Surface deformation characteristics of shallow buried and rapidly advancing longwall face in Jinjie coal mine

Abstract In high-intensity mining operations in western China, shallow burial depths and rapid advancement rates induce rapid surface responses, significant deformation, and pronounced crack development. This study comprehensively evaluates these effects through full-process rock movement monitoring at the Jinjie coal mine, focusing on subsidence coefficients, mining coefficients, and inflection point trajectories. Results indicate that weak stability of the overlying strata in the shallow-buried working faces led to substantial surface subsidence, with a subsidence coefficient of 0.87, exceeding typical values (0.6–0.7) for conventional mining. The inflection point at the open-off cut followed a monotonic L-shaped trajectory, migrating laterally up to 4.7 times the mining height (15 m), while the inflection point near the roadway stabilized at 5.6–7.5 times the mining height (18–24 m) after two fluctuations. A significant contrast was observed in the horizontal movement coefficient between the goaf area (0.21–0.47) and the unmined area (1.59–2.38). Surface cracks exhibited an O-shaped ring distribution, synchronizing with periodic weighting intervals of 12–14 m; the pressure coefficient was approximately 1.73. Despite pronounced crack development, self-healing mechanisms reduced environmental risks. Full surface subsidence was achieved after the working face had advanced 320 m, a distance approximately equal to 1.24 times the working face length and 3.5 times the burial depth, with the basin areas occupying 48% of the total. Surface stabilization was achieved within 70 days (less than the ratio of burial depth to 100 m), underscoring the necessity of proactive measures such as crack filling to prevent air leakage and water inrush during rapid advancement (20 m/day).