Analysis On Reflection Crack Fatigue Propagation Of AC-CRC Composite Pavement

AC-CRC composite pavement has strong bearing capacity,good driving comfort and the characteristics of both rigid and flexible pavement.It has been applied in China’s expressways,especially heavy haul roads.Under the long-term action of temperature stress and vehicle load,the inherent transverse cracks of continuous reinforced concrete(CRC)base are easy to be reflected into the asphalt concrete(AC)surface course and finally run through the whole asphalt surface course.The fatigue propagation of reflective cracks in composite pavement should be paid attention to.In this paper,the extended finite element(XFEM)method is introduced and combined with the improved Paris formula of energy release rate to study the fatigue propagation of reflection cracks in composite pavement,which overcomes the limitations of the traditional finite element method.Using the extended finite element method,this paper focuses on the fatigue growth of reflective cracks in composite pavement under the action of temperature shrinkage stress cycle,and obtains the relationship between the number of temperature shrinkage stress cycles and the crack length in asphalt pavement and the change law of energy release rate at the crack tip.The results show that when the temperature of continuously reinforced concrete base changes slightly,the energy release rate at the crack tip can be reduced and the fatigue life of the surface layer can be prolonged;The fatigue life of asphalt pavement increases with the increase of base reinforcement ratio,and the thickness of pavement effectively resisting crack propagation increases;The asphalt pavement with higher limit value of energy release rate has longer fatigue life and enhanced ability to resist reflection crack propagation;The fatigue propagation path of cracks in thicker surface layer is longer and the fatigue life increases;The influence of CRC layer modulus,CRC layer thickness and subbase modulus on crack fatigue propagation is very limited.Using the extended finite element method,this paper also studies the fatigue propagation law of reflection crack of composite pavement under the action of single vehicle load and temperature shrinkage load.The results show that when the initial crack length in the asphalt pavement is small,the reflection crack of the composite pavement does not expand under the action of a single vehicle load;The fatigue propagation type of composite pavement reflection crack under the combined action of temperature shrinkage and load is I-II composite type.Vehicle load has little effect on the fatigue propagation life of composite pavement temperature shrinkage and load composite reflection crack.The power of crack propagation mainly comes from temperature shrinkage stress.With the increase of load,the fatigue propagation life of crack is shortened.