# Excavation and Construction Technology of Diversion Tunnel under Complex Geological Conditions
## 6 Design of Excavation Construction Methods
### Exavation of the Vertical Shaft Section of the Diversion Tunnel  
The excavation area of the vertical shaft section is from the elevation of the upper flat section bottom plate to the elevation of the lower flat section top plate, including the curved section of the section. Due to the lack of conditions for the arrangement of reverse drilling rigs and considering factors such as construction progress, economy, and reliability, it was ultimately decided to use the manual reverse drilling method for construction. The manual reverse drilling well excavation was carried out from bottom to top, then expanded into a slag chute, and finally excavated from top to bottom to the design section. Among them, the diameter of the excavation section for the guide shaft is 2 m, the diameter of the excavation section for the slag chute is 4 m, the angle between the central axis and the horizontal is 98.5\({}^{\circ}\), and the length is 65.8 m. Before the construction of the guide shaft, the technical overbreak construction of the lower bend section must be completed, and before the first expansion excavation, the technical overbreak construction of the upper bend section must be completed.  
1. Artificial antimissile. To ensure construction safety, before excavation, the excavation support trolley must be used to lock and support the surrounding area of the guide shaft opening. At the same time, the exposed face and surrounding walls should be sealed with plain shotcrete to prevent the collapse of surrounding rock around the opening. Support measures and parameters: 0.2 m away from the contour line, with a circumferential spacing of 0.55 m, \(\Phi\)25. L = 3 m anchor rod, with a shotcrete sealing thickness of 5 cm. When drilling and blasting at the entrance of the pilot shaft, secondary blasting operation is adopted. The first blasting will be carried out by cutting the small pilot hole at the entrance of the tunnel, with the blasting footage controlled at 1-2 m. The second blasting will be carried out by surrounding hole smooth blasting, and the bedrock surface after the entrance blasting should be promptly sprayed and supported to ensure the safety and stability of the tunnel entrance. After the formation of the tunnel gate, manual excavation of a 2 m diameter pilot shaft will be carried out from bottom to top. The pilot shaft blasting will becarried out using a \"half second detonator, smooth blasting\" method, with a distance of 40 cm between the smooth blasting holes and a footage of 2 m per cycle. 2. Expansion excavation of slag chute. To ensure the smooth excavation of the vertical shaft section and the smooth mucking, after the construction of the guide shaft is completed, the first expansion excavation is carried out using a hanging basket and lifting equipment to drill radially from bottom to top. The expansion excavation is carried out in a mucking shaft with a diameter of 4 m. 3. Secondary expansion excavation. After the expansion of the slag chute is formed, the second expansion of the vertical shaft section is carried out to the design structural line. After each row of shots, safety measures must be taken seriously, and then the measuring personnel should retest the section to clarify the underexcavation situation and promptly handle it. The final depth of each layer of blasting holes is controlled by a slightly inclined slope towards the direction of the slag chute to facilitate manual slag removal. In the second excavation process, to ensure the quality of the upper and lower bend forming, the drilling direction is the tangent direction of the arc section, the drilling depth does not exceed 2.5 m, and the technical overbreak is controlled within 16 cm. To ensure the flatness of the excavation of the upper and lower bends and vertical sections, as well as to control overex excavation and underexcavation, smooth blasting is used around the perimeter, and the single-cycle footage is controlled at around 2.5 m. The stone slag is manually scraped into the slag chute and slid into the lower slag discharge area.