Asphalt mixture design method, computer equipment and storage medium

Abstract

The invention discloses an asphalt mixture design method, computer equipment and a storage medium, and relates to the field of asphalt mixtures. Wherein the asphalt mixture comprises mineral aggregate and asphalt, and the mineral aggregate comprises a coarse aggregate mixture, a fine aggregate mixture and mineral powder; the design method comprises the following steps: constructing a three-dimensional discrete element model; applying a preset radial load and a preset axial load to obtain a mechanical response model; coarse aggregate particles in the mechanical response model form a plurality of contacts under the action of the radial load and the axial load, and the contact force and the vector of each contact are extracted; constructing a weighted fabric anisotropy coefficient; determining the optimal gradation of each grade of coarse aggregate according to the relationship between the weighted fabric anisotropy coefficient and the axial strain thereof under the preset load; determining the grading of each grade of fine aggregate in the fine aggregate mixture according to a filling rule; and determining the proportion of the coarse aggregate mixture and the fine aggregate mixture. According to the invention, the defect of poor correlation between a volume design method and pavement performance is overcome, and the designed gradation has excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to the field of asphalt mixture, and in particular to an asphalt mixture design method, computer equipment and storage medium. Background Art

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

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

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

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

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

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

[0008] In order to solve the technical problem of the present invention, the present invention provides an asphalt mixture design method, 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; the design method comprises:

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

[0010] The second rigid wall is replaced by a flexible confining pressure wall, and the 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;

[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 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;

[0012] 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;

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

[0014] 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;

[0015] Determine the gradation of each grade of fine aggregate in the fine aggregate mixture according to the filling rule;

[0016] 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.

[0017] As an improvement of the above technical solution, 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:

[0018]

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

[0020]

[0021] 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.

[0022] As an improvement of the above technical solution, in the step of determining the proportion 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 proportion of the coarse aggregate mixture and the fine aggregate mixture in the mineral material is determined according to the following formula group:

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

[0024]

[0025] 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, da is the density of asphalt.

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

[0027] Filling coarse aggregates of various grades with preset gradation ratios into a closed space formed by a first rigid wall and a second rigid wall to obtain a stacking model;

[0028] 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:

[0029] The second rigid wall is replaced by a flexible confining pressure wall;

[0030] 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;

[0031] 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;

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

[0033]

[0034] 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;

[0035] The number 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] 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.

[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 exerted 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, the tangential contact force, the normal vector, the branch vector, the tangential vector, the normal branch vector and the tangential branch vector includes 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;

[0040] Among them, the stress tensor, fabric tensor, and anisotropy coefficient are calculated according to the following formula group:

[0041]

[0042] 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.

[0043] As an improvement of the above technical solution, the step of constructing the structural anisotropy coefficient according to the normal contact force, the tangential contact force, the normal vector, the tangential vector, the branch vector, the normal branch vector and the tangential branch vector further comprises: 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;

[0044] Among them, the structural tensor of the normal contact force is calculated as follows:

[0045]

[0046] 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, f i n , 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 cis the total contact number of coarse aggregate particles in the mechanical response model;

[0047] The structural tensor for the tangential contact force is calculated as follows:

[0048]

[0049] in, is the structural tensor of the tangential contact force of the second coarse aggregate assembly, f t c is the magnitude of the tangential contact force of the cth contact, f i t , 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;

[0050] Among them, the calculation method of the structure tensor of the normal branch vector is as follows:

[0051]

[0052] 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;

[0053] Among them, the calculation method of the structure tensor of the tangent branch vector is as follows:

[0054]

[0055] 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.

[0056] As an improvement of the above technical solution, 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: the step of 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 that characterize the degree of anisotropy distributed in different directions;

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

[0058]

[0059] 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 assembly 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;

[0060] Among them, the calculation method of the tangential contact force component anisotropy coefficient is as follows:

[0061]

[0062] 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, f t c is the magnitude of the tangential contact force of the cth contact, N c is the total contact number of coarse aggregate particles in the mechanical response model;

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

[0064]

[0065] 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;

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

[0067]

[0068] In the formula, a dt is the structural anisotropy coefficient of the tangential branch vector of the second coarse aggregate, S r4 for With σi ' 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.

