Study On Numerical Simulation Method Of Asphalt Mixture Based On Three Dimensional Discrete Element Method

At present,it is a vigorous period for China's pavement construction and technology research.However,the various of asphalt pavement distresses still have significant effects on the safety and comfort of vehicle driving.Nowadays,domestic and foreign researchers focus on the study of how to obtain good pavement performance and durability by designing the asphalt mixture,mainly on the macro and physical properties of asphalt mixture.However,limited studies have been conducted on the internal structure and properties of asphalt mixture from the micro point of view.In the current situation,the asphalt mixture design method is complex,low efficiency,heavy workload,and the test results are often not ideal.To improve this situation,it is necessary to explore and develop a set of mature and instructive methods for numerical simulation design of asphalt mixture.In this paper,based on the concept of the structure and composition of asphalt mixture,a three-dimensional numerical test specimen was constructed.The comparative analysis showed that the virtual experiment is consistent with the actual experiment,which verifies the rationality of the numerical model based on the three-dimensional discrete element method.First of all,the irregular convex hull was generated randomly on the Matlab software platform.Then,based on the 3D ODEC algorithm,the Bubble Pack filled in PFC3 D 5.0 and the clump block generation technique were used to generate the coarse aggregate composed of overlapping spheres.The proportion of coarse aggregate was calculated,and the coarse aggregate clump specimen with gradation feature was generated by the rainfall method.Regular array balls with 1 mm diameter was generated to simulate asphalt mortar.Also the vertical distribution of voids in asphalt mixture was simulated.Ultimately,a three-dimensional discrete element numerical model of asphalt mixture was established.According to viscoelastic theory,the contact model among the various internal elements was determined by the material analysis of internal structure.The relationship between micro contact parameters and macro mechanical parameters of Burgers model was established,and the parameters of contact model of asphalt mortar were calibrated by DSR test.The parameters of each component and the relevant parameters of the mechanical contact model between the elements can be used to describe the mechanical properties of asphalt mixture more accurately.Finally,the corresponding parameters were imported to the structural model to establish the model of three-dimensional micro mechanical structure.The volume fraction of coarse aggregate in the model was checked and adjusted by the macro indicators.The triaxial sheartest and uniaxial static creep test were conducted.The comparative analysis showed that the virtual test results are in good agreement with the experimental results.The rationality and the feasibility of the simulation method based on the discrete element method are verified.The relationship between microstructure and macro properties of asphalt mixture was preliminary established.