Observed Subsidence Progression at New Afton Mine in Response to Lift 1 Mining

Observed Subsidence Progression at New Afton Mine in Response to Lift 1 Mining

Authors: K Davenport, G Dick, C Kamp
Conference: Caving 2022
Date: August 30 to September 1, 2022

ABSTRACT

New Gold’s New Afton Mine is an operating gold-copper block cave mine located 10 km west of Kamloops, British Columbia, Canada. Mining of an initial lift (Lift 1), approximately 600 m below ground and partially beneath the historical Afton Pit, was completed in early 2022. The initial Lift 1 drawbell was blasted in September 2011 and cave breakthrough to the surface was monitored in February 2013. A state-of-the-art subsidence monitoring program has progressively been implemented at New Afton to monitor progression of surface and near-surface deformations in response to mining, including towards critical surface infrastructure.

This paper presents a case study of the observed subsidence progression in response to block cave mining, from initial breakthrough to the end of the Lift 1 production, using examples from the various instrumentation and monitoring techniques used at New Afton. The surface manifestation of deformation was found to be influenced predominantly by mine production rates and the location(s) of underground draw. Additional controls on the expansion of the subsidence zone and the spatial distribution of deformation rates included influence of topography, presence of major geological structures, preferential deformation within comparably deformable Nicola Group geological units, and interaction with the historical Afton Pit. A summary of the use of available instrumentation and monitoring methods and the phased development of New Afton subsidence monitoring system are also presented.

 

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