Journal of Hydroelectric Engineering

水力发电学报

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2015 Vol. 34, No. 6 Published: 2015-06-25

	1	Study and application of fuzzy support vector machine based on gray correlation analysis to streamflow forecasting
		ZHU Shuang, ZHOU Jianzhong, MENG Changqing, XIAO Ge, CHEN Jianguo
		This paper presents a fuzzy support vector machine forecasting method based on gray correlation analysis for forecasting streamflow featured with nonlinearity and randomness. This method takes advantage of traditional SVM in its arbitrary approximation ability and nonlinear mapping, and adopts a fuzzy membership function to consider the impacts of changes in climate and watershed surface conditions on streamflow forecasting results. Predictor selection is difficult in long-term streamflow forecasting and the correlation coefficient method can only measure linear correlation between factors. Hence, we adopt gray correlation analysis to quantify the degree of association and pick out predictors that have significant impact on the streamflow. This model was applied to forecasting of monthly stream flow at Shigu, a control station of the upper Jinsha river. Comparison with the GRNN model and A-FSVM model shows that the method is effective and improves the accuracy of long-term streamflow forecasting.
		2015 Vol. 34 (6): 1-6 [Abstract] ( 200 ) PDF (595 KB) ( 456 )

	7	Detection of variations in precipitation-runoff relationship based on Archimedean Copula
		GUO Aijun，HUANG Qiang，WANG Yimin，LI Yunyun，CHANG Jianxia，Mo Shuhong
		Guide::null
		Precipitation-runoff relationship is a core issue in engineering hydrology. Copula functions have advantages and flexibility in capturing dependences between variables. This study adopted an Archimedean Copula function to construct such a distribution relationship and detect its abrupt variation points based on the monthly and yearly scales of precipitation and runoff. The Jinghe river basin features precipitation and runoff following the Gamma and logarithmic normal distributions respectively, and according to Copula function analysis its abrupt point on precipitation-runoff relationship occurred in 1996. At the abrupt point, we divided the time series into two parts for the periods 1960~1996 and 1997~2010. Then, the analysis shows that a significant change in the relationship occurred, i.e. a reduction of 30% in water yield during 1997~2010 relative to 1960~1996 in the same conditions of precipitation. And the less precipitation, the greater reduction in water yield, with its maximum of 37.59% at P=500mm. This abrupt variation point on precipitation-runoff relationship calculated by Copula function is demonstrated by considering the variation in human activities, etc.
		2015 Vol. 34 (6): 7-13 [Abstract] ( 234 ) PDF (1204 KB) ( 476 )

	14	Study of rainfall changes at Qingshitan reservoir based on wavelet analysis
		LU Yujing，GUO Chunqing
		This paper presents a study of the rainfall changes at the Qingshitan reservoir (rainfall station) of Guilin using the observed data of annual rainfall and flood season rainfall, focusing on multi-time scale analysis of dry-wet alternating time scale and change point behaviors by Moelet wavelet. The results show that the annual rainfall was characterized by prominent cycles of roughly 8 years and 24 years and it tends to increase in the next three years. And the flood season rainfall took two major periods of roughly 8 years and 26 years and it will be decreasing in the next three years. The method gives an effective identification of the changes in rainfall, but its influencing factors should be quantitatively evaluated further.
		2015 Vol. 34 (6): 14-20 [Abstract] ( 165 ) PDF (737 KB) ( 284 )

