InSAR monitoring of subsidence induced by underground mining operations

Abstract

Subterranean activities such as underground mining and tunnel excavations can produce extensive subsidence of the ground surface, which in severe cases can have serious consequences. In mining, excessive subsidence can lead to blocks in production and safety issues while in urban tunneling contexts it can lead to stoppages, damage to above-ground structures and extensive project delays. The timely mapping of the extent and magnitude of surface movement is usually one of the main challenges faced by geotechnical managers in these cases. The instrumentation used for monitoring surface deformation has generally been based on conventional survey techniques (total stations, levelling, GPS, extensom-eters), which provide spatially sparse measurements. The advent of satellite SAR Interferometry (InSAR) significantly changed this scenario by providing wide coverage and high density of accurate information without the need to install ground instrumentation. It is also possible to assess historical deformation by processing satellite data archives going back to the early 1990s. Furthermore, recent advances in processing algorithms have significantly reduced computational time and the advent of newer satellites with increased spatial resolution and acquisition frequency have increased information density. Near-real time InSAR monitoring is now widely applied in different applications to highlight incipient movements in areas not visible to in-situ instrumentation. Some case studies of InSAR applied to underground mining and urban tunneling will be shown, highlighting the advantages of combining different InSAR techniques to monitor both slow and fast movements.