By investigating the historical meteorological data, disaster situation data and disaster bearing body information during 1951-2020, this paper establishes a risk survey database to accurately evaluate the hazard of rainstorm disaster in Changsha County of Hunan Province. Comprehensively considering the impact of multiple meteorological disaster causing factors of rainstorm disaster and inducing environment such as geology and drainage network of watershed, this paper carries out the analysis of basic characteristics of rainstorm and risk assessment of disaster, and forms a risk assessment model. Geological disasters in Changsha County mainly occur in the northeast of Changsha County. The urban waterlogging disaster mainly affects the county seat and the surrounding areas with high urbanization. Mountain torrents mainly affect the central and northern areas of Changsha County. The risk of rainstorm disaster in Changsha County tends to weaken from the southeast and northeast to the middle. Generally speaking, the risk of rainstorm in the whole county is not high, only Kaihui Town, Gaoqiao Town and Huanghua town are high-risk, and rainstorm events are easy to cause secondary disasters in these three towns. There are two relatively high value centers in the county, which are located in Huanghua town and Jiangbei town in the southeast and Kaihui town and Gaoqiao Town in the north. The comprehensive risk level of rainstorm in Ansha Town, Guoyuan Town, Chunhua Town and urban area in the middle is low.

During the landfall of Typhoon Billis in July 2006, Wujiang River, a tributary of the Beijiang River basin, was hit by an unusual rainstorm in history, resulting in the largest flood ever recorded in the basin. Based on precipitation record and Doppler weather radar data, it is found that the "train effect" induced by a convective storm, which originated in southern Hunan and crossed the divide, is the main reason for the extreme precipitation in Wujiang River basin. The study of the convective storm activity by using GIS technology shows that the complex topography of Wujiang River basin changed the direction of the convective storm several times, which greatly prolongs the duration of the storm in Lechang city, resulting in local rainstorm and flash flood. The study also found that the Huangcen Reservoir in Qitianling Mountain area was affected by typhoon, which probably enhanced local convections. The study reveals the influence of mesoscale and miso-scale topography on typhoon rainstorm, which contribute to the prevention of typhoon-induced disasters.

In view of the differences between national, continental and global scale precipitation data sets, there are many studies, but the reliability of data sets on river basin scale is rarely considered. To this end, the maximum/minimum difference percentage method and TFPM-MK trend analysis method were used to study and evaluate the differences between 12 widely used precipitation data sets in precipitation estimation and change trends in 6 292 basins around the world. The results show that there are large differences between precipitation data sets. There are 2 469 basins with an annual average precipitation difference of more than 500 mm/a, covering an area of 4 419.6×10⁴km², mainly distributed in Greenland, Africa, Oceania and West Asia. The existing data products cannot reach an agreement on the precipitation trend of all basins, and it is difficult to provide a reasonable scientific basis for the formulation and implementation of effective policies to ensure water conservancy and power generation, domestic water supply, flood control and early warning in the basin.

As a widely used function in hydrologic frequency and flood computation, the Gamma function has many calculation methods, and the scope of application and computation accuracy also vary. In order to explore a high-precision Gamma function computation method suitable for hydrological computation, different Gamma function asymptotic expansion formulas such as Stirling series and its derived approximation formula are used for computation and analysis. Comparing the accuracy and application range of various methods, the results show that the piecewise polynomial method has the smallest truncation error and the highest accuracy; The second is the Ramanujan asymptotic expansion and the Stirling first tetranomial. The recommendatory high-precision Gamma function computation method can effectively improve the computation accuracy of hydrological results, which can provide fast and accurate results for the planning and design of various hydro projects to determine project scale and management decisions.