	21	Study on optimal water supply operation model of pluriennial regulation reservoir groups with external water resource
		SUN Wanguang, YANG Binbin, XU Yanbin, XU Xiaowu, LI Chengzhen
		This paper develops an optimal water supply operation model of pluriennial regulation reservoir groups with external water resources, which has been applied in a case study of a reservoir groups water diversion system for one city. By integrating water diversion and water supply into an optimization system, this model reduces the system scale and dimensionality and implements global optimization with a dynamic programming method. We describe a concept of year-end water storage target of pluriennial regulation reservoir and an optimization method for determination of its value, so as to combine the factors of annual operation and pluriennial regulation. Relative to conventional operation, the optimized operation reduces water transfer by a sum of 8.44×106m3 and total waste water by 2.99×106m3. Thus, the storage of reservoir groups is increased substantially at the end of the year, and water supply capacity in low water season also increased, effectively reducing the degree and extent of water supply interruption. Comparison shows that the model and optimization method can improve water supply security in low water season while fully exploiting the potential of water resources and reducing the cost of water supply.
		2015 Vol. 34 (6): 21-27 [Abstract] ( 183 ) PDF (388 KB) ( 351 )

	28	Study on multi-objective prediction model for year-end water level of carryover storage reservoir
		WANG Jinlong，HUANG Weibin，MA Guangwen，BAI Yu，WANG Zhance，WANG Yuhua
		Based on the relationship between annual power generation and year-end energy storage, a multi-objective prediction model for the optimal year-end water level of carryover storage reservoir is developed, which gives a full consideration to maximizing the hydro energy and least output of the hydro plant at such a reservoir. The model was validated with the case of Longyangxia reservoir on the upper Yellow, and the essence in obtaining its optimal year-end level was revealed through analysis of the impacts of water inflow and year-start level on this optimal level. The operation results simulated by the model are further compared with the prototype operation case of this reservoir from 1990 to 2012. This shows that since 2006 it has run at a higher level than before 2006, which improves its own benefits and indicates that the multi-objective model is reasonable and feasible.
		2015 Vol. 34 (6): 28-34 [Abstract] ( 218 ) PDF (371 KB) ( 296 )

	35	Study on optimization method of priority control line on reservoir operation curve
		WANG Shiwu，WANG Helong，WEN Jinhua
		Water resources system has various functions that influence or restrict each other. To coordinate the conflicts between different beneficial goals of a reservoir, we developed a method how to add a line of priority control to reservoir operation curve and applied it in a case study of Hunanzhen cascade reservoirs. In the application, the control line was used to direct the reservoir manager's decision to put the priority on water supply or power generation to reconcile the conflicts between the water demands by Hunanzhen and the reservoirs. A mathematical model for optimization of reservoir operation under priority line control was developed and solved with an immune evolutionary particle swarm optimization. The results show that it can improve the comprehensive benefits via reasonable priority decision in reconciling various water demand conflicts.
		2015 Vol. 34 (6): 35-40 [Abstract] ( 172 ) PDF (774 KB) ( 274 )

	41	Extraction of reservoir optimal operation rules based on clustering analysis
		JI Changming，SHI Ping，HUANG Suting
		Clustering analysis and Gini coefficient are applied for the first time to analysis of reservoir optimal operation rules. The present results show that this method is feasible. This paper also presents a distance Gini coefficient that is more effective in reservoir operation analysis than traditional similarity index. Cascade hydropower stations in the middle Jinsha reach should be operated by the optimal operation rules that adjust along with the high and low inflow changes, and these rules are unique combinations of three basic elements, guaranteed capability, increasing flow, and no-surplus flow, in a certain way that varies with the high and low inflow condition every year.
		2015 Vol. 34 (6): 41-48 [Abstract] ( 156 ) PDF (2229 KB) ( 379 )

