The Analysis Of Fatigue Fracture Of Asphalt Pavements Base On Surface Cracking

There inevitably exist defects or cracks in asphalt mixture for pavement. Repeated traffic loading may cause stress intensification at the tip of the crack, resulting in crack propagation in a complex mode from the surface to the bottom and final failure of the pavement. This thesis discusses the fatigue life of asphalt pavement using principles of fracture mechanics. Results of analysis show that Generalized Paris Law can consider the complex crack propagation in the material of the pavement structure. The fatigue life of the pavement increases with increasing thickness of surface layer in a power function. Use of a thicker surface layer may extend the service life of the asphalt pavement. The fatigue life increases with decreasing modulus of surface layer in a power function with a negative exponent. However, since reduced modulus would scarify the structural strength and might cause rutting-related distress, caution should be taken when using low modulus materials for improving fatigue performance of asphalt pavements. The fatigue life increases with increasing modulus of base material in a power function. However, the fatigue life can not infinitely increases with increasing modulus of the base. With an ascending segment, the fatigue life curve tends to a constant. The fatigue life of the pavement increases nearly linearly with increasing thickness of subbase in a power function. In the currently method of pavement structure design, the thickness of surface layer is to some degree arbitrarily determined, and then the thickness of base or subbace is adjusted for the equivalent single axle loads by calculation. Analysis results of this thesis show that when the fatigue life is reached, the surface layer would completely fail, causing accelerated damage of the entire pavement. The increase in the thickness of base or subbace can not infinitely increase the number of equivalent single axle loads. In addition, results of this thesis show that the fatigue life significantly decreases with increasing axle load of vehicle in a power function with a negative exponent.