时序InSAR解析消落带区域岸坡地表形变及其水要素影响

A time-series InSAR-based analysis of surface deformation of hydro-fluctuation belts and the effects of hydrological elements

消落带区域多发生地质灾害,因此理清库水位、降雨等因素在消落带区域地表形变中的作用对于地质灾害预警及防治具有重要意义。为此,采用短基线集差分干涉测量技术对三峡库区奉节段2018年7月—2020年7月的63景Sentinel-1A升轨影像进行地表形变反演,结合地面监测点进行对比界定,通过形变量-库水位-月降雨量的时间序列图进行水要素分析。获得结论如下:①库水位变化和降雨是造成地表形变的重要因素,库水位变化对坡体影响主要体现在浮托减重效应和坡体内外的水位差,而降雨会减弱坡体的抗剪强度同时增加坡体自重进一步增加形变;②库水位变化快则地表形变大,库水位变化慢则地表形变小;③降雨与地表形变成正比,极强降雨时降雨完全主导着地表形变;④研究区地表总体稳定,但消落带邻近区域发现2个形变异常区域:异常区域年形变速率超过30 mm/a,区域内最高形变速率可达89 mm/a。结论具有较强的理论和实用价值,可为消落带区域地质灾害精准防治提供科学支撑。

Hydro-fluctuation belts are frequently struck by geological disasters.Therefore,ascertaining the effects of hydrological factors such as reservoir water level and rainfall on the surface deformation of these belts is of great significance for the early warning,prevention,and control of geological disasters.Based on 63 scenes of Sentinel-1 ascending images of the Fengjie section of the Three Gorges Reservoir Area from July 2018 to July 2020,this study conducted the inversion of surface deformation using the small baseline subset interferometric synthetic aperture Radar(SBAS-InSAR)technique.The inversion results were compared with the data of ground monitoring points,and the hydrological elements were analyzed using the time series diagrams of deformation,reservoir water level,and monthly rainfall.The conclusions are as follows:①The change in the reservoir water level and rainfall are important factors causing surface deformation.The effects of the change in the reservoir water level on the slope are primarily reflected in the buoyancy effect and the water level difference inside and outside the slope.In comparison,rainfall can decrease the shear strength and increase the dead weight of the slope,thus further increasing the deformations;②Quicker change in the reservoir water level corresponds to larger surface deformation,and vice versa;③Rainfall is directly proportional to surface deformation and totally dominates the surface deformation in the case of extremely heavy precipitation;④The surface of the study area is stable overall.However,two deformation anomaly zones have been found near the hydro-fluctuation belt.They have annual deformation rates of over 30 mm/a,with a maximum of up to 89 mm/a within the anomaly zones.The above conclusions have high theoretical and practical values and can provide scientific support for the accurate prevention and control of geological disasters in hydro-fluctuation belts.