Satellite mining-induced subsidence detection: Application of SAR Interferometry to the Kiruna Mine

CIM Montreal 2003
Rott Helmut, Mayer Christoph,
Abstract The Kiruna Mine is a large-scale sublevel-caving operation located in Northern Sweden. The orebody, made of massive magnetite, is more than four kilometres long and dips at 60 degrees towards the town of Kiruna. Hangingwall collapse is intrinsic to the mining method and is characterised by three phenomena: caving above the production levels, major fracturing up to one-two hundred metres from the caving area and deformation, beyond. Deformation is surprisingly high in a hard-rock context and is certainly the most critical parameter due to the proximity of major infrastructures like railroad, roads and houses. Although it is normally followed up by benchmark ground surveys, LKAB tested in 2000-2001 a satellite-based technology called Satellite Aperture Radar (SAR) Interferometry in collaboration with the Innsbruck University, Austria, and Eurimage, Italy. The technique consists in comparing two satellite radar pictures of the same area, taken at different times but with the same incidence angle, to detect ground subsidence caused by anthropic or natural activities. The technology had already been successfully used for ground subsidence monitoring in oilfields, earthquakes and coal mining areas and even to monitor landslides and glaciers. The paper first introduces the mining environment at the Kiruna Mine and details the hangingwall monitoring system with its advantages and disadvantages. SAR Interferometry’s principles are then described and the test results are detailed. The main conclusions were very positives: continuous hangingwall deformation maps were obtained with a centimetre accuracy level that agreed very well with benchmark ground survey data. SAR Interferometry proved to be a powerful technique, with no equivalent for ground coverage (continuous map), no need for ground reference points and the possibility to get retroactive pictures anterior to the installation of the benchmark system. It is moreover low cost. However, its sensitivity to vegetation and snow cover limits its use to low vegetation, urban or barren areas.
Keywords: Satellite, Interferometry, Kiruna, Hangingwall, SAR, Mining, Subsidence
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