INSTABILITY OF DILATING SAND

Stability postulates by Drucker and by Hill are applicable to solid me tal. When applied to granular material exhibiting nonassociated flow, these concepts of stability imply that the material may be unstable wh en exposed to certain stress paths inside the failure surface. Series of triaxial tests on fully saturated and partly saturated specimens ha ve been performed under drained and undrained conditions to study the regions of stable and unstable behavior. The stability postulate by Dr ucker and by Hill do not capture the conditions for stable and unstabl e behavior of granular materials. The experimentally determined condit ions for which granular materials are stable, conditionally unstable, and unconditionally unstable are discussed.