山区河流浅水条件下漂石对河床响应与泥沙补给影响的试验研究

Experimental Study on Influences of Boulder on Channel Responses and Sediment Supply with Limited Water Depth in Mountain River

受暴雨洪水与滑坡、泥石流灾害的影响,山区河流床沙多为宽级配卵砾石泥沙,甚至出现较多的漂石,从而影响近底水流结构与推移质输移特性。基于野外漂石河流的调查,通过概化水槽试验,探讨了漂石颗粒对河床冲淤的影响;对比分析了不同水沙条件下漂石对推移质输沙率过程的影响;根据床面粗化程度与漂石状态相异的两种类型对比试验,探讨了漂石对不同水沙条件下推移质输沙率的影响程度。研究表明:随着漂石颗粒相对淹没度(h/D,平均水深与漂石有效直径之比)的减少,漂石对其尾部区域水流的混掺越加突出,从而对河床的冲刷能力变大;根据本试验采用的水沙参数,漂石对推移质输沙率的扩大效应为几倍至十几倍。

On the basis of the field investigation of boulder riverbed and series of flume experiments with limited water depth, the influences of boulder on the riverbed deformation and bedload transport rate were analyzed. The results showed that the increase of flow turbulence becomes stronger behind the boulder with the decrease of boulder particle relative submergence degree （h/D, ratio between mean water depth and boulder effective diameter）, the scour ability is enlarged, and the more bed material is transported. According to the bed surface coarse degree and boulder dissimilar state, several of experimental cases were carried out in order to understand the variations of bedload transport rate,the results showed that the influence of boulder on bedload transport rate may be several times to ten times with the premise of the flow-sediment conditioins.