黑方台地表三维形变分析

摘要

The loess has strong collapsibility in Heifangtai Platform, Yongjing Country, Gansu Province which belongs to a typical loess platform. Collapsible loess of thick layer caused by long-term flood irrigation has induced many loess landslides and severe ground deformations. We selected ground deformations in Heifangtai Platform as research object. The descending data of Sentinel-1 A satellite in three different orbits were processed using PSInSAR technique between 2014 and 2017, and the deformation in different line of sight (LOS) is obtained. In addition, 3 D ground surface deformations was obtained by inversion and calculation in the area. Ground surface deformations of LOS direction, vertical and horizontal direction was analyzed, and the development trend of ground surface deformation was predicted. The results show there are differential settlements in study area. The deformation rates of LOS direction are larger in some area including closing to central area of platform and the part of area on the edge of platform. The range of settlement is 4 ～ 13 mm·a-1. A region with large vertical deformation is near themiddle of platform. The average rate of deformation is-20 ～-6 mm·a-1. The North-South deformations are small.The average rate of deformation is-5 ～ 5 mm·a-1. However, the West-East deformations are large. The average rate of deformation is mostly more than 20 mm·a-1. Ground surface deformations are still at a slow acceleration stage in short term as a whole. With continuous development of agricultural irrigation, the rate of ground surface deformation will gradually decrease after rising a certain value.%甘肃省永靖县黑方台属于典型的黄土台塬,其黄土具有较强的湿陷性,长期的大水漫灌引起厚层黄土发生严重的湿陷现象,进而诱发滑坡及严重的地面变形.本文以黑方台地表变形为研究对象,采用PS-InSAR技术对2014～2017年期间Sentinel-1 A卫星3条轨道的降轨数据进行处理,得到了不同视线(LOS)方向的变形,进而通过反演和计算得到该地区三维地表形变信息,分析了视线向、垂直向以及水平向的地表变形特征,预测了未来的发展趋势.结果表明:在靠近台塬中部区域以及塬边部分区域的视线向变形速率较大,沉降范围为4～13 mm·a-1;垂向变形较大的区域大都靠近台塬中部,平均变形速率为-20～-6 mm·a-1;整个台面南北向变形很小,平均变形速率为-5～5 mm·a-1,东西向变形较大,平均变形速率大都超过20 mm·a-1.研究区属于不均匀沉降区域;整体来看,研究区的地表变形在短期内仍然处于缓慢加速发展阶段,随着农业灌溉的持续进行,研究区地表变形速率达到一定值后会逐渐下降.