	49	Joint water supply simulation of multiple local water sources and inter-basin water diversion
		YANG Liu，WANG Ni，XIE Jiancang，ZHU Jiwei，JIANG Rengui
		This study developed a joint water supply system to improve the joint scheduling compensation of water transfer and water supply from local water resources for the Shaanxi Han river-to-Wei river water transfer (HWWT) project and the Shaanxi Heihe river diversion (HRWT) project. This system includes a structure diagram of the water resources system and a water dispatch simulation model. It simulates and calculates various supply schemes that were designed for two types of HWWT water allocation and a variety of HRWT water supply orders. Using this system, we optimized the supply schemes for 2020 and 2030, defining a monthly water supply reliability to verify the simulations. The results show that a better scheme is to allocate HWWT water in demand assignment by the order of water supply to city users. And in 2020 the water supply guarantee rate would reach 95% for comprehensive city life use while over 90% for industrial enterprises and ecological environment. In 2030, all the guarantee rates would exceed 90%. At the operation stage of HWWT project, the HRWT project will supply to the city with its surplus water after meeting the demands by river base flow and reservoir irrigation. This significantly improves the reservoir irrigation guarantee rates up to a level of higher than 75% in 2020 and 2030.
		2015 Vol. 34 (6): 49-56 [Abstract] ( 225 ) PDF (388 KB) ( 391 )

	57	Newsboy model of water resources allocation and its application in Dongjiang basin
		HE Yanhu，CHEN Xiaohong，LIN Kairong，Wu Xiaoqing, Gui Faliang
		In view of the proposition of total water use control, this paper introduces the concepts of benefit and compensation from economics into water resources allocation. Based on the newsboy model, a multi-objective water allocation system that takes a total water use control quota as the core state variable of water allocation is constructed and applied in the Dongjiang river basin. The principle of decomposition and coordination for large-scale systems was adopted to solve the model, and it provided water distribution results in the schemes of high and low quotas for domestic water use control in 2020. The results show that in these schemes, the water volumes allocated to various sectors had minor differences but the net benefits at the low quota are higher than those at the high quota. And during an extreme dry year, the water deficit ratio exceeded 50%. This newsboy model coordinates well the beneficial relationship of available water resources, water demand and water use control quota versus water allocation. The improvement on net benefits of each water use sector reflects the rationality of water allocation and confirms the feasibility of this model.
		2015 Vol. 34 (6): 57-64 [Abstract] ( 159 ) PDF (443 KB) ( 446 )

	65	Energy estimation of tidal power station and its software design and application
		SHU Quanying，LU Xiaoyan，ZHENG Xiongwei
		Energy estimation of a tidal power station is a core subject in its planning and design stage. This paper presents an estimation of the theoretical tidal energy output from a tidal power station by the water balance principle and a method for calculation of long-series hydro energy regulation of the station in different operating conditions under its specific modes of development and exploration. A user-friendly software was developed to calculate annual energy output and applied at the planning and design stage of the Wenzhou Ou’fei tidal power station. The results of application to this engineering case show that the software has a satisfactory accuracy and application value.
		2015 Vol. 34 (6): 65-70 [Abstract] ( 143 ) PDF (2666 KB) ( 322 )

	71	Urban area watershed flood simulation with hydraulic model：A case study of Qinghe river in Beijing
		PAN Xingyao, LI Qijun, CHEN Jiangang, LU Li, Meng Fanchen
		Watershed flood simulation for urban areas is important for river safety and flood control, but it is a difficult issue due to its complicated factors. Based on a one-dimensional MIKE11 model, we integrated on the model platform the processes of runoff generation in impervious areas, multi water projects control, regional drainage, and tributaries confluence, and constructed a coupled modeling system of Qinghe watershed flood in the urban area of Beijing. The river and floodgates hydraulic parameters are validated with design flood volume and its corresponding water level data of 20 year and 50 year return periods. And the floodgates operating rules are validated with the water level data from the storm and flood events in July 21 in 2012. The simulations shown a good agreement with the water level, total flood volume, and peak value monitored at eight floodgates. Application of this model to different scenarios of design storms shows that low water level corresponds to relative high flood volume and the river can undertake flood volume of 20 year rainfall return period. The riverbank in the middle reach between the floodgates of Qinghe and Yangfang is the most serious area for flood control. For the rainfall return periods from 1 year to 20 year, the ratio of final volume of storm water into the river over the river storage capacity is in the range from 33.5% to 54%. This study would supply a guide to flood control and storm water utilization assessment in the watershed of urban area.
		2015 Vol. 34 (6): 71-80 [Abstract] ( 197 ) PDF (2583 KB) ( 583 )

