Experimental study of reservoir flushing through a bottom tunnel initially covered by cohesive sediment  

作　　者：Huan Xu Zhixian Cao 

机构地区：[1]State Key Laboratory of Water Resources Engineering and Management,Wuhan University,Wuhan 430072,China

出　　处：《International Journal of Sediment Research》2024年第3期327-339,共13页国际泥沙研究（英文版）

基　　金：funded by the National Natural Science Foundation of China(Grant No.12072244).

摘　　要：Reservoir sediment flushing,one of the most effective strategies for alleviating reservoir sedimentation,involves discharging sediment-laden flows downstream through bottom tunnels.However,whether flushing can be accomplished if the intake of a bottom tunnel is initially covered by cohesive sediment remains poorly understood.Here,flume experiments were done to investigate cohesive sediment flushing in a reservoir.It is demonstrated that cohesive sediment in a reservoir is harder to flush than non-cohesive sediment.A higher water level in the reservoir,initially smaller cover layer thickness,and lower dry density of the sediment favor the occurrence of sediment flushing.The flushing process of cohesive sediment is significantly affected by seepage.Under the combined action of gravity erosion and water erosion,the scour hole upstream of the dam is characterized by angular and broken edges.The threshold conditions for flushing of non-cohesive and cohesive sediments are evaluated.Empirical formulas applicable to both non-cohesive and cohesive sediment are proposed to estimate the equilibrium scour depth immediately upstream of the bottom tunnel intake.Also,empirical models are proposed for the time variation of sediment position in the bottom tunnel.The current findings are significant for informing the design and operation of reservoirs on rivers carrying fine-grained cohesive sediment in support of reservoir benefits and capacity preservation.

关 键 词：Reservoir sedimentation Sediment flushing Cohesive sediment Scour hole Flume experiment 

分 类 号：TV145[水利工程—水力学及河流动力学]