Recovery of sill pillars is often associated with mining under existing backfill. The backfill stability in such cases is of primary concern due to risks associated with personnel safety, equipment loss, and ore dilution. Two key aspects that control the stability of exposed backfill are the fill strength and the size of the fill exposure. Use of stronger fill will allow for increased excavation size but will come at a higher cost because of higher binder content requirements. A mine operator, therefore, must decide what combination of excavation size and fill strength is appropriate. In this paper we present the results of a study for a base metal mine in Canada aimed at estimating the strength requirements for cemented rockfill (CRF) being undercut. Numerical simulations utilising bonded particle models were used to relate the size of the undercut to the CRF strength requirements. The results were expressed as the depth of fill failure and as ore dilution, allowing the operator to select appropriate fill strength.
As mines progress to depths for which the induced stress levels exceed the intact strength of the host rock, significant challenges related to rock mass instability must be met. However, given complexity and the scale of orebodies in deep mines, it is increasingly more challenging to predict/pinpoint where and when stress levels will become problematic. Prediction of where and when large scale instabilities will occur continues to be the 'holy grail' of rock mechanics in deep mining. There is no perfect solution; however, there have been a number of technological advancements that greatly helped to develop our understanding of rock mass behaviour and the risks pertaining to deep hard rock mines. It is recognised that at the mine scale, geology and material properties are not fully known, however, using past experience and sound engineering judgment, it is possible to use innovative tools and methodologies to arrive at a reasonable approximation of how a rock mass will behave at depth. The main goal of this paper is to provide an overview of how some of these tools and methodologies have evolved and are actively being applied to the planning of deep mines. Vale Canada Ltd.'s Creighton Mine will be used as a case study to demonstrate how these new techniques have contributed to a better understanding, and hence a better mine planning approach for hard rock mines at depth. https://papers.acg.uwa.edu.au/p/1410_25_Cotesta/ Numerical modelling and scientific visualisationintegration of geomechanics into L Cotesta et al. modern mine designs
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