Jeongho Oh

Railway settlement requires long-term monitoring with millimeter-level accuracy; however, conventional leveling provides limited spatial coverage and requires considerable field effort. This study presents a practical assessment of selected StaMPS parameter settings for ComSAR-based railway settlement monitoring using Sentinel-1 InSAR, with conventional StaMPS PS-InSAR used as a comparative workflow. A ComSAR-based compressed interferogram stack and a conventional PS-InSAR workflow were applied to a section of the Honam High-Speed Railway using 61 Sentinel-1A IW SLC scenes acquired between 28 December 2018 and 29 December 2020. Track Concrete Layer (TCL) leveling data acquired at three annual epochs in December 2018, 2019, and 2020 were projected onto the radar line of sight (LOS) using local incidence angles. The InSAR LOS displacement time series were then compared with the leveling-based linear reference trend using trend-referenced RMSE and a 5 m spatial matching criterion. Four StaMPS parameters were evaluated: spatial resampling grid size before unwrapping (unwrap_grid_size), Goldstein filter window size (unwrap_gold_n_win), temporal window for phase unwrapping (unwrap_time_win), and temporal low-pass filtering window (scn_time_win). A univariate parameter-effect assessment was conducted, in which each parameter was varied individually while the remaining parameters were held at their reference settings. Among the four parameters examined, unwrap_grid_size produced the clearest first-order RMSE response in the ComSAR-based workflow under the reference settings used in this study. Grid sizes of 10–20 m produced clear degradation in trend-referenced validation performance, with the RMSE increasing to approximately 6.7–7.4 mm, whereas 40 m was the smallest tested grid size that recovered practically stable RMSE-based validation performance, at approximately 5.58 mm. In contrast, unwrap_gold_n_win, unwrap_time_win, and scn_time_win produced only small or localized numerical RMSE variations, with no consistent deterioration trend across the tested settings. The conventional PS-InSAR workflow also showed relatively stable RMSE-based validation performance across the tested parameter ranges, with RMSE values of approximately 4.87–4.91 mm. These findings provide case-study-based practical guidance for selecting StaMPS parameter settings in ComSAR-based railway settlement monitoring.

1. 서 론 최근 남북철도 연결 및 현대화를 위한 북쪽의 경의선 및 동해선 구간에 대한 공동조사가 시행되었으며 향후 이를 발판으로 유라시아 철도 연계 실현에 대한 관심이 증대하고 있다. 북한은 여객수송의 약 60%, 화물수송의 약 90%를 철도가 분담하는 교통체계를

This study presents the two-row self-supported retaining wall method using steel pipe piles to improve the constructability and stability of underground structures constructed in urban areas. Herein, the behavior of steel piles was investigated by numerical analysis and laboratory model tests employing 3D (Three dimensions) printing, considering various design factors such as the soil condition, pile connector, wall spacing, and traffic load. The results indicated that the horizontal displacement of the walls was significantly reduced regardless of the ground conditions when the spacing between walls was 1.0 m along with the pile connector installation. To the end, the efficiency of recycling steel piles during excavation was also examined based of laboratory test to achieve economical construction cost.

Porous asphalt pavement is a part of the permeable pavement system, which can be used to mitigate the negative impacts of urbanisation on the water hydrological cycle and environment. This study aims to assess the mechanical and hydrologic characteristics of porous asphalt pavements, with and without geocell composites, using a plate load test, falling weight deflectometer test, and rainfall simulation test. The corresponding results indicate that the elastic modulus of the unreinforced pavement is lower than that of the reinforced pavement. The analysis demonstrates that the use of geocell composites effectively increases the load-bearing capacity of the pavement. When the base layer is reinforced with geocells, its load-bearing capacity increases. Observation of the rainfall simulation tests on the reinforced pavement indicates that the reinforced pavement effectively handles the surface runoff.

The ballastless plate girder bridge, classified as a structure type that requires an emergent replacement among domestic railway bridges, generally tends to upgrade to a ballasted track along with continuous welded rail (CWR). The axial forces of the CWR due to the temperature change need to be distributed to the bridge foundations. Because most of the existing ballastless plate girder bridges of over 50 years of age do not provide any design information, such bridge foundations are regarded as unknown foundations, and therefore, it is crucial to identify the structural adequacy and dimension. In this study, an effort was made to establish a correlation between the standard penetration test (SPT) and mid-size pneumatic cone penetration test (MPCP) to estimate the load bearing capacity of an unknown foundation. A field test was conducted to estimate the depth of the unknown foundation by employing SPT and MPCP as the source wave part. The magnitude of the shear wave was mitigated by the presence of PVC and steel pipes, such that it might be possible to identify the embedment depth of unknown foundations.

Construction of underground box structures that underpass existing infrastructures or facilities at shallow depths is being widely conducted in urban areas in order to avoid the interference of existing structures without the rerouting of traffic. Consequently, it is crucial to ensure safety during and after construction by monitoring the ground settlement induced by underground box installations that can be influential for the existing various structures. This paper provides a method to assess the risk potential around underground box structures with artificial neural networks (ANN), taking into account input variables that can be monitored in the field. By introducing the numerical methods and ANN, the probability of failures considering the variability of design parameters such as ground conditions, structure sizes and shapes, traffic loads, and presence of existing structures could be assessed and utilized for the safe construction of underground box structures at shallow depths. Experimental programs were also performed to investigate the effect of the umbrella method, which contributes to the decrease of risk potential in a practice. A limited field test evaluation using ground-penetrating radar (GPR) along with a pneumatic dynamic cone penetrometer (PDCP) was found to be promising in the assessment of risk potential at shallow depths.