	81	Study on water right trade model for the water market of Bayannur city
		WANG Lizhen， HUANG Yuefei, WANG Guangqian, ZHAO Jianshi
		The complex adaptive system theory was introduced to generalize production water agents into three levels in a water right trade model. The agents' activity was simplified with four major behaviors: water use, water buying, water selling and water saving, and they were determined by an economics agent equation. Maximum regional economic benefit is the target of optimization. This model was applied to the water market in Bayannur city that is facing a water shortage problem. The results indicate that it is effective in analysis of the potential water which can be traded and it supplies a decision support to determination and adjustment on water price in water market for water resource management sectors.
		2015 Vol. 34 (6): 81-87 [Abstract] ( 125 ) PDF (328 KB) ( 304 )

	88	Applicability of logistic model for phenology detection based on remote sensing data
		LIU Hui，HU Hongchang，HU Heping，TIAN Fuqiang
		Phenology change as a result of climate change has dramatic influence on terrestrial ecosystem and hydrological cycle. Phenology detection models based on remote sensing data are important tools for regional phenological study. The study area of this paper is the Inner Mongolia grassland with focuse on the grassland phenology. We used the wavelet analysis method and data from remote sensing and meteorological stations to investigate the applicability of logistic model for phenology detection under different climate conditions. The results indicate that in areas with the drought index HAI larger than 3 the life circle of grass is disturbed, and the assumption of the logistic model will not be satisfied anymore, so under this climate condition it will not be reasonable to use logistic model for phenology detection; in areas where HAI is between 2 and 3, the vegetation growth may be disturbed by drought sometimes, so pre-test should be carried out when applying the logistic model.
		2015 Vol. 34 (6): 88-94 [Abstract] ( 214 ) PDF (3893 KB) ( 353 )

	95	Impact of climate change on future low flow in Jinhua river basin
		MA Chong1，ZHU Guantian2，GAO Xichao1，ZHANG Xujie1，XU Yueping
		Low flow is an important component of hydrology. It is inextricably bound to our life and economic activity. But little attention is paid to it compared with flood. Impact analysis of climate change and human activities on water resources is a hot issue of current research. This paper projects the precipitation, temperature and flow of Jinhua river basin during the next 30 years. The main method is Statistical Down Scaling model and Sacramento model. Two low-flow indices 7Q10 and 30Q10 are computed from observed and simulated flows. The results show that 7Q10 and 30Q10 both increase under the two scenarios.
		2015 Vol. 34 (6): 95-99 [Abstract] ( 202 ) PDF (539 KB) ( 333 )

	100	Hydrological connectivity between main river channel and floodplain at McCarran Ranch wetland, USA
		CHEN Xiaobing, CHEN Li，ZHAO Jian
		Hydrological exchange between a river and its floodplain plays a critical role in maintaining river ecosystem. Herein, a state-of-art hydrodynamic model (AdH) was applied in modeling flood events in the Truckee River at lower McCarran ranch in Nevada. The hydrologic connectivity between main channel and floodplains is examined in details through flow field characteristics, trans-boundary flux, and particle tracing analysis. Results reveal substantial spatial variations of main channel-floodplain flux exchanges in both magnitude and direction. During a flood peak, up to 60% of its total discharge flows into floodplain, or about 1.52 times as much as that in main channel. Trans-boundary flux can be affected by both the river morphology and discharge magnitude. Particle-tracing shows that a large majority of particles (>85%) passed over the boundaries for at least one time, revealing a strong flux exchange at the interface of main channel and floodplains during flood events. The particle trajectory and residence time distribution also reflected a spatial and temporal heterogeneity of hydraulic interactions in a main channel-floodplain system.
		2015 Vol. 34 (6): 100-106 [Abstract] ( 180 ) PDF (1579 KB) ( 375 )

