# Investigation on Vibration Influence Law of Double-Shield TBM Tunnel Construction
## 3 Monitoring Program  
### Plan of Vibration Monitoring  
The vibration monitoring uses low-frequency vibration sensors (JX941) and a dynamic signal acquisition instrument (HC-1000) provided by Anhui Hengxin Hongce Electronic Technology Co., Ltd., (Hefei, China). By using passive closed-loop servo technology, the vibration sensors have good low-frequency characteristics. At the same time, there is an IPX8 waterproof steel cylinder outside the sensor, which can be used for vibration monitoring in deep holes. The technical parameters of the vibration sensor are shown in Table 1. This monitoring uses vibration sensors to pick up the acceleration of vibration signals. First, the vibration signal is converted into an electrical signal in the sensors. Then, the electrical signal is transmitted to a signal acquisition instrument through the cable. After the signal is interpreted by the signal acquisition instrument, the monitoring data are transmitted to the computer for viewing and storage. The principle of vibration monitoring is shown in Figure 4.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \begin{tabular}{c} **Physical** \\ **Quantities** \\ \end{tabular} & \begin{tabular}{c} **Sensitivity** \\ **(V/m/s\({}^{2}\))** \\ \end{tabular} & \begin{tabular}{c} **Measurement** \\ **Range (m/s\({}^{2}\))** \\ \end{tabular} & \begin{tabular}{c} **Pass Band (Hz)** \\ **Resistance (kf)** \\ \end{tabular} & \
\begin{tabular}{c} **Output Load** \\ **Ratio (m/s\({}^{2}\))** \\ \end{tabular} &
\begin{tabular}{c} **Resolution** \\ **Size (mm)** \\ \end{tabular} \\ \hline acceleration & 0.3 & 0–20 & 0.2–80 & 1000 & \(5\times 10^{-6}\) & \(56\times 56\times 77\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Technical parameters of the vibration sensor (JX941).  
Figure 4: The principle of vibration monitoring.  
Figure 3: Cutter-head of double-shield TBM (Reprinted with permission from Refs. [30; 31].)The mileage number of DK19 + 678.5 is selected as the vibration monitoring section, which is perpendicular to the axes of two tunnels. A total of nine sampling holes are arranged in the monitoring section. Meanwhile, the sampling holes are named Z-1-Z-9 from right to left. Among them, Z-4 and Z-8 are located above the vaults of the right and left tunnels, respectively. The spacing of each sampling hole is 0.5-1 times the tunnel diameter. Except for Z-4 and Z-8, which have a depth of 17 m, the depths of other sampling holes are 21 m.  
There are three monitoring points arranged in each sampling hole. The three monitoring points are located at a depth of 0, 10 m, and at the bottom of the sampling holes. The measuring point layout of the vibration monitoring is shown in Figure 5. The sensors of three monitoring points are named 01, 02, and 03 from top to bottom. Moreover, the sensor of each measuring point can monitor three directions of X, Y, and Z. The X and Y-directions are parallel to the tunnel axis and tunnel radial direction, respectively, and the Z-direction is perpendicular to the horizontal direction. Therefore, there are a total of 27 sensors in the vibration monitoring section.