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<p>Static cracking agents (SCA), as potential substitutes for explosives, can be used to rapidly fragment coal seam rocks. In order to optimize the fracturing effect of SCA and reduce the cost of engineering applications, this study uses PFC<sup>2D</sup> to construct a numerical model of static expansion loading, simulating the rock fracturing process caused by SCA and evaluating the effects of different borehole factors on static cracking effectiveness. The results show that the stress increase phase of the static cracking reaction is the key stage leading to rock failure, the resulting weakened zone around the cracks induces structural damage in the surrounding rock, while stress concentration at the crack tip promotes crack propagation and ultimately leads to block separation. Static cracking performance improves with larger borehole diameter and depth, and smaller borehole spacing under the plum blossom-shaped arrangement with a stress unloading surface. Based on the multi-objective optimization model for evaluating fracturing benefits, the optimal parameter combination—hole diameter of 41&#xa0;mm, hole depth of 2160&#xa0;mm, and hole spacing of 390&#xa0;mm—was determined using the response surface method. Field engineering practice and application indicated that under the optimal borehole parameters, the rock integrity was significantly disrupted, and the cracking performance was satisfactory. The advance distance of the working face per day increased from 2.4 to 3.2&#xa0;m, i.e., by 33.3%.</p>

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Evolution law of static expansion-induced cracking and borehole parameter optimization in coal measure hard rocks

  • 期刊论文

  • 发表日期：

    2025年8月4日

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  • Wei Zhang,
  • Feili Yang,
  • Linchao Cao,
  • Jingyu Chang,
  • Shengxun Zhao,
  • Jinfeng Mao

摘要

Static cracking agents (SCA), as potential substitutes for explosives, can be used to rapidly fragment coal seam rocks. In order to optimize the fracturing effect of SCA and reduce the cost of engineering applications, this study uses PFC2D to construct a numerical model of static expansion loading, simulating the rock fracturing process caused by SCA and evaluating the effects of different borehole factors on static cracking effectiveness. The results show that the stress increase phase of the static cracking reaction is the key stage leading to rock failure, the resulting weakened zone around the cracks induces structural damage in the surrounding rock, while stress concentration at the crack tip promotes crack propagation and ultimately leads to block separation. Static cracking performance improves with larger borehole diameter and depth, and smaller borehole spacing under the plum blossom-shaped arrangement with a stress unloading surface. Based on the multi-objective optimization model for evaluating fracturing benefits, the optimal parameter combination—hole diameter of 41 mm, hole depth of 2160 mm, and hole spacing of 390 mm—was determined using the response surface method. Field engineering practice and application indicated that under the optimal borehole parameters, the rock integrity was significantly disrupted, and the cracking performance was satisfactory. The advance distance of the working face per day increased from 2.4 to 3.2 m, i.e., by 33.3%.