IMPROVEMENT OF SEDIMENT-CONTROL FUNCTION OF SLIT DAM

为了提高垂直缝口拦沙坝的拦沙效率，本文首先通过实验研究了垂直缝口两侧产生的对水流和泥沙运动产生不利影响的孤立涡的特性。研究发现，孤立涡的存在减小了溢流的有效面积，同时也使泥沙向上游方向运动，考虑了几种减小孤立涡的不利影响的附加结构形式，并在狭缝上游口处增加一对或两对叶片式结构，提出了一种改进的基本思路--开孔法，并通过改变结构的数量和几何尺寸，对该方法的有效性进行了实验验证。研究结果表明，在中小洪水条件下，这些结构对沟道发育有明显的促进作用，从而提高了大洪水对多沙径流的拦蓄能力。研究叶片式结构对水流和泥沙的影响，以了解上述结果-从液压角度进行上述试验。

The purpose of this reseach is to improve the efficiency of sediment retention dams with vertical slit-openings.First, characteristics of an couple of isolated vortexes, being generated on the both sides of a slit-opening and giving negative effects to the behavior of water and sediment spilling through the slit-opening, were clarified experimentally. The isolated vortexes were found to reduce the efficient area of spilling flow as well as to reversely transport the sediment toward upstream.Some types of additional structure for reducing the negative effects of the isolated vortexes were considered and addition of one or two couples of vane-type structures to the upstream mouth of the slit-opening was selected as a basic idea of improvement.The efficiency of this measure is tested experimntally by changing the number and geometric dimensions of the structures. As the result, it was proved that those stuctures significantluy promote the development of gully streams in medium and minor flood events and thus increase the retention capacity for heavy sediment run-off by big floods.Finally, based on measurements of three dimensional flow velocity, the influence of the vane-type structures to flow and sediment is investigated in order to understand the results of the above-mentioned tests from hydraulic points of view.