Pillar Recovery Adjacent to Stabilised Rockfill at the Ballarat Gold Project

ABSTRACT Remnant rib pillars at Castlemaine Goldfields Ltd.’s Ballarat Gold Project have been sterilised by the placement of loose rockfill in production stopes. The application of selectively injecting low viscosity grout into the backfilled stopes to form a stabilised material has enabled recovery of the previously sterilised pillars. This paper outlines the engineering design, quality control and quality assurance program implemented to ensure the safe and efficient recovery of the rib pillars. The successful program included laboratory testing, numerical exposure stability modelling and in situ monitoring. INTRODUCTION At the Ballarat Gold Project, resources have been sterilised within the Llanberris Compartment due to the placement of loose rockfill adjacent to rib pillars. Potential exists for the recovery of these high grade pillars through injecting low viscosity cement grout into the loose rockfill to form artificial Stabilised Rockfill (SRF) adjacent to the rib pillars. A similar pillar recovery technique has been used to recover sill pillars at the Crusader Mine in Western Australia (Sainsbury et. al., 2007) and Cracow Mine in Queensland (Potts et. al., 2012).