Asphalt mixture coarse aggregate contact network characterization method and system

Abstract

The invention belongs to the technical field of road engineering, and discloses an asphalt mixture coarse aggregate contact network characterization method and system.The method comprises the steps that PFC 3D is adopted to establish an asphalt mixture three-dimensional dynamic compaction model, and the compaction process is simulated; counting the number of contact points among the coarse aggregates by adopting a virtual compaction model; collecting the size and direction of the contact force between the coarse aggregates, and calculating the included angle between the contact force and the loading direction and the component of the contact force along the loading direction; calculating physical contact parameters of the contact points among the coarse aggregates, wherein the physical contact parameters comprise the relative stable length, the relative stable area and the relative stable volume of the contact points; and establishing an asphalt mixture coarse aggregate contact network bearing capacity index calculation model, and realizing asphalt mixture coarse aggregate contact network characterization. The invention creatively provides an asphalt mixture coarse aggregate contact network characterization method based on discrete element simulation, so that an asphalt mixture contact network stability evaluation model is established, and various characteristics of the asphalt mixture coarse aggregate can be analyzed and evaluated.

Description

Technical Field

[0001] The invention belongs to the technical field of road engineering, and in particular relates to a method and system for characterizing a contact network of coarse aggregate in an asphalt mixture. Background Art

[0002] Asphalt mixture is a multi-level multi-phase granular material composed of mineral materials, asphalt and voids, with typical dissipative structural characteristics. During the compaction process, aggregate particles migrate under the action of compaction work, their spatial positions are rearranged, and the contact state between coarse aggregates is constantly changing. As compaction proceeds, aggregate particles interlock and rub against each other, gradually forming a contact network and eventually reaching a balanced and stable state. Therefore, the interlocking and friction characteristics of coarse aggregates and the stability of the contact network greatly affect the skeleton characteristics and compaction effect of asphalt mixtures, and thus affect the performance of asphalt pavement.

[0003] In order to further explore the contact network between coarse aggregates in asphalt mixtures, domestic and foreign scholars have conducted extensive research on the evolution and stability characterization methods of the contact network between coarse aggregates using indoor mechanical properties tests, X-ray industrial CT scanning, digital image processing and other methods. However, due to the large number of contact points between coarse aggregates in asphalt mixtures and different contact states, it is difficult to accurately measure the contact parameters of different contact points using conventional evaluation methods, and there is no effective evaluation method for the stability of the contact network between coarse aggregates in asphalt mixtures.

[0004] Based on this, the present invention creatively proposes a method for characterizing the coarse aggregate contact network of asphalt mixture based on discrete element simulation, thereby establishing an asphalt mixture contact network stability evaluation model.

[0005] Through the above analysis, the problems and defects of the existing technology are: there are a large number of contact points between coarse aggregates in asphalt mixtures and the contact states are different. Conventional test methods and digital image processing technology are difficult to accurately measure the contact parameters of different contact points. There is no effective evaluation method for the stability of the contact network between coarse aggregates in asphalt mixtures.

[0006] The compaction of asphalt mixture is a dynamic process. Under the action of compaction work, the contact points are frequently reorganized, and the size and direction of the contact force also change accordingly. Conventional test methods are difficult to measure the contact parameters of each contact point inside the asphalt mixture and the stability of the coarse aggregate contact network. Although the method combining X-ray and digital image processing can explore the contact state of asphalt mixture aggregates at a given compaction stage from a microscopic level, it is difficult to reflect the stability of the coarse aggregate contact network at any stage during the compaction process in real time. Summary of the invention

[0007] In order to overcome the problems existing in the related art, the embodiments disclosed in the present invention provide a method and system for characterizing the contact network of coarse aggregate in asphalt mixture, and in particular, a method and system for characterizing the contact network of coarse aggregate in asphalt mixture based on discrete element simulation, and the technical scheme is as follows:

[0008] The present invention is achieved by a method for characterizing the contact network of coarse aggregate of asphalt mixture, comprising the steps of:

[0009] S1, using PFC 3D to establish a three-dimensional dynamic compaction model of asphalt mixture to simulate the compaction process;

[0010] S2, using the three-dimensional dynamic compaction model of asphalt mixture, the number of contact points between coarse aggregates is counted;

[0011] S3, collect the magnitude and direction of the contact force between coarse aggregates, calculate the angle between the contact force and the loading direction, and the component of the contact force along the loading direction;

[0012] S4, calculate the physical contact parameters of the contact points between coarse aggregates, including the relative stable length, relative stable area and relative stable volume of the contact points;

[0013] S5. Establish a calculation model for the bearing capacity index of the coarse aggregate contact network of asphalt mixture.

