## 3 Analysis of the Mechanism of Cutterhead Jamming in Open-Type TBM Traversing Fault Fracture Zones
The radius of rotation of the tool around the rotary axis of the turntable, m.  
The calculated expression for the resisting moment Tb resulting from the friction between the sidewalls of the cutter and the surrounding rock is given by:  
\[T_{b}=\frac{\mu\pi d^{2}b}{8}(f_{1}+f_{2}+f_{3}+f_{4}) \tag{3}\]  
In the equation:  
T\({}_{\text{b}}\): Maximum static friction torque at the edge of the blade. Maximum static friction resistance coefficient at the side edge of the blade. Blade diameter. Blade side edge width. Shield top pressure. Shield bottom pressure. Top lateral pressure. Bottom Lateral Pressure. Figure 2: Diagram of card machine identification process. (Determination of TBM jamming: First, torque parameters are calculated, followed by an assessment of the cutterhead jamming conditions. If the cutterhead torque fails to meet the required criteria, the cutterhead is considered stuck. If the cutterhead is not jammed, the next step is to evaluate the shield for potential jamming. If the shield meets the criteria, the TBM proceeds smoothly; if not, the shield is considered stuck). The expression for the contact friction moment Tc between the blade panel and the palm surface is calculated as:  
\[T_{c}=\frac{\alpha\mu\pi d^{2}}{32}(f_{1}+f_{2}) \tag{4}\]  
In the equation:  
T\({}_{\rm c}\): Maximum static friction moment of contact between the blade panel and the palm surface. The ratio of the area of panels in contact with the surrounding rock. When TBM excavation passes through fault fracture zones, a large amount of fractured rock mass on the face of the tunnel directly contacts the front of the cutter head. Part of the slag that has not entered the opening of the cutter head rotates with the cutter head, and under the axial thrust of the TBM, it rubs against the front of the cutter head, causing a sharp increase in the contact resistance torque Tc in front of the cutter head. When the total torque T applied to the TBM cutter head exceeds its inherent disengement torque, jamming occurs. Establish criteria for TBM jamming state discrimination:  
\[T_{I}=n\mu_{1}rf_{R}<T_{N}\text{ and }T_{II}=T_{a}+T_{b}+T_{c}<T_{M},\text{non- jamming} \tag{5}\]  
\[T_{I}=n\mu_{1}rf_{R}>T_{N}\text{ or }T_{II}=T_{a}+T_{b}+T_{c}>T_{M},\text{ jamming} \tag{6}\]  
In the equation:  
T\({}_{\rm N}\): The maximum torque that can be provided by the TBM tool. T\({}_{\rm M}\): The breakaway torque that can be provided by the rotation of the TBM cutter. As shown in Figure 3, serious machine jamming occurred during the actual excavation process of on-site gully 1. To verify the accuracy of the card machine mechanism, real-time TBM excavation data of Gully 1 in front of the card machine was extracted for research. On-site, manual excavation of pilot tunnels, double-layer advanced pipe sheds, and chemical grouting were used for advanced reinforcement. The specific method is to first set up an advanced pipe shed above the shield, excavate a small guide hole, and then set up another layer of advanced pipe shed above the small guide hole. Subsequently, grouting reinforcement was carried out on the surrounding rock in front of the cutter head and within a range of 5-8 m from the tail of the shield, which took up to 6 months. Figure 3(a) shows the on-site construction drawing of the first layer of the advanced pipe shed and chemical grouting, and the right figure shows the grouting effect after passing. Figure 3(b) shows the second layer of advanced pipe shed grouting for the excavation of the top small guide tunnel, and the right figure shows the grouting effect after passing. Figure 3: Actual photo of the card machine site. As shown in Figure 5, the real-time excavation data of TBM reveals important information, where the red area indicates the warning interval where theoretically, TBM jamming may occur. The red line represents the rated torque and escape torque of the TBM.