Abstract Mining induced seismicity and rockbursting significantly increased in the LKAB Kiirunavaara Mine when mining production progressed beyond 700 m depth. Since 2008, significant work has been done at LKAB to better understand their induced seismicity. It has been identified that the majority of seismic events in the mine are likely caused by the interaction of mining excavations and structural geology. Two complimentary PhD projects (funded by LKAB) are underway at Luleå University of Technology to address the cause of the seismicity experienced at the mine, with one concentrating on mine seismology and one on rock mechanics. The rock mechanics project, the focus of this paper, concentrates on quantifying relationships between mining sequences, geomechanical and geological conditions, stress changes and induced seismicity at the mine. A series of numerical models will be developed based on an extensive data acquisition campaign to examine the interaction between the mining and geological systems. The role of structural geology in mine behaviour and its application to mine planning is of particular focus within these models. This paper presents the methodology of the rock mechanics project, including: data acquisition, data analysis, and numerical stress analysis models and modelling techniques.
Introduction LKAB's Kiirunavaara Mine, located in Kiruna, Sweden, is a large scale, iron ore, sublevel caving operation. The mine produces 28 million tonnes of crude ore per annum from 10 geographically defined production areas along the strike of the orebody, termed blocks. The productions blocks are named from the (strike-oriented) y-coordinate approximately at the centre of the block. The current main haulage level is at 1045 m, which is approximately 800m below the ground surface.
The orebody, illustrated in Figure 1, consists mostly of magnetite and is approximately 4.5 km long. The width of the orebody varies from a few meters up to 150 m, but averages around 80 m. The dip ranges from 50° to 70°. The orebody is open at depth, with a delineated depth of approximately 1100 m. The footwall consists mostly of trachyte and the hangingwall consists mostly of rhyodacites. Geological structures, including discontinuities (both fractures and faults) and dykes exist throughout the ore and host rock.