An equation to account for the volumetric behavior of unsaturated soils is proposed in this chapter. This equation is based on the effective stress principle and results in a unifying framework for the volumetric behavior for both saturated and unsaturated soils. The results of the proposed equation are compared with experimental results published by different researchers. These comparisons show that the equation is adequate to account for wetting-drying and net stress loading-unloading paths. This analysis confirms that the effective stress principle can be applied to the volumetric behavior of unsaturated soils.
Keywords: Collapse, Compression index, Controlled suction test, Effective stress principle, Effective stress, Elastoplastic framework, Hydro-mechanical coupling, Isotropic triaxial test, Macropores shrinkage, Suction hardening, Unloadingreloading index, Unsaturated soils, Volumetric behavior, Water menisci, Yield surface.