Process and Evolution Mechanism of Bed Formation in Curved Alluvial Channels

doi:10.11988/ckyyb.20230580

Abstract

Abstract:

The unique geometric boundary characteristics of alluvial bends result in distinct water and sediment transport behaviors and bed evolution dynamics compared to other channel types. To simulate the natural evolution of riverbed scour and siltation in alluvial bends, we employed a natural modeling approach to replicate a representative bend channel in a laboratory flume to investigate the influence of varying water and sediment conditions on the formation and development of bends. The experiments reveal the following: 1) A longer cycle of incoming sediment with lower intensity results in a quicker attainment of dynamic equilibrium in the curved river channel, with a narrower stable channel width. 2) Throughout the formation and development of the bend, morphological changes in the channel are primarily dominated by the prevailing water and sediment conditions. 3) Specifically, within a certain range of variation, shorter cycles of sediment transport, reduced incoming flow rate, and higher sediment concentrations facilitate the development of a more pronounced curvature in the channel. 4) Conversely, higher flow rates causing scouring of shallow areas tend to shape the bend into a wider and shallower cross-section. The adjustments in channel curvature and cross-sectional morphology are predominantly driven by changes in water and sediment transport dynamics, highlighting their significant role in shaping channel morphology.

Key words: curved river channel, bed formation process, evolutionary mechanism, channel morphology, natural model, model test

CLC Number:

TV147.3

QU Geng, YANG Han-lin, CHEN Yi-ming, ZHENG Cheng-tai, HU Cheng-wei, LUAN Hua-long. Process and Evolution Mechanism of Bed Formation in Curved Alluvial Channels[J]. Journal of Yangtze River Scientific Research Institute, 2024, 41(8): 15-22.

Figures/Tables 14

Fig.1 Schematic diagram of the experimental flume

Fig.2 Photograph of initial experimental flume

Fig.3 Initial model sand layering

Table 1 Experimental conditions of bed-formation in flume

试验分组	流量/ (L·s^-1)	含沙量/ (kg·m^-3)	放水历时/h	循环周期/h
	10	0.6	6.0
	20	0.8	4.5
A	30	1.2	3.0	24
	20	0.8	4.5
	10	0.6	6.0
	10	0.6	4.0
	20	0.8	3.0
B	30	1.2	2.0	16
	20	0.8	3.0
	10	0.6	4.0
	10	0.8	4.0
	20	1.0	3.0
C	30	1.4	2.0	16
	20	1.0	3.0
	10	0.8	4.0
	20	0.8	4.0
	30	1.0	3.0
D	40	1.4	2.0	16
	30	1.0	3.0
	20	0.8	4.0

Fig.4 Changes in channel morphology of each experimental group

Fig.5 Changes of bending coefficients over time

Fig.6 Morphological changes at typical cross-sections

Fig.7 Changes of river widths over time

Fig.8 Changes of average width-to-depth ratios over time

Fig.9 Changes of water surface slopes over distance

Fig.10 Changes of average flow velocities over distance

Fig.11 Changes of experimental circulation strengths at typical cross-sections over time

Table 2 Characteristic values of morphological elements and water-sand conditions

组次	水沙作用周期T/h	总来沙量W/kg	总来水量V/m³	相对平均弯曲系数	相对平均水面宽	相对平均宽深比
A	24	4 665.6	5 616	0.05	2.72	0.05
B	16	3 110.4	3 744	0.11	3.45	0.31
C	16	3 859.2	3 744	0.16	3.20	-0.08
D	16	6 048.0	6 048	0.04	4.66	0.73

Fig.12 Relationship between the absolute change of morphological elements(M) and the absolute change of water-sand conditions(N)

