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<p>Hot dry rock (HDR) is frequently subjected to repeated thermal shock and fatigue damage during geothermal drilling and reservoir stimulation. To simulate these coupled conditions, this study investigates the fatigue mechanical behavior of sandstone following two thermal shocks at 400&#xa0;°C, with a focus on stress–strain characteristics, energy evolution, and damage progression. The results indicate that thermal shock induces a strengthening effect in sandstone, characterized by increased strength and enhanced plasticity compared to the natural specimens. Under fatigue loading, thermal shock specimen exhibits greater plastic deformation and higher energy dissipation. By incorporating wave velocity degradation and energy dissipation as damage indicators, a thermo-mechanical coupling damage model is established to characterize fatigue life under different conditions. Finally, a generalized mechanical model is proposed to effectively describe the coupled failure process of thermal shock and fatigue stress in sandstone. Thermal shock generates a stress gradient characterized by surface tensile stress and internal compressive stress. While the surface tensile stress promotes micro-crack initiation, the internal compressive stress may partially constrain crack propagation. These opposing effects jointly determine the material′s strength behavior.</p>

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Mechanical behavior and damage mechanism of sandstone under the coupling of thermal shock and fatigue loading

  • 期刊论文

  • 发表日期：

    2025年11月8日

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  • Peilei Zhang,
  • Xibing Li,
  • Linqi Huang,
  • Xiaoli Zhou,
  • Jiarong Chen,
  • Jiangzhan Chen

摘要

Hot dry rock (HDR) is frequently subjected to repeated thermal shock and fatigue damage during geothermal drilling and reservoir stimulation. To simulate these coupled conditions, this study investigates the fatigue mechanical behavior of sandstone following two thermal shocks at 400 °C, with a focus on stress–strain characteristics, energy evolution, and damage progression. The results indicate that thermal shock induces a strengthening effect in sandstone, characterized by increased strength and enhanced plasticity compared to the natural specimens. Under fatigue loading, thermal shock specimen exhibits greater plastic deformation and higher energy dissipation. By incorporating wave velocity degradation and energy dissipation as damage indicators, a thermo-mechanical coupling damage model is established to characterize fatigue life under different conditions. Finally, a generalized mechanical model is proposed to effectively describe the coupled failure process of thermal shock and fatigue stress in sandstone. Thermal shock generates a stress gradient characterized by surface tensile stress and internal compressive stress. While the surface tensile stress promotes micro-crack initiation, the internal compressive stress may partially constrain crack propagation. These opposing effects jointly determine the material′s strength behavior.