Loss of controllability in unsaturated soils

Abstract

ABSTRACT A study on the triggering of instability modes during soaking of unsaturated soil specimens is presented. A constitutive model for unsaturated soils is linked in fact with the loss-of-controllability theory. The model is based on the concept of energy conjugated generalised stress variables. A convenient expression for effective stresses for partially saturated soils is adopted. It is shown that the saturation index acts as an extensive variable, the corresponding intensive variable being the modified suction. The controllability of generalised loading tests is then considered, with attention to tests at varying water content. It is shown that instability phenomena, such as collapse at constant axial loading and suction, can be described.