龙口下游水深对截流难度的影响

葛洲坝和三峡水利枢纽工程,其截流水力学指标在当时国内甚至国际截流史上都是前所未有的,认为这与龙口下游较大的水深有关.试验研究结果显示,龙口下游水深 ht 与龙口上下游落差z有密切关系,ht的增大可使相对落差z/ht明显减小,z/ht的减小有利于抛料在戗堤前沿冲刷面的稳定;同时,龙口下游水深的增加,能有效降低河槽底部流速和垂线平均流速,而抛石重量对流速的变化非常敏感,流速的降低,可使抛石重量大大降低,从而降低截流难度.

Influence of downstream water depth of closure gap on river closure difficulty

The river closure hydraulic indexes of Gezhouba Project and Three Gorges Project were unprecedented in the river closure history in the world, which was considered to have close relation with the downstream water depth of closure gap. Test results demonstrate that the downstream water depth h_t of closure gap has close relation with the drop z of the upstream and downstream water level of the closure gap, the increase of h_t can significantly decrease z/h_t and the decrease of z/h_t is advantageous to the stability of dumped material in the forward of berme dyke, in the meantime, the increase of the downstream water depth of closure gap can effectively decrease the bottom velocity and average velocity of the river flow, the required dumping rock weight has close relation with the flow velocity, the decrease of flow velocity can decrease the required weight of dumped rock weight and the difficulty of river closure.