Three-dimensional deformation inversion of mountain excavation and city construction areas using multi-track Sentinel-1 datasets and constraints of strain model and surface-parallel flow

Abstract

Mountain Excavation and City Construction (MECC) projects are common in many mountainous areas to create construction land, but ground deformation during and after MECC projects has not been fully studied. Synthetic Aperture Radar Interferometry (InSAR) is an advanced spaceborne technology to monitor large coverage ground deformation, but existing studies have neglected its horizontal deformation especially in the north-south direction due to its insensibility. As the original terrain of the filling area in the MECC areas is “V” shaped, the filling body can be regarded as a man-made “landslide” with the original slope surface as the sliding subsurface, resulting in the three-dimensional (3D) ground deformation including horizontal and vertical compaction. In this study, an InSAR technique for 3D deformation inversion of MECC areas is proposed by multitrack Sentinel-1 datasets. Firstly, surface height changes and line-of-sight (LOS) deformation are dynamically estimated in the MECC area. Then, the 3D deformation is estimated using strain model (SM) and surface-parallel flow (SPF) constraints. The results of the MECC area in Lanzhou city, China, show that the surface height changes in the MECC area range from −100 m to 75 m, along with the deformation rates in the east-west, north-south, and vertical directions amounting to 110, 80, and 180 mm/year, respectively. The magnitude of vertical deformation is positively correlated to the thickness of the filling loess, with the correlation coefficient of 0.7. Furthermore, the magnitude of the horizontal deformation is positively correlated to the gradient of the thickness of the filling loess, with the correlation coefficient of 0.7 and 0.36 in the east-west and north-south directions, respectively. Finally, the finite difference model (FDM) is employed to simulate the consolidation process in the high fill areas. The real experiments and FDM revealed that the high fill areas experienced both vertical and horizontal deformation, where horizontal consolidation of the filling loess causes the deformation fluctuations in the InSAR LOS direction at the bottom of the ravine.