基于多模态传感器系统的长江下游窝崩边坡稳定性分析

Stability analysis on arc collapsing channel slope in the lower reaches of the Yangtze River based on multimodal sensor system

2016年9月利用Sea Bat-7125多波束测深仪、Riegl-VZ-4000三维激光扫描仪、Edgetech-3100p浅地层剖面仪、双频ADCP、Trimble-差分GPS、RTK等组成的多模态传感器系统,对长江铜陵太阳洲水道凹岸河段窝崩边坡的沉积地貌和水动力特征进行陆上与水下联合测量和三维地形数据的融合研究,计算分析边坡整体稳定性及其发展趋势。结果表明:该河段发育的窝崩呈内凹型三级阶梯状冲蚀结构,陆上边坡坡比0.09~0.25,水下边坡坡比0.33~0.55,窝崩坑崩坍土方量15 246 m3,坡脚和近岸区均存在崩坍堆积体。坡脚表层沉积物属细砂-中砂质地,中值粒径为152.7μm,窝崩区及近岸区堆积层厚度3~5 m。窝崩坑内水流呈直径50 m的竖轴回流,表层平均流速0.22 m/s,中层平均流速0.30 m/s,底层平均流速0.14 m/s,其对边坡土体持续淘刷,并和近岸堆积体共同作用使窝崩朝西北向环形扩展,边坡稳定性较差。

Measurements of arc collapsing channel slope in Tongling reach of the Yangtze River were made in Sep- tember 2016. We deployed integrated SeaBat-7125 multi-beam sonar, Riegl-VZ-4000 terrestrial laser scanner, Edgetech-3100p sub-bottom profiler, ADCP, Trimble-DGPS and RTK to build a multimodal sensor system to directly measure morphological, hydrodynamic and sedimentary characteristics of the arc collapsing area. We integrated the point cloud data of submerged portions of the slope with the non-submerged portions to achieve visualization of 3 D morphology of channel slope. Then we evaluate the stability and development trend of the arc collapsing with measurement results. The results show that the arc collapsing is concave with three ladder-like distribution in morphological characteristics, slopes of the non-submerged portions are between 0.09 - 0.25, while the submerged slopes have reached 0.33 - 0.55. The collapsed bank material is 15 245.8 m3 and submerged blocks of failed bank materials which is 3 -5 meters thick were found at the bank toe. The riverbed is mainly formed with fine sand and medium sand, of which the medium particle size is 152.7 μm. ADCP data reveals that the recireulating flow with spead of 0. 14 - 0. 30 m/s is created within the arc collapsing and the combined effects of large-scale recirculation flow and the submerged slump block, therefore the location of erosion at the north-west embayment and the stability of the arc collapsing is poor.