The crack coalescence of rocks significantly affects the stability of rock engineering, and extensive studies have been performed on preflawed rock specimens without thermal treatment. However, the fracturing behaviour of preflawed specimens after thermal treatment has not been investigated comprehensively. In this study, three‐flawed sandstone specimens with different flaw inclinations after high‐temperature treatments were tested under uniaxial compression. Photographic, acoustic emission and digital image correlation techniques were used to investigate the crack initiation, propagation and coalescence behaviour. Experimental results show that the peak strength, elastic modulus and peak strain of the three‐flawed specimens were lower than those of intact specimens and that they gradually recovered with increasing flaw angle. The peak strength and elastic modulus first increased and then decreased, whereas the peak strain increased with temperature. Noncoalescence, indirect coalescence and direct coalescence were three patterns observed between the two adjacent pre‐existing flaws. Finally, the mechanism of high temperature in alteration of the mechanical properties of sandstone was revealed through microobservations.

中文翻译：

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高温处理后三缺陷砂岩试件断裂行为的实验研究

岩石的裂缝聚结显着影响了岩石工程的稳定性，并且对未经热处理的预缺陷岩石标本进行了广泛的研究。但是，尚未对热处理后的预伤试样的断裂行为进行全面研究。在这项研究中，在单轴压缩下测试了高温处理后具有不同缺陷倾角的三裂缝砂岩标本。使用照相，声发射和数字图像相关技术研究裂纹的萌生，扩展和聚结行为。实验结果表明，三缺陷试样的峰值强度，弹性模量和峰值应变均低于完整试样的峰值强度，弹性模量和峰值应变，并且随着缺陷角的增加逐渐恢复。峰值强度和弹性模量先增加然后减少，而峰值应变随温度增加。非聚结，间接聚结和直接聚结是在两个相邻的先前存在的缺陷之间观察到的三种模式。最后，通过微观观察揭示了高温改变砂岩力学性能的机理。