Asphalt Mixture Design Method, Computer Equipment and Storage Medium

Abstract

The present invention discloses an asphalt mixture design method, a computer device and a storage medium, relating to the field of asphalt mixtures. Among them, the asphalt mixture includes mineral materials and asphalt, and the mineral materials include coarse aggregate mixtures, fine aggregate mixtures and mineral powder; the design method includes: constructing a three-dimensional discrete element model; applying a preset radial load and a preset axial load to obtain a mechanical response model; multiple contacts are formed among the coarse aggregate particles in the mechanical response model under the action of the radial load and the axial load, and the contact force and vector of each contact are extracted; constructing a weighted fabric anisotropy coefficient; determining the optimal gradation of each size of coarse aggregate according to the relationship between the weighted fabric anisotropy coefficient and its axial strain under the preset load; determining the gradation of each size of fine aggregate in the fine aggregate mixture according to the packing rule; determining the proportions of the coarse aggregate mixture and the fine aggregate mixture. The present invention solves the defect that the volume design method has poor correlation with 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 design method for 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 then 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 based on mechanical properties.

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

[0004] I. 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 volumes of fine aggregates, asphalt, mineral powder, and the void volume of the designed mixture is equal to the measured void volume of 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 using 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 aggregates and fine aggregates, 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 using 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 within the gradation range that meet the volume parameter requirements. 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 an asphalt mixture design method, a computer device and a storage medium, which have a strong correlation with road performance and the designed asphalt mixture has excellent mechanical properties.

[0008] To solve the technical problems of the present invention, the present invention provides an asphalt mixture design method. The asphalt mixture includes mineral aggregates and asphalt, and the mineral aggregates include coarse aggregate mixtures, fine aggregate mixtures and mineral powder. The design method includes:

[0009] Construct a packing model of coarse aggregates with different gradation ratios. The packing 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 periphery of the first coarse aggregate aggregate.

[0010] Replace the second rigid wall with a flexible confining wall and servo it to a preset target void ratio according to a preset contact stiffness, and remove 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] Apply 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] Construct 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] Construct a weighted fabric anisotropy coefficient of the second coarse aggregate aggregate according to the fabric anisotropy coefficient.

[0014] Determine the optimal gradation of each grade of coarse aggregates 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 synthesize the coarse aggregate mixture with the optimal gradation.

[0015] Determine the gradation of each grade of fine aggregates in the fine aggregate mixture according to the packing rule.

[0016] Determine the proportions of the coarse aggregate mixture and the fine aggregate mixture under the preset asphalt proportion and mineral aggregate proportion according to the packing rule.

[0017] As an improvement of the above technical solution, in the step of determining the gradation of each grade of fine aggregates in the fine aggregate mixture according to the packing rule, the gradation of each grade of fine aggregates in the fine aggregate mixture is determined according to the following formula set:

[0018]

[0019] w i = P i - P i-1

[0020]

[0021] where w i is the weight percentage of the i-th fine aggregate in the fine aggregate mixture excluding the last fine aggregate, d i+1 is the maximum nominal size of the (i + 1)-th fine aggregate, D max is the maximum nominal size of the fine aggregate, w f is the weight percentage of the fine aggregate with the smallest particle size in the fine aggregate mixture, t is the total number of fine aggregate grades in the fine aggregate mixture, n is a constant, when d i+1 > 0.075 mm, the value of n is 0.4 - 0.55, when d i+1 ≤ 0.075 mm, the value of n is 0.6 - 0.8; P i is the sieve passing rate of the i-th fine aggregate, the aperture of the sieve is the maximum nominal size of the (i + 1)-th fine aggregate, and the maximum nominal size of the (i + 1)-th fine aggregate is smaller than that of the i-th fine aggregate.

[0022] As an improvement of the above technical solution, in the step of determining the proportions of the coarse aggregate mixture and the fine aggregate mixture under the preset asphalt proportion and the preset mineral powder proportion according to the filling rule, the proportions of the coarse aggregate mixture and the fine aggregate mixture in the mineral aggregate are determined according to the following set of formulas:

[0023] q c + q f + q p = 100%

[0024]

[0025] where q c is the mass percentage of the coarse aggregate mixture in the mineral aggregate, q f is the mass percentage of the fine aggregate mixture in the mineral aggregate, q p is the mass percentage of the mineral powder in the mineral aggregate, q a is the mass percentage of the asphalt in the asphalt mixture, d sc is the compacted density of the coarse aggregate mixture, V ca is the void ratio of the coarse aggregate mixture, V vs is the designed void ratio of the asphalt mixture, d tf is the apparent density of the fine aggregate mixture, d tp is the apparent density of the mineral powdera is the density of asphalt.

