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Coal Engineering ›› 2026, Vol. 58 ›› Issue (1): 76-84.doi: 10.11799/ce202601010

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Surrounding rock control of the retreat roadway during the final mining stage in an ultra-thick coal seam with fully mechanized top coal caving

  

  • Received:2025-07-14 Revised:2025-08-22 Online:2026-01-12 Published:2026-03-04

Abstract:

To address the severe issue of mining pressure manifestation in retreat channel, which arises from improper top-coal retention and inadequate support parameters in the final stage of fully mechanized top-coal caving (FMTCC) mining, a comprehensive study was conducted using field investigation, theoretical analysis, and numerical simulation. The study focused on determining the optimal retreat channel location, un-caving parameters of the top coal, and control measures for the surrounding rock. The main findings are as follows: (1) Retaining a portion of the top coal during the final mining stage effectively reduces the intensity of mining pressure manifestations in the working face. The overlying rock structure, formed when the main roof fracture line is located above the goaf, is most favorable for maintaining the stability of the retreat channel’s surrounding rock; (2) A un-caving distance of 20m ensures sufficient goaf filling, timely main roof fracturing, and pressure relief, thereby representing a rational un-caving top coal distance; (3) Asymmetric support system of anchor cable (Support Scheme VI) effectively establishes a prestressed field connection between the coal wall and the roof of the retreat channel, achieving targeted control of surrounding rock stability based on the principle of differentiated strong–weak support; (4) Field application demonstrates that the combination of a rational top-coal un-caving distance with a scientifically designed support system significantly enhances retreat channel stability, while simultaneously reducing coal resource wastage and mitigating the risk of spontaneous combustion of residual coal.

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