Multi-Temporal-InSAR Ground DeformationMapping of Beijing Subway NetworkBased on ALOS-2 and Sentinel-1 Data

Land subsidence is a geological process that occurs at a slow and persistent pace. However, due to the limited archive of high-resolution SAR images, the single-sensor Multi-temporal Interferometric Synthetic Aperture Radar (MTInSAR) technology is unable to satisfy the demands of long-term and high-resolution deformation monitoring. To address this issue, we employed a Small Baseline Subset of InSAR technology, using ALOS-2 and Sentinel-1 data, to detect the deformation characteristics of the Beijing Subway Network (BSN). The two datasets produced consistent results regarding the evolution process and spatial distribution. Subsidence monitoring can be sustained using other datasets when high-resolution images are insufficient. To investigate the differences in deformation characteristics at different stages, we focused on the newly opened section of Beijing Subway Line 17 (L17). Our findings revealed that the southern portion of L17 posed a significant risk of instability with subsidence occurring at Jiahuihu Station, Ciqu Station, and Ciqubei Station. The deformation at these stations was 12.8 mm, 18.7 mm, and 5.6 mm, respectively. Before and after the opening of L17, their deformation rates changed. Specifically, the deformation rate at Jiahuihu Station decreased from -9.4 mm/year to -5.5 mm/year, the deformation rate at Ciqu Station decreased from -14.1 mm/year to -7.5 mm/year, and the deformation rate at Ciqubei Station decreased from -4.9 mm/year to -1.5 mm/year. These results indicate that, after the subway's opening, the deformation rates at these stations are decreasing. The deformation along the subway will intensify during construction and then gradually stabilize once it is operational.