金塘水道的悬沙输运和再悬浮作用特征

Processes of suspended sediment transport and resuspension in Jintang Channel

根据1986年秋季和1987年春季金塘水道内十个站点的大、中、小潮的流速和悬沙浓度的同步观测资料，利用悬沙质量守恒原理，分析了金塘水道的悬沙输运和再悬浮作用特征。水道与外海的悬沙交换、水道内悬沙与底质的泥沙交换分别使水道内的悬沙质量平均每小时发生2％．10％和7％～14％的变化，前者小于后者。水道与外海进行悬沙交换时，水道向外海输出悬沙，大潮周日输出的悬沙质量比小潮大2个数量级。在悬沙与底质的泥沙交换过程中，大潮和中潮以再悬浮作用为主，小潮以沉降作用为主，在一个大小潮周期中，再悬浮作用强于沉降作用，水道底床发生侵蚀。再悬浮通量与流速、（τ—τCГ）／τCГ具有一定的正线性关系（τ为底部切应力，τCГ为临界再悬浮切应力）。再悬浮系数处于10—kg·m^-2s^-1量级，与（τ—τCГ）／τCГ不具有明显关系，底质沉积特征是影响再悬浮作用和再悬浮系数的重要因素。

Tidal cycle measurements of suspended sediment concentrations and tidal current velocities at 10 stations in the Jintang Channel were carried out simultaneously on spring, intermediate and neap tides, in autumn 1986 and spring 1987, respectively. Based upon the mass conservation of suspended sediment in the channel, the characteristics of suspended sediment transport and resuspension were analyzed. The results indicate that there were 7 % - 14% variations, on hourly time scales, in the suspended sediment quantity and concentration in the channel; such variations were controlled mainly by the sediment exchange at the sediment - water interface, with the exchange between the channel and adjacent sea areas only playing a minor role. A large quantity of suspended sediment was exported from the channel during the survey period; the exchange of suspended sediment between the channel and adjacent sea areas during the spring tide was 2 orders larger than during the neap tide. Resuspension was intensive, with the seabed being eroded on spring and intermediate tides, but accretion was prevailed on neaps. The resuspension flux was related linearly to the current velocity of bottom layer or normalized excess shear stress, whilst the resuspension coefficient did not show well-defined relationship with the normalized excess shear stress. The property of seabed sediment was the main factor that influenced the characteristics of resuspension flux and the related coefficient.