Application of ground penetrating radar to geological investigations

Ground penetrating radar data have been collected from a number of sites in order to investigate the shallow sub-surface. The purpose was to investigate, through active participation, the benefit that GPR can have to elements of the BGS Core Programme and to explore ways that GPR can be used more widely in the future. Field data were collected mainly with a 250 MHz Noggin GPR system manufactured by Sensors and Software Limited, but some additional data were also collected using frequencies of 50 and 100 MHz. Good results were achieved for mapping fractures, characterising an aggregate deposit and for locating infrastructure including, tunnels, voids, steel reinforcing bars and capping for a mineshaft. The use of new equipment that collects data rapidly was found to be especially useful for creating three-dimensional blocks of data. Three-dimensional displays enable artefacts in the data to be identified and for the true dip of structures to be measured. Surveys were less successful when characterising chalk and estimating the thickness of buried channels where the depth of the channels was found to be too deep for high frequency GPR. GPR is a powerful tool for investigating the shallow sub-surface when used in the appropriate environment. It is therefore important that BGS Programme Managers and project leaders should be aware of the potential of GPR and be prepared to utilise it when devising new projects. This is most likely to be achieved through active consultation with geophysicists during the planning phase of a project.