Research On Asphalt Pavement Milling Process And Milling Parameters Optimization Based On The Discrete Element Method

At present,the workload of pavement maintenance in China is showing a momentum of rapid growth.Asphalt pavement milling operation is an important part of maintenance work,and the amount of milling materials produced therefrom is huge.However,milling materials are often severely broken or have large agglomerates,which seriously affects its recycling rate.As stone resources are increasingly scarce,milling materials are an important renewable resource.How to improve the recycling rate of pavement milling materials and reduce the cost of pavement milling operations has become the focus of pavement milling work.Due to the different composition of the asphalt mixture,its mechanical response under the action of the milling cutting tool is different.For different asphalt mixtures,the use of reasonable milling operation parameters,such as milling speed,milling depth,etc,is helpful to reduce the aggregate crushing or the generated of larger clumps during the milling process.This is of great significance for improving the recycling rate of pavement milling materials and reducing the cost of pavement milling operations.Repeated pavement milling test will consume huge manpower and material resources.Therefore,with the help of the discrete element software PFC to carry out asphalt pavement milling simulation test research in this paper,in order to achieve the purpose of optimizing the milling parameters.Firstly,SBS modified asphalt was used to prepare AC-13 asphalt mixture specimens for indoor triaxial compression tests under different confining pressure conditions.Secondly,a PFC triaxial compression test model was constructed.According to the characteristics of the internal contact behavior of the asphalt mixture model,different contact models were selected to characterize the contact behavior between adjacent aggregates,inside coarse aggregate particles,between aggregates and asphalt mortar.According to the triaxial compression test of the asphalt mixture,the calibration of the contact model parameters was completed,and the confining pressure conditions were changed to verify the calibrated model parameters.Finally,a discrete element milling model of asphalt pavement was established according to the calibrated contact parameters,and the milling path was optimized to simulate the milling process of asphalt pavement.The influence of pavement milling parameters on the milling effect is analyzed from the perspectives of the force of the milling cutting tool,the utilization of milling materials and the mechanism of milling crushing.The results show: for AC-13 asphalt mixture milling operation,under the conditions of 42°cutting angle and 10°deflection angle,when the horizontal movement speed of the milling machine is 0.2m/s,the angular speed is 160r/min and the milling depth is 25 mm,the direct utilization rate of milling materials is the highest,the crushing rate of coarse aggregate is the lowest,and the combined force on the cutting tool is the smallest.At this time,the loss of the cutting tool is reduced,which is conducive to reducing the cost of milling operations.