Abstract:Aiming at the problems such as the difficulty of continuous simulation data transfer of multi-hazard coupling effect in hydropower engineering and the lack of full-process sequential simulation tools, a hybrid simulation method of dynamic disaster chain transfer coupled with multiple numerical simulation tools and physics engine was proposed by considering the key nodes and parameters in the process of disaster chain transfer. The method adopts numerical simulation tools to obtain physical fields and damage patterns such as structural strength and deformation, maps the physical field variables and structural damage patterns into the physics engine through secondary development. The block movement, reservoir underflow, and flood evolution process after structural damage based on computational fluid dynamics and physics engine simulation methods in a mixed sequence are then simulated to realize the whole process of simulation for the transfer of the extreme dynamic disaster chain. The validation results of an extreme explosion damage accident in a gravity dam hub show that the method overcomes the limitations of single numerical simulation tool, realizes the integrated simulation preview from the structural response of the primary disaster to the whole process of the secondary disaster evolution, and achieves the more desirable effect in terms of precision and efficiency on the scale of engineering application.

Abstract:The seepage field of embankment after piping was calculated by numerical simulation, and the variation law of pore water pressure at different depths and horizontal positions in the embankment was studied. The influence of piping locations and piping channel sizes on pore water pressure after piping was analyzed, and the idea of rapid identification of embankment piping based on the variation characteristics of pore water pressure was put forward. The reasonable layout area of measuring equipment of pore water pressure for embankment piping monitoring was obtained. The results show that after piping, the pore water pressure at different positions of the embankment decreases to a certain extent. The pore water pressure at the bottom of the piping channel and within a range of 1m above decreases greatly, which can be used as the buried depth range for pore pressure measuring equipment used for monitoring the occurrence of piping. After the occurrence of piping, the changes in pore water pressure at the same distance from the piping channel on the same horizontal plane are basically identical. The longer the distance between the piping channel and the embankment foot, the smaller the reduction value and reduction percentage of pore water pressure around the piping channel. With the increase of the diameter of the piping channel, the reduction value and percentage of pore water pressure around the piping channel increase significantly after piping.

Abstract:In order to optimize the hydraulic characteristics of a large-slope vertical slot fishway pool, a three-dimensional hydrodynamic numerical model was constructed on the basis of physical model validation. Numerical simulation was carried out to analyze the hydraulic distributions of the pool with or without the vertical slot sill and with different installation heights of the vertical slot sill, considering five types of large slope gradients. The results demonstrate that the pool’s maximum flow velocity and average turbulent kinetic energy are successfully reduced by setting the sill at the vertical slot. For a 1/20 slope, the maximum flow velocity of the pool is reduced by 10.16% to 14.84%, the average turbulent kinetic energy is dropped by 21.88% to 42.19%, and the mainstream flow velocity decays at a rate of 61.24% to 61.82%. A Ω-shape continuous flow with small flow velocity and low turbulence is formed in the pool.The installation heights of the vertical slot sill can affect the velocity distribution in the water depth above and below the sill, but has no significant effect on the distribution regimes of velocity, turbulence kinetic energy and strain rate in the water depth above and below the sill.

Abstract:Aiming at the problem of excessive negative pressure in a dropshaft caused by the inflow water tongue, the structure optimization design for the original dropshaft model was carried out. The realizable k-ε turbulence model and VOF two-phase flow model were used to study the flow regime and air pressure distribution in the original model and the optimized one under different inflow rates. A water tongue impact model was established to determine the installation elevation of the ventilation pipe bottom in the optimized model. The influence of the ventilation pipe position relative to the intake pipe on the air pressure distribution was discussed. The results show that the falling water tongue near the intake pipe blocks the normal air flow in the well, and large air recirculation zones are formed above the water tongue. The space below the water tongue cannot be replenished in time, and the sudden increase of negative pressure near the intake pipe is obvious. The established water tongue impact model can accurately predict the impact point position at the water tongue end, and the maximum error is within 10%. The installation elevation of the ventilation pipe bottom is 2.31 m, and the top elevation is slightly higher than the upper wall of the water inlet pipe. The optimized shaft model can reduce the pressure difference in the negative pressure surge zone by at least 70%, and when the angle between the ventilation pipe and the horizontal center extension line of the inlet pipe is 30°, the optimized dropshaft model has the best effect.