[0026] As an improvement to the above technical solution, the steps of constructing the stacking model of coarse aggregates with different gradation ratios include: extracting the geometric parameters of coarse aggregate particles;

[0027] Filling coarse aggregates of each grade 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;

[0028] The steps of replacing the second rigid wall with a flexible confining pressure wall and servoing to a preset target void ratio according to the preset contact stiffness and then removing the first rigid wall to obtain a three-dimensional discrete element model include:

[0029] Replacing the second rigid wall with a flexible confining pressure wall;

[0030] Assigning contact stiffness to each coarse aggregate particle in the first coarse aggregate aggregate with a linear model and servoing to the preset target porosity;

[0031] Removing the first rigid wall to obtain a three-dimensional discrete element model; the flexible confining pressure wall includes multiple layers of spherical particle layers distributed axially;

[0032] The radius of the spherical particles in each layer of spherical particle layers is calculated according to the following formula:

[0033]

[0034] where, r i is the radius of the spherical particles in the i-th layer of spherical particle layers, 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 spherical particle layers;

[0035] The number of layers of spherical particle layers in the flexible confining pressure wall is calculated according to the following formula:

[0036] C i = H i / 2r i

[0037] where, C i is the number of layers of spherical particle layers in the flexible confining pressure wall, H i is the height of the flexible confining pressure wall, r i is the radius of the spherical particles in the i-th layer of spherical particle layers.

[0038] 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 on the spherical particles in the spherical particle layer is calculated according to the area equivalence principle.

[0039] 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 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;

[0040] Among them, the stress tensor, fabric tensor and anisotropy coefficient are calculated according to the following set of formulas:

[0041]

[0042] σ kl is the stress tensor of the second coarse aggregate aggregate, φ kl is the fabric tensor of the second coarse aggregate aggregate, is the second-order structure tensor of the second coarse aggregate aggregate, a c 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 the l direction respectively, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model.

[0043] 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;

[0044] Among them, the calculation method of the structure tensor of the normal contact force is as follows:

[0045]

[0046] 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, f i n 、 are the projection magnitudes of the unit normal contact force of the c-th contact in the i direction and the 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 the l direction respectively, N cis the total number of contacts of coarse aggregate particles in the mechanical response model;

[0047] The calculation method of the structural tensor of the tangential contact force is as follows:

[0048]

[0049] where, is the structural tensor of the tangential contact force of the second coarse aggregate aggregate, f t c is the magnitude of the tangential contact force of the c-th contact, f i t 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, are the projection lengths of the unit normal vector of the c-th contact in the k-direction and l-direction respectively, N c is the total number of contacts of coarse aggregate particles in the mechanical response model;

[0050] where, the calculation method of the structural tensor of the normal branch vector is as follows:

[0051]

[0052] where, 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, are the projection lengths of the unit normal branch vector of the c-th contact in the i-direction and j-direction respectively, are the projection lengths of the unit normal vector of the c-th contact in the k-direction and l-direction respectively, N c is the total number of contacts of coarse aggregate particles in the mechanical response model;

[0053] where, the calculation method of the structural tensor of the tangential branch vector is as follows:

[0054]

[0055] where, 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, is the projection length 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, They are the projection lengths of the unit normal vector of the c-th contact in the k direction and the l direction, respectively, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model.

[0056] 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 anisotropy degree of distribution in different directions;

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

[0058]

[0059] In the formula, a n 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, σ i ' j and σ' mn are both the deviatoric tensors of the stress tensor of the second coarse aggregate aggregate; is the deviatoric tensor of the structure tensor of the normal contact force of the second coarse aggregate aggregate of, 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, N c 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 contact force fabric anisotropy coefficient is as follows:

[0061]

[0062] In the formula, a t is the tangential contact force fabric anisotropy coefficient of the second coarse aggregate aggregate, S r2 is the standard value of the double dot product with σ i '; sign() is the sign function. When S j > 0, sign(S r2 ) = 1; when S r2 < 0, sign(S r2 ) = -1; r2 ) = -1; and They are all the second-order structure tensors of the tangential contact forces of the second coarse aggregate assemblage; σ i ' j and σ' mn are all the deviatoric tensors of the stress tensors of the second coarse aggregate assemblage; is the structure tensor of the tangential contact forces of the second coarse aggregate assemblage of the deviatoric tensor, is the magnitude of the average tangential contact force of the second coarse aggregate assemblage, f t c is the magnitude of the tangential contact force of the c-th contact, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0063] Among them, the calculation method of the normal branch vector fabric anisotropy coefficient is as follows:

[0064]

[0065] In the formula, a dn is the normal branch vector fabric anisotropy coefficient of the second coarse aggregate assemblage, S r3 is the standard value of the double dot product with σ i ' j ; sign() is the sign function. When S r3 > 0, sign(S r3 ) = 1; when S r3 < 0, sign(S r3 ) = -1; and are all the second-order structure tensors of the normal branch vectors of the second coarse aggregate assemblage; σ i ' j and σ' mn are all the deviatoric tensors of the stress tensors of the second coarse aggregate assemblage, is the deviatoric tensor of the structure tensor of the normal branch vector , is the average length of the normal branch vectors of the second coarse aggregate assemblage, is the length of the normal branch vector of the c-th contact, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0066] Among them, the calculation method of the tangential branch vector fabric anisotropy coefficient is as follows:

[0067]

[0068] In the formula, a dt is the tangential branch vector fabric anisotropy coefficient of the second coarse aggregate assemblage, S r4 is the double dot product with σi ' j Standard value of the double dot product; sign() is the sign function. When S r4 > 0, sign(S r4 ) = 1; when S r4 < 0, sign(S r4 ) = -1; and are both the second - order structure tensors of the tangential branch vectors of the second coarse aggregate aggregate; σ i ' j and σ' mn are both the deviatoric tensors of the stress tensors of the second coarse aggregate aggregate, is the deviatoric tensor of the structure tensor of the tangential branch vectors of the second coarse aggregate aggregate of, 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, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model.

