RESILIENT PROPERTIES OF UNBOUND ROADBASE UNDER REPEATED TRIAXIAL LOADING

A study of the non-linear elastic behaviour of unbound, granite and limestone roadbase material has been made and values of moduli and Poisson's ratio determined to provide data for modelling the response of traffic loaded pavements. A dynamic triaxial testing machine incorporating interactive computer control was designed, built and used to make the measurements. The ability of the machine to apply simultaneous radial and axial stresses, and its stability at low load have enabled Young's modulus, and Poisson's ratio characteristics to be established as functions of the mean normal stress p, and the deviator stress q for the complete stress space that can be investigated in conventional triaxial tests on unbound materials. The work illustrates the non-linear effect of both mean normal stress and deviator stress on strain response, and shows that bulk modulus is independent or is an even function of the third stress invariant. These findings are shown to be consistent with parallel research carried out at Nottingham University under contract to the TRRL. (Author/TRRL)