Narendranathan, S, Patel, N, Mok, T, Stipcevich, J & Symonds, A 2022, 'A case study: conceptual rehabilitation and closure planning for the Loy Yang mine using the risk-based probabilistic approach employing the Mine Geotechnical Risk Index methodology', in AB Fourie, M Tibbett & G Boggs (eds), Mine Closure 2022: Proceedings of the 15th International Conference on Mine Closure
, Australian Centre for Geomechanics, Perth, pp. 449-462, https://doi.org/10.36487/ACG_repo/2215_31
In the mining industry, risk is conventionally evaluated under absolute conditions – that is, operational scenarios or, say, a completed rehabilitated scenario. However, challenges arise when applying these methods to a mine that is in a transient state – that is, transitioning from operation to final rehabilitated conditions. Risk-based approaches, such as the Mine Geotechnical Risk Index (MGRI) developed by Narendranathan et al. (2019), may be adopted to quantify the geotechnical risks associated with lake filling, and are useful tools for assessing transient risk profiles.
AGL’s Loy Yang mine, located in Victoria, Australia, is in the process of rehabilitation and closure planning and is considering a full lake option as part of their final landform.
This paper demonstrates how the MGRI approach was successfully employed to assess the batter stability implications during proposed lake filling so as to determine slope supplementation requirements under varying pit lake levels, to conceptualise transient slope supplementation measures to manage slope
stability–related risks during this phase.
Keywords: rehabilitation and closure, post-closure, large open cut coal mine, risk-based stability assessment
Ágústsson, K, Jóhanneson, T, Sauermoser, S, Sigurðsson, Hó & Jensen, EH 2003, Hazard Zoning for Bíldudalur, Vesturbyggð, report 03034, Icelandic Meteorological Office, Reykjavík, viewed 6 February 2019,
Ammann, WJ 2005, ‘Natural hazards: risk concept and integral risk management’, in WJ Ammann, S Dannenmann & L Vulliet (eds), Proceedings of RISK21 – Coping with Risks due to Natural Hazards in the 21st Century, A.A. Balkema, Rotterdam.
Bell, R, Glade, T & Danscheid, M 2005, Risks in Defining Acceptable Risk Levels, University of Bonn, Bonn.
Borter, P 1999, ‘Risikoanalyse bei gravitativen naturgefahren: methode’, Umwelt‐Materialien, no. 107/I.
Department of Jobs, Precincts and Regions 2020, Geotechnical Guideline for Terminal and Rehabilitated Slopes.
Geotechnical Engineering Office 1997, Landslides and Boulder Falls from Natural Terrain: Interim Risk Guidelines, GEO report no. 75, Geotechnical Engineering Office, Kowloon.
GHD 2022, Loy Yang Mine – 2019 Whole of Life Concept Geotechnical Assessment, GHD report ref: 311148420-15271-19.
Harr, ME 1984, Reliability-Based Design in Civil Engineering, Department of Civil Engineering, School of Engineering, North Carolina State University, Raleigh.
Jóhannesson, T & Ágústsson, K 2002, Hazard Zoning for Debris Flows, Rockfall, Slushflows and Torrents and Slushflows Mixed with Soil in Steep Slopes, report TóJ/Kri‐2002/01, Icelandic Meteorological Office, Reykjavík, in Icelandic.
Jónasson, K, Sigurdsson, SP & Arnalds, P 1999, Estimation of Avalanche Risk, report VÍ‐R99001‐ÚR01, Icelandic Meteorological Office, Reykjavík.
Malone, AW 2005, ‘The story of quantified risk and its place in slope safety policy in Hong Kong’, in T Glade, MG Anderson & M Crozier (eds), Landslide Hazard and Risk, John Wiley & Sons, Chichester.
Narendranathan, S 2009, ‘Fundamentals of probabilistic slope design and its use in pit optimization’, Proceedings of the 43rd US Rock Mechanics Symposium & 4th US ‐ Canada Rock Mechanics Symposium, American Rock Mechanics Association, Alexandria.
Narendranathan, S & Cheng, M 2019, ‘Development of the Mine Geotechnical Risk Index’, in J Wesseloo (ed.), MGR 2019: Proceedings of the First International Conference on Mining Geomechanical Risk, Australian Centre for Geomechanics, Perth,
Narendranathan, S, Stipcevich, J, Symonds, A & Faithful, J 2022, ‘A case study: development of a conceptual ground movement model for the Loy Yang mine with consideration to rehabilitation and closure’, in M Tibbett, AB Fourie & G Boggs (eds), Mine Closure 2022: Proceedings of the 15th International Conference on Mine Closure, Australian Centre for Geomechaincs, Perth,
Raisbeck, D 1980, Batter Stability: Yallourn North Open Cut, Victoria, paper presented at the Seminar on Slope Stability, Australian Geomechanics Society – Victoria Group, 2 April 1980.
Read, J & Stacey, P 2009, Guidelines for Open Pit Slope Design, CSIRO Publishing, Collingwood.
The Ministry of the Environment 2000, Reglugerð nr. 505/2000, Reglugerð um Hættumat Vegna Ofanflóða, Flokkun og Nýtingu Hættusvæða og gerð Bráðabirgðahættumats (Regulation on Hazard Zoning for Avalanches, Debris Flows and Rockfall, the Usage of Hazard Zones, and the Making of Preliminary Hazard Zoning), viewed 16 August 2018,