黄河上游高含沙水流交汇区河床形态及冲淤变化规律
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摘要
黄河上游交汇区为典型的高含沙水流交汇区,支流高含沙洪水往往引起剧烈的河床形态调整及冲淤变化。利用室内模型实验、野外观测资料,研究了支流高含沙洪水入汇干流后,交汇区变化过程及冲淤计算方法。研究表明,交汇区河床形态包括壅水区淤积沙坝、分离区沙洲、输水输沙主槽及分离区以下河段的沙洲等基本元素。进入交汇口上游壅水区的泥沙全部落淤,淤积量随高含沙洪水沙量的增加呈线性线增加;提出的交汇口以下河段的泥沙淤积模式,揭示了泥沙淤积的主要影响因素为支流高含沙洪水沙量、汇流比、恢复饱和系数等,支流高含沙洪水沙量的作用更为明显,该模式可以定量描述交汇口以下河段的泥沙淤积。支流高含沙洪水形成的淤积沙洲的冲刷,取决于干流洪水流量及持续时间。黄河上游交汇区的淤积沙洲,较优的冲刷流量为2000 m3/s左右,冲刷历时为10天左右。
At the river confluences of the upper Yellow River, flows carrying hyperconcentrated sediment merge together, and in flood season the merging usually causes severe deposition and dramatic change in bed morphology. In this study, we investigate the morphological process at hyperconcentrated confluences through laboratory experiment, field observation, and theoretical analysis, and develop a new method for predicting sediment deposition at the confluences. Results show that four basic elements of the morphological pattern can be identified: sandbars in the backwater zone, sandbars in the flow separation zone, a mainstream channel for water and sediment transport, and bars downstream of the separation zone. Because of turbulent diffusion, sediment particles carried by the hyperconcentrated flows enter the backwater zone upstream of the junction, and then form sandbar deposition with a volume proportional to the sediment load. We construct a model for calculation of the sediment deposition at river confluences and reveal its main factors: sediment load and discharge ratio of the incoming flows, water discharge of the main stem, and adaption coefficient of the incoming suspended loads. This model is applicable to prediction of the deposition at asymmetrical river confluences. Scour on the sandbars caused by heperconcentrated tributary flows depends on the discharge and duration of main stem floods. For the confluences on the upper Yellow River, the most efficient flow discharge and duration for flushing the sandbars are about 2000 m3/s and 10 days respectively.
At the river confluences of the upper Yellow River, flows carrying hyperconcentrated sediment merge together, and in flood season the merging usually causes severe deposition and dramatic change in bed morphology. In this study, we investigate the morphological process at hyperconcentrated confluences through laboratory experiment, field observation, and theoretical analysis, and develop a new method for predicting sediment deposition at the confluences. Results show that four basic elements of the morphological pattern can be identified: sandbars in the backwater zone, sandbars in the flow separation zone, a mainstream channel for water and sediment transport, and bars downstream of the separation zone. Because of turbulent diffusion, sediment particles carried by the hyperconcentrated flows enter the backwater zone upstream of the junction, and then form sandbar deposition with a volume proportional to the sediment load. We construct a model for calculation of the sediment deposition at river confluences and reveal its main factors: sediment load and discharge ratio of the incoming flows, water discharge of the main stem, and adaption coefficient of the incoming suspended loads. This model is applicable to prediction of the deposition at asymmetrical river confluences. Scour on the sandbars caused by heperconcentrated tributary flows depends on the discharge and duration of main stem floods. For the confluences on the upper Yellow River, the most efficient flow discharge and duration for flushing the sandbars are about 2000 m3/s and 10 days respectively.
引文
[1]Liu T H,Li C,Fan B L.Experiment study on flow pattern and sediment transportation at a 90°open-channel confluence[J].International Journal of Sediment Research,2012,27(2):178-187.
[2]Mosley M P.An experimental study of channel confluences[J].Journal of Geology,1976,84:535-562.
[3]Ghobadian R,Bajestan M S.Investigation of sediment patterns at river confluence[J].Journal of Applied Sciences,2007,7(10):1372-1380.
[4]Best J L.Sediment transport and bed morphology at river channel confluences[J].Sedimentology,1988,35(3):481-498.
[5]Best J L,Rhoads B L.Sediment transport,bed morphology and the sedimentology of river channel confluences[M]//Rice S P,Roy A,Rhoads B L.River Confluences,Tributaries and the Fluvial Network.John Wiley and Sons Ltd,The Atrium,Southern Gate,Chichester,West Sussex PO198SQ,England,2008:45-72.
