PLANE-STRAIN CHARACTERISTICS THEORY FOR SOILS AND GRANULAR-MATERIALS WITH DENSITY DEPENDENT YIELD CRITERIA

An Analysis of the quasi-static, plane strain, deformations of a rigid/plastic material whose yield stress depends on the current material density is presented. Both steady and unsteady flows are studied. Such constitutive relations are widely used to model the yielding behaviour of soils and granular media in what is generally known as "critical state soil mechanics". It is shown that, contrary to a widely held belief, the stress and velocity characteristics for such materials do coincide. The differential relations along the characteristics are derived and shown to have a structure typical of hardening materials. In addition it is shown that a second family of weak discontinuities, embedded in the material, can exist and that they give rise to the familiar "Sokolovskii stress characteristics" in the critical state limit. © 1989.