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<p>The safe and efficient mining of tar-rich coal holds enormous potential for efficient energy utilization in China and worldwide. Understanding the structural degradation characteristics and dynamic response mechanisms of tar-rich coal in a high-temperature environment is crucial for reducing the probability of dynamic disasters. This study examined tar-rich coal from northern Shaanxi, China. Scanning electron microscopy (SEM), computed tomography (CT), and Split-Hopkinson pressure bar (SHPB) tests were performed on specimens heat-treated at various temperatures (25&#xa0;°C, 200&#xa0;°C, 400&#xa0;°C, and 600°C) to investigate the material’s microstructural evolution and macrodynamic behavior. The study documents that tar-rich coal underwent rapid pyrolysis after 418&#xa0;°C. Consequently, surface cracks in tar-rich coal specimens treated at 600&#xa0;°C deepen. This leads to an eightfold increase in porosity and a permeability as high as 87.1%. However, the dynamic tensile and compressive strengths of the heat-treated tar-rich coal degrade significantly during the initial pyrolysis stage at 400&#xa0;°C. The strain rate to strength increase rate is the largest at 600&#xa0;°C during tension and compression. The energy dissipation mechanism under compression load tends to volume crushing and shear slip, while the energy of the splitting test is more focused on producing through-tension cracks, making the absorbed energy during dynamic compression failure 2–3 times that of the absorbed energy during dynamic splitting under the same working conditions. Overall, temperature significantly influences the parameters that directly reflect mechanical properties, while impact pressure influences strength indicators by improving energy absorption. The dynamic damage constitutive model based on the twin-shear unified strength theory provides a good fit.</p>

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Study on Microstructural Degradation Characteristics and Dynamic Mechanical Behavior of Heat-Treated Tar-Rich Coal

  • 期刊论文

  • 发表日期：

    2026年2月6日

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  • Fandong Meng,
  • Qingyu Xie,
  • Yue Zhai,
  • Heinz Konietzky,
  • Zhenmin Luo

摘要

The safe and efficient mining of tar-rich coal holds enormous potential for efficient energy utilization in China and worldwide. Understanding the structural degradation characteristics and dynamic response mechanisms of tar-rich coal in a high-temperature environment is crucial for reducing the probability of dynamic disasters. This study examined tar-rich coal from northern Shaanxi, China. Scanning electron microscopy (SEM), computed tomography (CT), and Split-Hopkinson pressure bar (SHPB) tests were performed on specimens heat-treated at various temperatures (25 °C, 200 °C, 400 °C, and 600°C) to investigate the material’s microstructural evolution and macrodynamic behavior. The study documents that tar-rich coal underwent rapid pyrolysis after 418 °C. Consequently, surface cracks in tar-rich coal specimens treated at 600 °C deepen. This leads to an eightfold increase in porosity and a permeability as high as 87.1%. However, the dynamic tensile and compressive strengths of the heat-treated tar-rich coal degrade significantly during the initial pyrolysis stage at 400 °C. The strain rate to strength increase rate is the largest at 600 °C during tension and compression. The energy dissipation mechanism under compression load tends to volume crushing and shear slip, while the energy of the splitting test is more focused on producing through-tension cracks, making the absorbed energy during dynamic compression failure 2–3 times that of the absorbed energy during dynamic splitting under the same working conditions. Overall, temperature significantly influences the parameters that directly reflect mechanical properties, while impact pressure influences strength indicators by improving energy absorption. The dynamic damage constitutive model based on the twin-shear unified strength theory provides a good fit.