Efficient approach in modeling the shear strength of unsaturated soil using soil water retention curve

Currently, there are debates on the relationship between the effective stress and shear strength of unsaturated soils. Thus, it is imperative to present an efficient method that could contribute to the existing knowledge in this aspect while ensuring an easy and fast operation. In this study, a novel approach for modeling the shear strength of unsaturated soils using soil water retention curve (SWRC) is proposed. The method considers a coherent thermodynamic expression of Bishop’s effective stress parameter χ and a physical model of the SWRC that depends only on one parameter. First, an expression for unsaturated effective stress was obtained. The starting point to develop the shear strength equation was then determined. The obtained equation can estimate Bishop’s parameter for unsaturated soil using only the SWRC and the relationship between unsaturated shear strength and soil suction. A sensitivity analysis and comparison with other methods that obtained different parameter expressions were also provided. The results showed that the results obtained from the proposed model fits with experimental data, indicating its applicability in studying the average behavior of unsaturated sands.