Geophysical SurveysGeophysical surveys involve investigation of the subsurface using non-invasive methods. Typically this involves collection of measurements followed by analysis and interpretation. This enables characterisation of the subsurface and subsurface features. The progress and development of Geophysical survey methods have made them increasingly suitable for adaptation and use in engineering. Sandberg uses a number of Geophysical techniques for engineering and construction applications. The most common being: Ground Penetrating Radar
Ground Penetrating Radar offers a unique non-invasive and non-destructive means for the characterisation of the subsurface and subsurface features. Ground Radar can be used on a wide variety of materials, most commonly soil, concrete and asphalt. The following lists some of the more common applications:
Electromagnetic (EM) conductivity
Based on the principles of inductive electromagnetics, and with no requirement for soil-to-instrument contact, EM surveys offer a rapid survey technique. The instruments have a response that is comparable to that of resistance meters (conductivity is the inverse of resistance) however, unlike resistance meters, EM meters respond strongly to metal. This can be an advantage when the target is metallic, but surveys can be affected by extraneous metallic objects. EM surveys are suitable for:
Resistivity
Ground Resistivity measures lateral and vertical variations in the electrical resistivity of the subsurface. Metal probes are inserted into the ground to obtain readings of the local electrical resistance. Sandberg uses systems with 32, 64 or 128 electrodes. A computerised control unit automatically controls the automatic measurement and logging of all the permutations between the electrodes. Resistivity surveys are suitable for:
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