To analyze the potential influence of the construction and operation of the cascade junction on the hydrologic regime of four major Chinese carps spawning sites in the downstream of the Xinjiang River, 21 parameters were selected to establish the hydrological index system of fish spawning sites. The one-dimensional hydrodynamic model was adopted to analyze the hydrological regime of Daxidu spawning site before and after the construction of the cascade junction. The range of variability approach was used to analyze the hydrological changes of spawning grounds during the breeding period before and after the construction of cascade junction. The results show that the flow during the breeding period decreases after the operation of the cascading junction, which made the variation range of water flow limited in a small range. Furthermore, the number of high flow pulse decreased, which reduced the stimulation signal to spawning of four large fishes. This study quantified the impact of the construction of cascade junction in the downstream of the Xinjiang River on the spawning grounds during the breeding period, and provided scientific guidance for the design of the local hub operation scheme.

Scientific assessment of the hydrological regime is an important part of the assessment of the health of the river ecological environment. The IHA indicators were used to quantitatively evaluate the change of hydrological indicators of Gaobazhou Station during the construction period and operation period of water conservancy projects in the Qingjiang River Basin. On the basis of analyzing the change law of five different IHA indicators, the overall hydrological situation change of Qingjiang River was analyzed by selecting three different RVA methods, which include the Nemero index method, the RVA method based on the European distance method and the RVA method considering the comprehensive weight. It shows that the results of the analysis of the hydrological situation in the Qingjiang River Basin by the three methods during the construction period and the comprehensive utilization period are moderate and highly changed, respectively, and the hydrological situation change in the Qingjiang River Basin has an increasing trend. The evaluation results of the RVA method considering comprehensive weights are similar to the previous two methods and are reasonable, which can better reflect the changes in the river hydrological situation after the construction of the water conservancy project in the Qingjiang River Basin.

In order to better understand the impact of vegetation restoration on hydrological processes, the SWATMODFLOW model and dynamic HRU was coupled, and LU-SWAT-MODFLOW model was developed to accurately simulate the dynamic change of vegetation and groundwater in the lower reaches of the Bayin River Basin. The results revealed that the LAI, ET and groundwater level simulated by LU-SWAT-MODFLOW model are better; After vegetation restoration in the study area, the monthly evapotranspiration of different sub-basins increased by 0-1.5 mm, and the annual evapotranspiration increased by 0-6 mm; The average monthly groundwater recharge increased about 1.27 mm, and the average annual groundwater recharge increased 14.02 mm. The exchange of the surface water and groundwater in the study area have obvious changes in the areas where the vegetation restoration type is low-coverage grassland and bare land converted to forestland.

The expansion of cities and towns has caused a large amount of waters to be compressed, occupied or even disappeared, and the risk of floods in the region has increased sharply. This study is based on Hengyang, a typical city in midstream of Xiangjiang River. Based on expansion speed index and intensity index of Xiangjiang midstream from 2001 to 2016, the linkage relationship between the two is quantitatively analyzed, and the response of water system change under the background of urban expansion is analyzed. The results show that the urban development in midstream of Xiangjiang River can be divided into three stages. The urban expansion is characterized by a high speed and then a low intensity. During the study period, the total number of river systems showed a declining trend, and the channel morphology showed a shrinking state. The change of the structure of river systems was more severe than the change of the number. The basin with few river systems and single structure had a sharp decline. Urban expansion has a close relationship with the change of river system, and has a greater impact on the change of the number of river systems. And it is highly related to the basin with few water systems and single structure. It can be seen that human activities such as urban construction and expansion should minimize the adverse impact on such watersheds.

In order to study the effect of arrangement of non-submerged rigid vegetation on surface flow hydraulic characteristics, this paper established a hydraulic model based on the actual situation. The average vegetation was evenly arranged as the control group, the vegetation was arranged in a strip pattern and the distance between the strips increased in multiples of 1.333, 1.667, 2.000, 2.333, 2.667, while the distance within the strips decreased by 0.833, 0.667, 0.500, 0.333, 0.167 as the experimental group. The numerical simulation based on Fluent verified the effects of changes in the arrangement of vegetation with the 5% coverage (210 plants) on the water flow and hydraulic characteristics. The results show that the vegetation coverage was the same and the vegetation arrangement tended to be uniform. Under the influence of water depth, the flow rate decreased, and the Reynolds stress in the lower half of the water depth increased. The surface flow rate on the non-submerged vegetation decreased, and the turbulent flow increased. The water energy is consumed to prevent water and reduce the erosion of water surface. This study provides reference for flood control and disaster reduction.

