A Review of Resistivity Studies on Commonly Used Soil Materials (Sandy Soil and Clay) in Earth–Rock Dams

Earth–rock dams provide cost-effective flood control and water storage through the utilization of locally available materials, making them essential infrastructure for regional safety, agricultural development, and sustainability. Electrical resistivity methods offer an efficient, non-destructive means to detect internal defects and potential hazards within dam bodies, thereby supporting dam safety assessment and service life extension. In this review, we focus on sand and clay, the most commonly used materials in earth–rock dams. We summarize the main methods and instruments for measuring soil resistivity and comparatively analyze the applicability and limitations of different approaches. Emphasis is placed on the key factors influencing soil resistivity, and recent progress in modeling the resistivity of soil materials is reviewed. The results show that soil resistivity parameters can effectively characterize physical and mechanical properties, structural features, and moisture migration behavior, providing an important basis for soil property evaluation. However, current studies are largely based on macroscopic experiments, with limited investigation of microscopic mechanisms and a lack of unified testing standards, leading to discrepancies between theoretical models and measured data. In this review, we aim to provide a theoretical reference for research and engineering applications of resistivity characteristics in earth–rock dam materials.