## 2 Test Design and Result Analysis
### Test Scheme  
This study mainly focuses on the deformation monitoring of adjacent stations and track structures. The main contents of monitoring include the following:  
(a) Displacement monitoring of the foundation pit retaining pile;  
(b) Displacement monitoring of the existing station main body and subsidiary structure;  
(c) Displacement monitoring of the existing track structure;  
(d) Track geometry monitoring.  
The monitoring contents and instruments of the project are shown in Table 2.  
The abovementioned monitoring contents correspond to different monitoring point arrangements. The top horizontal displacement, vertical displacement monitoring and deep horizontal displacement monitoring of foundation pit retaining piles are arranged with 22 measuring points, for a total of 66 measuring points, numbered ZQS-1-ZQS-22, ZQC1-ZQC-22 and ZQT-1-ZQT-22, respectively. The number sequence is ordered from the northeast corner of the foundation pit along the foundation pit counterclockwise. Ordering is performed from north to south. The monitoring layout of the foundation pit is shown in Figure 3.  
A total of 14 measuring points for station automatic monitoring (ZDH-1-ZDH-14) are arranged near the sidewall of the station near the foundation pit. There are 10 artificial monitoring points for station lateral deformation (CZH-1-CZH-10), 8 artificial monitoring points on the left side (ZZC-1-ZZC-8) and 14 artificial monitoring points on the right side (YZC-1-YZC-14). The right track structure has 16 vertical monitoring points (YGD-1-YGD-16) and 16 horizontal displacement monitoring points (YGS-1-YGS-16), and the left track structure has 10 vertical monitoring points (ZGD-1-ZGD-10) and 10 horizontal displacement monitoring points (ZGS-1-ZGS-10). There are nine vertical monitoring points (C-1-C-9) and six horizontal monitoring points (CH-1-CH-6) at the entrance and exit. The order of the monitoring points of the main body of the station and the track is from north to south, and the order of the vertical displacement monitoring points at the entrance and exit starts from one side of the station and rotates counterclockwise along the entrance and exit structure. The layout of the deformation monitoring points of the station and track structure is shown in Figure 4.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Serial** & **Category** & **Monitoring** & **Monitoring** & **Deformation** & **Monitoring** & **Monitoring** \\
**Number** & **Category** & **Content** & **Project** & **Deformation** & **Equipment** & **Accuracy** \\ \hline
1 & Automatic & Station structure & & Vertical & Static level & 0.1 mm \\
2 & & Station structure & Station structure & Vertical & Electronic level & 0.3 mm \\
3 & & & Lateral & Total station & 0.5 mm \\
4 & & Orbital structure & Vertical & Electronic level & 0.3 mm \\
5 & Manual & Track structure & Ancillary structure & Lateral & Total station & 0.5 mm \\
6 & & Orbit & Geometric bits & Vertical & Electronic level & 0.3 mm \\
7 & & Foundation pit & & & Track gauge & 1.0 mm \\
8 & & retaining structure & Enclosure pile & Deformation & Clinometer & 0.02 mm/0.5 m \\ \hline \hline \end{tabular}
\end{table}
Table 2: The main content of foundation pit engineering monitoring.  
When the new foundation pit is adjacent to the existing subway station, the allowable limit value of the track line deformation of the existing operating station should meet the daily maintenance requirements of the track determined in the Beijing subway engineering maintenance rule, as shown in Table 3.