| INCIPIENT MOTION OF COARSE PARTICLES IN HIGH GRADIENT RIVERS |
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| 作者姓名： | Shengfa YANG Jiang HU Xingkui WANG |
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| 作者单位： | Shengfa YANG1，Jiang HU2 and Xingkui WANG31 Assoc. Prof.，Department of River and Ocean，Chongqing Jiaotong University，and Department of Hydraulic Engineering，Tsinghua University. Chongqing，400074，China. 2 Instructor，Department of River and Ocean，Chongqing Jiaotong University. Chongqing，400074，China. 3 Prof.，Department of Hydraulic Engineering，Tsinghua University，Beijing 100084，China. |
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| 基金项目： | ACKN0WLEDGEMENTS This study was financially supported by the Ministry of Communications ＂Study on Key Technologies of Bridge and Culvert Design on Shallow and Changing Rivers in Xinjiang Autonomous Region＂ （No. 2001-318-365-88）. |
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| 摘 要： | 1 INTRODUCTION To data, there are about 100 formulae for the incipient motion of sediment, among which, only about ten are convenient and practical. In 1936, using nondimensional drag force and the sediment’s Reynolds number, Shields (1936) presented the…
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| 关 键 词： | 河床 梯度 粗状颗粒 运动方向 泥沙 |
| 收稿时间： | 2004-11 |
| 修稿时间： | 2005-06 |
INCIPIENT MOTION OF COARSE PARTICLES IN HIGH GRADIENT RIVERS |
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| Shengfa YANG Jiang HU Xingkui WANG.INCIPIENT MOTION OF COARSE PARTICLES IN HIGH GRADIENT RIVERS[J].International Journal of Sediment Research,2006,21(3):220-229. |
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| Authors: | Shengfa YANG Jiang HU Xingkui WANG |
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| Abstract: | In Northwest China, there are many inland rivers that are characterized by high a gradient, coarse particles, a thick pebble and gravel layer, and small discharge and shallow water depth during the flood season. In these rivers, the motion of coarse particles has an important influence on the construction of various structures related to these rivers. In this study, the law of the motion of coarse particles is investigated in high gradient rivers. First, according to the rolling mode of particle motion, the forces acting on coarse particles were analyzed, and a formula was deduced to represent the incipient drag force for uniform coarse particles in a high gradient river. The flow velocity near the river bed, resistance coefficient, and weight of a coarse particle were taken into account to obtain the formula, which indicated that the incipient drag force is not related to the sediment Reynolds number, but closely related to the Froude number, which was also true for the Maxwell formula. Next, after comparing the various criteria for incipient motion of sediment, experiments were done to obtain data and determine the incipient motion of coarse particles. Based on the experiments, it was concluded that the motion type of "embedded" coarse material belongs to the motion of contact load, and the nondimensional unit-width sediment transport rate, which was put forward by Taylor in 1971, was chosen as the criterion in this study. Finally, based on the experimental data, the drag force formula was calibrated. The computed drag force agreed well with the measured values. Moreover, the formula derived in this study was compared with the Maxwell formula, another formula to study the incipient motion of particles in step-shaped mountainous rivers. The comparison indicates that the slope is the key factor in the two formulas, and the weight is an important force on the incipient motion of coarse particles in the current formula, but not in the Maxwell formula. |
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| Keywords: | River bed High gradient Coarse particle Incipient motion formula Froude number |
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