Electrical Conductivity in Soils: Underlying Phenomena

Abstract

Electrical conductivity can be accurately and readily measured in the laboratory and in the field, with minimal electrode effects even in high specific surface soils and∕or high ionic concentration pore fluids. Electrical conductivity combines the contributions of particle conduction, surface conduction and pore fluid conduction, and the effects of particle shape and fabric. The interplay between participating soil parameters is often obscured in typical empirical equations, such as Archie’s law. New experimental results show that surface conduction is an important contributor to global soil conduction in high specific surface soils that are saturated with low-ionic concentration pore fluids; the relevance of surface conduction increases with decreasing porosity. On the other hand, pore fluid conduction prevails as the conductivity of the electrolyte and the porosity of the soil increase. Furthermore, low frequency conductivity anisotropy increases with increasing ionic concentration. Simple yet robust microscale analytical models properly capture the observed interplay between the most relevant soil parameters.

Mechanical and electromagnetic properties of northern Gulf of Mexico sediments with and without THF hydrates

“…Surface conduction effects can be neglected in marine sediments (Klein and Santamarina, 2003). The dielectric permittivity k 0 of soil-water mixtures in the microwave frequency range is dominated by the orientational polarization of free water molecules relative to their volume fraction in the soils.…”

Irreducible Water Saturation from Capillary Pressure and Electrical Resistivity Measurements

“…The effect of surface conductance in a formation can be estimated by adding a surface conduction term to Equation 1 (Klein and Santamarina, 2003;Santamarina et al, 2001). Then, the resistivity of the formation becomes: (2) where Θ is the surface conduction, γ min is the mineral unit weight, g is the acceleration of gravity, and S s is the specific surface of the formation mineral.…”

Laboratory characterization of the spatial variability in soils by the EM-wave-based technique

“…In the pH 6.63 sample, is always greater than one, even larger than four, and has an increasing trend along the depth. This behavior, as suggested by Klein and Santamarina (2003), can be attributed to the fact that the surface conduction via the overlapped double layer overcompensates for the decreased contribution of the fluid conductivity.…”

“…The conductivity of the clay sediment, mix , is the sum of the conductivity in the fluid channel and the contribution of surface conduction, which, under the condition that the electrical field is parallel to the fabric alignment, can be simply described as (Klein and Santamarina 2003) Results of the local dielectric measurements and the local porosities of the kaolinite sample with pH = 4.20: (a) the relaxation strength of bulk water, Áw, and the porosity, n; (b) DC conductivity of the sediment, mix, and the pore fluid, pf, and the ratio, ( = mix/pf). Note that the sediment surface is marked by the horizontal dotted line.…”