Abstract:

The Kiirunavaara mine has a history of good rock mass conditions and rare problems related to high rock stresses. Therefore the mine does not have a history of large rock mechanical problems. In the second half of 2007 and in the beginning of 2008 a number of seismically induced large rock falls took place. On the 2nd of February 2008 a large seismically induced rock fall took place causing a fatality. The mine has since then been regarded as seismically active and has experienced several larger seismically induced rock falls. The mine went from being non-seismically active to very seismically active when the production proceeded downwards from mining level 878 m to 907 m. This was probably caused by the combination of increa-sing mining depth and a more competent rock mass below 900 m in the mines coordi-nate system. A number of different actions have been taken in order to master the new rock mechanical conditions at the mine:

  • installation of a mine wide seismic system,

  • development of a new rock support system for dynamic loads,

  • a set-up of a structural geology model based on seismic data.,

  • adjusting the standard production sequencing with regard to seismic risk, and

  • developing procedures and criteria for closing down areas with regard to seismic risk.

The main finding of this work is that a mine can go from being a non-seismically active mine to a very seismically active mine in a very short time. In order to be able to continue production in a safe way a number of different actions have to be taken which changes many of the mines esta-blished procedures.

1 INTRODUCTION
1.1 The Kiirunavaara mine

The ore consists of pure magnetite and the mining method applied today is large scale sub-level caving.

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