Characterization and Correlation of Rock Fracture-Induced Electrical Resistance and Acoustic Emission

Understanding the response mechanism of multiparameter rock fractures can improve the accuracy of crack diagnosis. In this study, three types of rock samples with notches were subjected to three-point bending tests. The fracture morphology was observed using scanning electron microscopy, and real-time resistivity and acoustic emission (AE) data were used to describe the crack propagation. The spatial distribution of the electric potential was simulated based on practical crack morphologies and can explain the correlation between rock fracture and rock resistivity or AE. The results reveal that the initiation and propagation of cracks reconstructs the electrical potential distribution characteristics of the rock samples and changed their overall resistivity. The crack growth rate was proportional to the rate of increase in the resistivity rate, and the resistivity increased with nonuniform crack growth. Crack geometry complexity affected circuit connectivity, and a higher resistivity change rate was typically caused by cracks with more uniform propagation. The resistivity variation had the same trend as the fracture toughness, whereas the AE energy exhibited a similar trend to the fracture energy evolution. The cumulative AE count of the granite fracture was the largest, and the peak AE count of coal was larger than that of sandstone. In the main frequency band of 100 ± 25 kHz, a relatively large AE event occurred during crack initiation, and the AE amplitude of granite was the largest. The primary fracture propagation increased the peak AE count, amplitude, energy, and fracture energy release efficiency. During rock fracture, the opening of a microscopic bedding plane and a matrix fracture results in time-varying resistivity and AE characteristics. The complementary electrical and acoustic parameters help describe the details of crack propagation behaviour.