Journal of Hydroelectric Engineering

水力发电学报

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2020 Vol. 39, No. 7 Published: 2020-07-25

	1	Study on development trend of seismic safety theory for high dams ^Hot!
		KONG Xianjing, CHEN Jianyun, ZOU Degao
		DOI: 10.11660/slfdxb.20200701
		Hydropower projects are key infrastructures in the development and utilization of China’s green and clean energy, flood control and disaster reduction, and they will be an important part of the major infrastructure projects for a long time. At present, high dams are core hydropower structures, and their seismic safety of operation is a crucial issue. This paper presents a comprehensive review on the developing history and current situation of high dam seismic safety in China and other countries, and examines thoroughly the problems existing in the current research. It indicates that the research on aseismic dam design in China has been already at a globally advanced level, but many technical challenges still exist in the design of 300 m high dams. Particularly, no substantial breakthrough has yet been achieved in the idea or methodology of aseismic designs, making it difficult to meet the requirements of rapidly developing practice of 300 m high dams. This may bring about potential risks as more and more projects begin to operate. In view of the present situation, this paper elaborates in four aspects the future development trend and key scientific problems in high dam seismic safety research, which would be useful for the decision-making of national key project construction and sustainable development.
		2020 Vol. 39 (7): 1-11 [Abstract] ( 196 ) PDF (433 KB) ( 750 )

	12	Modified interface model for mixed-mode fracture analysis using discrete element method
		SUN Jian, JIANG Hui, HE Jialong, ZHOU Yuande
		DOI: 10.11660/slfdxb.20200702
		Reasonable characterization of fracture process zone is key to nonlinear fracture simulation of quasi-brittle materials, such as concrete and rock. This paper, based on a framework of cohesive zone model, presents an extension of the frictional contact model between discrete blocks in the deformable discrete element method. In this model, we adopt a new cracking criterion by combining the mixed-mode BK fracture energy criterion with to the Mohr-Coulomb criterion with tension-cutoff, and formulate nonlinear interface constitutive equations capable of modeling tension-shear and compression-shear mix-mode loading conditions. And Voronoi tessellation is used to eliminate the dependence of fracture propagation paths on the geometric division of discrete blocks. Through parametric analysis of the Galvez asymmetric three-point bending beam tests and adopting suitable softening parameters, we achieve a good agreement between the results of this model and the test data, verifying its capability in simulating uniaxial tension and mixed-mode fractures.
		2020 Vol. 39 (7): 12-20 [Abstract] ( 158 ) PDF (860 KB) ( 329 )

	21	Innovations in technology and management of dam construction and their application to Xiluodu hydropower station on Jinsha River
		FAN Qixiang, LU Youmei, ZHANG Chaoran, LI Guo
		DOI: 10.11660/slfdxb.20200703
		The Xiluodu hydropower station is the world’s top three to date, with its overall scale and technical difficulty ranking high globally among the large hydropower projects. In its construction, a great many technical problems have been solved and a wealth of management innovation accomplished. Using the case study method, this paper describes systematically a batch of innovation achievements in the dam construction, such as intelligent construction technology of 300m-class super-high arch dams, temperature control and crack prevention technology for mass concrete and lining concrete, and construction technology of high-velocity-flow spillway tunnels with large flood discharge and giant underground powerhouses. We also examine the fruits achieved via the concept of green hydropower construction, implementation of environmental planning and design, and innovation in construction technologies. We suggest and discuss a number of new concepts and methods–a concept of standardized, orderly, coordinated and healthy construction management for large hydropower projects; a project management system comprising six goals and nine supporting factors; an innovative management mode of industry-university-research-application collaboration; a method to optimize engineering planning, design and construction; a one-step finishing method based on dynamic analysis of complex rock mass engineering. These achievements ensure safe, high quality and efficient on-schedule construction of this hydropower station and its stable operation, generating tremendous social and economic benefits and
		2020 Vol. 39 (7): 21-33 [Abstract] ( 387 ) PDF (421 KB) ( 763 )

	34	Intelligent control theory of earth-rock dam compaction
		ZHANG Qinglong, AN Zaizhan, LIU Tianyun, ZHANG Zhaosheng, HUANGFU Zehua, LI Qingbin
		DOI: 10.11660/slfdxb.20200704
		Effective compaction quality control is crucial to safe and stable operation of earth-rock dams. This paper develops a novel intelligent control theory for intelligent decision-making and automatic control of earth-rock dam compaction. This theory adopts the structure of ternary theory. Based on an artificial intelligence algorithm and operation research, it uses an intelligent decision-making unit to formulate an optimal compaction plan from global perspective; and at its bottom level aimed at a problem of how to control the actuator, it achieves an intelligent control of the compaction process by using the automatic control theory and a double closed-loop control mode. Application examples show this new theory can achieve a successful intelligent control of earth-rock dam compaction and significantly improve compaction efficiency while ensuring compaction quality. It would provide key theoretical and technical support not just for intelligent construction of earth-rock dams, but with application prospects in highways, railways and airports.
		2020 Vol. 39 (7): 34-40 [Abstract] ( 308 ) PDF (500 KB) ( 633 )

