Abstract:To study the hydraulic flow state of a lateral outlet box culvert of a rainwater pumping station in Shanghai, a physical model test method was used to analyze the hydraulic flow state characteristics inside the culvert. Aiming at the founded problems, a combined rectification measure consisting of short diversion piers, bottom sills and composite beams was put forward. The test results show that the water flow inside the outlet box culvert is poorly diffused, resulting in uneven flow distribution at the outlet of the box culvert, centered main flow, and weak outflow on both sides of the outlet. After the combined rectification measures, under the comprehensive rectification action of the short diversion pier, the bottom sill and the composite beam, the flow distribution of each hole of the outlet box culvert is significantly homogenized, which effectively improves the outflow uniformity, and solves the existed problems of the flow state.

Abstract:To study the flow loss characteristics of a shaft tubular pump, the FBM-CC turbulence model was used to conduct unsteady calculations on the internal flow field of the shaft tubular pump based on the URANS method. The entropy production theory was used to quantitatively analyze the flow loss characteristics of the shaft tubular pump under different flow conditions. The result shows that the FBM-CC turbulence model can effectively predict the hydraulic performance of the shaft tubular pump, which is in good agreement with the experimental results. The flow loss of the shaft tubular pump is in the order of the impeller, outlet channel, guide vane and inlet channel. The main source of impeller energy loss is turbulent dissipation, accounting for up to 92%. Vortex and flow separation can lead to local high entropy production areas. Large number of vortices exist at the impeller hub in critical stall conditions and the flow at the rim is relatively stable. The deep stall conditions are affected by the tip leakage flow, and flow separation occurs at the impeller inlet rim. As the flow rate is further reduced, the streamline of the inlet channel is affected and separation vortices appear at the leading edge of the blade.

Abstract:To have a deep understanding of the concepts related to water conservation, the representative concepts of water conservation, water conservation function and water conservation capacity were sorted out and differentiated based on reviewing of relevant researches both at home and abroad and the definitions with clear connotations and denotation were put forward. Water conservation is a process and phenomenon in which the ecosystem intercepts precipitation, stores water, regulates runoff, purifies water quality and maintains ecology. Water conservation function has both narrow and broad sense. In the narrow sense, water conservation function is holding precipitation, runoff regulation and influencing precipitation. In the generalized sense, water conservation includes soil and water conservation, degradation reduction of vegetation, underlying surface conditions improvement, biodiversity and ecological environment protection functions such as regulating climate, as well as the special features in the narrow sense. Water conservation capacity is the quantitative embodiment of water conservation function. The water conservation capacity calculation is the calculation of water quantity in the narrow sense while in the broad sense, it should be the comprehensive calculation of water quantity, water quality and some ecological indexes. Finally, taking the source region of the Yellow River as an example, different calculation results and application of water conservation capacity are introduced.

Abstract:Based on the specific regional and water conditions of the Beijing-Tianjin-Hebei region, the rigid constraints of water resources were strengthened, and the concept and framework of the adaptation of water resources and industrial structure optimization was clarified. The designing principle of the adaptation scheme and its corresponding objective function were constructed, the constraints of the adaptation scheme designing were determined, and the multi-objective optimization configuration model was integrated and established. The diagnosis criteria of the adaptation scheme were constructed, embedded in the multi-objective optimization configuration model, and the overall optimal allocation was realized. The results show that the overall objective optimization function value reaches 0. 99 in the Beijing-Tianjin-Hebei region, verifying the feasibility of the adaptation framework and adaptation model. From 2000 to 2019, the relative adaptative degree of water resources allocation and economic development of Beijing-Tianjin, Beijing-Hebei and Tianjin-Hebei are in the range of ［0. 80, 1. 20］, ［0. 80, 1. 00］ and ［0. 70, 1. 20］ respectively. In 2019, the relative adaptative degree of water resources allocation and economic development of Beijing-Tianjin, Beijing-Hebei and Tianjin-Hebei are 0. 878, 0. 975 and 1. 110 respectively, which is in the diagnostic threshold interval ［0. 8, 1. 2］.