	107	Study on mean velocity over steps of stepped spillways
		YANG Jijian，LIU Hansheng，DAI Shubing，WEN Mingyi
		Stepped spillways have attracted great interests of researchers to date. This paper describes a concept of relative velocity over a stepped spillway and compares its velocities with those over a corresponding smooth spillway to explore in depth the mean velocity and its related hydraulic performances. We have conducted an experiment testing four different chute slopes of 26.57°, 32.01°, 38.66°, and 51.3° at a step height range of 0.5m ~ 2.0m, and examined the relationships of cross-sectional mean velocity over steps and relative velocity versus flow path length on the stepped section, unit width discharge, step height, chute slope, and relative energy dissipation rate. The results show that the mean velocity over the steps of a stepped spillway has a complicated nonlinear relationship with flow length, unit discharge, and the dissipation rate, while relative velocity varies linearly with these parameters. Generally, relative velocity much depends on unit discharge, size of stepped spillways, and chute slope, increasing with step height and chute slope and decreasing with unit discharge. It also takes a good linear relationship with the dissipation rate. At a fixed relative dissipation rate, an increase in unit discharge causes a decrease in relative velocity, which means a lower flow resistance.
		2015 Vol. 34 (6): 107-111 [Abstract] ( 150 ) PDF (632 KB) ( 325 )

	112	Study on relative Froude number over steps of stepped spillways
		YANG Jijian，LIU Hansheng，WEN Mingyi，CAO Changchong，AN Mengxiong
		Froude number is an key parameter in open channel flows, but its systematic research of flows over stepped spillways is lacking. This paper presents a relative Froude number concept for stepped spillways by comparing their Froude numbers with those of the corresponding smooth chutes. We have conducted experimental tests of fifteen sets on a model stepped spillway using four different channel slopes (26.57°, 32.01°, 38.66° and 51.3°) and different step heights (0.5~2.0 m). Analysis of the test data shows that for a smooth-bottom chute, the Froude number of its non-uniform flow section takes good linear relations with flow length, unit width discharge, step height, slope, and relative energy dissipation head, while for a stepped spillway, the relations are complicated and difficult to apply. This experiment proves the necessity of stepped spillway analysis adopting relative Froude number.
		2015 Vol. 34 (6): 112-116 [Abstract] ( 174 ) PDF (653 KB) ( 273 )

	117	Experimental study on effect of surface roughness on overland flow velocity
		SHI Mingxin， WU Faqi，TIAN Guocheng
		Surface roughness is a key factor of overland flow velocity and its variation. This study systemically discusses variations of average overland flow velocity V, surface roughness d and discharge q with slope gradient S using data of fixed-bed model tests. Flow velocity was measured on a flume with adjustable surface roughness (d≤10mm), unit discharge (0.04~0.24 L?s-1?m-1), and slope gradient (2°~12°). Results show that when surface roughness increases, the water flow consumes more energy in overcoming resistance and flow velocity is decreased exponentially. Different roughness leads to different main control factors of overland flow velocity. At lower roughness (0≤d≤2.5mm), roughness, discharge and gradient are dominant factors that contribute 19.8%, 44.8% and 27.8% of the flow velocity variance respectively, while at higher roughness (2.5
		2015 Vol. 34 (6): 117-124 [Abstract] ( 148 ) PDF (556 KB) ( 344 )

	125	Study on kinetic energy correction factors of gate arch-shaped sections of pressured tunnel
		HU Ming，ZHANG Qingqing
		Kinetic energy correction factor of gate arch-shaped sections of pressured tunnel has been studied by using FLUENT and MATLAB in combination with physical model tests. The results show three pairs of transverse circulation in the steady turbulence flow in such a tunnel. And when Reynolds number is no less than 4.0×103, this factor takes a value comparable to that for circular section. It decreases with an increasing Reynolds number and hydraulic radius and shows a difference between tunnels of standard and nonstandard gate arch shapes.
		2015 Vol. 34 (6): 125-130 [Abstract] ( 145 ) PDF (1073 KB) ( 423 )

