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