Petrophysical approach to electrical properties of loose soils

Abstract

The paper focuses on the relation between geoelectrical characteristics of the soil: resistivity, polarizability and normalized polarizability (ρ, η, Mn) – and its superficial conductivity (SC or σ") using methods of vertical electrical sounding with induced polarization (VES-IP), electric profiling with induced polarization (EP-IP) and frequency characteristic (FC-IP). The authors demonstrate that superficial conductivity can be determined not only from spectral IP data, but also from soil resistivity obtained through petrophysical measurements. In this case normalized polarizability (Mn) is equal to superficial conductivity (SC). Superficial conductivity, in its turn, is proportionate to clay content of the soil. Increasing clayiness reduces hydraulic conductivity. It has been demonstrated that interpretation of EP-IP results benefits from combined study of the plots of three abovementioned parameters (ρ, η, Mn). In the aeration zone, incomplete humidity has a significant effect on geoelectrical parameters of the soil. Petrophysical modelling helps to investigate the impact of humidity.