Zheng Shuwei, Xu Y Jun, Cheng Heqin, Wang Bo, Lu Xuejun
State Key Lab of Estuarine & Coastal Research, East China Normal University, Shanghai, 200062, China.
School of Renewable Natural Resources, Louisiana State University Agricultural Center, 227 Highland Road, Baton Rouge, LA, 70803, USA.
Environ Monit Assess. 2017 Dec 12;190(1):15. doi: 10.1007/s10661-017-6393-5.
Riverbed scour of bridge piers can cause rapid loss in foundation strength, leading to sudden bridge collapse. This study used multi-beam echo sounders (Seabat 7125) to map riverbed surrounding the foundations of four major bridges in the lower, middle, and upper reaches of the 700-km Yangtze River Estuary (YRE) during June 2015 and September 2016. The high-resolution data were utilized to analyze the morphology of the bridge scour and the deformation of the wide-area riverbed (i.e., 5-18 km long and 1.3-8.3 km wide). In addition, previous bathymetric measurements collected in 1998, 2009, and 2013 were used to determine riverbed erosion and deposition at the bridge reaches. Our study shows that the scour depth surrounding the bridge foundations progressed up to 4.4-19.0 m in the YRE. Over the past 5-15 years, the total channel erosion in some river reaches was up to 15-17 m, possessing a threat to the bridge safety in the YRE. Tide cycles seemed to have resulted in significant variation in the scour morphology in the lower and middle YRE. In the lower YRE, the riverbed morphology displayed one long erosional ditch on both sides of the bridge foundations and a long-strip siltation area distributed upstream and downstream of the bridge foundations; in the middle YRE, the riverbed morphology only showed erosional morphology surrounding the bridge foundations. Large dunes caused deep cuts and steeper contours in the bridge scour. Furthermore, this study demonstrates that the high-resolution grid model formed by point cloud data of multi-beam echo sounders can clearly display the morphology of the bridge scour in terms of wide areas and that the sonar technique is a very useful tool in the assessment of bridge scours.
桥墩的河床冲刷会导致地基强度迅速丧失，从而引发桥梁突然坍塌。本研究于2015年6月至2016年9月期间，使用多波束回声测深仪（Seabat 7125）对长江河口（YRE）700公里下游、中游和上游四座主要桥梁基础周围的河床进行测绘。利用高分辨率数据来分析桥梁冲刷的形态以及大面积河床（即长5 - 18公里、宽1.3 - 8.3公里）的变形情况。此外，还使用了1998年、2009年和2013年收集的以往水深测量数据来确定桥梁河段的河床侵蚀和淤积情况。我们的研究表明，长江河口桥梁基础周围的冲刷深度达到了4.4 - 19.0米。在过去5 - 15年里，一些河段的河道总侵蚀深度达到了15 - 17米，对长江河口的桥梁安全构成了威胁。潮汐周期似乎导致了长江河口下游和中游冲刷形态的显著变化。在长江河口下游，河床形态在桥墩基础两侧呈现出一条长长的侵蚀沟，在桥墩基础上下游分布着一条长条状淤积区；在长江河口中游，河床形态仅在桥墩基础周围呈现出侵蚀形态。大型沙丘导致桥梁冲刷处出现深切和更陡峭的等高线。此外，本研究表明，由多波束回声测深仪的点云数据形成的高分辨率网格模型能够清晰地显示大面积桥梁冲刷的形态，并且声纳技术是评估桥梁冲刷的一种非常有用的工具。
