Authors: Hormazabal, E; Alvarez, R; Valderrama, C

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This paper is hosted with the kind permission of the Universidad de Chile, Eighth International Conference & Exhibition on Mass Mining, 2020.


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Hormazabal, E, Alvarez, R & Valderrama, C 2020, 'A simplified geotechnical risk-based approach for extraction level pillar design in Block/Panel caving mines', in R Castro, F Báez & K Suzuki (eds), MassMin 2020: Proceedings of the Eighth International Conference & Exhibition on Mass Mining, University of Chile, Santiago, pp. 341-356,

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Definition of the extraction-level layout, including geometry and dimensions of the excavations, is an essential aspect of the design of any block/panel caving operation. The design needs to guarantee that the excavations remain stable and perform as intended during the life of mine, in other words, prior, during and after caving production takes place, a span of time that frequently involves decades. The layout of these excavations involves an intricate network of drifts, access tunnels, drawbells and other excavations. A complex 3D mechanical numerical model that incorporates the extraction level, the undercutting level and the broken material surfaces and which simulates the progression of the undercutting advance and resulting caving propagation was developed. The purpose of the model is to assess the layouts, in terms of stress concentrations and plastic damage in pillars at the extraction level, particularly in the vicinity of the caving front. A method for geotechnical risk-based design under high stress conditions which uses tridimensional numerical modelling and probabilistic methods of analysis to determine the probability of pillar failure is described in this paper. The methodology included three main tasks: (1) evaluation of the factor of safety (FOS) and probability of failure (POF) representative of the stability conditions of the extraction level layout; (2) evaluation of the risk associated with economic losses resulting from impacts on equipment and on production; and (3) generation of a simplified geotechnical risk map to compare several mining years. The results of these analyses enabled the identification of risk mitigation options for those situations where acceptability criteria are exceeded.

