## 5 Conclusions  
This study investigated a load-based track-irregularity-analysis technique for ballasted tracks on a serviced railway line with respect to adjacent excavations. Based on comparative analyses between the numerical and field-measurement results, the correlation between track irregularities and Wheel-Rail interaction force was verified. Thus, we emphasized the necessity for a load-based track-irregularity-management plan. As a result of the numerical analysis of the track deformation, the locations wherein the maximum vertical and lateral deformations occurred differed with respect to the excavation area. Therefore, instead of a concentrated installation of the sensors in the center of the excavation area during the adjacent excavation, the ends of the excavation section should be included for installation. Additionally, it is advisable to examine the locations of sensor installation based on the considerations of the location of the serviced railway line track. As a result of the measurements of track irregularities using the track-geometry-measurement system (Track master) and railbed-settlement-monitoring sensor (RM sensor), the maximum vertical profile and alignment values were measured at the center of the excavation work site, and the lateral deformation characteristics, such as the cross level and gauge, were clearly observed at the end points of the track section. Given that the maximum value measured by the RM sensor was different from the actual level of rail deformation when the RM sensor measurements were close to the maintenance criteria values before, during, and after the excavation work, it would be appropriate to use the Track master for direct measurements of the rail deformation. As a result of comparisons of the representative value of the dynamic wheel load that was calculated based on measurements of a ballasted track that did not contain any irregularities and based on the analyzed results of the Wheel-Rail interaction force representing the track irregularities, the maximum dynamic wheel load was measured in the range of ~10 m around the location of the occurrence of the maximum track irregularity. The results indicated that in the track section which yielded irregularities within the maintenance criteria, the dynamic-wheel-load value was within the range of the representative value of the dynamic wheel road within the design speed. However, in the section which exceeded the maintenance criteria of track irregularities, the dynamic-wheel-load value exceeded the representative value of the dynamic wheel road, and the increase could be as large as 200% depending on the speed increase. In addition, it was shown that even in the cases in which the maintenance criteria of track irregularities were satisfied, the designed dynamic wheel  
Figure 21: Analysis of correlation between track irregularities and Wheel-Rail interaction force (right rail). load could be exceeded depending on the train speed. This is indicative of the possibility of causing damage to the track owing to the impact load. Therefore, even with the same track irregularities, an impact load exceeding the track impact factor (as considered at the design phase) may be induced depending on the speed of the train in the target section. In the future, the location at which the maximum deformation occurs will be selected based on the numerical-analysis outcomes during the design phase in the cases in which adjacent excavations occur on railway infrastructures; accordingly, stability should be secured by constant monitoring following the installation of an RM sensor in the section with identified vulnerabilities. However, given that the RM sensor measurements may be slightly different from the actual track irregularities of the rail, it is advisable to measure the track irregularities using the Track master before, during, and after the excavation work. In the future, we will study the vertical acceleration of the wheel centers and vibration acceleration. Conceptualization, J.-Y.C., D.-R.P.