Abstract
Slope failures often occur during soil wetting, yet most analyses rely solely on drying soil-water characteristic curve (SWCC), leading to results that do not reflect field conditions. This study develops a mathematical model to estimate bimodal permeability functions under both soil drying and wetting, and to investigate the influence of hysteresis on the stability of dual-porosity soil slopes. Analyses were performed under three scenarios: using only the drying SWCC, using only the wetting SWCC, and using both the drying and wetting SWCCs. Rainfall patterns were chosen according to records of rainfall intensities in central Asia. Drying and wetting SWCCs were tested in the laboratory, while the shear strength of unsaturated soil was a function of matric suction linked to the SWCC. Comparing the results of analyses using the three scenarios indicates that ignoring hysteresis provides an ‘overly conservative’ factor of safety, with differences of up to 67%. Thus, using the relevant SWCC to model drying and wetting processes in slope stability analyses is important to avoid unsafe or excessively conservative designs.