Abstract
The extraction of steeply inclined and closely spaced coal seams induces intense strata pressure disasters owing to cross-layer fracturing and collapse, rendering strike longwall fully mechanised mining unsuitable. An innovative horizontal sectional combined mining method with simultaneous coal-rock drawing is therefore proposed. Using the combined mining of the middle coal group at Tianshun Coal Mine, Xinjiang, China, theoretical analysis and numerical simulation were employed to evaluate the effects of sublevel height on the working face safety-production performance. A “mining-induced pressure relief-plastic failure” model for the top coal-rock mass was established, together with the coupled “stress release rate (SRR)-plastic deformation zone index (PDZI)” evaluation index. A three-component decision-making framework, comprising preliminary selection, multi-dimensional evaluation, and economic decision-making was proposed for optimal sublevel height determination. The flow behavior of the coal-rock mass and drawing body morphology distortion under the “subsidence-interlayer leap” effect were investigated. Compared with a single steeply inclined coal seam, the drawing body morphology under coal-rock composite conditions exhibited distorted characteristics: expansion towards the interburden area on the roof side, constriction within the interburden zone, and an upward deflection on the floor side. A multi-cycle intermittent drawing process from the roof side towards the floor side was proposed and validated through industrial trials. Results indicate that at a sublevel height of 25 m achieves optimal balance between pressure relief, plastic failure, and production capacity. Compared with a single steeply inclined coal seam, the drawing body morphology exhibited distorted characteristics: expansion towards the interburden area on the roof side, constriction within the interburden zone, and an upward deflection on the floor side. Industrial trials achieved single-cycle production of approximately 900 t and 85% coal-rock recovery rate, supporting fully mechanised top-coal caving mining of steeply inclined, closely spaced coal seam groups.
Similar content being viewed by others
Acknowledgements
The authors are grateful to the editors and the editorial staff of Scientific Reports for their assistance, and to the anonymous reviewers for their constructive comments and suggestions, which contributed to improving the manuscript.
Funding
This work was supported by the National Natural Science Foundation of China (Grant Nos. 51974230 and 52474149), the Shaanxi Provincial Science Foundation for Outstanding Youth (Grant No. 2023-JC-JQ-42), and the Shaanxi Provincial University Youth Innovation Team Project (Grant No. 2024-CT-1-006).
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
About this article
Cite this article
Wang, H., Bai, J., Jiao, J. et al. Optimal sublevel height and drawing process for horizontal sectional combined mining in steeply inclined, and closely spaced coal seam groups. Sci Rep (2026). https://doi.org/10.1038/s41598-026-52670-w
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41598-026-52670-w
