Theory  

Electrical resistivity is a bulk electric property of all material that shows how strongly it opposes the flow of electric current. The electrical properties of the subsurface vary with the ground material, the presence and saturation level of fluids, and the presence of buried objects. Electrical techniques seek to imaging the distribution of these properties as a function of depth and horizontal distance in 2D / 3D shapes. Measurements of ground resistance are made by introducing an electric current into the subsurface via two metal stakes (current electrodes) planted into the ground. The current passing through the ground sets up a distribution of electrical potential in the subsurface. The difference in electrical potential between two additional electrodes (potential electrodes) is measured as a voltage. Using Ohm’s law, this voltage can be converted into a resistance reading for the ground between the two potential electrodes.

Applications

Geotechnical site Investigations – Stratigraphic mapping – Groundwater exploration –  Mapping and monitoring of groundwater pollution – Determination of depth to bedrock & Buried foundation mapping – Locating sinkholes / cave systems – Locating buried channels – Mapping buried dykes and other ore bodies –  Locating fissures, faults and mineshafts – Locating tunnels and large diameter buried utilities –  Landslide assessments – Soil corrosivity for pipeline assessment – Cross-borehole tomography.