Executive Summary : | Unsaturated hydraulic conductivity (k) and soil-water retention curve (SWRC) are crucial for numerical modeling of soil flow and transport phenomena. These properties are essential in geotechnical, geoenvironmental, and agricultural applications, such as hazardous waste containment, rainfall-induced landslides analysis, seepage estimation, and water retention capacity determination. Unsaturated hydraulic conductivity depends on the pore structure, fluid properties, and soil fluid content. Experimental methods for measuring these properties are costly, time-consuming, and challenging due to the large variance. Therefore, indirect methods are encouraged. These methods are classified into empirical, macroscopic, and statistical models. Empirical models require large amounts of experimental data and often provide parameters without theoretical basis. Macroscopic models are semi-empirical and neglect the effect of pore size distribution on hydraulic conductivity. Statistical models are more general and superior but struggle to represent soil pore structure and flow routes properly. SWCC attracts indirect methods or pedo-transfer functions (PTF) and can be divided into regression analysis, estimation of soil parameters, and physico-empirical models. However, these methods are highly sensitive to empirical fitting parameters. The proposed research aims to develop a numerical scheme using the discrete element method that models a practical and rational pore structure encompassing coarse and fine-grained soil. This pore structure will accurately capture unsaturated hydraulic conductivity and water retention characteristics along the drying and wetting path, accounting for appropriate pore-scale mechanisms without time-consuming and expensive experiments and fitting parameters. |