Experimental Study of the Impact of Sediments on Stilling Basin of Diversion Dams

This research studies empirical equation for abrasion of stilling basin caused by impact of the sediment. Review of previous papers shows that in previous researches, the mixture effect of erosion and impact are studied without determination of the share of impact in the mixture effect. Also in the researches, the sediment grain size is not as large as debris size in debris flow or experiments are done without tail water depth. Therefore, in this research, the impact of large grain size is studied on concrete stilling basin with tail water. First dimensional analysis is carried out, and subsequently experimental plan is designed. The experiment includes concrete samples with three different cement contents, five depth of tail water, three grain sizes. Abrasion of each grain impact is measured and recorded. Uni-variable and multivariable regression analysis was employed to find possible relation between abrasion ratio and the dimensionless parameter of the experiment. The empirical equations are judged using mean absolute relative errors of the equations. Then a multivariable power equation is proposed for determination of the impacts of abrasion of sediment. The equation shows the abrasion is function of dimensionless energy of sediment grain and the ratio of the grain velocity on stilling basin to the grain velocity on water surface.