Characterization of Vertical and Horizontal Propagations of Double Cracks in Asphalt Pavements under Moving Loads

The purpose of this research is to analyse the evolution of vertical and horizontal propagations of double cracks in asphalt pavements under moving loads using fracture mechanics and finite-element numerical simulations. In this regard, the effects of cracking space and reflective cracking depth on surface top-down cracking and base layer reflective cracking were studied by considering the viscoelastic behaviour of the surface material. Subsequently, crack propagation was characterized and the fatigue lives due to surface top-down cracking under different moving load levels were evaluated. The results indicated that surface top-down cracking mainly occurred in the type Ⅱ mode. Moreover, the cases of single crack and zero crack spacing corresponded to the conditions of most critical and noncritical propagations, respectively. However, crack spacing and the depth of reflective cracking did not have a significant influence on its propagation. For base layer reflective cracking, the most severe type Ⅰ and Ⅱ propagations occurred within a 400 mm cracking space, and the crack propagation level grew with increasing depth. The fatigue lives due to top-down mixed mode cracking under different moving load levels ranked in descending order as high speed, static state, low speed, and braking state. The fatigue life in the braking state was only 20.4% of that in the high-speed state.