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<p>To investigate the influence of heating and cooling paths (HCP) on the macro- and micro-properties (MMP) of sandstone, this study examined their relationships in heat-damaged sandstone. Low-field nuclear magnetic resonance (NMR) was employed to assess pore structure characteristics after treatments at 25, 200, 400, 600, and 800 ℃ using different HCPs: fast heat with slow cooling (FS), fast heat with fast cooling (FF), and slow heat with slow cooling (SS). The results show that pore content ratio (PCT) and pore surface area ratio (PAT) increase exponentially with temperature, while peak strength ratio (PST) decreases exponentially. FF has a greater impact on strength degradation than FS or SS. Pore size distribution shows a distinct transition between 400 ℃ and 600 ℃. Below 400 ℃, the cooling mode predominantly influences micropores; above 600 ℃, the heating mode plays a major role, with micropores and mesopores being most affected. Uniaxial compression of sandstone fragments reveals significant fractal properties, with fractal dimension positively correlated with temperature. Finally, PST increases exponentially with pore size distribution entropy ratio (PDET) and decreases exponentially with PAT and fractal dimension ratio (DT), respectively. This study elucidates the impact of HCP on the degradation of MMP and their correlation between microstructure evolution and macroscopic strength in rocks, with implications for the safety evaluation of deep geological engineering.</p>

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Study on the effect of heating and cooling paths on the macro- and micro-properties of red sandstone based on low-field NMR

  • 期刊论文

  • 发表日期：

    2026年4月10日

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  • Shuang Dang,
  • Lin Ning,
  • Jing Bi,
  • Yu Zhao,
  • Yuhang Zhao,
  • Chaolin Wang,
  • Zhongqian Chen

摘要

To investigate the influence of heating and cooling paths (HCP) on the macro- and micro-properties (MMP) of sandstone, this study examined their relationships in heat-damaged sandstone. Low-field nuclear magnetic resonance (NMR) was employed to assess pore structure characteristics after treatments at 25, 200, 400, 600, and 800 ℃ using different HCPs: fast heat with slow cooling (FS), fast heat with fast cooling (FF), and slow heat with slow cooling (SS). The results show that pore content ratio (PCT) and pore surface area ratio (PAT) increase exponentially with temperature, while peak strength ratio (PST) decreases exponentially. FF has a greater impact on strength degradation than FS or SS. Pore size distribution shows a distinct transition between 400 ℃ and 600 ℃. Below 400 ℃, the cooling mode predominantly influences micropores; above 600 ℃, the heating mode plays a major role, with micropores and mesopores being most affected. Uniaxial compression of sandstone fragments reveals significant fractal properties, with fractal dimension positively correlated with temperature. Finally, PST increases exponentially with pore size distribution entropy ratio (PDET) and decreases exponentially with PAT and fractal dimension ratio (DT), respectively. This study elucidates the impact of HCP on the degradation of MMP and their correlation between microstructure evolution and macroscopic strength in rocks, with implications for the safety evaluation of deep geological engineering.