河床阻力是河流动力学的基本问题之一,与河流的泄流能力及挟沙能力息息相关。利用2014—2016年长江下游九江至河口段河床的多波束、ADCP及底质沉积物的同步采集数据,通过计算沙粒阻力和沙波阻力,分析不同河段河床阻力的分布特征,探讨河床阻力与宽深比、粒度及流速3个因素之间的相关关系,并对比三峡蓄水前后主要河段河床阻力及其与影响因素之间相关性的变化特征。研究结果表明:三峡蓄水前后,总体上,长江九江至吴淞口河段最大河床沙粒阻力和平均沙粒阻力分别减小57％和63％。长江下游河道河床阻力在蓄水前后均以沙粒阻力为主,沙波阻力在河床阻力中占比不足1％且随着三峡工程的运用有减小的趋势。三峡蓄水前,长江下游河道河床阻力与3个影响因素相关性从大到小依次为粒度、流速和宽深比,相应的平均决定系数依次为0.48,0.30,0.25;而三峡蓄水后,长江下游河道河床阻力与3个影响因素相关性从大到小依次为流速、宽深比和粒度,相应的平均决定系数依次为0.71,0.41,0.30,但各河段河床阻力在不同时期主要影响因素又有所区别。研究结果可为长江下游航道整治、航运安全和防洪提供参考依据。
Abstract
As a fundamental issue of river dynamics, the resistance of river bed is closely related to the discharge capacity and sediment carrying capacity of river. The distribution of river bed resistance in different reaches was analyzed by calculating the sand particle resistance and sand wave resistance based on data acquired synchronously using multi-beam measurement system, ADCP, and particle size data from Jiujiang to Hekou in 2014-2016. The relations of bed resistance against ratio of width to depth, particle size, and flow velocity were examined. Furthermore, the bed resistance and influencing factors for main segments before and after the impoundment of Three Gorges Project (TGP) were also compared. Results concluded that: around the impoundment of the TGP, the maximum and average sand particle resistance from Jiujiang to Wusongkou decreased by 57% and 63%, respectively. Meanwhile, sand particle resistance was the dominant resistance, while sand wave resistance accounted for less than 1% and even tended to decline along with the operation of TGP. Before the impoundment of TGP, bed resistance in the lower reach of the Yangtze River was the most significantly correlated with particle size, followed by velocity and width to depth ratio; and the corresponding average correlation coefficients was 0.48, 0.30, and 0.25, respectively. After the impoundment of TGP, the correlation ranked from flow velocity, width to depth ratio to particle size in sequence; and the corresponding average correlation coefficients was 0.71, 0.41, and 0.30, respectively. The main influential factors of bed resistance in different reaches varied with time period.
关键词
长江下游 /
河床阻力 /
分布特征 /
宽深比 /
粒度 /
流速 /
三峡蓄水
Key words
the lower reach of Yangtze River /
riverbed resistance /
distribution characteristics /
ratio of width to depth /
particle size /
flow velocity /
impoundment of Three Gorges Project
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基金
国家自然科学基金项目(41476075);
国家自然科学基金中荷英项目(51761135023);
中国地质调查局项目(DD20160246)
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