Prediction of the hydraulic conductivity function for unsaturated soils over the entire suction range

The hydraulic conductivity function (HCF) refers to in this paper is the variation of hydraulic conductivity over the entire suction range from 0 to 10⁶ kPa. Most of the available HCF models in the literature are derived based on capillary theory and have limitations in the explanation of HCF in the high suction range. Recently, several models have been proposed for accounting for the thin film flow dominated by the adsorbed water in the high suction range. However, these models require measured HCF data for describing the thin film flow, which is time-consuming. In this study, a mathematically continuous and simple model is proposed for predicting the HCF. The model has physically meaningful parameters for predicting the HCF. In this model, the residual suction estimated from the soil-water characteristic curve (SWCC) is used to distinguish the capillary and adsorption-dominated regions, and a correction operator that considers the thin film flow is introduced. The performance of the model was validated using the measured and published experimental data for various soils. In addition, the proposed model is successfully applied in a numerical investigation of the hydraulic behavior of a capillary barrier system, highlighting the role of the thin film flow.