Study On Moisture Damage Mechanism Of Asphalt Pavement Under The Water-load Coupling Action

Early damage to asphalt pavement such as spalling,the water damage of asphalt pavement has become one of the most serious diseases which endanger the asphalt pavement of our country,so it is urgent and necessary to discuss the mechanism of water damage of asphalt pavement.In this paper,a macroscopic and microscopic model of asphalt pavement is established using Abaqus finite element software to study the mechanical behavior of saturated asphalt pavement under the coupling action of pore water pressure and driving load,and the relationship between them and the moisture damage of asphalt pavement.Firstly,the macroscopic finite element model of saturated asphalt pavement is established to calculate the pore water pressure of the asphalt pavement when the driving load is 0.7MPa,0.9 MPa,1.1MPa and the driving speed is 80km/h,100km/h and 120km/h respectively.The distribution of pore water pressure under different conditions and the relationship between pore water pressure and driving load and driving speed are analyzed.Under the simulation conditions,the analysis results show that the pore water pressure caused by the load of the saturated asphalt pavement is the largest,however,as the depth of pavement structure increases,the value of pore water pressure decreases gradually.The larger the load,the larger the pore water pressure in the pavement structure increases with the increase of the driving load.With the increase of driving speed,When the pore water pressure of asphalt pavement is increased,the influence of velocity on the middle and lower layer is obviously weakened,and the pore water pressure course of the pavement is different step,and the lower layer is lagging behind the upper layer.Secondly,a meso-dimensional finite element model of saturated asphalt pavement is established,and the relationship between the maximum principal stress,maximum principal strain and vertical displacement of asphalt pavement under the coupling action of different speed(80km/h,100km/h,120km/h)with water and driving load is analyzed.Under the simulation conditions,the analysis results show that the gap edge of asphalt mixture and the stress near the interface of asphalt and aggregate,the strain and displacement are larger;Due to the low strength and stiffness of relative aggregates,the influence of pore water pressure and driving load is more sensitive to the effect of asphalt mortar on the velocity;because the dissipation of pore water pressure requires a process,When the aggregate and asphalt mortar in asphalt mixture are unloaded,the displacement of aggregate will be restored immediately,but the displacement of asphalt mortar will not be restored immediately,but relative delay.Finally,by analyzing the relationship between water and driving load and the moisture damage of asphalt pavement,it is considered that the pore water pressure formed in the voidwill produce scour,squeeze and suction effect on the asphalt mixture around the pore under the action of the load of the saturated asphalt pavement.Because of the different mechanical properties,such as the strength and stiffness of asphalt mortar and aggregate itself,the variation of stress,strain and displacement on the interface between asphalt and aggregate adhesion under the action of one load shows a great difference,and the interface between asphalt and aggregate is subjected to continuous difference under the coupling action of repeated traffic load and pore water pressure,The adhesion is gradually reduced,which causes the separation of asphalt and aggregates,which results in the moisture damage of asphalt pavement.