Study on the stability of fully mechanized top-cutting pressure relief au-to-matic roadway formation under the effect of cutting depth

Abstract

Roof‐cutting gob‐side entry retaining in inclined thick coal seams is strongly affected by the depth of pre‐split roof cutting and the asymmetric movement of overlying strata. Taking the 1703 working face of Hongling Coal Mine in Anyang, Henan Province as an engineering case, this paper investigates the influence law of roof‐cutting depth on surrounding‐rock stability by combining field observations, theoretical analysis, FLAC3D numerical simulation and field monitoring. Field observations of the original 14 m roof‐cutting scheme reveal severe roof subsidence of 1.2–1.6 m together with damage to support components. A three‐stage mechanical analysis framework is established to interpret the action mechanism of roof‐cutting depth before, during and after roof caving. Since the available analytical conditions cannot yield a unique quantitative optimization function, the theoretical analysis is mainly adopted to reveal the directional effects of roof‐cutting depth on stress transfer, roof‐block rotation, goaf support and time‐dependent deformation. Comparative FLAC3D numerical simulations were carried out for 14 m and 20 m roof‐cutting depths. The peak lateral abutment pressure decreases from 26.8 MPa to 22.6 MPa; the roof displacement drops from 307 mm to 179 mm, representing a reduction of 41.7%; and the solid‐coal‐rib displacement falls from 370 mm to 191 mm, with a reduction of 48.4%. Field monitoring indicates that the 20 m scheme produces a lower peak anchor‐cable load (366.2 kN for the 20 m scheme versus 382.1 kN for the 14 m scheme), and the average hydraulic‐support pressure is reduced by 48.5%. Therefore, under the geological and support conditions corresponding to this study, the 20 m scheme achieves better surrounding‐rock control performance than the 14 m scheme. The 20 m depth is a recommended effective value specific to this mining area.