Interpretation of soil grain size effect on electrical resistivity method

Electrical resistivity method is a non-destructive method to detect the anomalies within the subsurface of the earth that applies the properties of electricity. There are multiple factors that influence the apparent resistivity such as grain sizes, type of soil, and water content. In this study, the effects of particle sizes towards the resistivity and chargeability value are assessed. The size samples are gravel size passing 50 mm and retained at 37.5 mm, 28 mm, 20 mm, 11.2 mm, 6.7 mm, 5 mm and 2.36 mm. Meanwhile, the sand size samples are sample sieve size passing 2 mm and retained at 1.18 mm, 0.85 mm, 0.60 mm, 0.43 mm, 0.30 mm, 0.20 mm, 0.15 mm and 0.063 mm sieve and passing the 0.063 mm are the clayey samples. Abem Terrameter LS2 was used for the electrical resistivity testing. The water used was kept constant throughout the testing with resistivity and chargeability value of 102 omega m and 0.41 ms, respectively. The resistivity values for the fully soaked gravels, sands, silt and clay are in the range of 162 omega m to 37 omega m and the chargeability values ranges from 1.2 ms to 12.31 ms. The changes in porosity causes the apparent resistivity to decreased and for the chargeability value to increase with decreasing particle sizes.