黄河三角洲海底土波致再悬浮研究

A study on wave-induced sediment resuspension on the sea-bed in the Huanghe River Delta in China

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1g/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 sea- bed 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, to-gether with the settling pattern of sediment in static water since wave stopped. It is shown that the resus-pension 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-cles under the continuous action of certain height waves. At the primary stage of wave action, the differ- ence between the low layer concentration and the middle-upper layer concentration is significant, the verti-cal concentration structure presents a slanted type. After the distribution of SSC in each water layer is sta-ble,the ratio of SSC on the bottom to that on the surface is about 0.96-1.98 and the SSC uniformly dis-tributes in the whole water. During the hydrostatic sedimentation process, the SSC presents a law of expo-nential attenuation over time and there is a good negative linear correlation between the SSC and the settle-ment flux when the SSC is high （greater than 1 g/dm^3）. The findings can be used for reference in the un derstanding of wave-induced resuspension process of silty sea-bed sediments in the subaqueous Huanghe River Delta.