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.
