The effective stress in insaturated soils: Insights from thermodynamics

An effective stress approach can be employed for modeling hydro-mechanical behavior of unsaturated soils. However, any constitutive modeling which is based on the effective stress approach needs a correct definition and formulation of the effective stress. Recent theoretical studies based on the micromechanics have revealed different aspects of the effective stress in unsaturated soils such as its tensorial nature and the importance of the contractile skin forces. In this paper, the results of a new method based on rational thermodynamics have been presented and discussed which sheds light into the effective stress formulation. The results of the proposed thermodynamic approach support the previous studies based on micromechanics by emphasizing on the tensorial nature of the different terms involved in the effective stress formulation as well as the importance of the interfacial energy in mechanical behavior of unsaturated soils