the fabric anisotropy coefficient according to the normal contact force, tangential contact force, normal vector, tangential vector, branch vector, normal branch vector, and tangential branch vector further includes: calculating the normal contact force fabric anisotropy coefficient, tangential contact force fabric anisotropy coefficient, normal branch vector fabric anisotropy coefficient, and tangential branch vector fabric anisotropy coefficient that characterize the degree of anisotropy in different directions.

[0051] Among them, the calculation method of the normal contact force fabric anisotropy coefficient is as follows:

[0052]

[0053] In the formula, is the normal contact force anisotropy coefficient of the second coarse aggregate aggregate, and are both the second-order structure tensors of the normal contact force of the second coarse aggregate aggregate, and are both the deviatoric tensors of the stress tensor of the second coarse aggregate aggregate; is the structure tensor of the normal contact force of the second coarse aggregate aggregate of the deviatoric tensor, is the magnitude of the average normal contact force of the second coarse aggregate aggregate, is the magnitude of the normal contact force of the c-th contact, is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0054] Among them, the calculation method of the tangential contact force fabric anisotropy coefficient is as follows:

[0055]

[0056] In the formula, is the tangential contact force fabric anisotropy coefficient of the second coarse aggregate aggregate, is and the standard value of the double dot product; sign() is the sign function. When > 0, sign( ) = 1; when < 0, sign( ) = -1; and are both the second-order structure tensors of the tangential contact force of the second coarse aggregate aggregate; and They are all the deviatoric tensors of the stress tensors of the second coarse aggregate assemblies; is the structural tensor of the tangential contact forces of the second coarse aggregate assembly of the deviatoric tensor, is the magnitude of the average tangential contact force of the second coarse aggregate assembly, is the magnitude of the tangential contact force of the c-th contact, is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0057] Among them, the calculation method of the normal branch vector fabric anisotropy coefficient is as follows:

[0058]

[0059] In the formula, is the normal branch vector fabric anisotropy coefficient of the second coarse aggregate assembly, is and the standard value of the double dot product; sign() is the sign function. When > 0, sign( ) = 1; when < 0, sign( ) = -1; and are both the second-order structural tensors of the normal branch vectors of the second coarse aggregate assembly; and are both the deviatoric tensors of the stress tensors of the second coarse aggregate assembly, is the structural tensor of the normal branch vector of the deviatoric tensor, is the average normal branch vector length of the second coarse aggregate assembly, is the length of the normal branch vector of the c-th contact, is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0060] Among them, the calculation method of the tangential branch vector fabric anisotropy coefficient is as follows:

[0061]

[0062] In the formula, is the tangential branch vector fabric anisotropy coefficient of the second coarse aggregate assembly, is and the standard value of the double dot product; sign() is the sign function. When > 0, sign( ) = 1; when < 0, sign( ) = -1; and They are all the second-order structure tensors of the tangential branch vectors of the second coarse aggregate aggregate; and They are all the deviatoric tensors of the stress tensors of the second coarse aggregate aggregate, is the structure tensor of the tangential branch vector of the second coarse aggregate aggregate of the deviatoric tensor, is the average length of the tangential branch vectors of the second coarse aggregate aggregate, is the length of the tangential branch vector of the c-th contact, is the total number of contacts of the coarse aggregate particles in the mechanical response model.

[0063] As an improvement to the above technical solution, the weighted fabric anisotropy coefficient is calculated according to the following formula:

[0064] ;

[0065] In the formula, is the weighted fabric anisotropy coefficient of the second coarse aggregate aggregate, is the anisotropy coefficient of the second coarse aggregate aggregate, is the normal contact force fabric anisotropy coefficient of the second coarse aggregate aggregate, is the normal branch vector fabric anisotropy coefficient of the second coarse aggregate aggregate, is the tangential branch vector fabric anisotropy coefficient of the second coarse aggregate aggregate, is the tangential contact force fabric anisotropy coefficient of the second coarse aggregate aggregate.

[0066] Correspondingly, the present invention also discloses a computer device, including a memory and a processor, the memory stores a computer program, and when the processor executes the computer program, the steps of the above design method are realized.

[0067] Correspondingly, the present invention also discloses a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above gradation design method are realized.

