Correlation between electrical resistivity variation and shear failure behaviors of rock joint

The shear behavior of rock joints plays a crucial role in the stability and safety of geological structures such as tunnels, slopes and foundations. However, owing to the inherent stochasticity of joint surface morphology and the complexity of the shearing process, accurately predicting shear failure mechanisms remains a major challenge in geotechnical engineering. To investigate the evolution of contact conditions during joint shearing, this study developed electrically conductive rock-like materials and fabricated jointed specimens with controlled resistivity. Direct shear tests were performed while continuously monitoring the resistivity response. The evolution of contact resistance and the potential distribution across joint surfaces were analyzed to clarify their coupled effects on resistivity variations and their correlation with shear failure modes. The results indicate that the proposed rock-like material exhibits mechanical properties comparable to those of natural sandstone, along with stable and reproducible electrical conductivity. During the initial shearing stage, compaction of the joint surfaces reduces contact resistance, leading to a decrease in bulk resistivity. With increasing shear displacement, joint dilatancy and the shearing-off of sawtooth asperities induce void formation, which alters the potential distribution and results in an increase in resistivity. As shearing progresses, surface wear of the joint further modifies the contact condition, causing a subsequent reduction in resistivity governed by the combined effects of contact resistance and potential redistribution. The resistivity response effectively discriminates among different joint failure mechanisms and captures their progressive evolution under varying undulation angles and normal stress conditions. Moreover, the characteristic resistivity parameter ( Δλ ) exhibits a trend highly consistent with the development of shear strength, indicating a strong coupling between electrical and mechanical responses. These findings provide new insights into the micromechanical processes governing joint shear behavior and demonstrate the potential of resistivity-based monitoring for improved prediction of joint shear failure.