[6]惠遇甲,张国生.交汇河段水沙运动和冲淤特性的实验研究[J].水力发电学报,1990,9(3):33-42.HUI Yujia,ZHANG Guosheng.Experimental studies on the behavior of flow and sediment movement at river confluence[J].Journal of Hydroelectric Engineering,1990,9(3):33-42.(in Chinese)
[7]李霞,侯极.入汇角60°时入汇口泥沙淤积试验研究[J].水电能源科学,2011,29(8):75-76.LI Xia,HOU Ji.Experimental study of sediment deposition for open channel confluence at junction angle60°[J].Water Resources and Power,2011,29(8):75-76.(in Chinese)
[8]刘同宦,王协康,郭炜,等.支流水沙作用下干流床面冲淤特征试验研究[J].长江科学院院报,2006,23(2):9-12.LIU Tonghuan,WANG Xiekang,GUO Wei,et al.Experimental study on bed morphology at channel confluence with tributary action[J].Journal of Yangzi River Scientific Research Institute,2006,23(2):9-12.(in Chinese)
[9]詹磊,董耀华,刘同宦.干支流直角交汇区水流泥沙运动特性初步研究[J].长江科学院院报,2010,27(8):6-11.ZHAN Lei,DONG Yaohua,LIU Tonghuan.Preliminary study on natures of flow structure and sediment transport in right-angled conjunction of main and branch channels[J].Journal of Yangzi River Scientific Research Institute,2010,27(8):6-11.(in Chinese))
[10]李文全.支流入汇弯曲河段水流运动特性试验研究[J].水运工程,2012(10):62-68.LI Wenquan.Experimental research on flow characteristics of inflow of tributaries to curve d reach[J].Port&Waterway Engineering,2012(10):62-68.(in Chinese)
[11]Hooke R L.Process on arid-region alluvial fans[J].Journal of Geology,1967,75(4):405-460.
[12]Bigelow P E,Benda L E,Miller D J,et al.On debris flows,river networks,and the spatial structure of channel morphology[J].Forest Science,2007,53(2):220-238.
[13]郭志学,余斌,曹叔尤,等.泥石流入汇主河情况下交汇口附近变化规律的试验研究[J].水利学报,2004(1):33-37.GUO Zhixue,YU Bin,CAO Suyou,et al.Experimental study on evolution of debris at the vicinity of confluence[J].Journal of Hydraulic Engineering,2004(1):33-37.(in Chinese)
[14]Tsai Y F.Three-dimensional topography of debris-flow fan[J].Journal of Hydraulic Engineer,ASCE,2006,132(3):307-318.
[15]王平,张原锋,侯素珍,等.黄河上游高含沙支流入汇与交汇区淤积形态试验研究[J].四川大学学报(工程科学版),2013,45(5):34-42.WANG Ping,ZHANG Yuanfeng,HOU Suzhen,et al.Experimental study on the processes of the hyperconcentrated flood of the tributaries’merging into the Upper Yellow River and the Deposition Pattern at the Confluence[J].Journal of Sichuan University(Engineering Science Edition),2013,45(5):34-42.(in Chinese)
[16]张原锋,王平,侯素珍,等.黄河上游干支流交汇区沙坝淤堵形成条件[J].水科学进展,2013,24(3):344-350.ZHANG Yuanfeng,WANG Ping,HOU Suzhen,et al.On conditions of sandbar clogging at confluences in the Upper Yellow River[J].Advances in Water Science,2013,24(3):344-350.(in Chinese)
[17]Zhang Y F,Wang P,WU B S,et al.An experimental study of fluvial processes at asymmetrical river confluences with hyperconcentrated tributary flows[J].Geomorphology,2015,230(2):26-36.
[18]支俊峰,时明立.“89.7.21”十大孔兑区洪水泥沙淤堵黄河分析[M]//汪岗,范昭.黄河水沙变化研究:第一卷.郑州:黄河水利出版社,2002:460-471.ZHI Junfeng,SHI Mingli.Analysis on clogging to the Yellow River caused by flood and sediment of ten tributaries on July 21,1989[M]//WANG Gang,FAN Zhao.Research on changes of water and sediment of the Yellow River:Vol.I.Zhengzhou:Yellow River Press,2002:460-471.(in Chinese)
[19]谢鉴衡.河流模拟[M].北京:水利水电出版社,1990.XIE Jianheng.River Modelling[M].Beijing:Water and Power Press,1990.(in Chinese)
[20]张红武,江恩惠,白咏梅,等.黄河高含沙洪水模型的相似律[M].郑州:河南科学技术出版社,1994.ZHANG Hongwu,JIANG Enhui,BAI Yongmei,et al.The scale laws of model similarity of hyperconcentrated flows[M].Zhengzhou:Henan Science and Technology Press,1994.(in Chinese)
[2]Mosley M P.An experimental study of channel confluences[J].Journal of Geology,1976,84:535-562.
[3]Ghobadian R,Bajestan M S.Investigation of sediment patterns at river confluence[J].Journal of Applied Sciences,2007,7(10):1372-1380.
[4]Best J L.Sediment transport and bed morphology at river channel confluences[J].Sedimentology,1988,35(3):481-498.
[5]Best J L,Rhoads B L.Sediment transport,bed morphology and the sedimentology of river channel confluences[M]//Rice S P,Roy A,Rhoads B L.River Confluences,Tributaries and the Fluvial Network.John Wiley and Sons Ltd,The Atrium,Southern Gate,Chichester,West Sussex PO198SQ,England,2008:45-72.
