# The Vibration Response Characteristics of Neighboring Tunnels Induced by Shield Construction
## 3 Monitoring Data Validation Analysis
### Monitoring Results  
#### 3.3.1 Analysis of Vibration Monitoring Results on the Construction Tunnel Side  
At the shield construction site, 10 sensors were installed along the construction-side tunnel to monitor vibration responses. One sensor was positioned at the head of the shield machine to serve as the reference point for the vibration source. The remaining seven sensors were placed along the tunneling line at 1.5 m intervals, corresponding to the length of the pipe segments, covering the area from 0 m to 9 m. The 0 m position, located adjacent to the shield chassis, corresponds to the most recently assembled pipe segment ring. Additionally, because the vibration response becomes weaker beyond 10 m, the final two sensors were positioned at 12 m and 15 m to ensure data integrity and comparability. This sensor arrangement enables a more comprehensive reflection of the propagation characteristics of vibrations at different axial distances. The vibration  
As shown in Figure 4, the shield cutter exhibited the most significant vibration characteristics during the construction process. Specifically, the peak vibration displacement in the radial direction of the tunnel at the cutter head (i.e., pointing toward the tunnel center) reached 0.4 mm, significantly higher than the vibration levels observed at other locations. This indicates that the cutter head was the most intense vibration area throughout the construction process. This strong vibration primarily originated from the substantial thrust force generated by the shield machine during advancement and the impact force of cutting the soil, with particularly pronounced vibrations during startup and steering. In contrast, the segment at the 0 m position (i.e., the first section of the lined segment immediately adjacent to the cutter head) exhibited a smaller radial vibration displacement of 0.07 mm. This suggests that, although the vibration at the cutter head was intense, its effect diminished rapidly over a short distance. As the shield machine advanced, vibration energy was gradually transferred to subsequent segments; however, the vibration amplitude decreased sharply due to the increasing distance and the damping effect of the segment structure. By the fourth lined segment (located at 4.5 m), the radial vibration displacement of the tunnel had significantly reduced, with a peak value not exceeding 0.03 mm. This indicates that as distance increases, vibration energy is progressively absorbed and attenuated during propagation, with the damping effect of the segment structure playing a crucial role. At the 9 m position, the vibration displacement in the radial direction further diminished to 0.01 mm, which is almost negligible. This demonstrates that the vibration impact effectively  
Figure 5: Tunnel axial vibration displacement. dissipated within approximately 9 m behind the cutter head, confirming that the vibration impact of the shield construction on the surrounding environment was well controlled. As shown in Figure 5, the vibration displacement in the axial direction of the tunnel is significantly larger than that in the gravity direction. This phenomenon highlights the unique nature of vibration propagation during shield machine construction. Specifically, the shield cutter exhibits the most prominent vibration characteristics in the tunnel's axial direction, with a peak vibration displacement reaching 0.4 mm, much higher than the vibration levels at other locations. This suggests that the axial thrust force generated by the shield machine during its advancement, along with the impact force during soil cutting, not only creates a strong vibration source at the head but also facilitates strong vibration propagation along the tunnel axis. In contrast, the segment located at 0 m (the first section of lined segment immediately adjacent to the shield's nose) experiences a vibration displacement of 0.15 mm in the axial direction, which, although lower than at the nose, remains at a high level.