Authors: Moulding, CR; Stephenson, RM; Barsanti, BJ; Francis, DD

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Moulding, CR, Stephenson, RM, Barsanti, BJ & Francis, DD 2017, 'Managing the onset of accelerated deformation in capital development at Agnew Gold Mine', in J Wesseloo (ed.), Deep Mining 2017: Proceedings of the Eighth International Conference on Deep and High Stress Mining, Australian Centre for Geomechanics, Perth, pp. 937-948,

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The Kim Lode at Waroonga Underground (Agnew Gold Mine) extracts ore using a longhole open stoping method. The orezone dips west at approximately 65° and predominantly lies between a sandstone hanging wall contact and an ultra-mafic footwall. The Waroonga Underground has recently seen an increase in levels of deformation associated with squeezing ground conditions, including bulging of the shoulders, walls and floor heave. This is commonly experienced in the oredrives during ore extraction. However, this type of deformation has since begun to migrate into capital long-term development in the lower levels of the mine, including the access drives and decline. This paper describes the methods of observations, monitoring, modelling, short and long term management methods used at Waroonga Underground for safe production 1,180 m below surface. The driving mechanisms of the squeezing ground conditions can be attributed to large and small-scale structures, rock mass strength, rock stress orientation, mine design, and the stoping sequence. The majority of the ground deterioration is between the Thresher and Spinner faults in the southern access drives. The rock mass between these faults and the orezone creates a ‘triangle’ of accelerated ground squeezing (within 24 hours of blasting). These mechanisms are discussed in relation to the results of non-linear numerical modelling and analysis using damage mapping. The damage mapping was used to identify areas requiring upgraded ground support leading to a proactive approach to ground control. The overall aim is to develop a better understanding of potential damage in relation to structures at depth, and improve future planning of capital development location and orientation relative to the orezone.

Keywords: accelerated ground squeezing, ground support

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