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.

Artificial neural network and statistical models for predicting the basic geotechnical properties of soils from electrical measurements

“…The equipment employs a four‐electrode technique and measures the real and imaginary parts of the complex resistivity of the samples that are automatically corrected for temperature variations to 25°C. We utilized measured values at 4 Hz based on earlier work (Vanhala ; Boadu and Seabrook ; Boadu and Owusu‐Nimo ) where electromagnetic coupling problems are minimal and the electrical responses are maximum with a high signal‐to‐noise ratio. Furthermore, the resistivity or conductivity as well as the phase shift of rocks and soils are nearly constant at frequencies below 100 Hz (Scott ; Olhoeft ; Vanhala and Soininen ; Borner et al ; Slater and Lesmes ; Seabrook and Boadu ; Schon ).…”

“…( 4) and (5) measured values at 4 Hz based on earlier work (Vanhala 1997;Boadu and Seabrook 2006;Boadu and Owusu-Nimo 2010) where electromagnetic coupling problems are minimal and the electrical responses are maximum with a high signal-to-noise ratio. Furthermore, the resistivity or conductivity as well as the phase shift of rocks and soils are nearly constant at frequencies below 100 Hz (Scott 1983;Olhoeft 1985;Vanhala and Soininen 1995;Börner et al 1996;Slater and Lesmes 2002;Seabrook and Boadu 2002;Schön 2004).…”

Complex resistivity decomposition of the Dias's model in partition fractions applied to electrolyte salinity, clay content and hydraulic permeability determination

“…According to Dias's model (Dias, 1968;1972), the first Ma xwell equation must include a current density ' J → element associated to internal source as (1) in this way, the total current conductivity is given by (2) where E , H , D are electric, magnetic and electric displacement fields, considering steady state condition and time variation as …”

“…4. Applied to Boadu and Seabrook (2006) experimental data, this procedure provided through the Dias model a new methodology to determine the electrolyte concentration and the clay content in rocks samples without disseminated metallics. 5.…”

Estimation of sediment texture from spectral induced polarisation data using cluster and principal component analysis

“…; Weller et al . ), and the amount of clay (Slater, Ntarlagiannis, and Wishart ; Boadu and Seabrook ; Oh, Kim, and Park ; Breede et al . ); fluid properties, such as the total dissolved solids or electrical conductivity (Lesmes and Frye ; Hördt and Milde ; Kavian, Slob, and Mulder a; Ponziani et al .…”