## 1 Introduction  
The increase in the urban population, the escalating demand for high-rise buildings, and railway construction projects used to resolve transportation problems have led to an increase in the various types of construction works adjacent to the existing tracks of serviced railway lines. In particular, the tunnel excavation work conducted under the serviced railway lines in the downtown area is a key process directly related to the safety of all the phases of the railway construction project management. Therefore, in the case of adjacent excavation under the in-service railway structure, it is imperative to secure the stability and normal operation of the railway infrastructure. In addition, because the relative displacement of the railway infrastructure may occur due to adjacent underground excavations, the analysis of track irregularities is necessary. A previous study by [PERSON] et al. [1] investigated an evaluation method of the track deformation in the ballasted tracks on serviced railway lines with respect to adjacent excavation and assessed the impact of the irregularities in the track of the serviced railway line with respect to the excavation adjacent to the railway infrastructure. [PERSON] [2] performed a qualitative analysis on the dynamic behavior of the ballasted tracks and presented a dynamic model for the analysis of the Wheel-Rail-interaction-force analysis. The analysis demonstrated that the Wheel-Rail interaction force can be significantly changed due to track irregularities, and the results of experiments and a numerical analysis showed that the train speed was the main parameter. [PERSON] analyzed the effects of track irregularities on the dynamic wheel load of concrete tracks by applying the track irregularities measured in the section with track support stiffness changes in which a considerable vertical profile displacement occurred in the concrete tracks [3]. [PERSON] et al. conducted a study to analyze ground subsidence according to the tunnel passage in a geologically vulnerable zone [4]. The analysis investigated the ground subsidence and deformation in the existing urban railway infrastructure due to the weakened ground conditions from the adjacent tunnel excavation. The results showed that deformation in the vertical direction was dominant in the case of the railway infrastructure in the geologically vulnerable section. [PERSON], [PERSON] et al., and [PERSON] investigated the improvement method of an automated measurement and evaluation system, deformation of serviced railway line track, deformation of tunnel structure, and deformation of subway structure according to the adjacent excavation [5; 6; 7]. [PERSON] analyzed the definition of track irregularities and the effects of track irregularities on rolling stock-track interactions [8]. [PERSON] et al. proposed a disturbance rejection through a controller-optimization method for disturbances induced by track irregularities that are caused by track deformation and installation errors on a maglev line [9]. [PERSON] et al. quantified the irregularities of the railroad track using an automatic recording vehicle and confirmed that the values measured by the automatic recording vehicle and the values measured by the manual-measuring method agreed closely [10]. [PERSON] et al. compared the short- and long-term behaviors based on laboratory experiments and numerical analysis in order to verify the performance of ballasted and concrete tracks subjected to periodic loads [11]. As a result, the numerical-analysis and the experimental outcomes were consistent. [PERSON] et al. developed a Kalman-filtering-based methodology to monitor the lateral track irregularities [12]. The Kalman-filter-based strategy showed high accuracy and robustness when a systematic parametric analysis was performed based on a highly simplified linear bogie model and was able to capture the most relevant dynamic behavior. This study aims to evaluate the impact of track irregularities on ballasted tracks on serviced railway lines due to adjacent excavations.