沙坝海岸输沙特征试验研究

Experiment study on the characteristics of sandbar beach sediment transport rates

为了研究沙坝海岸波浪系列中波高变化对悬移质输沙率、推移质输沙率和净输沙率的影响,进行了不同坡度海岸上规则波和不同调制系数波群作用下沙坝泥沙运动的试验。通过地形仪测量的不同时刻海岸剖面得到了净输沙率,通过浊度仪测量了悬移质在沙坝坝峰和沙坝前后位置处的垂向分布。根据试验结果讨论了波高变化对沙坝海岸泥沙运动的影响,包括:沙坝运动的瞬时速度大小和方向与沙坝峰处瞬时净输沙率大小和方向的关系;不同调制系数所导致的泥沙输沙率和沙坝运动瞬时速度的大小和方向;影响悬移质浓度水深平均值的各种因素。

A series of physical model experiments were conducted under the conditions of regular waves and wave groups with different modulation coefficients,to study the importance of waves with different modulation coefficients in cross-shore sediment transport in the surf zone of a sandbar beach. The laboratory data are presented,including the spatial variations of net sediment transport rates measured by a topography meter,the vertical distributions of suspended sediment concentrations measured by concentration meters,the along sandbar distributions of suspended sediment transport rates. Those experimental results show that the value and direction of the sandbar movement speed relate to the instantaneous value and direction of the net transport rate.Depth average value of suspended sediment concentration depends on the relative positions to the sandbar,water depth at sandbar crest,modulation coefficients and coastal slopes. The value of suspended sediment transport rate in front of the sandbar is larger than that in back of the sandbar. The suspended sediment transport rate dominates the net sediment transport rate.