ELECTRICAL RESISTIVITY SURVEY
Electrical resistivity tomography is a geophysical technique for imaging sub-surface variation of resistivity value from 2D/3D electrical resistivity survey made at surface
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The Electric resistivity map method is used to map the subsurface electrical resistivity structure, which is interpreted by the Geophysicist to determine geologic structure and / or physical properties of the Geologic material.
Resistivity is the property of material to object the flow of electricity through it. Resistivity of soil depends on its type, stratification, temperature, moisture content, void ratio, chemical composition, presence of metals etc. The resistivity of earth also tells about the probability of rusting in structure and it is important for earthing too. Resistivity is measured in terms of Ohm-m by special testing arrangement.
ERT surveys are highly useful for locating groundwater resources such as potable groundwater to depths of 50m or more. Extent of groundwater contamination can be determined by ERT beyond the limits of an EM survey. Routine applications of ERT surveys include mapping soil/bedrock interfaces, vertical fractures zones, sand channels, sinkholes and void zones.
Electrical Resistivity Survey
A subsurface - Imaging Technique by Vertical Electric Sounding , Electric profiling, Electric Imaging.
- Sinkhole/void locating.
- Mapping of depth to bedrock.
- Groundwater table investigation.
- Mapping of bedrock fracture zones.
- Mapping extents of conductive contaminant plumes.
- Landfill delineation.
- Localize seepage through dams etc.
- Bulk Resistivity of the Sub-surface.
An EM survey is generally completed first in order to locate regions for optimal ERT line placement. ERT lines are then setup by placing a number of equidistant electrodes and then introducing a current. The resulting voltages are measured and converted to resistivity values for processing and plotting. ERT data are collected using a linear array of electrodes connected to a resistivity transmitter/receiver and an electrode control box. The different modes of ERT surveying are profiling, sounding and profiel sounding.
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