Effects of Adsorbed Water Layer in Predicting Saturated Hydraulic Conductivity for Clays with Kozeny–Carman Equation

Abstract

Saturated hydraulic conductivity for clays predicted using the conventional Kozeny–Carman equation is scalar and found to diverge significantly from measured values. The divergence is consistent and systematic requiring a mathematical derivation of the formula using first principles. The incorporation of the physical characteristics of the adsorbed water layer surrounding a clay particle results in a generalized Kozeny–Carman equation with two new parameters. The porosity correction factor gives the effective porosity taking into account the thickness of the adsorbed water layer and the mass specific surface area of the clay. The second parameter is shown to depend on the interparticle contact area and the interparticle contact stress. The ability of the proposed physically based generalized Kozeny–Carman equation to explain the results from some of the published laboratory permeability tests is tested. The paper results in a new theoretical framework to model changes in saturated hydraulic conductivity in clays where the soil profile is compacting as a result of changes in pore-water pressure and or externally applied loads.