摘要
三峡工程运行后,长江中游荆江河段含沙量大幅度降低,次饱和水流冲刷河床使含沙量在沿程逐渐恢复,但其恢复特点由于沿程床沙组成差异而有所不同。本文基于Markov随机过程及泥沙起动理论,推导非均匀悬沙的泥沙落距表达式;结合悬移质扩散理论,修正非均匀悬沙恢复饱和系数公式。在此基础上,基于荆江河段实测输沙过程,提出考虑床沙组成影响的分组悬沙恢复饱和系数计算方法;该方法主要与泥沙粒径、悬浮指标、床沙组成及止滚概率、止悬概率等因素有关,无需考虑非饱和调整系数的影响。计算结果表明:①不考虑床沙组成时,沙市、监利站恢复饱和系数计算值均在区间0.12~0.27内变化,而考虑床沙组成时分别为0.0003~0.1718和0.0035~0.1579。②不考虑床沙组成时,分组悬沙恢复饱和系数计算值细沙>中沙>粗沙;考虑床沙组成时细沙<中沙<粗沙;除落水期外,沙市站粗沙的恢复速度均大于监利站。③沙市、监利站恢复饱和系数在各计算时段的变化过程对悬沙分组具有敏感性,其中洪水期恢复饱和系数大于枯水期、涨水期和落水期。采用河床变形方程反算分组悬沙恢复饱和系数,并与本文计算结果进行对比;通过比较分析,本文公式能够用于描述荆江河段分组悬沙恢复特性,可为三峡工程下游非均匀悬沙沿程恢复过程研究提供参考。
Sediment discharge in the Jingjiang reach has sharply reduced since the Three Gorges Project operation,and the channel has been scoured by the clear water in order to recover the sediment transport capacity.However,the recovery rate of nonuniform suspended sediment was different with the different bed material compositions along the Middle Yangtze River.Therefore,the equation of settling distance of nonuniform sediment is derived,based on the theories of Markov stochastic process and sediment motion.Then,according to the definition of saturation recovery coefficient(α)based on the diffusion theory of suspended sediment,the formula of grouped saturation recovery coefficient(αi)is modified using the equation of settling distance;However,it ignores the effect of bed material composition(BMC)on suspended sediment recovery.For the actual process of sediment transport in the Jingjiang reach,a formula ofαi is then proposed with the effect of the BMC being considered.These results show that:①The value range ofαi in this study was 0.12-0.27 at Shashi and Jianli when the influence of the BMC was not taken into account,but it became to the range of 0.0003-0.1718 and 0.0035-0.1579 respectively when considering the BMC effect;②Amongαi of different sediment groups,the relationship ofαi f for fine sediment>αi m for medium sediment>αi c for coarse sediment existed when the BMC effect was not considered,but the relationship ofαi f<αi m<αi c existed when considering the influence of BMC;and the recovery rate of suspended sediment at Shashi was higher than that at Jianli except for the recession period;③The variations ofαi at Shashi and Jianli were sensitive to different groups during different periods,in whichαi during the flood period was higher than the value during other periods.Through comparation and analysis,the proposed formula in this study can predict the value ofαi for the Middle Yangtze River well,and it also providing a basis for further research on the recovery mechanism of suspended sediment in th
作者
李林林
夏军强
邓珊珊
周美蓉
李志威
LI Linlin;XIA Junqiang;DENG Shanshan;ZHOU Meirong;LI Zhiwei(State Key Laboratory of Water Resources and Hydropower Engineering Science,Wuhan University,Wuhan 430072,China)
出处
《水科学进展》
EI
CAS
CSCD
北大核心
2021年第5期727-737,共11页
Advances in Water Science
基金
国家自然科学基金资助项目(51725902
U2040215)。
关键词
悬移质
床沙组成
恢复饱和系数
随机过程
长江中游
suspended load
bed material composition
saturation recovery coefficient
stochastic process
the Middle Yangtze River