[0068] Implementing the present invention has the following beneficial effects:

[0069] In the coarse aggregate gradation design method of the asphalt mixture of the present invention, the three-dimensional discrete element model, three-dimensional flexible confining pressure, servo control, fabric tensor, structure tensor, and fabric anisotropy coefficient are combined to form a coarse aggregate gradation design process that is consistent with the road performance and what you see is what you get. Specifically: The present invention adopts flexible confining pressure control, which can track the multiple mechanical properties of the coarse aggregate aggregate within the effective deformation range and comprehensively evaluate the effectiveness of the designed gradation. The present invention adopts the theoretical method, effectively solves the shortcoming of poor correlation between the volume design method and the road performance, and the designed gradation has excellent mechanical properties. Description of the Drawings

[0070] Figure 1 It is a three - dimensional schematic diagram after scanning the coarse aggregate of 4.75 - 9.5mm in Embodiment 1 of the present invention;

[0071] Figure 2 It is a three - dimensional schematic diagram after scanning the coarse aggregate of 9.5 - 13.2mm in Embodiment 1 of the present invention;

[0072] Figure 3 It is a schematic diagram of the closed space in Embodiment 1 of the present invention;

[0073] Figure 4 It is a schematic diagram of the flexible confining pressure wall in Embodiment 1 of the present invention;

[0074] Figure 5 It is a schematic diagram of the numbering rules for the head balls, regular balls, and tail balls in the even layers when the spherical particles are arranged in an interlocking pattern in Embodiment 1 of the present invention;

[0075] Figure 6 It is a schematic diagram of the numbering rules for the head balls, regular balls, and tail balls in the odd layers when the spherical particles are arranged in an interlocking pattern in Embodiment 1 of the present invention;

[0076] Figure 7 It is a schematic diagram of the numbering rules for the head balls, regular balls, and tail balls when the spherical particles are arranged symmetrically in Embodiment 1 of the present invention;

[0077] Figure 8 It is a schematic diagram of the calculation rules for the unit area when the spherical particles are arranged in an interlocking pattern in Embodiment 1 of the present invention;

[0078] Figure 9 It is a schematic diagram of the calculation rules for the unit area when the spherical particles are arranged symmetrically in Embodiment 1 of the present invention;

[0079] Figure 10 It is a graph showing the relationship between the weighted fabric stress coefficient and the axial strain under a confining pressure of 0.2MPa in Embodiment 1 of the present invention;

[0080] Figure 11 It is a graph showing the relationship between the weighted fabric stress coefficient and the axial strain under a confining pressure of 0.4MPa in Embodiment 1 of the present invention. Detailed Embodiments

[0081] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the specific embodiments.

[0082] Embodiment 1

[0083] This embodiment provides a method for designing the coarse aggregate gradation in asphalt mixtures, including:

[0084] S1: Construct the stacking models of coarse aggregates with different gradation ratios;

[0085] Specifically, in one embodiment, the coarse aggregate refers to the aggregate with a particle size ≥ 4.75 mm.

[0086] Specifically, step S1 includes:

[0087] S11: Use a 3D scanner to scan coarse aggregates of different particle sizes in each grade to form stl format files, and form a template template from the 3D scan files of different particle sizes;

[0088] Specifically, in one embodiment, taking asphalt mixture AC-13 as an example, its coarse aggregates include two grades of 4.75~9.5 mm and 9.5~13.2 mm, and their stl files after 3D scanning are respectively as Figure 1 、 Figure 2 shown.

[0089] S12: Generate top, bottom and lateral rigid walls to form an enclosed space (see Figure 3 ), and calculate the volume of the enclosed space;

[0090] S13: Use clump distribute to sequentially read the coarse aggregate particles of different particle sizes in the template template, determine the generated volume of each grade of coarse aggregate particles according to the preset gradation ratio relationship, calculate the number of coarse aggregate particles required to be generated for each grade according to the volume of a single coarse aggregate particle; the generation order is to generate the coarse aggregate particle models in sequence from the largest particle size to the smallest;

[0091] S14: Randomly place the generated coarse aggregate particle models in a predetermined area of the preset enclosed space to obtain a stacking model;

[0092] Specifically, in one embodiment, steps S12~S14 are completed in the 3D discrete element software PFC.

[0093] S2: Replace the second rigid wall with a flexible confining pressure wall, and servo to the preset target void ratio according to the preset contact stiffness, and remove the first rigid wall to obtain a 3D discrete element model;

[0094] Specifically, in one embodiment, step S2 includes:

[0095] S21: Replace the second rigid wall with a flexible confining pressure wall;

[0096] It should be noted that in the traditional 3D discrete element model, it is difficult to effectively apply radial load (confining pressure), which makes it difficult to effectively simulate the stress influence on asphalt mixture during the actual road use process. Based on this, the present invention replaces the second rigid wall with a flexible confining pressure wall (seeFigure 4 ), to simulate the influence of the radial load on the coarse aggregate aggregate. Specifically, the flexible confining wall is composed of a plurality of spherical particles, and each spherical particle can transmit pressure in the radial direction, so that the radial load applied to the model is conducted to the coarse aggregate particles through the spherical particles. In order to accurately evaluate the above simulation, it is necessary to specify in detail the specific number, diameter, and numbering rules of the spherical particles in the flexible confining wall to accurately extract the confining pressure on each spherical particle. Specifically as follows:

[0097] In one embodiment, the flexible confining wall includes multiple layers of spherical particle layers distributed along the axial direction;

[0098] The radius of the spherical particles in each layer of the spherical particle layer is calculated according to the following formula:

[0099]

[0100] where r i is the radius of the spherical particles in the i-th layer of the spherical particle layer, R i is the radius of the first coarse aggregate aggregate in the stacking model, N i is the number of spherical particles in the i-th layer of the spherical particle layer; specifically, for the convenience of calculation, the number of spherical particles in each layer of the spherical particle layer is set to 10 n , where n is a positive integer greater than or equal to 2. Further, it is set that the radii of all the spherical particles in the flexible confining wall are the same.

