Rana Gruber operates an underground iron mine, the Kvannevann mine, located 30 km east of Mo i Rana in the northern Norway. The ore body is from 30 to 100 m wide and more than 600 m deep. The host rock is a mica schist. The mine has been in operation for many years using sublevel stoping, and is now changing to sublevel caving. To change mining methods the crown pillar left to support the sublevel stopes will be removed before the sublevel caving can begin. In the western part of the mine the crown pillar has been removed, resulting in caving of the hangingwall. The underground monitoring system will have the two fold purpose of both determining the behaviour of the rock when the cave is opened as well as monitoring the long term stress changes at key locations in the mine. The surface monitoring system will be designed to observe deformations both in the hangingwall and in the footwall. The monitoring system was installed during September 2011. As blasting of the first slots was planned for October 2011 it was of interest to look at the response of the surface and underground monitoring. The long-term doorstoppers so far show a stress change of 1–2 MPa, but show a clear response when major blasting have taken place in the vicinity. The surface monitoring shows no significant development of deformations.
The Kvannevann mine is one of several iron ore deposits mined by Rana Gruber in the Dunderland Valley east of Mo i Rana, and the only underground mine. The ore body is from 30 to 100 wide and more than 600 m deepThe mine has been in operation for almost 25 years using sublevel stoping, and is now changing to sublevel caving.