## 3 Analysis of the Mechanism of Cutterhead Jamming in Open-Type TBM Traversing Fault Fracture Zones  
Based on the case of TBM passing through a fault fracture zone in the position of gully 1, this paper analyzes the mechanism of cutter head jamming in an open TBM passing through a fault fracture zone and provides a basis for determining the jamming in subsequent gullies 2-4. Based on the research by [PERSON] et al. [22] on cutter head jamming, this paper further analyzes the mechanism of cutter jamming. The normal operation of the TBM cutter head requires overcoming the cutting resistance torque of the tool, the contact friction torque in front of the cutter head, and the friction torque at the circumferential edge of the cutter head. To ensure the normal excavation of TBM, the total torque mentioned above cannot exceed the maximum torque that the cutter head can release, otherwise, there will be a risk of machine jamming. Based on this theory, the mechanism of machine jamming is analyzed, and the analysis process is shown in Figure 2. This paper conducts theoretical research on the frictional resistance generated by the friction between the cutting tool and the surrounding rock on the cutting tool shaft and finally obtains the maximum torque T1 for TBM cutter head disengagement in Figure 2. The following identification process can provide a basis for TBM jamming determination. The maximum frictional torque generated by the cutter to overcome its frictional resistance intersects with the normal direction of the tunnel face, so the effect of the cutter overcoming frictional force needs to be analyzed separately. The maximum static frictional torque before the roller cutter rolls is calculated using Equation (1). \[T_{I}=n\mu_{1}rf_{R} \tag{1}\] \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Name** & **Gully Alignment** & **Lithology** & **Compressive Strength of Rock (MPa)** & **Gully Area (m2)** & **Crossing Length with Tunnel (m)** \\ \hline Gully 2 & 116 + 158–119 + 495 & Granitic Gneiss & 5–65 & 27.3 & 54 \\ Gully 3 & 119 + 495–119 + 769 & Granitic Gneiss & 5–60 & 15.8 & 140 \\ Gully 4 & 119 + 769–120 + 427 & Granite & 5–51 & 21.3 & 130 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Cave Top Washout Statistics. Figure 1: Schematic diagram of the erosion gully and geological profile of the tunnel site. (**a**) Schematic diagram of surface gully. (**b**) Geological map of the gully tunnel site area. In the equation:  
T\({}_{\text{I}}\): Overcoming the static frictional torque of the roller shaft before the cutter engages in cutting the surrounding rock. Number of cutters, with double cutters set to 2. Maximum static friction coefficient before the roller cutter starts rolling. Rolling radius of the cutter, in meters. Tangential force of the roller cutter, in kilonewtons (kN). The rotational resistance torque generated by the TBM cutter head during tunneling due to friction with the surrounding rock primarily consists of the frictional torque T\({}_{\text{a}}\) produced by the cutter cutting into the surrounding rock on the cutter head shaft, the resistive torque T\({}_{\text{b}}\) from friction between the cutter head sidewall and surrounding rock, and the frictional torque T\({}_{\text{c}}\) from contact between the front of the cutter head and the tunnel face. The calculation expression for the maximum frictional torque T\({}_{\text{a}}\) generated on the cutter head shaft before the cutter engages in cutting the surrounding rock is:  
\[T_{a}=\sum_{i=1}^{n}\mu_{1}r_{2}f_{R} \tag{2}\]  
In the equation:  
T\({}_{\text{a}}\): The maximum static frictional torque generated on the cutter head shaft before the roller cutter engages in cutting the surrounding rock.