[0069] As an improvement of the above - mentioned technical solution, the weighted fabric anisotropy coefficient is calculated according to the following formula:

[0070] τ = 0.4(a c + a n + a dn + 1.5a dt + 1.5a t );

[0071] In the formula, τ is the weighted fabric anisotropy coefficient of the second coarse aggregate aggregate, a c is the anisotropy coefficient of the second coarse aggregate aggregate, a n is the fabric anisotropy coefficient of the normal contact force of the second coarse aggregate aggregate, a dn is the fabric anisotropy coefficient of the normal branch vectors of the second coarse aggregate aggregate, a dt is the fabric anisotropy coefficient of the tangential branch vectors of the second coarse aggregate aggregate, a t is the fabric anisotropy coefficient of the tangential contact force of the second coarse aggregate aggregate.

[0072] 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 - mentioned design method are implemented.

[0073] 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 steps of the above - mentioned grading design method are implemented.

[0074] Implementing the present invention has the following beneficial effects:

[0075] 1. In the design method of the asphalt mixture gradation of the present invention, the coarse aggregate and the fine aggregate are designed separately. The coarse aggregate is designed by the theoretical simulation method, and the fine aggregate is designed by the filling method. The division of labor is clear and the functions are prominent. The gradation designed according to the proposed design method has excellent mechanical properties, high density and excellent road performance.

[0076] 2. In the design method of the coarse aggregate gradation in 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 uses 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 uses the theoretical method, which effectively solves the disadvantage of poor correlation between the volume design method and the road performance, and the designed gradation has excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 is the three-dimensional schematic diagram after scanning the 4.75 - 9.5 mm coarse aggregate in Embodiment 1 of the present invention;

[0078] Figure 2 is the three-dimensional schematic diagram after scanning the 9.5 - 13.2 mm coarse aggregate in Embodiment 1 of the present invention;

[0079] Figure 3 is the schematic diagram of the closed space in Embodiment 1 of the present invention;

[0080] Figure 4 is the schematic diagram of the flexible confining pressure wall in Embodiment 1 of the present invention;

[0081] Figure 5 is the schematic diagram of the numbering rules of the head balls, regular balls, and tail balls in the even layers when the spherical particles are arranged in an interlocking manner in Embodiment 1 of the present invention;

[0082] Figure 6 is the schematic diagram of the numbering rules of the head balls, regular balls, and tail balls in the odd layers when the spherical particles are arranged in an interlocking manner in Embodiment 1 of the present invention;

[0083] Figure 7 is the schematic diagram of the numbering rules of the head balls, regular balls, and tail balls when the spherical particles are arranged symmetrically in Embodiment 1 of the present invention;

[0084] Figure 8 is the schematic diagram of the calculation rules of the unit area when the spherical particles are arranged in an interlocking manner in Embodiment 1 of the present invention;

[0085] Figure 9It is a schematic diagram of the calculation rule of the unit area when the spherical particles are symmetrically arranged in Embodiment 1 of the present invention;

[0086] Figure 10 It is a graph showing the relationship between the weighted fabric stress coefficient and the axial strain under a confining pressure of 0.2 MPa in Embodiment 1 of the present invention;

[0087] Figure 11 It is a graph showing the relationship between the weighted fabric stress coefficient and the axial strain under a confining pressure of 0.4 MPa in Embodiment 1 of the present invention. Specific Embodiments

[0088] 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 specific embodiments.

[0089] Embodiment 1

[0090] This embodiment provides a design method for the coarse aggregate mixture gradation in asphalt mixture, including:

[0091] S1: Construct a stacking model of coarse aggregates with different gradation ratios;

[0092] Specifically, in one embodiment, the coarse aggregate refers to the aggregate with a particle size ≥ 4.75 mm.

[0093] Specifically, step S1 includes:

[0094] S11: Use a 3D scanner to scan coarse aggregates of different particle sizes in each grade to form an stl format file, and form a template template from the 3D scan files of different particle sizes;

[0095] 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 3D scanned stl files are respectively as Figure 1 、 Figure 2 shown.

[0096] S12: Generate top, bottom, and lateral rigid walls to form a closed space (see Figure 3 ), and calculate the volume of the closed space;

[0097] S13: Use clump distribute (block generation) 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 particle size;

[0098] S14: Randomly place the generated coarse aggregate particle model in a predetermined area of a preset enclosed space to obtain a stacking model;

[0099] Specifically, in one embodiment, steps S12 - S14 are completed in the three - dimensional discrete element software PFC.

