InSAR Monitoring of Subsidence Induced by Underground Mining Operations

Underground cave and longwall mining can produce subsidence of the ground surface.Mapping of the extent and magnitude of ground movement is usually one of the main challenges faced by mine operators and is important for mine planning, operational hazard assessment and to evaluate environmental and socio-economic impacts.Until now, subsidence prediction was based on complex numerical modelling that typically used a small set of discrete data points as input to calibrate the model.These measurements were both spatially and temporally sparse.The advent of interferometric synthetic aperture radar (InSAR) significantly changed this scenario by providing a high density of measurement points with a high sampling frequency in time.Additional beneficial features of InSAR for mine sites include: (i) the provision of information without the need to install ground instrumentation (no need to access remote or hazardous sites), (ii) the capability to perform historical ground deformation analyses thanks to the existence of data archives going back to the 1990s (worldwide coverage is available from at least May 2016), and (iii) millimetric sensitivity to vertical deformation, which allows accurate characterisation of the areas affected by subsidence.Two case studies of InSAR monitoring applied to underground mining operations are presented, highlighting the advantages of combining different InSAR techniques to monitor both slow and fast movements.