Abstract:The reservoirs(Xiluodu, Xiangjiaba, Zipingpu, Pubugou, and Tingzikou)in the upper Yangtze River were considered as the object of study. A nonlinear safety degree strategy for the joint flood control system of the multi-reservoirs in the upper Yangtze River was proposed, based on which a flood storage capacity optimization distribution model for multi-reservoirs was constructed and an in-depth discussion for the flood control effect of the nonlinear safety degree strategy was conducted. The results show that compared with linear safety degree strategy of multi-reservoirs, the flood control capacity of Xiluodu reservoir can be less consumed by increasing the usage of the flood control capacity in other reservoirs by the nonlinear strategy in the condition that the flood control effect of the downstream is not deteriorated. The application of the nonlinear safety degree strategy can relatively balance the flood storage capacity allocation of the reservoirs, make the reservoirs share the flood risk of the flood control areas, give full play to the flood control benefits of the reservoirs, and ensure the stable and safe operation of the multi-reservoir system.

Abstract:Aiming at the complex problems of water resources in Beijing-Tianjin-Hebei region, an overall regulation and control idea based on the theory of virtuous circulation of water resources is proposed, which includes the smooth circulation of natural water resources and the cooperative equilibrium of social water resources circulation. Coping strategies are put forward in five aspects, including nature-enriched water regulation, combination of concentrated and sporadic sewage treatment, unified regulation, water consumption management, and synergetic utilization of water market. The present study is aimed at achieving virtuous circulation to support sustainable utilization of water resources and green development.

Abstract:Mega water control projects constructed in the main river basins in China can be influenced by a lot of uncertainties, such as natural environments, engineering structures and scheduling measures during operation. The benefit of water control projects under the constraint of safety operation is taken as the starting point, risks and opportunities originated from the joint regulation and control of the mega projects made up of cascade water control projects are emphasized. Related research results of water conservancy and hydropower engineering from both home and aboard are compared and the need for scientific research on joint control and safe operation of mega water control projects is proposed. Advances in the mechanisms of safety risk identification, joint operation and multi-objective benefit optimization of mega water control projects are reviewed, based on which a framework for regulation technology systems of mega water control projects is proposed. This paper gives the development direction of the integrated regulation and control technology for mega water control projects considering flood control, power generation, water supply, navigation, ecology, and shipping with multi-dimensional safety.

Abstract:In order to comprehensively understand the current status of global hydropower development, to analyze the development potential of hydropower markets in various countries, and to guide hydropower enterprises to explore the international market, the world is divided into six regions, including North America, South America, Africa, Europe, Central and South Asia, East Asia and the Pacific Rim. The current status of hydropower development in various regions of the world, as well as the corresponding status and development goals in key countries are elaborated. Based on the water resources and the development situation, the exploring potential of the global hydropower market is analyzed. The results show that the total installed capacity of hydropower in the world continues to increase but the annual increment shows a downward trend. The hydropower development potential in Africa, South Asia and Southeast Asia is relatively large. In terms of technology development, the countries such as Indonesia, Peru, DR Congo, Tajikistan, Nepal, Angola, Myanmar and Bolivia, etc. , have broad prospects for future hydropower markets.

Abstract:In order to determine the process and characteristics of channel geometry adjustments of the Tarim River, the morphological evolution features and influencing factors were analyzed based on the measured flow and sediment data as well as the mainstream cross-sectional profiles from 2005 to 2013. The results show that the channel geometry in the middle and upper reaches shrank gradually from 2005 to 2009, with a decreasing trend of the bankfull area. The fluvial erosion intensity during flood seasons was enhanced from 2010 to 2013, resulting in a lateral adjustment for the bankfull channel geometry in the braided reach characterized with wider and shallower cross-sections. The adjustment of the transition reach was relatively stable. Variation trend of the fluvial erosion intensity during flood seasons in the meandering reach was similar to that in the braided reach, and the cross-sections developed to be narrower and deeper with slight bankfull width variation. From 2009 to 2011, the longitudinal channel slope in the braided reach and the transition reach decreased by 1. 7% and 3. 0%, respectively, resulting in a flat river bed slope. However, it increased by 1. 6% in the meandering reach with little fluvial erosion. Fluvial erosion intensity can better respond to the channel geometry variation, which can be used to predict erosion and deposition of the bankfull channel. In addition, the stability of the river bank soil is poor and the river bank can be easily decomposed by the action of the near shore water flow, which accelerates the adjustment process to some extent.

