Comparative stability analysis of tailings dams using limit equilibrium and finite element methods

Abstract

This paper presents a case study of stability assessment conducted on a tailings storage facility divider dam. The stability utilized limit equilibrium (LE) with Slope/W, incorporating various commonly used slip surface searching options, and the finite element method (FEM) with Plaxis2D under static peak and post liquefaction conditions. The results reveal a significant variation in the factor of safety (FoS) obtained from LE (FoSLE), depending on the selected slip surface searching options. Notably, the commonly used searching options in Slope/W can yield significantly higher FoS than those obtained from Plaxis2D. This observation prompted the adoption of the fully specified (FS) searching option in Slope/W, where the critical slip surface was aligned with that determined by Plaxis2D, resulting in comparable results to Plaxis2D. The FoSLE obtained by FS closely approximated FoSFEM, with a difference of 3.4% under static peak and 15.4% under post-liquefaction conditions. The results indicate that certain slip surface searching options in LE may fail to accurately identify the critical slip surface, leading to an overestimation of the FoS for a given geometry. The FEM, on the other hand, can provide valuable insights by identifying potential critical slip surfaces that may not be identified in LE.