[0014] In step S1, a three-dimensional dynamic compaction model of asphalt mixture is established using PFC 3D, including:

[0015] Using discrete element numerical simulation technology, PFC 3D software was used to establish virtual coarse aggregate and asphalt mortar;

[0016] Contact models are set up between asphalt mortars, between coarse aggregates, and between asphalt mortar and aggregates to generate virtual asphalt mixture specimens.

[0017] Furthermore, the three-dimensional dynamic compaction model of asphalt mixture refers to a rotational compaction model;

[0018] Walls are set at the top and bottom of the specimen, and compaction parameters are set. A virtual compaction specimen is formed by applying pressure to the top wall.

[0019] Furthermore, the compaction parameters are: vertical pressure 600 Kpa, internal rotation angle 1.15°, rotation rate 30 r / min, and designed compaction times 100.

[0020] In step S2, the number of contact points between coarse aggregates refers to the number of contact points between any coarse aggregates within the particle size range of 4.75 mm to the nominal maximum particle size.

[0021] In step S3, the loading direction refers to the direction of pressure applied to the top wall, and the expression is:

[0022] F ci =F i ·cos〈min{a,b}〉

[0023] In the formula, F i is the contact force at the contact point between coarse aggregates, a is the angle between the positive contact force and the loading direction, and b is the angle between the negative contact force and the loading direction.

[0024] In step S3, calculating the angle between the contact force and the loading direction refers to calculating the acute angle between the contact force and the loading direction.

[0025] In step S4, the relative stable length of the contact point is calculated as:

[0026]

[0027] In the formula, R L is the relative contact length of any two contacting coarse aggregates, L is the height of the virtual specimen;

[0028] The relative stable area is calculated as:

[0029]

[0030] In the formula, R S is the relative contact area between any two contacting coarse aggregates, R SS is the interstitial area of ​​coarse aggregate;

[0031] The relative stable volume is calculated as:

[0032]

[0033] In the formula, R V is the relative contact volume of any two contacting coarse aggregates, and V is the volume of the virtual specimen.

[0034] In step S5, the calculation model of the asphalt mixture coarse aggregate contact network bearing capacity index is:

[0035]

[0036] Where NMAS is the nominal maximum particle size of the virtual asphalt mixture, i is the particle size classification of the coarse aggregate, i = 4.75, 9.5, 13.2, 16, 19, 26.5, 31.5.

[0037] Another object of the present invention is to provide a coarse aggregate contact network characterization system for asphalt mixture, which is used to control the coarse aggregate contact network characterization method for asphalt mixture, and the system comprises:

[0038] The compaction process simulation module is used to establish a three-dimensional dynamic compaction model of asphalt mixture using PFC 3D to realize compaction process simulation;

[0039] The module for counting the number of contact points between coarse aggregates is used to count the number of contact points between coarse aggregates using a three-dimensional dynamic compaction model of asphalt mixtures;

[0040] The module for calculating the contact force between coarse aggregates is used to collect the magnitude and direction of the contact force between coarse aggregates, calculate the angle between the contact force and the loading direction, and the component of the contact force along the loading direction;

[0041] The physical contact parameter calculation module is used to calculate the physical contact parameters of the contact points between coarse aggregates, including the relative stable length, relative stable area and relative stable volume of the contact points;

[0042] The coarse aggregate contact network characterization module is used to establish a calculation model for the bearing capacity index of the coarse aggregate contact network of asphalt mixture and realize the characterization of the coarse aggregate contact network of asphalt mixture.

