Differentiating Clayey Soil Layers from Electrical Resistivity Imaging (ERI) and Induced Polarization (IP)

Abstract

Electrical Resistivity Imaging (ERI) method is one of the most promisingtechniques which is well suited for the applications in the fields of geohydrology,environmental science and engineering. The present work is aimed to show theefficiency of 2D Electrical Resistivity Imaging (ERI) and Induced Polarization (IP) inprobing the subsurface soil for site investigation and differentiating the clayey soillayers as it is a common practice to measure the IP sounding along with resistivity forcorrect interpretation of field data. The study has demonstrated the practicalapplication of 2D ERI and IP tomography along 7 lines using Wenner- Schlumbergerarray. The data analysis comprises of 2D inversions using the RES2DINV software,thus 2D electrical resistivity and IP imaging sections have been obtained. The depth ofinvestigation was 4 m, and resistivity values range from <1 to 292 ohm.m. Twoelectrical layers were recognized: the upper layer with high resistivity (7-71 ohm.m)represents the loamy soil extends to a depth around 1.3 m; and the second layer withlow resistivity (<1-9 ohm.m) represents the clayey layer. Some anomalous low andhigh electric zones are appeared reflecting the inhomogeneity in deposits. The IPvalues are ranging from -2 to 17 mV/V showing good confirmation with resistivitydata, where high chargeability are associated with low resistivity. The study revealsthat combining IP with resistivity surveys is recommended since IP is, sometimes, veryeffective in relieving ambiguity in interpretation.