Precursory electrical resistivity signatures of shear failure in saturated sandstone under varying shear rates.

To improve the accuracy of monitoring and early warning of rock shear failure, this study investigates the applicability of resistivity monitoring during the incubation stage of shear failure in rocks, with a particular focus on its potential to compensate for acoustic emission (AE) signal quiescence. Direct shear tests were conducted on saturated red sandstone under varying shear rates, during which both resistivity and AE responses were monitored. Digital image correlation (DIC) technology was simultaneously employed to capture surface deformation, enabling a comprehensive analysis of the evolution and precursor characteristics of resistivity and AE signals throughout the shear process. The results indicate that the shear failure process of saturated sandstone can be divided into four stages-compaction, elastic deformation, unstable crack propagation, and residual deformation-corresponding to slight fluctuation, steady decline, sudden drop, and near-constant behavior in resistivity, respectively. At higher shear rates, AE signals are significantly attenuated and enter a quiescent phase, while resistivity continues to decline, suggesting that resistivity effectively captures internal damage evolution during the AE quiescence period. By constructing damage variables based on both resistivity and AE data, the study further confirms the consistency of these two monitoring methods in identifying shear failure. Notably, resistivity demonstrates greater sensitivity and earlier warning capability during the stage of unstable crack propagation. These findings highlight the value of resistivity monitoring as a complementary technique to AE methods, offering a novel approach for the early detection and warning of rock engineering hazards.