Electric Potential Response Characteristics of Coal Under Stress Wave Loading

Monitoring the electric potential (EP) response induced by coal deformation and rupture is essential to the safety of underground engineering under extreme load and stress wave disturbance conditions. In this study, the split Hopkinson pressure bar and EP acquisition systems were utilized for EP testing of coal under stress waves. The EP response under stress waves was investigated, the changes in accumulated charge caused by each stage of stress wave loading were analyzed, and the mechanism of EP signal generation is discussed. The results show that under stress waves, coal produces a significant EP signal, and the EP fluctuations correspond well to each stage of the stress wave. The EP and stress wave signals have a strong linear relationship when the stress wave is rising. During the descent of the stress wave, the EP decreases exponentially with time, showing a gradual decrease in the rate of EP decrease. The cumulative charge growth at each stage shows a “stable-surging-stable” change trend. Dislocation charged movement causes local polarization within the coal. Crack propagation leads to charge separation and free charge generation. These findings explain the mechanism of EP signal creation caused by stress waves. A mathematical model of the link between charge density and dynamic load stress is derived, indicating a strong positive correlation between the two parameters. The results of this research help to improve the reflection of coal seam stability through the EP response.