Ang, A, & Tang, W1975, ‘Probability concepts in Engineering Planning and Design’, John Wiley and Sons.
Araneda, O & Sougarret, A 2008, ’Lessons learned in cave mining at the El Teniente mine over the period 1997-2007’ in H Schunnesson, E Nordlund (eds), Proceedings of MassMin 2008, Lulea, Sweden, 9-11 June 2008.
Brady, BHG & Brown, ET 1993, ‘Rock Mechanics for Underground Mining’, 2nd edition, Chapman and Hall: London, p 571.
Brown, ET 2007, ‘Block Caving and Geomechanics (2Ed)’, – The International Caving Study 1997 – 2004., The University of Queensland. Australia.
Cai, M, Kaiser, P, Tasaka, Y, Maejima, T, Morioka, H, & Minami, M 2004, ‘Generalized crack initiation and crack damage stress thresholds of brittle rock masses near underground excavations’, International Journal of Rock Mechanics and Mining Sciences, vol. 41, pp. 833-847.
Cavieres, P, Gaete, S, Lorig, L, & Gómez, Pm 2003, ‘Three-dimensional analysis of fracturing limits induced by large scale underground mining at El Teniente mine’, In P. Culligan, H. H. Einstein, & A. Whittle (Eds.), 39th US Rock Mechanics Symposium, Massachusetts, USA: MIT, pp. 893-900.
Contreras, L-F, Hormazabal, E, Ledezma, R & Arellano, M 2019, ‘Geotechnical risk analysis for the closure alternatives of the Chuquicamata open pit’, in J Wesseloo (ed.), Proceedings of the First International Conference on Mining Geomechanical Risk, Australian Centre for Geomechanics, Perth, pp. 373-388.
Contreras, LF 2015, ‘An economic risk evaluation approach for pit slope optimization’, The Journal of the Southern African Institute of Mining and Metallurgy, vol. 115, pp. 607-622.
Diederichs, MS 2007, ‘The 2003 Canadian Geotechnical Colloquium: Mechanistic interpretation and practical application of damage and spalling prediction criteria for deep tunnelling’, Canadian Geotechnical Journal, vol. 44, no.9, pp. 1082–1116, .
Esterhuizen, GS, Tyrna, P, & Murphy, MM 2018, ‘A Case Study of Pillar Collapse at a Limestone Mine in Pennsylvania’ - 52nd US Rock Mechanics/Geomechanics Symposium.
Flores-Gonzalez, G 2019, ‘Major hazards associated with cave mining: are they manageable?’, in J Wesseloo (ed.), Proceedings of the First International Conference on Mining Geomechanical Risk, Australian Centre for Geomechanics, Perth, pp. 31-46.
Flores, G & Karzulovic, A 2002, ‘Benchmarking Report’, prepared for ICS-II, JKMRC and Itasca Consulting Group, Inc.: Brisbane.
Hajiabdolmajid, V, & Kaiser, P 2003, ‘Brittleness of rock and stability assessment in hard rock tunneling’, Tunnelling and Underground Space Technology, vol.18, no. 1, pp. 35-48.
Harr, ME 1996, ‘Reliability-based design in civil engineering’, Dover Publications, Mineola, New York, USA.
Hawkes, I 1966, ‘Significance of In-Situ Stress Levels’, Proc. 1st Intl. Cong. Intl. Soc. of Rock Mech., vol. 3.Hoek, E & Brown, ET 2019, ‘The Hoek-Brown failure criterion and GSI – 2018 edition. Journal of Rock Mechanics and Geotechnical Engineering, vol. 11, no. 3, pp. 445-463.
Hormazabal, E, Alvarez, R, Russo, A & Acevedo, D 2018, ‘Influence of the undercut height on the behaviour of pillars at the extraction level in block and panel caving operations’, in Y Potvin & J Jakubec (eds), Proceedings of the Fourth International Symposium on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 351-362.
Itasca 2015, ‘FLAC3D. Fast Lagrangian analysis of continua in 3 dimensions (computer software)’. Version 5.0. Itasca Consulting Group. Minneapolis, Minnesota.
Joughin, WC 2017, ‘Dealing with uncertainty and risk in the design of deep and high stress mining excavations’, in J Wesseloo (ed.), Proceedings of the Eighth International Conference on Deep and High Stress Mining, Australian Centre for Geomechanics, Perth, pp. 489-507.
Kaiser, P, Kim, B, Bewick, R, & Valley, B 2011, ‘Rock mass strength at depth and implications for pillar design’, Mining Technology, vol. 120, no. 3, pp. 170-179.
Karzulovic, A 2001, ‘Tronaduda & Geomecánica hacia la optimización del negocio minero’ – 5 Seminario Dyno Nobel – 19 – 20 de julio, 2001 – Antofagasta Chile, in Spanish.
Langford, J & Diederichs, MS 2015, ‘Reliable support design for excavations in brittle rock using a global response surface method’, Rock Mechanics and Rock Engineering, vol. 48, pp. 669-689.
Laubscher, D, Guest, A & Jakubec, J 2017, ‘Guidelines on Caving Mining Methods: The Underlying Concepts’, WH Bryan Mining and Geology research Center, Brisbane, St. Lucia, Queensland 4072, Australia.
Lü, Q, & Low, BK 2011, ‘Probabilistic analysis of underground rock excavations using response surface method and SORM’, Computers and Geotechnics, vol. 38, no. 8, pp. 1008–1021, .
Martin, C, Kaiser, P, & McCreath, D 1999, ‘Hoek-Brown parameters for predicting the depth of brittle failure around tunnels’, Canadian Geotechnical Journal, vol. 36, pp. 136-151.
Montgomery, D 2001, ‘Design and analysis of experiments’, New York: John Wiley and Sons.
Morgan, MG & Herion, M 1990, ‘Uncertainty: A Guide to Dealing with Uncertainty in Quantitative’, Risk and Policy Analysis, 1st ed. New York: Cambrige University Press.
Oracle 2017, ‘CRYSTAL BALL v. 7.0’, Risk Analysis Program, USA.
Ortlepp, WD 1997, ‘Rock Fracture and Rockbursts – an illustrative study’, S. Afr. Inst. Min. Metall., p. 255.
Peng, Syd S 1986, ‘Coal Mine Ground Control’, 2nd Ed., Wiley Interscience, p. 491.
Rosenblueth, E 1975, ‘Point estimates for probability moments’, Proceedings of the National Academy of Sciences of the United States of America, 3812-3814.
Stacey, TR 2012, ‘Support of excavations subjected to dynamic (rockburst) loading’, Harmonizing Rock Engineering and the Environment – Proceedings of the 12th ISRM International Congress on Rock Mechanics, Beijing, China, 18-21 October 2011; Qihu Qian & Yingxin Zhou.
Steffen, O, Contreras, L, Terbrugge, P & Venter, J 2008, ‘A risk evaluation approach for pit slope design’, In: Proceedings of the 42nd U.S. Rock Mechanics Symposium and 2nd U.S. Canada Rock Mechanics Symposium, 29 June ⅓ 2 July 2008. San Francisco: ARMA 08-231.
Vásquez, P, Rubio, J & Cavieres, P 2008, ‘Methodology for estimating the “serviceability” of the UCL pillars at El Teniente mine, new mine level project, Codelco Chile’, in H Schunnesson, E Nordlund (eds), Proceedings of MassMin 2008, Lulea, Sweden, 9-11 June 2008.
Villegas, F, Diaz, J & Lledo, P 2009, ‘Modelo Conceptual Potencialidad de Colapso en Minería por Hundimiento: Proyecto Mina Chuquicamata Subterráneo’, XVI Mining Engineering Symposium – Universidad de Santiago de Chile, in Spanish.
Villegas, F 2008, ‘Prevención De Colapsos En Una Mina De Hundimiento Por Paneles En Ambiente De Roca Primaria’ – Tesis Magister – Universidad de Chile, in Spanish.
Wang, JA & Park HD 2001, ‘Comprehensive prediction of rockburst based on analysis of strain energy in rocks, Tunneling and underground space technology, pp. 49-57.
Wesseloo, J 2013, ‘Towards real-time probabilistic hazard assessment of the current hazard state for mines’, Proceedings of the Eighth International Symposium on Rockbursts and Seismicity in Mines, Geophysical Survey of Russian Academy of Sciences, Obninsk, Mining Institute of the Ural Branch of the Russian Academy of Sciences, A Malovichko and D Malovichko (eds), Perm, pp. 307-312.
Woodruff, S 1962, ‘Rock mechanics of block caving operations, MINING RESEARCH, edited by G. Clarke, Pergamon Press, New York.

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