Aqueous Diffusion Coefficients in Unsaturated Materials

Abstract

ABSTRACTSimple diffusion coefficients, D(θ), in most unsaturated media were found to be primarily a function of water content and not material characteristics except where the characteristics affect or determine water content. At high water contents, D(θ) gradually declines as water content decreases, from 10−5 cm2/sec at a volumetric water content of about 50% to 10−7 cm2/sec at a volumetric water content of about 5%, followed by a sharp decline as surface water films become thin and discontinuous and pendular water elements become very small, from 10−7 cm2/sec at a volumetric water content of about 5% to 10−9 cm2/sec at a volumetric water content of about 0.5% to 1%.