Abstract:In order to promote the application of aeration technology in alleviating the influence of supersaturated dissolved oxygen (DO),the release tests of supersaturated DO under non-aeration and aeration conditions were carried out. The impact of aeration on the dissipation process of supersaturated DO and its related laws were studied, and the release process and release coefficient of supersaturated DO under different aeration conditions were analyzed. The experimental results show that the time required for DO saturation to dissipate from about 170% to about 105% under aeration conditions is less than 11 min, while the time required under no aeration conditions is at least 240 min, indicating that aeration can significantly promote the dissipation of supersaturated DO. The supersaturated DO release coefficient increases with the increase of aeration rate, decreases with the increase of aeration depth, and shows a strong negative correlation power function relationship with aeration aperture. According to the release law of supersaturated DO, the quantitative relationship between release coefficient and aeration conditions was established. The quantitative relationship between release coefficient and aeration conditions, model size and fluid parameters was established by dimensional analysis. By comprehensively analyzing the two quantitative relationships, it can be concluded that the latter has smaller root mean square error and average absolute error, higher correlation coefficients, and easier parameter acquisition, which shows that the latter is more applicable in practice.

Abstract:In order to increase the power output of tidal current energy, a new type of turbine blades and a Venturi-type duct were designed. Through in-door flume test, the roles of Venturi-type duct on increasing low velocity and rectifying oblique of the inflow were experimentally studied. The effects of different free stream drift angles, length-diameter ratios and area ratios of Venturi-type duct on the rotational speed of turbine were analyzed. Calculation formulas of the loads (thrust force, torque and radial force) exerted on the tidal current turbine were theoretically deduced. Changes in the relationship between the acting loads with free stream drift angles, length-diameter ratios and area ratios of the Venturi-type duct were analyzed combined with the experimental results. The results show that the Venturi-type duct can considerably increase the rotational speed of turbine, with the amplitude depending on the length-diameter ratio and area ratio of the guide duct. Under different drift angles, the maximum rotational speed occurs at the length-diameter ratios between 1.5 and 2.0, which means the guide duct should not be too long or too short. The rotational speed increases with the area ratio, and can reach the maximum value at the drift angle of 30°. The torque and radial force increase with the area ratio, but critical values exist for different length-diameter ratios and drift angles. The thrust force decreases with the drift angles. Compared with the case of free stream, the Venturi-type duct can not only increase the tidal current velocity, but also can rectify oblique inflow, thus enhancing the power inputted into the tidal current turbine.

Abstract:The ABAQUS numerical software was used to analyze the bearing characteristics of batter piles under the coupling of horizontal load H and torque T , the variation characteristics of pile internal force and the friction on pile-soil interface. The changes in characteristics of batter piles were also compared to those of straight piles. The impact of pile-soil stiffness ratio, eccentricity of loading and length diameter ratio of the pile shaft on the torsional bearing capacity of batter piles was discussed. The results indicate that when subjected to the coupling the horizontal load and torque, batter pile is torsionally damaged. The torsional bearing capacity of batter piles is greater than that of straight piles. The torsional bearing capacity of batter piles is related to the inclination angle of the pile body. The pile-soil stiffness ratio, eccentricity of loading and length diameter ratio of the pile shaft also have a certain impact on the torsional bearing capacity of batter piles, and the length diameter ratio of the pile shaft has a greater impact.

Abstract:In order to study the shear strength of fiber-water soluble polymer composite and the failure mechanism of sand, the shear strength characteristics of improved sand under different polymer contents and fiber contents were studied through a series of direct shear tests and numerical tests.The shear strength, parameters and failure characteristics of improved sand were analyzed. The test results show that the shear strength characteristics of the improved sand increase significantly with the polymer content and fiber content. The incorporation of water-soluble polymers and fibers increases the cohesion and has little fluence on the internal friction angle of the improved sand. When the fiber content is 0.8% and the water-soluble polymer content increases from 1% to 4%, the shear strength of the improved sand increases by 55.58.kPa. When the water-soluble polymer content is 4% and the fiber content increases from 0.2% to 0.8%, the cohesion increases by 32.69.kPa. The increase in polymer and fiber contents promotes the bonding between the components of the composite sandy soil, enhances the overall integrity of the improved sandy soil, and improves the stability of the soil.

Abstract:In order to enhance the seismic stability of sand and gravel in the dam body of the Karabelli Water Conservancy Hub Project in Xinjiang, the prototype model test area was established based on the construction parameters of the original dam. The cemented sand and gravel were formed by cement grouting, and indoor shear characteristics of cement cemented sand and gravel were studied. The results show that the sand and gravel material form a “dense-skeleton” structure after rolling. By cement grouting, the shear parameters such as internal friction angle and cohesion are greatly improved. The strength of cement, the bond strength between cement and gravel, and the normal stress play a major role in the shear strength of cemented sand and gravel. Under shear stress, the internal micro cracks gradually develop into penetrating cracks, causing the failure of cement cemented sand and gravel. Due to the interlocking effect and shear dilatancy effect between particles, the residual cohesion of cement grouting cemented sand gravel does not significantly decrease.

