Research On Reflective Crack Fatigue Propagation Of Asphalt Pavements With Semi Rigid Base Course Based On XFEM

Reflective crack is the main disease of asphalt pavement with semi rigid base course because of its high stiffness and temperature shrinkage characteristics.Once the base layer cracks,surface layer will crack and propagate to the top of surface layer under cyclic action of base material temperature shrinkage stress and vehicle load because of stress concentration.Newly developed Extended Finite Element Method(XFEM)has its irreplaceable advantages on studying cracks and crack propagation.XFEM makes geometric model of cracks independent from finite element mesh and there is no need to re-mesh,which means that crack tip can propagate through internal elements freely without predefining propagation path.Fracture mechanics and corresponding theory are used in this paper to describe fatigue propagation of cracks.Fatigue crack propagation process is divided into three parts consist of low speed crack propagation,medium speed crack propagation and high speed crack propagation by fracture energy release rate modified Paris Law.In order to describe the crack initiation stage more accurately,a phenomenon model is adapted in this paper.Once the model requirements are satisfied crack propagation mechanism in ABAQUS will be started and the later crack propagation is controlled by modified Paris Law.Firstly,this paper simulated fatigue crack propagation process of semi-circle bending of asphalt concrete beam using XFEM and modified Paris Law.The simulation results coincided well with the experiment results,which meant that the fatigue crack propagation model in this paper was applicable in asphalt concrete materials.On that basis,this paper analyzed fatigue crack propagation regulations of surface layer under cyclic temperature shrinkage stress of base course.The simulation realized the free propagation of reflective crack.The analyses also obtained change regulation between reflective crack propagation length and cyclic temperature shrinkage stress action of base course.Moreover,influence of changing structure and material parameters on reflective crack propagation was studied.Then,regulations of unbalanced transportation load action on reflective crack were analyzed.The results indicated that unbalanced transportation load mainly influenced the propagation mode of reflective crack from mode ? to mode ?-?.Finally,this paper simulatedreflective crack propagation regulation under coupling action of temperature shrinkage stress of base course and unbalanced transportation load.The results show that reflective crack propagated in the mixed mode of ?-? and fatigue life under coupling action of temperature shrinkage stress of base course and unbalanced transportation load was about the same as that under only temperature shrinkage stress of base course,which meant that temperature shrinkage stress of base course was the main driving force of reflective crack propagating.