The effect of kaolinite and illite towards resistivity and chargeability value for groundwater survey

Abstract

The most common method of surveying the groundwater is the Electrical Resistivity Tomography (ERT). Electrical Resistivity Tomography is a non-destructive method of groundwater surveying where the current is being injected into the ground to determine the resistivity and chargeability value. In this study, the effects of minerals and moisture content are assessed by using Abem Terrameter LS 2 connected with soil resistivity box in the laboratory. The materials used in this test are illite and kaolinite mixed with different types of water, which are filter water and groundwater at resistivity value at 96.7 Ωm and 1.88 Ωm respectively. The physical properties for the kaolinite clay samples are 70% and 40% for liquid limit and plastic limit, while for illite were 40% and 22%. The resistivity and chargeability testing were conducted towards the clay sample with 10% moisture increment until the sample reaches its liquid limit or fully saturated condition. The resistivity and chargeability for kaolinite mixed with filter water at 42% and 22% moisture contents were 96 Ωm and 0.2 ms, whereas, when mixed with groundwater at 54% and 51% moisture contents were 4.8 Ωm and 0.29 ms, respectively. Further increase in moisture content across these points causes no substantial changes in resistivity and chargeability value as the value began to plateau. The resistivity and chargeability for illite mixed with filter water at 36% and 34% moisture contents were 36 Ωm and 0.5 ms whereas, the mixture with groundwater at 36% and 22% moisture contents were 4.9 Ωm and 0.8 ms, respectively. At their respective moisture content, the resistivity and chargeability began to plateau. By using filter water with high resistivity value, illite has more influence towards the resistivity value compared to kaolinite, however the low resistivity of groundwater diminishes the effect of mineral towards resistivity and chargeability value.