Simple Approaches for Modeling Hysteretic Soil Water Retention Behavior

Abstract

Hysteretic soil water retention behavior is the key information required for interpreting and predicting the hydromechanical responses of unsaturated soils during drying and wetting processes. For this reason, models capable of describing such behavior are valuable in the development of constitutive relationships for unsaturated soils. In this paper, a model is proposed for predicting the main and scanning soil-water characteristic curves (SWCCs) (degree of saturation-suction relationships). In addition, the model is extended to another model for predicting the main and scanning soil-water characteristic surfaces (SWCSs) (degree of saturation-void ratio-suction relationships). The proposed models need one extra parameter (q for SWCC or q′ for SWCS), in addition to parameters required for conventional SWCC or SWCS models. The major advantages of the proposed models are as follows: (1) measurements of the main drying and wetting curves or surfaces are the only information required to calibrate all model parameters, (2) model predictions allow a smooth transition from scanning curves or surfaces to the main curves or surfaces, and (3) calibration associated with the parameter q or q′ can be further refined using measurements of scanning curves or surfaces to improve the precision of the predictions. The performance of both proposed models was validated against measurements of six different soils ranging from sands to clayey soils. Reasonable agreements between predictions of the proposed models and experimental results are achieved for all soils investigated in this study.