高拱坝表孔宽尾墩体型优化试验研究

Optimal experimental study on flaring piers of surface spillways in high arch dam

高拱坝表孔溢流坝面短,作用水头低,堰前行进水流具有向心倾向。宽尾墩消能工应用在高拱坝泄洪表孔必须与此特点相适应。本文对宽尾墩应用在高拱坝坝顶泄洪表孔的体型布置进行了试验研究。结果表明,宽尾墩应用在高拱坝表孔时,出口角度不宜采用挑角,而应采用俯角:采用较大的宽尾墩墩尾折角有利于水流的纵向扩散和减小水垫塘底板冲击动压;同时为避免拱坝曲率造成的水流径向集中现象,两边表孔宽尾墩应采用非对称体型设计。优化后表孔水流能够在竖向及纵向充分扩散,空中呈窄而高且长的流态,在水垫塘中横向分区入水明显,不仅使水垫塘底板冲击动压减小和冲击点向下游偏移,而且为高拱坝表深孔水舌相互穿插无碰撞消能,减轻泄洪雾化创造了条件,对狭窄河谷中的高坝工程具有重要的工程应用价值。

High arch dam has the characteristics of short spillway, low-head and radial flow, so the flaring piers applied to the surface spillway in high arch dam must have these characteristics. The optimal layout of flaring piers on spillway in high arch dam is studied experimentally in this paper. The results show that in order to make the jets spread vertically and stretch in longitudinal direction, the outlet angle of spillways with flaring piers in high arch dam can＇t be lift angle but plunge angle. At the same time, in order to solve the problem of water concentration caused by radius of curvature in high arch dam, the flaring piers on both sides of spillways must be asymmetric layout. With the optimal layout of flaring piers, the flared vertical spreading and longitudinal stretching jets are gotten, the impact pressure on bottom of plunge pool is also reduced and the point of maximum averaged impact pressure is also offset to downstream, which is helpful to keep the safety of high arch dam. The new approach of energy dissipation in high arch dam is especially adaptive applied to the projects with high side slope in narrow valley.