The Detection of Abandoned Mineshafts using GPS and Capacitively Coupled Resistivity Imaging

The re-development of derelict land in the built environment frequently encounters potential geohazards, such as old mine shafts and workings, which pose serious risk to health and safety. Apart from the physical risk to new structures from subsidence, people are also at risk from mine contaminants. Trial pits and boreholes test only a statistically small volume of ground, therefore, a technique is required that is non-invasive and provides ultra-high density volumetric images of the subsurface.

The research underway at the University of Nottingham and the British Geological Survey investigates the integration of single frequency RTK GPS with a novel capacitively coupled resistivity imaging (CCRI) system. Traditional resistivity systems use probes that are inserted into the ground to measure the resistance of the ground to electricity. The CCRI system uses electrodes that are dragged over the surface to do the same. The system is designed to enable the real time positioning and resistivity of the ground to be determined, and hence the spatial characteristics of the ground to be evaluated.

The following paper details the work, and focuses on the research into the integration of GPS with a CCRI system. Precision field trials and results are discussed. Eventually, it is planned that such a system would allow the user to build up a real time sub surface image, and hence allow the user to concentrate the geophysical survey on areas of interest rather than simply conduct the survey on a grid pattern. This will allow the user to take measurements where they are necessary and not waste time and effort taking measurements where they are not needed.