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Roof Stability and Support Strategies Associated with Longwall-induced Horizontal Stress Changes in Belt Entries

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Abstract

Longwall mining is a highly productive and efficient coal mining method used in the USA. During longwall retreating, the belt entry must be maintained stable, and any roof fall in the belt entry would jeopardize mine safety and substantially interrupt the continuous production of coal in the longwall face. Past experience of longwall mining has shown that belt entry stability was the greatest challenge in longwall ground control, and the occurrence of roof falls in belt entries was largely associated with high horizontal stress. To properly support the roof in the belt entry, it is important to understand how longwall-induced horizontal stress changes affect roof stability in belt entries and to strategically install supplementary support to prevent any potential roof falls. Researchers from the National Institute for Occupational Safety and Health (NIOSH) performed horizontal stress measurements in the immediate roof of the belt entries for two Pittsburgh seam longwall panels oriented unfavorably to high horizontal stress. Hollow inclusion cells (HICells) were installed in the immediate roof at the intersection in each of the belt entries, and stress changes were monitored as the longwall face was approaching and passing the intersection. Numerical models were set up to calculate the longwall-induced horizontal stress changes in the roof at the monitoring sites. With the verified model, investigations were made of how horizontal stress is concentrated and relieved in the belt entry roof near the face under different panel orientations. Both measurements and modeling results showed that high horizontal stress is concentrated in the roof in the belt entry within about 15 m outby the face when a longwall panel is unfavorably oriented to the major horizontal stress. The study demonstrated that longwall-induced differential horizontal stress can be used as an indication of the degree of horizontal stress concentration. Roof support strategies are discussed on how to maintain the stability of belt entry under high horizontal stress concentration.

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Acknowledgements

Data from this manuscript have been presented at the 41st International Conference on Ground Control in Mining, July 27–28, 2021.

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Authors and Affiliations

  1. Office of Mine Safety and Health Research, NIOSH, Washington, DC, USA

    Peter Zhang, Gabriel Esterhuizen, Morgan Sears, Jack Trackemas & Todd Minoski

  2. Department of Mining Engineering, West Virginia University, Morgantown, WV, USA

    Berk Tulu

Authors
  1. Peter Zhang
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  2. Gabriel Esterhuizen
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  3. Morgan Sears
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  4. Jack Trackemas
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  5. Todd Minoski
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  6. Berk Tulu
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Correspondence to Peter Zhang.

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The findings and conclusions in this report are those of the author(s) and do not necessarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention (CDC). Mention of any company or product does not constitute endorsement by NIOSH.

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Zhang, P., Esterhuizen, G., Sears, M. et al. Roof Stability and Support Strategies Associated with Longwall-induced Horizontal Stress Changes in Belt Entries. Mining, Metallurgy & Exploration 39, 1873–1885 (2022). https://doi.org/10.1007/s42461-022-00634-9

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