A theoretical model of freezing water characteristic curve of saturated sandstone considering capillarity and adsorption.

This article focuses on investigating the freezing characteristics of pore water in saturated sandstones, emphasizing the effects of pore structure and water–mineral interactions. Using x-ray diffraction (XRD), nitrogen gas adsorption (N2GA), and nuclear magnetic resonance (NMR) techniques, the study analyzes mineral composition, pore size distribution, and unfrozen water content in three sandstone types with varying lithologies and clay mineral contents. A theoretical model integrating capillary water and adsorbed water freezing behaviors is developed, incorporating fractal theory and statistical thermodynamics, and validated against experimental data. Results indicate that higher hydrophilic clay content, particularly montmorillonite, increases NMR surface relaxivity, adsorbed water content, and water film thickness, leading to slower freezing rates and distinct freezing behaviors despite similar pore volume distributions. Compared to existing empirical and theoretical models, the proposed model more accurately describes the relationship between temperature and unfrozen water content in different sandstones, though further validation and consideration of freezing-induced deformation and premelting effects are recommended.