	131	Flow structure in upper part of Three Gorges reservoir
		ZHOU Yinjun，JIN Zhongwu，XU Tao
		Since the Three Gorges reservoir (TGR) started to run, the non-uniform flow with backwater characteristics in its upper part has remarkably affected sediment transport and flood travelling. Specific observed data were analyzed to reveal the behaviors of three-dimensional velocity and turbulence intensity in this reservoir region, particularly the characteristics of vertical distribution. Results show that in the region, vertical profiles of longitudinal velocities generally follow the log-law, the distribution of transverse flows is controlled by riverbed forms, and vertical components are considerable and largely in downward direction. Turbulence intensities of all the three components are distributed uniformly on all the cross sections along the flow, but vertical turbulences tend to increase gradually along the flow. Such features of vertical flows and turbulences in the backwater region of non-uniform flow are remarkably different from those in uniform flow, and hence it has brought about significant changes in sediment motions, especially the vertical profiles of suspended sediment concentration in the reservoir area.
		2015 Vol. 34 (6): 131-137 [Abstract] ( 153 ) PDF (1897 KB) ( 337 )

	138	Calculation of head loss over stepped spillways with relative specific energy
		WEN Mingyi，LIU Hansheng，AN Mengxiong，YANG Jijian
		Specific energy is a foremost hydraulic parameter of stepped spillways, a measure of kinematic energy of moving water. This paper compares specific energies between stepped spillway and smooth spillway, and works out a new concept—relative specific energy that describes the difference of head loss between the two spillways. Model tests on skimming flows of 21 sets were conducted using a spillway slope range of 26.6°~48° and a step height range of 0.5~2.0 m, focusing on the variations of specific energy and relative specific energy with the length of flow path, unit discharge, step height, and bottom slope. The results indicate that the specific energy varies with these parameters in a manner too complicated to apply practically while the relative specific energy that is independent of discharge, varies linearly with the length of flow path. Step height has a great influence on the relative specific energy that increases with it and spillway slope. The results prove the necessity of stepped spillway analysis adopting relative specific energy and its advantage in practical applications. An empirical formula for calculation of water head loss is given.
		2015 Vol. 34 (6): 138-142 [Abstract] ( 141 ) PDF (390 KB) ( 278 )

	143	Study of riverbed resistance calculation for the lower Yellow River. A review
		LI Lingyun，FAN Beilin，WANG Jiasheng，CAO Huiqun
		Determination of riverbed resistance is an essential issue in river dynamics. The lower Yellow River, as a river with the highest sediment concentration in the world, has rapid and frequent changes in its channel carrying fine sediment particles. Due to its specific flow and sediment conditions, it is always very difficult to estimate its riverbed resistance. A large body of its previous studies focused on such calculations but the achievements are still quite embarrassed because of the lack of field survey data about its riverbed resistance and the complexity of its fluvial processes. This paper analyzes the factors of riverbed resistance of the lower Yellow channel and summarizes the previous results of riverbed resistance calculation, and makes suggestions of potential directions in further research.
		2015 Vol. 34 (6): 143-148 [Abstract] ( 155 ) PDF (336 KB) ( 310 )

	149	Experimental study on temperature of water released from intakes of different types
		GAO Xueping，REN Qingyu
		Stop log gate intake, multi-level orifice intake, and floating point intake, are often used as engineering measures on thermally-stratified reservoirs to control the temperature of irrigation water for crop growth. Previous studies on temperature of water released from such intakes, particularly comparative studies of different types of intakes, are lacking. This study has conducted experimental tests to model the thermal stratification of a reservoir and compare these three intakes. Results show that the released temperature of stop log gate intake is higher than that of the other two intakes and of all the intakes, the released temperature are closely related with their submergence but nearly irrelevant to their flow rate. This study would lie a basis for selection, operation, and management of reservoir water intakes.
		2015 Vol. 34 (6): 149-153 [Abstract] ( 171 ) PDF (991 KB) ( 399 )

