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<p>This study examines how mining disturbances affect the bearing capacity of interlayer strata during upward mining above pillar goafs. The sandstone from coal-bearing strata was selected as the research subject, and a dynamic uniaxial compression test was performed under the coupling of “low-frequency disturbance + static pre-stress”. The strength degradation rate (SDR) of the sandstone, along with its underlying mechanism, was analysed for various levels of static pre-stress under low-frequency disturbance. The results indicate that: (1) Compared with the uniaxial compressive strength (UCS) of sandstone under pure static loading, sandstone with static pre-stress levels of 20%, 30%, 40%, 50%, 60% and 70% UCS exhibit strength reductions of 8.38%, 3.96%, 1.66%, 0.65%, 1.76% and 4.83%, respectively, after low-frequency disturbances. The SDR in disturbance-damaged sandstone initially decreases and then increases, with increasing static pre-stress levels, exhibiting a quadratic polynomial relationship. The lowest SDR occurs at a static pre-stress level of 48.98% UCS. (2) As the static pre-stress levels increase, the cumulative irreversible strain and energy storage capacity initially decrease and then increase, matching the SDR parabolic evolution trend. (3) The static pre-stress levels corresponding to minimal disturbance damage, as determined by the cumulative irreversible strain, ultimate elastic strain energy density degradation rate and secant modulus increment, are 46.70%, 39.80% and 45.59% UCS, respectively. The disturbance damage deviation, quantified by plastic deformation after disturbance, is the smallest. (4) During low-frequency disturbances, the b-value and proportion of shear fracture evolution trends align with the strength evolution pattern of disturbance-damaged sandstone. At the microscale, damage evolution in sandstone with low static pre-stress levels primarily results from structural adjustments through compaction and primary crack embedding. Conversely, at high static pre-stress levels, disturbance damage is predominantly driven by microcrack initiation from internal fractures.</p>

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Strength Deterioration Mechanism of Sandstone Subjected to Low-Frequency Dynamic Disturbance Under the Varying Static Pre-stress Levels

  • 期刊论文

  • 发表日期：

    2025年9月8日

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  • Xiaoze Wen,
  • Guorui Feng,
  • Jun Guo,
  • Ruipeng Qian,
  • Wenming Feng,
  • Jinwen Bai,
  • Kenan Liu,
  • Xu Zhang,
  • Daniel Dias

摘要

This study examines how mining disturbances affect the bearing capacity of interlayer strata during upward mining above pillar goafs. The sandstone from coal-bearing strata was selected as the research subject, and a dynamic uniaxial compression test was performed under the coupling of “low-frequency disturbance + static pre-stress”. The strength degradation rate (SDR) of the sandstone, along with its underlying mechanism, was analysed for various levels of static pre-stress under low-frequency disturbance. The results indicate that: (1) Compared with the uniaxial compressive strength (UCS) of sandstone under pure static loading, sandstone with static pre-stress levels of 20%, 30%, 40%, 50%, 60% and 70% UCS exhibit strength reductions of 8.38%, 3.96%, 1.66%, 0.65%, 1.76% and 4.83%, respectively, after low-frequency disturbances. The SDR in disturbance-damaged sandstone initially decreases and then increases, with increasing static pre-stress levels, exhibiting a quadratic polynomial relationship. The lowest SDR occurs at a static pre-stress level of 48.98% UCS. (2) As the static pre-stress levels increase, the cumulative irreversible strain and energy storage capacity initially decrease and then increase, matching the SDR parabolic evolution trend. (3) The static pre-stress levels corresponding to minimal disturbance damage, as determined by the cumulative irreversible strain, ultimate elastic strain energy density degradation rate and secant modulus increment, are 46.70%, 39.80% and 45.59% UCS, respectively. The disturbance damage deviation, quantified by plastic deformation after disturbance, is the smallest. (4) During low-frequency disturbances, the b-value and proportion of shear fracture evolution trends align with the strength evolution pattern of disturbance-damaged sandstone. At the microscale, damage evolution in sandstone with low static pre-stress levels primarily results from structural adjustments through compaction and primary crack embedding. Conversely, at high static pre-stress levels, disturbance damage is predominantly driven by microcrack initiation from internal fractures.