延安新区地面沉降时空演化特征时序InSAR监测与分析

Time Series InSAR Monitoring and Analysis of Spatiotemporal Evolution Characteristics of Land Subsidence in Yan’an New District

延安新区以其规模巨大的平山造城工程而备受关注,其快速的工程建设及复杂的地质条件导致了广泛的地面沉降。利用小基线集合成孔径雷达干涉测量(small baseline subset interferometric synthetic aperture radar,SBAS-InSAR)技术对2016-05—2019-10期间获取的升轨Sentinel-1A数据进行处理,分析了延安新区工后地面沉降时空演化特征,探讨了其沉降机理及演化趋势。结果表明,新区的地面沉降区随造地工程由城区向林区发展,其面积随时间总体呈衰减趋势;地面沉降的时间演化经历快速、减缓、平稳3个过程,填方体厚度越大,其累计沉降量越大,沉降稳定所需时间越长。地面沉降主要为填方体自身的固结压缩变形,可分为瞬时沉降、固结沉降、次固结沉降3个阶段,依据不同阶段的特征并结合时序形变,可以对新区的地面沉降过程及其发展趋势进行分析。研究结果可为新区进一步开展沉降监测预警、城市规划建设及灾害防控提供科学的参考依据。

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-1 A 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.