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Mechanisms of the development of water-conducting fracture zone in overlying strata during shortwall block backfill mining: a case study in Northwestern China

  • Yun Zhang
  • Shenggen CaoEmail author
  • Shuai Guo
  • Tong Wan
  • Jijun Wang
Original Article

Abstract

In this work, a shortwall block backfill mining (SBBM) technique is proposed for the recovery of residual corner coal pillars and irregular blocks left behind during the exploitation of coal mines, and a solution is provided for the risks associated with gangue piling and the loss of water resources owing to coal mining. Based on the theory of beams on elastic foundations, a mechanical analysis model was established for calculating the height of a water-conducting fracture zone (WCFZ) in the overlying strata of coal mines exploited using the SBBM technique. It was found that the key factors influencing the development of the WCFZ are the mining height, width of the protective coal pillars, backfill percentage, block length, and number of mining blocks. The relationships between these factors and the height of the WCFZ were obtained by incorporating the relevant parameters in the above-mentioned model. In the field experiment site, it was discovered that the minimum coal pillar width and goaf backfill percentage required to prevent the development of water-conducting fractures that could reach an aquifer are 5 m and 65%, respectively. Based on this result, the protective pillars of the site were designed to be 5 m wide, while the goaf backfill percentage was set as 80%. The borehole fluid method was used to measure the height of the WCFZ, which was found to be 26.8 m. This is consistent with the theoretical calculations (27.0 m) of this study, and thus, validates the reliability of the proposed mechanical model. The findings of this work will improve the recovery rate of residual coal resources in coal mining areas, and they are significant for the refinement of water conservation mining theories.

Keywords

Protection of water resources Shortwall block backfill mining Height of water-conducting fracture zone Beams on elastic foundation 

Notes

Acknowledgements

This research was supported by the Fundamental Research Funds for National Key Basic Research Program of China (2015CB251600).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Yun Zhang
    • 1
    • 2
  • Shenggen Cao
    • 1
    • 2
    Email author
  • Shuai Guo
    • 3
  • Tong Wan
    • 1
    • 2
  • Jijun Wang
    • 3
  1. 1.State Key Laboratory of Coal Resources and Safe MiningChina University of Mining and TechnologyXuzhouChina
  2. 2.School of MinesChina University of Mining and TechnologyXuzhouChina
  3. 3.State Key Laboratory for Geomechanics and Deep Underground EngineeringChina University of Mining and TechnologyXuzhouChina

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