【作者】 万新宁；

【导师】 李九发；

【作者基本信息】 华东师范大学 ， 自然地理学， 2008， 博士

【摘要】 洋山海域位于崎岖列岛南北岛屿群之间,具有明显的峡道地形特点,自然状态下该海域涨、落潮水流迅急,且落潮流强于涨潮流,在岛屿峡道效应作用下,水流产生聚能,同时在波浪的叠加下,成为崎岖列岛周边海区冲刷和泥沙运移的主要作用力。峡道区流急、悬沙浓度高、泥沙运移强而落淤少,这是自然状态下洋山海域峡道效应的显著特点。由于其具有良好的水深条件,2002年6月上海国际航运中心洋山深水港区工程在此开工实施,工程实施过程中,在洋山海域先后进行了堵汊工程、吹填工程和疏浚工程等。工程实施后,小洋山北岛链的三个主要汊道已被封堵,改变了原有的峡道地形,水动力结构、泥沙分布及地形冲淤演变等都相应地发生了变化。工程实施后对于洋山海域潮流场最大的改变就是涨落潮流优势的转变,主通道内由落潮动力占优势的格局逐步向涨落潮动力均衡的方向发展,这种变化在东口门尤为显著,由于落潮流下泄不如堵汊前顺畅,东口门附近出现了壅水现象。而作为北岛链上唯一没有封堵的汊道,通过颗珠山～蒋公柱汊道的涨落潮量也有增有减,但始终保持落潮流优势,且较为稳定,正是由于这条出水汊道的存在,才使得颗珠山汊道附近水域成为为数不多的冲刷区域。相关分析表明,工程实施后洋山海域在宏观上仍受周边海域大环境的泥沙场制约,工程前后含沙量没有异常变动。但由于峡道地形的改变,局部含沙量分布发生了一些变化。自然状态下,由于岛屿周边紊流的影响,会形成局部高含沙区域,但汊道封堵后,小洋山北岛链前沿水域基本形成了平顺的岸线,主通道内含沙量等值线分布较为均匀。同时,在自然状态下,洋山海域存在着底部高含沙水体,随着工程的实施,虽然底层含沙量仍然高于表层含沙量,但表底层的差异与工程前相比已经明显减小。工程前后,洋山海域主通道的泥沙来源及其颗粒成分基本不变。在这样的条件下,主通道底质的粗、细分布,主要与该区的水动力有关,而由于潮动力的变化,洋山海域总体上形成弱淤积环境,洋山海域的沉积物经历了总体由粗到细、局部区域存在粗化现象,沉积物的变化是对洋山海域的峡道地形改变的直接响应的结果。随着洋山海域汊道封堵工程、吹填工程和疏浚工程的不断实施,洋山海域主通道内的地形也发生了明显的调整变化,淤积范围不断扩大。北岛链汊道封堵后,洋山海域水流动力减弱,悬浮的泥沙颗粒易于沉降,在此背景下,吹填沙泄漏以及疏浚抛泥区的选择等都造成了大范围淤积的产生,但是其中由堵汊工程产生的峡道地形边界改变及其相应的流场变化才是根本原因所在;同时实测资料表明潮周期过程中的最大含沙量主要出现在涨落憩前后。也就是说,高低潮前后流速最低,而含沙量最高,这成为最有利于泥沙落淤的时刻,是研究区域的泥沙淤积的重要因素。此外在实施了疏浚工程的区域内,疏浚增加了局部区域水深,随着疏浚水深的增加淤积强度呈递增趋势。总体看来,由于小洋山北岛链各主要汊道的先后封堵,从根本上改变了原有的地貌形态,形成了新的峡道地形,从而改变了峡道内的水动力、泥沙、地形等综合峡道效应,这种变化仍处于调整过程中。更多还原

【Abstract】 Yangshan sea area lies in the Qiqu Archipelago, the south of Changjiang Estuary, the west of East China Sea, the outside north of Hangzhou Bay, and on the south-east of Luchaogang of Nanhui. Its dynamical characteristics of water current and suspended sediment are very complex because of its unique trumpet-shape and topography of strait. Its characteristic of dynamic condition is decided by the contrast of the forces between river runoff and tide flow and wave. The transportation and deposition of sediments are mainly decided by the suspended sediment concentration from Changjiang Estuary and the strength of the flow. Silt transportation and sedimentary mechanism in the area are discussed from dynamics, which shows that rapid current, high suspended sediment concentration and little deposition are themain features of the area.Yangshan Harbor Area of Shanghai International Shipping Center constructed because of the well water-depth condition in June, 2002. The construction of a series of projects changed the natural strait-channel effects of Yangshan Sea Area, the water dynamics, the distribution of sediment and the evolvement of topography etc. The Pattern of ebb-tide dominant has been changed to the balance of ebb-tide and flood-tide, the Kezhushan strait-channel kept the ebb-tide dominant as the only no-blocking strait-channel. And the Yangshan Sea Area has been in the situation of weak deposition.The resource of sediment was controlled by the big environment of adjacent sea area, but the distribution of sediment has changed in some areas because of the changing of strait-channel topography. The isolines of suspended sediment concentration were uniformity in the main routeway after the blocking of strait-channels. The water dynamic decreased, the function of separation and convergence of tidal current disappeared and the coarser particles settled after the construction of project. The sediment changed from coarse to fine and was coarser in some areas, which reflected the strait-channel of Yangshan Sea Area.The evolvement of topography has changed along with the changing of tidal current and the sediment. The range of siltation aggrandized after the construction of project, and the erosion water area occurred in the forefront of dock and Kezhushan strait-channel. The changing of tidal current and topography of strait-channel, the leakage of filling silt and the region of mud casting brought out the big area of siltation. At the same time, the sediment was easy to settle when the time of before and after high tide and low tide because of the minimum water velocity and maximal suspended sediment concentration. Furthermore, the water depth of dredging affects the intension of siltation, which increased with the adding of water depth.Generally speaking, the topography of strait-channel of Yangshan Sea Area, the tidal current and distribution of sediment have changed after the construction of project, and the seabed has adjusted accordingly and the adjustment continued at all times.更多还原