Behaviour of Granular Materials for Pavements in a Hollow Cylinder Apparatus

Unbound granular materials used in pavement structures are subjected to a complex stress path that includes rotational stresses. Hollow cylinder apparatuses (HCAs) are suitable laboratory devices for reproducing stress paths found in the field. However, as the size of the HCA depends on the size of the granular particles, their use for testing unbound granular materials for pavements has received limited attention in the literature. This paper presents some results about the behavior of granular materials for pavements tested in a hollow cylinder apparatus. This large HCA has hydraulic actuators for vertical movement and torsion while shear and vertical stresses are servo-controlled to reproduce stress paths produced by a heavy vehicle moving on a pavement structure. Confining stress is applied using rings with controllable stiffness. The results show the effect of stress rotation on the behavior of unbound granular materials used in pavement structures.