ABSTRACT
Understanding pressure in clay soils is critical for determining flow rate, diffusion, and swelling rate. In this paper we summarize recent theoretical work within the framework of hybrid mixture theory which defines three pressures in swelling clay soils: thermodynamic pressure, classical pressure and swelling pressure. The thermodynamic pressure is the pressure associated with the normal force, the classical pressure is related to the pressure one associates with a single phase (usually gas), and the swelling pressure is specific for swelling porous media. We expound on the physical interpretation of each pressure, explain how the pressures affect flow rate, diffusion, and rate of expansion, and propose experiments to measure the three pressures. Further, we state the effects of surface charge density and aqueous ions have on these pressures.