[0043] Combining all the above technical solutions, the advantages and positive effects of the present invention are as follows:

[0044] The present invention proposes a characterization method for the contact network of coarse aggregate in asphalt mixture based on discrete element simulation. A three-dimensional dynamic compaction model of asphalt mixture is established by PFC 3D software, the compaction process is simulated, the number of contact points between coarse aggregates is counted, the contact force parameters and physical contact parameters are calculated, and finally a bearing capacity index calculation model based on the coarse aggregate contact network is established, which is used to analyze and evaluate the various characteristics of coarse aggregate in asphalt mixture.

[0045] Based on the discrete element simulation method, the present invention constructs a contact network characterization model for coarse aggregates in asphalt mixtures. Through dynamic compaction simulation, the number of contact points, contact force and its direction and other parameters are accurately analyzed, and the characteristic changes of the contact network in the dynamic process are provided. The present invention overcomes the limitation that traditional experimental methods are difficult to obtain the dynamic parameters of contact points in real time, and effectively solves the characterization problem caused by the complex and changeable compaction process. It is helpful to promote the real-time evaluation of the compaction effect of asphalt mixtures, improve the level of mechanical performance analysis of asphalt pavements, and promote the research and development and promotion of high-performance pavements.

[0046] By quantifying the dynamic characteristics of the coarse aggregate contact network, the present invention can significantly improve the design accuracy and service performance prediction capability of asphalt pavement, and provide scientific guidance for road construction and maintenance. It helps to optimize the construction process, reduce maintenance and repair costs, and provide basic technical support for intelligent road construction. This technical solution can be widely used in road construction companies, asphalt mixture manufacturers and scientific research institutes. It is expected to effectively promote the construction of smart highways, fill the market gap in dynamic contact network research, and bring considerable economic benefits to enterprises.

[0047] At present, the characterization of the coarse aggregate contact network of asphalt mixture at home and abroad mainly relies on indoor mechanical tests, X-ray scanning and digital image processing technologies, but these methods are difficult to achieve dynamic full-factor analysis of the compaction process. The present invention is based on discrete element simulation, which can not only realize the real-time dynamic characterization of the coarse aggregate contact state during the compaction process, but also comprehensively evaluate the stability parameters of the contact points, filling the technical gap of existing research that is difficult to quantify the dynamic characteristics of the contact network, and providing new research ideas and methods for the field of road engineering.

[0048] The present invention solves the problem of dynamic characterization of coarse aggregate contact network that has long plagued the field of road engineering. Traditional methods cannot comprehensively and accurately analyze the dynamic changes of contact points during the compaction of asphalt mixtures. The present invention uses discrete element simulation technology to achieve accurate measurement of contact point parameters throughout the compaction process for the first time, and establishes a contact network stability evaluation model. This technology provides important support for accurately evaluating the compaction effect of asphalt mixtures and the service performance of pavement, and meets the industry's long-standing urgent need for refined research in this field.

[0049] The present invention effectively overcomes the technical prejudice in the industry against the limitations of traditional characterization methods, which is that the contact network characterization in dynamic processes cannot be accurately achieved. Through the innovative application of discrete element simulation, the present invention overturns the traditional concept of relying solely on static test methods and verifies the feasibility and scientificity of dynamic simulation in contact network research. This technological breakthrough sets a new standard for the refined research in related fields of road engineering in the future and promotes the widespread acceptance and application of dynamic contact network research methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the description, serve to explain the principles of the present disclosure;

[0051] Figure 1 is a flow chart of a method for characterizing a coarse aggregate contact network of an asphalt mixture provided by an embodiment of the present invention;

[0052] Figure 2 It is a schematic diagram of a virtual specimen of AC-20 median asphalt mixture provided in Example 2 of the present invention. DETAILED DESCRIPTION

[0053] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific implementation disclosed below.

[0054] The innovation of the present invention is that the discrete element method is used to construct a three-dimensional dynamic compaction model to accurately simulate the particle migration and contact state changes during the compaction process of asphalt mixtures, thus overcoming the limitations of traditional static characterization. By dynamically collecting and quantifying all-factor parameters such as the number of coarse aggregate contact points, the size and direction of contact force, stable length, area, volume, etc., a contact network bearing capacity index model is constructed to comprehensively evaluate the stability of the contact network. In addition, this method realizes the characterization of the entire compaction process and all stages, breaking through the technical bottleneck that conventional experiments cannot capture dynamic changes in real time, and provides new ideas for the accurate analysis of the mechanical properties of asphalt mixtures and the service behavior of pavements.

