Rock masses typically contain joints and defects affecting their safety and stability under compression, shear, or tension. The shear strength of these discontinuities, influenced by environmental factors like temperature, is critical in deep rock engineering. This study conducted direct shear tests on sandstone joints at room temperature (RT) and after thermal treatment at 250 and 500 . The behavior under compressive and shear forces was investigated by using the direct shear test. The results showed that compressive and shear properties improved at 250 but deteriorated following thermal treatment at 500 . Peak shear strength before and after thermal treatment closely followed Patton's bilinear failure criterion. As intact asperities were sheared under normal stress of 0.75MPa, the residual shear strength was less affected by temperature than peak shear strength. The shear strength of intact asperities increased by 8.8% following thermal treatment at 250 and decreased by 4.3% at 500 . The joint closure, normal stress, and stiffness were consistent with a modified Bandis et al. (1983) criterion. Increasing the thermal treatment temperature from RT to 250 and 500 changed maximum joint closure from 0.201 to 0.125and 0.301 mm, and subsequently, the initial normal stiffness from 8 to 19.6 and 6.62MPa/mm, respectively. These findings offer valuable insights into the temperature-dependent behavior of sandstone joints, aiding the design and maintenance of deep underground structures. This research is particularly relevant to engineering geology, where understanding the thermo-mechanical behavior of rock joints is essential for projects such as geothermal energy extraction and the storage of nuclear waste. The results can improve the safety and efficiency of geological engineering practices in thermally active environments.

中文翻译：

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砂岩节理的热机械行为：直接剪切试验的结果


岩体通常含有节理和缺陷，影响其在压缩、剪切或拉伸下的安全性和稳定性。这些不连续性的剪切强度受温度等环境因素的影响，在深层岩石工程中至关重要。本研究对室温 (RT) 以及 250 和 500 热处理后的砂岩节理进行了直接剪切试验。通过直接剪切试验研究了压缩力和剪切力下的行为。结果表明，压缩和剪切性能在 250 ℃ 时有所改善，但在 500 ℃ 热处理后会恶化。热处理前后的峰值剪切强度严格遵循巴顿双线性失效准则。由于在0.75MPa的法向应力下剪切完整的凹凸体，残余剪切强度受温度的影响小于峰值剪切强度。在 250 ℃ 热处理后，完整凹凸体的剪切强度增加了 8.8%，在 500 ℃ 热处理后降低了 4.3%。关节闭合、法向应力和刚度与改进的 Bandis 等人一致。 （1983）标准。将热处理温度从RT提高到250℃和500℃，最大接头闭合量从0.201改变到0.125和0.301mm，随后，初始法向刚度分别从8改变到19.6和6.62MPa/mm。这些发现为砂岩节理随温度变化的行为提供了宝贵的见解，有助于深层地下结构的设计和维护。这项研究与工程地质学特别相关，了解岩石节理的热机械行为对于地热能提取和核废料储存等项目至关重要。 研究结果可以提高热活跃环境中地质工程实践的安全性和效率。