Predicting water film thickness in unsaturated soils considering irregular grain shapes Available to Purchase

Water films on solid surfaces play a crucial role in hydraulic conductivity, fluid flow, and chemical transport in unsaturated granular materials. Existing models are limited to idealised geometries, such as flat surfaces, spherical grains, and spherical pores, whereas natural granular materials typically consist of irregular grains with surfaces that include convex, concave, and planar regions. Consequently, these models may not capture the variation in water film thickness on the surface of irregular grains. To address this limitation, a new model is proposed based on Derjaguin–Landau–Verwey–Overbeek theory, incorporating the effect of solid surface curvature. The model’s predictions show good agreement with experimental data. When the relative humidity (RH) exceeds 95%, the water film thickness increases rapidly with increasing RH. When RH > 99%, the effects of solid surface curvature and temperature become significant. At saturated vapour pressure, a decrease in solid surface curvature and an increase in temperature lead to an increase in water film thickness, while an increase in the ion valence of counterions reduces water film thickness. Model predictions also indicate that, compared with larger pores, smaller pores can be filled with water at a lower RH due to adsorption, which is consistent with experimental observations.