泥沙研究

为探究河床中小于2 mm沙含量不同对冲刷过程中砾石和卵石输沙影响，采用0.5 mm沙、5 mm砾石和20 mm卵石配比3种典型级配铺沙，进行4种阶梯流量清水冲刷试验。结果表明，一定水流强度下，初始流量对不同沙含沙的河床的冲刷影响不同，河床最大冲深与初始流量大小不同的流量过程存在两种截然不同的相关关系。一定沙质含量可以促进砾卵石冲刷输移，但过量含量可能通过不连续级配中粗细颗粒之间重力差异的影响，增大卵石的起动切应力来抑制其冲刷输移。揭示小于2 mm沙对砾卵石泥沙输移的影响，有助于推进非均匀沙起动理论的发展。

In order to explore the influence of the content of sand(smaller than 2 mm in diameter) on the erosion processes of riverbed with gravel and pebbles, clear-water erosion tests have been conducted in an experimental flume under four different flow processes and three mixtures of bed material with different components of fine sand of 0.5 mm, gravel of 5 mm, and pebbles of 20 mm in diameter. The results indicate that, under a certain flow intensity, the effect of the initial flow rate on the scouring of different sand laden riverbed is different, there are two distinct correlations between the maximum scour depth of the riverbed and the initial flow rate under different flow processes. A certain content of sand can promote the erosion and transport of gravel and pebbles. However, an excessive sand content may increase the critical shear stress for sediment motion and inhibit their scouring and transport consequently due to the gravity difference between coarser and finer particles in the discontinuous gradation. The results will contribute to the development of the incipient motion theory.