Authors: Jele, R; Dunn, MJ

Open access courtesy of:

Cite As:
Jele, R & Dunn, MJ 2019, 'Economic significance of geotechnical uncertainties in open pit mines', in J Wesseloo (ed.), Proceedings of the First International Conference on Mining Geomechanical Risk, Australian Centre for Geomechanics, Perth, pp. 111-126.

Download citation as:   ris   bibtex   endnote   text   Zotero


Abstract:
The major cost associated with open pit mine operations is waste stripping. While the steepening of slope angles reduces the stripping ratio, and hence operational costs, it also increases the likelihood of failure. Major slope failures incur significant cost elements including clean-up, disruption to mine operation, and damage to mining equipment and in some cases loss of reserves. Geotechnical engineers are often faced with the difficult task of finding the balance between slope optimisation and acceptable risk related to the likelihood of large slope failures. Technological advancements have allowed for the development of larger and deeper open pit operations, but have also created higher economic impact from potential slope failures. Given that the aim of mining operators is to maximise overall profits, it is surprising that most slope designs are based on deterministic design approaches, and limited attention is given to quantifying uncertainties in the geotechnical model. As most major decisions in the mining industry are made by senior management staff and financial staff, any attempt on linking slope stability analysis results with monetary values would improve the critical communication between geotechnical designers and decision-makers. Using Cowal Gold Mine as a case study, this paper illustrates economic risk caused by geotechnical uncertainties. The geotechnical risk estimate is generally subjective due to geotechnical engineers having to rely on limited data and engineering judgement. Geotechnical risk is compared against economic factors that are often perceived as important variables in mining operations.

Keywords: uncertainty, risk

References:
ARANZ Geo Ltd 2016, Leapfrog, computer software, ARANZ Geo Ltd, Christchurch, http://www.leapfrog3d.com/products/leapfrog-geo
Bieniawski, ZT 1991, ‘In search of a design methodology for rock mechanics’, in Roegiers (ed.), Proceedings of the 32rd US Symposium on Rock Mechanics, A.A. Balkema, Rotterdam, pp. 1027–1036.
Bieniawski, ZT 1992, ‘Principles of engineering design for rock mechanics’, in JR Tillerson and WR Wawersik (eds), Proceedings of the 33rd US Symposium on Rock Mechanics, A.A. Balkema, Rotterdam, pp. 1031–1040.
Call, RD, & Kim, YC 1978, ‘Composite probability of instability for optimizing pit slope design’, in YC Kim (ed.), Proceedings of the 19th US Symposium on Rock Mechanics, American Rock Mechanics Association, Alexandria.
Crouse, R & Wright, S 2015, ‘Cowal gold mine: success in mining through saprolites – a case history’, Mining Engineering, September 2015,
Dunn, MJ 2014, ‘Geotechnical models and data confidence in mining geotechnical design’, Proceedings of the Third Australasian Ground Control in Mining Conference, The Australasian Institute of Mining and Metallurgy, Melbourne, pp. 105–112.
Guest, A & Read, J 2009, ‘Geotechnical model’, in J Read & P Stacey (eds), Guidelines for Open Pit Slope Design, CSIRO Publishing, Collingwood, pp. 201–212.
Hustrulid, WA, McCarter, MK, & van Zyl, DJA 2001, Slope Stability in Surface Mining, Society for Mining, Metallurgy and Exploration, Littleton.
Hadjigeorgiou, J & Harrison, JP 2011, ‘Uncertainty and sources of error in rock engineering’, in Q Qian & X Zhou (eds), Proceedings of the 12th ISRM International Congress on Rock Mechanics: Harmonising Rock Engineering and the Environment, CRC Press, Leiden, pp. 2063–2067.
Haile, A 2004, ‘A reporting framework for geotechnical classification of mining projects, AusIMM Bulletin, September/October 2004, pp, 30–37.
Hoek, E 1994, ‘The challenge of input data for rock engineering’, letter to the editor, ISRM News Journal, vol. 2, no. 2, pp. 23–24.
Itasca International, Inc. 2019a, FLAC3D, computer software, Itasca International, Inc., Minneapolis, https://www.itascacg.com/software/flac3d
Itasca International, Inc. 2019b, 3DEC, computer software, Itasca International, Inc., Minneapolis, https://www.itascacg.com/software/3dec
Jefferies, M, Lorig L & Alvarez, C 2008, ‘Influence of rock strength spatial variability on slope stability’, in R Hart, C Detournay & P Cundall (eds), Proceedings of the First International FLAC/DEM Symposium on Numerical Modelling, Itasca International, Inc., Minneapolis.
Kim, YC, Cassun, WC & Hall, TE 1976, Pit Slope Manual Supplement 5-3: Financial Computer Programs, Canada Department of Energy, Mines and Resources,
Lai, FJ, Bamford, WE, Yuen, STS & Li, T 2009, ‘Implementing value at risk in slope risk evaluation’, Proceedings of the Third International Symposium on Rock Slope Stability in Open Pit Mining and Civil Engineering, Universidad de los Andes, Santiago.
Lilly, PA 2006, ‘Geotechnical risk considerations in mine planning’, in R Dimitrakopoulus (ed.), Orebody Modelling and Strategic Mine Planning – Uncertainty and Risk Management Models, Spectrum Series no. 14, The Australasian Institute of Mining and Metallurgy, Melbourne.
Lorig, LJ 2009, ‘Challenges in current slope stability analysis methods’, Proceedings of the Third International Symposium on Rock Slope Stability in Open Pit Mining and Civil Engineering, Universidad de los Andes, Santiago.
Lorig, L, Stacey, P & Read, J 2009, ‘Slope design methods’, in J Read & P Stacey (eds), Guidelines for Open Pit Slope Design, CSIRO Publishing, Collingwood, pp. 237–264.
McMahon, BK 1985, Geotechnical Design in the Face of Uncertainty: EH Davis Memorial Lecture, Australian Geomechanics Society, Barton.
Read, JRL 1994, ‘Risk analysis and uncertainty in open pit mine design’, Proceedings of the 4th Large Open Pit Conference, The Australian Institute of Mining and Metallurgy, Melbourne, pp. 139–143.
Read, J 2009a, ‘Structural model’, in J Read & P Stacey (eds), Guidelines for Open Pit Slope Design, CSIRO Publishing, Collingwood, pp. 69–82.
Read, J 2009b, ‘Acceptance criteria’, in J Read & P Stacey (eds), Guidelines for Open Pit Slope Design, CSIRO Publishing, Collingwood, pp. 221–236.
Read, J 2009c, ‘Data uncertainy’, in J Read & P Stacey (eds), Guidelines for Open Pit Slope Design, CSIRO Publishing, Collingwood, pp. 213–220.
Read, J & Stacey, P, 2009, Guidelines for Open Pit Slope Design, CSIRO Publishing, Collingwood.
Stacey, P 2009, ‘Fundamentals of slope design’, in J Read & P Stacey (eds), Guidelines for Open Pit Slope Design, CSIRO Publishing, Collingwood, pp. 1–14.
Steffen, OKH 1997, ‘Planning of open pit mines on risk basis’, Journal of The Southern African Institute of Mining and Metallurgy, vol. 2, pp. 47–56.
Swindels, CF 1990, ‘Geotechnical studies for open pit mines – West Australian operating experience’, Proceedings of the Mine Geologists Conference, The Australian Institute of Mining and Metallurgy, Melbourne, pp. 160–170.




© Copyright 2019, Australian Centre for Geomechanics (ACG), The University of Western Australia. All rights reserved.
Please direct any queries or error reports to repository-acg@uwa.edu.au