Abstract:Taking typical soil dikes in the Dongting Lake area as the object, the coupling calculation of seepage, temperature and stress was carried out by using FLAC3D software.The temporal-spatial evolution characteristics of the seepage field, temperature field and damage field of dikes and foundations were analyzed under the conditions of seepage and structural failure. The internal relationships between temperature and seepage and between temperature and structural failure were investigated. The results show that the evolution of dike foot and surface temperature in the lower reaches reveals the characteristics of stage change during the process of local penetration failure and even the whole structure failure. The change characteristics of surface temperature can be used as an indirect index to predict or judge the degree of seepage damage and structural damage in dams.

Abstract:Aiming at the abnormal leakage problem of the north sluice of the Shilianghe Reservoir, based on a long series of field synchronous prototype observation tests, the temperature field around the secondary stilling basin of the north sluice was drawn.The similarity and dissimilarity characteristics of mass concentrations of hydrochemical elements such as Ca2+ and Cl^- were analyzed. The main source and leakage path of the secondary stilling basin of the north sluice were identified, and feasible reinforcement measures such as building underground continuous cut-off wall, using high-pressure jet grouting pile to intercept seepage, and repairing the bottom filter of the secondary stilling basin were put forward, which made the reinforcement project be constructed accurately, blocking the leakage passage successfully and great economic benefits were achieved. The results of the Shilianghe Reservoir dam leakage detection show that the combined tracing method of temperature field tracing, natural water chemical tracing and ICP chemical tracing can accurately trace the source of leakage, it can be promoted and applied in dam leakage detection.

Abstract:Many unfavorable factors such as system failure and sensor aging can often lead to deviation or even lack of monitoring data. In the present study, a bi-directional CNN-BiLSTM-Attention missing data interpolation model for intermediate missing data during dam monitoring based on the deep learning framework was constructed from the perspective of time series. The characteristics of the convolution neural network and long-term and short-term memory neural network were combined to extract time features in the model. The attention mechanism was introduced to optimize the interpolation process. The forward and backward interpolation results were fused by the weights decreasing according to time steps. A concrete gravity dam was selected to verify the effectiveness of the proposed model by interpolating the long-series missing data of dam monitoring. The results indicate that bidirectional fusion interpolation can effectively overcome the cumulative error of interpolation time steps for long-series missing data, and this deep learning framework has higher interpolation accuracy compared to other interpolation models.

Abstract:Aiming at the problems of strong nonlinearity, difficulty in identifying and eliminating gross errors in concrete dam deformation monitoring data, an approach of gross error identification and a dam safety monitoring model for deformation monitoring data of concrete dams are proposed based on the improved IGGⅢ-ELM method, which combines the advantages of the improved IGGⅢ method with the good robustness to outliers, the extreme learning machine (ELM) method with high efficiency in predicting data sequences and strong ability to handle nonlinear problems and the incremental ELM method with rapid optimal network structure seeking, the IGGⅢ-ELM method is improved by using a four-segment weight function containing two harmonic coefficients, making the first derivative of the weight function smooth everywhere, and enhancing the availability of information in the mutation range of the weight function. In the study case, the processing result of the improved IGGⅢ-ELM method was compared with the IGGⅢ-ELM method, DBSCAN clustering algorithm, Romanovsky criterion and Pauta criterion. The results show that the gross error identification and prediction method of concrete dam deformation monitoring data based on the improved IGGⅢ-ELM method has a gross error identification rate, stronger generalization ability and better prediction effect than the other four methods.

Abstract:In order to explore a feasible scheme for improving the water quality of a plain river network in Weitang Town of Suzhou, a hydrodynamic and water quality coupling model of the river network was constructed based on Delft3D. Using Delft3D-FLOW, the spatiotemporal characteristics of the hydrodynamics in the river channels of the town during October of 2021 were simulated, and the discharges of the water pump stations and water thrusters were demonstrated. Using the Delft3D-WAQ module and tanking CODMn, NH3-N, and TP as the main evaluation indicators, the rationality of the scale of bypass purification facilities was demonstrated. The simulation results show that the hydrodynamic results of the model are relatively ideal and the live water effect is good. The discharge of the No.1 Pump Station in the Laozhen section is determined to be 1.0 m³/s, and the in duced discharge of the live water thrusters in the Pearl Lake section is 0.4 m³/s in each group.The water quality simulation results are relatively ideal. After being treated with Pearl Lake and Diamond Bypass purification facilities with a scale of 20 000 m³/d, the water quality of the rivers in the town can reach to Level IV of the Environmental Quality Standard for Surface Water (GB.3838—2002), with significant improvement effect.

