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Long-term Evolution of the Phreatic Surface in a Tailings Dam following Closure

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

Following mine closure, tailings dams remain on the site, eventually becoming part of the landscape. Historically, it was common practice to design these structures with consideration of failure modes that could occur during the mine’s active life. This is problematic as the life of the tailings dam is expected to far exceed the life of the mine. Further, the importance of reclamation and decommissioning through the processes of sustainable mining practice is a relatively recent development in the mining industry. Despite this, there is limited information regarding how a tailings dam ages in perpetuity. The evolution of the phreatic surface in a tailings dam is a potential area of uncertainty associated with the closure phase of a tailings dam. Changes in the phreatic surface can act as a trigger for failure of different elements in a tailings dam following closure. Consequently, understanding the long-term evolution of the phreatic surface in a tailings dam is essential to the process of reclamation and closure and is an integral component of the long-term risk management of tailings dams. This paper aims to evaluate this commonly made assumption through the analysis of the evolution of the phreatic surface of an oil sands tailings dam case study in Alberta, Canada in response to different scenarios, including: drain failure, formation of ponds on the reclamation surface, and climate change. The seepage modelling demonstrated under certain scenarios, drains failing and ponds forming on the reclamation surface had the potential to cause a rise in the phreatic surface in the case study dam. Longterm seepage modelling can also be used to help guide monitoring and maintenance plans for closure works, which can be anchored back to the observational method or an adaptive management framework.

Text

2023-12-08

Attribution-ShareAlike 4.0 International

http://hdl.handle.net/2429/86792

Unreviewed

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