Knowledge of soil electrical resistivity is necessary when designing the grounding system in an electrical substation or corrosion protection for buried metal structures.

 

In-situ soil resistivity testing is performed using the Wenner (4-Pin) method in accordance with ASTM G57 standard. The method involves four metal electrodes placed with equal separation in a straight line. To obtain the profile of the soil resistivity at various depths the separation between the electrodes is successively increased. The measurements are performed using a resistivity meter able to introduce current into the soil between the outer electrodes and measure the potential drop between the inner electrodes.

 

The measured data are presented in the form of sounding curves – plots of measured apparent resistivity values against electrode spacing in a log-log scale. The data are interpreted using specialized software by matching field sounding curves with theoretical curves. As a result of the interpretation, a multi-layered model representing the variation of electrical resistivity with depth is obtained.

 

Frontwave Geophysics conducts soil resistivity surveys customized to clients’ requirements and performs thorough interpretation of the data including data quality/reliability assessment.

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