Strata behavior and advanced control technologies in longwall top coal caving of extra-thick coal seams under hard roofs.

Authors

Yu Guo, Zewei Li, Tukhtaev Bobirjon Isomitdinovich, Yewuhalashet Fissha, N Rao Cheepurupalli, Mengxue Wang, Xiaowei Feng, Bin Du

Published in

Scientific reports. Jul 19, 2026. Epub Jul 19, 2026.

Abstract

The extraction of extra-thick coal seams under hard, massive roofs using Longwall Top Coal Caving (LTCC) can induce dynamic hazards, including large-area roof suspension, intense advanced abutment pressures, and extreme roadway deformation. Taking the 8401 working face of the Tongfa Dongzhouyao Coal Mine as the engineering background, this study systematically investigates the dynamic evolution of overlying strata and proposes a comprehensive stability control strategy. Two-dimensional non-linear numerical simulations using RS2(Phase 2) were conducted to evaluate the spatiotemporal evolution of roof subsidence under different mining-to-caving ratios. The 2D numerical results provide theoretical insights indicating that a 3 + 7 extraction pattern (3 m cutting, 7 m caving) helps balance void space and bulking effects, facilitating progressive energy release and preventing the sudden delayed caving observed in extreme ratios (e.g., 1 + 9 pattern). Furthermore, the numerical models validate that directional hydraulic fracturing effectively pre-weakens the hard sandstone roof, creating a fracture-induced damage zone that forces predictable, controlled caving. To manage the intense mining-induced stresses in the entry, a "horseshoe-shaped" closed combined support system-integrating deep-hole cable bolts and reinforced concrete floor paving-was developed. Field monitoring confirmed the system's efficacy: macroscopic deformation was remarkably suppressed, with roof-to-floor and rib-to-rib convergences stabilized at 290 mm and 210 mm, respectively. Crucially, the support system maintained a residual bearing capacity of approximately 14 MPa in the shallow coal rib, mitigating excessive stress transfer to the deep strata and eliminating the risk of dynamic impact disasters. These findings provide a robust theoretical basis and practical engineering reference for disaster prevention in similar complex geological environments.

PMID:
42472998
Bibliographic data and abstract were imported from PubMed on 20 Jul 2026.

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