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Caving mechanisms of loose top-coal in longwall top-coal caving mining based on stochastic medium theory

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Abstract

A good understanding of the caving mechanisms of loose top-coal is significant for longwall top-coal caving (LTCC) mining. In this paper, the equations of the particle motion, top-coal boundary, and drawing body were derived based on the stochastic medium theory. Then, the particles moving boundary and the shape of the top-coal loss were discussed, and the dynamic evolvement of the top-coal boundary and drawing body was analyzed. A theoretical model for calculating the top-coal recovery ratio was established, and the relationship between the top-coal recovery ratio and rock mixed ratio was studied and then the criterion for terminating the drawing cycle was proposed. Finally, model experiments were conducted to verify the theoretical analysis. It is concluded that the starting top-coal boundary keeps moving to the lower left with increasing drawing volume. The top-coal loss is zonal distribution and tilts toward the goaf and is composed of the top-coal surrounded by the floor, the starting top-coal boundary and the ending top-coal boundary between the drawing window and the lowest moving point in the starting top-coal boundary. The drawing body tilts toward the goaf and its deflection angle decreases with increasing drawing volume. The top-coal recovery ratio increases non-linearly with increasing rock mixed ratio, and the rock mixed ratio of 10–15% can be used as the criterion for terminating the drawing cycle. This work is the first attempt at demonstrating the caving mechanisms of the loose top-coal using the stochastic medium theory in LTCC mining.

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Funding

The study was financially supported by the National Natural Science Foundation of China (No. U1361209).

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Authors and Affiliations

  1. College of Mining Engineering, Taiyuan University of Technology, Taiyuan, 030024, Shanxi, China

    Dijie Zhu

  2. Key Laboratory of In-situ Property-improving Mining of Ministry of Education, Taiyuan University of Technology, Taiyuan, 030024, Shanxi, China

    Dijie Zhu

  3. School of Mechanics and Civil Engineering, China University of Mining and Technology, Beijing, 100083, China

    Zhonghui Chen, Lingfan Zhang & Zihan Zhou

  4. State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing, 100084, China

    Weisheng Du

Authors
  1. Dijie Zhu
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  2. Zhonghui Chen
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  3. Weisheng Du
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  4. Lingfan Zhang
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  5. Zihan Zhou
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Corresponding author

Correspondence to Dijie Zhu.

Appendix

Appendix

Top-coal boundary—the boundary between the waste rock and top-coal. The starting top-coal boundary is the top-coal boundary before the current drawing cycle begins, and the ending top-coal boundary is the top-coal boundary after the current drawing cycle being terminated.

Drawn top-coal—the top-coal flowing out from the drawing window during the drawing process.

Drawing body—the original shape of the drawn top-coal and rock.

Drawing volume—equaling the area of the drawing body in the theoretical analysis and the quality of the drawn top-coal and rock in experiments.

Drawing interval—when the current drawing cycle is terminated, the shield support will be moving along the mining direction and the next drawing cycle will begin, the corresponding moving distance is the drawing interval.

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Zhu, D., Chen, Z., Du, W. et al. Caving mechanisms of loose top-coal in longwall top-coal caving mining based on stochastic medium theory. Arab J Geosci 11, 621 (2018). https://doi.org/10.1007/s12517-018-3987-3

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  • DOI: https://doi.org/10.1007/s12517-018-3987-3

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