破碎波作用下床面形态研究及泥沙受力分析

Analysis of bed form and sediment force under action of breaking waves

破碎带水体强烈紊动对床面形态影响甚大,基于波浪水槽试验对沙质斜坡上破碎带床面形态以及泥沙受力进行研究。分析床面形态发现,同一断面处沙纹沙坝的形态与波浪形态基本一致,波高和周期决定沙纹沙坝的尺寸,波高越大,沙纹沙坝越高;周期越长,沙纹沙坝越长。通过对波浪破碎区的近底流速及砂床内孔隙水压力进行测量,将计算得到的表层上举力与超静孔隙水压力进行对比分析,发现其上举力与床面超静孔隙水压力大小相同。同时观察波浪破碎带床面高程,进一步研究上举力与超静孔隙水压力与床面高程的关系,发现表层上举力随着床面高程增加而变大,随着床面高程的降低而减小,而超静孔隙水压力与床面高程之间的关系则相反。

Strong turbulent flow has a great influence on the bed form in the wave broken zone. Based on the wave flume experiments, studies of the bed form and forces acting on the sediment in the wave broken sections have been carried out. According to the analysis of the bed form, it is found that the form of the sand ripple, sandbar and wave in the same place is basically consistent ; the wave height and wave period influence the size of the sand ripple and the sandbar; the higher the wave height, the higher the sand ripple and sandbar; the larger the wave period, the longer the sand ripple and sandbar, and vice versa. The near bottom velocity and pore water pressure have been measured along the wave broken sections. Comparing and analyzing the surface uplift force and excess pore water pressure, it is concluded that the values of uplift force and the bed excess pore water pressure amplitude are the same. At the same time, the bed elevation in the broken zone is observed and further studies are made of the relationship among surface uplift force, excess pore water pressure and bed elevation. The analysis results show that the surface uplift force has increased with the increase in the bed elevation and decreased with the decrease in the bed elevation. However, the relationship between the excess pore water pressure and the bed elevation is quite opposite.