[0069] As an improvement of the above technical solution, the weighted structural 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] 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.

[0072] Correspondingly, the present invention also discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above-mentioned design method when executing the computer program.

[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 grading design method steps of the above method are implemented.

[0074] The implementation of the present invention has the following beneficial effects:

[0075] 1. The design method of asphalt mixture gradation of the present invention designs coarse aggregate and fine aggregate separately. The coarse aggregate is designed by theoretical simulation method, and the fine aggregate is designed by filling method. The division of labor is clear and the function is 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 coarse aggregate gradation in asphalt mixture of the present invention, three-dimensional discrete element model, three-dimensional flexible confining pressure, servo control, fabric tensor, structural tensor, and fabric anisotropy coefficient are combined to form a coarse aggregate gradation design process that is consistent with road performance and what you see is what you get. Specifically: the present invention adopts flexible confining pressure control, which can track the multiple mechanical properties of the coarse aggregate assembly within the effective deformation range and comprehensively evaluate the effectiveness of the designed gradation. The present invention adopts a theoretical method to effectively solve the shortcomings of the poor correlation between the volume design method and road performance, and the designed gradation has excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 is a three-dimensional schematic diagram of a 4.75-9.5 mm coarse aggregate scanned in Example 1 of the present invention;

[0078] Figure 2 is a three-dimensional schematic diagram of a 9.5-13.2 mm coarse aggregate scanned in Example 1 of the present invention;

[0079] Figure 3 is a schematic diagram of a confined space in Example 1 of the present invention;

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

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

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

[0083] Figure 7 Schematic diagram of the numbering rules of the head ball, the regular ball and the tail ball when the spherical particles are symmetrically arranged in Example 1 of the present invention;

[0084] Figure 8 Schematic diagram of the calculation rule of unit area when spherical particles are arranged in an interlocking manner in Example 1 of the present invention;

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

[0086] Fig.10 is a relationship diagram between the weighted structural stress coefficient and the axial strain under a confining pressure of 0.2 MPa in Example 1 of the present invention;

[0087] Fig.11 It is a relationship diagram between the weighted structural stress coefficient and the axial strain under the confining pressure of 0.4 MPa in Example 1 of the present invention. DETAILED DESCRIPTION

[0088] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with specific implementation methods.

[0089] Example 1

[0090] This embodiment provides a method for designing the gradation of a coarse aggregate mixture in an asphalt mixture, comprising:

[0091] S1: Construct the stacking model of coarse aggregate with different grading ratios;

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

[0093] Specifically, step S1 includes:

[0094] S11: Scanning coarse aggregates of different particle sizes in each batch using a 3D scanner to form an STL format file, and forming a template with the 3D scanning files of different particle sizes;

[0095] Specifically, in one embodiment, taking asphalt mixture AC-13 as an example, its coarse aggregate includes two grades of 4.75-9.5 mm and 9.5-13.2 mm, and the stl files after three-dimensional scanning are as follows: Figure 1 , Figure 2 shown.

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

[0097] S13: using clump distribute to sequentially read coarse aggregate particles of different particle sizes in the template, determine the generation volume of each level of coarse aggregate particles according to the preset gradation ratio, and calculate the number of coarse aggregate particles required to generate each level of coarse aggregate according to the volume of a single coarse aggregate particle; the generation order is to sequentially generate coarse aggregate particle models in order of particle size from large to small;

[0098] S14: randomly placing the generated coarse aggregate particle model into a predetermined area of ​​a preset closed space to obtain a stacking model;

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

[0100] S2: 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;

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

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

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

[0106]

[0107] Among them, r i is the radius of the spherical particles in the i-th spherical particle layer, R i is the radius of the first coarse aggregate in the accumulation model, N i is the number of spherical particles in the i-th spherical particle layer; specifically, for the convenience of calculation, the number of spherical particles in each spherical particle layer is set to 10 n , wherein n is a positive integer greater than or equal to 2. Further, the radii of all spherical particles in the flexible confining pressure wall are set to be the same.

