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Seismic Safety of Upstream Tailings Dams : A Risk-Informed Case

Tailings and Mine Waste Conference (2023 : Vancouver, B.C.); University of British Columbia. Norman B. Keevil Institute of Mining Engineering

Emerging global standards such as the GISTM (Global Industry Standard on Tailings Management) center around risk management practices to protect people and the environment. However, many questions remain on how to address zero risk, how to quantify risk, and how compliance with the standards will be achieved and audited. This is particularly true for tailings facilities built by the method of upstream construction in high seismic regions and in a time when an accepted standard was not available, or the upstream construction was not prohibited in some countries. This paper presents the seismic safety evaluation results of a representative existing upstream tailings facility in the closure phase and some of the existing methods for retrofitting it. The paper introduces the annual probability of occurrence of extreme seismic ground motions and how these influence the current prediction of tailings dam instability. Uncertainties to consider in the choice of a seismic design value are presented, as well as criteria for selecting acceleration time histories compatible with a seismic hazard level. In addition, the paper comments on the use of a log-normal probability density function for selecting a range of liquefied shear strength ratios in a transparent way for analysis and retrofitting of upstream tailings deposits. The paper covers in an integrated approach the performance of a typical upstream tailings facility from the component to the tailings system-wide level to illustrate the propagation of seismic liquefaction and failure. Results of a quantitative stability risk assessment, with and without retrofitting, are described to highlight its use as a decision-making tool to manage residual risks.

Text

2023-12-08

Attribution-NoDerivatives 4.0 International

http://hdl.handle.net/2429/86819

Unreviewed

http://creativecommons.org/licenses/by-nd/4.0/