延安新区地面沉降分布及影响因素的时序InSAR监测分析

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

陕西省延安新区的“平山造城”是目前世界上在湿陷性黄土沟壑地区规模最大的岩土工程。大规模的土地创造、工程建设及复杂的工程地质条件,引起了大量的不均匀地面沉降。首先利用合成孔径雷达干涉测量(interferometric synthetic aperture radar,InSAR)技术对2017-12—2018-12期间获取的升轨哨兵1号A星(Sentinel-1A)数据进行分析,获取了延安新区平山造城工程工后的地面沉降分布特征,并通过实地调查验证了InSAR技术探测结果的可靠性,然后讨论分析了影响地面沉降分布的主要因素。结果表明,延安新区工后地面沉降主要分布在填方区,最大形变速率达120.1 mm/a。填方工程中黄土的重塑及其物理力学性质的改变是填方区地面沉降的主要内在因素,挖填方工程和填方体厚度是地面沉降分布与大小的主要控制因素,人类活动和地质环境的改变也会加速地面沉降的发展。时序InSAR技术可为黄土重大工程灾害隐患的早期识别提供有效的技术手段,为进一步开展监测预警、规划建设或科学防控提供依据。

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.