A grain scale model to predict retention properties of unsaturated soils

The soil water retention curve (SWRC) is a fundamental relationship in unsaturated soils. Retention properties of unsaturated soils are important for many practical applications. Mechanical and hydraulic properties of soil in unsaturated state depend on the soil saturation. Therefore, knowledge of the retention properties of unsaturated soils and determination of various factors affecting the soil water retention curves are of considerable importance. Experimental methods to measure SWRC are time consuming and costly. To model soil water retention curves, various empirical and physically-based models have been introduced in the literature. There are two types of physically based models which have been recently proposed that capture two phase flow in unsaturated poromechanics and petroleum engineering, namely: pore scale and grain scale models. Grain scale models can directly consider the presence of grains of different sizes in the sample whereas pore scale models require visualization or estimation of the pore geometry. In this study, a grain scale model is employed for determining soil water retention properties using the discrete element technique and capillary invasion algorithm.