Fatigue Life Analysis of Composite Pavement with Multiple Overlays

Two 3D finite element models are established to analyze the mechanical response of road construction and solve the problem in which the actual fatigue life of the overlay is significantly shorter than the designed value. The first model is composite pavement with multiple overlays, whereas the second model is pavement overlaid with the same thickness of asphalt concrete. Calculation result indicates that interlaminar bonding condition significantly affects shear stress and tensile strain, and the value calculated by the second model is smaller than that calculated by the first model, which may lead to unsafe design. The following conclusions can be drawn based on the tendency of interlayer shear to form along the direction of road depth. (1) The interlaminar shear of old pavement decreases when overlaid with asphalt concrete, whereas maximum shear stress always occurs at the bottom of the surface layer. (2) When pavement overlay frequency is increased, the interlaminar shear value of the surface layer will be increased. The value of interlayer shear stress mutation increases with the frequency of overlay. The simulation results show that the service life of asphalt overlay decreases with the frequency of overlay, which indicates that overlaying asphalt cannot improve the stress state of the surface layer. By contrast, the comprehensive influences of interlaminar bonding condition and composite load will increase surface stress, which may eventually intensify surface damage.