	154	Study on crack resistance and crack-width control of concrete spiral case of hydropower station in river channel
		SHI Changzheng，WU Hegao，JIN Jian，CHEN Xiaodong
		Combined with an in-stream hydropower house, cracking characteristics of reinforced concrete spiral case were analyzed by a nonlinear finite element method, and effects of steel fiber-reinforced concrete and epoxy mortar on concrete crack control are discussed. The results indicate that water head endured by this spiral case is not high, but owing to the large size of its orifices, cracks are very likely to appear in the intersections of its roof, floor and sidewall and on the generator pier. For a large-scale concrete spiral case, high strength concrete or steel fiber-reinforced concrete can reduce the extent of its concrete damage, while they have little effects in prevention of its cracking and they will, on the contrary, induce problems of high hydration heat and complicated construction technology. Thus, adoption of concrete with lower strength is more rational if combined with an effective control on crack width within a certain allowable range and a measure of seepage prevention. To reduce seepage, steel liner and epoxy mortar coating on the inner wall of spiral case are effective, and for crack control, a beneficial measure is to allow the steel liner and epoxy mortar to carry a certain part of the load. During practical operation, aging and spalling of the epoxy mortar are the problems unsolved yet, so steel liner is better and reliable in terms of durability.
		2015 Vol. 34 (6): 154-159 [Abstract] ( 208 ) PDF (459 KB) ( 280 )

	160	Discussion on inverse method of elastoplastic parameters for gate arch-shaped tunnel
		LIU Naifei，LI Ning，GUO Xiaogang，WANG Qian，ZHANG Chengke
		Based on the thought of seeking problem-solving approaches in practice, an effective and simple method was previously presented which is used for back-analysis of the elastoplastic displacement of a circular tunnel. In this paper, the method is promoted to the gate arch-shaped tunnel applying the complex function theory, and rationality and uniqueness of its strength parameters are discussed. First, using the elastic solutions of deformation in such tunnels, the authors prove a conclusion that the ratio of arch vertical displacement over side-wall horizontal displacement is independent of Young's modulus, and an elastic back-analysis theory is formulated. Then, we point out that the criteria of elastic parameters from back-analysis is unreasonable since analysis values are compared with measured values at the same ratios of vaults and side walls. An improved criteria is derived by the stress release rules, and the uniqueness of strength parameters is discussed from the view of mathematics. Finally, application in a case study of an actual project verifies the applicability and reliability of the promoted back-analysis method. This study would improve the applicability of geotechnical back-analysis to actual projects.
		2015 Vol. 34 (6): 160-168 [Abstract] ( 165 ) PDF (467 KB) ( 311 )

	169	Statistical analysis of dam concrete strength parameters
		ZHANG Yanhong，HU Xiao，YANG Chen，ZHU Hongdong，JIAO Jian
		Tensile strength and compressive strength are common strength indexes of concrete. Tensile strength can be measured by direct tensile test, three point bending test, and tensile splitting strength test; and compressive strength measured by cube compressive strength test. Fully-graded large specimens and wet-screened small specimens are typical forms used in dam concrete material test. Certain statistical relationships exist between strength indexes of concrete specimens with different sizes under tests of different types. This paper summarizes static and dynamic test results of fully-graded concrete and wet-screened concrete considering concrete materials in actual dam projects, including examination on the rate effect and size effect of concrete strength and analysis on the quantitative relationships between different strength indexes. The results are compared with previous studies in literature and they would provide significant information to design of actual projects.
		2015 Vol. 34 (6): 169-175 [Abstract] ( 210 ) PDF (1010 KB) ( 391 )