[0101] The number of layers of the spherical particle layer in the flexible confining wall is calculated according to the following formula:

[0102]

[0103] where C i is the number of layers of the spherical particle layer in the flexible confining wall, H i is the height of the flexible confining wall, r i is the radius of the spherical particles in the i-th layer of the spherical particle layer.

[0104] Specifically, in one embodiment, the spherical particles in each layer of the spherical particle layer in the flexible confining wall are numbered according to the rule from large to small. Exemplarily, in one embodiment, if the number of spherical particles in each layer of the spherical particle layer is 100, the starting number of the spherical particles in this layer can be set to 100000, and the number of the last spherical particle is 100099, and so on.

[0105] Further, in order to facilitate the calculation of the confining pressure on each spherical particle after applying a radial load in the later stage, it is also necessary to stipulate the numbering rules between adjacent layers. Specifically, the spherical particles in adjacent spherical particle layers are arranged in an interlocking or symmetric pattern; when the spherical particles are arranged in an interlocking pattern, six spherical particles are provided around each spherical particle; when the spherical particles are arranged symmetrically, four spherical particles are provided around each spherical particle (see Figures 5 - 7 ). The numbering rules between adjacent layers in each arrangement mode are described in detail below:

[0106] I. When the spherical particles are arranged in an interlocking pattern, the numbering rules for the spherical particles in even and odd layers are different;

[0107] When the spherical particles are arranged in an interlocking pattern, they are divided into head balls, regular balls, and tail balls. The head ball is the ball at the beginning of the numbering in each layer of small balls, and its number N0 can take an integer, and N0≥10 n (n is a positive integer ≥ 3), for example, 10000 or 100000; the tail ball is the ball at the end of the numbering in each layer of small balls, and its number N e can take an integer, and N e = N0 + N i - 1 (N i is the total number of spherical particles in the i-th layer), for example, 10099 or 100099; the regular balls are the small balls between the head ball and the tail ball, and the numbers are N0 + 1~N e - 1, for example, 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 and odd layers are different. Specifically as follows:

[0108] (I) See Figure 5 , the numbering rule for the spherical particles in the even layer is:

[0109] (1) When it is the head ball (the first ball) in the even layer, if the number of this ball is recorded as bid, then

[0110] the number of the small ball on the right side of this ball is bid + 1,

[0111] the number of the small ball on the left side of this ball is bid - 1 + N i ,

[0112] the number of the small ball on the upper right side of this ball is bid + 1 + N i ,

[0113] the number of the small ball on the upper left side of this ball is bid + N i ,

[0114] the number of the small ball on the lower right side of this ball is bid + 1 - N i ,

[0115] The number of the small ball at the lower left side of this ball is bid-N i .

[0116] (2)When it is the last ball of an even layer, if the number of this ball is denoted as bid, then

[0117] The number of the small ball on the right side of this ball is bid + 1 - N i ,

[0118] The number of the small ball on the left side of this ball is bid - 1,

[0119] The number of the small ball on the upper right side of this ball is bid + 1,

[0120] The number of the small ball on the upper left side of this ball is bid + N i ,

[0121] The number of the small ball on the lower right side of this ball is bid + 1 - N i -N i ,

[0122] The number of the small ball on the lower left side of this ball is bid - N i .

[0123] (3)When it is an ordinary ball of an even layer (the 2nd to the N i -1 ball), if the number of this ball is denoted as bid, then

[0124] The number of the small ball on the right side of this ball is bid + 1,

[0125] The number of the small ball on the left side of this ball is bid - 1,

[0126] The number of the small ball on the upper right side of this ball is bid + 1 + N i ,

[0127] The number of the small ball on the upper left side of this ball is bid + N i ,

[0128] The number of the small ball on the lower right side of this ball is bid + 1 - N i ,

[0129] The number of the small ball on the lower left side of this ball is bid - N i .

[0130] It should be noted that Figure 5 in the legend, N i = 100 is used for illustration, but the value of N i is not limited to this value.

