## 2 Project Profile
### Engineering Measured Data  
Figure 5a shows the cumulative maximum horizontal displacement of the tunnel observed throughout the monitoring period. The maximum horizontal displacement of the tunnel is greater on the south side (3.7 mm) compared to the north side (3.4 mm), with both values nearing the warning threshold. At the same time, regarding its spatial distribution, the maximum horizontal tunnel displacement within the open excavation section of the foundation pit is also greater on the east and west sides compared to the covered excavation section. Initially, there is minimal horizontal displacement of the tunnel during the early stage of foundation pit excavation. Subsequently, with increasing depth, the tunnel gradually  
Figure 4: Layout of tunnel displacement monitoring points.  
\begin{table}
\begin{tabular}{c c c} \hline
**Monitoring Projects** & **Warning Value** & **Control Value** \\ \hline horizontal displacement & Accumulated deformation up to 4 mm or & 5 mm \\  & deformation rate over 1.0 mm/day & \\ vertical displacement & Accumulated deformation up to 4 mm or & \\  & deformation rate over 1.0 mm/day & 5 mm \\ differential settlement of structural joints & Accumulated deformation up to 3 mm or & \\  & deformation rate over 1.0 mm/day & 4 mm \\ fissures & 2 mm & / \\ \hline \end{tabular}
\end{table}
Table 1: Early warning and control values for deformation monitoring in existing tunnels.  
shifts towards the pit. Throughout the construction stage of the station's main structure, the tunnel's horizontal displacement exhibits fluctuations but demonstrates an overall decreasing trend. Figure 4(b) illustrates the cumulative maximum vertical displacement of the tunnel at each measuring point during the monitoring period. Figure 4(b) shows that both the north and south sides of the tunnel undergo subsidence and uplift during foundation pit construction. The maximum uplift and settlement values on the south side of the tunnel (\(1.8\) mm and \(-3.3\) mm, respectively) are slightly less than those on the north side (\(2.1\) mm and \(-3.5\) mm, respectively) and are approaching the warning thresholds. Spatially, the tunnel's maximum vertical displacement within the open excavation section of the foundation pit on both sides exceeds that of the covered excavation section. Initially, the tunnel experiences slight uplift during the early stage of foundation pit excavation, followed by gradual subsidence with increasing excavation depth in the later stages. Throughout the construction stage of the station's main structure, the tunnel's vertical displacement fluctuates but exhibits an overall decreasing trend.  
Figure 6 illustrates the cumulative maximum value of differential settlement for each structural joint of the tunnel observed throughout the monitoring period. During the construction of the foundation pit, the maximum differential settlement of the tunnel's structural joints reaches \(2.0\) mm on the south side and \(2.3\) mm on the north side, nearing the early warning threshold. Spatially, the differential settlement of the tunnel's structural joints is notably higher on the south side than on the north side in the eastern portion of the open-cut section of the foundation pit, while the opposite trend is observed elsewhere. The differential settlement and range of variation of the tunnel's structural joints during the excavation stage of the foundation pit are less pronounced than during the construction stage of the station's main structure.  
Figure 5: Cumulative maximum tunnel displacement at each monitoring point.