The objective of pit slope optimisation programs during mining operations is twofold: to develop safe operating conditions and to minimise waste stripping ratios (O’Bryan, 2013). By achieving these two aims, the pit slope angle can be maximised, and in turn can have a significant positive impact on the economics of an open pit operation. One of the components of pit slope optimisation is the operational performance of the pit wall. A large component of operational performance is the implementation of effective wall control techniques – drilling, blasting and scaling.
The Boddington gold-copper mine is owned and operated by Newmont Mining Corporation. Located approximately 130 km south-east of Perth in Western Australia, the Boddington operations commenced mining in 2007, with production from two large open pits utilising large-scale non-selective open pit mining methods. Initial design recommendations indicated hard rock slopes could be constructed at an inter-ramp angle of 64 degrees – steep by industry standards. However, a challenge of the hard rock slopes at Boddington has been the inability to consistently achieve the required catch berm width to retain rockfall. As a result, the inter-ramp angle was reduced to 59 degrees. Consequently the pit slope configuration has experienced a number of changes since the commencement of operations, and numerous trials completed to increase the effectiveness of wall control techniques (Graf and Sullivan, 2016).
Through the ongoing refinement of wall control techniques, and close collaboration between technical and operational teams, significant improvements have been made in reducing crest loss and improving batter conditions, enabling wall steepening trials to be commenced.
Chung, J, Asad, M, Topal, E and Ghosh, A K, 2016. Determination of the Transition Point from Open Pit to Underground Mining, in Proceedings Ninth AusIMM Open Pit Operators’ Conference 2016, pp 95–95 (The Australasian Institute of Mining and Metallurgy: Melbourne).