## 7 Conclusions  
This paper investigated the mechanism of TBM jamming in fault zones during excavation, focusing on fault-fractured zones in a water conservancy project in Xinjiang. The study aimed to identify effective pre-reinforcement measures for surrounding rock to prevent such incidents, considering rock stability, strata displacement, support structure stress, and cost-effectiveness. Using theoretical analysis, numerical simulations (FLAC 3D), and field monitoring, the study concludes that grouting pre-reinforcement at the surface is the most effective measure to prevent TBM jamming, particularly in trench fault zones. While the study's simplification of strata parameter variations may introduce minor errors, these were controlled through displacement indicators, with a final model showing less than 20% discrepancy from field data. Future research should focus on refining the modeling process and utilizing advanced optical measurement technologies to improve accuracy in simulating tunnel excavation conditions. The following conclusions are drawn:  
1. The TBM tunnel jamming mechanism was studied, incorporating tool friction into the jamming theory. Deformation calculation before shield jamming was also analyzed, improving the efficiency of jamming detection. In working condition II (control group), it was identified that jamming occurred when passing through gullies. On-site verification showed that TBM jamming and escape took up to six months, primarily relying on manual excavation of the pilot tunnel in working condition III. 2. By analyzing the distribution of plastic zones under four working conditions, the results show that the plastic zone at the arch waist is deep, particularly under the pipe shed support conditions, where the interface between pre-grouting and soil shows significant plastic deformation. In working condition II, the plastic zone at the arch bottom expands notably. Since a single-layer pipe shed cannot effectively prevent soil collapse in the fault zone, additional support is needed to ensure smooth TBM passage. Condition I improves the support structure's load-bearing capacity and limits fault area damage by using chemical grouting and inclined small conduits. Pre-grouting on the surface results in minimal plastic zone development, with depth significantly lower than in other conditions, indicating a strong reduction in surrounding rock disturbance. The double-layer pipe shed grouting, chemical grouting + shield tail small pipe grouting, and surface pre-grouting reduced rock deformation by 2.12%, 3.97%, and 50.78%, respectively, with surface pre-grouting showing the best results. 3. Surface pre-grouting enhances soil stability, increases strength and stiffness, reduces collapse and deformation risks, and improves soil's physical properties and bearing capacity. This method accelerates construction, boosting efficiency and safety. Three-dimensional numerical simulations show that surface pre-grouting maintains good surrounding rock integrity, with minimal deformation and relative displacement, and effectively controls geological settlement. Therefore, it is an effective technique for fault fracture zones. 4. From an economic perspective, umbrella grouting saves approximately 6.82 million RMB in investment; however, it presents challenges such as extended construction periods, increased technical difficulty, and potential risks, particularly at greater tunnel depths where grouting quality may be compromised and the grouting process is prolonged. In contrast, surface pre-grouting allows for early ground reinforcement before the TBM reaches fault zones, ensuring smooth TBM operation and effectively preventing delays and jamming risks. Considering both economic viability and technical feasibility, surface pre-grouting proves to be more advantageous for tunnel depths of less than 70 m, as it minimizes costs, ensures construction safety, and enhances efficiency.