Research Of The Semi-rigid Asphalt Pavement Structural Fatigue Life

The crack is one of the common problems in pavement diseases. Because of it's rigid behavior, the semirigid subbase is liable to crack under physical condition such as load,temperature and water. These subbase cracks can lead to the reflect cracking in the pavement surface course, then can result in the derogation of the wholly pavement systematic.Nowadays, we usually though loading on the joist in the laboratory to forecast the fatigue life of the semirigid subbase. Whereas owing to the difference between the laboratory and the practice in the load mode and other environmental functions, the fatigue life obtained in the laboratory can not characterize the semirigid subbase actual performance.Based on fracture mechanics and the actual state of the semirigid subbase from investigation, This article builds three-dimensional modeling of the pavement sheets in the finite element software ANSYS, and gets the stress intensity factor in the top of the semirigid subbase cracks. Then though these dates of the stress intensity factor, we use the PARIS formulae of the fracture mechanics and get the fatigue life of the semirigid subbase.This fatigue life is different from the one obtained in the laboratory, it is obtained based on simulation of the whole pavement structure, so it can be called the structure fatigue life of the semirigid subbase. The structure fatigue life is more practical than the one obtained in the laboratory, because it characterizes the semirigid subbase's structure fatigue performance on occasion of the whole pavement structure.The analytic result shows that:there are prodigious stress mutation value in the top of the cracks, and the value of the stress intensity factor can represent the stress concentration's degree of subbase crack tip. Whether the load alone or the load and temperature coupled, basically the stress intensity factor augments with the spreading of the crack, and in the length of 2cm the stress intensity factor has one mutation, while after the 2cm length the stress intensity factor's augmentation is incline to gentleness.The structure fatigue life decries in company with the increment of the subbase modulus, the decrease velocity is relatively fast in the beginning, then slows down. Also the structure fatigue life is different in different temperature, the value of the structure fatigue life is high when the temperature is approaching to the standard, furthermore the gap between the values is high in low subbase modulus, while with the subbase modulus increasing the gap goes down.