窄河谷高拱坝收缩式表孔体型研究

无碰撞泄洪消能方式是狭窄河谷地区高拱坝工程优先选择的坝身泄洪消能方式,其核心思路是利用宽尾墩形成横向收缩、纵向拉伸的表孔水舌,以适应狭窄河谷地形条件,同时满足表孔水舌从深孔水舌间隙穿插,表、深孔水舌空中不发生碰撞,从而减轻表、深孔联合泄洪时泄洪雾化的目的。然而,高拱坝表孔多为开敞式溢流堰结构,流道短、作用水头小、出流流速低,通常难以形成流态稳定、纵向拉伸效果好的表孔水舌。为此,以锦屏一级特高拱坝工程为依托,采用了理论分析与水力学模型试验相结合的分析方法,先后开展了5种收缩式表孔体型的探索研究,成果表明,采用宽尾墩辅以出口透空体型能够有效地提高表孔水舌的空中稳定性、改善表孔水舌纵向拉伸效果、增加水舌纵向入水长度,从而减小水垫塘底板的最大冲击压力。

Study on shape of contracted surface outlet on high arch dam in narrow valley

The non-collision flood discharge and energy dissipation is a preferred energy dissipation mode for the high arch dam innarrow valley， of which the core concept is to form the nappe from surface outlet with transverse contraction and longitudinaldraw-out by flaring pier， so as to adapt to the narrow valley terrain and meet the requirement of that the nappes from surface out-lets can jet out through the spaces in-between the nappes from deep outlets and no collisions occur between both the nappes in theair， thus get the target of flood discharge atomization during the joint flood discharge from both the surface outlet and the deepoutlet. However， as most of the surface outlets of high arch dam are the open-overflow weir structures with short flow passage， small effective head and low flow velocity， it is difficult to form a surface outlet nappe with stable flow pattern and better longitu-dinal draw-out effect. Therefore， on the basis of the ultra-high arch dam of Jinping I Project， an exploratory study is made on fivekinds of contracted surface outlets one after another with the analysis method combining the relevant theoretical analysis with thehydraulic model experiment concerned， from which the result shows that adopting flaring pier supplemented with porous shape ofoutlet can effectively enhance the in-air stability， improve the longitudinal draw-out effect and increase the length of flowing intowater of the nappe from surface outlet， thus reduce the maximum impacting pressure on the bottom slab of plunge pool.