A new model for predicting the hydraulic conductivity of unsaturated porous media

TLDR

The model builds on the Childs and Collis‑George (1950) framework, modifying the pore‑sequence conductivity assumption to account for larger pore sections. The authors propose a simple analytic model that predicts unsaturated hydraulic conductivity curves from the moisture‑content/ capillary‑head relationship and the saturated conductivity. They derive a computational method to estimate residual water content and extrapolate the moisture‑content/ capillary‑head curve, then compare the resulting model against Averjanov, Wyllie & Gardner, and Millington‑Quirk using data from 45 soils. The new model shows better agreement with observed data than the existing practical models.

Abstract

A simple analytic model is proposed which predicts the unsaturated hydraulic conductivity curves by using the moisture content‐capillary head curve and the measured value of the hydraulic conductivity at saturation. It is similar to the Childs and Collis‐George (1950) model but uses a modified assumption concerning the hydraulic conductivity of the pore sequence in order to take into account the effect of the larger pore section. A computational method is derived for the determination of the residual water content and for the extrapolation of the water content‐capillary head curve as measured in a limited range. The proposed model is compared with the existing practical models of Averjanov (1950), Wyllie and Gardner (1958), and Millington and Quirk (1961) on the basis of the measured data of 45 soils. It seems that the new model is in better agreement with observations.