Modifying Kozeny-Carman equation for evaluating saturated hydraulic conductivity in clay with adsorbed water layers

摘要

Due to the importance of saturated hydraulic conductivity values in simulating flow phenomenon in saturated soil systems and inherent variability in hydraulic conductivity data for different type of soils and difficulties of collecting reliable representative samples, engineering and earth science communities have for long sought alternative methods of estimating hydraulic conductivity values from physical properties of the soil mass and fluid. A widely used relationship between the saturated hydraulic conductivity and the physical properties of the fluid and the soil mass is based on the 'hydraulic radius theory' and referred to as the Kozeny-Carman (K-C) equation. The current formulation of the K-C equation implicitly assumes a negligible inter-particle contact area. The K-C equation has been shown to hold true for sand, but consistently fails when applied to clays. The reasons for the failure of K-C equations when applied to clays, despite various efforts, have not yet been resolved. The presence of adsorbed water layer has been shown to contradict the assumption of negligible contact area in clay. This paper develops a modified K-C equation accounting for effects of the adsorbed water layer. The presence of adsorbed water is shown to affect the porosity values as well as the inter-particle contact areas in clays. The modified K-C equation is tested against published laboratory test results. The use of the modified K-C equation taking into account the effects of adsorbed water layer on the porosity values improves the predictive capability of the Kozeny-Carman equation.