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<p>In extremely thick coal seam mining, residual coal pillars and associated goafs induce asymmetric instability in underlying roadways, leading to severe floor heave disasters. Unlike previous studies that rely on single stress parameters, this study integrates deviatoric stress invariants <i>J</i><sub>2</sub> and <i>J</i><sub>3</sub> with unloading damage mechanics to evaluate roadway stability, where <i>J</i><sub>2</sub> reflects the magnitude of shear stress concentration and <i>J</i><sub>3</sub> identifies the dominant failure mode, distinguishing between compression-dominated and extension-dominated stress states. A theoretical stress model incorporating the combined effects of residual coal pillars and adjacent goafs was developed. Triaxial unloading experiments demonstrated that unloading trajectory, rather than final stress state, controls progressive damage evolution. Numerical simulations of four roadway layouts revealed symmetric Y-shaped high stress zones beneath pillar goaf interfaces, and a coal pillar spanning roadway layout (CPSRL) was proposed with the lowest stress concentration and damage indices. A multilevel support system combining surface shotcrete, deep grouting, and active–passive reinforcement was implemented.</p>

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Asymmetric failure and stability control of roadways beneath residual coal pillars: stress invariant and unloading damage analysis

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2026年7月11日

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  • Zhiqiang Wang,
  • Lu Lin,
  • Peng Wang,
  • Tingzhao Li,
  • Jingkai Li,
  • Andrian Batugin,
  • Xinsheng Gen

摘要

In extremely thick coal seam mining, residual coal pillars and associated goafs induce asymmetric instability in underlying roadways, leading to severe floor heave disasters. Unlike previous studies that rely on single stress parameters, this study integrates deviatoric stress invariants J2 and J3 with unloading damage mechanics to evaluate roadway stability, where J2 reflects the magnitude of shear stress concentration and J3 identifies the dominant failure mode, distinguishing between compression-dominated and extension-dominated stress states. A theoretical stress model incorporating the combined effects of residual coal pillars and adjacent goafs was developed. Triaxial unloading experiments demonstrated that unloading trajectory, rather than final stress state, controls progressive damage evolution. Numerical simulations of four roadway layouts revealed symmetric Y-shaped high stress zones beneath pillar goaf interfaces, and a coal pillar spanning roadway layout (CPSRL) was proposed with the lowest stress concentration and damage indices. A multilevel support system combining surface shotcrete, deep grouting, and active–passive reinforcement was implemented.