减速流条件下卵砾石输移规律初步研究

Study on gravel transport laws in decelerating flow

实测资料显示,长江三峡水库变动回水区末端段床沙质以卵砾石夹沙为主,消落期出现的碍航特性主要由卵砾石推移质运动造成,对三峡库尾段航运造成很大影响,有必要对库尾水流条件下的卵石输移规律进行研究。库尾水流通常是非均匀减速流,目前对非均匀流的研究多把局部近似为均匀流。通过库尾非均匀流减速流的卵砾石输移水槽试验,观测减速流卵砾石运动输移过程,并确定非均匀系数对卵砾石输沙强度的影响,再与已有推移质公式对比,根据已有相近的输沙强度公式结构形式,结合水槽试验结果,拟合得出含有非均匀系数的适合于减速流态下的卵砾石输移的输沙强度公式,并通过计算值与实测值的对比验证公式的合理性。

Based on field data of Three Gorges Reservoir fluctuating backwater reach,the bed material mainly consists of gravel and sand. Gravel transport may cause navigation obstruction characteristics in the period of low level. These characteristics also lead to a great impact on navigation in the tail reach of Three Gorges Reservoir. One of main tasks of Three Gorges Project is navigation,then it is necessary to study the gravel transport laws in the tail reservoir flow. Mostly the tail reservoir flow is decelerating flow,which is one type of non-uniform flow. However,the majority of existing researches about non-uniform flow are based on local uniform flow approximation. As a result,this study conducted flume experiments of gravel movement in decelerating flow,describing the gravel transport process and regarding the non-uniform coefficient as one of the gravel transport intensity factors. By comparing experimental data with existing bedload formulas which is in the form of a typical transport intensity,this study derived the gravel transport intensity formula under decelerating flow through interpolating. This formula contains non-uniformity coefficient. finally,the formula was verified to be proper by the ratio of computed data to measured data.