A Semianalytical Model for Three-Dimensional Stability Analysis of Potentially Rotational Slopes in Unsaturated Soils

Abstract

Stability analysis of slopes subjected to steady infiltration is a hot topic in geotechnical engineering. However, the existing three-dimensional (3D) upper-bound limit analyses of unsaturated rotational slopes failed to take variable strength parameters and hydraulic parameters in space into account. To fill this gap, a semianalytical model is developed to capture the factor of safety (FS) and the critical failure region of unsaturated slopes based on the kinematical approach of limit analysis (KALA). A 3D rotational failure mechanism of unsaturated slopes subjected to steady vertical infiltrations is generated by a “point-by-point” technique, which can readily incorporate spatially variable strength parameters and hydraulic parameters. The work rates are calculated to formulate the objective function of FS, and the critical FS are optimized. The proposed model is validated through comparisons with the existing solutions and numerical solutions in terms of both the FSs and the failure patterns. The combined effects of hydraulic parameters and the size of slopes are investigated. An application to the stability analyses of unsaturated slopes with spatially variable physical parameters demonstrates that the proposed model has the potential to serve as a benchmark for the KALA of unsaturated slopes under complex geological conditions. Generally, the described framework can help geotechnical designers quickly evaluate the stability of unsaturated slopes in the preliminary design phase if the water table elevation is available and the hydraulic and strength parameters have been calibrated.