Study On Longitudinal Slippage Crack Of Asphalt Pavement Based On Cohesive Zone-extended Finite Element Model

With the rapid development of the transportation and vehicle,the frequency and load of the vehicle on the pavement surface are gradually increasing,but the pavement structure has a lot of deficiencies against the load.In the area where the horizontal load of vehicle frequently acts,that is,the frequent acceleration and deceleration of vehicles,U-shaped slippage crack often appear in the asphalt pavement surface layer,and the pavement structure is accompanied by the phenomenon of interlayer slip due to adhesion failure.Therefore,the mechanism analysis of the phenomenon provides a theoretical basis for the relevant departments to prevent the occurrence of this phenomenon in actual engineering.In this paper,the interlayer slip and the longitudinal slippage crack in pavement surface is the main research object.After investigating and analyzing the characteristics and causes of longitudinal slippage crack disease,the finite element model of interlayer contact between multi-layer structures of asphalt pavement is established.The correctness of the finite element model is verified by the finite element model mesh size convergence analysis and experimental data comparison.On this basis,the state of static-dynamic pavement slippage crack and interlayer adhesion failure is analyzed,and the mechanism of slippage crack generation is obtained.Then the changes of longitudinal slippage cracks and interlaminar bond failure states under different parameters are simulated and analyzed.The main research contents are as follows:(1)Based on the finite element model size of asphalt pavement,the mesh size convergence analysis of finite element is carried out to improve the numerical accuracy of the finite element model.The analysis of the interlayer contact between the asphalt layers is then carried out.(2)The mechanical response of the pavement model structure under horizontal load is analyzed.By comparing the mechanical response with the surface material strength and the interlaminar bond strength,static cracks are introduced.The crack propagation angle is calculated by the maximum energy release rate failure criterion and the second nominal stress failure criterion is used to determine the change of the interlayer failure area,and then the formation of the slippage crack and the accompanying interlayer failure caused by the interlayer slip are analyzed step by step.(3)By using the extended finite element(XFEM)module in ABAQUS to analyze the dynamic expansion of the slippage crack and the change of the interlayer bond failure under quasi-static load;moreover,applying dynamic load to analyze the dynamic propagation of slippage crack and interlayer bonding state.By comparing the forms of the two types of slippage cracks,the quasi-static load can be applied to improve the solution time of the finite element model under taking into account the accuracy of the simulation results.(4)Comparative analysis of the Young's modulus of the surface layer material,the thickness of the upper layer,the bond strength between layers and the overload on the mechanical response-longitudinal tensile stress,longitudinal shear stress and the failure of interlayers and surfaces are made,and then analysing the change of the failure state of the interlayer bond and the expansion of the surface slippage crack.Finally,the influence of different factors on the main mechanical variables of slip cracks-longitudinal tensile stress and longitudinal shear stress is analyzed based on the grey theory.