[1]	LIU Bo-cheng, LI Guang-ning, HAN Yan-cheng, LIU Yong-de, SUN Shuang-ke. Experimental Study on Optimizing Energy Dissipation by Adding Pier to Steep Chute of Open Channel in Wet Collapsible Loess Area [J]. Journal of Yangtze River Scientific Research Institute, 2024, 41(5): 95-102.
[2]	LIU Zhong-feng, HUANG Ben-sheng, LIU Da, LI Ming. Physical Model Test on the Scale of Drainage Pump Station on Tidal River [J]. Journal of Yangtze River Scientific Research Institute, 2024, 41(4): 23-28.
[3]	MA Peng-jie, WEI Kai, KANG Jing-wei, RUI Rui, CAI Zheng-qian, XIA Rong-ji. Mechanical Mechanism of Single Row of Micro Piles Strengthening Gently Inclined Long Fissured Soil Slope [J]. Journal of Yangtze River Scientific Research Institute, 2024, 41(3): 178-185.
[4]	LU An-dian, TANG Xin-wei, YAN Zhen-rui, MAI Sheng-wen, YAO Guang-liang. Full-scale Model Test on Tensioning Technology of Prestressed Lining with Unbonded Circular Anchor [J]. Journal of Yangtze River Scientific Research Institute, 2024, 41(3): 142-147.
[5]	YI Fu, TAO Han, DU Chang-bo, QI Xu-peng, ZHAI Wei-kun, XU Zhan. Modelling of Overtopping Break of Large Scale Tailings Pond Using Composite Model Sand [J]. Journal of Yangtze River Scientific Research Institute, 2024, 41(1): 83-89.
[6]	ZHU Jie-bing, LÜ Si-qing, WANG Bin, ZHU Yong-suo. Research Review of Scaled Physical Model Test of Water Inrush Disaster in Tunnel [J]. Journal of Yangtze River Scientific Research Institute, 2024, 41(1): 98-106.
[7]	CAO Wei-ping, LI Qing-yuan, TAO Peng, ZHAO Min. Model Test on Bearing Behaviors of Battered Piles under Horizontal Eccentric Loads [J]. Journal of Yangtze River Scientific Research Institute, 2023, 40(9): 118-125.
[8]	YAN Peng-peng. Hydraulic Characteristics of Spillway of a Labyrinth Weir in Kenya [J]. Journal of Yangtze River Scientific Research Institute, 2023, 40(8): 92-96.
[9]	GU Jian-yong, ZHANG Qiang, LU Xiao-chun, HU Jing, ZHU Jun-wei. Centrifugal Model Test on Deformation Mechanism of Reservoir Bank Landslide under Reservoir Water Level Fluctuation [J]. Journal of Yangtze River Scientific Research Institute, 2023, 40(6): 166-172.
[10]	HAN Qi-yuan, XU Gui-zhong, LI Ming-dong, WENG Jia-xing. Model Test of Intermittent Vacuum Preloading Treatment of Dredged Slurry with High Water Content [J]. Journal of Yangtze River Scientific Research Institute, 2023, 40(4): 113-118.
[11]	FANG Tao, LIANG Lian, YAN Jian-wei. Experimental Study on Stratum Deformation Caused by Shield Tunnelling at Different Buried Depths [J]. Journal of Yangtze River Scientific Research Institute, 2023, 40(3): 85-92.
[12]	CHEN Zi-qiang, DENG Yue-bao, SUN Jia-feng, SHAO Fei-yu, ZHANG Ri-hong. Influence of Drainage Time on Bearing Characteristics of Static Drill Rooted Drainage Pile [J]. Journal of Yangtze River Scientific Research Institute, 2023, 40(3): 112-116.
[13]	ZHANG Xin, LUO Qi-feng, TU Guo-xiang, TANG Hao. Regularities of Water-Air Migration in Deposits Containing Crushed Stone Interlayer under Intermittent Rainfall [J]. Journal of Yangtze River Scientific Research Institute, 2023, 40(10): 123-130.
[14]	LI Shao-wei, ZHANG Wen-chuan, WANG Jun-xing, ZHOU Zhao. Hydraulic Characteristics of Stepped Spillway with Trapezoidal Concave Angle [J]. Journal of Yangtze River Scientific Research Institute, 2022, 39(6): 56-63.
[15]	YANG Qing-hua, WANG Zi-cong, YANG Qian, ZHANG Yu-qian. Erosion Characteristics of Exposed River-crossing Pipe under the Protection of Heavy Block [J]. Journal of Yangtze River Scientific Research Institute, 2022, 39(4): 99-105.