HANGINGWALL SUBSIDENCE

Large scale surface subsidence has been experienced in Kiirunavaara mine since 1960 when sublevel caving was implemented as the mining method after the open pit operation ended. Today, the mine-induced subsidence is a big concern to LKAB because as mining proceeds surface disturbances on the hangingwall are reaching part of the city of Kiruna, the railway and the power station.

Prognoses of future surface subsidence will require a good understanding of the rock mass properties and behaviour, the failure mechanisms causing the subsidence and details about the distribution of surface deformation. A geological model will be developed together with detailed studies of deformation zones/large-scale structures and the regional stress state. Based on the geological model and the findings in the detailed study of the deformation zones a geomechanical model of the future hangingwall will be developed.

Using the geomechanical model, numerical analyses will be carried out in order to predict future subsidence and identify the failure and deformation modes. Therefore, one of the objectives is to identify suitable numerical methods/programs and how the rock mass has to be discretised to obtain accurate results in the analyses of future hangingwall subsidence.

Tomas Villegas