Prediction Of Mechanical Response Of Asphalt Pavement Based On 3D Discrete Element Method

Since the reform and opening up,the construction of road infrastructure in our country has developed rapidly.At the same time,asphalt pavement has been extensively used because of its advantages of smoothness,noise reduction and easy construction.During the operation period,the road diseases led by cracking and rutting seriously affect the comfort of asphalt pavement.Especially under the repeated action of heavy load vehicles,the problems such as rutting or cracking appear before the asphalt pavement reaches its designed service life.Therefore,it is of great significance to grasp the mechanical response characteristics of asphalt pavement with different structures such as internal stress and strain under certain load times to enhance the serviceability of asphalt pavement and guide the design of asphalt pavement structure.In recent years,the numerical simulation method has entered the road field,and the discrete element method has shown great vitality by its superiority in solving the problem of discontinuous medium of asphalt mixture.Therefore,based on PFC3D platform and combined with the full-scale acceleration loading test,a 3D DEM of asphalt pavement structure considering temperature gradient distribution was established to analyze the mechanical response characteristics of eight different asphalt pavements under vehicle load.The main steps are as follows:First,the volume fraction of each coarse aggregate was calculated from the design parameters of the pavement structure layer.After the volume fraction calibration calibration,the 3D virtual specimen of asphalt pavement structure was reconstructed based on Python language and PFC3D platform.Secondly,the temperature gradient of asphalt pavement structure was predicted along the pavement depth direction,and the model scale was simplified by considering the influence of load diffusion angle.Given a suitable contact model between different units,the micro contact parameters of Burgers visco-elastic model were obtained by uniaxial creep test.Damage factor D was introduced to modify the parameters of burgers visco-elastic model and the contact parameters were assigned to the corresponding temperatures at different depths.Finally,the appropriate boundary and loading conditions were given to the 3D DEM.Taking low temperature,medium temperature and high temperature as examples,the mechanical response characteristics of eight kinds of asphalt pavements under standard load were analyzed and verified by the data collected from the full-scale acceleration loading test site.The results show that the virtual model of asphalt pavement structure established by PFC 3D could simulate the mechanical response of asphalt pavement under the action of load well.The mechanical response characteristics of asphalt pavement depends on the combination of different pavement structure layer materials.The gain effect of additives is different from each other,which is more significant under high temperature conditions.The middle surface layer is the main action area of shear stress,and the shear properties of the middle surface layer should be increased in the actual pavement design.