Conditions for elasto-plastic strain localization in unsaturated soils

The necessary and sufficient conditions for elasto-plastic strain localization initiation in unsaturated soli massifs are proposed. Unsaturated behaviour is described unsing net stress and suction as independent stress variables and modifying the basic constitutive surface parameters and hardening rules to consider the role of suction. The process is accepted to be static isothermal. The conception that the localization band initiates due to loss of stability of deformation process is used. In that case, the rates of process measures bifurcate. A special example is given to illustrate the application of the obtained conditions.