I. D. Brunton

Factors influencing overbreak in the Barkers orebody, Kundana Gold mine: narrow vein case study

Abstract A detailed analysis of stope performance data from the narrow vein Kundana Gold mine in Western Australia has been made using the extended Mathews stability graph method and comparative statistics. For these Kundana stopes, a poor correlation was found between stope stability and both the Mathews stability number N and hydraulic radius HR. Given that both N and HR correlate well with stability in the vast majority of Mathews method case histories, this suggested that there is an overriding influence on stability at Barkers not accounted for in the Mathews method. Drill and blast issues were isolated as the most likely cause of this poor correlation. Blast pattern was found to have a statistically significant effect on overbreak. In terms of the drill and blast patterns used at the mine, the inline pattern performed significantly better than both the ‘staggered’ and ‘dice-5’ patterns for the vein geometries at the time. Undercut footwalls were found to behave in a similar manner to non-undercut hangingwalls. There was no evidence that backfill abutments behave differently from solid rock abutments in terms of determination of stable stope dimensions. Drillhole accuracy was indirectly examined by considering the effect of stope heights within the limits of 13–20 m. Within these limits, stope height did not affect the magnitude of overbreak.