Sensitivity study of four-electrode resistivity in soil media

The electrical resistivity of geotechnical media is a key indicator of its conductivity and is influenced by factors such as testing methods (e.g., voltage, electrode depth), sample conditions, mineral composition, particle size and shape, pore structure, water content, pore fluid composition, saturation, and temperature. However, the mechanisms by which soil properties and test configurations affect resistivity, and their interactions, remain insufficiently understood. This study investigates the resistivity of clayey and sandy soils, along with four electrolyte solutions, using the laboratory four-electrode method. The effects of water content, dry density, pore fluid concentration, voltage, electrode depth, particle morphology and size, and media type were analyzed. An orthogonal design combined with range and variance analyses was used to assess factor sensitivity. The linear correlations between electrical resistivity and intra-group factors were also examined. Results show that: (1) in sandy soils, resistivity is most sensitive to pore fluid concentration, followed by water content, dry density, particle size, electrode depth, particle morphology, and voltage; (2) in clayey soils, water content and dry density dominate; (3) across media types, solution concentration has the greatest impact. (4) Finally, through Pearson linear analysis, the linear correlation between the influencing factors is revealed, and the mechanism of state parameter single-factor and multi-factor coupling on resistivity is elucidated. This work supports the development of forward modeling of geotechnical resistivity and its application in engineering evaluation.