# 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  
Step 1: TSP data collection and parameter settings. TSP technology is a technique for predicting tunnel geological conditions using seismic methods. TSP technology is based on the principles of seismic wave propagation and reflection. By deploying seismic detectors on the ground or underground, they monitor and analyze the propagation and reflection of seismic waves in underground rocks in order to obtain geological information about underground rock formations in front of tunnels or potential work areas. The prediction mileage range selected by TSP technology in the excavation project of the diversion tunnel is \(44+700\)-\(16+632.357\). On the basis of determining the relationship between the location and direction of the unfavorable geological body and the tunnel axis, the seismic source point is selected to arrange the measurement wall. This measurement wall is selected at the left wall position of the tunnel entrance. In addition, based on the actual geological conditions on site, the mileage of the receiver is determined, and the offset distance between the blast holes and the detector is reasonably set. A total of 24 blast holes are set on the same horizontal plane as the sensor, with a spacing of 1.5 m between each blast hole. The detector is placed in the casing according to the standard, directional calibration work is performed, and an anchoring agent is used to tightly connect the casing with the surrounding rock, ensuring that there is no gap between the casing and the surrounding rock, which is conducive to signal reception. After connecting the entire instrument according to the operation process, the collection phase begins in preparation to collect data [8]. Finally, the finished explosive package is placed at a depth of 1.5 m in the blast hole, the blast hole is filled with water until it is saturated, then the muzzle is sealed for detonation. The propagation form of vibration waves excited by explosions is spherical waves, which propagate in the opposite direction to the sensor. When encountering unfavorable geological bodies such as karst and faults, some seismic wave signals will generate reflected waves and be received by sensors, while the remaining part will continue to propagate until it is completely consumed [9; 10]. After completing the data reception of 24 shots, the on-site data collection work is completed. The principle of TSP observation is shown in Figure 2.  
Figure 1: Construction system layout. Using SeisSpace/ProMAX3D software to process the collected data, the specific processing steps include: data adjustment, bandpass filtering, head wave pickup, pickup processing, gun energy balance, loss coefficient estimation, reflection wave extraction, transverse and longitudinal wave separation, velocity analysis, depth migration, and reflection surface extraction. The processing parameters are set to default. In order to ensure the processing accuracy of TSP data, it is necessary to select the appropriate maximum gain and loss coefficient in the reflection wave extraction, otherwise information will be lost. By setting appropriate parameters, this problem can be effectively improved, restoring some high-frequency information and improving the quality of ground detection. To improve the service effectiveness of TSP prediction results in practice, it is necessary to use indicators such as wave velocity, density, Poisson's ratio, and mechanical modulus to depict the rock mass quality in front of the diversion tunnel face through TSP [11]. The higher the Poisson's ratio, the higher the water content of the rock mass, while the smaller the values of other indicators, the poorer the quality of the rock mass [12]. Step 2: Calculate TSP data.