Rock fracture and rock instability at high temperatures are serious threats to the safe and efficient exploitation of deep geothermal resources. The electric potential (EP) can provide valuable information to monitor and forecast these issues. In this work, compression-shear failure tests were performed to monitor the EPs of granite samples after thermal treatment at 25 °C, 200 °C, 400 °C and 600 °C. The temporal response and non-extensive statistical characteristics of EPs subjected to different thermal treatments were analyzed. The precursory information of the EPs was studied by exploring the change in Tsallis entropy and variance with the damage variable. The effect of thermal damage on the response mechanisms of EPs was studied using fracture surface scanning, thermogravimetry-infrared radiation (TG-IR) and scanning electron microscopy (SEM) tests. The results show that the thermal treatment affects the EP response by changing the mechanical properties, failure behavior and microstructure. With increasing treatment temperature, the average EP value gradually decreased. The probability density distributions (PDF) of the EPs under different treatment temperatures were consistent with a -Gaussian distribution, and increased with increasing treatment temperature. According to the critical theory, the damage state of samples is reflected by the evolution of and variance based on the EPs and can provide precursory information for instability failure. With increasing treatment temperature, the initial thermal damage becomes more severe, the fractal dimension and roughness of the fracture surface increase, and the unstable propagation of microcracks and precursory points appears earlier.

中文翻译：

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压缩剪切载荷下热损伤花岗岩的电势：响应机制和前兆


高温下岩石破裂和岩石失稳严重威胁深层地热资源的安全高效开采。电势 (EP) 可以提供有价值的信息来监测和预测这些问题。在这项工作中，进行了压剪破坏试验来监测花岗岩样品在 25 °C、200 °C、400 °C 和 600 °C 热处理后的 EP。分析了经过不同热处理的 EP 的时间响应和非广延统计特性。通过探索 Tsallis 熵和方差随损伤变量的变化来研究 EP 的前兆信息。通过断裂面扫描、热重-红外辐射（TG-IR）和扫描电子显微镜（SEM）测试研究了热损伤对EP响应机制的影响。结果表明，热处理通过改变力学性能、失效行为和微观结构来影响EP响应。随着处理温度的升高，平均EP值逐渐下降。不同处理温度下EP的概率密度分布(PDF)符合-高斯分布，并且随着处理温度的升高而增大。根据临界理论，样品的损伤状态通过基于EP的演化和方差来反映，可以为失稳失效提供前兆信息。随着处理温度的升高，初始热损伤变得更加严重，断口的分形维数和粗糙度增大，微裂纹和前兆点的不稳定扩展出现得更早。