A modified Kozeny-Carman equation for predicting saturated hydraulic conductivity of compacted bentonite in confined condition

Kozeny-Carman (KC) equation is a well-known relation between hydraulic conductivity and pore properties in porous material. The applications of KC equation to predicting saturated hydraulic conductivities of sands and non-expansive soils are well documented. However, KC equation is incapable of predicting saturated hydraulic conductivity of expansive soil (e.g. bentonite) well. Based on a new dual-pore system, this study modified KC equation for improving the prediction of saturated hydraulic conductivities of bentonites. In this study, an assumption that inter-layer space (micropore) has limited effect on fluid flow performance of compacted bentonite was adopted. The critical parameters including total porosity and total tortuosity in conventional KC equation were replaced by macroporosity and tortuosity of macropore, respectively. Macroporosity and microporosity were calculated by basal spacing of compacted bentonite, which was estimated by assuming that specific surface area is changeable during saturation process. A comprehensive comparison of bentonite's saturated hydraulic conductivity predictions, including modified KC equation proposed in this study, conventional KC equation, and prediction method based on diffuse double layer (DDL) theory, was carried out. It was found that the predicted saturated hydraulic conductivity of bentonites calculated using modified KC equation fitted the experimental data better than others to a certain extent. (C) 2022 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. All rights reserved.

Automated summary

The Kozeny-Carman (KC) equation is a well-known relation between hydraulic conductivity and pore properties in porous material. This study proposes a modified KC equation based on a new dual-pore system to improve the prediction of saturated hydraulic conductivities of bentonites. The modification replaces critical parameters in the conventional KC equation with macroporosity and tortuosity of macropore, and calculates them based on the basal spacing of compacted bentonite. Compared with conventional KC equation and prediction method based on diffuse double layer (DDL) theory, the modified KC equation shows better fitting to the experimental data of bentonites' saturated hydraulic conductivity to a certain extent.