Analysis Of The Mechanical Response Of Semi-rigid Base Asphalt Pavement Under Heavy Load

At present,China's highway transportation has the following characteristics: 1)heavy traffic tasks,heavy traffic prominent;2)overload phenomenon is widespread,in many areas the overload rate of heavy vehicles averages more than 50%,in some areas the road overload degree is even between 80% and 300%;3)the grounding pressure is mainly between 0.8 MPa and 1.1 MPa,and even in some cases the grounding pressure can be as high as 1.6 MPa.But for heavy load,the asphalt pavement design specifications in our country do not take into account;many scholars believe that the bonding state between asphalt base pavement is a whole,but according to the site drilling and the use of follow-up roads,it is found that the interlayer damage of asphalt pavement starts from a small area and then gradually expands,eventually leading to early damage of the pavement.Therefore,it is of great significance to study the local bond failure of the base course under heavy load to reveal the early damage of asphalt pavement.The horizontal force is not considered in the design of asphalt pavement in China,but a large number of practical surface horizontal forces have a significant impact on the damage of asphalt pavement.In this paper,ABAQUS is used to establish elastic model and elastic-plastic model to analyze the distribution of mechanical indexes of asphalt pavement under 100 KN,130KN,150 KN,180KN,200 KN,250KN and 300 KN axle loads.Based on the current "Design Code for Asphalt Pavement on Highway"(JTG D50-2017),the pavement structure is checked.On this basis,local bond failure and horizontal force are considered.Influence.The main research contents are as follows:(1)When the elastic model is used,the values of each index increase linearly with the increase of axle load,while the fatigue cracking life of asphalt mixture,the fatigue cracking life of inorganic binder stabilizer,the permanent deformation of asphalt mixture and the compressive strain of soil top decrease in logarithmic function with the increase of axle load.When using elastic-plastic model,the deflection,shear stress and bottom tension stress of inorganic binder layer increase linearly with the increase of axle load,while the compressive strain and bottom tension strain of asphalt layer increase parabolically.The mechanical index value calculated by elastic-plastic model is larger than that calculated by elastic model,and the calculation result is more conservative.Therefore,the elastic-plastic model is recommended in the analysis of heavy load.(2)When considering the local bond failure area of the base layer under heavy load,the deflection value of the two wheels centers is no longer equal,but the maximum value is obtained on the side where the bond failure area exists.The greater the bond failure area and the axle load,the greater the deflection difference.The local bond failure zone has little effect on the compressive stress and the compressive strain in the surface layer.When the bonding failure zone is considered,the shear stress will suddenly decrease in the middle layer,and the maximum shear stress is larger than that without considering the bonding failure zone.The existence of bond failure zone makes the maximum tensile strain at the bottom of asphalt layer transit from the bottom of middle layer to the bottom of surface layer,and the tension strain at the loading area of two wheels is no longer equal.Therefore,the existence of local bond failure zone makes the asphalt pavement destroy at the bottom layer first,and then transfer upward,leading to the overall damage of asphalt pavement,thereby reducing the fatigue life of pavement.(3)The influence of the horizontal force along the driving direction on the pavement structure is greater than that of the centrifugal force.For deflection and compressive stress,the influence of horizontal force on its numerical value can be neglected,only affecting its position.The larger the horizontal force is,the more obvious the migration effect is.Under the action of horizontal force,the maximum value of vertical compressive strain and tensile strain at the bottom of asphalt pavement moves gradually from the bottom of middle layer to the surface,which causes great plastic strain at the bottom of upper layer of asphalt pavement and leads to tensile crack at the top layer of asphalt pavement.The existence of horizontal force makes the maximum shear stress no longer be obtained at the top of the middle layer,but at the surface of the road.Therefore,the horizontal force makes the asphalt pavement shear failure on the surface and the upper layer first.