# Displacement Monitoring of Subway Tracks and Tunnels According to Adjacent Construction
## 4 Analysis and Discussion  
In this study, a tunnel convergence meter sensor was installed in a subway tunnel structure, and monitoring was performed for 18 months. Gaussian probability density function analysis was performed for quantitative evaluation using the measurement results from long-term monitoring. Figure 10 shows the maximum vertical displacement analysis results from Sections A-C. The Gaussian analysis results for each section according to the adjacent excavation work revealed that in Section A, the adjacent excavation work did not significantly affect the measurements of sensors TL-1, TL-3, TL-4, and TL-6. By contrast, for sensors TL-2 and TL-5, the displacement increased rapidly in the early stages of the excavation work. Therefore, the locations of sensors TL-2 and TL-5 in Section A were directly affected during the adjacent excavation work. Vertical displacement was observed in Section B; however, the impact of the excavation work was not significant. In Section C, the largest displacement occurred at the location of sensor TL-2. However, except for the location of sensor TL-2, most locations exhibited displacement behavior in the opposite direction. Therefore, the tunnel structure was observed and analyzed to have a more significant tunnel displacement at the start and end points than at the center of the excavation area. The tunnel maximum vertical displacement results using Gaussian analysis of 1-month and 18-month data are shown in Table 5.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Sensor**} & \multirow{2}{*}{\ \begin{tabular}{c} **Location** \\ **(m)** \\ \end{tabular}  } & \multicolumn{3}{c}{**Average (mm)**} & \multicolumn{3}{c}{**Standard Deviation (mm)**} & \multirow{2}{*}{ \begin{tabular}{c} **Field Maintenance** \\ **Criteria (mm)** \\ \end{tabular}  } \\ \cline{1-1}  & & **1 Month** & **10 Months** & **18 Months** & **1 Month** & **10 Months** & **18 Months** & **Criteria (mm)** \\ \hline RM-01 & 0 & \((-)0.064\) & 0.033 & \((-)0.115\) & 0.079 & 0.074 & 0.076 & \\ \hline RM-11 & 20 & \((-)0.086\) & \((-)0.126\) & \((-)0.167\) & 0.066 & 0.058 & 0.073 & \\ \hline RM-21 & 40 & \((-)0.049\) & 0.059 & \((-)0 Figure 10: Maximum vertical displacement analysis results (Xc + SD): (**a**) Section A; (**b**) Section B; (**c**) Section C.  
In this study, a continuous data analysis in the tunnel direction was performed using the analysis results of the tunnel convergence meter sensor, as shown in Figure 11. Using the data in Table 5, the range of tunnel vertical displacement influence was analyzed through displacement control for each location [22]. Figure 11: Cont. As a result of the analysis of the tunnel vertical deformation influence range, a large subsidence was found at the TL-3 location of Section C, as shown in Figure 11b. On the other hand, upward displacement was observed in TL-6 of Section C. In addition, it was found that similar displacement behavior occurred in Figure 11d, which is the 18 th month data. Existing evaluations use data at nodes, making continuous data analysis difficult. It is believed that the continuous displacement behavior of the tunnel can be identified by using the technique presented in this study. In this study, a track bed settlement sensor was installed on a subway track structure to quantitatively evaluate the monitoring data. Figure 12 shows the vertical displacement analysis results for sensors RM-01 to RM-68. Figure 11: Max vertical displacement analysis results (Xc + SD): (**a**) Boundary condition; (**b**) 3D view (1 month); (**c**) Top view (1 month); (**d**) 3D view (18 months); (**e**) Top view (18 months). The per location analysis according to the adjacent excavation work, shown in Figure 12, revealed a vertical displacement of approximately (\(-\))0.181 mm approximately 30 m before the adjacent excavation work area. However, the vertical displacement resulting from the adjacent excavation work was approximately (\(-\))0.424 mm, corresponding to a 0.243 mm reduction.