In order to accurately judge the start and end time of snowmelt period, the upstream of the Danba basin, the main source of snowmelt runoff in Daduhe River, was taken as an example. Based on hydrometeorological data from 2009 to 2020, set pair analysis method, systematic clustering method and K-means clustering method were used to calculate the snowmelt period in the dry season (November to the next May), and the rationality of the staging results was evaluated. The division scheme of final snowmelt period in the basin was determined. The results show that the main snowmelt period is from January 11 to May 10, the preceding period is from November 1 to January 10, and the following period is from May 11 to May 31, which is the beginning period of rainfall runoff (there is still some snowmelt runoff). The research results can provide reference for the classification of snowmelt periods in high latitude areas.

The bedload sediment transport in the compound channel is affected by the presence of emergent rigid vegetation, and there were few studies available on this topic. The laboratory experiments and theoretical analysis were used to investigate the effect of emergent rigid vegetation in parallel arrangement on the threshold Shields number and the bedload transport intensity. The results show that the presence of emergent rigid vegetation in parallel arrangement increased the threshold Shields Number by 97.2%, and the bedload transport intensity reduced by more than 80%. The modified Engelund Formula that was applicable to the emergent rigid vegetation in parallel arrangement conditions was developed to calculate the bedload transport intensity. The formula was shown to have a high accuracy by applying it to the other studies.

Integrating reclaimed water into water supply system is a strategic measure to alleviate the problem of water resource shortage. Aiming at the uncertainty and stability existing in the optimal allocation of multiple water sources including reclaimed water, Monte Carlo simulation and interval two-stage robust stochastic optimization were coupled to build the optimal allocation model of multiple water sources under the condition of multiple uncertainties. The uncertainty represented by the form of interval and probability distribution in the process of water supply and water demand was effectively handled. The variable random value of water resources allocation and the recourse cost were balanced, and the system’s risk was controlled. The water resources allocation schemes were obtained under different scenarios. The improved model was applied to water supply area in Linfen Basin-Jincheng Qindan river watershed of Shanxi large water network. Based on the comprehensive analysis of regional water efficiency and water loss under different scenarios, the joint allocation scheme of multiple water sources under different utilization rates of reclaimed water was obtained, which provides a reference for decision makers to consider the optimal allocation scheme of reclaimed water under uncertain conditions.

Aiming at the evaluation of water resources security in China, combined with the characteristics that support vector machine (SVM) has good classification effect on small samples and nonlinear problems, the sparrow search algorithm (SSA) was used to optimize the penalty factor (C) and kernel function parameters (g) of the SVM. The support vector machine model optimized by the sparrow search algorithm (SSA-SVM) was used for regional water resources security assessment. A case study was carried out in a certain area of Luoyang City. The results show that the evaluation grade obtained by SSA-SVM method and T-S fuzzy neural network method are basically consistent, the SSA-SVM model has the characteristics of fast searching speed, and not easy to fall into local optimum, which can be used for regional water resources security evaluation.

The supersaturated total dissolved gas (TDG) is mainly caused by the discharge of high dam spillway, excess oxygen production of plant photosynthesis and sharp increase in water temperature, which may directly lead to fish and aquatic organisms suffering from gas bubble disease (GBD) or even death. In order to explore the measures to mitigate the adverse effects of supersaturated TDG, under different aeration conditions, the swirl mixing aeration mode has an obvious effect on the release of supersaturated TDG, its effect is slightly stronger than that of pinhole aeration method, and the aeration rate has the greatest impact on the mass transfer coefficient of supersaturated TDG, followed by the aeration depth, and the aeration diameter is the smallest. The relationship between supersaturated TDG mass transfer coefficient and aeration rate, aeration diameter and aeration depth is obtained, respectively. The average error is within ±6.25%. The research results provide a data basis for mitigating the adverse effects of supersaturated TDG.

