Considerations for using critical state soil mechanics based constitutive models for capturing static liquefaction failure of tailings dams

Recent disastrous tailings dam failures have heightened public concerns about the safety of these structures. Typically, tailings are disposed of as a slurry in a loosely saturated state, making them susceptible to static liquefaction. The widely used limit equilibrium method for analysing tailings dams may overlook potential failures and is incapable of simulating static-liquefaction-type dam failures. This paper presents simulations of the initiation of progressive failure within a finite element framework, using a well-described tailings dam in Brazil as a basis. Three different constitutive models (Hardening Soil, SANISAND2004, and NorSand) were employed to demonstrate a numerical modelling procedure for simulating tailings dam static liquefaction and a practical approach to numerically account for the effects of fines content in slime layers. Models that incorporate the state parameter (psi) as an integral part can realistically depict the loss of strength in loose granular materials during a liquefaction process. Stress-strain paths of representative points in critical zones of the studied tailings dam indicate localized shear deformations that lead to progressive failure due to static liquefaction.