Analysis of Land Subsidence Distribution and Influencing Factors in Yan'an New District Based on Time Series InSAR

  Objectives  The "mountain excavation and city construction" in Yan'an New District is the largest geotechnical project in the collapsible loess gully region. Large-scale land creation, engineering construction and complex engineering geological conditions has caused a large number of uneven land subsidence, which is posing an increasing threat to the stability of urban infrastructure and public safety.

  Methods  The ascending Sentinel-1A data stacks obtained during December 2017 to December 2018 were analyzed using the time series interferometric synthetic aperture radar (InSAR) technique, and the distribution characteristics of the post-construction land subsidence of the mountain excavation and city construction in Yan'an New District were obtained. The reliability of the detection results of InSAR technology was demonstrated by field investigation. Finally, based on the deformation monitoring results, the main influencing factors of land subsidence distribution were analyzed.

  Results  (1) The results show that significant uneven land subsidence formed after the mountain excavation and city construction in Yan'an New District is mainly distributed in the filling area, and the maximum deformation rate reaches up to 120.1 mm/a. Field investigation validates the reliability and accuracy of the deformation results. (2)The remodeling of original loess and the change of its physical properties during the filling process is the main intrinsic factors of land subsidence in the filling area. Large-scale land creation determines the distribution of land subsidence, and the thickness of the filling are the main controlling factor of the distribution and size of land subsidence. In addition, human activities and changes in the geo-environment will also accelerate the development of land subsidence.

  Conclusions  In order to achieve the early detection of potential geo-hazards and active risk prevention in the site selection and feasibility study stage of mega engineering projects in the Loess Plateau, the time-series InSAR technology can provide an effective technical that allows for the early detection of potential geo-hazards such as land subsidence and landslides, and provide a scientific basis for further monitoring and warning, planning and construction, geologic disaster prevention.