Effects of Clay Content and Salinity on the Spectral Electrical Response of Soils

Abstract

The spectral electrical responses [Formula: see text] of sand and clay mixtures subjected to an effective stress of [Formula: see text] and saturated with varying concentrations of NaCl are measured in a laboratory environment in the frequency range [Formula: see text]. Changes in clay content and fluid concentrations result in characteristic changes in amplitude and phase spectra. The equivalent circuit model due to Dias is used to characterize the spectral electrical behavior of the saturated mixtures. Two circuit elements of Dias model, the electrochemical parameter [Formula: see text], and the dimensionless parameter [Formula: see text], are particularly sensitive to the amount of clay and the concentration of the pore fluid. The electrochemical parameter [Formula: see text] is shown to increase significantly with an increase in clay content when the soil sample is saturated with freshwater. The dimensionless parameter [Formula: see text] on the other hand is directly related to the concentration of the pore fluid solution (NaCl), increasing with an increase in fluid concentration. Effects of electrode polarization on the [Formula: see text] measurements are modeled and minimized by addition of a Warburg diffusion element term to the equivalent circuit model of the sample.