Additional Information
Applications
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Resistivity
 Recent advancements in resistivity imaging systems and techniques have greatly expanded practical applicability of the method to a wide range of subsurface problems and objectives. It is becoming an effective and dependable tool for everyday use in environmental and engineering applications where increased knowledge about the subsurface is sought.
Some of the most common applications include:
- depth to bedrock
- voids and cavities
- mapping lithology (i.e. sand lenses)
- isolated ore bodies
- faults
- prospecting for sand, gravel
- groundwater studies
- mapping pollution plumes
- locating leakage from landfills
- locating seepage through dams
- minerals exploration
- slope stability studies
The intrinsic properties of soil or rock that affect their resistivity are porosity, water content, composition, salinity of the pore water, and grain size distribution. Resistivity measurements or soundings are made with instruments that apply electrical current to the ground surface, typically through two electrodes. Two or more additional electrodes are used to measure variations in the electrical field induced by the current electrodes. Multi-electrode systems are becoming widely used employing 28 or more electrodes and a recording instrument capable of electronically switching the electrodes. Field surveys are conducted to map the variation of resistivity with depth, reflecting the horizontal stratification of earth materials; and to map lateral variations in resistivity that may indicate soil lenses, isolated ore bodies, faults, or cavities. The data are analyzed with a 2-D or 3-D forward inverse modeling computer program. In the program, a non-linear least-squares optimization technique is used to automatically determine the best fit to the data. Examples of a two dimensional electrical resistivity cross-sections are shown in the Figures below.
 Resistivity Profiling
Sample 2D resistivity inversion section profile for slope stability analysis project in volcanic region. The section shows acute features near the slope edge. Subsequent drilling confirmed the presence of heavily weathered volcanic rock, leached of conductive minerals,along with a near surface path.
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