Concept of effective suction for describing hysteresis of multiphase pressure–saturation relationship in porous media

Abstract

A novel approach is proposed to capture the hysteresis of the suction - degree of saturation (ψ-S) relationship of three–phase fluids in porous media. Effective suction ψ′ is defined such that it incorporates the delay in the variation in the degrees of saturation due to the hysteresis, with its movement in a closed domain of suction space. This effective suction space domain represents the possible range in effective suction in which matric suction ψ is always located at the center of the locus. The incremental change in matric suction determines the movement of the effective suction in the suction space. This effective suction is incorporated into the unique (ψ-S) relationship previously defined by van Genuchten (1980) to obtain the delayed variation in the degrees of saturation caused by the hysteresis along the wetting and drying scanning paths. By incorporating the effective suction into the conventional ψ-S relationship, the hysteretic characteristics of the saturation of air, NAPL, and water are described for both 2–phase and 3–phase systems. Realistic soil behavior is further captured through a simulation of the vertical soil profiles in the presence of hysteresis by incorporating the proposed concept into a 3–phase system.