Mine-scale numerical modelling, seismicity and stresses at Kiirunavaara Mine, Sweden

Authors: Vatcher, J; McKinnon, SD; Sjöberg, J Download Paper

DOI https://doi.org/10.36487/ACG_rep/1410_24_Vatcher

Cite As:
Vatcher, J, McKinnon, SD & Sjöberg, J 2014, 'Mine-scale numerical modelling, seismicity and stresses at Kiirunavaara Mine, Sweden', in M Hudyma & Y Potvin (eds), Deep Mining 2014: Proceedings of the Seventh International Conference on Deep and High Stress Mining, Australian Centre for Geomechanics, Perth, pp. 363-376, https://doi.org/10.36487/ACG_rep/1410_24_Vatcher



Abstract:
LKAB’s Kiirunavaara Mine, located in northern Sweden, has exhibited seismic behaviour since the mining production extended below 700 m depth. Iron ore is mined from the 4.5 km long orebody via sublevel caving at a production rate of 28 m t per annum. The deepest current production level is at approximately 800 m depth, and current mining plans call for mining to about 1,200 m depth. It is thus of critical importance for LKAB to gain a deeper understanding of the stress and rock mass behaviour at the mine. The Kiirunavaara orebody has complex geometry and geology, which is represented using the discontinuum distinct element code 3DEC. As part of a larger series of models investigating the influence of strength and structural geology on rock mass behaviour, the results of multiple continuum models are presented. The goals of these continuum models included: (i) obtain a better understanding of the virgin stress field and redistribution of stresses caused by mining, (ii) further define the extent of mining induced plastic failure; and (iii) increase the understanding of existing failure mechanisms at the mine. The elastic and plastic continuum models accurately produced principal stresses similar to measurements recently conducted at two sites in the mine, confirming the previously estimated virgin stress state. Spatial correlations between plastic failure in the model and seismicity in the hanging wall and footwall were found. However, these correlations were not consistent throughout either material for any evaluated set of material properties; either the plastic failure in the footwall or hanging wall corresponded well with seismicity. This may be because a set of rock mass properties which represent rock mass failure at this scale have not been evaluated or that some underlying failure mechanisms causing seismicity are not represented in the models, for example, failure along discontinuities. Some events larger than moment magnitude of 1.2 in the hanging wall, in particular shear source mechanisms events, do not correspond well with plastic failure from the model. These results potentially indicate that geological structures, which are not represented in these models, influence mine behaviour. The improved understanding of input data, rock mass behaviour, and failure mechanisms as a result of these models has a direct impact upon mine excavation design and future rock behaviour investigations, and will be used in the continued research, as well as in mine planning.

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