It is common practice to deposit tailings hydraulically into upstream-raised tailings storage facilities (TSF) whose stability depends on the strength of the tailings themselves. Due to the tailings deposition method, upstream-raised tailings dams are vulnerable to flow liquefaction.
As a result of recent tailings dam failures (Cadia, Samarco, Brumandhino), the current practice of stability assessment of tailings dams is to assume that all materials susceptible to flow liquefaction will liquefy. It is recognized that evaluating all possible triggers for flow liquefaction is not practically feasible, and that triggering analyses are not frequent at the stage of the design process of a new dam.
This work presents a procedure for assessing the liquefaction vulnerability of tailings dams system (including the retention structure, retained materials and foundation). The proposed procedure tests the system resilience by employing a set of deteriorating events that may result in the instability of the system, rather than identifying plausible failure scenarios. The procedure employs a numerical deformation model to reproduce the conditions of a dam after construction and applies a set of actions aimed at mobilizing the shear strength of the tailings under undrained loading conditions to check for progressive failure and instability. The procedure was tested by applying it to the well-documented Fundão Dam failure.
Session: Tailings & Dams
