Resistivity laboratory measurement of geomaterial

Abstract

Electrical resistivity is usually measured as field survey as it is one of geophysical methods that is currently used in site investigation program for subsurface profiling. Problems in quantifying the resistivity value of geomaterial may possibly contribute to a meaningless data collection for geotechnical assessment. As consequences this technique is less appreciated by engineers as it may be complicated in accepting the interpretation of the resistivity profile of the subsurface. This paper presents finding on experimental study in developing electrical resistivity measurement of geomaterial including soil and rock. The purpose of this laboratory study is to establish a laboratory test method of electrical resistivity measurement using resistance meter or a LCR meter, so then resistivity index of geomaterial can be produced. Due to the objectives of this study, a configuration test was carried out on a group of artificial and real rock samples to obtain an ideal frequency for the geo-material. The tests were performed by connecting the cables to the two current electrodes at the both ends of the sample. The resistivity measurement on homogeneous rock sample (gypsum) at 500 kHz frequency showed a result that the variations in sample thickness do not influence the resistivity value of the material. An ideal moisture content of 56% of the geo-material results a constant resistivity value. As for validation for this laboratory experiment, a field resistivity test was carried out to measure the actual resistivity value on site. By comparing field and laboratory results, this method can be applied to soil and rock material for resistivity index determination.