[0131] (II)For the odd-numbered layers, the numbering rule of the spherical particles is as follows: Figure 6 Figure 6

[0132] (1)When it is the first ball of an odd layer, if the number of this ball is denoted as bid, then

[0133] the number of the ball on the right side of this ball is bid + 1,

[0134] the number of the ball on the left side of this ball is bid - 1 + N i ,

[0135] the number of the ball on the upper - right side of this ball is bid + N i ,

[0136] the number of the ball on the upper - left side of this ball is bid - 1 + N i +N i ,

[0137] the number of the ball on the lower - right side of this ball is bid - N i ,

[0138] the number of the ball on the lower - left side of this ball is bid - 1.

[0139] (2)When it is the last ball of an odd layer, if the number of this ball is denoted as bid, then

[0140] the number of the ball on the right side of this ball is bid + 1 - N i ,

[0141] the number of the ball on the left side of this ball is bid - 1,

[0142] the number of the ball on the upper - right side of this ball is bid + N i ,

[0143] the number of the ball on the upper - left side of this ball is bid - 1 + N i ,

[0144] the number of the ball on the lower - right side of this ball is bid - N i ,

[0145] the number of the ball on the lower - left side of this ball is bid - 1 - N i .

[0146] (3)When it is an ordinary ball (the 2nd to the (N - 1)th ball) of an odd layer, if the number of this ball is denoted as bid, then i -1 ball), then

[0147] the number of the ball on the right side of this ball is bid + 1,

[0148] the number of the ball on the left side of this ball is bid - 1,

[0149] the number of the ball on the upper - right side of this ball is bid + Ni ,

[0150] The number of the small ball on the upper left side of the ball is bid - 1 + N i ,

[0151] The number of the small ball on the lower right side of the ball is bid - N i ,

[0152] The number of the small ball on the lower left side of the ball is bid - 1 - N i .

[0153] It should be noted that Figure 6 in which N i = 100 is used for the legend illustration, but the value of N i is not limited to this.

[0154] II. When the spherical particles are symmetrically arranged, the numbering rule of the spherical particles is as follows:

[0155] When the spherical particles are symmetrically arranged, they are divided into head balls, regular balls, and tail balls. The head ball is the ball at the beginning of the numbering in each layer of small balls, and its number N0 can take 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 the numbering in each layer of small balls, and its number N e can take an integer, and N e = N0 + N i - 1 (N i is the total number of spherical particles in the i-th layer), for example, 10099 or 100099; the regular ball is the small ball between the head ball and the tail ball, and the number is N0 + 1 ~ N e - 1, for example, 10001 - 100098 or 100001 ~ 100098 (taking 100 spherical particles in each layer as an example, but not limited to this); the numbering rules for even layers and odd layers are the same, as Figure 7 shown, more specifically as follows:

[0156] (1) When it is the head ball (the first ball) in each layer, record the number of this ball as bid, then

[0157] the number of the small ball on the right side of this ball is bid + 1,

[0158] the number of the small ball on the left side of this ball is bid - 1 + N i ,

[0159] the number of the small ball directly above this ball is bid + N i ,

[0160] the number of the small ball directly below this ball is bid - N i .

[0161] (2)When it is the last ball of each layer, record the ball number as bid, then

[0162] the number of the small ball on the right side of this ball is bid + 1 - N i ,

[0163] the number of the small ball on the left side of this ball is bid - 1,

[0164] the number of the small ball directly above this ball is bid + N i ,

[0165] the number of the small ball directly below this ball is bid - N i .

[0166] (3)When it is an ordinary ball of each layer (the 2nd to the N - 1st ball), record the ball number as bid, then i -1 ball (the ordinary ball)), then

[0167] the number of the small ball on the right side of this ball is bid + 1,

[0168] the number of the small ball on the left side of this ball is bid - 1,

[0169] the number of the small ball directly above this ball is bid + N i ,

[0170] the number of the small ball directly below this ball is bid - N i .

[0171] It should be noted that Figure 7 in which N i = 100 is used for illustration by example, but the value of N i is not limited to this.

[0172] S22: Assign contact stiffness to each coarse aggregate particle in the first coarse aggregate aggregate with a linear model, and servo to the preset target void ratio;

[0173] Specifically, a linear contact bonding model can be used for simulation, and servo to the preset target void ratio under the given contact stiffness.

[0174] S3: Apply a preset radial load and a preset axial load to the three-dimensional discrete element model to obtain a mechanical response model;

[0175] Among them, when applying the radial load, calculate the confining pressure received by the spherical particles in the spherical particle layer near the middle according to the area equivalence principle. Specifically, extract the center coordinates of each spherical particle according to its number, calculate its center vector, and calculate the preset area according to the center vector, and then calculate the confining pressure applied to each spherical particle;

[0176] Exemplarily, the embeddment arrangement is as follows Figure 8 As shown, the regular hexagon is the calculation unit area. The regular hexagon is composed of six equilateral triangles. Then, the force applied to the regular hexagon area 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, and S1, S2, S3, S4, S5, and S6 are the areas of the six equilateral triangles respectively.

