This is one of the geophysical methods of investigation which includes the measurement of physical properties of the ground based on which the type of strata and depth of strata can be approximately evaluated. These tests provide a quick means of getting useful information about the stratification and underground utilities.
This will enable to plan of the depth/extent of the in-situ tests and the type of test to be carried out in situ and in the laboratory. This test is carried out to assess the substrata profiles (that is, soil and rock profiles) over large areas at a relatively lower cost and can thus supplement the information obtained from detailed site investigations.
This test involves placing four electrodes in line along the ground surface and passing an alternating current through the outer two current electrodes and measuring the resulting potential drop between the two inner potential electrodes. From the resistance, calculated as the ratio of the potential drop to the current applied, the apparent resistivity of the substrata (that is, soil or rock strata) is determined by multiplying with applicable factors which are dependent on the geometry and spacing of the four electrodes. The equipment and accessories required for carrying out the test, the test procedure, recording of observations, presentation, and analysis of results shall be in accordance with IS 15736.