Abstract:To improve the accuracy of flow discharge at monitoring sections influenced by hydraulic structures and the performance of HADCP-based discharge monitoring system, the apparatus depth, drop height and other relevant factors were comprehensively considered. A multilinear regression model solved by least-square method was built to calculate the cross-sectional mean velocity. In order to improve the low accuracy of flow discharge in low-flow conditions, the relationship of the measured mean velocity and the velocity cell of the H-ADCP which has a high correlation with the measured-mean velocity was considered using the LASSO regression model in machine learning for parameter estimation in low-flow conditions. The approach was applied in the Baihe Hydrological Station and the results meet the requirements of specification. The research results provide references for the H-ADCP velocity derivation scheme design in the Baihe Hydrological Station and other hydrological stations affected by hydraulic projects.

Abstract:The basin upstream the Fulaerji section of the Nenjiang River was selected as the study area. Statistical method and model method were used to evaluate the impact of land use change and the Nierji Reservoir operation on the runoff variation, and the change trend of runoff under the combined influence of the two factors was analyzed. The results show that, the land use change in the basin before and after the construction of the Nierji Reservoir is not obvious, while the runoff change in the downstream is obvious, and the reservoir has a greater impact on the runoff change. SWAT model is suitable for runoff simulation in the study area. The influence of reservoir operation and land use change on the runoff change is 92. 86% and 7. 14% respectively. Under the same rainfall and reservoir operation conditions, the annual runoff can be first decreased and then increased by the land use change from 1990 to 2020, and the reservoir operation has a significant impact on the annual runoff distribution.

Abstract:The transformation of the regulation mode of the lower Yellow River was comprehensively reviewed. The new strategy of basin zoning treatment in the lower Yellow River was introduced. This mode divides the broad beach between the main channel and the levee into ecological resettlement area, high-efficiency ecological agricultural area, ecological wetland and areas for other functions. The water and sediment regulation objectives of flood control with graded standards, sediment deposition in partitioned zones, and free exchange of channel runoff and sediment are expected to be achieved by means of sediment and river dredging for the tender beach, lower beach and high beach. It is therefore believed the mode is technically sound and advanced, and the application of this model in the lower reaches of the Yellow River is bound to achieve a win-win situation of river regulation and people benefit, and it can promote the high-quality development of the economic belt along the Yellow River and the construction of water ecological civilization.

Abstract:Numerical simulations for open-channel combining flows with equal channel width were performed with a three-dimensional numerical model with RSM and VOF method. The results were analyzed for 21 cases, in which seven junction angles and three discharge ratios were combined. The separation zone is defined with the isoline method of longitudinal velocity. The sizes and the three-dimensional shape of the separation zone were analyzed. Meanwhile, the streamwise distribution of the secondary-current intensity downstream the junction was summarized in terms of the sectional vorticity. The results reveal that as the discharge ratio increases or the junction angle decreases, the horizontal sizes of the separation zone decrease, and its shape becomes long and narrow. The averaged depth of separation zone decreases while the discharge ratio or the junction angle increases. The intensity of the secondary currents downstream of the junction gradually reduces while the discharge ratio increases. The impact of the junction angle is significant near the junction and gradually reduces along the streamwise direction.

Abstract:In order to reduce the probability of fish injury and improve the fish passing capability for water turbines, an evaluation method for fish passing capability was established based on the fish damage mechanism. Combined with a three-dimensional hydrodynamic distribution characteristic of the turbine passage and the hydrodynamic damage threshold of the fish, the evaluation method was proposed for fish passing ability. The key operation parameters for Kaplan turbines were discussed based on the study case in which the juvenile of the four major Chinese carps in the Yangtze River passing through the ZZ500 turbine passage in the Gezhouba Hydropower Station. The results show that the operating head, flow rate, guide vane opening, blade angle and power output of the Kaplan turbine all have certain influence on the fish passing capability, and the key influence parameters are operating head and guide vane opening. When the turbine operates under the conditions of low head, large flow, large output and high efficiency, the probability of fish injury caused by the spatial hydrodynamic characteristics of the flow passage is small, and the fish passing capacity of the turbine passage is the best.

