Influence of Nonassociativity on Localization and Failure in Geomechanics Based on Gradient Elastoplasticity.

We present results of a parametric study on shearband formation in geomaterials, examining the influence of material dilatancy on shearband properties. The study is based on a new higher order continuum theory, called gradient elastoplasticity, developed to model localization of deformation. We present results for two problems with different initial stress fields: The biaxial test and the hollow cylinder test. We show that nonassociativity promotes bifurcation at lower deformation, leading to localized deformation and more abrupt final failure. Both the inclination and thickness of the calculated shearbands decrease with increasing nonassociativity. Gradient elastoplasticity is capable of reproducing the experimentally observed localized failure modes, including details such as reorientation of shearband close to a free boundary. [ABSTRACT FROM AUTHOR]