[0055] Embodiment 1, as Figure 1 As shown, the method for characterizing the contact network of coarse aggregate in asphalt mixture provided by the embodiment of the present invention comprises the following steps:

[0056] S1, using PFC 3D to establish a three-dimensional dynamic compaction model of asphalt mixture to simulate the compaction process;

[0057] Among them, the use of PFC 3D to establish a three-dimensional dynamic compaction model of asphalt mixture refers to the use of discrete element numerical simulation technology and PFC 3D software to establish virtual coarse aggregate and asphalt mortar, and set up contact models between asphalt mortar, between coarse aggregates, and between asphalt mortar and aggregates to generate virtual asphalt mixture specimens.

[0058] Asphalt mixture compaction model refers to the rotational compaction model. Walls are set at the top and bottom of the specimen, and reasonable compaction parameters are set to form a virtual compaction specimen by applying pressure to the top wall.

[0059] The compaction parameters are: vertical pressure 600Kpa, internal rotation angle 1.15°, rotation rate 30r / min, and designed compaction times 100.

[0060] S2, using the three-dimensional dynamic compaction model of asphalt mixture, the number of contact points between coarse aggregates is counted;

[0061] The number of contact points between coarse aggregates refers to the number of contact points between any coarse aggregates within the particle size range of 4.75 mm to the nominal maximum particle size. The contact points are divided according to the particle sizes of the two contacting coarse aggregates, as shown in Table 1.

[0062] Table 1 Contact point division results

[0063]

[0064]

[0065] S3, collect the magnitude and direction of the contact force between coarse aggregates, calculate the angle between the contact force and the loading direction, and the component of the contact force along the loading direction.

[0066] The loading direction refers to the direction of pressure applied to the top wall.

[0067] F ci =F i ·cos <min{a,b}〉

[0068] In the formula, F i is the contact force at the contact point between coarse aggregates, a is the angle between the positive contact force and the loading direction, and b is the angle between the negative contact force and the loading direction.

[0069] The contact force between the two aggregates involves the action force F1 and the reaction force F2; because the internal rotation angle is set during the rotary compaction process, the force F3 exerted by the top wall of the specimen on the specimen is not vertically downward. At this time, there is an angle a between F3 and F1, and an angle b between F3 and F2. The smaller acute angle can be selected between a and b. If a=b, select one of them.

[0070] S4, calculate the physical contact parameters of the contact points between coarse aggregates, including the relative stable length, relative stable area and relative stable volume of the contact points;

[0071] The calculation method of the relative stable length of the contact point is:

[0072]

[0073] In the formula, R L is the relative contact length of any two contacting coarse aggregates, L is the height of the virtual specimen;

[0074] The relative stable area is calculated as:

[0075]

[0076] In the formula, R S is the relative contact area between any two contacting coarse aggregates, R SS is the interstitial area of ​​coarse aggregate;

[0077] The relative stable volume is calculated as:

[0078]

[0079] In the formula, R V is the relative contact volume of any two contacting coarse aggregates, and V is the volume of the virtual specimen.

[0080] S5, establish a calculation model for the bearing capacity index of the coarse aggregate contact network of asphalt mixture;

[0081] Among them, the bearing capacity index calculation model is:

[0082]

[0083] Where NMAS is the nominal maximum particle size of the virtual asphalt mixture, i is the particle size classification of the coarse aggregate, i = 4.75, 9.5, 13.2, 16, 19, 26.5, 31.5.

[0084] Embodiment 2, the method for characterizing the contact network of coarse aggregate in asphalt mixture based on discrete element simulation provided by the embodiment of the present invention specifically comprises the following steps:

[0085] Step 1: Use PFC 3D to establish a three-dimensional dynamic rotary compaction model of AC-20 median asphalt mixture to simulate the compaction process, such as Figure 2 The passing rate of AC-20 median gradation is shown in Table 2.

