## 4 Summary of the Project and Preprocessing of Data  
### Summary of the Project  
The KS tunnel spans a total length of 283 km and is constructed using eleven open-type [22] TBM machines. It reaches an average depth of 428 m, with a maximum depth of 774 m. This project is characterized by its immense scale, spanning multiple regions and involving complex construction techniques. The focus of this article lies on the research conducted on the section between KS 253 + 877 and KS 254 + 588 within the KS tunnel. From a rock classification perspective, this particular section comprises consecutive segments featuring different types of surrounding rocks, including II, IIIa, IV, and V. The geological profile of this section is shown in Figure 5.  
Section KS 253 + 877-KS 254 + 045: The exposed lithology of this section comprises tuff, which is partially schistified, exhibiting a gray color and thick layered structure. The rock layers in this section are oriented at 280\({}^{\circ}\)NE \(\angle\) 75-80\({}^{\circ}\), indicating a medium-to-hard rock classification. The primary joint occurrence is observed at 290\({}^{\circ}\)NE \(\angle\) 75\({}^{\circ}\), with slight fissure development. Along the rock layer, there is a well-developed gray carbonaceous interlayer measuring 0.5-0.8 m in thickness and spaced at intervals of 3-10 m; their count amounts to five. These openings are sealed and exhibit smooth undulation. Within the interlayer, the surrounding rock experiences fragmentation and displays low strength along with minor wrinkling phenomena. The rock wall within this section remains dry while maintaining overall integrity of the surrounding rock mass, resulting in good chamber stability overall. Based on these observations, the overall categorization for the surrounding rocks within this section is determined as IIIa. Section KS 254 + 045-KS 254 + 411: The exposed lithology of this section comprises tuff, characterized by a blue-gray hue and a thick layered structure. The orientation of the rock layers is 280\({}^{\circ}\)NE \(\angle\) 75-80\({}^{\circ}\), indicating its classification as hard rock. The primary joint occurrence is observed at 310\({}^{\circ}\)SW \(\angle\) 5-15\({}^{\circ}\) and 290\({}^{\circ}\)NE \(\angle\) 75\({}^{\circ}\), with a total count of 10 joints exhibiting closed openings and smooth undulations. No fissures are present in this section. The rock walls within this segment exhibit dryness, showcasing excellent overall integrity of the surrounding rock mass and stable cavern conditions. KS 254 + 411-KS 254 + 542 section: the exposed lithology of this section is the schist-to-tuff, with gray-black to gray-green color and thick layered structure. The occurrence of the rock layer is 280\({}^{\circ}\)NE \(\angle\) 75-80\({}^{\circ}\), thus belonging to medium hard to soft rock. The surrounding rock of this section is affected by tectonic extrusion and hydrothermal alteration, with obvious crumple, strong carbonization, schistity development, phyllite fossilization, chlorite fossilization, and a small amount of serpentine fossilization phenomenon; the main joint occurrence is 280-300\({}^{\circ}\)SW \(\angle\) 30-45\({}^{\circ}\), 290\({}^{\circ}\)NE \(\angle\) 75\({}^{\circ}\), the fracture surface is undulating and smooth and slightly rough and filled with phyllite film; the spacing is 1-3 m, running through the chamber, affected by the combination of fracture cutting and layer; the block drops 30-60 cm along the fracture surface, the waist line collapse on the right side of pile No. 254 + 454; the axial length is 3 m, the circumferential width is 1.3 m, and the radial depth is 1.7-2.0 m. The overall integrity of the surrounding rock of this section is poor to broken, the chamber is basically stable, and the local instability is significantly increased. The overall surrounding rock of this section is determined to be class IV. Since the pile No. 254 + 423, the surrounding rock gradually becomes complete, the fracture is less developed, and the strength is significantly increased.