The purpose of electrical surveys is to determine the subsurface resistivity distribution by making measurements on the ground surface. From these measurements, the true resistivity of the subsurface can be estimated. The ground resistivity is related to various geological parameters such as the mineral and fluid content, porosity and degree of water saturation in the rock. Electrical resistivity surveys have been used for many decades in hydrogeological, mining and geotechnical investigations. More recently, it has been used for environmental surveys. The resistivity measurements are normally made by injecting current into the ground through two current electrodes (C1 and C2 in Figure 1), and measuring the resulting voltage difference at two potential electrodes (P1 and P2). From the current (I) and voltage (V) values, an apparent resistivity (pa) value is calculated.
pa = k V / I
The ground Resistivity tests shall be performed using the two methods (Wenner, and Schlumberger arrays) at depths of 1m,2m and 3m. Ground resistivity shall be measured at work sites in location where the earth electrodes are to be installed. The soil resistivity tests shall be conducted as per ASTM G57-06 .