Characterization of electrical resistivity of silty clay under water−salt interaction

Clarifying the evolution of electrical properties of silty clay under the influence of moisture and salinity is essential for expanding the field application of geotechnical investigation technologies in cohesive soil areas of northern China and improving the accuracy of integrated geophysical exploration methods. Aiming at the demand for electrical characterization in silty clay regions, this study systematically investigates the effects of water-salt interaction on the resistivity characteristics of silty clay. Laboratory tests were conducted on silty clay samples collected from Linfen, Shanxi Province, using a digital bridge instrument over a frequency range of 100～10000 Hz. Water content was controlled between 8% and 18%, and salt content ranged from 0% to 6%. The results show that the soil resistivity decreases exponentially with increasing water content, with an inflection point near the plastic limit. As salt content increases, resistivity first decreases rapidly and then tends to stabilize. Resistivity decreases with increasing frequency, and its sensitivity to salinity is more pronounced under low water content conditions. The observed trends were interpreted based on a solid-liquid-gas three-phase conductive path model and the diffuse double layer structure of clay. The findings provide a theoretical basis for electrical prospecting and electrical parameter identification in silty clay regions, which is of significance for enhancing the precision of resistivity-based geophysical methods.