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

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.