[0100] S2: Replace the second rigid wall with a flexible confining pressure wall, and servo to a preset target void ratio according to the preset contact stiffness, and remove the first rigid wall to obtain a three - dimensional discrete element model;

[0101] Specifically, in one embodiment, step S2 includes:

[0102] S21: Replace the second rigid wall with a flexible confining pressure wall;

[0103] It should be noted that in the traditional three - dimensional discrete element model, it is difficult to effectively apply radial loads (confining pressures), which makes it difficult to effectively simulate the stress effects on asphalt mixtures during the actual road - using process. Based on this, the present invention replaces the second rigid wall with a flexible confining pressure wall (see Figure 4 ) to simulate the influence of radial loads on the coarse aggregate mixture. Specifically, the flexible confining pressure wall is composed of multiple spherical particles, and each spherical particle can transfer 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. 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 pressure wall to accurately extract the confining pressure on each spherical particle. Specifically as follows:

[0104] In one embodiment, the flexible confining pressure wall includes multiple layers of spherical particle layers distributed along the axial direction;

[0105] The radius of the spherical particles in each layer of spherical particle layer is calculated according to the following formula:

[0106]

[0107] 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 stacking model, N i is the number of spherical particles in the i - th layer of spherical particle layer; specifically, for the convenience of calculation, the number of spherical particles in each layer of 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 spherical particles in the flexible confining pressure wall are the same.

[0108] The number of layers of spherical particle layers in the flexible confining pressure wall is calculated according to the following formula:

[0109] C i = H i / 2r i

[0110] Wherein, C i is the number of layers of spherical particle layers in the flexible confining pressure wall, H i is the height of the flexible confining pressure wall, and r i is the radius of the spherical particles in the i-th layer of spherical particle layers.

[0111] Specifically, the spherical particles in each layer of spherical particle layers in the flexible confining pressure 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 spherical particle layers is 100, the starting number of the spherical particles in this layer can be set as 100000, and the number of the last spherical particle is 100099, and so on.

[0112] Furthermore, in order to facilitate the calculation of the confining pressure received by each spherical particle after applying the radial load in the later stage, it is also necessary to stipulate the numbering rule between adjacent layers. Specifically, the spherical particles in adjacent spherical particle layers are arranged in an interlocking or symmetric manner; when the spherical particles are arranged in an interlocking manner, 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 to 7 ). The numbering rules between adjacent layers in each arrangement mode are described in detail below:

[0113] I. When the spherical particles are arranged in an interlocking manner, the numbering rules of the spherical particles in the even layers and the odd layers are different;

[0114] When the spherical particles are arranged in an interlocking manner, 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), exemplarily 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), exemplarily such as 10099 or 100099; the regular balls are the small balls between the head ball and the tail ball, and the number is N0 + 1 to N e - 1, exemplarily such as 10001 to 10098 or 100001 to 100098 (taking 100 spherical particles in each layer as an example, but not limited to this); the numbering rules of the even layers and the odd layers are different. Specifically as follows:

[0115] (1) See Figure 5 , the numbering rule of the spherical particles in the even layer is:

[0116] (1) When it is an even - numbered layer's first ball, if the ball number is bid, then

[0117] the number of the ball on the right side of this ball is bid + 1,

[0118] the number of the ball on the left side of this ball is bid - 1+N i ,

[0119] the number of the ball on the upper - right side of this ball is bid + 1+N i ,

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

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

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

[0123] (2) When it is an even - numbered layer's last ball, if the ball number is bid, then

[0124] the number of the ball on the right side of this ball is bid + 1 - N i ,

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

[0126] the number of the ball on the upper - right side of this ball is bid + 1,

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

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

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

[0130] (3) When it is an even - numbered layer's ordinary ball (the 2nd to the N i -1 ball), if the ball number is bid, then

[0131] the number of the ball on the right side of this ball is bid + 1,

[0132] the number of the ball on the left side of this ball is bid - 1,

[0133] The number of the small ball on the upper right side of this ball is bid + 1 + N i ,

[0134] The number of the small ball on the upper left side of this ball is bid + N i ,

[0135] The number of the small ball on the lower right side of this ball is bid + 1 - N i ,

[0136] The number of the small ball on the lower left side of this ball is bid - N i .

[0137] It should be noted that Figure 5 in which N i = 100 is used for the legend illustration, but the value of N i is not limited to this.

[0138] (2) For the spherical particles in the odd-numbered layers, the numbering rule is as follows: Figure 6 When it is the first ball in the odd-numbered layer, if the number of this ball is denoted as bid, then

[0139] the number of the small ball on the right side of this ball is bid + 1,

[0140] the number of the small ball on the left side of this ball is bid - 1 + N

[0141] the number of the small ball on the upper right side of this ball is bid + N i ,

[0142] the number of the small ball on the upper left side of this ball is bid - 1 + N i ,

[0143] + N i + N i ,

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

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

[0146] (2) When it is the last ball in the odd-numbered layer, if the number of this ball is denoted as bid, then

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

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

[0149] the number of the small ball on the upper right side of this ball is bid + N i ,

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

[0154] The number of the small ball on the right side of the ball is bid + 1,

[0155] The number of the small ball on the left side of the ball is bid - 1,

[0156] The number of the small ball on the upper right side of the ball is bid + N i ,

[0157] The number of the small ball on the upper left side of the ball is bid - 1 + N i ,

[0158] The number of the small ball on the lower right side of the ball is bid - N i ,

[0159] The number of the small ball on the lower left side of the ball is bid - 1 - N i .

