A modification for capillary hysteresis internal variable model of unsaturated soils

Soil-water characteristic curve(SWCC) describes the relationship between suction and volumetric water content of unsaturated soil which are not one-to-one correspondence. This curve performs hydraulic hysteresis during arbitrary drying-wetting suction changes are applied to the material. Based on capillary hysteresis internal variable model and conventional soil-water characteristics theory of unsaturated soils, a modified model which can simulate soil-water characteristic relationship during arbitrary suction changes is proposed. This model increases one parameter compared with the capillary hysteresis internal variable model, which describes the reversible changes of water content and ensures the slope of scanning curve not to be infinite when scanning curves approach the boundary of SWCC. The modified model retains the precision of the capillary hysteresis internal variable model simultaneously. Compared with experimental results in references, this model is able to simulate soil-water characteristics relationship of unsaturated soils better than the capillary hysteresis internal variable model. Determination method of the new parameter is also discussed.