Mining operations cause movements in bedrock and affect the surroundings, both below and above ground. As mining proceeds deeper and deeper in the underground mines, the ground and the surrounding communities are affected.
As the iron ore is mined from the rock and brought to the surface, the ground gradually sinks. Mining generates vibrations, ground deformations and movements that are monitored and controlled so that any impacts can be dealt with in plenty of time.
The shape and location of the ore bodies determine where any ground movement will occur and how communities will be affected. In Malmberget, there are around twenty ore bodies that run in a south-westerly direction under the town. Mining takes place in around a dozen of these. In Kiruna, there is just one, huge ore body. The mining operation is gradually moving deeper into the mines and the ground above is being affected.
The Land and Environment Court has determined by how much the ground surface may move by establishing environmental conditions for ground movements. This means that for the area to be inhabited, ground movements must not exceed the maximum permitted measured value. Before this value is reached, the local plans for the area must be changed from commercial and residential areas to industrial areas. No mining is permitted under areas where people live or reside. Therefore, any housing must be moved and the areas converted into industrial areas.
Ground movements are measured regularly
You cannot see with the naked eye that the ground is moving. Accordingly, the mine and the surrounding area are monitored by an extensive system of geophones, which are located underground, and metering plinths placed above ground. Readings from the measurements are important for drawing up prognoses regarding mining and to increase safety in the mine. The results also constitute important data for how ongoing urban transformation can be best implemented.
Measurements are taken twice a year, in May and September, while partial measurements are recorded four times a year. The data is collected and analysed at LKAB and sent to the County Administrative Board and the municipalities. The measurement results determine when an area must be vacated and demolished.
Urban transformations are planned several years ahead. Before the ground surface is affected, i.e. when the area must be redefined as an industrial area, it is still possible to live in the area for some time. It is only once the area has to be fenced off that it is no longer permitted to live there.