[0160] It should be noted that Figure 6 in the legend, N i = 100 is used for illustration, but the value of N i is not limited to this value.

[0161] II. When the spherical particles are symmetrically arranged, the numbering rule of the spherical particles is as follows;

[0162] When the spherical particles are symmetrically arranged, they are divided into head balls, ordinary 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 ordinary balls are the small balls between the head ball and the tail ball, and the numbers are N0 + 1 to 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 and odd layers are the same, such as Figure 7 shown, more specifically as follows:

[0163] (1) When it is the first ball in each layer, if the number of this ball is recorded as bid, then

[0164] the number of the small ball on the right side of this ball is bid + 1,

[0165] the number of the small ball on the left side of this ball is bid - 1 + N i ,

[0166] the number of the small ball directly above this ball is bid + N i ,

[0167] the number of the small ball directly below this ball is bid - N i .

[0168] (2) When it is the last ball in each layer, if the number of this ball is recorded as bid, then

[0169] the number of the small ball on the right side of this ball is bid + 1 - N i ,

[0170] the number of the small ball on the left side of this ball is bid - 1,

[0171] the number of the small ball directly above this ball is bid + N i ,

[0172] the number of the small ball directly below this ball is bid - N i .

[0173] (3) When it is an ordinary ball (the 2nd to the N i -1 ball) in each layer, if the number of this ball is recorded as bid, then

[0174] the number of the small ball on the right side of this ball is bid + 1,

[0175] the number of the small ball on the left side of this ball is bid - 1,

[0176] the number of the small ball directly above this ball is bid + N i ,

[0177] the number of the small ball directly below this ball is bid - N i .

[0178] It should be noted that Figure 7 in which N i= 100 is used for legend illustration, but the value of N i is not limited to this.

[0179] S22: Assign contact stiffness to each coarse aggregate particle in the first coarse aggregate aggregate using a linear model, and servo to a preset target void ratio;

[0180] Specifically, a linear contact bonding model can be used for simulation, and servo to a preset target void ratio under a given contact stiffness.

[0181] S3: Apply a preset radial load and a preset axial load to the three-dimensional discrete element model to obtain a mechanical response model;

[0182] Among them, when applying the radial load, the confining pressure on the spherical particles in the spherical particle layer near the middle is calculated 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;

[0183] Exemplarily, the interlock arrangement is as Figure 8 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 sphere BP_0. F = P*(S1 + S2 + S3 + S4 + S5 + S6), where P is the confining pressure value, and S1, S2, S3, S4, S5, S6 are the areas of the six equilateral triangles respectively.

[0184] Taking the area S1 triangle composed of the small spheres BP_0, BP_UR, and BP_R as an example, by extracting the center coordinates of the three small spheres, 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 sphere, extract them according to the number of each small sphere. The numbering rules of the small spheres refer to Figure 5 and Figure 6 .

[0185] The symmetric arrangement is as Figure 9 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 equivalent to the force applied to the target sphere BP_0. F = P*(S1 + S2 + S3 + S4), where P is the test confining pressure value, and S1, S2, S3, S4 are the areas of the four squares respectively.

[0186] Taking the square with an area of (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, and calculating S1 based on half of the cross product of the center vectors, the force value applied to S1 is further calculated. Among them, when extracting the center coordinates of each small ball, they are extracted according to the numbers of each small ball. The numbering rules of the small balls refer to Figure 7 。

[0187] 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. The simulation is carried out through the discrete element software PFC, and then the normal contact force, tangential contact force, normal vector, tangential vector, branch vector, normal branch vector, and tangential branch vector of each contact are extracted. It should be noted that the contacts here are different from the coarse aggregate particles. Each coarse aggregate particle may form multiple contacts under the action of multiple surrounding coarse aggregate particles.

[0188] S4: Construct 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;

[0189] Specifically, S5 includes:

[0190] S41: Calculate the stress tensor and fabric tensor according to the normal contact force, normal vector, tangential vector, and branch vector, and calculate the anisotropy coefficient according to the stress tensor and fabric tensor;

[0191] Among them, the stress tensor, fabric tensor, and anisotropy coefficient are calculated according to the following set of formulas:

[0192]

[0193] σ kl is the stress tensor of the second coarse aggregate aggregate, φ kl is the fabric tensor of the second coarse aggregate aggregate, is the second-order structure tensor of the second coarse aggregate aggregate, a c 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 the l direction respectively, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model.

[0194] 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 is the vector obtained by dividing the normal vector by its modulus, and the other unit vectors are calculated in the same way.

