Experimental Investigation on Energy Dissipation in Diversion Tunnel at the Head of Canal

doi:10.11988/ckyyb.20240304

Abstract

Abstract:

[Objective] The flow patterns of energy dissipation inside tunnels are complex, and theoretical calculations cannot meet design requirements. This research aims to: (1) verify the rationality of design parameters for energy dissipation in diversion tunnels at canal head based on hydraulic model tests; (2) propose an energy dissipation layout suitable for specific projects through model optimization to address high wave height inside the tunnel, insufficient clearance below the tunnel crown, and cavitation and erosion. [Methods] A hydraulic model test with a scale of 1∶1.5 was selected to simulate the diversion channel, pressurized tunnel, in-tunnel gate chamber, energy dissipation section, and a downstream section of free-flow tunnel. Additionally, an emergency gate shaft and the ventilation pipe behind the gate were simulated. A water tank was used as the model reservoir. The project involved three different discharge conditions, each with varying reservoir water levels, resulting in eight typical working conditions for testing. Then, based on the hydraulic model test results under different conditions, the downstream flow pressure characteristics, cavitation characteristics of the weir surface behind the operating gate, pressure characteristics of the gradually expanding stilling basin floor and sidewalls, flow connection patterns, and energy dissipation performance were obtained. Finally, the dimensions of the stilling basin section and the free-flow tunnel were improved, and wave suppression measures were optimized based on the test results. [Results] The hydraulic model test revealed shortcomings in the original energy dissipation scheme and proposed a combined layout of “stilling basin + wave suppression beam” suitable for in-tunnel energy dissipation. The test results showed: 1) the maximum wave height inside the free-flow tunnel was reduced by 67%, and the tunnel crown clearance met safe water conveyance requirements; 2) The local minimum cavitation number of the water flow at the curved section of the weir surface and the expanded section of the sidewalls behind the operating gate was about 0.37, indicating a low likelihood of cavitation erosion; 3) The root mean square of fluctuating pressure at measuring points along the stilling basin floor did not exceed 1.0×9.81 kPa, meeting structural design requirements. [Conclusion] This study proposes a combined energy dissipation method of “stilling basin + wave suppression beam” to address problems of high wave height and insufficient tunnel crown clearance in the original scheme. Compared with traditional submerged energy dissipators, the combined method significantly improves dissipation efficiency and has better energy dissipation characteristics. Hydraulic model tests verify the feasibility of the optimized scheme. The energy dissipation scheme is effective in solving the problems of large waves and insufficient tunnel crown clearance in similar projects. It is effective under multiple reservoir water levels and discharge conditions, and the wave suppression beam, as an in-tunnel energy dissipation structure, has little impact on tunnel flow capacity, demonstrating certain universality.

Key words: water diversion project, energy dissipation type, tunnel, wave-absorbing beam, model test

CLC Number:

TV671

ZHONG Kun, YAN Fu-gen, GUO Jian-hua, YI Shun, LI Min-kang. Experimental Investigation on Energy Dissipation in Diversion Tunnel at the Head of Canal[J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(7): 119-125.

Figures/Tables 13

Fig.1 Schematic diagram of vertical well type water intake tower in tunnel 1#

Table 1 Main scale relationship of the model

物理量	长度	流速	时间	流量	糙率
比尺关系	λ_L	λ_V= $λ L 1 / 2$	λ_t= $λ L 1 / 2$	λ_V= $λ L 5 / 2$	λ_Q= $λ L 1 / 6$
比尺数值	15	3.87	3.87	871.4	1.57

Table 1 Main scale relationship of the model

物理量	长度	流速	时间	流量	糙率
比尺关系	λ_L	λ_V= $λ L 1 / 2$	λ_t= $λ L 1 / 2$	λ_V= $λ L 5 / 2$	λ_Q= $λ L 1 / 6$
比尺数值	15	3.87	3.87	871.4	1.57

Fig.2 Hydraulic model of canal head diversion project

Fig.3 Layout of pressure measurement points

Table 2 Model test conditions

工况编号	库水位/ m	输水流量/ (m³·s^-1)	下游无压隧洞进口水深/m	闸门开度/m
1	110.26	9.2	2.76	0.23
2		7.3	2.32	0.18
3		5.5	1.85	0.13
4	105.85	9.2	2.76	0.27
5		7.3	2.32	0.20
6		5.5	1.85	0.15
7	80.85	7.3	2.32	1.13
8	80.85	5.5	1.85	0.55

Table 3 Water level and fluctuation of gate shaft

工况编号	库水位/m	输水流量/ (m³·s^-1)	闸门内水位/m
1	110.26	9.2	108.87	0.09
2		7.3	109.35	0.06
3		5.5	109.69	0.05
7	80.85	7.3	80.85	0.08
8	80.85	5.5	80.36	0.05

Fig.4 Flow state of energy dissipation section under the first working condition

Fig.5 Waterline and wave amplitude under the first working condition

Fig.6 Optimization scheme and dimensions

Fig.7 Flow pattern at typical locations under the first condition in the optimized scheme

Fig.8 Waterline and wave amplitude under the first condition in the optimized scheme

Table 4 Time-averaged pressure during control and relief operation of working gate ×9.81 kPa