	176	Blade opening adjustment for hydraulic turbines based on substitute angle measurement
		LIU Zhong，RAO Hongde，HUANG Zhuqing，ZHONG Yong2，LI Jianyong
		A method of blade opening adjustment for hydraulic turbines based on substitute angle measurement is studied and presented herein to overcome the difficulty in accurate onsite measurement of blade angle and its unfavorable effect on the adjustment. We give a definition of substitute blade angle and methods for its measurement and calculation, and determine the thickness modification of adjusting shims according to a blade opening conversion ratio and the interaction between adjacent blades. This method was applied in situ to a bulb turbine and its blade openings were successfully adjusted. The results show that it improves the uniformity of blade openings and the synchronism of blade angles effectively, so as to better the hydraulic performance of turbines and their efficiency and operation stability.
		2015 Vol. 34 (6): 176-181 [Abstract] ( 136 ) PDF (439 KB) ( 325 )

	182	Analysis of wavelet packet energy spectrum and power spectrum and its application to fault diagnosis of hydropower units
		AN Zhoupeng，XIAO Zhihuai，CHEN Yufan，SUN Zhaohui，TANG Weidong
		Wavelet packet analysis overcomes the shortcoming of wavelet analysis in poor resolution of high frequency band, thus providing a more accurate decomposition of signals. Basis on this analysis, a method for signal feature extraction is described for fault diagnosis of hydropower units, which combines wavelet packet energy spectrum with power spectrum analysis. Extraction and analysis of the in-situ test data and vibration fault signal at a hydropower station shows that this extraction method is accurate and efficient. It is a method of high application value and would lie a basis for accurate unit fault diagnosis.
		2015 Vol. 34 (6): 182-190 [Abstract] ( 292 ) PDF (1304 KB) ( 385 )

	191	Intelligent recognition of axis orbits with fish-based algorithms and neural networks with mentors
		LI Qiang，WANG Wenbin，LIU Xue
		A new identification and classification of unit failures by computer intelligence is realized by using the Canny operator and Hu invariant moments in the image discipline instead of human eyes to identify axis orbit, and applying artificial fish streamline redundant data and PNN fault classification. This paper proves that this method has a higher recognition accuracy and efficiency than the traditional neural network.
		2015 Vol. 34 (6): 191-196 [Abstract] ( 177 ) PDF (417 KB) ( 304 )

	197	Study of hydropower units fault diagnosis based on Bayesian network Noisy Or model
		HU Yongjian，XIAO Zhihuai，ZHOU Yunfei，SUN Zhaohui
		A fault diagnosis system of hydropower units is developed using a Bayesian network to consider complicated system structure and uncertain factors in fault diagnosis. This system adopts a Noisy Or model to overcome the shortcomings of the network in large numbers of probabilities and difficulty in determining their values. Taking the characteristic nodes as binary nodes, it uses experts’ knowledge determining the probability at each node and calculates the influence of random combinations of multiple nodes on the outcome, thus determining the possibility of occurrence of a certain fault. The simulations indicate that the number of conditional probabilities required by this new model is decreased from 2n to 2n, and thus it significantly reduces the data demand and raises the time efficiency of hydropower units fault diagnosis.
		2015 Vol. 34 (6): 197-203 [Abstract] ( 233 ) PDF (771 KB) ( 507 )

	204	Risk analysis of project construction period based on construction schedule
		LI Zongkun, ZHANG Yadong, SONG Haojing, GUAN Hongyan
		This paper describes a risk analysis method dividing project construction period into several major phases and each phase into several time spans based on the construction schedule and project features. By calculating the risk degree of construction items and allocating them to each phase and time span, we obtain three indicators, i.e. overall risk degree, average risk degree, and key projects, for each phase and time span to control the risk characteristics of the project. Example analysis shows that the method is effective and feasible.
		2015 Vol. 34 (6): 204-212 [Abstract] ( 149 ) PDF (478 KB) ( 284 )