# 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
This indicates that, despite being just one step away from the nose, the pipe sheet structure has not fully mitigated the vibration, and the vibration energy is still transmitted relatively strongly to the first ring of pipe sheets. As the shield progresses further to the fourth lined segment (at 4.5 m), the axial vibration displacement remains as high as 0.1 mm, demonstrating the strong persistence and propagation capacity of the vibration along the tunnel axis. Even at distances beyond 9 m, the axial vibration displacement decreases to less than 0.05 mm, suggesting that the  
Figure 6: Vibration displacement in the direction of gravity. vibration energy maintains a certain level of intensity over longer distances. In contrast, the vibration displacement in the gravity direction has significantly decreased at the same locations, further confirming the distinctiveness and persistence of axial tunnel vibrations. As shown in Figure 6, the shield machine cutter plate exhibits the most significant vibration in the gravity direction (i.e., the vertical direction), with a peak vibration displacement reaching as high as 0.4 mm. This phenomenon highlights the strong vibrations generated by the shield machine during the propulsion process, especially during startup and steering, when the impact force of the cutter cutting through the soil and the propulsion system result in substantial vibration energy. This intense vibration not only affects the shield machine itself but also propagates through the mechanical structure to the neighboring segments. Specifically, the segment located at 0 m (the first ring of segments immediately adjacent to the shield nose) experiences a vibration displacement of 0.13 mm in the gravity direction. While weaker than at the cutter plate, this value remains significant, indicating that vibration energy is still strongly transmitted to the segment even when only one step away from the cutter plate. This may be due to the close connection between the segment and the shield, allowing the rapid transfer of vibration energy, while the segment structure has not yet fully utilized its damping effect. As the shield advances to the fourth ring of pipe sheets (at 4.5 m), the vibration displacement in the gravity direction decreases significantly, with a peak value no greater than 0.05 mm. This indicates that the vibration energy is progressively absorbed and attenuated as it propagates over distance. The damping effect of the segment structure begins to manifest, particularly in the axial and radial directions. Factors such as the connection method between the segments, their material properties, and thickness all contribute to the effective reduction in vibration transmission. Additionally, the soil medium absorbs part of the vibration energy, further diminishing the impact of the vibration. By the time the pipe sheet reaches 9 m, the vibration displacement in the gravity direction decreases further to 0.02 mm, which is nearly negligible. This indicates that the vibration impact has essentially disappeared within about 9 m behind the shield cutter, and the shield construction's impact on the surrounding environment has been effectively controlled. Notably, vibration signals collected at a distance of 15 m are extremely sparse, indicating that the vibration energy has almost completely dissipated at this distance and no longer significantly affects the surrounding environment. Comparing Figures 4-6 reveals that the vibration displacement on the construction-side tunnel lining segment is greatest in the tunnel's axial direction, followed by the radial direction, and is smallest in the vertical direction. This pattern indicates that the primary vibration response of the construction-side tunnel arises from the shield machine's thrust force transmitted through the excavation face to the tunnel lining segments. Consequently, the data along the axial direction are more pronounced. This phenomenon can be attributed to the mechanical characteristics of shield tunneling construction.