Dynamic Numerical Evaluation of the Effect of the Retained Tailings on the Performance of a Tailings Impoundment

The seismic performance of a tailings impoundment in western Quebec was evaluated using dynamic numerical analysis. The perimeter dike forming the impoundment is composed of waste rock (rockfill) and is up to 24 meters high. Foundation conditions vary from bedrock to 7 m of silty clay and till over bedrock. Multiple scenarios were simulated to determine the influence of subsurface conditions, the contents of the impoundment (tailings, water or empty) as well as the intensity and the frequency content of the ground motion. The responses of the tailings (i.e. CSR, r(u), and liquefaction) and of the dike (i.e. PGA, deformation) were used to evaluate the performance of the impoundment. The performance of the impoundment was found to be satisfactory for all the scenarios considered. However, the contents, subsurface conditions, and earthquake loading were found to have appreciable effects on the response of the tailings impoundment.