Developments in monitoring mine slope stability using radar interferometry

The authors describe a new ground based radar system which utilises differential interferometry to detect changes in rock surfaces in open cut mines. The aim is to detect small precursor movements of the rock slope which often occur prior to collapse, allowing the estimation of rock slope stability. A ground based system gives a unique opportunity to investigate the accuracy of radar interferometry for bare rock surfaces, as unlike satellite systems, high repeat rates, atmospheric monitoring and ground truthing is now easily achieved. Data collected from field trials at two open cut coal mines (Drayton, NSW Australia and Moura, QLD Australia), demonstrates that after compensation for atmospheric effects, sub-millimeter accuracy can be obtained over distances of 70-150 meters using the Slope Stability Radar (SSR). The two remaining sources of errors are fretting or weathering of the surface and dielectric changes of the rock surface, primarily due to rain. Through these tests the SSR is shown to be more accurate than current reflectorless laser EDM systems at detecting changes in a rock surface.