区域	桩号/m	工况1	工况2	工况3	工况4	工况5	工况6
底板中轴线	0+168.0	31.41	31.64	32.43	27.18	27.63	28.14
	0+173.0	31.52	31.92	32.60	27.57	27.83	28.26
	0+175.3	31.61	31.88	32.55	27.57	27.86	28.28
	0+179.0	30.77	31.49	32.33	27.00	28.41	28.26
	0+181.7	0.38	0.34	0.17	0.64	0.41	0.17
	0+183.8	-0.75	-0.93	-1.01	0.61	0.34	0.27
	0+187.6	1.57	2.25	1.24	2.35	1.80	1.42
	0+191.2	3.49	2.97	2.53	3.58	3.04	2.59
	0+191.5	2.46	2.27	2.20	3.28	2.77	2.33
	0+203.6	4.10	3.38	3.36	4.36	3.93	3.41
	0+214.2	2.69	2.10	1.90	2.66	2.29	1.83
底板近边墙	0+175.3	31.61	31.98	32.58	27.60	27.80	28.28
	0+177.2	31.46	31.88	32.55	27.50	28.01	28.44
	0+179.0	30.78	31.34	32.36	27.02	27.45	28.07
	0+181.7	0.36	0.31	0.24	0.89	0.34	0.29
	0+183.8	-0.90	-1.02	-1.13	0.01	-0.21	-0.36
	0+186.1	0.97	1.00	0.72	1.95	1.50	1.17
	0+189.5	2.42	2.09	1.84	2.92	2.48	2.03
陡坡段侧边墙	0+181.7	0.25	0.13	0.07	0.41	0.22	0.08
	0+183.8	0.06	-0.10	-0.18	0.48	0.31	0.25
	0+187.6	1.85	1.46	1.27	2.35	1.90	1.49
	0+191.2	3.32	2.86	2.48	3.41	2.96	2.50
顶部中心线	0+168.0	29.55	29.84	30.48	25.46	25.80	26.34
	0+173.0	29.62	30.05	30.78	25.73	27.36	26.46
	0+175.3	29.65	29.03	30.78	25.76	26.01	26.46
	0+179.0	29.94	30.35	31.01	26.01	26.25	26.66

Fig.9 Result of water flow pulsation pressure

[1]	WANG Shuai, ZHANG Jia-lin, HU Shao-wei, YOU Jian-hua, YANG Yu-ming. Lateral Bearing Characteristics of Bucket Foundation Breakwaters in Soft Soil of Port Areas [J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(7): 174-180.
[2]	GAO Su, CHEN Cheng. Prediction of Shield Tunneling Attitude Based on WM-CTA Method [J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(7): 181-189.
[3]	WANG Sheng-li, DONG Shu-qing, HUANG Yu, SONG Zhi-han, WU Tong, ZHENG Shan-suo. Research Progress on Anti-floating Design of Underground Structures [J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(6): 154-161.
[4]	BO Yin, WANG Cong, FENG Yan-fang, ZHANG Bin, ZHANG Ying, GUO Xiao-gang, YAO Jin-song, WEI Lai, CHEN Rong, XU Chen. Similarity Criterion Based on the Analytical Solution of Heat Conduction Equation in Frozen Soil [J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(5): 184-191.
[5]	WANG Ji-min, LIU Zong-xian, DU Cheng-bo, MA Bin, ZHANG Zi-liang. Experimental Study on Hydraulic Characteristics of the Aerated Flow over Spillway in Lianghekou Hydropower Station [J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(4): 103-111.
[6]	LI Jian, TAO Bo-wen, CAI Qi, YAO Jian-qiang, WANG Gan. Intelligent Prediction of Tunneling Parameters for Large Diameter Slurry Shield [J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(3): 148-155.
[7]	HUANG Shu-ling, WANG Xiang-xiang. Bearing Characteristics of Confined Concrete Box Steel Arch in Soft Rock Tunnel [J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(2): 1-8.
[8]	MU Yi-long, ZHOU Xiao-wen, LIU Huai-yu. Deformation Control Technology for New Shield Tunneling Overcrossing an Existing Tunnel with Extremely Small Spacing [J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(2): 122-128.
[9]	WU Zhen-hui, WANG Meng, LIU Yang-yang, WU Bi, XIAO Yang, ZHANG Ke-ke. Predicting the Impact of Water Diversion Project from Yangtze River to Hanjiang River on Water Environment in the Water Source Area of Three Gorges Reservoir [J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(2): 194-203.
[10]	NIU Guang-li, LI Tian-yang, XUE Guang-wen, CUI Peng, QIN Peng, FANG Hao-wen. Research and Application of Intelligent Safety Monitoring and Early Warning System for Long-distance Water Diversion Projects [J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(2): 204-210.
[11]	ZHANG Guo-qiang, CUI Zhen, YAN Tian-you, ZHANG Mao-chu, LI Jian-he. Deformation and Failure Characteristics of Deep-buried Water Diversion Tunnel Crossing Active Fault Zone and Corresponding Adaptive Measures [J]. Journal of Changjiang River Scientific Research Institute, 2025, 42(1): 152-161.
[12]	CHU Zhao-wei, YU Shi-jie, LI Xing-yang, LU Xing-yu, WANG Xu, LUO Rui, WANG Tian-long. Indoor Model Test of Negative Pressure Drainage Method for Treatment of Engineering Mud [J]. Journal of Changjiang River Scientific Research Institute, 2024, 41(9): 114-122.
[13]	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 Changjiang River Scientific Research Institute, 2024, 41(8): 15-22.
[14]	LIU Cheng-kun, ZHANG Hang, JING Zheng, YANG Xing-yue, ZHANG Li. Three-dimensional Water Quality Deduction Method Based on Digital Twin Technology [J]. Journal of Changjiang River Scientific Research Institute, 2024, 41(8): 189-196.
[15]	GAO Xue-ping, WEI Nan-jiang, LIU Yin-zhu. Hydraulic Characteristics at Side Outlet of Tunnel Elbow [J]. Journal of Changjiang River Scientific Research Institute, 2024, 41(7): 94-102.