Stress Issues at Pajingo Mine

Authors: Whiting, RK Download Paper

DOI https://doi.org/10.36487/ACG_repo/711_10

Cite As:
Whiting, RK 2007, 'Stress Issues at Pajingo Mine', in Y Potvin (ed.), Deep Mining 2007: Proceedings of the Fourth International Seminar on Deep and High Stress Mining, Australian Centre for Geomechanics, Perth, pp. 129-140, https://doi.org/10.36487/ACG_repo/711_10



Abstract:
Newmont Asia Pacific operates the Pajingo gold mine exploiting a series of narrow mineralised quartz veins commonly referred to as the Vera-Nancy system. An underground operation since 1995, the site has recently encountered stress related problems at mining depths of greater than 450 m below surface. Deterioration of conditions at depth include intact rock failure, stress induced wedge failures, minor seismicity and significant damage to reinforcement and hole closures with drilled stocks in advance of the mining front. Specifically, the mine has shown stress conditions and rock mass damage that are difficult to control when using a benching method which retreats to centrally located crosscuts below 450 m. The design for the Jandam mining area was changed from a central retreat extraction method (using a single crosscut access) to a more development intensive end access, centre out mining sequence, designed to minimise stress induced damage. This allowed adoption of a key design modification in the form of an inclined mining front with simultaneous production from multiple mining levels. Successive extraction of individual panels with prescribed lead-lag distances allowed shedding of stress into stope abutments making mining conditions manageable and maximising predictability and productivity. This paper will discuss general stress related issues encountered on site and various strategies used to manage the conditions. It will outline the background leading to the choice of mining methods and operational variations adapted to the traditional sub level benching technique to control stress related problems at Pajingo mine.

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