A contact angle-dependent hysteresis model for soilwater retention behaviour
Hysteresis is common in soilwater phenomena, and the soilwater retention relationship is not a one-to-one relationship between the effective degree of saturation and the matric suction. Existing theoretical soilwater retention models are usually derived by applying a capillary law that does not depend on the contact angle to the cumulative distribution function of soil pores. These theoretical models usually contain equations only for the main drying and wetting branches, so additional empirical scanning laws are needed to model hysteresis behaviour between these branches. This paper proposes a contact angle-dependent model in incremental form to reproduce soilwater hysteresis behaviour. The change in suction during scanning wetting and drying processes leads to a change in both the effective degree of saturation and the liquidsolid contact angle. An allocation proportion function is proposed to divide suction increments into two parts, one of which is allocated to the change in the effective degree of saturation and the other consumed by changing the contact angle. The proposed hysteresis model contains only four parameters that can be conveniently calibrated by the main drying branch and a scanning wetting curve. Test results are included to validate the proposed hysteresis model.
contact angle hysteresis suction soilwater characteristic curve (swcc)