In order to improve the water environment carrying capacity of Nanchang during the dry period, this paper constructed a water environment model at the lower end of the Ganjiang River and proposed an optimal scheduling scheme. The results show that the optimal scheduling water levels for the Ganjiang main river and its four downstream branches-the main, the north, the middle, and the south-were between the minimum ecological water level and the alert control water level, and that the scheduling time was within 1.11 days when the flow rate was less than 1 020 m³/s. Conversely, when the flow rate was greater than 1 020 m³/s, the alert control water level was the flood control limit water level. The optimal scheduling water levels of the main river and the four branches were between the minimum ecological water level and the flood control limit water level, and the scheduling time was within 4-7 d. It was suggested that each branch barrage hub should be operated close to the alert control water level to ensure that the water quality of the river control section meet the standard, and to maintained the maximum amount of water resources available in Nanchang.

Conventional and wetting triaxial experiments were carried out on coarse grained materials for dam construction with a large static and dynamic triaxial tester. The dynamic characteristics of coarse grained materials after wetting deformation were studied, and the results were compared with those of conventional triaxial dynamic experiments. The experimental results show that the dynamic characteristics of coarse grained materials are greatly affected by wetting deformation, and the dynamic performance parameters of coarse grained materials are attenuated to a certain extent. The Hardin-drnevich model parameters of the two experiments were compared and analyzed. It was found that wetting deformation had a significant effect on k₂ and λ_max, and the numerical values were attenuated, but the effects on n and k₁ were not significant.

Considering the characteristics of inversion problems of concrete face dam, including high dimensionality, complex calculation and excessive calculation time, the orthogonal experimental design was used to construct the learning sample composed of the combination of permeability coefficient and the water head of pressure measuring point. The nonlinear mapping relationship between the water head at monitoring points and permeability coefficient was established by general regression neural network (GRNN), and the particle swarm optimization (PSO) algorithm was used to search for the smoothing factor σ suitable for the specific project to improve the generalization and convergence speed of the model. The PSO-GRNN model for the inversion of the permeability coefficient of concrete face dam was established, and was applied on an engineering example. The results show that the value of permeability coefficient obtained by inversion based on the model is reasonable, and the maximum relative error between the calculated value of water head at monitoring points obtained by seepage analysis and the measured value is 3.64%, and the accuracy meets the needs of engineering.

With the continuous accumulation of dam deformation monitoring data and the continuous increase of deformation measuring points, it often takes a lot of time to predict all deformation measuring points, which is easy to cause the problem of untimely feedback. Therefore, the fuzzy C-means clustering algorithm (FCM) was introduced to partition the dam according to the similarity of deformation laws. The whale optimization algorithm (WOA) was used to optimize the parameters of long short-term memory neural network (LSTM), and a dam deformation prediction model based on FCM-WOA-LSTM was established. The measured deformation data of a concrete double-curvature arch dam was used as sample data for prediction, and the prediction results were compared with those of LSTM model and SVM model. The results show that the average absolute error (M_MAE), mean square error (M_MSE) and root mean square error (R_RMSE) of the prediction results of FCM-WOA-LSTM model are the smallest among the three models, and the three evaluation indexes of the fitting section are close to those of the prediction section, respectively. Compared with the existing models, the FCM-WOA-LSTM model has higher prediction accuracy and better applicability.

For the long-distance water supply project where the pump station pressurizes before the high point and gravity flows after the high point, when the end valve is closed in a straight line in case of power failure in an accident, a longer valve closing time is required to meet the pressure control standard, which virtually increases the scale of the protective measures and increases the investment. In order to solve this problem, a broken line valve closing rule is proposed to reduce the volume of protective measures while optimizing the pressure. The characteristic line method is used to check each scheme through FORTRAN programming, and the general rule is summarized by analyzing the influencing factors of the main parameters. The case results show that the broken line valve closing can reduce the volume of protective measures and reduce the project cost compared with the straight line valve closing within the same valve closing time under the premise of ensuring that the pressure meets the requirements.

