分汊河道平衡水深方法
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摘要
为了研究分汊河道的河床演变与航道水深,本文基于水力几何形态关系,得到分汊河道平衡水深计算方法。该方法对于不同断面形态的分汊河道均具有适用性,汊道与单一河道过水断面面积之比为分流比的6/7次方。应用于长江南京以下12. 5 m深水航道二期工程,计算得出的落成洲分汊河段断面的平均水深与多年平均水深基本一致,表明了平衡水深理论的可靠性。对福姜沙和世业洲分汊河段工程前的最大通航水深计算,亦与实际情况较为吻合;工程后的预测结果显示工程整治效果明显,世业洲和福姜沙左汊河段均能满足12. 5 m通航水深的要求,但福北水道仍无法达到12. 5 m通航水深。平衡水深方法提供了一种除数学模型和物理模型外预测河床演变趋势,计算出航道能维持的平衡水深,丰富了航道整治理论的同时,也为二期工程的实施提供科学依据与理论指导。
To investigate the evolution of riverbed and waterway depth of a branching river based on hydraulic geometry,this paper proposes a solution to equilibrium depth based on hydraulic geometry. This method is suitable for different cross-sectional shapes of waterway. The ratio of cross-sectional area of a distributary channel to the main stream is a power function of the waterway's bifurcation ratio with an exponent of 6/7. The theory was applied to the second phase of a 12. 5 m deepwater channel of the Yangtze River at Nanjing city. The average depth calculated in Luochengzhou was basically consistent with the average multi-year water depth,which showed the reliability of the equilibrium depth theory. The calculation of the maximum navigable depth of the Fujiangsha and Shiyezhou also agreed well with the actual depth. The forecast results after the second phase project showed that the project remediation effect was obvious,with Shiyezhou and Fujiangsha,in their left branches,able to meet the requirements of12. 5 m navigable depth. However,the Fubei waterway still could not reach this navigable depth. Results showed that the theory of equilibrium depth provides a method for predicting the evolution of a riverbed using mathematical and physical models. It can calculate the sustainable equilibrium depth of a channel,improving waterway regulation,and providing a scientific basis and theoretical guidance for the implementation of the second phase project.
To investigate the evolution of riverbed and waterway depth of a branching river based on hydraulic geometry,this paper proposes a solution to equilibrium depth based on hydraulic geometry. This method is suitable for different cross-sectional shapes of waterway. The ratio of cross-sectional area of a distributary channel to the main stream is a power function of the waterway's bifurcation ratio with an exponent of 6/7. The theory was applied to the second phase of a 12. 5 m deepwater channel of the Yangtze River at Nanjing city. The average depth calculated in Luochengzhou was basically consistent with the average multi-year water depth,which showed the reliability of the equilibrium depth theory. The calculation of the maximum navigable depth of the Fujiangsha and Shiyezhou also agreed well with the actual depth. The forecast results after the second phase project showed that the project remediation effect was obvious,with Shiyezhou and Fujiangsha,in their left branches,able to meet the requirements of12. 5 m navigable depth. However,the Fubei waterway still could not reach this navigable depth. Results showed that the theory of equilibrium depth provides a method for predicting the evolution of a riverbed using mathematical and physical models. It can calculate the sustainable equilibrium depth of a channel,improving waterway regulation,and providing a scientific basis and theoretical guidance for the implementation of the second phase project.
引文
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[11]孙志林,夏珊珊,朱晓,等.河口时变水流挟沙能力公式[J].清华大学学报(自然科学版),2010,50(3):383-386.SUN Zhilin,XIA Shanshan,ZHU Xiao,et al. Formula of time-dependent sediment transport capacity in estuaries[J]. Journal of Tsinghua University(science and technology),2010,50(3):383-386.
[12]孙志林,杨仲韬,高运,等.长江分汊河口水力几何形态[J].浙江大学学报(工学版),2014,48(12):2266-2270.SUN Zhilin,YANG Zhongtao,GAO Yun,at el. Hydraulic geometry of branching channels in Yangtze estuary[J].Journal of Zhejiang University(engineering science),2014,48(12):2266-2270.
[2]谢鉴衡.河床演变及整治[M].武汉:武汉大学出版社,2013.
[3]PITTALUGA M B,REPETTO R,TUBINO M. Channel bifurcation in braided rivers:Equilibrium configurations and stability[J]. Water resources research,2003,39(3):1046.
[4]LANE S N,RICHARDS K S. High resolution,two-dimensional spatial modelling of flow processes in a multi-thread channel[J]. Hydrological processes, 1998, 12(8):1279-1298.
[5]NEARY V S,ODGAARD A J. Three-dimensional flow structure at open-channel diversions[J]. Journal of hydraulic engineering,1993,119(11):1223-1230.
[6]BARKDOLL B D,HAGEN B L,ODGAARD A J. Experimental comparison of dividing open-channel with duct flow in T-junction[J]. Journal of hydraulic engineering,1998,124(1):92-95.
[7]DARGAHI B. Three-dimensional flow modelling and sediment transport in the River Klarlven[J]. Earth surface processes and landforms,2004,29(7):821-852.
[8]BERTOLDI W,TUBINO M. River bifurcations:experimental observations on equilibrium configurations[J]. Water resources research,2007,43(10):W10437.
[9]姚仕明,张超,王龙,等.分汊河道水流运动特性研究[J].水力发电学报,2006,25(3):49-52,57.YAO Shiming,ZHANG Chao,WANG Long,et al. Study on the characteristics of flow movement in branching river[J]. Journal of hydroelectric engineering,2006,25(3):49-52,57.
[10]ENSIGN S H,DOYLE M W,PIEHLER M F. The effect of tide on the hydrology and morphology of a freshwater river[J]. Earth surface processes and landforms,2013,38(6):655-660.
[11]孙志林,夏珊珊,朱晓,等.河口时变水流挟沙能力公式[J].清华大学学报(自然科学版),2010,50(3):383-386.SUN Zhilin,XIA Shanshan,ZHU Xiao,et al. Formula of time-dependent sediment transport capacity in estuaries[J]. Journal of Tsinghua University(science and technology),2010,50(3):383-386.
[12]孙志林,杨仲韬,高运,等.长江分汊河口水力几何形态[J].浙江大学学报(工学版),2014,48(12):2266-2270.SUN Zhilin,YANG Zhongtao,GAO Yun,at el. Hydraulic geometry of branching channels in Yangtze estuary[J].Journal of Zhejiang University(engineering science),2014,48(12):2266-2270.