Three‐dimensional Shear Strength Prediction of Unsaturated Soil Based on a Novel Soil‐water Characteristic Curve (SWCC) Model

ABSTRACT The study of water retention and strength characteristics in unsaturated soils is an underexplored topic yet significant challenge in geotechnical engineering. This paper proposes a simplified computational model for the soil‐water characteristic curve (SWCC), incorporating the novel proposed void optimization parameters l 1 and l 2 . This model can predict SWCC under various initial void ratios and is applicable across a wide suction range. Additionally, we suggest an adjustment parameter m , which can reflect soil type, and then develop a three‐dimensional strength criterion for unsaturated soil. The strength criterion inherently allows for three expansion trends of the failure surface as the matrix suction s increases: parallel, outward non‐parallel, and inward non‐parallel. Furthermore, based on the novel SWCC model, a predictive formula for the shear strength q f of unsaturated soils is established. This formula is then applied to accurately estimate the strength of unsaturated soils under drained true triaxial conditions.