摘要
北槽大型航道整治工程确定了南北槽分汊口分流界线,阻碍了北槽和邻近滩槽的水沙自由交换过程,使北槽水沙动力过程发生调整。基于工程前后北槽主槽纵向同步水沙观测数据的统计分析表明:入口段落潮优势显著减弱;上段枯季时落潮优势显著减弱,而洪季时落潮优势有所增强;中段(弯曲段拐点附近)落潮优势略有减弱;下段落潮优势明显加强。北槽主槽水沙纵向输移机制分析表明:欧拉余流、潮泵作用、斯托克斯效应和垂向环流为悬沙输移的主要驱动力,其中欧拉余流输沙指向海,斯托克斯输沙和垂向环流输沙指向陆,而潮泵输沙随着季节而变化。洪季,欧拉余流输沙和潮泵输沙在工程前后的变化使大潮期河床冲淤由中段和下段普遍落淤转化为中上段集中落淤。枯季,工程前后稳定的潮流辐散输沙作用使大潮期河床以冲刷为主,但工程后在入口段和上段潮泵的向上游输沙占优势,使悬沙在入口段落淤。
To improve navigability of the major access channel into Shanghai Harbor, a large-scale Deep Waterway Project （DWP） was carried out in the North Passage （NP） of the Yangtze Estuary. Training walls, groins and channel dredging directly transformed the natural geometry of the estuary. Besides, the engineering constructions greatly hindered the exchanges of water and sediment between the NP and adjacent bar areas. Changes in the char- acteristics of hydrodynamics and sediment dynamics were accessed by statistical analysis on the data of flow and suspended sediment concentration （SSC）, which were collected simultaneously at several locations along the main channel of the NP prior to and after the engineering works. The results show that the decreased ebb flow diversion from the South Channel and the overbanking flood tidal currents from the Jiuduan Shoal caused an increase in the flood tidal volume and an decrease in the ebb tidal volume in the distributrary inlet and upper reach, while the con centrating of flow into the main channel by the training walls and groins caused an increase in the ebb tidal volume in the lower reach. The analysis on the mechanisms of sediment transport reveals that Euler residual flow, tidal pumping, Stokes effect and vertical-longitudinal circulation are main forcing agents leading to residual sediment transport. Euler residual flow caused seaward transport, while Stokes effect and vertical longitudinal circulation caused landward transport. Sediment transport due to tidal pumping varied with seasons. During wet seasons, the transports due to Euler residual flow and tidal pumping significantly changed, leading to the change in the along channel distribution of the net sediment transport in a spring tidal cycle, which suggests an overall sediment accu- mulation in the middle and lower reach prior to the DWP but accumulation in the upper half of the middle reach af- ter the DWP. During dry seasons, the divergent pattern of sediment transport due to tidal pumping resulted in sed- iment resuspension in most part of the channel, with sediment accumulation in the distributrary inlet after the DWP.
出处
《海洋学报》
CAS
CSCD
北大核心
2013年第4期129-141,共13页
基金
国家自然科学基金(批准号:50393003
51061130544
40976055)
河口海岸学国家重点实验室开放基金(SKLEC-KF201202)
关键词
长江河口北槽
水动力
泥沙运动
水沙输移机制
冲淤变化
the North Passage of the Changjiang Estuary
hydrodynamics
sediment dynamics
mechanisms of wa ter and sediment transport
erosion and deposition
