Electrical Imaging Techniques For Environmental and Engineering Applications

The development of electrical resistivity imaging techniques has been rapid in the last decade. This applies to data acquisition as well as inverse modelling techniques, and has lead to a greatly expanded practical applicability of the method. A trend today is to move from traditionally used electrode array types towards non-conventional arrays that are more efficient for multi-electrode equipment with multi-channel measuring capability, e.g. multiple gradient array measurements. On the data processing and analysis side robust (L1-norm type) inversion and time-lapse inversion can be mentioned as valuable tools. Resistivity imaging is now becoming widely used in environmental and engineering applications where increased knowledge about the subsurface is sought. Important applications include of groundwater resources mapping and vulnerability studies, contaminant mapping and monitoring, geotechnical pre-investigation, natural resources prospecting, geothermal prospecting, permafrost mapping, leakage detection etc.. Selected examples will be presented. Good quality induced polarisation imaging, using data acquisition equipment that is primarily designed for resistivity imaging, has proved to be feasible on a time and cost efficient basis in some environments. In other environments data quality problems will occur with such equipment in standard configuration. A prime application for IP imaging appears to be mapping and characterisation of buried waste, which is expected to become increasingly important for rehabilitation and re use of areas used as landfills