Campbell, AD 2018, 'Full-scale experiments to measure the effect of crosscut height on recovery in sublevel cave mines', in Y Potvin & J Jakubec (eds), Proceedings of the Fourth International Symposium on Block and Sublevel Caving
, Australian Centre for Geomechanics, Perth, pp. 443-456.
A major disadvantage of the sublevel cave (SLC) mining method is the potential for substantial dilution and ore loss. Scale-model experiments demonstrate that gravity flow and recovery in SLC mines is affected by crosscut geometry. Several authors also suggest that crosscut height affects the digging depth of loading equipment and therefore influences recovery, particularly from the back of a blasted ring. However, specifically designed full-scale experiments that directly compare the effect of different crosscut heights on recovery have not been published to date.
This paper details the results of experiments conducted in an operating SLC mine to measure the effect of crosscut height on recovery and depth of draw. Two trial programs, each consisting of six blast rings, and each with approximately 285 electronic cave markers, were used to measure recovery in real time. One trial measured recovery for the standard 5 m crosscut height and the other for a crosscut height of 4 m; the smallest practical dimension for loaders used at the mine. The effect of reducing the crosscut height is a reduction in the distance a muck pile extends from the brow. The literature suggests that a shorter muck pile will enable loading equipment to dig deeper relative to the drawpoint brow. This was hypothesised to increase ore recovery from the back of the blast ring in a mining method in which shallow draw is common.
The experimental program showed that reducing the crosscut height did not achieve the desired effect of improving primary recovery. It is proposed that drawpoint flow is controlled by the outflow depth at the drawpoint brow rather than the dig depth or length of the muck pile under the test conditions. Observations identified that the bucket of the loader did not penetrate the muck pile beyond the drawpoint brow, despite the crosscut height being reduced as far as practical. The experimental results do not justify SLC mines reducing the crosscut height to increase ore recovery. In terms of mine design guidelines, it is recommended that crosscut height be based solely on geotechnical, operational and equipment requirements.
An accompanying paper in the proceedings (Campbell 2018) details the results of experiments conducted using different ring burdens and explosive densities to determine the effect on fragmentation and recovery.
Keywords: gravity flow, mine design, ore recovery, sublevel caving
Brunton, I 2009, The Impact of Blasting on Sublevel Caving Flow Behaviour and Recovery, PhD thesis, The University of Queensland, Brisbane.
Brunton, I, Fraser, SJ, Hodgkinson, JH & Stewart, PC 2010, ‘Parameters influencing full scale sublevel caving material recovery at the Ridgeway gold mine’, International Journal of Rock Mechanics and Mining Sciences, vol. 47, no. 4, pp. 647–56.
Bull, G & Page, CH 2000, ‘Sublevel caving—today’s dependable low-cost ‘ore factory’’, in G Chitombo (ed.) Proceedings of MassMin 2000, The Australasian Institute of Mining and Metallurgy, Melbourne, pp. 537–556.
in Y Potvin & J Jakubec (eds), Proceedings of the Fourth International Symposium on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp.485–498.
Campbell, AD & Power, GR 2017, ‘Improving calibration of flow models against SLC marker trials by linking blasting effects to particle mobility’, Proceedings of the 13th AusIMM Underground Operators’ Conference, The Australasian Institute of Mining and Metallurgy, Melbourne, pp. 11–22.
Dunstan, G & Power, G 2011, ‘Sub level caving’, in P Darling (ed.), SME Mining Engineering Handbook, 3rd edn, Society for Mining, Metallurgy, and Exploration, Englewood.
Elexon Mining 2017, Smart Marker System, apparatus, Elexon Mining, Brendale, viewed 20 May 2017,
Gustafsson, P 1998, Waste Rock Content Variations During Gravity Flow in Sublevel Caving: Analysis of Full-scale Experiments and Numerical Simulations, PhD thesis, Luleå University of Technology, Luleå.
Hollins, B & Tucker, J 2004, ‘Draw point analysis using a marker trial at the Perseverance Nickel Mine, Leinster, Western Australia’, in A Karzulovic & M Alfaro (eds), Proceedings of MassMin 2004, Instituto de Ingenieros de Chile, Santiago, pp. 498–502.
Just, GD 1972, ‘Sublevel caving mining design principles’, Institution of Mining and Metallurgy Section A, October, pp. A214–A220.
Kosowan, MI 1999, Design and Operational Issues for Increasing Sublevel Cave Intervals at Stobie Mine, MSc thesis, Laurentian University, Sudbury, p. 152.
Kvapil, R 1998, ‘Mechanics and design of sublevel caving systems’, in RE Gertsch & RL Bullock (eds), Techniques in Underground Mining, Society for Mining Metallurgy and Exploration, Englewood, p. 621.
Page, CH & Bull, G 2001, ‘Sublevel caving: a fresh look at this bulk mining method’, in WA Hustrulid & RL Bullock (eds), Underground Mining Methods: Engineering Fundamentals and International Case Studies, Society for Mining, Metallurgy, and Exploration, Englewood, pp. 385–394.
Power, GR 2004, Modelling Granular Flow in Caving Mines: Large Scale Physical Modelling and Full Scale Experiments, PhD thesis, The University of Queensland, Brisbane.
Quinteiro, CR, Larsson, L & Hustrulid, WA, 2001, ‘Theory and practise of very large scale sublevel caving’, in WA Hustrulid & RL Bullock (eds), Underground Mining Methods: Engineering Fundamentals and International Case Studies, Society for Mining, Metallurgy, and Exploration, Englewood, pp. 381–384.
Trotter, DA & Goddard, GJ 1981, ‘Design techniques for sublevel caving layouts’, Canadian Institute of Mining Bulletin, January 1981, pp. 92–100.
Wimmer, M 2010, ‘Gravity flow of broken rock in SLC - the state of the art’, Swebrec Report 2010:P1, Luleå University of Technology, Luleå.
Wimmer, M 2012, Towards Understanding Breakage and Flow in Sublevel Caving, PhD thesis, Luleå University of Technology, Luleå.
Zhang, G 2004, ‘Behaviour of caved ore mass in sublevel caving and its effect on ore dilution’, in A Karzulovic and M Alfaro (eds), Proceedings of MassMin 2004, Instituto de Ingenieros de Chile, Santiago, pp. 238–242.