陡坡强输沙河道变坡点水位的试验研究

Experimental study on water level at change point in steep slope river under high sediment concentration

我国山洪灾害频发,人们对其中泥沙致灾的因素越来越重视。采用单因素控制法通过陡比降变化水槽试验,模拟山区河道坡度变化及大量泥沙输送,研究大比降强输沙条件下水位的变化规律。试验结果显示:在携带大量泥沙的情况下,快速落淤泥沙导致局部坡度变缓、流速降低、水位上升;另一方面,泥沙本身的阻力作用导致水位升高。因而导致局部河段急缓流交替水跃发生,显著抬高洪水位,泥沙与水的互馈作用使交界锋面位置处水位显著高于清水水深。研究表明,流量越大、输沙率越大或上游河道比降越大,交界锋面位置处水位越高。伴随着泥沙淤积的逆行发展,异常的水位激增除在边坡交界点附近发生外,还向上游传播,导致漫溢洪水泛滥成灾。

Mountain torrents occur frequently in China,and people pay more and more attention to the factors of sediment disaster.The flume test is carried out to simulate the slope change and large amount of sediment transport in mountainous rivers.Adopting the single factor experiment,we study the variation law of water level caused by large gradient and strong sediment transport.The results show that carrying a large amount of sediment,the rapid deposition of sediment contributes to the slowing down of local slopes,the decrease of flow velocity and the rise of water level.On the other hand,the resistance of sediment itself leads to the rise of water level.Thus the water jumps in some sections happen alternately,and the flood level increases significantly.The interaction between sediment and water results in that the water level at the junction front is far higher than the clear water depth.The research reveals that the higher the discharge,the larger the sediment transport rate or the larger the upstream channel gradient is,and then the higher the water level at the junction front will be.With the retrograde development of sediment deposition,the abnormal surge of water level will not only occur near the slope junction,but also spread upstream,causing the rivers to overflow and flood around.