[6]惠遇甲,张国生.交汇河段水沙运动和冲淤特性的实验研究[J].水力发电学报,1990,9(3):33-42.HUI Yujia,ZHANG Guosheng.Experimental studies on the behavior of flow and sediment movement at river confluence[J].Journal of Hydroelectric Engineering,1990,9(3):33-42.(in Chinese)
[7]李霞,侯极.入汇角60°时入汇口泥沙淤积试验研究[J].水电能源科学,2011,29(8):75-76.LI Xia,HOU Ji.Experimental study of sediment deposition for open channel confluence at junction angle60°[J].Water Resources and Power,2011,29(8):75-76.(in Chinese)
[8]刘同宦,王协康,郭炜,等.支流水沙作用下干流床面冲淤特征试验研究[J].长江科学院院报,2006,23(2):9-12.LIU Tonghuan,WANG Xiekang,GUO Wei,et al.Experimental study on bed morphology at channel confluence with tributary action[J].Journal of Yangzi River Scientific Research Institute,2006,23(2):9-12.(in Chinese)
[9]詹磊,董耀华,刘同宦.干支流直角交汇区水流泥沙运动特性初步研究[J].长江科学院院报,2010,27(8):6-11.ZHAN Lei,DONG Yaohua,LIU Tonghuan.Preliminary study on natures of flow structure and sediment transport in right-angled conjunction of main and branch channels[J].Journal of Yangzi River Scientific Research Institute,2010,27(8):6-11.(in Chinese))
[10]李文全.支流入汇弯曲河段水流运动特性试验研究[J].水运工程,2012(10):62-68.LI Wenquan.Experimental research on flow characteristics of inflow of tributaries to curve d reach[J].Port&Waterway Engineering,2012(10):62-68.(in Chinese)
[11]Hooke R L.Process on arid-region alluvial fans[J].Journal of Geology,1967,75(4):405-460.
[12]Bigelow P E,Benda L E,Miller D J,et al.On debris flows,river networks,and the spatial structure of channel morphology[J].Forest Science,2007,53(2):220-238.
[13]郭志学,余斌,曹叔尤,等.泥石流入汇主河情况下交汇口附近变化规律的试验研究[J].水利学报,2004(1):33-37.GUO Zhixue,YU Bin,CAO Suyou,et al.Experimental study on evolution of debris at the vicinity of confluence[J].Journal of Hydraulic Engineering,2004(1):33-37.(in Chinese)
[14]Tsai Y F.Three-dimensional topography of debris-flow fan[J].Journal of Hydraulic Engineer,ASCE,2006,132(3):307-318.
[15]王平,张原锋,侯素珍,等.黄河上游高含沙支流入汇与交汇区淤积形态试验研究[J].四川大学学报(工程科学版),2013,45(5):34-42.WANG Ping,ZHANG Yuanfeng,HOU Suzhen,et al.Experimental study on the processes of the hyperconcentrated flood of the tributaries’merging into the Upper Yellow River and the Deposition Pattern at the Confluence[J].Journal of Sichuan University(Engineering Science Edition),2013,45(5):34-42.(in Chinese)
[16]张原锋,王平,侯素珍,等.黄河上游干支流交汇区沙坝淤堵形成条件[J].水科学进展,2013,24(3):344-350.ZHANG Yuanfeng,WANG Ping,HOU Suzhen,et al.On conditions of sandbar clogging at confluences in the Upper Yellow River[J].Advances in Water Science,2013,24(3):344-350.(in Chinese)
[17]Zhang Y F,Wang P,WU B S,et al.An experimental study of fluvial processes at asymmetrical river confluences with hyperconcentrated tributary flows[J].Geomorphology,2015,230(2):26-36.
[18]支俊峰,时明立.“89.7.21”十大孔兑区洪水泥沙淤堵黄河分析[M]//汪岗,范昭.黄河水沙变化研究:第一卷.郑州:黄河水利出版社,2002:460-471.ZHI Junfeng,SHI Mingli.Analysis on clogging to the Yellow River caused by flood and sediment of ten tributaries on July 21,1989[M]//WANG Gang,FAN Zhao.Research on changes of water and sediment of the Yellow River:Vol.I.Zhengzhou:Yellow River Press,2002:460-471.(in Chinese)
[19]谢鉴衡.河流模拟[M].北京:水利水电出版社,1990.XIE Jianheng.River Modelling[M].Beijing:Water and Power Press,1990.(in Chinese)
[20]张红武,江恩惠,白咏梅,等.黄河高含沙洪水模型的相似律[M].郑州:河南科学技术出版社,1994.ZHANG Hongwu,JIANG Enhui,BAI Yongmei,et al.The scale laws of model similarity of hyperconcentrated flows[M].Zhengzhou:Henan Science and Technology Press,1994.(in Chinese)