Abstract:On the basis of summarizing and elaborating the similarities, differences, and applicability of one-dimensional unsteady convection-heat transfer model theory, the hyporheic zone of the Walker River Basin in the United States was chosen as a case study, of which the VFLUX 2 program was carried out to calculate and compare the differences between different one-dimensional analytical models for quantifying the vertical hyporheic exchange fluxes in the hyporheic zone. The optimal analytical model for solving the vertical hyporheic exchange flux was verified and determined, and the spatial-temporal variation of the hyporheic exchange flux at different depths in the hyporheic zone was investigated. The advantages and disadvantages of the analytical model and the focus of future work using the heat tracer method were discussed from the perspective of theoretical analysis. The results show that the amplitude method can reasonably reflect the interaction between surface water and groundwater in the hyporheic zone compared with the phase and amplitude-phase combination methods, which is an ideal model to quantify the vertical hyporheic exchange flux. The hyporheic exchange flux at different depths of the hyporheic zone is significantly different. The hyporheic exchange is frequent in the shallow, and the exchange effect is suppressed with the depth increase. In the future, a more reasonable and suitable numerical model for quantifying the hyporheic exchange flux using the heat tracer method for complex engineering conditions should be considered.

Abstract:Aiming at the problem of solid calcium decomposition under seepage erosion of concrete dams, based on the analysis model of cement-based material advection-diffusion-driven leaching model, the calculation method for concrete dam leaching quality was proposed. Taking the RCC gravity dam of the Shimantan Reservoir as an example, the distribution of the leached quality of different dam sections was studied. The calculation results show that the simulation results are in good agreement with the monitoring data, which verifies the correctness of the method. The leached parts of the dam cementitious materials are concentrated at the bottom of the concrete face slabs, the upstream side of the key-wall and the connection part of the curtain and the key-wall. The existence of the drainage pipes can affect the leaching rate of the cementitious materials. After 100 years of leaching duration, the mass percents of the cementitious materials of the curtain, key-wall, panel and dam body are 5. 5%, 5. 6%, 4. 5% and 1. 2% respectively, which shows that the advection-diffusion-driven leaching has a great impact on the curtain and the key-wall. In the operation of the project, it is necessary to strengthen the leaching monitoring of curtain and key-wall.

Abstract:Aiming at the problem that the randomness and complexity of inverted siphons cannot be comprehensively reflected by safety evaluation at the present stage, and the membership function of evaluation index based on analytical formula tends to be conservative, AHP method was used to construct the analytic hierarchy process system including multi-dimensional factors, in which the membership function of evaluation index was constructed by using cloud model theory. A comprehensive evaluation method based on AHP-cloud model with on-site monitoring and detection information fusion was then proposed, which was applied to the safety evaluation of an inverted siphon at the Huangshui River branch in the Middle Route of the South-to-North Water Transfer Project. The results show that the inverted siphon safety evaluation method based on AHP-cloud model is reasonable and feasible. The evaluation results can reflect the comprehensive safety state of the inverted siphon during operation, which can provide reference for its safety management.

Abstract:Aiming at the “abnormal” phenomenon that the penetrating crack opening of a gravity arch dam crest along the arch direction increases when the temperature rises and decreases when the temperature falls,a three-dimensional finite element method was used to simulate the force transmission characteristics of longitudinal cracks on the dam crest.By introducing two-node element method, the opening degree variation of longitudinal cracks was simulated under two working conditions of temperature rise and temperature drop, and the physical causes of abnormal variation of cracks were analyzed based on the measured data of cracks.The analysis results show that the arc length of the upstream side arch ring is longer than that of the downstream side arch ring. When the temperature rises, the deformation of the upstream side arch is larger than that of the downstream side arch, which leads to the increase of the longitudinal crack opening at the riverbed.When the temperature drops, the deformation of the upstream side arch ring downstream is larger than that of the downstream side arch ring downstream, which leads to the phenomenon that the longitudinal crack opening of the dam crest at the riverbed is smaller or even in a closed state.

