Spatio-temporal analysis and volumetric characterization of interferometric synthetic aperture radar-observed deformation signatures related to underground and in situ leach mining

Abstract

The effect of uranium mining on ground deformation is a relatively unexplored area, especially in terms of surface subsidence related to subsurface ore removal. We use interferometric synthetic aperture radar and spatiotemporal techniques to characterize subsidence signals at the McArthur River underground mine in Canada and the Four Mile in situ leach mine in Australia. We enhance the signal-to-noise ratio of our datasets via time-series techniques and compare results from active periods with results during inactivity to establish a baseline for mining-related signals. We then relate observed surface subsidence to subsurface volumetric strain rates via a voxel parameterization and Bayesian, geostatistical inversion. We use priors on our volumetric strain rates to identify whether these rates are best attributed to ore removal or if additional factors are contributing to subsidence at these sites. We find that the subsidence at McArthur River is best explained by a combination of ore removal and thermal contraction resulting from ground freezing practices. Ore removal via solution extraction alone explains the subsidence at Four Mile, although the localized subsidence pattern and resulting strain rates suggest an intricate combination of sinks and sources in the field, possibly from injection and production well locations and the subsequent flow of solution.