[0086] Table 2 AC-20 median gradation pass rate

[0087]

[0088] In this model, virtual coarse aggregate and asphalt mortar are accurately simulated, and contact models are set between asphalt mortar, between coarse aggregate, and between asphalt mortar and aggregate to ensure the accuracy of the generated virtual asphalt mixture specimen. Then, the rotational compaction model is used for simulation. The model sets walls at the top and bottom of the specimen and applies pressure to the top wall according to the compaction parameters of set vertical pressure of 600Kpa, internal rotation angle of 1.15°, and rotation rate of 30r / min to simulate the actual compaction process. Finally, the virtual compaction specimen is formed by executing 100 designed compaction times, thereby realizing a detailed simulation of the entire compaction process.

[0089] Step 2: Using the established virtual compaction model, count the number of contact points between any coarse aggregates with a particle size range of 4.75 mm to 19 mm.

[0090] Step 3: Collect the magnitude and direction of the contact force between the coarse aggregates, and calculate the acute angle of the vertical downward pressure direction exerted by the coarse aggregate on the top wall and the contact force component in the pressure direction.

[0091] Step 4: Calculate the relative stable length, relative stable area, and relative stable volume of the contact points between coarse aggregates.

[0092] The calculation method of the relative stable length of the contact point is:

[0093]

[0094] In the formula, RL is the relative contact length of any two contacting coarse aggregates, L is the height of the virtual specimen;

[0095] The relative stable area is calculated as:

[0096]

[0097] In the formula, R S is the relative contact area between any two contacting coarse aggregates, R SS is the interstitial area of ​​coarse aggregate;

[0098] The relative stable volume is calculated as:

[0099]

[0100] In the formula, R V is the relative contact volume of any two contacting coarse aggregates, and V is the volume of the virtual specimen.

[0101] Step 5: Calculate the contact network bearing capacity index of coarse aggregate in asphalt mixture.

[0102]

[0103] Where NMAS is the nominal maximum particle size of the virtual asphalt mixture, i is the particle size classification of the coarse aggregate, i = 4.75, 9.5, 13.2, 16, 19, 26.5, 31.5.

[0104] After calculation, the coarse aggregate contact network bearing capacity index of AC-20 median asphalt mixture is 0.13307723.

[0105] Embodiment 3, the method for characterizing the contact network of coarse aggregate in asphalt mixture based on discrete element simulation provided by the embodiment of the present invention specifically comprises the following steps:

[0106] Step 1: Use PFC 3D to establish a three-dimensional dynamic rotary compaction model of AC-20 median asphalt mixture to simulate the compaction process. The pass rate of the upper limit gradation of AC-13 is shown in Table 3.

[0107] Table 3 AC-13 upper limit gradation pass rate

[0108]

[0109] In this model, virtual coarse aggregate and asphalt mortar are accurately simulated, and contact models are set between asphalt mortar, between coarse aggregate, and between asphalt mortar and aggregate to ensure the accuracy of the generated virtual asphalt mixture specimen. Then, the rotational compaction model is used for simulation. The model sets walls at the top and bottom of the specimen and applies pressure to the top wall according to the compaction parameters of set vertical pressure of 600Kpa, internal rotation angle of 1.15°, and rotation rate of 30r / min to simulate the actual compaction process. Finally, the virtual compaction specimen is formed by executing 100 designed compaction times, thereby realizing a detailed simulation of the entire compaction process.

[0110] Step 2: Using the established virtual compaction model, count the number of contact points between any coarse aggregates with a particle size range of 4.75 mm to 9.5 mm.

[0111] Step 3: Collect the magnitude and direction of the contact force between the coarse aggregates, and calculate the acute angle of the vertical downward pressure direction exerted by the coarse aggregate on the top wall and the contact force component in the pressure direction.

[0112] Step 4: Calculate the relative stable length, relative stable area, and relative stable volume of the contact points between coarse aggregates.