	41	Predicting toughness and fracture process zone of mode I concrete fracture using theory of critical distance
		TONG Gusheng, CHEN Shusong, ZHANG Tianzhu
		DOI: 10.11660/slfdxb.20200705
		To study the performance of concrete fractures, using the line method of the theory of critical distance (TCD), this paper derives functional relationships between generalized critical distance, nominal fracture toughness, and tensile strength of concrete. The results show that the TCD line method can obtain fracture toughness slightly more conservative than that of the double K fracture criterion and it gives an estimated value of the corresponding fracture process zone (FPZ) length. It is applied to an analysis of the fracture toughness and FPZ of geometrically similar concrete beams, and comparison with the unstable fracture toughness obtained using the double K fracture criterion shows the feasibility of the line method.
		2020 Vol. 39 (7): 41-51 [Abstract] ( 141 ) PDF (410 KB) ( 294 )

	52	Study on detection method of dam surface cracks based on full convolution neural network
		CHEN Bo, ZHANG Hua, WANG Shuang, WANG Haoran, LIU Zhaowei, LI Yonglong, XIE Hui
		DOI: 10.11660/slfdxb.20200706
		Aimed at the drawback of conventional crack detection methods not applicable to the detection of dam surface cracks, this paper presents a new method for quantitative detection based on a full convolution network (FCN). This method combines image preprocessing with morphological post-processing to achieve an improvement on detection accuracy through optimizing raw data and predictions. Oriented at dam surface data, it further improves the accuracy by modifying the traditional FCN network into a more targeted crack detection network, namely a crack full convolution network (C-FCN). And its quantitative information is extracted based on the imaging principle, which avoids complicated camera calibration and is more efficient and objective. We have applied it to in-situ measurements at a dam face and achieved a pixel accuracy of 75.13%, a recall rate of 86.84%, and an intersection ratio of 60.15%. These three indexes are improved by 5.61%, 16.56% and 13.22% respectively in comparison with the traditional FCN network. And the quantified error of detection is less than 5%, and the average opening of the cracks detected is less than 5 mm. Thus, our new detection method would provide a useful tool for dam surface risk assessment and maintenance of water dams.
		2020 Vol. 39 (7): 52-60 [Abstract] ( 249 ) PDF (2179 KB) ( 485 )

	61	Group decision study on Three Gorges reservoir's water impounding schemes
		WANG Liping, LI Ningning, MA Haoyu, YAN Xiaoran, WU Jiajie
		DOI: 10.11660/slfdxb.20200707
		Early impoundment at the end of flood season can improve the full storage rate of reservoirs at controllable risk and create significant benefits. Extensive studies have been conducted on the Three Gorges reservoir's operation schemes of water impounding at the end of flood season, but their focuses are quite different and they lack the support of decision-making technology in selecting water impounding schemes. This paper presents a group decision-making model of experts’ most-satisfaction to integrate the existing research fruits on the reservoir's impounding schemes for higher level decision making. We rank the available schemes using the method of cumulative prospect theory and the matrices of experts' decision, and then solve the model to maximize the satisfaction of the expert group. The results show that the best scheme is to start impoundment on September 11 and this can achieve greater benefits with a lower risk and agrees with the result of the traditional decision method, verifying the effectiveness of our group decision model. This model has fully considered experts' decision-making psychology and respects the group opinions of experts; thus it gives evaluation results that can be followed and provides a new effective approach to the reservoir's operation schemes of early water impounding.
		2020 Vol. 39 (7): 61-72 [Abstract] ( 114 ) PDF (667 KB) ( 276 )

