海岸沙坝剖面和滩肩剖面特征研究

Experiment study on evolution and geometrical characteristics of sandbar profile and berm profile

通过物理模型实验研究了海岸沙坝剖面和滩肩剖面的形成和演化过程,给出了稳定的沙坝剖面和滩肩剖面的几何特征。实验中考虑了两种初始坡度(1∶20和1∶10)和不同波高的规则波和不规则波,讨论了不同初始坡度海岸上破碎波空间分布特征。结果表明,沙坝产生后存在向岸和离岸两种运动形态,但最终将停留在稳定位置。稳定的沙坝剖面对应不同初始坡度和波浪存在不同的大沙坝和小沙坝分布。沙坝剖面由长时间小波高波浪序列作用后可转化为稳定滩肩剖面,该剖面不依赖于波浪和初始坡度。实验也给出了平衡剖面与理论曲线的对比以及剖面上泥沙粒径的分布。

A series of physical model experiments were conducted to study the formation and evolution of sandbar and berm profiles.The characteristics of these profiles were observed.Two initial beach slopes （1∶20 and 1∶10） and regular and irregular waves with different heights were adopted.The results showed that the sandbar can move onshore or offshore,depending on wave condition （for regular wave cases）or on initial beach slope （for irregular wave cases）.But it has a final steady position.The transform of sandbar profile to berm profile was realized with action of a series of waves with gradually decreased wave height.The distribution and formation mechanism of multiple bars formed in the experiment are discussed by relating them to initial beach slope,wave type and spatial distribution of breaking wave.The geometrical features of the sandbar profile are presented.The distribution of the sand grain along beach cross section was measured.The measured equilibrium berm profile agrees with the theoreti-cal result.