伶仃洋河口泥沙絮凝特征及影响因素研究

发布时间：2018-08-10 07:23

【摘要】：泥沙絮凝对河口细颗粒泥沙运动过程起着极其重要的作用。本文通过LISST-100激光粒度仪等仪器实测伶仃洋河口2013年洪季悬浮泥沙絮凝体现场粒径及水动力、泥沙条件,结合实验室悬沙粒径分析,研究大小潮期间伶仃洋河口泥沙絮凝特征,探讨紊动剪切强度、含沙量、盐度分层及波浪等因素对伶仃洋河口泥沙絮凝的影响。结果表明:伶仃洋河口水体中现场粒径平均值为148.53μm,大于实验室悬沙分散粒径36.74μm,河口絮凝现象明显;沉速与有效密度、粒径呈正相关,絮团平均有效密度为153.49kg/m3,平均沉速达1.13mm/s;小潮时絮团平均粒径大于大潮,垂向上表底层絮团粒径小、中层大,中底层絮团沉速大于表层。伶仃洋河口水动力、泥沙条件是影响其泥沙絮凝的重要因素,低剪切强度(小于5s-1)、低含沙量(小于50mg/L)及高体积浓度有利于细颗粒泥沙之间的相互碰撞,促进絮凝作用;当剪切强度与颗粒间碰撞强度高于絮团所能承受的强度时,絮团易破碎分解成小絮团或更细的泥沙颗粒;伶仃洋河口盐度层化引起的泥沙捕获现象增大中层泥沙体积浓度,有利于中层絮凝体的发育;观测期相对较大的波浪增强水体紊动,增大了水体细颗粒泥沙的碰撞几率,表层絮团粒径随波高峰值的出现而增大。
[Abstract]:Sediment flocculation plays an extremely important role in the process of fine sediment movement in estuaries. In this paper, the particle size and hydrodynamic properties of suspended sediment in the Lingdingyang Estuary during the flood season of 2013 were measured by LISST-100 laser particle size analyzer, and combined with the analysis of suspended sediment particle size in laboratory, the characteristics of sediment flocculation in Lingdingyang Estuary during the period of big and small tide were studied. The effects of turbulent shear strength, sediment content, salinity stratification and wave on sediment flocculation in Lingdingyang Estuary are discussed. The results show that the average particle size in Lingdingyang Estuary is 148.53 渭 m, which is larger than that in laboratory suspended sediment. The flocculation phenomenon in the estuary is obvious, and the sedimentation velocity is positively correlated with the effective density and particle size. The average effective density of flocs is 153.49 kg / m ~ (3), and the average settling velocity is 1.13 mm / s. The average particle size of the floc is larger than that of the spring tide at low tide, and the diameter of the bottom floc in vertical surface is small, the middle layer is large, and the settling velocity of the middle and bottom floc is larger than that of the surface layer. Low shear strength (less than 5s-1), low sediment content (less than 50mg/L) and high concentration are favorable to the collision of fine sediment and promote flocculation. When the shear strength and the impact strength of the particles are higher than the strength of the flocs, the flocs are easily broken down into smaller flocs or finer sediment particles, and the sediment capture caused by salinity stratification in the Lingdingyang Estuary increases the volume concentration of the middle sediment. The relatively large waves in the observation period enhance the turbulence and increase the collision probability of fine sediment, and the particle size of surface floc increases with the peak of wave height.
【作者单位】：中山大学海洋科学学院河口海岸研究所;
【基金】：国家自然科学基金项目(41106015,41476073) 科技部科技基础性工作专项重点项目“中国典型河口动力沉积地貌本底数据调查”(2013FY112000)
【分类号】：TV148

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