Evaluating Fatigue Performance Of Asphalt Mixture Based On Mechanical Response Of Asphalt Pavement

Fatigue damage is the key problem in the theory of asphalt pavement design. Viscoelastic response of asphalt pavement under moving vehicle load is the basis of pavement design and it can explain the load-induced fractures in asphalt pavement. Stress and strain condition produced in the traditional fatigue test has a great difference with the actual mechanical response of asphalt pavement. Therefore, the fatigue life prediction equations based on the tensile stress or strain are not sufficiently reasonable, they cannot describe the fatigue damage evolutions under actual loading pulse.This paper considers the characteristics of asphalt mixture and asphalt pavement, the viscoelastic parameters are incorporated into the pavement mechanical analysis under moving vehicle load. A orthogonal method is conducted to analyze the influence of the six main factors on pavement mechanical response, such as moving load, temperature, vehicle speed, thickness of asphalt layer, thickness of subbase and module of subbase. The range analysis is used to get the sequences with taking the tensile and compression strain history as the index.First the typical flexible crushed stone base asphalt pavement is selected as the study candidate; the results show that the stress and strain at the bottom of asphalt layer suffered an alternate tension-compression pulse. As the temperature increases, the peak value of tensile and compression strain history present an exponential growth, the higher the temperature is, the longer the compression stress history duration is. The tensile stress history duration has a power function relation with the vehicle speed. Second, the typical semi-rigid asphalt pavement is chosen to conduct the analysis. The modulus of each layer is considered to reduce with the service life. The results show that the stress at the bottom of asphalt layer is compression at the initial stage, as the modulus reduces, the stress condition changes and becomes into the tensile condition. Moreover, the tensile stress grows dramatically at final stage of service life. The single, tandem and tridem axis are analyzed to calculate the load equivalent factors based on the dissipated energy. The fatigue life prediction equation is established with considering the strain history.The difference between tensile and compression modulus is taken into consideration, The Galerkin method is employed to determine the bimodular stress distribution in the indirect tension specimen. The Galerkin method is compared to an analytical solution, Hondros’ solution.The alternate biaxial splitting(ABS) fatigue loading mode is proposed to conduct the fatigue test based on the above mechanical analysis. The results show that the stress condition produced by splitting fatigue loading is similar to the actual pavement response. Compared with indirect tension(IDT) fatigue test, the ABS loading mode can significantly reduce the permanent deformation. Moreover, the ABS loading mode can produce a longer life than IDT loading mode. When a small transverse loading is applied, the produced compression stress can contribute to the healing of fatigue cracks, but when the traverse loading reaches to a higher level, the compression stress could induce an obvious shear failure. This research could provide a theoretical guidance for fatigue damage study based on the actual pavement respionse.