Effects of surface cracking on responses in flexible pavements

This paper investigates the effects of surface cracks on the primary responses to wheel loading in a model of a flexible pavement structure. Details of the modelling procedure using finite-element analysis are presented and the effects of different material properties and crack lengths are reported. Results show that in an uncracked flexible pavement structure, the inclusion of horizontal tractions imposed by the wheel load results in narrow regions of horizontal tensile strain at the pavement surface and a high shear strain at the edge of the tyre which could lead to crack initiation. The presence of a surface crack results in a localised region of high horizontal tensile stress and strain at the edge of the tyre, making further crack propagation possible. The predicted horizontal tensile strains increase as the stiffness modulus of the asphalt layer is decreased. The presence of a surface crack results in a high value of shear strain at the crack tip, which increases as the stiffness modulus of the asphalt layer is decreased. The predicted horizontal tensile strain at the base of the asphalt layer is not sensitive to a surface crack until it reaches approximately 50 mm (25% of the layer thickness), after which it increases. The predicted shear strain at the crack tip increases linearly with increasing crack length.