Abstract
The stability of the roof in coal mining plays a crucial role in ensuring safe excavation. After coal extraction, the roof experiences complex and unbalanced stress conditions, leading to diverse roof failure behaviors, particularly in the case of thick roofs. This study examines the failure behaviors of roofs with different thicknesses through a combination of on-site measurements, physical modeling, and numerical modeling. The on-site results indicate that the failure of thick roof leads to larger magnitudes, increased magnitude variance, and energy compared to thin roof. A self-developed three-dimensional roof fracture experimental platform was utilized to conduct loading experiments on roofs with different thicknesses. The experimental results reveal that roof thickness significantly impacts peak load, deformation characteristics, crack patterns, and acoustic emission (AE) signals. Thin roof failure only generates tensile cracks, while thick roof failure produces both tensile and shear cracks. This suggests that an increase in roof thickness leads to a transition in the roof’s failure mode from pure tensile failure to tensile-shear mixed failure or shear failure. The energy of AE events has a threshold. When below this threshold, more AE events occur for thin roofs, and when above it, thick roofs exhibit more AE events. The digital image correlation (DIC) results and AE location indicate roof failure initiates from the upper surface of the roof, where “O” shaped cracks form around the periphery, followed by gradual development of cracks on the lower surface. Thin roofs exhibit regular “X” shaped crack on lower surface, while thick roofs display additional branching and inflection points based on “X” shaped crack on lower surface. Numerical modeling using four polygonal particle roof models confirms the influence of roof thicknesses on peak load, deformation, and crack distribution, aligning with experimental and on-site results. These findings offer valuable theoretical support for controlling the stability of surrounding rock conditions in the presence of different roof thicknesses.
Highlights
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Roof thickness significantly affects coal mine safety, leading to diverse roof failure behaviors.
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On-site measurements, physical experiments, and numerical simulations reveal insights into roof behaviors.
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An experimental platform was established to explore the correlation between roof thickness and failure behavior.
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Thicker roofs exhibit higher peak loads, reduced deflection, complex crack propagation, and a tensile-shear mixed failure or shear failure.
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Numerical models of polygonal particle roofs further corroborate the impact of roof thickness on failure behavior, offering practical support for coal mine stability.
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All data, models, and codes generated or used during the study appear in the submitted article.
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Acknowledgements
This paper was supported by the National Natural Science Foundation of China (51974320, 51934008, and 52121003), China National Key R & D Program (2022YFC2904001), and China University of Mining and Technology (Beijing) Fundamental Research Funds-Outstanding Innovation Talents among Doctoral Students (BBJ2023007). The authors express gratitude to Dr. Yuan Li from the University of British Columbia and Dr. Yuqi Ren from Shanxi Datong University for their valuable assistance in revising the manuscript. The authors also would like to thank the journal editor and anonymous reviewers for their insightful suggestions.
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Yang, S., Yue, H., Li, Q. et al. Study on Failure Behaviors of Roofs with Varying Thicknesses in Longwall Coal Mining Working Face. Rock Mech Rock Eng (2024). https://doi.org/10.1007/s00603-024-03850-5
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DOI: https://doi.org/10.1007/s00603-024-03850-5