To evaluate the stability of fiber-reinforced cemented foamed backfill (FCFB) in complex underground mining environments, this study investigates the synergistic effects of fiber content and modified coal gangue (MCG) under acidic and high-temperature conditions. Through a systematic analysis of hydration processes, compressive strength, and deformation characteristics, the research identifies critical mechanisms for optimizing backfill performance. Calcination of MCG at 700 °C enhances gelling activity via amorphous phase formation, while modified aluminum dross (MAD) treated at 950 °C develops dense α-Al₂O₃ and spinel phases, significantly improving chemical stability. In acidic environments, the suppression of calcium silicate hydrate (C-S-H) is offset by the development of Al³⁺-driven C-A-S-H gels. These gels adopt a tobermorite-like structure, substantially increasing acid resistance. Mechanical testing reveals that while 1% fiber reinforcement promotes nucleation and densification, a 2% concentration hinders hydration. Compressive strength at 28 days shows constrained growth due to pore inhibition, and failure modes transition from multi-crack parallel failure (3-day) to single-crack tensile-shear failure. Under acidic conditions, strain concentration in the upper sample highlights a competitive mechanism between Al³⁺ migration and fiber anchorage. Ultimately, the coordinated regulation of MCG/MAD and fiber content provides a robust solution for roof support in challenging thermo-chemical mining environments.

This study numerically investigates the Mach number influence on the stability limits of stationary curved premixed flames. The numerical study is conducted over a range of realistic Mach numbers and varying channel widths. The results reveal that the stationary flame velocity increases with Mach number, consistent with prior studies. Notably, the study identifies two critical channel widths: (i) Dc, at which the Darrieus–Landau instability first occurs, and (ii) Dw, beyond which the flame velocity surpasses theoretical predictions based on weakly nonlinear analyses and the stationary curved flame velocity grows monotonically with increasing channel width. The second limit b=Dw/Dc is shown to decrease as the Mach number increases. Moreover, the transitions to the asymmetric flame front are observed for nearly isobaric Mach number in wide channels. It is investigated that with the decrease in the Mach number, the stationary curved flame velocity is closer to the analytical prediction.