Authors: Rwodzi, L; Joughin, W; Stacey, TR


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Rwodzi, L, Joughin, W & Stacey, TR 2011, 'Rockfall risk — how well do we understand the consequences of the decisions we make?', in Y Potvin (ed.), Strategic versus Tactical 2011: Proceedings of the Fourth International Seminar on Strategic versus Tactical Approaches in Mining, Australian Centre for Geomechanics, Perth, pp. 179-194,

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The consequences of rockfalls in the narrow tabular mining geometry typical of the gold and platinum operations in South Africa are numerous and vary depending on rockfall size and applicable remedial strategy. Rockfalls are a significant cause of mining accidents, and also result in losses to the mining operation due to such accidents as well as reduced productivity, dilution, re-supporting, and loss of sweepings. Pillars and remnants may also have to be left, which results in loss of ore, reducing the available reserves. While these financial losses can be significant, there are commonly no records of the evaluation of such losses on mines. The financial evaluation of risk mitigation is usually tactical, being based only on the cost of implementing a support system, and does not take into account the losses resulting from accidents and incidents. The losses associated with rockfalls for different support designs are rarely quantified, hence the question, “How well do we understand the consequences of the decisions we make?” A more realistic evaluation of alternative support designs should compare the total cost of implementing the support system and the inherent risk of rockfalls. To determine the inherent risk of rockfalls, the consequences of rockfalls must be identified and quantified. In this paper, a generic methodology to quantify the cost of the losses associated with rockfalls is proposed. The methodology was developed after extensive research was conducted on two South African narrow tabular mining operations. The methodology enables the calculation of risk associated with different support options, and the risk is expressed in monetary terms (South African rands are used in the paper), a language well understood by management. Management can therefore be involved in the design of risk mitigating systems, since they can determine the acceptable risk that the rock engineer can apply in the support design. Safety and value to the mining operation can therefore be optimised, which represents a strategic approach to rock support design rather than the tactical approach that is currently practised.