[0108] The number 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] 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.

[0111] Specifically, the spherical particles in each spherical particle layer in the flexible confining pressure wall are numbered from large to small. For example, in one embodiment, if the number of spherical particles in each spherical particle layer is 100, the starting number of the spherical particles in the layer can be set to 100000, the last spherical particle is numbered 100099, and so on.

[0112] Furthermore, in order to facilitate the calculation of the confining pressure of each spherical particle after the radial load is applied later, it is also necessary to specify the numbering rules between adjacent layers. Specifically, the spherical particles of adjacent spherical particle layers are arranged in an interlocking arrangement or a symmetrical arrangement; when the spherical particles are arranged in an interlocking arrangement, six spherical particles are arranged around each spherical particle; when the spherical particles are arranged in a symmetrical arrangement, four spherical particles are arranged around each spherical particle (see Figure 5 to Figure 7 ). The following is a detailed description of the numbering rules between adjacent layers in each arrangement mode:

[0113] 1. When spherical particles are arranged in an interlocking manner, the numbering rules of spherical particles in even-numbered layers and odd-numbered layers are different;

[0114] When spherical particles are arranged in an interlaced manner, they are divided into head balls, regular balls, and tail balls. The head ball is the ball that starts numbering in each layer of balls. Its number N0 can be an integer, and N0 ≥ 10 n (n is a positive integer ≥ 3), such as 10000 or 100000; the tail ball is the ball at the end of each layer of balls, and its number is N e It can be an integer, and N e =N0+N i -1(N i is the total number of spherical particles in the i-th layer), exemplarily 10099 or 100099; the conventional balls are small balls between the head ball and the tail ball, numbered N0+1 to N e -1, illustratively, such as 10001-10098 or 100001-100098 (taking 100 spherical particles in each layer as an example, but not limited thereto); the numbering rules for even-numbered layers and odd-numbered layers are different. The details are as follows:

[0115] (I) Ginseng Figure 5 , the numbering rule for spherical particles in even layers is:

[0116] (1) When it is the first ball in an even layer, the ball is numbered as bid.

[0117] The number of the ball to the right of the ball is bid+1.

[0118] The number of the ball to the left of the ball is bid-1+N i ,

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

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

[0121] The number of the ball to the lower right of the ball is bid+1-N i ,

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

[0123] (2) When it is the last ball of an even-numbered layer, the ball is numbered bid.

[0124] The number of the ball to the right of the ball is bid+1-N i ,

[0125] The ball to the left of the ball is numbered bid-1.

[0126] The number of the ball on the upper right side of the ball is bid+1.

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

[0128] The number of the ball to the lower right of the ball is bid+1-N i -N i ,

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

[0130] (3) When it is an even-numbered layer of regular balls (the 2nd to Nth i -1 ball (the ordinary ball), record the ball number as bid, then

[0131] The number of the ball to the right of the ball is bid+1.

[0132] The ball to the left of the ball is numbered bid-1.

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

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

[0135] The number of the ball to the lower right of the ball is bid+1-N i ,

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

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

[0138] (II) Figure 6 , the numbering rule for odd-numbered layers of spherical particles is:

[0139] (1) When it is the first ball in an odd layer, the ball is numbered as bid.

[0140] The number of the ball to the right of the ball is bid+1.

[0141] The number of the ball to the left of the ball is bid-1+N i ,

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

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

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

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

[0146] (2) When it is the last ball of an odd-numbered layer, the ball is numbered as bid.

[0147] The number of the ball to the right of the ball is bid+1-N i ,

[0148] The ball to the left of the ball is numbered bid-1.

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

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

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

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

[0153] (3) When it is an odd-numbered layer of regular balls (the 2nd to Nth i -1 ball (the ordinary ball), record the ball number as bid, then

[0154] The number of the ball to the right of the ball is bid+1.

[0155] The ball to the left of the ball is numbered bid-1.