Abstract:Using Laoxiqiao Village in Yangshahu Town as an example, the MIKE model was used to analyze the health degree of a rainwater pipe network system in Xiangyin County of Yueyang City during rainstorm interference. The model was calibrated and validated using the measured water depth of severe waterlogging points during a rainfall process. Design rainfall with a duration of 2-hour and return periods of 1, 3, 5, 10, and 20 years was simulated, and the 3-year 2-hour rainfall process was studied in detail. A health evaluation index system for rainwater pipe networks considering four comprehensive indicators including drainage capacity, pipe network structure, environmental factors and social factors with 15 sub-indicators was constructed. The results show that the comprehensive scores for drainage capacity, pipe network structure, environmental factor and social factor are 0.48, 0.78, 1 and 0.66, respectively. The overall health degree is 0.54, indicating a poor comprehensive health level. The greater the recurrence period, the deeper the water depth, but the arrival time of the maximum water depth is not affected by the recurrence period. The locations with greater risk of waterlogging and deeper water are located near pipelines with lower health degree.

Abstract:In order to optimize the allocation of water resources of the Henan Section of the Yangtze River to Huaihe River Water Diversion Project, the optimal allocation model of water resources with the maximum economic benefit, the minimum water shortage and the minimum pollutant emission as the objective function was constructed. The improved third generation non-dominated sorting genetic algorithm (A-NSGA-Ⅲ) was used to solve the model, and four optimal allocation schemes of water resources focusing on different objectives were selected. The results show that the water diversion from the Yangtze River to the Huaihe River can greatly alleviate the contradiction between supply and demand in the water-receiving area. The water shortage rate can be reduced to 10.43% and 5.47 % in 2030 and 2040, respectively. The water supply structure can also be optimized and the ecological environment can be improved. The fourth scheme with the largest coupling economic-social-ecological environment coordination degree is the optimal scheme. Under the fourth scheme, the proportion of groundwater supply in the planning years can be decreased by to 53.32% and 46.59%. The A-NSGA-Ⅲalgorithm has good applicability in solving multi-objective and high-dimensional water resources allocation problem, which can provide reference for the formulation of water resources allocation scheme in the Henan Section of the Yangtze River to Huaihe River Water Diversion Project.

Abstract:In order to study the sensitivity of WRF-Hydro model parameters in the Hexi Inland River Basin, the area above the Jiutiaoling Hydrological Station in the Xiying River Basin was taken as the research area.The WRF-Hydro model was driven by global forecast system (GFS) data from 2015 to 2018 in standalone mode. The latin-hypercube one-factor-at-a-time (LH-OAT) method was used to analyze the six main parameters of the WRF-Hydro model and was carried out with confluence grids of different evaluation objectives and different spatial resolutions. The sensitivity index of each parameter was quantitatively calculated and classified. Combined with a typical flood, the specific influence of each parameter on flood hydrograph was analyzed. The results show that the Manning roughness multiplier (MANNFAC) is an extremely sensitive parameter. The infiltration coefficient (REFKDT), the soil saturated hydraulic conductivity (REFDK), and the deep hydraulic conductivity (slope) are sensitive parameters. The surface roughness multiplier (OVROUGHRTFAC) is a general sensitive parameter, and the surface water holding depth (RETDEPRTFAC) is an insensitive parameter. The sensitivity of each parameter is not static, and the parameter sensitivity can be affected by the evaluation index, and a certain degree of change exists. With the variation of the spatial resolution of the confluence calculation grid, the global sensitivity of each parameter can also change slightly, but the global sensitivity level of the parameter does not change. MANNFAC has the best adjustment effect on peak time, REFKDT and REFDK have significant adjustment effect on flood volume and peak, and slope can adjust the shape of flood hydrograph well.

Abstract:In order to explore the evolution law of the hydrological and meteorological elements in the Xijiang River Basin and to study the potential impact of extreme rainfall on flood runoff, based on the hydrological and meteorological data of the basin from 1956 to 2019, the evolution laws of extreme rainfall, annual runoff, and annual maximum 1-day flood volume were comprehensively analyzed using methods such as trend analysis and mutation test. The Pearson correlation coefficient and double cumulative curve method were used to evaluate the relationship between extreme rainfall and annual runoff. The impact of extreme rainfall on flood disaster losses was discussed. The results show that compared with the upper reaches of the high-altitude area, the changes of extreme rainfall in the middle and lower reaches of the Xijiang River Basin are more obvious, showing increasing frequency and intensity of the extreme rainfall. Rx1day,R99p, and SDⅡ show a significant upward trend, with extreme rainfall indicators mostly experiencing sudden changes in 1992. The average annual runoff and maximum annual flood do not significantly increase, and there exist two mutation points. PRCPTOT, R25, R10, and R95p are significantly correlated with runoff, while R95p, R99p, CDD, R25 have a relatively significant impact on flood disaster indicators. After 2002, the correlation between extreme rainfall indicators and flood disaster indicators has significantly changed.