Electrical Resistivity of Freezing Clay: Experimental Study and Theoretical Model

Abstract

Electrical resistivity of soil has become one of the most important indicators of compactness and compressive resistance. In previous studies, the temperature of soil tested was always above 0 °C. However, due to the phase change of pore water, the resistivity of freezing soils is different from that of unfrozen soils. Therefore, it is necessary to clarify the influence of temperature on electrical resistivity. To achieve this goal, according to the bundle of the cylindrical capillary model, pores in soil were treated as conducting tubes, and two simple lognormal functions were introduced to describe the distribution of the conducting tubes. Based on the conductivity theory, a new model considering the temperature and the pore size distribution was presented. Results show that only a part of the conducting tubes can be treated as the effective conducting tubes, which are determined by the soil temperature. Furthermore, a small portion of the pores with the smaller size controlled the electrical resistivity of the freezing clay. In other words, the change in the electrical resistivity of freezing clay was caused mainly by the change of unfrozen water content through the decrease in temperature. Based on the experimental results conducted on clay from Northeast China, the validity of the presented model was verified. The comparison results indicate that there was a good agreement between the calculated results and the experimental results. To expand the scope of the model, more laboratory tests are suggested to conduct to verify the applicability of the model to other clays.

A Capillary Bundle Model for the Electrical Conductivity of Saturated Frozen Porous Media

“…These methods allow to characterize the spatial distribution of the electrical parameters (electrical conductivity, SP and so on) in a fast and non‐invasive manner. Recently, these electrical and electromagnetic methods have gained a strong interest in the field of permafrost, frozen porous media as well as snowmelt infiltration, for example, to characterize the thaw layer thickness dynamics (e.g., Dafflon et al., 2013; Duvillard et al., 2018; Murton et al., 2016; Pedrazas et al., 2020) or to measure the liquid water content in frozen porous media (Coperey, Revil, Abdulsamad, et al., 2019; Ming et al., 2020; Oldenborger & LeBlanc, 2018). For instance, the zeta potential is very sensitive to the temporal evolution of snow porosity, pH and meltwater flux, which is important in snowmelt and liquid water‐ice phase change systems.…”

“…In response to this shortcoming, the third type includes the capillary bundle models of electrical conductivity of frozen porous media, which consider either a variable PSD or the physical properties of the solid surface-liquid water interface. Recently, Ming et al (2020) calculated the liquid water content in frozen soils by establishing the cylindrical capillary electrical conductivity model from a mathematical point of view. Even if the impact of PSD on electrical conductivity is considered, this model does not consider the influence of surface conductivity at the solid surface-liquid water and bulk ice-liquid water interfaces in frozen porous media, and the physical relationship between electrical conductivity and basic soil properties such as porosity, liquid water content, permeability or cation exchange capacity remains unclear.…”

Causes and Characteristics of Electrical Resistivity Variability in Shallow (<4 m) Soils in Taylor Valley, East Antarctica

“…Moreover, pore sizes are small in fine‐grained sediments and the growth of miniscule ice crystals developing in such confined spaces during freezing is hindered by thermodynamic surface effects (Dash, 1989). Consequently, laboratory freezing experiments on fine‐grained sediments show that small amounts of liquid water persist down to at least −20°C and that the electrical resistivity of such sediments remains relatively low (Ming et al., 2020). For these reasons, we interpret that increasing soil conductivities in all three transects are due to increases in solute contents and fine‐grained sediment fractions.…”

Geophysical Observations of Taliks Below Drained Lake Basins on the Arctic Coastal Plain of Alaska

“…Furthermore, Figure 8b shows that the depth to the top of a talik can be shallower if the freezing point depression is 2 °C. Recent studies based on laboratory measurements of the resistivity response during freezing of porous media showed that above 0 °C, the bulk resistivity is controlled by the pore water resistivity which increases with decreasing temperature, and below 0 °C, the bulk resistivity depends on the unfrozen water content and its resistivity (Herring et al., 2019; Ming et al., 2020). This evidence suggests that TEM measurements can detect partially unfrozen saline pore water in remnant taliks, since electrical current can flow through very small pore spaces.…”