	73	Spatiotemporal evolution of runoff based on extreme-point symmetric mode decomposition
		LI Jiqing, WANG Shuang, HUANG Jing, CHEN Siyu, ZHOU Ting, TIAN Yu
		DOI: 10.11660/slfdxb.20200708
		Studying the evolution trends of river runoff is of great significance for hydrological forecasting and rational allocation of water resources. In view of the multi-time scales and non-linear trend aliasing in runoff sequences, this paper presents an application of extreme-point symmetric mode decomposition (ESMD) to analysis of the spatiotemporal evolution of runoffs for the upper reach of the Yangtze River. Using ESMD, we decompose runoff sequences into various modes, including the annual, monthly, and daily runoff sequences for eight hydrological stations on the mainstream and tributaries of the reach. Then, we identify large-scale cyclic and non-linear trends using state components and trend residuals; obtain the sequences’ time periods, variation trends, and abrupt changes though examining the cycle diagrams, trend residuals, and time frequency analysis; and compare with previous methods. The results show that temporally, two types of dominant cycles are observable: annual cycles of 6 months, 1 year, 2 years, 4 years, and 22-23 years; and inter-annual cycles of 2 years, 6 years, and 10-11 years. Spatially, all the stations show a decreasing trend in the annual and inter-annual runoffs, except for the Zhutuo station featured with an increasing trend. The abrupt change patterns at the eight stations are not the same. This study demonstrates ESMD can excavate more hydrological characteristics of runoff through identifying the cycles, trends and mutations, opening up new ideas for spatiotemporal evolution analysis of river runoff.
		2020 Vol. 39 (7): 73-87 [Abstract] ( 142 ) PDF (3636 KB) ( 331 )

	88	Statistical trends of drift acceleration of tropical cyclones
		WANG Jing, LIU Yilong, SHAN Kaiyue, YU Xiping
		DOI: 10.11660/slfdxb.20200709
		Understanding the statistical trends of tropical cyclone movement is of great significance to revealing its mechanism and improving forecast accuracy. We examine certain trends of drift acceleration of tropical cyclones using the data observed for tracking the histories of 4907 cyclone events during 1979-2016, published by Joint Typhoon Warning Center (JTWC) and the National Hurricane Center (NHC). We found that tropical cyclones have a mean zonal acceleration close to 0 at low latitudes, while at high latitudes they tend to accelerate towards the east with an increasing mean zonal acceleration. And similar trends can be observed in the northern and southern hemispheres. Along the meridian, however, the acceleration trends vary across different basins, and the difference becomes more noticeable at higher latitudes.
		2020 Vol. 39 (7): 88-98 [Abstract] ( 159 ) PDF (1665 KB) ( 321 )

	99	Experimental investigation of flood inundation over typical urban streets
		DONG Boliang, XIA Junqiang, CHEN Jinhan
		DOI: 10.11660/slfdxb.20200710
		Global climate changes and increasingly frequent extreme weather events lead to higher frequency and intensity of urban flooding disasters. In-depth study on flood inundation over typical urban streets becomes essential to understand flooding mechanism and work out effective disaster-mitigating strategy and measures. This study establishes a flood inundation physical model for laboratory experiment to represent a urban street system and its complicated structure, inluding roads, sidewalks, buildings, greenbelts, and other street facilities. From the experimental results, we obtain a quantitative analysis on the effect of building density and greenbelt arrangement on flow inundation process. We come to the conclusions that (i) on the model road, the celerity of dam-break waves depends on initial water depth in the reservoir and road characteristics, while the influences of buildings and greenbelts are insignificant. (ii) Adding greenbelts or buildings to the system reduces the flow cross-sectional area, thereby increasing the flow depth on the road during flood events, but it can reduce the water volume around buildings or increase flow resistance so that more water is concentrated on the road. (iii) Peak depths in front of buildings are roughly proportional to the initial reservoir depth, and a large initial reservoir depth will cause a much stronger impact force on the buildings. This study supplies data for numerical model calibration and helps design urban streets facing outburst flooding threat.
		2020 Vol. 39 (7): 99-108 [Abstract] ( 149 ) PDF (2157 KB) ( 354 )

	109	Experimental study on optimization of inclination angles of deflector of vortex setting chamber
		WANG Pingyuan, LI Lin, TAN Yihai, ZHAO Faxin, MU Zhuoyun, HOU Jie
		DOI: 10.11660/slfdxb.20200711
		This paper reports a series of model tests on the sand-water separation performance of a vortex setting chamber (VSC) equipped with a flow deflector that is placed in horizontal, downward or upward direction toward the central orifice. The results show that in these three deflector conditions, the removal efficiency of the chamber is nearly the same but its sediment deposition differs. For a deflector tilted upward and downward, the total amount of sediment deposited in the VSC basin and on the deflector surface is less than that of a horizontal deflector. Usually a larger inclination angle results in a smaller deposition volume. The decrease in the amount of deposition in the upward deflector case is greater than that of a downward deflector. For the upward deflector, water consumption is lower than that in the downward or horizontal case and it decreases with an increasing upward angle. Thus, tilting the near-center edge of the deflector upward at a certain angle can effectively avoid sediment deposition on the deflector surface while reducing water consumption and sediment deposition in the VSC basin, which helps better optimize the design of vortex setting chambers.
		2020 Vol. 39 (7): 109-120 [Abstract] ( 89 ) PDF (5776 KB) ( 318 )