Stresses and deformation in two layer pavement structures under slow repeated loading

Abstract

Successful performance of a pavement structure depends on elastic behaviour of the constituent materials under repeated loading. A laboratory examination of the behaviour of sand and a sand bitumen mix suggests that these granular materials can be conditioned to behave quasi elastically provided they are proof loaded to a stress level higher than that required in service. The stress strain characteristics of these materials under slow repeated loading are such that the 'true' elastic modulus is that measured on the unloading cycle in a compression test (the rebound modulus) not, as has been assumed previously, the value obtained from a single loading cycle. Tests on model pavements in the laboratory have indicated that the stresses in two layered systems follow the predictions of the linear elastic theory closely with respect to mode of distribution but the evaluation of the effective modulus still presents a serious problem. It is likely that the behaviour is non linearly elastic. It can also be shown therefore that, in the absence of proof loading, elastic theory cannot predict adequately the total deformation of a pavement surface (A).