Objectives Yan'an New District has attracted much attention because of its large-scale mountain excavation and city construction project. Such mega-scale land creation, rapid urban construction and complex geological conditions has induced wide land subsidence in the region.
Methods In this paper, the temporal and spatial evolution of land subsidence in Yan'an New District was assessed using small baseline subset synthetic aperture radar interferometry (SBAS-InSAR) to process the Sentinel-1A images covering the period from May 2016 to October 2019. Then, the mechanism and evolution trend of land subsidence in the new district was analyzed.
Results Experimental results suggest that the spatial evolution pattern of land subsidence in Yan'an New District is highly relevant with the process of land creation project. The land subsidence area in the new district gradually expanded from the major urban area to the area of forest along with the land creation project, and its area decreased gradually with the passing of time. The temporal deformation evolution of land subsidence in the new district is related to the thickness of the fill, and all exhibit non-linear subsidence with various velocities. The temporal evolution of land subsidence undergoes three processes of rapid-slow-steady. The greater the thickness of the fill, the larger the amount of sedimentation, the longer it takes for the sedimentation to stabilize.
Conclusions The main internal mechanism of land subsidence is the consolidation and compression deformation of the loess fill, which can be divided into three stages: Instantaneous settlement, consolidation settlement, and secondary consolidation settlement. Based on the characteristics of different stages combined with time series deformation, the land subsidence process and development trend can be analyzed. The research results provide a scientific reference for further monitoring and early warning, urban planning, and prevention and control of subsidence disasters in the new district.
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