Analysis Of Stress State And Interface Damage Of Asphalt Pavement Based On Multiscale Model

With the increasing traffic volume,asphalt pavement always get early damage in service life.Cracking is the most common failure mode of pavement which has great influence on the function of asphalt pavement.Pavement materials are treated as homogeneous materials in traditional asphalt pavement design and the design indexes are given at the macro scale,but actually pavement materials are multi-phase composite materials which lead to the heterogeneous stress distribution in pavement.And the stress concentration causes pavement cracking.The macrocracks of pavement start with the microcracks between aggregates and binders.The interface of pavement materials will be in damage under wheel load with microcracks.The repeated load make microcracks develop into macrocracks,eventually reduce the service life of asphalt pavement.Therefore,it is necessary to study the multi-scale stress responses of pavement and the interface damage of pavement materials under wheel load.Based on representative volume element theory,digital image process technology and cohesive zone model,three-dimensional macroscopic finite element model,two-dimensional mesoscopic finite element model and two-dimensional interface model were built in this paper.By the sub-model method,pavement model at the different scale were interconnected,and the multi-scale stress response and damage state of pavement under wheel load were analyzed.The followings are main conclusions:(1)At the macro scale,there is large longitudinal stress at the bottom center of base and subbase between wheel load.But the surface center of pavement between wheel load is in transverse tension.And asphalt concrete layers suffer high shear stress that reaches the peak at binder course.(2)The maximum stress of each layer of pavement at the meso scale is far larger than it at the macro scale.What's more,the extreme stresses are located at the interface between aggregates and binders all time.(3)Interface damage is occurred in base and subbase,as well as the surface layer,while the others have little interface damage.The transverse microcracks at asphaltconcrete layer are mainly sliding-shear cracks,and the longitudinal microcracks at semi-rigid base and subbase are mainly open cracks.(4)Both the adhesive strength and fracture energy of interface have great influence on damage state of interface.While the stiffness of aggregates and binders have little effect on interface damage.The increase of adhesive strength or the decrease of fracture energy of interface will deteriorate the damage state of interface.(5)The interface analysis shows that road materials have already damaged though the analysis of pavement at the macro scale suggests that pavement is in safe under standard wheel load.It is not enough to merely design pavement at the macro scale,the heterogeneity of road materials should be taken into consideration as well.