To prevent the occurrence of excavation face instability incidents during shield tunneling, this study takes the Bailuyuan tunnel of the ‘Hanjiang-to-Weihe River Water Diversion Project’ as the engineering background. A three-dimensional discrete element method simulation was employed to analyze the tunneling process, revealing the displacement response of the excavation face to various tunneling parameters. This led to the development of a risk assessment method that considers both tunneling parameters and geological conditions for deep-buried shield tunnels. The above method effectively overcomes the limitations of finite element method (FEM) studies on shield tunneling parameters and, combined with the Analytic Hierarchy Process (AHP), enables rapid tunnel analysis and assessment. The results demonstrate that the displacement of the excavation face in shield tunnel engineering is significantly influenced by factors such as the chamber earth pressure ratio, cutterhead opening rate, cutterhead rotation speed, and tunneling speed. Specifically, variations in the chamber earth pressure ratio have the greatest impact on horizontal displacement, occurring predominantly near the upper center of the tunnel. As the chamber earth pressure ratio decreases, horizontal displacement increases sharply from 12.9 mm to 267.3 mm. Conversely, an increase in the cutterhead opening rate leads to displacement that first rises gradually and then rapidly, from 32.1 mm to 121.1 mm. A weighted index assessment model based on AHP yields a risk level of Grade II, whereas methods from other scholars result in Grade III. By implementing measures such as adjusting the grouting range, cutterhead rotation speed, and tunneling speed, field applications confirm that the risk level remains within acceptable limits, thereby verifying the feasibility of the constructed assessment method. Construction site strategies are proposed, including maintaining a chamber earth pressure ratio greater than 1, tunneling speed not exceeding 30 mm/min, cutterhead rotation speed not exceeding 1.5 rpm, and a synchronous grouting range of 0.15 m. Following implementation, the tunnel construction successfully passed the high-risk section without any incidents. This research offers a decision-making framework for shield TBM operation safety in complex geological environments.

Tunnel construction in weak and fractured strata often faces risks such as tunnel face instability and large deformation of surrounding rock, which are difficult to effectively control using conventional support methods. Based on the engineering background of the No. 8# TA Tunnel in the F3 section of Georgia’s E60 Highway, this study employed ADECO-RS and developed a 3D numerical model with finite difference software to simulate full-face tunnel excavation process. The influence of advanced reinforcement measures on the stability of the surrounding rock was systematically investigated. The control effectiveness of different advanced reinforcement schemes was evaluated by comparing the displacement field, stress field, and plastic zone distribution of the surrounding rock under three conditions: no support, advanced pipe roof support, and a combination of pipe roof and glass fiber bolts. A comprehensive quantitative analysis of the synergistic effect of the combined reinforcement was also performed. The results indicated that significant extrusion deformation of the tunnel face and vault settlement occurred after excavation. The pressure arch developed within a range of 17.5 to 22 m above the tunnel vault. The surrounding rock of this tunnel was classified as type B (short-term stable). Deformation primarily occurred within one tunnel diameter ahead of the face, with the deformation rate significantly reduced after support. Advanced pipe roof support effectively restrained surrounding rock deformation, while the combination of advanced pipe roof and glass fiber bolts delivered better performance: reducing final convergence by 73.10%, pre-convergence by 82.69%, and face extrusion by 87.66%. The combined support also contracted the pressure arch boundaries from 17.5 to 22 m to 6–12.5 m, reduced the extent of major principal stress deflection, and significantly shrinks the plastic zone. Glass fiber bolts played a key role in controlling plastic zone expansion and ensuring stability. This study provides theoretical and numerical references for safe construction and advanced support design in tunnels under complex geological conditions.