SEISMIC ANALYSIS OF TAILINGS DAM

Abstract

Tailings dams are used to impound waste tailings generated by mining activities. Failure of a tailings dam is hazardous for that region because corrosive and radioactive material in the tailing would then contaminate the surrounding environment. The tailings material is a fine grind of sizes similar to clay particles however they behave as cohesionless material and thus are very likely to liquefy under earthquake conditions. Stability of a tailings dam needs to be checked under earthquake loading. The tailings dam under consideration is a zoned dam raised in six stages using the center line method and having three different types of fill materials. The zones, from upstream to downstream, consisted of (i) impervious material (ii) compacted tailings and (iii) pervious random fill. An inclined chimney drain and a connecting horizontal filter are provided to keep most of the dam section on the downstream side dry. The main objective of this study is to perform static and pseudo-static analyses by the Finite Element Method (FEM) using the Strength Reduction Technique and comparing the results with those from various Limit Equilibrium Methods (LEM) such as Bishop Simplified, Janbu Simplified, Janbu Corrected, Spencer, Corps of Engineers-1, Corps of Engineers-2, Lowe Karafiath and Morgenstern Price, considering both circular and non-circular failure surfaces. Finite element analyses have been performed using the geotechnical software PHASE-2, while Limit equilibrium analyses has been performed using geotechnical software SLIDE. The results are presented in the form of normalized plots for the following cases: (i) Stagewise (With Tailings) (ii) Stagewise (Without Tailings) (iii) Considering circular failure surface (iv) Considering non-circular failure surfaces.