Comparison of freezing and hydration characteristics for porous media

The processes of freezing–thawing and hydration–dissociation change the content of liquid water that coexists with ice or hydrate in porous media, such as frozen soils and hydrate‐bearing sediments, changing their physicomechanical properties. In this study, a generalized phase equilibrium equation is presented for both frozen soils and hydrate‐bearing sediments by considering the capillary and osmotic pressures. The liquid water content is related to temperature depression, plotted as the soil freezing characteristic curve (SFCC) or the soil hydration characteristic curve (SHCC), by combining the generalized phase equilibrium equation and the soil‐water characteristic curve (SWCC). From the SFCC or the SHCC, the phase equilibrium surface can be calculated in the space of temperature, pressure, and liquid water content. The proposed generalized phase equilibrium equation and the model of SFCC and SHCC can help to estimate the physicomechanical properties that depend on the fraction of the liquid or solid phase in porous media. Finally, the SHCC is employed to analyze the dissociation of hydrate‐bearing sediments using various methods.