黄河三角洲海底土波致再悬浮研究

摘要

在现代黄河三角洲采集土样,制备室内水槽试验的底床,施加波浪作用,观测波致悬沙含量的变化规律,分析不同波高、作用时间对单位面积底床再悬浮量的影响,及波浪停止作用后悬浮泥沙的静水沉降规律.研究发现,在水深一定条件下底床再悬浮量呈现随波高增大而增大的特性,两者线性拟合的相关性很好；在一定波高的波浪连续作用下,约5 000～6 000个波周期底床再悬浮过程完成；在波浪作用初始阶段底层悬沙含量与中上层的相差很大,悬沙含量垂线结构呈斜线型,稳定阶段的悬沙浓度垂向结构呈准直线型,底层与表层含沙量比值为0.98～1.25,整个水层含量分布均匀；静水沉降过程中当悬沙含量大于1 g/dm3,悬沙含量(SSC)呈现出随时间指数衰减的规律,悬沙浓度与沉降通量呈线性关系.研究结果对认识黄河水下三角洲泥沙运移规律具有一定的科学意义.%The variation of suspended sediment concentration (SSC) under different waves imposed on seabed soils, collected from the modern Huanghe River Delta,is observed in a laboratory flume experiment. Resuspension flux per unit area of sea-bed in different wave heights and action time has been analyzed, together with the settling pattern of sediment in static water since wave stopped. It is shown that the resuspension flux of sea-bed sediments increases with the wave height under a certain water depth with a good linear fitting relationship;the resuspension of sea-bed sediments experiences about 5 000-6 000 wave cy-rn cles under the continuous action of certain height waves. At the primary stage of wave action, the difference between the low layer concentration and the middle-upper layer concentration is significant, the vertical concentration structure presents a slanted type. After the distribution of SSC in each water layer is stable, the ratio of SSC on the bottom to that on the surface is about 0. 96 - 1. 98 and the SSC uniformly distributes in the whole water. During the hydrostatic sedimentation process,the SSC presents a law of exponential attenuation over time and there is a good negative linear correlation between the SSC and the settlement flux when the SSC is high (greater than 1 g/dm3). The findings can be used for reference in the understanding of wave-induced resuspension process of silty sea-bed sediments in the subaqueous Huanghe River Delta.