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

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

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

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

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

[0161] 2. When the spherical particles are arranged symmetrically, the numbering rule of the spherical particles is:

[0162] When the spherical particles are arranged symmetrically, they are divided into head balls, regular balls, and tail balls. The head ball is the ball that starts numbering in each layer of balls. Its number N0 can be an integer, and N0 ≥ 10 n (n is a positive integer ≥ 3), such as 10000 or 100000; the tail ball is the ball at the end of each layer of balls, and its number is N e It can be an integer, and N e =N0+N i -1(N i is the total number of spherical particles in the i-th layer), exemplarily 10099 or 100099; the conventional balls are small balls between the head ball and the tail ball, numbered N0+1 to N e-1, illustratively, 10001-100098 or 100001-100098 (taking 100 spherical particles in each layer as an example, but not limited thereto); the numbering rules of even-numbered layers and odd-numbered layers are consistent, such as Figure 7 As shown, more specific as follows:

[0163] (1) When it is the first ball of each layer, the ball number is bid, then

[0164] The number of the ball to the right of the ball is bid+1.

[0165] The number of the ball to the left of the ball is bid-1+N i ,

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

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

[0168] (2) When it is the last ball of each layer, the ball number is bid.

[0169] The number of the ball to the right of the ball is bid+1-N i ,

[0170] The ball to the left of the ball is numbered bid-1.

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

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

[0173] (3) When the regular balls in each layer (the 2nd to the Nth i -1 ball (the ordinary ball), let the ball be numbered bid, then

[0174] The number of the ball to the right of the ball is bid+1.

[0175] The ball to the left of the ball is numbered bid-1.

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

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

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

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

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

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

[0182] When a radial load is applied, the confining pressure exerted on the spherical particles in the spherical particle layer near the middle is calculated according to the area equivalence principle. Specifically, the center coordinates of each spherical particle are extracted according to the number of each spherical particle, the center vector of each spherical particle is calculated, and the preset area is calculated according to the center vector, and then the confining pressure exerted on each spherical particle is calculated;

[0183] Exemplarily, the nested arrangement is as follows Figure 8 As shown, the regular hexagon is the calculation unit area, and the regular hexagon is composed of six equilateral triangles. The force applied to the area of ​​the regular hexagon is equivalent to the force applied to the target ball BP_0, F=P*(S1+S2+S3+S4+S5+S6), where P is the confining pressure value, and S1, S2, S3, S4, S5, and S6 are the areas of six equilateral triangles respectively.

[0184] Taking the triangle S1 composed of balls BP_0, BP_UR, and BP_R as an example, the center coordinates of the three balls are extracted, the center vector is calculated, S1 is calculated based on the cross product of the center vectors, and then the force applied to S1 is calculated. When extracting the center coordinates of each ball, the extraction is performed according to the number of each ball. The numbering rules of the balls refer to Figure 5 and Figure 6 .

[0185] Symmetrical arrangement Fig. 9 As shown, the square is the calculation unit area, and the square is composed of four small squares. The force applied to the square area is equivalent to being applied to the target ball BP_0, F=P*(S1+S2+S3+S4), where P is the test confining pressure value, and S1, S2, S3, and S4 are the areas of the four squares respectively.

[0186] Take the square of (S1+S2+S3+S4) enclosed by the balls BP_R, BP_L, BP_U, and BP_D as an example. By extracting the center coordinates of the three balls BP_0, BP_L, and BP_U, the center vector is calculated. S1 is calculated based on half of the cross product of the center vector, and then the force applied to S1 is calculated. When extracting the center coordinates of each ball, the extraction is performed according to the number of each ball. The numbering rules of the balls refer to Figure 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, and the discrete element software PFC is used for simulation, 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 contact here is different from the coarse aggregate particles, and each coarse aggregate particle may form multiple contacts under the action of multiple coarse aggregate particles around it.

[0188] S4: construct the structural anisotropy coefficient based on 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 the fabric tensor according to the normal contact force, the normal vector, the tangential vector and the branch vector, and calculate the anisotropy coefficient according to the stress tensor and the fabric tensor;

[0191] Among them, the stress tensor, fabric tensor, and anisotropy coefficient are calculated according to the following formula group:

[0192]

[0193] 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.