[0177] Taking the area S1 triangle composed of the small balls BP_0, BP_UR, and BP_R as an example, by extracting the center coordinates of the three small balls, calculating the center vector, calculating S1 according to the cross product of the center vectors, and then calculating the force value applied to S1. Among them, when extracting the center coordinates of each small ball, it is extracted according to the number of each small ball, and the numbering rule of the small balls refers to Figure 5 and Figure 6 .

[0178] The symmetric arrangement is as follows Figure 9 As shown, the square is the calculation unit area. The square is composed of four small squares. Then, the force applied to the square area is equivalently 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.

[0179] Taking the area of the square (S1 + S2 + S3 + S4) enclosed by the small balls BP_R, BP_L, BP_U, and BP_D as an example, by extracting the center coordinates of the three small balls BP_0, BP_L, and BP_U, calculating the center vector, calculating S1 according to half of the cross product of the center vectors, and then calculating the force value applied to S1. Among them, when extracting the center coordinates of each small ball, it is extracted according to the number of each small ball, and the numbering rule of the small balls refers to Figure 7 .

[0180] Specifically, after applying the preset radial load and the 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. The simulation is carried out by the discrete element software PFC, and then the normal contact force, tangential contact force, branch vector, normal branch vector, tangential branch vector, and normal vector of each contact are extracted. It should be noted that the contact here is different from the coarse aggregate particles. Each coarse aggregate particle may form multiple contacts under the action of multiple coarse aggregate particles around it.

[0181] S4: Construct the fabric anisotropy coefficient according to the normal contact force, tangential contact force, normal branch vector, branch vector, tangential branch vector, and normal vector

[0182] Specifically, S5 includes

[0183] S41: Calculate the stress tensor and fabric tensor based on the normal contact force, normal vector, tangential vector, and branch vector, and calculate the anisotropy coefficient based on the stress tensor and fabric tensor;

[0184] Among them, the stress tensor, fabric tensor, and anisotropy coefficient are calculated according to the following formula set:

[0185]

[0186]

[0187]

[0188]

[0189] is the stress tensor of the second coarse aggregate aggregate, is the fabric tensor of the second coarse aggregate aggregate, is the second-order structure tensor of the second coarse aggregate aggregate, is the anisotropy coefficient of the second coarse aggregate aggregate, is the normal contact force of the c-th contact, is the branch vector of the c-th contact, V is the volume of the second coarse aggregate aggregate, 、 are the projection lengths of the unit normal vector of the c-th contact in the k direction and l direction respectively, is the total number of contacts of the coarse aggregate particles in the mechanical response model.

[0190] It should be noted that in the present invention, the normal contact force, tangential contact force, normal vector, tangential vector, branch vector, normal branch vector, and tangential branch vector are all vectors, and their magnitudes and lengths refer to the modulus of the vector. The unit normal vector refers to the vector obtained by dividing the normal vector by its modulus, and other unit vectors are calculated similarly.

[0191] S42: Calculate the structure tensor of the normal contact force, the structure tensor of the tangential contact force, the structure tensor of the normal branch vector, and the structure tensor of the tangential branch vector;

[0192] Among them, the calculation method of the structure tensor of the normal contact force is as follows:

[0193]

[0194] Among them, is the structure tensor of the normal contact force of the second coarse aggregate aggregate, is the magnitude of the normal contact force of the c-th contact, 、 The projection magnitudes of the unit normal contact force of the c-th contact in the i-direction and j-direction respectively, is the second-order structure tensor of the second coarse aggregate aggregate, 、 The projection lengths of the unit normal vector of the c-th contact in the k-direction and l-direction respectively, is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0195] The calculation method of the structure tensor of the tangential contact force is as follows:

[0196]

[0197] Among them, is the structure tensor of the tangential contact force of the second coarse aggregate aggregate, is the magnitude of the tangential contact force of the c-th contact, 、 The projection magnitudes of the unit tangential contact force of the c contacts in the i-direction and j-direction respectively, is the second-order structure tensor of the second coarse aggregate aggregate, 、 The projection lengths of the unit normal vector of the c-th contact in the k-direction and l-direction respectively, is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0198] Among them, the calculation method of the structure tensor of the normal branch vector is as follows:

[0199]

[0200] Among them, is the structure tensor of the normal branch vector of the second coarse aggregate aggregate, is the length of the normal branch vector of the c-th contact, is the second-order structure tensor of the second coarse aggregate aggregate, 、 The projection lengths of the unit normal branch vector of the c-th contact in the i-direction and j-direction respectively, 、 The projection lengths of the unit normal vector of the c-th contact in the k-direction and l-direction respectively, is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0201] Among them, the calculation method of the structure tensor of the tangential branch vector is as follows:

[0202]

