This paper presents a case study demonstrating active geotechnical pit slope management at the now completed Carina Iron Ore Project operated by Mineral Resources Ltd (MRL). The site is located 105 km north-east of Southern Cross, Western Australia. The paper is primarily focused on the slope stability failure modes and the remedial measures employed to maintain mining.
Between a quarter and a third of the excavated slopes were impacted by some form of instability that was beyond expectations of the intended slope design criteria and common practice. Ongoing mining was supported by intensive geotechnical pit slope management including close cooperation between geotechnical, mine planning and operations staff to achieve timely and practical mining solutions.
Mining encountered varied slope failure mechanisms which required a combination of remedial solutions comprising: horizontal depressurisation holes, deferral of excavation, unloading, buttressing and catch berms.
The root cause of the challenging slope performance was a mismatch between the predicted and encountered geotechnical model, resulting from a failure to recognise the critical mechanisms that control slope stability.
Despite the extensive zones of instabilities at completion of mining, full ore recovery was achieved without major delays and in a controlled and safe manner.
Fowler, M, Strang, D and Jaine, R, 2016. Adapting to Geotechnical Change – a Case Study of the Carina Open Pit Mine, in Proceedings Ninth AusIMM Open Pit Operators’ Conference 2016, pp 150–161 (The Australasian Institute of Mining and Metallurgy: Melbourne).