Evaluation of asphalt mixture micromechanical behavior evolution in the failure process based on Discrete Element Method

Asphalt mixture was a granular material, and traditional mechanical testing methods were difficult to reveal the failure mechanism. To evaluate the micromechanical behavior of asphalt mixture in the failure process, the DEM (Discrete Element Method) model of the uniaxial compression test was established. The virtual aggregate particle database with real morphology properties was constructed, and the linear parallel bond model was used to simulate the adhesion of asphalt. In the DEM model of the asphalt mixture failure process, the movement of asphalt mortar and coarse aggregate was evaluated, and the Discrete Fracture Network (DFN) was proposed to represent the microcrack. Finally, the three-dimensional spherical coordinate histogram was used to analyze the evolution of magnitude and direction of the coarse aggregate skeleton contact force. It found that the movement of coarse aggregate was less than that of asphalt mortar in the process of the uniaxial compression test, and the coarse aggregate movement was affected by its particle size and location. The result also found that although the adhesive and cohesion failure could occur at the same time, the adhesive failure was less than cohesion failure in the early stage of the uniaxial compression test, and the aggregate with larger particle size could reduce the generation of adhesive failure. Compared with the magnitude of coarse aggregate skeleton contact force, the change of direction was the main reason for a decrease in stress when the asphalt mixture specimen exceeded the peak strength.