渤海海峡潮流底应力与沉积物分布的关系

Relationship between the Tidally-induced Near-bed Shear Stress and the Distribution of Surficial Sediments in the Bohai Strait

用数值模型方法计算了渤海海峡区潮流引起的最大和平均底应力 ,以及相应的活动层厚度的空间分布 ,并根据沉积物参数计算了沉积物临界起动切应力。计算结果的分析表明 :(1)最大潮流底应力和沉积物临界起动切应力的关系与底质分布之间存在着明显的对应 ,最大潮流底应力大于临界起动切应力的地方 ,分布着粗颗粒沉积物 ,若前者小于后者 ,对应的是细颗粒沉积物 ,若两者近于相等 ,则对应着较细颗粒的沉积物 ;(2 )在山东半岛北部近岸和渤海海峡的东北角 ,最大潮流底应力小于或接近于临界起动切应力的量值 ,而对应的沉积物是粉砂和砂 ,这一例外可能是由于残留沉积的出露 ,这一假说需要根据全新世海面上升历史、古水动力环境模拟、渤海海峡沉积环境演化等方面的研究来验证 ;(3)活动层厚度的分布规律与海底沉积物的分布存在着相关性 :即活动层厚度越大 ,对应的海底沉积物越粗 ;活动层厚度越小 。

A 2 D horizontal numerical model is used to simulate maximum and mean tidally induce near bed shear stresses and the corresponding mobile layer thicknesses in the Bohai Strait region. At the same time, the critical near bed shear stress was calculated using the grain size parameters. An analysis of the results shows that: (1) the seabed sediment types are related to the difference between the tidally induced shear stress and the critical shear stress (a larger difference is associated with a coarser bed material); (2) in some places (e.g. the northeastern part of the Strait and the near shore areas of the northern Shandong Peninsula) the tidally induced shear stress is smaller than the critical shear stress, but the seabed sediment is relatively coarse, indicating that the sediment may represent relict materials (this hypothesis should be tested by the results from future investigations into the Holocene sea level changes, paleo hydrodynamic conditions and the evolution of the sedimentary environment); and (3) a good correlation between the mobile layer thickness and the sediment type exists, i.e., a large mobile layer thickness is associated with relatively coarse sediments, and a small thickness is associated with fine grained sediments.