Experimental Stress-Dilatancy Relations of Sand Subjected to Cyclic Loading

Abstract

Cyclic triaxial tests, cyclic torsional shear tests on isotropically consolidated specimens and cyclic torsional simple shear tests on one-dimensionally consolidated specimens, using saturated Toyoura sand, were performed under drained conditions in order to investigate the general tendencies of the stress-dilatancy characteristics under cyclic loadings. It was found that in each testing method a unique relationship between the stress ratio and the dilatancy factor (strain increment ratio) exists irrespective of void ratio and pressure level. In each testing method, the rate of dilatancy, as defined as the rate of volumetric strain increment to shear strain increment (positive for volume expansion), becomes negative by the reversal of loading direction. Then it increases continuously with shearing without showing any discontinuous behavior at the moment when the sign of shear stress changes (i.e., at the neutral stress point), and subsequently it becomes positive. It was also found that in the triaxial tests an over-consolidation stress history affects the stress-dilatancy relation only below a certain stress ratio in the first loading and has no effect in the subsequent shearing. (Author/TRRL)