Abstract:In this study, a combined hydraulic cavitation device composed of a triangular multi-orifice plate and a Venturi Pipe developed by the Hydraulics Laboratory of Zhejiang University of Technology, was used to sterilize the pathogenic microorganisms in the raw water samples taken from the Shengli River in Hangzhou with different volume ratios. Escherichia coli and the total colony count were chosen as the indicator bacteria of the pathogenic microorganisms. The effects of diffusion angles of the Venturi tube diffusion section, number of orifices of the triangular multi-orifice plate, arrangement of the orifices, volume ratio of the raw water and the number of cavitation on the killing rates of pathogenic microorganisms were studied by the agar plate method. The experimental results show that choosing an appropriate diffusion angle and the raw water volume ratio, increasing the orifice number, using staggered orifice layout, and lowing the cavitation number can considerably increase the killing rates of the total colony count and Escherichia coli.

Abstract:To accurately simulate the hydrodynamic pressure on a gravity dam face during an earthquake, a computing method considering both the flexibility of dam body and reservoir bottom is proposed based on the seamless coupling theory of finite element method and scaled boundary finite element method. By using the scaled boundary finite element method, semi-infinite impounded water can be modeled with high efficiency and accuracy with only discretization of the interface of the reservoir and the dam. In addition, water compressibility and the effect of absorption from reservoir bottom can be conveniently considered. Finite element method is employed to discretize the dam body and the dynamic response of the dam-reservoir system can be solved by the hydrodynamic pressure on the dam face. Numerical examples show that the hydrodynamic pressure calculated by the proposed method agrees well with that in the literature. The hydrodynamic pressure on a gravity dam face can be reduced by dam flexibility and it decreases with a decreased reflection coefficient of the reservoir bottom.

Abstract:Freeze-thaw action and chloride corrosion both have influences on the service life of reinforced concrete structures under northern marine environment. Based on the Fick’s second law, a model for chloride ion migration within concrete, in which the effect of time, temperature, humidity, chlorine binding capacity and the freeze-thaw damage effect had been taken into account, was established in this paper. The model was used to predict the corrosion life for the reinforced concrete piers of the Qingdao Bay Bridge. The results show that rebars inside concrete members have an obvious blocking effect on chloride ion migration. Chloride ions are likely to accumulate on the surface of the steel bar near the protective layer while concentration retardation appears on the surface of the steel bar far away from the protective layer. The peak chloride concentration in the corner region is higher than that in the non-corner region of a concrete member, and the peak values rise with the erosion time. The distribution of chloride concentration around the rebar in the inner corner of the member varies with the erosion time. At the beginning of the erosion, the peak chloride concentration occurs on the surface of the rebar perpendicular to the eroded surface, and then, it turns to appear at the diagonal of the two eroded surfaces. Compared the results in the non-salt freeze-thaw environment, the corrosion life of the concrete structure is dramatically reduced after a freeze-thaw cycle in salt environment, and the distinction of the corrosion life of the concrete component between the corner and non-corner areas also significantly increases.

Abstract:Since the existing methods of water level forecasting in the downstream of a hydropower station have a larger computational error, Gezhouba Hydropower Station was taken as a research object to establish a novel method for downstream water level variation forecasting during the non-abandoning water period. Based on the BP neural network and the hydropower station monitoring data, the downstream water level forecasting with high accuracy was realized, which can satisfy the needs of real-time scheduling. Compared with the methods of water level-discharge relationship and the empirical formula for unsteady flows, the present forecasting method has the following advantages: (1)It does not use the storage outflow data to calculate the water level, and the influence of the outflow calculation error can be avoided; (2)The hysteretic nature effects of the downstream water level variation is considered during the model construction process, so the forecast accuracy during the hump modulation periods can be greatly improved; (3)It can forecast the downstream water level changing process directly with stable calculation results and higher calculation accuracy, which can significantly improve the forecast accuracy under large peak shaving operating conditions of Gezhouba Hydropower Station during the non-abandoning water period.

Abstract:An in situ measurement device for sediment critical shear stress in the intertidal zone was developed to accurately obtain the parameters of sediment incipient motion and to reduce perturbation to the undisturbed soil. The inner flow field and the bed shear stress of the device were simulated using the software Fluent. The optimal speed ratio of the inner cylinder and outer cylinder for the most uniform bed shear stress was put forward. The correlations between the rotating speed and the bed shear stress was established and the influence of the device size on the optimal speed ratio was explored. It is found that higher bed shear stress can be obtained when the inner cylinder, outer cylinder and the shear ring rotate in the same direction. A device with an inner cylinder’s radius of 310 mm and an outer cylinder’s radius of 410 mm operating in a water depth of 260 mm was taken as an example. When the inner cylinder and outer cylinder rotate in the same direction without a shear ring, the most uniform bed shear stress distributes in the annular area with a distance of 0. 33~0. 38 m from the axis, and the optimal speed ratio is 3∶1. When the inner cylinder, outer cylinder and the shear ring rotate in the same direction, the most uniform bed shear stress distributes in the annular area with a distance of 0. 33~0. 40 m from the axis and the optimal speed ratio is 3∶1∶3. There is a quadratic function relation between the bed shear stress and the rotating speed of the outer cylinder.