[0113] The calculation method of the relative stable length of the contact point is:

[0114]

[0115] In the formula, R L is the relative contact length of any two contacting coarse aggregates, L is the height of the virtual specimen;

[0116] The relative stable area is calculated as:

[0117]

[0118] In the formula, R S is the relative contact area between any two contacting coarse aggregates, R SS is the interstitial area of ​​coarse aggregate;

[0119] The relative stable volume is calculated as:

[0120]

[0121] In the formula, R V is the relative contact volume of any two contacting coarse aggregates, and V is the volume of the virtual specimen.

[0122] Step 5: Calculate the contact network bearing capacity index of coarse aggregate in asphalt mixture.

[0123]

[0124] Where NMAS is the nominal maximum particle size of the virtual asphalt mixture, i is the particle size classification of the coarse aggregate, i = 4.75, 9.5, 13.2, 16, 19, 26.5, 31.5.

[0125] After calculation, the coarse aggregate contact network bearing capacity index of AC-13 upper limit asphalt mixture is 0.00081.

[0126] Embodiment 4, the method for characterizing the contact network of coarse aggregate in asphalt mixture based on discrete element simulation provided by the embodiment of the present invention specifically comprises the following steps:

[0127] Step 1: Use PFC 3D to establish a three-dimensional dynamic rotary compaction model of AC-13 lower limit asphalt mixture to simulate the compaction process. The pass rate of AC-13 lower limit gradation is shown in Table 4.

[0128] Table 4 AC-13 lower limit gradation pass rate

[0129]

[0130] In this model, virtual coarse aggregate and asphalt mortar are accurately simulated, and contact models are set between asphalt mortar, between coarse aggregate, and between asphalt mortar and aggregate to ensure the accuracy of the generated virtual asphalt mixture specimen. Then, the rotational compaction model is used for simulation. The model sets walls at the top and bottom of the specimen and applies pressure to the top wall according to the compaction parameters of set vertical pressure of 600Kpa, internal rotation angle of 1.15°, and rotation rate of 30r / min to simulate the actual compaction process. Finally, the virtual compaction specimen is formed by executing 100 designed compaction times, thereby realizing a detailed simulation of the entire compaction process.

[0131] Step 2: Using the established virtual compaction model, count the number of contact points between any coarse aggregates within the particle size range of 4.75 mm to 13.2 mm.

[0132] Step 3: Collect the magnitude and direction of the contact force between the coarse aggregates, and calculate the acute angle of the vertical downward pressure direction exerted by the coarse aggregate on the top wall and the contact force component in the pressure direction.

[0133] Step 4: Calculate the relative stable length, relative stable area, and relative stable volume of the contact points between coarse aggregates.

[0134] The calculation method of the relative stable length of the contact point is:

[0135]

[0136] In the formula, R Lis the relative contact length of any two contacting coarse aggregates, L is the height of the virtual specimen;

[0137] The relative stable area is calculated as:

[0138]

[0139] In the formula, R S is the relative contact area between any two contacting coarse aggregates, R SS is the interstitial area of ​​coarse aggregate;

[0140] The relative stable volume is calculated as:

[0141]

[0142] In the formula, R V is the relative contact volume of any two contacting coarse aggregates, and V is the volume of the virtual specimen.

[0143] Step 5: Calculate the contact network bearing capacity index of coarse aggregate in asphalt mixture.

[0144]

[0145] Where NMAS is the nominal maximum particle size of the virtual asphalt mixture, i is the particle size classification of the coarse aggregate, i = 4.75, 9.5, 13.2, 16, 19, 26.5, 31.5.

[0146] After calculation, the coarse aggregate contact network bearing capacity index of AC-13 lower limit asphalt mixture is 0.08267.

[0147] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for characterizing the contact network of coarse aggregate in asphalt mixture, characterized in that: The method comprises the steps of: S1, using PFC 3D to establish a three-dimensional dynamic compaction model of asphalt mixture to simulate the compaction process; S2, using the three-dimensional dynamic compaction model of asphalt mixture, the number of contact points between coarse aggregates is counted; S3, collect the magnitude and direction of the contact force between coarse aggregates, calculate the angle between the contact force and the loading direction, and the component of the contact force along the loading direction; S4, calculate the physical contact parameters of the contact points between coarse aggregates, including the relative stable length, relative stable area and relative stable volume of the contact points; S5. Establish a calculation model for the bearing capacity index of the coarse aggregate contact network of asphalt mixture.

