Three-dimensional Slope Stability Assessments For A Large Translational Landslide

The factor of safety is often used to assess the stability of a slope. SVSlope is one of the software to calculate the factor of safety for both two and three-dimensional scenarios by using several Limit Equilibrium Methods options, including Morgenstern-Price, Spencer, Janbu and Bishop methods. Other geotechnical software such as FLAC and Plaxis use the Strength Reduction Method to calculate the factor of safety. When the authors recently analysed a large-scale translational landslide involving a large flat basal slip surface, it was found that different calculation methods for two-dimensional sections predicted a significantly different factor of safety for the same shear strength parameters. It became challenging for the design team to agree on the slope performance assessment from the various methodologies and the limitations of the two-dimensional analysis to massive translational landslides. The purpose of this paper is to investigate the stability of a typical three-dimensional large-scale translational landslide by applying different methods and comparing the differences between them. A typical large-scale translational landslide was modelled based on an actual project. It was analysed using 2D/3D SVSlope with different Limit Equilibrium Methods and FLAC3D with the Strength Reduction Method. The differences in the factor of safety from the various methods are presented. This paper highlights the strengths and weaknesses of a different factor of safety methods for a typical two and three-dimensional large translational landslide.