PSI技术在苏通大桥基础沉降监测中的应用

Application of PSI Technology in Foundation Settlement Monitoring of Sutong Bridge

苏通大桥桥位区河床松软覆盖层厚约300m,主塔群桩基础由131根直径2.8m/2.5m、长117m（北塔）/114m（南塔）的钻孔灌注桩组成,桩径比仅2.29,群桩沉降问题非常突出。已有研究表明,常规的地面变形观测方法及精密传感器监测技术都具有一定的局限性。为此,将新兴的永久散射体干涉测量（Permanent Scatters InSAR,简称PSI）技术应用于苏通大桥地基基础沉降监测。结合大桥自身的PS特性和桥位区重点监测部位的CR,利用该地区2003年~2007年（主体工程施工期间）间获取的12景ENVISAT卫星SLC数据和外部的SRTMDEM进行＂二通＂模式D-InSAR,从而得到施工过程中不同阶段的雷达视线向形变图,转换后得到地面竖向变形分量,客观、全面地反映了苏通大桥在建设过程中基础的沉降。将差分干涉测量的沉降结果与多种高精度传感器监测结果对比,两者具有很好的一致性。研究结果表明,PSI技术是一种极具潜力的大型桥梁地基基础沉降监测技术,可获得可靠的、具有mm级精度的观测结果。随着监测区SAR数据的不断累积,备受关注的南、北主墩的高精度的沉降量也将逐步得到解算。

In Sutong bridge region,the depth of the riverbed soft overburden is about 300m,the pile group foundation of main cable tower is constituted of 131 cast-in-place bored piles with the diameter of 2.8m/2.5m and the length of ll7m（north tower）/ll4m（south tower）, and the ratio between pile spacing and pile diameter is only 2.29, which lead that it is a very outstanding question for the settlement of pile group. It has been reported that general observation methods on ground deformation and exact sensor monitoring technology both show spatio-tempelal limita- tion. For this reason, the rising permanent scatters InSAR （PSI） technology is applied in the settlement monitoring for foundation of Sutong bridge. Combing with the PS characteristics of the bridge and CaR which is set up in the key monitoring site at bridge region, by processing 12 scenes SLC data of ENVISAT acquired in 2003 ~ 21X17 （The main project is in the construction period）and external SRTM DEM,＂Two-pass＂ mode D-InSAR is done, thus slant range deformation in different periods are obtained,and it is further switched to obtain surface vertical defonmtion.It re- fleets the settlement of the bridge＇s foundation in the process of construction objectively and roundly. Comparing set- tlement results gained by D-InSAR with high-precision muir-sensors,they have good coherence. The study resnlts in- dicate that PSI technology is a powerful technology to monitor the foundation settlement of the huge bridge＇s founda- tion and the observation result is reliable and has the precision of millimeter level. Along with continuous accumula- tion of SAR data in the monitoringarea,high-precision settlement of the south and the north main piers will be gradually calculated.