Failure mechanism and comprehensive countermeasures of the inclined shaft in water-rich fractured strata: A case study

The increasing construction of mountain tunnels crossing water-rich fractured strata, particularly on inclined shafts, presents significant challenges. This research analyzed seven water and mud inrush events that occurred at inclined shaft of Liangwangshan Tunnel. Then, the geological with water innovation detection method was applied to determine the approximate location of unfavorable geology. The failure mode of hydraulic fracturing failure of incomplete impermeable layer was determined with four stages. The fluid–solid coupling numerical model showed that the critical thickness was 5 m, closely matching the theoretical calculation. In addition, the sensitivity of key factors influencing the safety state was also analyzed. Finally, the comprehensive countermeasures were implemented on further construction. Field monitoring results confirmed that the deformation and stress of the surrounding rock were effectively controlled, which can provide guidance for other similar engineering case.