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.

中文翻译：

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不同岩性样品单轴加载的电位响应特性试验研究

当煤或岩石材料受到机械载荷时，会检测到电势 (EP) 信号。这种信号归因于在外部施加的负载下自由电荷的产生和积累。由于EP与损伤演化之间的良好相关性，EP方法在岩体结构工程损伤监测中具有巨大的潜力。为了系统地研究不同材料的 EP 响应，制备了四种样品进行实验。此外，引入变异系数（CV）和相关系数来研究不同加载阶段的EP响应特性。此外，基于原子力显微镜 (AFM)、扫描电子显微镜 (SEM)、和 X 射线荧光 (XRF) 被用来从微观特性的角度揭示带电的原因。结果表明，EP响应特性受不同加载阶段的主要带电因素支配，而这些因素受不同样品的微观结构和成分的影响。此外，裂纹扩展是 EP 响应的重要机制，包括裂纹尖端应力集中引起的电子逃逸、裂纹扩展引起的电荷分离和裂纹尖端放电。最后，表面电位是一个关键的 EP 生成因素。不同样品在 5 μm × 5 μm 扫描区域的电学特性较弱，不均匀分布的表面电位区域会影响自由电荷的积累和迁移。这项研究从宏观和微观角度提供了对 EP 响应特性和带电原因的新见解。