A thermodynamic approach to effective stresses in unsaturated soils incorporating the concept of partial pore deformations

We have extended a previously proposed model to include the effect of interfaces in the mechanical behavior of unsaturated soils, and we showed that the Bishop-like stresses involved in the elastic and plastic responses respectively can take different expressions. The Modified Cam-Clay model used for saturated soils is extended to unsaturated soils through the use of these Bishop-like stresses. This model is compared to some experimental results reported from the literature. The thermodynamical analysis presented here follows from the work of Coussy et al., who proposed a thermodynamically consistent model for unsaturated soils that is based on a Bishop-like effective stress to describe the stress-strain relationship while the water saturation (or the capillary pressure) is involved in a saturation-induced hardening in addition to the mechanical hardening. We extended this model to include the effect of interfaces in the mechanical behavior and we showed that the Bishop-like stresses involved in the elastic and plastic responses respectively can take different expressions. The Modified Cam-Clay model used for saturated soils is extended to unsaturated soils through the use of these Bishop-like stresses. This model is compared to some experimental results reported from the literature.