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Numerical simulation on mechanisms of dense drilling for weakening roofs and its application in roof control

密集钻孔弱化坚硬顶板机理的数值模拟及应用研究

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Abstract

This study proposed a method of dense drilling that could induce the formation of a discontinuous surface to weaken the roof. According to the geological conditions of the Chahasu coal mine, a PFC2D numerical model was established to explore the stress response mechanism and crack expansion law around dense drilling. The study found that, after the dense drilling excavation, progressive damage occurred around the boreholes, and then an elliptical pressure relief zone was created concentric with the direction of the minimum horizontal principal stress as the long-axis and the direction of the maximum horizontal principal stress as the short-axis. Meanwhile, the cumulative area ratio of pixels (λ) increased from 0 to 6.42% and the pressure relief zone width ratio (μ) increased from 11.55% to 54.6% when the drilling diameter increased from 30 mm to 133 mm. When the spacing of drilling was increased from 300 mm and 700 mm, λ decreased from 30.86% to 9.74%; μ decreased from 63.9% to 33.2%, which means that larger diameters and smaller spacing are beneficial for pressure relief. Field tests found that the discontinuous weak surface induced by dense drilling effectively improves the roadway stress environment. This study can provide reference and experience for hard roof control in coal mines.

摘要

煤矿坚硬顶板工作面回采后形成的侧向悬臂梁结构导致邻近工作面回采巷道和煤柱处于高应力状态, 使得邻近工作面回采巷道围岩矿压显现剧烈。本文提出了一种密集钻孔诱导形成非连续弱面弱化坚硬顶板的技术方法。根据察哈素煤矿31315 工作面的工程地质条件, 采用颗粒流数值计算软件PFC2D建立了数值计算模型, 研究了密集钻孔周围的应力响应机制和裂缝扩展规律。研究发现, 密集钻孔开挖后, 钻孔周围岩体因受集中应力而出现渐进性破坏并形成以最小水平主应力方向为长轴, 最大水平主应力方向为短轴的椭圆形卸压区。同时, 当钻孔直径(D)由30 mm 增加到133 mm 时, 卸压区面积比(λ)从0 增加到6.42%, 卸压区宽度比(µ)从11.55% 增加到54.6%。当钻孔间距(L)从300 mm 增加到700 mm 时, λ从30.86% 减小到9.74%, µ 从63.9% 减小到33.2%, 表明采用较大的直径和较小的间距能够提高密集钻孔对坚硬顶板岩层的弱化程度及卸压效果。现场工业性试验结果表明, 密集钻孔诱导形成的非连续弱面有效地弱化了顶板岩层的强度, 促进了工作面回采后侧向悬臂结构及时垮落, 优化了巷道围岩所处的应力环境, 保证了工作面生产安全。本研究为煤矿坚硬顶板的控制方案提供了一种新的技术方法。

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Authors and Affiliations

  1. Key Laboratory of Deep Coal Resource Mining (Ministry of Education), China University of Mining and Technology, Xuzhou, 221116, China

    Jun-qiang Ma  (马军强), Xue-hua Li  (李学华), Qiang-ling Yao  (姚强岭), Ze Xia  (夏泽), Qiang Xu  (徐强) & Chang-hao Shan  (山长昊)

  2. Faculty of Mining Engineering, Saint Petersburg Mining University, Saint Petersburg, 199106, Russia

    Jun-qiang Ma  (马军强), Andrey Sidorenko & Aleksei Aparin

  3. School of Mines, China University of Mining and Technology, Xuzhou, 221116, China

    Jun-qiang Ma  (马军强), Xue-hua Li  (李学华), Qiang-ling Yao  (姚强岭), Ze Xia  (夏泽), Qiang Xu  (徐强) & Chang-hao Shan  (山长昊)

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  1. Jun-qiang Ma  (马军强)
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Contributions

MA Jun-qiang completed the numerical simulation and data processing of the paper and wrote the manuscript. LI Xue-hua supervised the research protocol design and data processing of the paper. YAO Qiang-ling knew the field industrial test of the thesis and reviewed the research proposal of the thesis. XU Qiang, XIA Ze and SHAN Chang-hao participated in the industrial experiments, data processing and manuscript revision of the paper. Andrey SIDORENKO and Aleksei APARIN revised the linguistic presentation of the paper and revised the paper. All authors responded to the reviewers’ comments and revised the final version.

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Correspondence to Xue-hua Li  (李学华).

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Conflict of interest

MA Jun-qiang, LI Xue-hua, YAO Qiang-ling, XIA Ze, XU Qiang, SHAN Chang-hao, Andrey SIDORENKO and Aleksei APARIN declare that they have no conflict of interest.

Foundation item: Project(51874285) supported by the National Natural Science Foundation of China; Project(KYCX22_2620) supported by the Postgraduate Research & Practice Innovation Program of Jiangsu Province, China; Project(2022WLKXJ008) supported by the Graduate Innovation Program of China University of Mining and Technology, China; Project (202206420004) supported by the China Scholarship Council

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Ma, Jq., Li, Xh., Yao, Ql. et al. Numerical simulation on mechanisms of dense drilling for weakening roofs and its application in roof control. J. Cent. South Univ. 30, 1865–1886 (2023). https://doi.org/10.1007/s11771-023-5345-1

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