Weir, FM, Fowler, MJ, Sullivan, TD, Kobler, M & Bu, J 2020, 'Evolution of a geotechnical model for slope design in an active volcanic environment', in PM Dight (ed.), Slope Stability 2020: Proceedings of the 2020 International Symposium on Slope Stability in Open Pit Mining and Civil Engineering
, Australian Centre for Geomechanics, Perth, pp. 455-472, https://doi.org/10.36487/ACG_repo/2025_26
The Lihir gold mine is located at the base of the amphitheatre of the Luise volcano, which is a young strata volcano that has undergone sector collapse, phreatomagmatic activity and alteration. This creates a geotechnically complex environment due to the co-incidence of complicated lithologies, alteration, structural, geothermal conditions, existing landslides and high seismicity.
The rock mass model at Lihir comprises units that may be grouped into the following broad categories; surficial sediments, lithological and alteration. The structure model was developed understanding the geotechnically important strato-volcano regions which have been overprinted and modified by sector collapse and subsequent phreatomagmatic effects. The rock mass and structural understanding at Lihir are closely linked.
Groundwater flow at Lihir is driven by the interplay of rainfall recharge, deep geothermal upflow and the ocean. Due to the elevated rainfall rates occurring in the area, recharge is significant across the entire site. The groundwater and geothermal conditions are complex and this makes pore pressure estimations for slope stability some of the most complicated undertaken in modern mining practices around the world.
The geotechnical model comprises a view of the rock mass, structure and pore pressures. This paper presents the geotechnical model for pit slope design at Lihir gold mine with a focus on how our understanding of ground conditions and controls on slope stability has evolved over time.
Keywords: geotechnical model, volcano, diatreme, slope design
Australian Geomechanics Society 2007, ‘Practice Note Guidelines for Landslide Risk Management 2007’, Journal of Australian Geomechanics Society, vol. 42, no. 1.
Blackwell, J 2010, Characteristics and origins of breccias in a volcanic-hosted alkalic epithermal gold deposit, Ladolam, Lihir Island, Papua New Guinea, PhD Thesis, University of Tasmania, Hobart.
Corbett, GJ & Leach, TM 1998, ‘Southwest Pacific rim gold-copper systems: structure, alteration and mineralisation’, Society of Economic Geologists, Littleton, Special Publication No. 6.
Gifkins, C, Herrmann, W & Large, R 2005, Altered volcanic rocks: a guide to description and interpretation, Centre for Ore Deposit Research, Hobart.
Hencher, S 2012, Practical Engineering Geology, Spon Press, New York.
Hunt, AJ 2002, The discovery of structure confined blind ore extensions to the Ladolan deposits, Lihir, PNG, Exploration in the Shadow of the Headframe. North Sydney: Annual Meeting of the Sydney Mineral Exploration Discussion Group,
Komyshan, P 1999, Geological interpretations of Lihir Island: Consulting Scientists of Australia (CSA Australia Pty Ltd), unpublished report R8.99, p. 40.
McPhie, J, Doyle, M & Allen, R 1993, ‘Volcanic textures: a guide to the interpretation of textures’, Volcanic Rocks, CODES Key Centre, Hobart.
Sillitoe, RH, Baker, E & Brook, WA 1984, ‘Gold deposits and hydrothermal eruption breccias associated with a maar volcano at Wau, Papua New Guinea’, Economic Geology, vol. 79, no. 4, pp. 638–655.
Wallace, L, Stevens, C, Silver, E, McCaffrey, R, Loratung, W, Hasiata, S & Taugaloidi, J 2004, ‘GPS and seismological constraints on active tectonics and arc-continent collision in Papua New Guinea: Implications for mechanics of microplate rotations in a plate boundary zone’, Journal of Geophysical Research, vol. 109,