New Gold’s New Afton Mine ("New Afton") is a 5 million tonne per year operating block cave mine located 8km outside of Kamloops, British Columbia, Canada. The current extraction level is at 615m below surface and the current mining footprint is approximately 800m in length by 120m in width. At its current size, New Afton is one of the smallest producing block caving operations in the world. The ore being mined is a copper-gold porphyry deposit situated within the Iron Mask batholith complex, is bounded by 2 major fault structures and dips near vertically to the south-southeast and plunges southwest. The bulk of the economically viable portion of the deposit is highly jointed and rockmass quality is in the order of 35 - 55 (RMR76, Bieniawski), placing it in a poor to fair classification category. The case study presented here focuses on a single strike drive ("G") located on the southern abutment of the cave. An excavation that has been subjected to numerous rehabilitation operations and campaigns since caving started early in 2012.
The New Afton Mine completed its first drawbell in September 2011. This was after ~17,700 metres of decline access, infrastructure and footprint development. The operation decided on the "El-Teniente" extraction leve l layout of straight-through drawpoint drives, a decision largely made on geotechnical and operational considerations. Employing an advanced undercut method, a fairly aggressive drawbell development and construction schedule was planned and achieved to establish the initial design hydraulic radius to promote steady state caving. This caving strategy allowed the operation to install a number of convergence monitoring stations throughout the entire advanced strike drive development ahead of the cave. This important aspect provided us the ability to monitor ground movement very early on and track progression of rockmass deformation and changes as the cave matured