On yielding and flow of sand; A generalized two-surface model

This paper presents an extension to the concepts and ideas put forward in three articles by the first author and his colleagues during the 1966–1967 period [1].An isotropic-kinematic hardening rule for sand is proposed applicable to both monotonic and cyclic loading conditions. It is based on the theory of bounding surface plasticity incorporating, as in the previous studies, a non-associated flow rule. A three dimensional formulation of the constitutive relation is provided and a comparison of the predicted behaviour and observed responses for a number of undrained loading programs is presented.