Temporal-spatial evolution characteristics of defective coal fracture based on electric potential and multifractal characterization

•The uniaxial compression tests were conducted on defective coal, and AE and EP were tested simultaneously.•The mechanical behavior and failure characteristics of the coal samples were studied.•The AE and EP response characteristics were analyzed.•The temporal-spatial features of the EP multifractal were revealed.•The spatio-temporal characteristics of Δαe and Δf(αe) correspond well with the stress level and local damage. The primary defects in coal are critical factors that induce geological disasters. Accurately predicting and identifying local damage in these defects is essential for the safe mining of underground engineering. In this paper, uniaxial compression tests were conducted on defective coal, and acoustic emission (AE) and electric potential (EP) were tested simultaneously. The mechanical behavior and failure characteristics were studied, the EP and AE features were analyzed, and the temporal-spatial features of the EP multifractal were revealed. The results indicate that external loads significantly stimulate both AE and EP responses in the coal sample, which correlate well with stress changes. As the defect dip angle increases, high-amplitude AE signals gradually decrease, and the main frequency distribution of AEs shifts from a full frequency range to a mid-low frequency range. The EP signals of each channel correspond closely with its corresponding strain evolutions, and the EP signals near the local damage area exhibit regions of high-value abnormal Δαe and low-value abnormal Δf(αe). When macroscopic fracturing occurs, Δαe shows a fluctuating increase, while Δf(αe) shows a fluctuating decrease. The spatiotemporal distribution of Δαe and Δf(αe) corresponds well with the stress levels and local damage in the sample. These research results provide significant theoretical guidance for the early warning and precise identification of geological disasters.