# Excavation and Construction Technology of Diversion Tunnel under Complex Geological Conditions
## 2 Project Overview and Construction Difficulties Analysis
### Implementing Advanced Geological Prediction Based on TSP Technology
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Receiving Hole** & **Blast Hole** \\ \hline Quantity & One on each side wall & 24 \\ Diameter & \(\Phi\)42–45 mm & \(\Phi\)32–38 mm \\ Depth & 2 m & 1.5 m \\ Direction & Vertical tunnel axis. Tilt up 5–10\({}^{\circ}\) & Vertical tunnel axis. Tilt down 10–20\({}^{\circ}\) \\ Height & 1.0–1.5 m from the bottom of the tunnel & 1.0–1.5 m from the bottom of the tunnel \\ Position & Above 60 m from the palm surface & The first shot point is 55 m away from the same side \\  & detector, and the spacing between the shot holes is 1.5 m \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Parameters of blast holes and receiving holes. Figure 2: TSP observation principle. Using the TSP data collected and processed to obtain the wave line time, and combining it with the distance between it and the blasting position, the longitudinal wave velocity \(V_{p}\) of the rock mass is obtained as follows:  
\[V_{p}=\frac{X_{s}-R_{cv}}{T} \tag{1}\]  
In Formula (1), \(X_{s}-R_{cv}\) represents the distance between the detector and the blasting hole. Based on this, the shear wave velocity \(V_{s}\) and other physical coefficients of the rock mass can be obtained, and the water content of the rock mass can be obtained based on practical foundations. Combining velocity analysis, the propagation world of reflected signals is transformed into distance, and the dynamic elastic modulus and dynamic Poisson's ratio are respectively expressed as:  
\[E_{d}=\rho V_{s}^{2}\left(3V_{p}^{2}-4V_{s}X_{s}^{2}\right)/\left(V_{p}^{2}-V_{ s}\right)^{2} \tag{2}\]  
\[v_{d}=\frac{V_{p}^{2}-2V_{s}^{2}}{2\left(V_{p}^{2}-V_{s}^{2}\right)} \tag{3}\]  
In the formula, \(\rho\) represents the density of the rock mass. If the dynamic elastic modulus of a rock mass is higher than the static elastic modulus, the \(\frac{E_{d}}{E_{s}}\) value of hard rock is lower, while the \(\frac{E_{d}}{E_{s}}\) value of weak rock is higher [13], then:  
\[E_{s}=\frac{E_{d}}{A_{1}\exp\left(A_{2}\times V_{p}/V_{s}\right)} \tag{4}\]  
In the formula, \(A_{1}\) and \(A_{2}\) both represent the rock mass coefficient. By using TSP technology to obtain parameters such as rock wave velocity, \(V_{p}/V_{s}\), and density, comprehensive prediction of surrounding rock information in front of the diversion tunnel can be achieved. Step 3: Determine the classification of rock surrounding tunnel. Based on the \"Code for Engineering Geological Survey\" and the underground seepage situation, stress magnitude, and surrounding environment of the surrounding rock, combined with the value of \(V_{p}\), the classification standards for the surrounding rock of the diversion tunnel are comprehensively analyzed, and the results are shown in Table 2.  
Step 4: Interpretation of forecast results. After processing the collected TSP data, in order to predict the geological conditions of the rock surrounding the tunnel, it is necessary to combine tunnel design data, geological exploration data, and the actual geological conditions of the excavated section to interpret the predicted data. In general, the interpretation of data should follow the following principles:  
1. Interpretation is based on reflection amplitude, which is positively correlated with the difference between reflection coefficient and wave impedance. If the reflection \begin{table}
\begin{tabular}{c c} \hline \hline
**Surrounding Rock Level** & **Longitudinal Wave Velocity of Rock Mass (km/s)** \\ \hline I & \(>\)4.5 \\ II & 3.5–4.5 \\ III & 2.5–4.0 \\ IV & 1.5–3.0 \\ V & 1.0–2.0 \\ VI & \(<\)1.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Basic classification table for railway tunnels. amplitude is larger, the difference between the two is greater, and vice versa; the reflection amplitude can also reflect the rock mass, with positive and negative reflection amplitudes corresponding to rigid and weak rock masses, respectively. 2. When interpreting based on \(V_{p}\), when the rock mass is harder and more complete, \(V_{p}\) is relatively higher, and vice versa. 3.