Document Type

Conference Paper

Publication Date

2020

Publication Details

Ellie Hawkins and Scott Sheldon, Evaluation of the recovery of block cave underbreak by sub level caving, Proceedings of the 2020 Coal Operators' Conference, University of Wollongong - Mining Engineering, 12-14 February 2020, University of Wollongong, 340-352.

Abstract

Northparkes Mines (NPM) is located 27 kilometres north of the township of Parkes in central New South Wales, Australia. The operations consist of underground block cave mines and an ore processing plant which produces high grade copper and gold concentrate. Production is currently sourced from the E48 Lift 1 block cave mine, E26 Sublevel Cave (SLC) and open cut stockpiles. Mining at Northparkes has been underway for over 20 years in various forms. Beginning with open pit mining and later progressing to block cave and sub-level cave mining methods, operations haven’t been without their technical challenges. During mining of E26 Lift 2 block cave, a wedge of high grade material failed to cave, even with the assistance of preconditioning. The unrecovered wedge created the E26 SLC, which commenced mining in 2015, with production following in 2016. The SLC provides 1Mt/a to supplement the lowering grade of the current block cave feed. The poor ground conditions in close proximity to the cave have proved a challenge. This was particularly noticeable on the first level, 9740L, with half of the firings including more than one ring. The loss of the brow encountered when blasting in ground that had been initially preconditioned for block cave mining created a heavy reliance on redrills in the operation causing poor drawpoint turnovers. Precharging was researched to improve the flow, however due to prevalence of brow loss; concerns were raised over the inability to hook up the charged ring. In 2018, a wireless initiation trial was completed in the E26 SLC over 24 rings. The trial showed that precharging was achievable in this environment and greatly improved the safety of charge up personnel.

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