A numerical estimate of localized deformation in geomaterials with a double-slip model

In many experiments of indentation onto geomaterials, there are observed many localized shearing bands at their rather early stages of loadings which cannot be predicted by the classical ultimate analysis. We here propose a simple constitutive relation in which a double-slip model is used to describe post-bifurcation micro-behavior. As the bifurcation criterion, the localization condition within the framework presented by Hill is used. Numerical examinations on tensile tests of materials with non-coaxial plasticity show no mesh dependency. Examples of analyses are a simple indentation problem under a direct footing as well as compression tests in order to show evolution of the localized plastic deformation.