# Excavation and Construction Technology of Diversion Tunnel under Complex Geological Conditions
## 6 Design of Excavation Construction Methods
### Exavation Grouting Technology  
The grouting of the excavation section of the main tunnel during the construction of the diversion tunnel is set at the T65 fault fracture zone. In order to prevent geological disasters such as collapse during the excavation process of the main tunnel, the grouting starting section is set at \(0+306\), with \(0+306\) as the center, and the grouting area is determined by  
\[\Omega=\chi\cdot\frac{\beta+\alpha}{\xi}\times K_{a} \tag{7}\]  
In Formula (7), \(\chi\) represents the permeability coefficient during the grouting process; \(\beta\) represents the excavation angle of the main tunnel; \(\xi\) represents the soil parameters of the main tunnel; \(K_{a}\) represents the compressive value of the side wall of the main tunnel; \(\alpha\) represents the numerical value of the grouting angle [19]. In order to ensure construction safety on the workbench, a 1.0 m thick flocculant main mudguard is poured first, and then segmented grouting is carried out at intervals of 15 m, with 10 m of excavation every 10 m. In order to ensure the quality of the main tunnel excavation grouting, a push type segmented grouting process was adopted, as shown in Figure 6.  
According to the segmented drilling and grouting construction mode, the grouting equation for the excavation of the main tunnel of the diversion tunnel is:  
\[f=\lambda\frac{|\Omega\cdot L|}{\phi+\sigma}-Z \tag{8}\]  
In Formula (8), \(\lambda\) represents the grouting parameters for the excavation of the main tunnel; \(\Omega\) represents the area of the grouting operation during the excavation process of the main tunnel; \(L_{s}\) represents the excavation parameters of the main tunnel during the  
Figure 6: Segmental drilling and grouting construction mode. construction of the diversion tunnel; \(\phi\) represents the height of the main tunnel; \(\sigma\) represents the depth of the main tunnel; \(Z_{j}\) represents the amount of grouting [20]. According to the grouting equation for the excavation of the main tunnel of the water conservancy diversion tunnel, the grouting technology for the excavation of the main tunnel of the water conservancy diversion tunnel has been designed. The specific steps are as follows:  
Step 1: Set up the structure and antislurry board of the antislurry wall. T65 fracture is a type of strata with high pressure. To prevent groundwater from entering the working face or erosion during the grouting process in the nongrouting area, C20 cement mortar is poured once before each pregrouting, with a thickness of 100 m. After each grouting is completed, leave a 5 m space for the next grouting step. Step 2: Calculate the grouting pressure and diffusion radius. In the fracture zone, the grouting pressure is mainly split grouting, and the grouting pressure should not be too high to avoid causing too much disturbance to the formation and exceeding the bearing capacity of the grout stop wall and grout stop plate. Therefore, it is recommended to have a grouting pressure of 2-6 MPa at the fracture zone and control the grouting radius at 2 m. Step 3: Install grouting holes for the main tunnel of the diversion tunnel. In the headrace tunnel, there are 86 preinjected mud holes in each cycle, with a depth of 10 m for boreholes 1-23, 12 m for boreholes 24-43, and 16.5 m for boreholes 44-86. As shown in Figure 7, 89 are installed at the front end of the grouting hole \(\times\) 4 mm orifice tube with a length of 3.5 m.  
The grouting problem in the excavation of the main tunnel of the diversion tunnel construction is analyzed. If the grouting pressure and expansion radius cannot meet the requirements of the main tunnel construction, mud should be injected first, and the grouting operation can only be completed when the mud is injected to twice or more of the level of the original grouting.