Numerical modelling of hydraulic hysteresis in unsaturated soil covers

This paper aims to study the effect of hydraulic hysteresis on seepage in unsaturated soils. A hysteretic water retention model is incorporated into the Richards equation to describe water flow in unsaturated soils. A linear scanning curve is used to describe the hydraulic behaviour within the main hysteretic loop of the water retention curves. The proposed approach is implemented into a finite difference code, and is then used to analyse seepage in soil covers on wastes. An infiltration test on a two-layered soil column is simulated with the proposed hysteretic model. Results show that hydraulic hysteresis plays a crucial role in the seepage analysis of unsaturated soils subjected to cyclic drying and wetting. The hysteretic model is suggested for use in the design and evaluation of the hydraulic performance of soil covers.