This paper is hosted with the kind permission of the Universidad de Chile, Eighth International Conference & Exhibition on Mass Mining, 2020.
Mahayasa, M, Widijanto, E, Yuniar, AT & Gautama, R 2020, 'The final result of slope Optimization program at Grasberg surface mine in Papua, Indonesia', in R Castro, F Báez & K Suzuki (eds), MassMin 2020: Proceedings of the Eighth International Conference & Exhibition on Mass Mining
, University of Chile, Santiago, pp. 1384-1394, https://doi.org/10.36487/ACG_repo/2063_104
In order to maximize the pit value and achieve final pit design in a safe manner, the Grasberg surface mine initiated the slope optimization program in fourth quarter 2017; this program lasted 15 months before achieving the final pit. The optimization program focused on the Grasberg Intrusive Complex at radial sector 200˚- 360˚ with final Inter-ramp Slope Angle (ISA) up to 60˚. By the end of 2018, this program successfully had added 255 million pounds of copper and 660 kilo ounces of gold by opening extra width of the pushbacks and deepening the pit by two benches. Further mining of the Grasberg ore body will utilize block caving. The pit optimization had brought some of the block cave ore forward by a couple years and increased the value and life of the open pit. The pit steepening required intensive control and supervision to be successful. This paper outlines the slope optimization program at the end of the pit mining operations, requirements of the drill and blast improvement team, cutting-edge technology to provide actual wall condition for the quality control program, slope remediation and protection, real-time geotech monitoring program, and excavation control to manage geotechnical risks and maximize pit value.
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Nicholas, D 2002, ‘Comment on PTFI Memo, dated 28 May 2002: Geotechnical assessments on steepening slope for mining
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Read, J, & Stacey, P 2009, ‘Guidelines for open pit slope design’, CSIRO, Canberra, pp. 265 – 326.
Schmelter, S & Nicholas, D 2004, ‘Analysis and documentation of the 9 October 2003 Grasberg south wall slide’, Call&Nicholas Inc report for PT Freeport Indonesia, Papua.
Widijanto, E, Gautama, R, Siburian, P, Sirait, J, & Yuniar, A 2018, ’Slope optimization program to maximize pit value Grasberg Surface Mine, Papua – Indonesia ‘, in ISRM International Symposium: proceedings of 10th Asian Rock Mechanics Symposium, Singapore pp. 1-9.