Nonassociated Flow and Stability of Granular Materials

Abstract

Materials exhibiting nonassodated flow should, according to Drucker's stability postulate, become unstable when exposed to certain stress paths inside the failure surface. Results of a series of triaxial tests designed to expose the type of behavior displayed by granular materials are presented and discussed. The sand dilates during shear, it exhibits nonassociated flow, and when exposed to stress paths in the region of potential instability, none is observed. The reliability of the test results, the possible influence of viscous effects on the stability, and the effect of release of elastic energy are studied and discussed in detail. Thus, Drucker's stability postulate is not applicable to granular materials. The type of volume‐change behavior displayed by the material is of great importance in the question of stability of granular materials.