Thermodynamically based mixture models of saturated and unsaturated soils

Many geotechnical problems are conditioned by the coupling effects between the solid matrix and fluid transport, in particular in unsaturated zones: construction of embankments, cyclic loading of road foundations, environmental engineering, etc. An understanding of the behaviour of saturated/unsaturated soils is therefore important for the design and analysis of those geostructures. In this paper, the Svendsen–Hutter thermodynamic theory of a mixture of isotropic visco-elastic materials is summarized and applied to the formulation of field equations for saturated/unsaturated, compressible/incompressible soils. Emphasis is on the presentation of differences in the formulation, the roles of thermodynamics and configurational as well as saturation pressures. The theory is illustrated by studying (1) viscous mixtures (saturated binary/ternary mixtures and unsaturated binary mixtures) and (2) the statics of elastic soils. Several variants of this modern thermodynamic theory are presented. We establish a thermodynamic basis for well-known concepts of effective stress in saturated and unsaturated soils. Copyright © 1999 John Wiley & Sons, Ltd.