Research On The Law Of Shear Rheological Damage Of Asphalt Mixture Based On Three-Dimensional Discrete Element Method

The shear failure(such as rutting and shoving etc.)is one of the most common failure types of asphalt pavement,causing great economic losses and negative social effect.With this regard,there are lots of research conducted in domestic and abroad,and the importance of combining macroscopic and microscopic research is gradually recognized.Since the discrete element method(DEM)was introduced into the microscopic study of asphalt pavement,the research mainly focused on the stiffness modulus and fatigue properties of asphalt mixture,while the research on shear rheological behavior was less.Therefore,the methods of the combination of macroscopic and microscopic,and the methods of combination of experiments and theories were adopted in this project.The shear rheological damage laws of asphalt mixture were studied by discrete element method.This paper takes AC-13 asphalt mixture as the main research object.First,the Hamburg rutting test and repeated loading creep laboratory tests were carried out.Then,using the particle flow code PFC3D of the three-dimensional discrete element method,the AC-13 asphalt mixture virtual model is constructed by random placement method,and the virtual Hamburg rutting test and virtual repeated loading creep tests were performed on it.The shear failure mechanism and the creep deformation mechanism during the test loading process were analyzed from a microscopic point of view.The effects of temperature,load and humidity on the anti-deformation performance of asphalt mixture were analyzed,and accuracy of the discrete element model was verified by comparison,Finally,this paper also constructed a number of control specimens,and further explored the material selection and grading design methods that can alleviate the shearing disease of asphalt pavement.The results show that the discrete element model can accurately simulate the asphalt mixture rutting test and repeated loading creep test,and the relative error of the final test is below 10%.In the Hamburg rutting test,the internal contact force and the aggregate displacement of the virtual test piece are distributed in a "V" shape that under the wheel action area,and rapidly decay to both ends of the test piece.The displacement of the aggregate in the Z-axis and X-axis directions increases with the increase of the number of loadings,and there is a certain reciprocating movement process in the Y-axis direction.The aggregate still maintains a high level of displacement at a eertain depth from the top of the test piece,indicating that the small depth of the asphalt pavement from the top to the bottom i5 the peak area where the structure is sheared.In the repeated loading creep test,as the temperature and load increase,the axial strain generated under the same loading times increases,the number of rheological changes decreases,and the anti-permanent deformation ability of the asphalt mixture decreases to some extent.In order to alleviate the shearing disease of asphalt pavement,eoarse aggregates with high friction coeffieient,rich surface texture,rich comers and high viscosity asphalt should be selected.According to the simulation results,in the grading design,SMA,OGFC and other types of grading with a developed skeleton,and aggregates with a maximum nominal particle size of 13mm or 16mm can provide higher resistance to permanent deformation.