Authors: Cancino, CF; Silva, R; Giraud, C

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DOI https://doi.org/10.36487/ACG_repo/2135_0.03

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Cancino, CF, Silva, R & Giraud, C 2021, 'Numerical assessment of an overall instability at Bajo de la Alumbrera Mine', in PM Dight (ed.), SSIM 2021: Second International Slope Stability in Mining, Australian Centre for Geomechanics, Perth, pp. 27-36, https://doi.org/10.36487/ACG_repo/2135_0.03

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Abstract:
In May of 2017, an instability at overall scale occurred in the southwestern wall at Bajo de la Alumbrera mine. A cessation of mining followed due to unstable material reaching the pushback planned to mine the ore located at the bottom of the open pit. This paper describes the numerical modelling analyses developed to back-analyse the instability and to study the options to continue mining the remaining ore at the bottom of the open pit. In 2012, Itasca carried out a predictive analysis using numerical modelling (3DEC) which suggested that a large-scale instability was possible in the area. A new numerical model was developed in 2017 to back-analyse the instability in terms of Factor of Safety (FS) contours, and this achieved a good match with field observations. To continue mining the pushback below while meeting the acceptance criterion of the slope design, defined by an FS ≥ 1.2 at inter-ramp scale, sequential excavations were simulated from top to bottom. The model showed that an excavation 204 m high would be required to meet the acceptance criterion to resume mining in Pushback-12.

Keywords: slope stability, back-analysis, numerical modelling

References:
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Itasca Consulting Group, Inc. 2016a, 3DEC — Three-Dimensional Distinct Element Code, version 5.2, Itasca, Minneapolis.
Itasca Consulting Group, Inc. 2016b, Griddle, version 1.0, Itasca, Minneapolis.
Silva, R & Gomez, P 2015, Towards a Mechanically Based Definition of the Disturbance Factor Using the Slope Model Lattice Code, IOS Press, Buenos Aires, pp. 3–10.
Zienkiewicz, O, Humpheson, C & Lewis, R 1975, ‘Associted and non-associated visco-plasticity and plasticity in soil mechanics’, Géotechnique, vol. 25, issue 4, pp. 671–689.




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