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<p>This study investigates the effects of different cooling methods (water, air, and furnace cooling) and single versus cyclic thermal shocks on the physical, mechanical, and microscopic pore structure of Beishan granite at temperatures from 200&#xa0;°C to 800&#xa0;°C. Heat treatment was conducted using a box resistance furnace, while low-field nuclear magnetic resonance (LF-NMR) was employed to obtain T₂ spectra and pore imaging data. Combined with measurements of macroscopic physical parameters such as mass, volume, density, and P-wave velocity, the evolution behavior of pore distribution and connectivity during thermal damage was analyzed. The results show that increasing temperature raises mass loss and volume expansion while reducing density and P-wave velocity, with changes becoming particularly pronounced above 600&#xa0;°C. The cooling method significantly influences the degree of damage: water cooling, due to its thermal shock effect, most readily induces microcrack propagation, whereas furnace cooling suppresses damage by mitigating thermal stress gradients. Cyclic high-temperature treatment further amplifies thermal fatigue effects, promoting the development and interconnection of fracture networks. This research reveals the damage mechanisms of granite under the synergistic effects of high temperature and cooling from a multi-scale perspective, providing important theoretical support for the development of hot dry rock resources, stability assessment of surrounding rock in deep underground engineering, and long-term safety of nuclear waste geological repositories.</p>

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Study on thermal damage and pore structure evolution of granite under high temperature and different cooling methods

  • 期刊论文

  • 发表日期：

    2026年8月4日

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  • Yingjie Zhang,
  • Chuanqu Zhu,
  • Yanlin Zhao,
  • Lianyang Zhang,
  • Shuailong Lian,
  • Rui Luo,
  • Pei Tang

摘要

This study investigates the effects of different cooling methods (water, air, and furnace cooling) and single versus cyclic thermal shocks on the physical, mechanical, and microscopic pore structure of Beishan granite at temperatures from 200 °C to 800 °C. Heat treatment was conducted using a box resistance furnace, while low-field nuclear magnetic resonance (LF-NMR) was employed to obtain T₂ spectra and pore imaging data. Combined with measurements of macroscopic physical parameters such as mass, volume, density, and P-wave velocity, the evolution behavior of pore distribution and connectivity during thermal damage was analyzed. The results show that increasing temperature raises mass loss and volume expansion while reducing density and P-wave velocity, with changes becoming particularly pronounced above 600 °C. The cooling method significantly influences the degree of damage: water cooling, due to its thermal shock effect, most readily induces microcrack propagation, whereas furnace cooling suppresses damage by mitigating thermal stress gradients. Cyclic high-temperature treatment further amplifies thermal fatigue effects, promoting the development and interconnection of fracture networks. This research reveals the damage mechanisms of granite under the synergistic effects of high temperature and cooling from a multi-scale perspective, providing important theoretical support for the development of hot dry rock resources, stability assessment of surrounding rock in deep underground engineering, and long-term safety of nuclear waste geological repositories.