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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/9956

Title: Estimating depth of investigation in electrical resistivity survey from laboratory measurements
Authors: Asare, Albert
Issue Date: 18-Jan-2017
Abstract: The depth of investigation in geo-electrical resistivity surveys is an important physical parameter required to make a reasonable interpretation of the measured apparent resistivity. Even though it is generally agreed that the wider the spread the deeper the investigation, no definite relationship has been established between the depth of investigation and the electrode spread (AB). Different depth factors have been proposed by researchers; the most commonly used is AB/2, proposed by the Schlumberger brothers. However, field observations do not support this. This work is a laboratory study of the depth of investigation in some commonly used electrode configurations in resistivity surveys (i.e. Schlumberger, Wenner and Dipole-Dipole). A rectangular wooden box filled with silty-sand was placed directly on the ground, and the interface between the sand and the natural ground was investigated. The three array types were each used to sound for the interface while varying the depth of sand above the ground. The sounding curves were inspected for points of conspicuous changes in apparent resistivity, which were attributed to the change from the silty-sand to the natural ground surface. Then comparing the known depths of the interface to AB, it was established that for both the Schlumberger and Wenner arrays, the depth of investigation is about 0.26 of AB (i.e.  AB/4). This seems to compare favourably with field data and some of the results obtained by earlier researchers. However, the results from the dipole-dipole test did not appear to show any clear and consistent anomaly for the interface; this could be the result of insufficient dipole separation.
Description: A Thesis submitted to the Department of Geological Engineering, College of Engineering in partial fulfilment of the requirements for the degree of Master of Science, 2016
URI: http://hdl.handle.net/123456789/9956
Appears in Collections:College of Engineering

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