[0195] S42: Calculate the structure tensors of the normal contact force, tangential contact force, normal branch vector, and tangential branch vector;

[0196] Among them, the calculation method of the structure tensor of the normal contact force is as follows:

[0197]

[0198] 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, f i n 、 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, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0199] The calculation method of the structure tensor of the tangential contact force is as follows:

[0200]

[0201] Among them, is the structure tensor of the tangential contact force of the second coarse aggregate aggregate, f t c is the magnitude of the tangential contact force of the c-th contact, f i t 、 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 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, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0202] Among them, the calculation method of the structure tensor of the normal branch vector is as follows:

[0203]

[0204] 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, are the projected lengths of the unit normal branch vector of the c-th contact in the i and j directions respectively, are the projected lengths of the unit normal vector of the c-th contact in the k and l directions respectively, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0205] Among them, the calculation method of the structural tensor of the tangential branch vector is as follows:

[0206]

[0207] 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, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model.

[0208] 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 anisotropy degree of distribution in different directions;

[0209] Among them, the calculation method of the normal contact force fabric anisotropy coefficient is as follows:

[0210]

[0211] In the formula, a n 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, σ i ' j and σ' mn 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 magnitude of the average normal contact force of the second coarse aggregate aggregate, is the magnitude of the normal contact force for the c-th contact, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0212] Among them, the calculation method of the tangential contact force fabric anisotropy coefficient is as follows:

[0213]

[0214] In the formula, a t is the tangential contact force fabric anisotropy coefficient of the second coarse aggregate aggregate, S r2 is the standard value of the double dot product with σ i ' j ; sign() is the sign function. When S r2 > 0, sign(S r2 ) = 1; when S r2 < 0, sign(S r2 ) = -1; and are both the second-order structure tensors of the tangential contact force of the second coarse aggregate aggregate; σ i ' j and σ' mn are both the deviatoric tensors of the stress tensor of the second coarse aggregate aggregate; is the deviatoric tensor of the structure tensor of the tangential contact force of the second coarse aggregate aggregate, is the magnitude of the average tangential contact force of the second coarse aggregate aggregate, f t c is the magnitude of the tangential contact force for the c-th contact, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0215] Among them, the calculation method of the normal branch vector fabric anisotropy coefficient is as follows:

[0216]

[0217] In the formula, a dn is the normal branch vector fabric anisotropy coefficient of the second coarse aggregate aggregate, S r3 is the standard value of the double dot product with σ i ' j ; sign() is the sign function. When S r3 > 0, sign(S r3 ) = 1; when S r3 < 0, sign(S r3 ) = -1; and are all the second-order structure tensors of the normal branch vectors of the second coarse aggregate aggregate; σ i ' j and σ' mn are all the deviatoric tensors of the stress tensor of the second coarse aggregate aggregate, is the structure tensor of the normal branch vector of the deviatoric tensor, is the average length of the normal branch vector of the second coarse aggregate aggregate, is the length of the normal branch vector of the c-th contact, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model;

[0218] Among them, the calculation method of the tangential branch vector fabric anisotropy coefficient is as follows:

[0219]

[0220] In the formula, a dt is the tangential branch vector fabric anisotropy coefficient of the second coarse aggregate aggregate, S r4 is and σ i ' j the standard value of the double dot product; sign() is the sign function, when S r4 > 0, sign(S r4 ) = 1; when S r4 < 0, sign(S r4 ) = -1; and are all the second-order structure tensors of the tangential branch vectors of the second coarse aggregate aggregate; σ i ' j and σ' mn are all the deviatoric tensors of the stress tensor 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 vector of the second coarse aggregate aggregate, is the length of the tangential branch vector of the c-th contact, N c is the total number of contacts of the coarse aggregate particles in the mechanical response model.

[0221] S5: Construct the weighted fabric stress coefficient of the second coarse aggregate aggregate according to the fabric anisotropy coefficient;

[0222] Specifically, the weighted fabric anisotropy coefficient is calculated according to the following formula:

[0223] τ = 0.4(a c + a n + a dn + 1.5a dt + 1.5at );

[0224] In the formula, τ is the weighted fabric anisotropy coefficient of the second coarse aggregate aggregate, a c is the anisotropy coefficient of the second coarse aggregate aggregate, a n is the normal contact force fabric anisotropy coefficient of the second coarse aggregate aggregate, a dn is the normal branch vector fabric anisotropy coefficient of the second coarse aggregate aggregate, a dt is the tangential branch vector fabric anisotropy coefficient of the second coarse aggregate aggregate, a t is the tangential contact force fabric anisotropy coefficient of the second coarse aggregate aggregate.

[0225] S6: Determine the optimal gradation of each size of coarse aggregate according to the relationship between the weighted fabric stress coefficient of the second coarse aggregate aggregate and its axial strain under a preset axial load.

[0226] Specifically, take each coarse aggregate with different particle sizes, mix them according to different gradation ratios respectively, generate a three-dimensional discrete element model according to the steps of S1 to S5, change different radial loads and axial loads, and 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.

[0227] Exemplarily, in an embodiment of the present invention, the relationship between the weighted fabric anisotropy coefficient at 9.5 - 13.2 mm: 4.75 - 9.5 mm = 3:7, 4:6, 5:5, 6:4 under confining pressures of 0.2 MPa and 0.4 MPa is as Figure 10 , Figure 11 shown.

[0228] According to Figure 10 , Figure 11 , when 9.5 - 13.2 mm: 4.75 - 9.5 mm = 4:6, the mechanical properties of the coarse aggregate combination are the best, so the ratio of coarse aggregate 9.5 - 13.2 mm to 4.75 - 9.5 mm is determined to be 4:6.

