Compaction effect on the gas diffusion coefficient in soils

This study investigated the effects of compaction in four soils. The experiment involved equilibrating bulk loose soil to a known matric potential in a pressure chamber, compressing the equilibrated moist soil in metal cores at a given applied stress, and measuring the concentration of N₂ diffusing through these cores into a diffusion chamber. The diffusion coefficient of N₂ varied exponentially as a function of air-filled porosity and was nearly the same function for all four soils. A model for predicting the diffusion coefficient of gases in soils based on the diffusion coefficient of individual soil constituents overpredicted the coefficient for all four soils. A reduction factor suggested in the literature to account for blocked air slightly improved predictions. -from Authors