Work input for unsaturated elastic porous media

The work input for unsaturated elastic porous media is investigated based on averaged conservation equations for phases, interfaces, and common curves. In this analysis, the interfaces between the air–water interfaces are allowed to move and the surface tension appears explicitly in the analysis. Expressions for the work of the solid alone and for the medium are obtained. Conditions under which the result obtained here for the medium reduces to a more traditional expression are indicated. In this analysis, a form of the solid phase stress tensor, recently derived within the framework of thermodynamically constrained averaging theory for phase and interface properties, is used.