Abstract：Soil-water characteristic is one of important hydraulic parameters for geotechnical media. A soil-water characteristic curve(SWCC) represents a relationship between moisture content and matrix suction，and this relationship is generally nonmonotonic，showing hysteretic behaviors under drying-wetting cyclic paths. When a geological material experiences drying-wetting cycles，part of air phase will be trapped as air bubbles in the pore space. Such air entrapment has significant influences on the soil-water characteristics and the permeability of the porous media. Based on the internal-variable theory of capillary hysteresis and an empirical model of soil-water characteristics，a mathematical model is developed that can be used to describe the soil-water characteristics of geotechnical media experiencing arbitrary drying-wetting paths. In particular，the effect of air entrapment is fully taken into account in this model. Provided that the hysteresis loop is given，the proposed model includes only one material parameter，which can be determined by using any first-order scanning curve(or one datum point on the curve). The model is numerically solved using the forward Euler iterative scheme. Numerical simulations are compared with the experimental data of the soil-water characteristic curves for four different types of geotechnical media，i.e. a silt loam，sintered glass beads，a limestone and a dolomite. It is found that the computational results agree very well with the measured data；and it is shown that the proposed model is capable of describing the soil-water characteristic curves of geotechnical media experiencing complicated drying-wetting paths.
