Porous Media

Soil or rock can be considered as a multiphase medium consisting of a solid phase (solid matrix) and of one or more fluid phases (gas and liquids), which occupy the void space (Fig. 3.1). Fluids are immiscible, if a sharp interface is maintained between them. In general, a phase is defined as a part of a continuum, which is characterized by distinct material properties and by a well-defined set of thermodynamic state variables. State variables describe the physical behaviour at all points of the phase. They must vary continuously within the considered phase of a continuum. Phases are separated from each other by surfaces referred to as interphase boundaries. Transport of components may occur within a phase and/or across interphase boundaries. Those interphasic exchange processes between adjacent phases can result from diffusive and/or advective mechanisms.