Effect of Soil Mineralogy and Pore-Water Chemistry on the Electrical Resistivity of Saturated Soils

Abstract

The electrical characteristics of soil-water mixtures reflect the soil type, ionic concentration, surface conduction, fluid saturation, porosity, and pore connectivity of the mixtures. Archie’s law commonly is used to analyze the electrical resistivity measurement results of soil-water mixtures. This paper explores the pore-fluid effect on Archie’s law. Experimental tests were performed on sand and clay specimens to measure the variation in their electrical resistivity at different porosities and for different electrical resistivities of the pore fluid. The results demonstrate that the sand specimens (i.e., low specific surface soil) have a unique Archie’s law curve; however, the clay specimens (i.e., high specific surface soil) have an inconsistent Archie’s law curve owing to the surface conduction induced by the double layer of clay particles. In particular, Archie’s law should be applied and analyzed cautiously when high specific surface soils are subjected to pore fluids with high electrical resistivities (i.e., low electrolyte conductivity).