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<p>Coal burst has become the predominant dynamic hazard in deep coal mines. To mitigate this risk, a whole-layer pre-fracture pressure relief technique has been proposed for the hard roof strata of high-level key layer prone to inducing bursts, which can be implemented through deep-hole blasting. After pre-fracturing, fractured rock blocks encapsulated by intact rock masses are formed within the roof. To simulate these conditions, fractured-intact composite rock (FICR) specimens were prepared, and uniaxial compression tests with acoustic emission (AE) monitoring were conducted. The mechanical properties of FICR were analyzed using uniaxial compression results combined with strain difference theory, while AE data provided further insight into failure mechanisms. Numerical simulations were also performed to examine internal failure characteristics. Results show that the compressive strength and elastic modulus of FICR specimens first decrease and then increase with particle size, and the dominant failure mode shifts with increasing size. Medium-sized FICR specimens with particle sizes of 6–8&#xa0;mm display the greatest plastic deformation capacity, with enhanced energy absorption and buffering ability during the post-peak stage. By contrast, specimens with particle sizes of 2–4&#xa0;mm and 10–12&#xa0;mm tend to brittle failure or rapid instability, characterized by abrupt energy release and limited capacity for sustained absorption. This study demonstrates that there exists an optimal particle size for FICR, which can effectively enhance plastic deformation capacity and energy dissipation during compression, thereby providing guidance for selecting the optimal pre-fracture block size in deep coal mines to improve pressure relief efficiency.</p>

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Study on the Mechanics, Energy Absorption, and Crack Characteristic of Fractured-intact Composite Rock Based on High-level Whole-layer Pre-fractured Layer

  • 期刊论文

  • 发表日期：

    2026年1月6日

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  • Xinyu Gao,
  • Xianjie Hao,
  • Huaixiang Yang,
  • Yijia Li,
  • Hang Li,
  • Fule Chu,
  • Jinyi Ji

摘要

Coal burst has become the predominant dynamic hazard in deep coal mines. To mitigate this risk, a whole-layer pre-fracture pressure relief technique has been proposed for the hard roof strata of high-level key layer prone to inducing bursts, which can be implemented through deep-hole blasting. After pre-fracturing, fractured rock blocks encapsulated by intact rock masses are formed within the roof. To simulate these conditions, fractured-intact composite rock (FICR) specimens were prepared, and uniaxial compression tests with acoustic emission (AE) monitoring were conducted. The mechanical properties of FICR were analyzed using uniaxial compression results combined with strain difference theory, while AE data provided further insight into failure mechanisms. Numerical simulations were also performed to examine internal failure characteristics. Results show that the compressive strength and elastic modulus of FICR specimens first decrease and then increase with particle size, and the dominant failure mode shifts with increasing size. Medium-sized FICR specimens with particle sizes of 6–8 mm display the greatest plastic deformation capacity, with enhanced energy absorption and buffering ability during the post-peak stage. By contrast, specimens with particle sizes of 2–4 mm and 10–12 mm tend to brittle failure or rapid instability, characterized by abrupt energy release and limited capacity for sustained absorption. This study demonstrates that there exists an optimal particle size for FICR, which can effectively enhance plastic deformation capacity and energy dissipation during compression, thereby providing guidance for selecting the optimal pre-fracture block size in deep coal mines to improve pressure relief efficiency.