Preliminary risk assessment of metro lines subjected to adjacent disturbance with time-series InSAR

The urban metro system is a crucial infrastructure for sustainable urban development. However, ground engineering disturbances, such as foundation pit excavations and overloading, can cause damage to the metro structure, including cracks and water leakage. By integrating small baseline subset synthetic aperture radar interferometry (SBAS-InSAR) technology, this study develops a preliminary risk assessment methodology for metro lines that are subjected to ground engineering disturbances. A relevant case from Changsha was proposed, spanning from January 2017 to July 2023, using a dataset of 147 Sentinel satellite images. Key findings include: (1) InSAR technology effectively monitors ground settlement, the areas with significant construction activities, the average annual settlement rate typically exceeds −6 mm/yr, with some regions reaching up to −10mm/yr. In contrast, most areas without ground disturbance usually experience surface settlement not exceeding −2 mm/yr. (2) Satellite imagery analysis of metro areas with settlement differences greater than 20 mm revealed that most of these regions are influenced by foundation pit excavation, and some regions may be influenced by soil consolidation. (3) Overall, metro lines in Changsha have a low risk level, with certain areas classified as “ high risk”. In the high-risk sections, Line 2 and Line 6 account for 32.7% and 20%, respectively, and regular inspections are required. This study would be beneficial to sustainable urban transportation.