Unsaturated flow in hydrating porous media with application to cemented mine backfill

Abstract

Unsaturated flow in hydrating porous media is pertinent to several engineering applications, including underground and surface use of cemented tailings. Proper description and modelling of flow is complicated by changes in material properties due to hydration as well as by the generation of suction by the net consumption of water volume by hydration, variously termed chemical shrinkage or self-desiccation. It is necessary to define changes in hydraulic properties with time; for instance, the soil-water characteristic curve (SWCC) is not unique in time in addition to being path (drying versus wetting) dependent. To address this problem, a theory for modelling unsaturated flow in hydrating materials is introduced. The theory deconstructs the SWCC into a pore-size distribution, which changes with time as hydration occurs, and the water content, which is a variable that must be tracked with space and time. Matric suction depends on the time-dependent SWCC and the water content variable. The theory is applied to a multi-layer deposition experiment performed in a column, and shows reasonable results.