Abstract:Missing data of concrete dam deformation can cause difficulty and even misjudgment to the analysis of dam service status. Based on the theory of clustering and panel data, a novel method to deal with the missing data of concrete dam deformation is proposed, in which the common and specific influencing factors of dam deformation are considered. Compared with traditional methods, this method can more comprehensively reflect the influence of load and non-load factors on dam structural performance, and is more effectively for processing the missing data of dam deformation. The application of missing data processing in a concrete double curvature arch dam shows that the predicted residual error is lower than the error limit of arch dam radial deformation stipulated in the Code for Dam Safety Monitoring (SL.601-2013), indicating that it has high precision and can effectively process the missing data of safety monitoring.

Abstract:Based on a typical gently inclined red-bed slope along the Desui expressway, an indoor slope model was established according to the geological analysis and similarity theory. The excavation test was used to simulate the actual engineering slope cutting, and the deformation evolution process of the slope was studied. The results show that the longitudinal red-bed slope with a gentle dip angle of 20° presents a typical tensile-slip failure under the condition of slope cutting. The displacement of the slope increases with the cutting grades, and the horizontal displacement is higher than the vertical displacement. The displacement near the slope surface is larger than the other parts of the slope. The slope deformation is mainly composed of unloading deformation in the cutting slope stage and creep deformation in the stationary stage, and the unloading creates the basic condition for the development of creep deformation. From the uncut slope to the weak mudstone stage, the magnitude and rate of unloading deformation are higher than the creep deformation stage. After the cut slope to the weak mudstone interlayer, the unloading deformation of the slope is lower than the creep deformation. The stress near the cutting slope surface is obviously disturbed while the stress in the middle and trailing edge of the slope is less disturbed by cutting. The overall stress decreases inside the slope, indicating gradual stress release with the slope cutting process. 

Abstract:To solve the problem of insufficient non-linear fitting that may exist in the inversion of geo-stress field using the multiple linear regression method, a mathematical model based on the extreme gradient boosting (XGBoost) algorithm is introduced, which can correct the inversion results of the multiple linear regression, and a more accurate initial geo-stress field can be obtained. Application to actual engineering cases show that, through the comparison and analysis of the corrected inversion value and the measured value of the ground stress measuring points, the fitting error of the test set is reduced by about 60%, and the stability is high, which effectively improves the accuracy of the inversion results.

Abstract:To explore the freeze-thaw properties of aeolian sand improved by cement and silt, a series of freeze-thaw cycle tests were carried out on aeolian sands improved by 5% content of cement mixed with different contents of silt soils. The strength attenuation and mass-volume variation rules of the modified aeolian sands were studied. The results show that the compressive strength and peak strain of the improved aeolian sand are positively correlated with silt content after two freeze-thaw cycles. With the increase of freeze-thaw cycles, the resistance to compression and deformation of modified aeolian sands decrease obviously. The aeolian sand improved by 15% content of silt soils has the most stable structure. In addition, with the increase of freeze-thaw cycles, the volume change rates of modified aeolian sands with single cement mixture and silt cement mixture both present a decreasing tendency. The sample treated with 5% cement and 15% silt shows the lowest decreasing amplitude, and the mass loss rate of the sample improved with 5% cement increases linearly. The coefficient of strength attenuation can directly and effectively reflect the strength change rule of the improved aeolian sands after freeze-thaw cycles.

Abstract:To study the dry shrinkage of cement stabilized soil (CSS) and its size effect, two types of clay from the engineering field of a key water-control project in Mengcheng were tested for indoor dry shrinkage performance. The shrinkage of CSS of different cement content and under various curing time was measured and the size effect on shrinkage was compared. The results show that, the shrinkage of CSS increases with extension of drying time, and tends to be stable after 14 days. As the content of cement increases, dry shrinkage decreases. The extension of curing time is beneficial to dry shrinkage performance with limited effects. There is a positive correlation between dry shrinkage and mass loss rate. The size of specimen has little effect on dry shrinkage with non-significant size effect. 