侵蚀沙质海岸演变过程中的岸滩泥沙通量研究-以辽东湾东岸月亮湾沙滩为例

With Yueliang Bay eroding sand beach as the object of our research,in Liaodong Gulf Eastern coast,the self-designed sediment traps are deployed offshore in surf zone.The vertical distribution charateristic of offshore and longshore sediment flux in surf zone is measured,and also the regulations that the volume of sediment flux varies at different location of the seabed sandbar are researched,together with the sediment grain characters.Wave elements,such as wave direction,wave height,wave period,are observed.The facters of current near seabed in different location offshore is also measured. Base on the data,the numerical model is estanlished to calculate sand transport rate.It is validated by the measurement results of sediment traps in surf zone.Used the modified model,applicable to calcuate sand transport flux in erosion sand coast,the sediment flux is numerated finally.Based on the survey data of wave and current during spring tide and neap tide in different seasons,the gross and net sediment transport loadings in different location offshore can be calcaculated during spective tidal cycle.Some improved sediment traps are designed and used in the project.The modified equipments can effectively research the offshore and longshore sediment flux at the same time,and it could not be done with the existing sediment traps. The data gained in the project enriches the current fingdings of sediment grain characteristic and transport flux in erosion sand coast. The studyings contribute to promote the work,namely,sediment transport flux,control mechanism of coast erosion,and coast evolvement process to develop further.

以辽东湾东岸月亮湾侵蚀沙滩为研究对象，尝试运用自行设计、改进的泥沙捕获器观测碎波带横、纵向泥沙粒度、通量的垂向分布特征，结合同步观测的岸滩地形变化特征，探寻岸滩泥沙横、纵向通量变化与底床沙坝形态演变的关系。利用观测的波要素、向海离岸沿线的近底床海流，结合实测的泥沙通量，修正并建立适用于侵蚀砂质海岸的泥沙输运通量的计算模型，计算不同季节的完整潮周期（包括大、小潮）的岸滩断面沿程的泥沙输运总量和净量。项目改进了现有观测手段，弥补了其在碎波带无法同步观测泥沙横向（离-向岸）、纵向（进-出）运移的缺陷，丰富了侵蚀海岸演变过程中的泥沙粒度、通量的观测数据，有助于推动泥沙输运通量、海岸侵蚀控制机理、岸滩演变过程的科学研究向更深、更广的方向发展。

课题组研制了笼式泥沙捕获器，并在辽东湾白沙湾海岸进行了实测，取得了较好的观测结果。观测结果表明，近底床泥沙输运大量发生于距离45cm的高度范围内，而距离底床100cm的泥沙运移量极少。另外，沉积物平均粒径、物质组成等粒度参数在不同的泥沙运移方向上没有表现出明显的规律。岸滩地形测量结果指出2013年冬季至2016年夏季白沙湾南部岸滩地形整体呈淤积状态，2013年冬季至2014年冬季白沙湾中部潮间带上部呈侵蚀状态，2015年夏季至2016年夏季白沙湾中部呈淤积状态，尤其是潮间沙坝向海一翼淤积明显。三角架水文泥沙观测系统的观测结果指出白沙湾水下海底底床的变化受强浪作用控制，而海流作用对沉积物再悬浮影响较小，强浪作用下，白沙湾的水下沙坝出现向岸迁移的趋势，坝-槽向岸迁移并加高或加深，对低潮带带来的侵蚀破坏尤其明显。基于现场测得波浪和流速要素，采用Engelund& Hansen的波流共同作用全沙输沙率公式计算得出的研究区域泥沙输运率单宽输沙率最高1.07×10-3m3/s。岸滩水文泥沙观测系统指出底边界层内的悬沙浓度基本与距离底床高度呈负相关关系，距离底床越高，悬沙浓度越低。悬沙浓度（距离底床0.35m）最高达380mg/l，近底床近0.8m范围内的悬沙浓度普遍小于20mg/l。同一潮周期内，在涨潮至落潮期间，近底床边界层内的悬沙浓度呈现低-高-低变化趋势。悬沙浓度峰值区与高潮位的平潮期相关度较高，而在低潮位的时期悬沙浓度相对较低。