Authors: Brown, B; Gillani, I
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Abstract:
Completing slope stability analyses using the correct methodology and correct strength characterisation for different failure modes is essential for managing the hazards associated with tailings storage facilities. Incorrect assumptions in the input to a slope stability program can provide highly precise but fundamentally incorrect Factors of Safety with significant safety and financial implications. Recent tailings dam failures, especially Mount Polley in Canada, and possibly Samarco in Brazil, have indicated that the failures are related to undrained shearing. In this case the pore water pressures that control the shear strength are not the ones that exist in situ before failure but the ones that are generated during the failure. This is unfortunately not well understood by many geotechnical engineers. Inappropriate use of drained analyses, inaccurate estimation of in situ effective stress in the application of the undrained strength analysis approach, failure to properly apply the SHANSEP technique for over and under consolidated clays, not capping the undrained strength at the drained strength and using linear strength envelopes to model rockfill are some of the other common problems encountered in slope stability analyses. This paper illustrates how these incorrect assumptions regarding material behaviour can significantly affect the estimation of embankment stability. Examples, comparing stability assessments carried out with incorrect and correct methodologies, are presented to highlight the differences.

Keywords: tailings, dams, slopes, slope stability, shear strength

Citation:
Brown, B & Gillani, I 2016, 'Common errors in the slope stability analyses of tailings dams', in PM Dight (ed.), Proceedings of the First Asia Pacific Slope Stability in Mining Conference, Australian Centre for Geomechanics, Perth, pp. 545-556.

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