内河入海闸上桥梁冲刷特征与桩基缺陷分析

Analysis on Scouring Characteristics and Pile Foundation Defects of Bridge on Inland River Estuary Sluices

摘要:

为掌握长三角某内河入海闸上2座特大型桥梁的河床冲刷及水下桩基状况，采用三维声呐图像系统、测深仪及潜水员人工探摸等方式全面检测了该桥水下基础。检查发现：在流域整体趋于冲刷的背景下，2座大桥均存在较为严重的河床冲刷，其中距泄洪闸1.2 km的A桥存在显著的由泄洪引发的局部冲刷，距泄洪闸12.3 km的B桥，因大闸泄洪、河道收窄和群桩效应等多因素作用造成更严重的束窄冲刷和局部冲刷，导致其主墩群桩钢护筒底部裸露1.0～4.5 m。研究结果认为，内河入海口的闸上桥梁由于存在经常性泄洪所面临的冲刷问题比较严重，需要桥梁设计、施工及管养单位重视后期面临的冲刷风险，定期进行水下检测并对症施策。

Abstract:

To assess the riverbed scour and underwater pile foundation conditions of two super-large bridges located on an inland river estuary sluice in the Yangtze River Delta, a three-dimensional sonar image system, depth sounders and manual exploration by divers are adopted to comprehensively inspect the underwater foundation of the bridge. The inspection reveals that against a background of overall watershed scour, the two bridges are suffering from relatively severe riverbed erosion, suffered from severe riverbed scour, in which the A bridge, 1.2 km away from the flood discharge gate, has significant local scouring caused by flood discharge, and the B Bridge, 12.3 km away from the flood discharge gate, has suffered from more severe narrowing and local scours due to multiple factors such as the flood discharge from the main gate, the narrowing of the river channel and the group pile effect, resulting in the bottom of the steel casing of the main pier group pile being exposed for 1.0 to 4.5 m. The conclusion shows that bridges on the inland river estuary sluices face serious scouring problems due to frequent flood discharge. Therefore, bridge design, construction and maintenance units need to pay attention to the scouring risks in the later stage. The regular underwater inspections are conducted and the targeted measures are taken.