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Interaction Mechanism of the Upper and Lower Main Roofs with Different Properties in Close Coal Seams: A Case Study

Author

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  • Shengrong Xie

    (School of Energy and Mining Engineering, China University of Mining & Technology, Beijing 100083, China)

  • Yiyi Wu

    (School of Energy and Mining Engineering, China University of Mining & Technology, Beijing 100083, China)

  • Fangfang Guo

    (School of Energy and Mining Engineering, China University of Mining & Technology, Beijing 100083, China)

  • Dongdong Chen

    (School of Energy and Mining Engineering, China University of Mining & Technology, Beijing 100083, China)

  • En Wang

    (School of Energy and Mining Engineering, China University of Mining & Technology, Beijing 100083, China
    Department of Civil Engineering, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada)

  • Xiao Zhang

    (School of Energy and Mining Engineering, China University of Mining & Technology, Beijing 100083, China)

  • Hang Zou

    (School of Energy and Mining Engineering, China University of Mining & Technology, Beijing 100083, China)

  • Ruipeng Liu

    (School of Energy and Mining Engineering, China University of Mining & Technology, Beijing 100083, China)

  • Xiang Ma

    (School of Energy and Mining Engineering, China University of Mining & Technology, Beijing 100083, China)

  • Shijun Li

    (State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China)

Abstract

Close-distance coal seams are widely distributed in China, and the mining of overlying coal seams leads to floor damage. To grasp the properties and the fracture spans of the damaged main roof in the underlying coal seam, combining the calculation of the floor damage depth with rock damage theory and the formulas for calculating the first and periodic weighting intervals of the damaged main roof and the instability conditions of the damaged key blocks are obtained. Three interaction stability mechanics models are proposed for key blocks with different properties of the upper and lower main roof, and the instability conditions of the lower damaged key blocks are obtained when the fracture lines overlap. When combined with a specific example, the field monitoring verified the calculation results. The research results are as follows: (1) The first and periodic weighting intervals, horizontal thrust between blocks, and critical load of instability of the damaged main roof are significantly reduced. Still, there are differences in its reduction under different loads, rotation angles, and lumpiness. (2) When the fracture lines of the upper and lower main roofs overlap, the stability of the damaged key blocks is the lowest. There are three linkage stability regions in the critical load curves of the two key blocks. (3) In this case, the damage equivalent of the main roof is 0.397, which belongs to the local damage type. Its first and periodic weighting intervals are 40 m and 16 m, which is 22% and 24% less than when there is no damage. (4) A supporting load of 0.489 MPa is required to maintain the stability of the upper key block, and the lower damaged key block is prone to rotary and sliding instability during the first and periodic weighting, respectively. Thus, the supports need to bear a total of 0.988 MPa and 0.761 MPa to maintain the stability of the two key blocks simultaneously. The ground pressure data monitored on-site is in accord with the calculation results.

Suggested Citation

  • Shengrong Xie & Yiyi Wu & Fangfang Guo & Dongdong Chen & En Wang & Xiao Zhang & Hang Zou & Ruipeng Liu & Xiang Ma & Shijun Li, 2022. "Interaction Mechanism of the Upper and Lower Main Roofs with Different Properties in Close Coal Seams: A Case Study," Energies, MDPI, vol. 15(15), pages 1-21, July.
    • Handle: RePEc:gam:jeners:v:15:y:2022:i:15:p:5533-:d:876153
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    References listed on IDEAS

    as
    1. Chunyuan Li & Jianping Zuo & Yue Shi & Chunchen Wei & Yuqing Duan & Yong Zhang & Hong Yu, 2021. "Deformation and fracture at floor area and the correlation with main roof breakage in deep longwall mining," Natural Hazards: Journal of the International Society for the Prevention and Mitigation of Natural Hazards, Springer;International Society for the Prevention and Mitigation of Natural Hazards, vol. 107(2), pages 1731-1755, June.
    2. Feng Cui & Chong Jia & Xingping Lai & Yanbing Yang & Shuai Dong, 2020. "Study on the Law of Fracture Evolution under Repeated Mining of Close-Distance Coal Seams," Energies, MDPI, vol. 13(22), pages 1-20, November.
    3. Weidong Pan & Shaopeng Zhang & Yi Liu, 2020. "Safe and Efficient Coal Mining Below the Goaf: A Case Study," Energies, MDPI, vol. 13(4), pages 1-15, February.
    4. Dongdong Chen & Xiaoyu Wu & Shengrong Xie & Yanding Sun & Qing Zhang & En Wang & Yaohui Sun & Long Wang & Hui Li & Zaisheng Jiang & Xiaowei Wu, 2020. "Study on the Thin Plate Model with Elastic Foundation Boundary of Overlying Strata for Backfill Mining," Mathematical Problems in Engineering, Hindawi, vol. 2020, pages 1-15, March.
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    Cited by:

    1. Dongdong Chen & Jingkun Zhu & Qiucheng Ye & Xiang Ma & Shengrong Xie & Wenke Guo & Zijian Li & Zhiqiang Wang & Shaohua Feng & Xiangxiang Yan, 2023. "Application of Gob-Side Entry Driving in Fully Mechanized Caving Mining: A Review of Theory and Technology," Energies, MDPI, vol. 16(6), pages 1-26, March.
    2. Fulian He & Bingquan Liu & Deqiu Wang & Dongdong Chen & Yanhao Wu & Liming Song & Xiang Ma & Qiucheng Ye & Zaisheng Jiang & Fangfang Guo & Weiguang Wang & Yiyi Wu, 2022. "Study on Stability and Control of Surrounding Rock in the Stopping Space with Fully Mechanized Top Coal Caving under Goaf," Energies, MDPI, vol. 15(22), pages 1-22, November.

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