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<p>To address the cyclic loading-unloading effects induced by mining disturbances on adjacent coal masses and the resulting coal strength degradation, uniaxial compression tests and CT-based 3D reconstruction were conducted on typical hard coal from western China under varying numbers of cycles. The results show that, as the number of cycles increases, the area of the plastic hysteresis loop in coal samples significantly enlarges, internal damage continuously accumulates, and the uniaxial compressive strength exhibits a marked decreasing trend. Compared with uncycled specimens, the coal strength decreased by 2.44%, 10.29%, and 23.06% after 5, 10, and 20 cycles, respectively. CT scanning reveals that, after 20 cycles, the total internal fracture volume increased by 8436% and the total area increased by 7924%; fracture propagation and coalescence are identified as the primary mesoscale cause of strength degradation. Based on damage mechanics theory, a stress–strain damage model incorporating the attenuation coefficient λ and the cycle number N was established. The model predictions agree well with the experimental curves. The findings provide theoretical support for evaluating coal mass stability in mining-influenced zones, designing protective seam mining, and preventing coal and rock dynamic disasters in deep coal mines.</p>

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Deterioration law of hard coal strength under cyclic static loading

  • 期刊论文

  • 发表日期：

    2026年6月30日

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  • Bo Xue,
  • Chen Wang,
  • Yan Shang,
  • Yuting Zhang,
  • Yongfeng Jia

摘要

To address the cyclic loading-unloading effects induced by mining disturbances on adjacent coal masses and the resulting coal strength degradation, uniaxial compression tests and CT-based 3D reconstruction were conducted on typical hard coal from western China under varying numbers of cycles. The results show that, as the number of cycles increases, the area of the plastic hysteresis loop in coal samples significantly enlarges, internal damage continuously accumulates, and the uniaxial compressive strength exhibits a marked decreasing trend. Compared with uncycled specimens, the coal strength decreased by 2.44%, 10.29%, and 23.06% after 5, 10, and 20 cycles, respectively. CT scanning reveals that, after 20 cycles, the total internal fracture volume increased by 8436% and the total area increased by 7924%; fracture propagation and coalescence are identified as the primary mesoscale cause of strength degradation. Based on damage mechanics theory, a stress–strain damage model incorporating the attenuation coefficient λ and the cycle number N was established. The model predictions agree well with the experimental curves. The findings provide theoretical support for evaluating coal mass stability in mining-influenced zones, designing protective seam mining, and preventing coal and rock dynamic disasters in deep coal mines.