# Displacement Monitoring of Subway Tracks and Tunnels According to Adjacent Construction
## 1 Introduction  
In the Republic of Korea, the demand for social infrastructure, such as high-rise buildings, public transportation, and convenience facilities, is increasing owing to population growth in metropolitan areas [1; 2; 3; 4]. In addition, owing to overcrowding in urban areas, large-scale, deep excavation construction is being conducted adjacent to structures [1; 2; 3; 4]. To ensure the safety of subway tunnels and track structures, an automated measurement system was introduced for real-time safety management. However, current monitoring results of the automated measurement system compare the maximum value with safety management standards within a specific period [1; 2; 3; 4]. This method evaluates the safety of subway tunnels and track structures based on whether they exceed safety management standards. In addition, the utilization of measurement results is extremely low, and research on reasonable and reliable standards and evaluation techniques is insufficient. In Korea, subway structure deformation occurs owing to ground deterioration, an increase in groundwater level, and adjacent excavation work. Accordingly, [PERSON] et al. [1] evaluated structural damage caused by the uplift and subsidence of subway box structures owing to changes in ground conditions. They presented a technique for determining damage through stress analysis of subway box structures using survey data. [PERSON] et al. [2] numerically analyzed ground settlement behavior when passing through a tunnel in a geologically vulnerable section. [PERSON] et al. [3] numerically analyzed the behavioral characteristics of concrete tracks laid on a subway box structure during subsidence and uplift. In addition, they analyzed the level of damage to the concreteballast resulting from concrete track settlement and uplift. [PERSON] et al. [4] analyzed track deformation caused by excavation work close to urban and high-speed railways. They modeled the construction stage, ground conditions, and gravel track and performed a precise three-dimensional (3D) numerical analysis. [PERSON] and [PERSON] [5] investigated the lining behavior following the excavation of the upper part of an operating underground structure using laser scanning. [PERSON] et al. [6] presented a technique for evaluating tunnel cracks using a tunnel scanner. [PERSON] et al. [7] experimentally analyzed the feasibility of measurement methods (TDP&S, TDPS) used for microseismic monitoring. [PERSON] et al. [8] measured damage to precast concrete tunnels in real time using a multichannel acoustic emission system. [PERSON] et al. [9] predicted the impact of tunneling on Roman architecture through numerical analysis using the Mohr-Coulomb model. [PERSON] et al. [10] monitored subway tunnel displacement based on a robotic total station (RTS) using a prism as a reflector. The monitoring range of the RTS was derived through tunnel experiments, and the accuracy of the long-term monitoring was verified. [PERSON] et al. [11] accurately and automatically calculated the leakage area of a shielded tunnel lining using a deep-learning model. [PERSON] et al. [12] analyzed the effects of foundation and excavation technology through numerical analyses using field measurement. [PERSON] et al. [13] presented an automatic recognition system for tunnel lining elements using deep-learning-based ground-penetrating radar images. The lining thicknesses measured using the corresponding technique and field test were found to be 95.45% consistent. [PERSON] et al. [14] presented a plan for improving safety evaluation techniques for subway tunnel structures using an existing automated measurement system. They presented a Gaussian probability density function analysis technique for quantitatively evaluating a substantial amount of measurement data. [PERSON] et al. [15] analyzed the dynamic wheel load using track deviation measurement results from adjacent excavation work. This study presents a technique for monitoring the behavior of subway tunnels and track structures following actual adjacent excavation work.