Northparkes E26 L1N block cave progress to date

Authors: Snyman, L; Webster, S; Flynn, M Download Paper

DOI https://doi.org/10.36487/ACG_repo/2435_O-09

Cite As:
Snyman, L, Webster, S & Flynn, M 2024, 'Northparkes E26 L1N block cave progress to date', in Daniel Johansson & Håkan Schunnesson (eds), MassMin 2024: Proceedings of the International Conference & Exhibition on Mass Mining, Luleå University of Technology, Luleå, pp. 1344-1358, https://doi.org/10.36487/ACG_repo/2435_O-09



Abstract:
Northparkes underground operations consist of E26 sub-level cave and E48 Lift 1 and the E26 Lift 1 North block caves. Two open-cut mines blend with underground ore in the processing plant to produce a copper and gold concentrate. E26 block cave mining began in 1997, and the ability to extend cave footprints and utilise existing infrastructure has provided continual ore and value, along with several technical challenges. The E26 Lift 1 North block cave extraction level and undercut wraps around the historic E26 L1 block cave. Development commenced in 2019, and extensive re-design occurred due to the variable ground conditions of the existing cave and historic development around the footprint. The undercut start-up sequence against the existing cave commenced in a post-undercut form to overcome substantial pillars between historical development, then shifted to an advanced undercut as the pillars reduced to an acceptable size. We present the finding of the inclined saw-tooth undercut design, which allowed a reduction in the undercut development drives, reducing the duration and cost of the construction. The production phase commenced in early 2022, and construction was completed five months early compared to the feasibility study. The cave extension geometry amongst existing infrastructure and the overlying subsidence crater made L1N cave growth a unique cave during its cave establishment and breakthrough, posing monitoring challenges. This paper looks at the progress of the cave from feasibility study, construction, cave establishment and essential considerations for monitoring the growing cave through to full production.