Application of ground resistivity surveying in subsurface characterization

Abstract

Geophysical methods have become instrumental in ground exploration as these techniques offer non-invasive and efficient means to investigate subsurface conditions without the need for extensive excavation or disruption. Ground electrical resistivity is a geophysical method which can be used for subsurface profiling in addition to borehole investigations. With the recent improvements to the resistivity surveying instruments, 2D and 3D profiling can be done and 2D profiling can be done up to a maximum depth of 100 m. However, lack of reliable correlations with ground resistivity and subsurface properties have been identified as a major drawback for implementing this method in many investigation projects. This study was based on correlating borehole data with ground electrical resistivity. For that, borehole data from several sites were used and ground electrical resistivity surveys were conducted at the same locations in order to get borehole data and resistivity values of the same locations and depths. The results were analyzed by categorizing the data according to rock type. Five major rock types were considered in this study. After the analysis, variation of core recovery, RQD and weathering grade with the variation of ground electrical resistivity have been identified for five major rock types and the results were presented graphically. For Lugeon analysis, reliable results were obtained only for Calc Gneiss. With the graphically presented results, subsurface properties can be predicted if rock type and ground electrical resistivity is known.