Shiels, A 2022, 'Unearthing the Black Rock orebody with sublevel caving', in Y Potvin (ed.), Caving 2022: Proceedings of the Fifth International  Conference on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 1443-1458, https://doi.org/10.36487/ACG_repo/2205_101
(https://papers.acg.uwa.edu.au/p/2205_101_Shiels/)
Abstract: The Black Rock orebody is located at Mount Isa Mines, in northwest Queensland, Australia. Owned and operated by Glencore, the mine has been in operation for almost 100 years. The orebody was last mined as an open cut from 1957 to 1965. It was closed due to two major wall failures and ongoing stability issues one bench short of completion, leaving behind a large quantity of high-grade ore. The remaining orebody is being extracted using the sublevel cave (SLC) mining method. The orebody is located in extensively altered and weak kaolinic shales, with zones of hot and reactive ground. Other challenges include naturally occurring and historic voids, and mining proximity to fixed surface infrastructure. The small SLC has a planned draw of approximately 1.5 million tonnes at 4.5% copper over four years, which commenced in September 2020. This paper discusses the work completed during the project phase and the key learnings during the initial execution phase. This includes geotechnical characterisation, caveability and subsidence assessments, fragmentation testing, cave flow and rock cutter trials, and development of a real-time instrumentation system to monitor surface infrastructure.

Keywords: sublevel caving, weak and poor rock mass, rock cutting, subsidence, cave flow