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

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

[0196] Among them, the structural tensor of the normal contact force is calculated as follows:

[0197]

[0198] 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, f i n , 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;

[0199] The structural tensor for the tangential contact force is calculated as follows:

[0200]

[0201] in, is the structural tensor of the tangential contact force of the second coarse aggregate assembly, f t c is the magnitude of the tangential contact force of the cth contact, f i t , 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;

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

[0203]

[0204] 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;

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

[0206]

[0207] 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.

[0208] S43: calculating the normal contact force configuration anisotropy coefficient, the tangential contact force configuration anisotropy coefficient, the normal branch vector configuration anisotropy coefficient and the tangential branch vector configuration anisotropy coefficient, which characterize the degree of anisotropy distributed in different directions;

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

[0210]

[0211] 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;

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

[0213]

[0214] 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, f t c is the magnitude of the tangential contact force of the cth contact, N c is the total contact number of coarse aggregate particles in the mechanical response model;

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

[0216]

[0217] 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;

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

[0219]

[0220] 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.

[0221] S5: constructing a weighted structural stress coefficient of the second coarse aggregate according to the structural anisotropy coefficient;

[0222] Specifically, the weighted structural 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] 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.

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

[0226] Specifically, coarse aggregates of different particle sizes are taken respectively, and after being mixed according to different grading ratios, a three-dimensional discrete element model is generated according to steps S1 to S5, different radial loads and axial loads are changed, the microscopic mechanical properties of the coarse aggregate assembly under different grading ratios are compared and analyzed, and the gradation with the best road performance is selected.

[0227] For example, in one embodiment of the present invention, the relationship between the weighted structural anisotropy coefficients at 9.5-13.2 mm: 4.75-9.5 mm = 3:7, 4:6, 5:5, 6:4 under a confining pressure of 0.2 MPa and 0.4 MPa is as follows: Fig.10 , Fig.11 shown.

[0228] according to Fig.10 , Fig.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 and 4.75~9.5mm 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: The gradation of coarse aggregate (particle size ≥ 4.75 mm) is designed using the design method of coarse aggregate described in Example 1, and a coarse aggregate mixture is prepared according to the gradation, and its packing density and void ratio in a packed state are calculated;

[0232] Specifically, two grades of coarse aggregates, 9.5-13.2 mm and 4.75-9.5 mm, were mixed to obtain a coarse aggregate mixture, and its packed density d was measured. sc=1.644cm 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 formula group;

[0235]

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

[0237]

[0238] 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 (0.45 in this embodiment), when d i+1 When ≤0.075mm, the value of n is 0.6-0.8 (0.7 in this embodiment); 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.

[0239] Taking AC-13 as an example, since the fine aggregate with a particle size of 2.36 to 4.75 mm is the largest fine aggregate, it is determined to be the first grade, and d1 = 2.36, D max =4.75, n=0.45, then P1=27%, w1=P1-P0=27%. Accordingly, the fine aggregate of 1.18-2.36 mm is determined as the second grade fine aggregate, and d2=2.36, D max =4.75, n=0.45, then P2=46.6%, w2=P2-P1=19.6%. By analogy, the fine aggregate of 0.075mm~0.015mm is determined as the sixth grade fine aggregate, and d6=0.075, D max=4.75, n = 0.7, then P6 = 94.5%, w6 = P6-P5 = 2%. The proportion of the last fine aggregate w f =1-94.6%=5.4%. The details are shown in Table 2.

[0240] Table 2 Proportion of each grade of fine aggregate

[0241]

[0242]

[0243] After determining the gradation of each grade of fine aggregate, they are synthesized into a fine aggregate mixture and their apparent density d is determined. tf =2.691g / cm 3 .

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

[0245] Specifically, the proportion of coarse aggregate mixture and fine aggregate mixture in the mineral material is determined according to the following formula group:

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

[0247]

[0248] 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.

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

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

[0251]

[0252] The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A method for designing 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 an 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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