2. The method for characterizing the contact network of coarse aggregate in asphalt mixture according to claim 1, characterized in that: In step S1, a three-dimensional dynamic compaction model of asphalt mixture is established using PFC 3D, including: Using discrete element numerical simulation technology, PFC 3D software was used to establish virtual coarse aggregate and asphalt mortar; Contact models are set up between asphalt mortars, between coarse aggregates, and between asphalt mortar and aggregates to generate virtual asphalt mixture specimens.

3. The method for characterizing the contact network of coarse aggregate in asphalt mixture according to claim 2, characterized in that: The three-dimensional dynamic compaction model of mixture refers to the rotational compaction model; Walls are set at the top and bottom of the specimen, and compaction parameters are set. A virtual compaction specimen is formed by applying pressure to the top wall.

4. The method for characterizing the contact network of coarse aggregate in asphalt mixture according to claim 3, characterized in that: The compaction parameters are: vertical pressure 600Kpa, internal rotation angle 1.15°, rotation rate 30r / min, and designed compaction times 100.

5. The method for characterizing the contact network of coarse aggregate in asphalt mixture according to claim 1, characterized in that: In step S2, the number of contact points between coarse aggregates refers to the number of contact points between any coarse aggregates within the particle size range of 4.75 mm to the nominal maximum particle size.

6. The method for characterizing the contact network of coarse aggregate in asphalt mixture according to claim 1, characterized in that: In step S3, the loading direction refers to the direction of pressure applied to the top wall, and the expression is: F ci =F i ·cos<min{a,b}> In the formula, F i is the contact force at the contact point between coarse aggregates, a is the angle between the positive contact force and the loading direction, and b is the angle between the negative contact force and the loading direction.

7. The method for characterizing the contact network of coarse aggregate in asphalt mixture according to claim 1, characterized in that: In step S3, calculating the angle between the contact force and the loading direction refers to calculating the acute angle between the contact force and the loading direction.

8. The method for characterizing the contact network of coarse aggregate in asphalt mixture according to claim 1, characterized in that: In step S4, the relative stable length of the contact point is calculated as: In the formula, R L is the relative contact length of any two contacting coarse aggregates, L is the height of the virtual specimen; The relative stable area is calculated as: In the formula, R S is the relative contact area between any two contacting coarse aggregates, R SS is the interstitial area of ​​coarse aggregate; The relative stable volume is calculated as: In the formula, R V is the relative contact volume of any two contacting coarse aggregates, and V is the volume of the virtual specimen.

9. The method for characterizing the contact network of coarse aggregate in asphalt mixture according to claim 1, characterized in that: In step S5, the calculation model of the asphalt mixture coarse aggregate contact network bearing capacity index is: Where NMAS is the nominal maximum particle size of the virtual asphalt mixture, i is the particle size classification of the coarse aggregate, i = 4.75, 9.5, 13.2, 16, 19, 26.5, 31.

5.

10. A coarse aggregate contact network characterization system for asphalt mixture, characterized in that: The system is used to control the asphalt mixture coarse aggregate contact network characterization method according to any one of claims 1 to 9, and the system comprises: The compaction process simulation module is used to establish a three-dimensional dynamic compaction model of asphalt mixture using PFC 3D to realize compaction process simulation; The module for counting the number of contact points between coarse aggregates is used to count the number of contact points between coarse aggregates using a three-dimensional dynamic compaction model of asphalt mixtures; The module for calculating the contact force between coarse aggregates is used to collect the magnitude and direction of the contact force between coarse aggregates, calculate the angle between the contact force and the loading direction, and the component of the contact force along the loading direction; The physical contact parameter calculation module is used to calculate the physical contact parameters of the contact points between coarse aggregates, including the relative stable length, relative stable area and relative stable volume of the contact points; The coarse aggregate contact network characterization module is used to establish a calculation model for the bearing capacity index of the coarse aggregate contact network of asphalt mixture and realize the characterization of the coarse aggregate contact network of asphalt mixture.

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