Comparative analysis and parameter determination method of shear strength models for unsaturated clayey soils

Due to the great variation of strength of unsaturated soils with matric suction, the numerous influence factors and the complex mechanism, the worldwide scholars have proposed various unsaturated strength models, but no consensus has been reached. In order to obtain a universal model that can describe the nonlinear variation of strength of the unsaturated soils over a wide suction range, the existing unsaturated strength models are systematically summarized. Also, their application effects are compared with the data in the literature. The research results show that: (1) The fitting models are superior to the prediction ones; (2) Among the fitting models, the hyperbolic models are the best in predicting the shear strength of clayey soils. Furthermore, the parameter determination method for the hyperbolic model is analyzed. It is found that: (1) Two parameters of the hyperbolic model can be accurately obtained by measuring the unsaturated strength at three saturation levels. (2) It is recommended to measure the shear strength of soil samples within the saturation degrees of 1, 0.7 to 0.4 and 0.1 to 0. The determination method for the hyperbolic parameters is proposed. The parameters require a few of experimental data, which can obtain a relatively accurate evolution law of the strength in the full suction range. It is of great significance to the study on the mechanical behaviour and engineering application of unsaturated soils.