[0203] Among them, is the structural tensor of the tangential branch vector of the second coarse aggregate aggregate is the length of the tangential branch vector of the c-th contact 、 are the projected lengths of the unit tangential branch vector of the c-th contact in the i and j directions is the second-order structural tensor of the second coarse aggregate aggregate 、 are the projected lengths of the unit normal vector of the c-th contact in the k and l directions, respectively is the total number of contacts of the coarse aggregate particles in the mechanical response model

[0204] S43: Calculate the normal contact force fabric anisotropy coefficient, tangential contact force fabric anisotropy coefficient, normal branch vector fabric anisotropy coefficient, and tangential branch vector fabric anisotropy coefficient that characterize the degree of anisotropy in different directions

[0205] Among them, the calculation method of the normal contact force fabric anisotropy coefficient is as follows

[0206]

[0207] In the formula is the normal contact force anisotropy coefficient of the second coarse aggregate aggregate and are both the second-order structural tensors of the normal contact force of the second coarse aggregate aggregate and are both the deviatoric tensors of the stress tensor of the second coarse aggregate aggregate is the structural tensor of the normal contact force of the second coarse aggregate aggregate of the deviatoric tensor is the average magnitude of the normal contact force of the second coarse aggregate aggregate is the magnitude of the normal contact force of the c-th contact is the total number of contacts of the coarse aggregate particles in the mechanical response model

[0208] Among them, the calculation method of the tangential contact force fabric anisotropy coefficient is as follows

[0209]

[0210] In the formula is the tangential contact force fabric anisotropy coefficient of the second coarse aggregate aggregate is and the standard value of the double dot product; sign() is the sign function. When > 0, sign( ) = 1; when < 0, sign( ) = -1; and are both the second - order structure tensors of the tangential contact force of the second coarse aggregate aggregate; and are both the deviatoric tensors of the stress tensor of the second coarse aggregate aggregate; is the structure tensor of the tangential contact force of the second coarse aggregate aggregate 's deviatoric tensor, is the magnitude of the average tangential contact force of the second coarse aggregate aggregate, is the magnitude of the tangential contact force of the c - th contact, is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0211] Among them, the calculation method of the normal branch vector fabric anisotropy coefficient is as follows:

[0212]

[0213] In the formula, is the normal branch vector fabric anisotropy coefficient of the second coarse aggregate aggregate, is and 's standard value of the double - dot product; sign() is the sign function. When > 0, sign( ) = 1; when < 0, sign( ) = -1; and are both the second - order structure tensors of the normal branch vectors of the second coarse aggregate aggregate; and are both the deviatoric tensors of the stress tensor of the second coarse aggregate aggregate, is the structure tensor of the normal branch vector 's deviatoric tensor, is the average length of the normal branch vectors of the second coarse aggregate aggregate, is the length of the normal branch vector of the c - th contact, is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0214] Among them, the calculation method of the tangential branch vector fabric anisotropy coefficient is as follows:

[0215]

[0216] In the formula, is the tangential branch vector fabric anisotropy coefficient of the second coarse aggregate aggregate, is and 's standard value of the double - dot product; sign() is the sign function. When > 0, sign( ) = 1; When < 0, sign( ) = -1; and are both the second-order structure tensors of the tangential branch vectors of the second coarse aggregate aggregate; and are both the deviatoric tensors of the stress tensors of the second coarse aggregate aggregate, is the structure tensor of the tangential branch vectors of the second coarse aggregate aggregate of the deviatoric tensor, is the average length of the tangential branch vectors of the second coarse aggregate aggregate, is the length of the tangential branch vector of the c-th contact, is the total number of contacts of the coarse aggregate particles in the mechanical response model.

[0217] S5: Construct the weighted fabric stress coefficient of the second coarse aggregate aggregate according to the fabric anisotropy coefficient;

[0218] Specifically, the weighted fabric anisotropy coefficient is calculated according to the following formula:

[0219] ;

[0220] In the formula, is the weighted fabric anisotropy coefficient of the second coarse aggregate aggregate, is the anisotropy coefficient of the second coarse aggregate aggregate, is the normal contact force fabric anisotropy coefficient of the second coarse aggregate aggregate, is the normal branch vector fabric anisotropy coefficient of the second coarse aggregate aggregate, is the tangential branch vector fabric anisotropy coefficient of the second coarse aggregate aggregate, is the tangential contact force fabric anisotropy coefficient of the second coarse aggregate aggregate.

[0221] S6: Determine the optimal gradation of each grade of coarse aggregate according to the relationship between the weighted fabric stress coefficient of the second coarse aggregate aggregate and its axial strain under the preset axial load.

[0222] Specifically, take each coarse aggregate with different particle sizes, mix them according to different gradation ratios, generate a three-dimensional discrete element model according to the steps of S1~S5, change different radial loads and axial loads, compare and analyze the meso-mechanical properties of the coarse aggregate aggregate under different gradation ratios, and select the gradation with the best road performance.

