Satellite based forensic MSRS monitoring system for detecting settlement of urban underground

Along subway corridors, ground settlement can occur above the track alignment due to construction activities associated with installation and maintenance, as well as changes in the surrounding environment. Because occurrence locations are difficult to predict in advance, continuous monitoring over a wide corridor is required; however, conventional in situ measurement techniques have limitations in providing continuous observations over large areas simultaneously. To address this gap, prior studies have proposed pairwise combinations of two techniques, such as InSAR with ground-penetrating radar (GPR) or InSAR with laser scanning; however, integrated interpretation can be constrained by scale mismatches between techniques. This study advances these efforts by integrating satellite InSAR, laser scanning (L/S), and GPR into a staged framework linking wide-area monitoring, site-specific validation, and near-surface condition assessment along an urban subway corridor. First, long-term surface deformation was analyzed using InSAR over the Seoul Metropolitan Subway Bundang Line corridor between Suseo Station and Cheongnyangni Station (approximately 16 km), and ventilation shafts exhibiting settlement signals pronounced relative to the surrounding area were selected as vulnerable sites. Subsequently, L/S was conducted at the selected shafts to precisely evaluate the interior ceiling geometry and the spatial distribution of deformation, and GPR surveys were performed on the overlying road to examine subsurface conditions. Finally, by cross-comparing the InSAR, L/S, and GPR results, a staged MSRS workflow is presented to supplement and interpret settlement anomalies detected by wide-area monitoring with field-based evidence along urban railway corridors.