淤泥质浅滩泥沙临界起动切应力剖面确定

Critical stress profile for incipient sediment motion on muddy shoals

为了确定淤泥质浅滩泥沙的临界起动切应力垂线剖面,采用音叉密度计在淤泥质连云港徐圩浅滩进行了定点密度垂线分布测量,并针对该海域的泥沙利用长水槽和环形槽开展了泥沙起动室内试验。淤泥密度现场结果表明,浅滩泥沙密度与深度满足对数型关系;室内试验得出密度1 050～1 400 kg/m3的泥沙临界起动切应力值为0.1～1.0 Pa,泥沙临界切应力与密度呈指数关系;进而确定了临界起动切应力与深度的关系即临界起动切应力剖面,该剖面关系式可供数学模型模拟淤泥质浅滩的泥沙起动过程参考。

The vertical profile of critical shear stress is determined using both experimental data and in-situ measurements.A tuning fork densimeter is employed to measure the vertical density distributions of mud on the Lianyungang muddy shoals in Jiangsu Province of China.Laboratorial experiments are conducted to study the incipient motion of sediment collected from the sea area where the vertical density of mud is measured.Both annular flume and long straight flume are used in the experiments under gradually increasing flow velocity.The result shows that there is a logarithmic relationship between the mud density and the water depth as revealed by the field survey.Laboratorial experiments indicate that the critical shear stress needed to initiate sediment movement ranges from 0.1 to 1.0 Pa for the density of 1 050~1 400kg/m3 mud,and the critical shear stress increases exponentially with the densification of the mud layer.As the result,a formula is established to describe the relationship between the critical shear stress and the water depth.The formula could be useful to simulate the incipient motion of sediment particles in a muddy environment.