[0229] Example 2

[0230] This embodiment provides an asphalt mixture design method, which includes the following steps:

[0231] S1: Design the gradation of coarse aggregate (particle size ≥ 4.75 mm) using the coarse aggregate design method described in Example 1, synthesize the coarse aggregate mixture according to this gradation, and calculate its compacted density and void ratio in the compacted state;

[0232] Specifically, mix two sizes of coarse aggregate, 9.5 - 13.2 mm and 4.75 - 9.5 mm, to obtain a coarse aggregate mixture, and measure its compacted density d sc= 1.644 cm 3 , void ratio V ca = 38%.

[0233] S2: Determine the gradation of fine aggregate.

[0234] Specifically, in the step of determining the gradation of each grade of fine aggregate in the fine aggregate mixture according to the filling rule, the gradation of each grade of fine aggregate in the fine aggregate mixture is determined according to the following set of formulas;

[0235]

[0236] w i = P i - P i-1

[0237]

[0238] Among them, w i is the weight percentage of the i-th grade of fine aggregate in the fine aggregate mixture except for the last grade of fine aggregate, d i+1 is the maximum nominal particle size of the (i + 1)-th grade of fine aggregate, D max is the maximum nominal particle size of the fine aggregate, w f is the weight percentage of the fine aggregate with the smallest particle size in the fine aggregate mixture, t is the total number of grades of fine aggregate in the fine aggregate mixture, n is a constant. When d i+1 > 0.075 mm, the value of n is 0.4 - 0.55 (take 0.45 in this embodiment). When d i+1 ≤ 0.075 mm, the value of n is 0.6 - 0.8 (take 0.7 in this embodiment); P i is the sieve passing rate of the i-th grade of fine aggregate, the aperture of this sieve is the maximum nominal particle size of the (i + 1)-th grade of fine aggregate, and the maximum nominal particle size of the (i + 1)-th grade of fine aggregate is smaller than the maximum nominal particle size of the i-th grade of fine aggregate.

[0239] Taking AC-13 as an example, since the fine aggregate with a particle size of 2.36 - 4.75 mm is the fine aggregate with the largest particle size, determine it as the 1st grade, and determine d1 = 2.36, D max = 4.75, n = 0.45, then P1 = 27%, w1 = P1 - P0 = 27%. Correspondingly, determine the fine aggregate with a particle size of 1.18 - 2.36 mm as the 2nd grade of fine aggregate, and determine d2 = 2.36, D max = 4.75, n = 0.45, then P2 = 46.6%, w2 = P2 - P1 = 19.6%. And so on, determine the fine aggregate with a particle size of 0.075 mm - 0.015 mm as the 6th grade of fine aggregate, and determine d6 = 0.075, D max= 4.75, n = 0.7, then P6 = 94.5%, w6 = P6 - P5 = 2%. The proportion w of the fine aggregate in the last stage f = 1 - 94.6% = 5.4%. Specifically, it is shown in Table 2 as follows.

[0240] Table 2 Proportions of Each Grade of Fine Aggregate

[0241]

[0242]

[0243] After determining the gradation of each grade of fine aggregate, synthesize them into a fine aggregate mixture and determine its apparent density d tf = 2.691 g / cm 3 .

[0244] S3: Determine the proportions of the coarse aggregate mixture and the fine aggregate mixture under the preset asphalt proportion and the preset mineral powder proportion;

[0245] Specifically, determine the proportions of the coarse aggregate mixture and the fine aggregate mixture in the mineral aggregate according to the following set of formulas:

[0246] q c + q f + q p = 100%

[0247]

[0248] where q c is the mass percentage of the coarse aggregate mixture in the mineral aggregate, q f is the mass percentage of the fine aggregate mixture in the mineral aggregate, q p is the mass percentage of the mineral powder in the mineral aggregate, q a is the mass percentage of the asphalt in the asphalt mixture, d sc is the compacted density of the coarse aggregate mixture, V ca is the void ratio of the coarse aggregate mixture, V vs is the designed void ratio of the asphalt mixture, d tf is the apparent density of the fine aggregate mixture, d tp is the apparent density of the mineral powder, d a is the density of the asphalt.

[0249] More specifically, in this embodiment, take the designed porosity V of the asphalt mixture vs as 4%, in the designed proportion q of the asphalt a = 4.4%, the asphalt density d a = 1.103 g / cm 3 , the designed proportion of the mineral powder is q p as 5%, the apparent density d of the mineral powdertp = 2.742 g / cm 3 In the case of, the proportion q of the coarse aggregate mixture in the mineral aggregate is calculated c = 71.08%, and the proportion q of the fine aggregate mixture in the mineral aggregate f = 23.92%.

