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Case Study : Geotechnical Studies to Improve Understanding of Material Parameters and Address Changes in Stability Requirements, Granny Smith Gold Mine, Western Australia

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

Upstream construction relies on the integrity of the tailings for stability. As such, while this construction method has been successfully used for decades, these designs require greater ongoing scrutiny. The Tailings Storage Facility (TSF) complex at the Granny Smith mine comprises three cells and was designed preANCOLD guidelines with minimum allowable factors of safety for static conditions of 1.3. Previous investigations on Cell 1 identified horizontal layering resulting from deposition of primary and oxide ore tailings. The oxide layers were located beneath the top elevation of and adjacent to the original starter embankment, covering approximately 50% of the TSF floor area. The Engineer of Record assessed that the oxide tailings would likely exhibit brittle behaviour and very low post-peak undrained shear strength ratios. As a result, preliminary stability assessments yielded factors of safety below 1.5 under undrained static loading conditions. Deposition into Cell 1 was therefore suspended and deposition diverted to Cell 3. This paper presents the approach followed to confirm the stability of the cells and to optimize the geometry of the toe buttress (including geotechnical investigations, laboratory testing, and deformation modelling). The dynamic deformation modelling completed to predict the deformation of the TSF under the seismic design load and to check the propensity of the low predicted post-seismic strengths to trigger under the seismic design event is discussed. The paper highlights the importance of material characterization, particularly for upstream constructed dams, and that brittle materials are a special case that requires conservative design.

Text

2023-12-08

Attribution-NonCommercialNoDerivatives 4.0 International

http://hdl.handle.net/2429/86803

Unreviewed

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