【作者】 左书华；

【导师】 张宁川；

【作者基本信息】 大连理工大学 ， 港口、海岸及近海工程， 2013， 博士

【摘要】 岛群海域环境下的淤泥质海床泥沙运动因受到复杂边界的影响泥沙运动研究的复杂性,目前针对岛屿链不断变化引起的泥沙运动和海床冲淤变化研究尚不多见；有关顺岸式港池淤积计算方法尚不明确。本文以崎岖列岛和洋山港工程为背景,通过遥感影像资料、现场实测水、沙资料分析、潮流数学模型试验、泥沙基本特性及平衡含沙量水槽试验、理论分析等综合研究手段,得到研究背景(岛群)环境下水流运动、岛群内水域海床演变、顺岸挖深港池泥沙淤积计算方法。主要结论研究如下：(1)岛群内水域水流形态及改变岛群边界的影响：自然状态下,崎岖列岛岛屿较多,岸线复杂,岛群内分流、汇流、环流现象明显；潮流是岛群内水域泥沙掀扬与输移的主要动力。人工改变岛群边界(封堵部分岛群链间的潮流通道),将导致岛群链内不同汉道的进出潮量分配发生变化。当岛群边界变化不大时岛群内的总进出潮量基本不变,但进出潮量将重新分配,当岛群边界变化较大时,岛群内的总进出潮量将发生变化(减小)。计算5种边界形态,岛群内主通道水域流速变化情况,从总体上而言,随着陆域边界的变化(即汉道的封堵),岛群内流速的变化呈现出“局部变化”—“变化扩展”—“变化趋于平稳”—“变化进一步增大”的不连续过程；当岛群链边界改变到一定程度后,岛群内水域流速变化较大,对后期工程开发不利。(2)岛群内水域泥沙基本物理特性：悬沙粒平均中值粒径dso为0.008mm,为细粉砂-极细粉砂类型；海床沉积物主要以粘土质粉砂(YT)为主,平均中值粒径D50=0.030mm;多年底质中值粒径总体变化不大。底床泥沙容重为1.34t/m3时,水流作用下的起动摩阻流速为2.07cm/s,起动时平均流速为54cm/s；沉降速度受水流流速、含沙量、盐度等因素的综合影响：水流速度越大,沉降速度越小；沉速随含沙量的增大先增大后减小,在同一水流和初始含沙量条件下,沉降速度随沉降量的增大而减小；研究海域平均沉降速度0.005cm/s左右。(3)悬沙含沙量时间、空间分布特性及其分类：含沙量在时间上分布的不均匀性,主要是受潮位、流速等动力因素的影响导致的。含沙量在空间上(短期)分布与流速和背景含沙量有关。在潮流涨落潮的一个周期时段内,流速、流向在不断变化。垂线含沙量分布分为“下抛物型——沉降型”和“上抛物型——起悬型”两类含沙量,基于现场观测资料分别拟合给出了“沉降型”和“起悬型”含沙量计算公式,给出了含沙量影响系数(ap)。(4)基于分类含沙量,提出了淤泥质海床冲淤判别指标；考虑进出岛群链内水域各潮流通道的流量分配和基于含沙量垂向分布分类方法,建立了适用于岛群海域环境下淤泥质海床冲淤演变预测的便捷计算方法(5)在分析顺岸式港池内水流特征的基础上,建立顺岸式港池内的流量平衡方程和和水体运动方程,然后基于水流连续条件将顺岸式挖深港池的内流速变化归结为“水流归槽指数n”的变化,给出了固定相对挖深条件下,以港池长宽比L/B为参数的n计算公式；,进而基于平衡含沙量理论,建立了考虑“水流归槽指数n”和“平衡含沙量指数m”的顺岸式港池泥沙淤积预报公式。更多还原

【Abstract】 In China, due to reasons such as siltation available deepwater coastline has developed at the estuary and coast. There are many difficulties to transform the old harbors in our country at present. But the deep development of islands shoreline has a great potential for exploitation. Therefore the development to deep-water port coastline of archipelago waters will not only effectively relieve the contradiction between waterway transport demand and the port status but also be huge potential. Due to hydrological characteristics and landscape characteristics of archipelago waters are complex. Many problems need to be solved to the movement mechanism. So the study of dynamic characteristics, sediment problem of archipelago waters has great economic value, far-reaching scientific significance and widespread application prospect.According to the remote sensing data, field data, the laboratory experiment, mathematical model and theoretical analysis, the hydrodynamic force and sediment condition of archipelago waters are analyzed roundly, and the sea-bed nature, sediment transport form and sediment mechanism of archipelago waters are analyzed in detail. Based on the concept of equilibrium sediment concentration, the siltation index and forecasting mode of muddy seabed evolution is put forward. The prediction formula for siltation of marginal quay dock is established in the muddy seabed. The results show:(1) The tidal currents of the study archipelago waters belong to informal half-day shallow sea tidal current. Tidal current is reversing current. The tidal current velocity is very strong. Under the natural state, because the island is more, shoreline is complex, there are shunt, confluence and circulation obviously; the wave is weak within islands waters due to the action of islands shield; tidal current is the main dynamic force to sediment lift and transport; the tidal current strength determines the change of seabed sediment to a certain extent.(2) In archipelago waters, blocking branches plays an important role to the adjustment of water flow and smooth flow; as change of land boundary (that is, blocking branches), change of flow velocity show a discontinuous process of "part change-change extension-smooth and steady change-change enlargement"; the influence degree on main section tidal volume is increased gradually. After the land border reaches a certain form, tide power change tends to steady, if we continue to change the boundary shape, tide impulses to the adverse direction. (3) In archipelago waters, suspended sediment concentration is high. The seabed evolution is aroused by suspended sediment transport. In archipelago waters, sediment erosion and deposition of muddy seabed are mainly related to local sediment suspension, transport and sedimentation except the background sediment concentration. Suspended sediment concentration distribution in space and time are inhomogeneity prominently. Because, on the one hand, the sediment transport and diffusion of background sediment environment effects sediment concentration distribution, on the other hand, the "channel effect" between islands impacts sediment concentration distribution. In the waters, suspended sediment concentration shows two types--suspension pattern and settlement pattern.(4) Terrain adjustment (scouring or silting) are quickly by influence of land boundary changes within the waters. As the land boundary fixed, water stability and smooth, the terrain changes tend to be relatively balanced. Combination of seabed properties, sediment movement form etc., based on the sediment deposition mechanism and the relationship between actual sediment concentration and equilibrium sediment concentration, the seabed scouring or silting indicator is put forward in the islands sea areas. Further the model of seabed evolution is established. The model is validated based on physical model, mathematical model results. Taking the Yangshan Deep-wate port sea area as an example, the seabed evolution is forecasted using the the muddy seabed evolution model.(5) Improved of the methods to the index n value in the current continuous laws to the alongshore basin flow; in the basin, velocity and basin aspect ratio have good relationship under n value different conditions, which affect flow velocity and depositing change. The sedimentation prediction formula is established to the alongshore basin. The formula contains the n value. Taking the Yangshan Deep-wate port sea area as an example, the silting thickness is calculated to the first and second harbor basin waters using the prediction formula. This result is in good agreement with the measurement data. The error is about10%.更多还原