Abstract:Due to the complexity of the flow pattern in the upstream and downstream of the combined sluice-pump hub, reasonable selection for arrangement types is required to reduce the adverse effects. Taking the Zhaojiagou East Combined Sluice-Pump Hub in Shanghai as an example, comparison and selection for different arrangement types of a combined sluice-pump hub in plain river network regions were analyzed in the aspect of hydrodynamic conditions based on two-dimensional numerical simulation of the flow patterns near the project. The results show that, symmetric arrangements are superior to asymmetric ones in terms of the overall flow patterns in the upstream and downstream of the hub. In terms of the velocity distribution during flood drainage, the sluice-pump-sluice arrangement is superior to the pump-sluice-pump arrangement in the symmetric arrangement types, because it is more beneficial to reduce the scour downstream the sluice. From the perspective of river navigation conditions during water diversion, the influence of sluice-pump-sluice arrangement on the navigable cross-flow of the inland river is obviously reduced compared with the pump-sluice-pump arrangement. The allowable discharge of the sluice-pump-sluice arrangement is obviously larger than that of the pump-sluice-pump arrangement under the same restrictions on the navigable cross-flow of the inland river.

Abstract:In view of the face cracking of a CFRD during construction in cold regions, the structural deformation, temperature variation, hydration temperature rise and its own shrinkage were analyzed with an actual project based on prototype monitoring. It is found that the highest value of the hydration temperature rise and the maximum temperature difference in the later cooling is the main factor affecting the temperature difference of cumulative cooling. When the temperature difference of the cumulative cooling is larger, the temperature stress may exceed the tensile strength of the panel concrete, causing panel cracking. Suggestions for avoiding temperature cracks were put forward for construction projects with larger annual temperature difference and higher hydration temperature during the concrete pouring period, such as optimizing the concrete mix ratio, optimizing the construction process and improving concrete crack resistance.

Abstract:Aiming at the problems of strong nonlinearity, complexity of diagnosing and eliminating abnormal values, and poor ability to resist gross errors of traditional monitoring models for the analysis of dam deformation monitoring data, a dam deformation monitoring model based on robust estimate extreme learning machine(M-ELM)was established. It combines the theory of robust estimation which has strong roughness tolerance with the extreme learning machine which has strong ability in dealing with nonlinear problems. The network number of the hidden layers was determined by tests and a fourth power loss function was built. A weighted least square method was used to calculate the output weights, and the fitting and prediction of the original monitoring data was carried out. The monitoring data of a certain dam deformation was taken as an example for modeling analysis. The mean square error and the mean absolute percentage error reflecting the prediction accuracy, and the median absolute deviation representing the model robustness were taken as the evaluation indexes. The results show that each index of the dam deformation monitoring model based on robust estimate extreme learning machine is superior to other models.

Abstract:Aiming at the requirements of the real-time process evaluation for the on-site compaction degree of roller-compacted concrete(RCC), prediction parameters such as the moisture content, the shear wave velocity on the surface of compacted fresh concrete, aggregate gradation, the ratio of cementitious material and sand are selected to construct a prediction model based on GA-BP neural network. The effectiveness of the proposed real-time evaluation method was validated by an on-site application case. The results show that compared with BP neural network models, GA-BP model has a higher prediction accuracy with a smaller range of deviation fluctuation and it can predict the real-time compaction degree of RCC accurately and effectively with higher stability. GA-BP model is more sensitive to the lower limit value of the compaction degree. For samples with the compaction degree ranging from 93% to 96%, the average error of the GA-BP model is only 0. 08% and the maximum one is only 0. 17%, revealing very high prediction accuracy.

Abstract:In order to apply the viscoelastic artificial boundary condition in the computation of a layered foundation model, the formulas for calculating the amplitude ratio of different types of seismic waves are derived in this paper based on the wave theory. The traveling wave effect is considered by the delay method and the free field of the layered foundation is solved, based on which the equivalent load considering the reflection and transmission of seismic waves is obtained. Finally, a viscoelastic artificial boundary model considering layered foundation is established. The vertical incidence of an SV wave is taken as an example to verify the formula and the proposed numerical model is then used in the dynamic calculation of a gravity dam. The results show that the model established in this paper satisfies the accuracy requirement of engineering seismic analysis and it can solve the problem of structural dynamic analysis considering soil-structure interaction when seismic waves spread vertically on the layered foundation.