Effective stresses for unsaturated states stemming from clay microstructure

The paper first discusses a novel microstructure conceptual model for compacted clays based on the assumptions that compacted unsaturated clay is made of a water-saturated part (pores filled with water) and an air-saturated part (pores filled with air). The microstructure conceptual model is exploited to interpret a variety of MIP from the literature. The paper then shows the capability of the two effective stresses for unsaturated states stemming from this microstructure conceptual model to model volume change and shear strength behaviour of compacted clays. The model built around these two effective stresses is based on the assumption that the water saturated part behaves like reconstituted clay under saturated conditions and the air-saturated part behaves like clay compressed from dry powder under dry conditions. As a result, mechanical behaviour of compacted clay is modelled by only considering constitutive parameters from reconstituted clay and clay compressed from dry powder.