Baecher, G.B. (1981) Risk Screening for Civil facilities: Massachusetts Institute of Technology, Department of Civil Engineering, CER, Vol. 81, pp. 90–110.
Baecher, G.B. and Christian, T.J. (2003) Reliability and Statistics in Geotechnical Engineering, John Wiley and Sons, West Sussex, England.
Barton, N., Lien, R. and Lunde, J. (1974) Engineering classification of rock masses for the design of tunnel support, Rock Mechanics, Vol. 6 (4), pp. 189–236.
Bawden, W.F. (2008) Risk Assessment in Strategic and Tactical Geotechnical Underground Mine Design, in Proceedings from 42nd US Rock Mechanics Symposium and 2nd US-Canada Rock Mechanics Symposium, held in San Francisco, 29 June–2 July 2008.
Beauchamp, K.J., Carvalho, J., Castro, L. and Morrison, D.M. (1998) Probabilistic Analysis for Ground Support for Underground Mines, CIM, Montreal.
Brummer, R.K. and Kaiser, P.K. (1995) Risk–Cost Benefit Analysis for Support Design in Burst-Prone Mines, Transactions from Institute of Materials, Minerals and Mining, January–April 1995, Vol. 104, pp. A71–A75.
Carter, T.G. and Miller, R.L. (1995) Crown-pillar risk assessment–planning aid for cost effective mine closure remediation, Transactions from Institute of Materials, Minerals and Mining (Section A: Mining Technology), January–April 1995, Vol. 104, pp. A41–A57.
Chowdhury, R.N. and Flentje, P.N. (1998) A landslide database for landslide hazard assessment, in Proceedings 2nd International Conference on Environmental Management, M. Sivakumar and R.N. Chowdhury (eds), February 10–13, Wollongong, Australia, Elsevier, London, pp. 1229–1239.
Christian, J.T. (2004) Geotechnical Engineering Reliability: How well do we know what we are doing?, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, ISSN 10900241/2004/10-985-1003.
Contreras, L.F., LeSeur, R. and Maran, J. (2006) A case study of risk evaluation at Cerejon Mine, in Proceedings from International Symposium on Stability of Rock Slopes in Open Pit and Civil Engineering, April 2006, Cape Town, South Africa, South African Institute of Mining and Metallurgy, pp. 181–210.
Davies, M.P. (1997) Potential problem analyses: A practical risk assessment technique for the mining industry, CIM Bulletin, April 1997, Vol. 90, pp. 49–52.
Dunn, M.J., Earl, P.J. and Watson, J. (2008) Support design using probabilistic keyblock methods, in Proceedings 6th International Symposium on Ground Support in Mining and Civil Engineering Construction, SAIMM, SANIRE and ISRM.
Duzgun, H.S.B. and Einstein, H.H. (2004) Assessment and Management of rockfall risks in Underground coal mines, Safety Science Vol. 42, pp. 23–41.
Einstein, E.E. (1996) Risk and risk analysis in rock engineering, Tunnell, Underground Space Technology, Vol. 11 (2), pp. 141–155.
Einstein, H.H. (2003) Uncertainty in Rock Mechanics and Rock Engineering–Then and Now, ISRM–Technology Roadmap for Rock Mechanics, SAIMM.
Esterhuizen, G.S. (2003) JBLOCK user manual, Pretoria.
Gumede, H. (2006) Development of data sets on joint characteristics and consideration of associated instability for a typical South African gold mine, MSc Eng Dissertation, University of the Witwatersrand.
Joughin, W.C. (2008) A preliminary model for quantifying the risk of rockfalls and evaluating the benefits of safety spending.
Laubscher, D.H. (1990) A geomechanics classification system for the rating of rock mass in mine design, in the Journal of South African Institute of Mining and Metallurgy, Vol. 90, No. 10, pp. 257–273.
Marx, C. (1996) An activity based costing approach to fall of ground accidents in a South African gold mine, Potchefstroom: PU vir CHO (Dissertation–MBA).
Peck, R.B. (1969) The observational method in applied soil mechanics–9th Rankine Lecture, Geotechnique, Vol. 19, pp. 171–187.
Pine, R.J. and Arnold, P.N. (1996) Application of risk assessment methods to underground excavations, in Proceedings Eurock’96, Turin, Italy, G. Barla (ed), Balkema, pp. 1189–1196.
Pine, R.J. and Thin, I.G. (1993) Probabilistic risk assessment in mine pillar design, in Proceedings Innovative Mine Design for the 21st Century, W.F. Bawden and J.F. Archibald (eds), Balkema, pp. 363–373.
Potvin, Y. (1998) Empirical stope design in Canada, PhD Thesis, University of British Columbia.
Potvin, Y. and Hadjigeorgiou, J. (2001) The stability graph method for open stope design, W.A. Hustrulid and R.L. Bullock (eds), in Underground mining methods: engineering fundamentals and international case studies, Society for Mining Metallurgy and Exploration Inc, SME, pp. 513–520.
Stacey, T.R. (2006) Design–A Strategic Issue, in Proceedings 2nd International Seminar on Strategic versus Tactical Approaches in Mining, Perth, Western Australia, 8–10 March 2006, Australian Centre for Geomechanics, Section 4, 13 p.
Stacey, T.R. (2007) Is Rock Engineering Addressing Risk Appropriately?, Redefining the boundaries Part 2, Proceedings SANIRE 2007 Symposium, Free State, South Africa.
Summers, J. (2000) Analysis and Management of Mining Risk, in Proceedings MassMin 2000, G. Chitombo (ed), 29 October to 2 November 2000, Brisbane, Australia, Australasian Institute of Mining and Metallurgy, Melbourne, pp. 63–79.
Swart, A.H., Stacey, T.R., Wesseloo, J., Joughin, W.C., Le Roux, K., Walker, D. and Butcher, R. (2000) Investigation of factors governing the stability/instability of stope panels in order to define a suitable design methodology for near surface and shallow mining operations, Safety in Mines Research Advisory Committee (SIMRAC) final project report OTH501.
Tapia, A., Contreras, L.F., Jefferies, M.G. and Steffen, O. (2007) Risk evaluation of slope failure at Chuquicamata Mine, in Proceedings International Symposium on Rock Slope Stability in Open Pit Mining and Civil Engineering (Slope07), Yves Potvin (ed), 12–14 September 2007, Perth, Western Australia, Australian Centre for Geomechanics, Perth, pp. 477–496.
Terbrugge, P.J., Steffen, O.K.H., Wesseloo, J. and Venter, J. (2006) A risk consequence approach to open pit slope design, in Proceedings from International Symposium on Stability of Rock slopes in Mining and Civil Engineering Situations, Cape Town, April 2006, in the Journal of South African Institute of Mining and Metallurgy, pp. 81–96.
Tyler, D.B., Trueman, R. and Pine, R.J. (1991) Rockbolt support design using a probabilistic method of keyblock analysis, In Rock Mechanics as a Multidisciplinary Science, J.C. Roegiers (ed), Rotterdam, Balkema, pp. 1037–1047.
Vanmarcke, E.H. and Bohenblust, H. (1982) Methodology for integrated risk assessment for dams, MIT Research Report, Vol. 82, pp. 11–23.
Viner, H.C. (2002) Risk management lecture notes, School of Mining Engineering, Witwatersrand University.
Wong, W. (2005) How did that happen? – Engineering Safety and Reliability, Professional Engineering Publishing Limited, Edmonds, UK.

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