[0250] Based on the above calculation results, the proportions of the coarse aggregate mixture, fine aggregate mixture, and mineral powder in the entire asphalt mixture are re-determined as follows:

[0251]

[0252] 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 an asphalt mixture, wherein the asphalt mixture comprises mineral material and asphalt, wherein the mineral material comprises a coarse aggregate mixture, a fine aggregate mixture and mineral powder; 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 multiple 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; Determine the optimal gradation of each coarse aggregate 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 mix the coarse aggregate mixture with the optimal grade; Determine the gradation of each grade of fine aggregate in the fine aggregate mixture according to the filling rule; According to the filling rule, the proportion of coarse aggregate mixture and fine aggregate mixture under the preset asphalt proportion and mineral aggregate proportion is determined.

2. The asphalt mixture design method according to claim 1, characterized in that: In the step of determining the gradation of each grade of fine aggregate in the fine aggregate mixture according to the filling rule, the gradation of each grade of fine aggregate in the fine aggregate mixture is determined according to the following formula group: w i =P i -P i-1 Among them, w i is the weight percentage of the i-th grade fine aggregate in the fine aggregate mixture except the last grade fine aggregate, d i+1 is the maximum nominal particle size of the i+1th grade fine aggregate, D max is the maximum nominal particle size of fine aggregate, w f is the weight percentage of the smallest size fine aggregate in the fine aggregate mixture, t is the total number of fine aggregates in the fine aggregate mixture, n is a constant, when d i+1 >0.075mm, the value of n is 0.4~0.

55. i+1 When ≤0.075mm, the value of n is 0.6~0.8; P i is the sieve pass rate of the i-th grade fine aggregate, the aperture of the sieve is the maximum nominal particle size of the i+1-th grade fine aggregate, and the maximum nominal particle size of the i+1-th grade fine aggregate is smaller than the maximum nominal particle size of the i-th grade fine aggregate.

3. The asphalt mixture design method according to claim 2, characterized in that: In the step of determining the ratio of the coarse aggregate mixture and the fine aggregate mixture under the preset asphalt ratio and the preset mineral powder ratio according to the filling rule, the ratio of the coarse aggregate mixture and the fine aggregate mixture in the mineral material is determined according to the following formula group: q c +q f +q p =100% Among them, q c is the mass percentage of coarse aggregate mixture in the ore, q f is the mass percentage of fine aggregate mixture in the ore, q p is the mass percentage of mineral powder in the ore, q a is the mass percentage of asphalt in asphalt mixture, d sc is the packed density of the coarse aggregate mixture, V ca is the void ratio of the coarse aggregate mixture, V vs is the design void ratio of asphalt mixture, d tf is the apparent density of the fine aggregate mixture, d tp is the apparent density of the mineral powder, d a is the density of asphalt.

4. The method for designing asphalt mixture according to claim 1, characterized in that: The step of constructing a stacking model of coarse aggregates with different gradation ratios includes: extracting 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; the flexible confining pressure wall includes multiple spherical particle layers 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: C i =H i / 2r i 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; 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 asphalt mixture design method 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 tangential vector, the branch 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: σ kl is the stress tensor of the second coarse aggregate, φ kl is the fabric tensor of the second coarse aggregate, is the second-order structure tensor of the second coarse aggregate, a c 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, N c is the total contact number of coarse aggregate particles in the mechanical response model.

6. The asphalt mixture design method 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, N c 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, N c 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, N c 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, N c is the total contact number of coarse aggregate particles in the mechanical response model.

7. The asphalt mixture design method 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, a n 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, σ i ' j and σ' mn 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 normal contact force of the cth contact, N c 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, a t is the structural anisotropy coefficient of the tangential contact force of the second coarse aggregate, S r2 for With σ i ' j The standard value of the double dot product; sign() is the sign function, when S r2 >0,sign(S r2 )=1; when S r2 <0,sign(S r2 )=-1; and are the second-order structural tensors of the tangential contact force of the second coarse aggregate; σ i ' j and σ' mn 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, N c 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, a dn is the normal branch vector structural anisotropy coefficient of the second coarse aggregate, S r3 for With σ i ' j The standard value of the double dot product; sign() is the sign function, when S r3 >0,sign(S r3 )=1; when S r3 <0,sign(S r3 )=-1; and are the second-order structure tensors of the normal branch vectors of the second coarse aggregate; σ i ' j and σ' mn 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, N c 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, a dt is the structural anisotropy coefficient of the tangential branch vector of the second coarse aggregate, S r4 for With σ i ' j The standard value of the double dot product; sign() is the sign function, when S r4 >0,sign(S r4 )=1; when S r4 <0,sign(S r4 )=-1; and are the second-order structure tensors of the tangential branch vectors of the second coarse aggregate; i ' j and σ' mn 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, N c is the total contact number of coarse aggregate particles in the mechanical response model.

8. The asphalt mixture design method according to claim 6, characterized in that: The weighted structural anisotropy coefficient is calculated according to the following formula: τ=0.4(a c +a n +a dn +1.5a dt +1.5a t ); Where, τ is the weighted structural anisotropy coefficient of the second coarse aggregate, a c is the anisotropy coefficient of the second coarse aggregate, a n is the normal contact force structural anisotropy coefficient of the second coarse aggregate, a dn is the normal branch vector structural anisotropy coefficient of the second coarse aggregate, a dt is the structural anisotropy coefficient of the tangential branch vector of the second coarse aggregate, a t 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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