Experimental Study of Electric Potential Response Characteristics of Different Lithological Samples Subject to Uniaxial Loading

Electric potential (EP) signals are detected when coal or rock materials are subjected to mechanical loading. Such signals are attributed to the generation and accumulation of free charges under externally applied loads. Due to the excellent correlation between EP and damage evolution, EP methods have great potential in rock mass structural engineering damage monitoring. To systematically study the EP response of different materials, four kinds of samples were prepared for experiments. Moreover, the coefficient of variation (CV) and correlation coefficient were introduced to study the EP response characteristics in different loading stages. Furthermore, characterizations based on atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray fluorescence (XRF) were used to reveal the reasons for electrification from a microproperty perspective. The results showed that the EP response characteristics were dominated by the main electrification factors in different loading stages, while these factors were influenced by the microstructure and composition of the different samples. Additionally, crack propagation was a significant mechanism for the EP response, which included electron escape induced by stress concentration at the crack tip, charge separation due to crack propagation, and discharge in the crack tip. Finally, the surface potential was a critical EP generation factor. Different samples were characterized by weak electrical properties in the 5 μm × 5 μm scanning area, and the unevenly distributed surface potential regions can affect the accumulation and migration of the free charges. This study offers new insights into the EP response characteristics and the causes of electrification from macro- and microperspectives.