The Yielding Behavior of Particulate Media

Abstract

This paper presents a discussion of the yielding behavior of particulate media during shearing, based on the results of a laboratory investigation of the stress–strain properties of samples of glass microspheres. The test program, carried out on hollow cylinder specimens, studied the effect of functions of the three stress invariants on the stress–strain behavior.It is suggested that a 'yield' point may be defined, below which relatively little interparticle slippage occurs. Below this yield point, stress–strain relations under any particular stress-path may be predicted from superposition of isotropic and deviatoric components. An initial yield point is defined which is shown to occur at a constant ratio of octahedral shear to normal stresses, so obeying an extended Von Mises type criterion.With regards to the post-yield-point behavior, an expression is developed for the yielding behavior, based on an assumed mechanism of energy dissipation within the mass. This yield relation expresses the lack of normality between the strain increment vector and the yield function, known empirically to exist in granular materials, and shows that the deviation from normality is constant, and related to the true angle of interparticle friction, [Formula: see text].