This paper deals with constitutive modeling of soil in saturated and non-saturated conditions, including the volumetric decrease during wetting stress-paths (collapse). It presents an extended effective stress principle that, together with small adaptations made in an elasto-plastic model developed for dry and saturated conditions, allows for modeling soil behavior in non-saturated conditions. Besides briefly discussing theoretical aspects, the paper presents results of triaxial tests performed on a residual soil in saturated and non-saturated conditions, shows how to obtain new parameters included in the model, presents a method to find optimum parameters and shows comparisons between experimental and analytical results obtained with the model.

KEYWORDS: Elasto-plastic modeling; collapse; extended effective stress principle; non-saturated condition; parameters optimization