Transitioning from the funicular to the pendular regime in granular soils

The simulation of granular soils partially saturated by two immiscible fluids – say, water and air – has long been restricted to the so-called ‘pendular regime’, in which the wetting phase (i.e. water in air/water systems) is discontinuous and its presence is restricted to bridges connecting grain pairs. In this work the pendular model is combined with the recently developed two-phase pore-scale finite volumes (2PFV) method for the first time in order to simulate complete drainage from a saturated state to a residual pendular state. The contribution of pendular bridges in terms of water retention and induced internal stress is examined. It is shown that although the presence of a bridge does not significantly affect the soil water retention curve, its induced stress indeed plays a major role in the capillary effects for low saturation (lower than 0·10).