Resistivity Imaging

Service Description

Electrical imaging is a survey technique which makes use of the electrical properties of ground material. The resistivity of a rock or soil depends on the mineral composition, porosity, water content and the water chemistry. Common resistivity values are over 2000 Ωm for crystalline rocks and less than 500 Ωm for clay-rich soil and weathered material with high moisture contents. In the resistivity method, a current is injected into the ground and the resulting potential between a pair of potential electrodes is measured at the surface. The positions of the electrodes are either progressively widened for probing into deeper part of the ground or moved along a traverse for mapping horizontal changes in apparent resistivity. A resistivity measurement system generally consists of a resistivity meter, electrodes and cables. Electrodes are deployed along an array in a certain configuration. Commonly used configurations include Wenner, Sclumberger, dipole-dipole etc. The choice of the configuration used depends on the requirement on resolution and penetration range. Forward or inversed modeling is normally needed for converting the field data into a resistivity model. Commonly used software routines include SOUNDER, RES2DINV and RES3DINV Common Applications (1) determination of rock head depth and weathering grade, (2) marine geophysics survey, (3) metallic mineral explorations, (4) studying slope stability indicators such as clay-rich and enhanced moisture zones, (5) mapping water table, (6) studying groundwater contamination, (7) locating subsurface hazardous zones, (8) determining thickness of retaining walls, and (9) mapping underground cavities

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