The electrical resistance of soils and rock varies, depending on their mineral content and exposure to influences such as ground water or contamination. Whiteford Geoservices are experts in this field.
Measurement of variation in the electrical resistivity of the subsurface can yield significant information about the subsurface soils, rock and their relative thickness or strength.
Electrical Resistivity Testing is particularly useful when used for the following purposes:
- Mapping individual layers of soil and bedrock interfaces along linear routes such as road corridors, new cable routes and pipelines
- Determining subsurface variation in ground resistance/resistivity that can be used to aid the placement of exploratory holes ahead of the main ground investigation campaign
- Mapping of groundwater levels within subsurface soils
- Mapping the severity of weathering within the subsurface bedrock topography
- In marine environments 2D electrical resistivity imaging is used to profile sub seabed sediments to identify layer boundaries and aid identification of sediment types. (In a similar manner to seismic studies, but where resistivity is directly related to rock integrity)
The two main types of resistivity survey are as follows:
- 1D Vertical Electrical Sounding (Ground Resistance Testing)
- 2D or 3D Combined Vertical and Constant Sectional Traverse Resistivity Surveying
Seismic surveys are particularly useful in the following scenarios:
- Extrapolating rock and soil interfaces between exploratory holes
- Providing preliminary information with respect to soil type and thickness along new cable and pipeline routes.
- Provision of accurate soil and rock resistivity data to inform the design of earthing systems for reinforced concrete and steel structures