Site characterization and assessment using the microgravity technique: a case history
M.W. Branston and P. Styles
Journal name: Near Surface Geophysics
Issue: Vol 4, No 6, December 2006 pp. 377 - 385
Info: Article, PDF ( 2.21Mb )
Price: € 30
A microgravity survey was undertaken to investigate the area surrounding the collapse of a river-bank retaining wall. Initial site investigation identified the presence of a void in the immediate area of the collapse. The objective of the geophysical survey was to assess the extent of the identified void and identify any similar features in the surrounding area. Several geophysical techniques were considered but due to the urban environment, the microgravity technique was chosen. Forward modelling using the data from the initial site investigation was undertaken to optimize the survey parameters. The gravity data was processed to the Bouguer anomaly and the terrain effects of the river-channel morphology accounted for. Anomalies identified within the data set have been analysed using the Euler deconvolution method, which has provided estimates of the depth to the top of the anomalous areas. Inversion of the gravity data using the Cordell and Henderson method has provided an image of the 3D extent of the anomalous areas identified. Guided by this information, a secondary invasive site investigation was conducted which confirmed the interpretation of the geophysical results. The combination of a non-invasive geophysical investigation together with selective invasive control has enabled the full subsurface characterization of this site.