[0223] Exemplarily, in an embodiment of the present invention, the relationship between the weighted fabric anisotropy coefficient at 9.5~13.2mm:4.75~9.5mm = 3:7, 4:6, 5:5, 6:4 under confining pressures of 0.2MPa and 0.4MPa is as Figure 10 , Figure 11 shown.

[0224] According to Figure 10 , Figure 11 , when 9.5~13.2mm:4.75~9.5mm = 4:6, the mechanical properties of the coarse aggregate assembly are the best. Therefore, the ratio of coarse aggregate 9.5~13.2mm to 4.75~9.5mm is determined to be 4:6.

[0225] The above is the preferred embodiment of the invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A method for designing the gradation of coarse aggregate in asphalt mixture, 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 preset contact stiffness is servoed to a preset target void ratio, 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 contact force, tangential contact force, normal vector, tangential vector, branch vector, normal branch vector and tangential branch vector of each contact; Constructing a structural anisotropy coefficient according to the normal contact force, the tangential contact force, the normal vector, the tangential vector, the branch vector, the normal branch vector and the tangential branch vector; Constructing a weighted structural anisotropy coefficient of a second coarse aggregate assembly according to the structural anisotropy coefficient; The optimal gradation of each level of coarse aggregate is determined according to the relationship between the weighted structural 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 method for designing the gradation of coarse aggregate in asphalt mixture according to claim 1, characterized in that: The steps of constructing a stacking model of coarse aggregates with different gradation ratios include: Extract geometric parameters of coarse aggregate particles; Filling coarse aggregates of various grades with preset gradation ratios into a closed space formed by the first rigid wall and the second rigid wall to obtain a stacking model; The steps of replacing the second rigid wall with a flexible confining pressure wall, servoing 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 include: The second rigid wall is replaced by a flexible confining pressure wall; Using a linear model, each coarse aggregate particle in the first coarse aggregate assembly is given a contact stiffness, and the contact stiffness is servoed to a preset target porosity; The first rigid wall is removed to obtain a three-dimensional discrete element model.

3. The method for designing the gradation of coarse aggregate in asphalt mixture according to claim 1 or 2, characterized in that: The flexible confining pressure wall comprises multiple layers of spherical particles distributed along the axial direction; The radius of the spherical particles in each spherical particle layer is calculated according to the following formula: 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; The number of spherical particle layers in the flexible confining pressure wall is calculated according to the following formula: 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.

4. The method for designing the gradation of coarse aggregate in asphalt mixture according to claim 1, characterized in that: In 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, when applying the radial load, the confining pressure exerted on the spherical particles in the spherical particle layer is calculated according to the area equivalence principle.

5. The method for designing the gradation of coarse aggregate in asphalt mixture according to claim 1, characterized in that: The step of constructing the fabric anisotropy coefficient according to the normal contact force, the tangential contact force, the normal vector, the branch vector, the tangential vector, the normal branch vector and the tangential branch vector comprises the steps of calculating the stress tensor and the fabric tensor according to the normal contact force, the normal vector, the tangential vector and the branch vector, and calculating the anisotropy coefficient according to the stress tensor and the fabric tensor; Among them, the stress tensor, fabric tensor, and anisotropy coefficient are calculated according to the following formula group: is the stress tensor of the second coarse aggregate, is the fabric tensor of the second coarse aggregate, is the second-order structure tensor of the second coarse aggregate, is the anisotropy coefficient of the second coarse aggregate, is the normal contact force of the cth contact, is the branch vector of the cth contact, V is the volume of the second coarse aggregate, , are the projection lengths of the unit normal vector of the cth contact in the k direction and the l direction, respectively, is the total contact number of coarse aggregate particles in the mechanical response model.

6. The method for designing the gradation of coarse aggregate in asphalt mixture according to claim 5, 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, the branch vector, the normal branch vector and the tangential branch vector also includes the step of calculating the structural tensor of the normal contact force, the structural tensor of the tangential contact force, the structural tensor of the normal branch vector and the structural tensor of the tangential branch vector; Among them, the structural tensor of the normal contact force is calculated as follows: in, is the structural tensor of the normal contact force of the second coarse aggregate assembly, is the normal contact force of the cth contact, , are the projections of the unit normal contact force of the cth contact in the i and j directions respectively, is the second-order structure tensor of the second coarse aggregate, , are the projection lengths of the unit normal vector of the cth contact in the k direction and the l direction, respectively, is the total contact number of coarse aggregate particles in the mechanical response model; The structural tensor for the tangential contact force is calculated as follows: in, is the structural tensor of the tangential contact force of the second coarse aggregate assembly, is the magnitude of the tangential contact force of the cth contact, , are the projections of the unit tangential contact forces of c contacts in the i and j directions, is the second-order structure tensor of the second coarse aggregate, , are the projection lengths of the unit normal vector of the cth contact in the k direction and the l direction, respectively, is the total contact number of coarse aggregate particles in the mechanical response model; Among them, the calculation method of the structure tensor of the normal branch vector is as follows: in, is the structural tensor of the normal branch vector of the second coarse aggregate, is the length of the normal branch vector of the cth contact, is the second-order structure tensor of the second coarse aggregate, , are the projection lengths of the unit normal branch vector of the cth contact in the i and j directions, respectively. , are the projection lengths of the unit normal vector of the cth contact in the k direction and the l direction, respectively, is the total contact number of coarse aggregate particles in the mechanical response model; Among them, the calculation method of the structure tensor of the tangent branch vector is as follows: in, is the structural tensor of the tangential branch vector of the second coarse aggregate, is the length of the tangential branch vector of the cth contact, , is the projection length of the unit tangential branch vector of the cth contact in the i and j directions, is the second-order structure tensor of the second coarse aggregate, , are the projection lengths of the unit normal vector of the cth contact in the k direction and the l direction, respectively, is the total contact number of coarse aggregate particles in the mechanical response model.

