Physical-statistical model for estimation of hysteresis of soil-water characteristic curve

The hysteresis phenomenon is commonly observed associated with both the soil-water characteristic curve (SWCC) and the hydraulic conductivity function (HCF) of unsaturated soils. In other words, the volumetric water content and the hydraulic conductivity in the wetting process are commonly different than those in the drying processs. There are various empirical models avaiable for the estimation of the hysteresis of SWCC, and the estimated results by those empirical models are much dependent on the model parameters, which have weak physical meanings. A matrix is adopted for the simulation of the improved capillary model, and the water amount in the tubes with different radii is calculated using the statistical method. The water contents corresponding to different suction levels in the drying and wetting processes are obtained by summation of the water amount in the tubes with different radii. In the wetting process, the effects of the factors (such as the entrapped air, ink-bottle effect and the "rain-drop" effect) on the hysteresis of SWCC are quantified. The SWCC data collected from the literatures published both at home and abroad are adopted for the verification. It is observed that the predicted results by the proposed model have good agreement with the experimental data from the literatures.