Method for predicting unsaturated permeability using basic soil properties

Abstract

Permeability function is one of the key functions in unsaturated soil mechanics, which is often estimated from the soil water characteristic curve (SWCC) of a soil. Mualem’s permeability function which employs Van Genuchten's SWCC function is one of widely used function. However, there are two parameters in the function which need to be determined using test data and in many cases those kind of test data are not available. Empirical equations for estimating two fitting parameters (aD and n) in Mualem’s permeability function from easy to be measured basic soil properties has been proposed, i.e. aD is linked to saturated permeability (ks), and n is determined from the grain size distribution curve of a soil. The proposed method was applied to predict permeability functions of 9 soils (4 from this study and 5 from literature) with which the test data are available. Comparing the predicted and the measured values indicates that the proposed method can result in satisfaction predictions for both drying and wetting paths. It is suggested that the method can provide a first order estimation of permeability function in case there are no test data available.