Abstract
In this paper, we examined hydraulic performances of circular crests for easier consrtuction of a dam crest part. And we led the hydraulic design method of circular crests from the results of experiments. The results are summarized in the following. i) Weir coefficient of circular crests is given equation (1). The error of this equation is between ±3% on the condition that H/Lc>0.5 (H: head, Lc: Crest width). ii) Overflow water profile on circular crests with no piers is estimated accurately by equation (2). And highest water profile on circular crests with piers can be estimated by equation (6). iii) Negative pressure occurs on the circular parts of circular crests when head is high. But, excessive negative pressure can be prevented provided that L/H≥0.28 on the upstream circular part, R2/H≥(1.0-1.7) on the downstream circular part (H: head, L: Crest length of upstream circular part and flat top, : Radii of downstream circular part). On these condition, pressure on the downstream circular part is higher than -3.0mH2O when head is lower than about 10m.