7. The method for designing the gradation of coarse aggregate in asphalt mixture according to claim 6, characterized in that: The step of constructing the composition anisotropy coefficient according to the normal contact force, tangential contact force, normal vector, tangential vector, branch vector, normal branch vector and tangential branch vector also includes: calculating the composition anisotropy coefficient of the normal contact force, the composition anisotropy coefficient of the tangential contact force, the composition anisotropy coefficient of the normal branch vector and the composition anisotropy coefficient of the tangential branch vector, which characterize the degree of anisotropy distributed in different directions; Among them, the calculation method of the normal contact force component anisotropy coefficient is as follows: In the formula, is the normal contact force anisotropy coefficient of the second coarse aggregate, and are the second-order structural tensors of the normal contact force of the second coarse aggregate, and They are all deviatoric tensors of the stress tensor of the second coarse aggregate aggregate; is the structural tensor of the normal contact force of the second coarse aggregate The partial tensor of is the average normal contact force of the second coarse aggregate, is the magnitude of the normal contact force of the cth contact, is the total contact number of coarse aggregate particles in the mechanical response model; Among them, the calculation method of the tangential contact force component anisotropy coefficient is as follows: In the formula, is the structural anisotropy coefficient of the tangential contact force of the second coarse aggregate, for and The standard value of the double dot product; sign() is the sign function, when >0,sign( ) = 1; when <0, sign( ) = -1; and They are the second-order structural tensors of the tangential contact force of the second coarse aggregate assembly; and They are all deviatoric tensors of the stress tensor of the second coarse aggregate aggregate; is the structural tensor of the tangential contact force of the second coarse aggregate The partial tensor of is the average tangential contact force of the second coarse aggregate, is the magnitude of the tangential contact force of the cth contact, is the total contact number of coarse aggregate particles in the mechanical response model; Among them, the calculation method of the normal branch vector structural anisotropy coefficient is as follows: In the formula, is the normal branch vector structural anisotropy coefficient of the second coarse aggregate, for and The standard value of the double dot product; sign() is the sign function, when >0,sign( ) = 1; when <0, sign( ) = -1; and are the second-order structure tensors of the normal branch vectors of the second coarse aggregate; and are the deviatoric tensors of the stress tensor of the second coarse aggregate, is the structure tensor of the normal branch vector The partial tensor of is the average normal branch vector length of the second coarse aggregate, is the length of the normal branch vector of the cth contact, is the total contact number of coarse aggregate particles in the mechanical response model; Among them, the calculation method of the tangential branch vector structural anisotropy coefficient is as follows: In the formula, is the structural anisotropy coefficient of the tangential branch vector of the second coarse aggregate, for and The standard value of the double dot product; sign() is the sign function, when >0,sign( ) = 1; when <0, sign( ) = -1; and are the second-order structure tensors of the tangential branch vectors of the second coarse aggregate; and are the deviatoric tensors of the stress tensor of the second coarse aggregate, is the structural tensor of the tangential branch vector of the second coarse aggregate The partial tensor of is the average tangential branch vector length of the second coarse aggregate, is the length of the tangential branch vector of the cth contact, is the total contact number of coarse aggregate particles in the mechanical response model.

8. The method for designing the gradation of coarse aggregate in asphalt mixture according to claim 6, characterized in that: The weighted structural anisotropy coefficient is calculated according to the following formula: ； In the formula, is the weighted structural anisotropy coefficient of the second coarse aggregate, is the anisotropy coefficient of the second coarse aggregate, is the normal contact force structural anisotropy coefficient of the second coarse aggregate assembly, is the normal branch vector structural anisotropy coefficient of the second coarse aggregate, is the structural anisotropy coefficient of the tangential branch vector of the second coarse aggregate, is the structural anisotropy coefficient of the tangential contact force of the second coarse aggregate assembly.

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 of any one of claims 1 to 8 are implemented.

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