基于SBAS-InSAR的珠江口万顷沙区域软土地面沉降时空特征与演化机理

    Spatial and temporal characteristics and evolutionary mechanism of surface subsidence in Wanqingsha soft soil area in Pearl River Estuary based on SBAS-InSAR

    • 摘要: 快速城市化加深了珠江口地区的人地矛盾,数十年间的填海造陆诱发了广泛的地面沉降灾害,严重制约区域经济、社会和生态的协调发展。聚焦珠江口的万顷沙区域,选取2015年12月至2016年12月间24景C波段Sentinel-1A升轨SAR影像,利用小基线集合成孔径雷达干涉测量技术(Small Baseline Subset Inter-ferometric Synthetic Aperture Radar, SBAS-InSAR)技术,结合高精度实地钻孔监测数据,开展研究区地面沉降时空特征和演化机理研究,特征结果表明: 研究区整体年均沉降速率为-9.45 mm/a,以南沙港口最为严重,呈现由内地向沿海不断递增的沉降速率格局,经历点-片-面、缓-快-稳的沉降趋势,累积沉降相继出现南沙港口、沙仔村及南沙湾3处典型沉降中心。机理结果表明: 地面沉降在以软土发育为主的脆弱地质环境下孕育发展,并在演化过程中受到地面荷载、降水补给的外力影响。研究成果可为人地矛盾激烈的城市建设和未来发展规划提供科学依据,为海陆交互相软土广布地的地面沉降监测预警和灾害防控提供技术支撑。

       

      Abstract: Rapid urbanization has stimulated the human-land conflict in the Pearl River estuary. Several years of land reclamation have induced serious ground subsidence disasters, which seriously constrains the coordinated development of economy, society and ecology. The authors in this study focused on Wanqingsha area in the Pearl River Estuary and selected 24 views of C-band Sentinel-1A uplinked SAR images between December in 2015 and December in 2016. The SBAS-InSAR technique and high-accuracy borehole monitoring data were used to extract spatial and temporal characteristics and evolutionary mechanism of the surface subsidence. The research results indicated that the overall average sedimentation rate in the study area was -9.45 mm/a, and the most significant area is Nansha Port. It showed a pattern of increasing subsidence rate from the interior to the coast, and experienced the trend of point-sheet-surface, slow-fast-steady subsidence. Three typical subsidence centers were Nansha Port, Shazai Village and Nansha Bay. The mechanistic results showed that ground settlement was nurtured and developed in a fragile geologic environment dominated by soft soil development. And it was externally influenced by ground loading and precipitation recharge during the evolutionary process. The study results could provide references for urban planning and development under the background of growing contradiction between people and land, and technical support for monitoring and early warning of ground settlement and disaster prevention and control in the wide area of soft soil where the sea and land intersect.

       

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