For the pressurized water supply project of a long distance, large flow and high lift pumping station, the pump trip was simulated. Combined with the characteristics of the engineering terrain, the combined protection method of air-cushion surge chamber and one-way surge tank was proposed. And then the sensitivity analysis of the closing rule of the valve after the pump and the throttle orifice of the surge chamber was carried out according to the requirements of pipeline pressure control. The results show that the air cushion surge chamber could effectively protect the water hammer of the pump trip and the water hammer of valve shutdown caused by the rapid closure of the pump valve. The one-way surge tank solved the problem of local high pressure caused by the continuous water refill of the air cushion surge chamber, and protected the safety of the high point pipe section. The combined protection scheme could significantly reduce the volume of air cushion surge chamber and saved the engineering cost. In addition, the closing rule of the pump valve and the throttle orifice area of the air cushion surge chamber has a great impact on the water hammer pressure of the pipeline. Too fast valve closing or too large throttle orifice area will lead to the positive pressure of the pipeline exceeding the standard. Too slow valve closing or too small throttle orifice area will lead to large negative pressure in the pipeline. The specific project needs to be optimized in combination with transition process simulation. For this project, after simulation and optimization, the diameter of the throttle orifice was 0.8m, and the valve of the pump was closed by 5s straight line, and the results met the requirements of regulation guarantee calculation.

When upstream and downstream water regime changed in long-distance pressurized water delivery pipeline of cascade pump stations, it is easy to cause the change of water pressure in pipeline and hydraulic parameters such as flow velocity, and results in water hammer. In order to meet the water delivery requirements of the pipeline and ensure its safe operation under various working conditions, one-dimensional characteristics method and 3D VOF coupled methods were used to simulate. The mathematical model for transient process analysis of long-distance water delivery system of cascade pump stations was established to analyze the change and law of pipeline internal pressure and water level in outlet pool during long-distance water delivery system in Chuhe Level Ⅳ station of Simashan River Diversion Project under working conditions, such as suspending period and power losing period. It also shows that the safety of the entire pipeline system can be better guaranteed though the reasonable open-close laws of the terminal gate and side gate.

The downstream surge chamber of a certain pumped storage power station adopts impedance with upper chamber layout. The tailrace tunnel is connected with the connecting pipe through right angle bifurcated pipe and bend. The layout type is special and the water flow conditions are complex. In order to study its hydraulic characteristics, a three-dimensional flow field mathematical model of the connecting pipe at the bottom of the surge chamber was established, and the variation law of hydraulic characteristics under different diversion ratio and confluence ratio was studied. The results show that for the resistance loss of surge chamber with complex bottom flow, the three-dimensional numerical simulation can achieve better simulation effect, and the calculation results are in good agreement with the theoretical analysis results. Because the elbow at the bottom of the surge chamber, the sudden expansion and contraction between the connecting pipe and the big well will cause additional hydraulic losses, its head loss coefficient is greater than that of the conventional impedance surge chamber, and the flow coefficient is smaller than that of the separate impedance hole.

The purpose of the paper is to explore connection mechanism between interval time and pressure at draft tube inlet in successive load shedding case. Based on transient flow theory and method of characteristics, numerical simulation calculation of transition process in the successive load shedding case for pumped storage power station with layout of two turbines and one tunnel was carried out. The relationship between flow rate, running track of turbines and minimum pressure at draft tube inlet was analyzed. The result shows that there is a certain most unfavorable interval time making the time-domain asynchronous degree of first wave flow rate in two turbines maximized and the pressure at draft tube inlet is the minimum. At the same time, running track point of the first load shedding turbine is near the upper bending point in the inverse S-region of characteristic curve and running track point of the last one is near the lower bending point. The conclusion can provide a reference for calculation of extreme value of pressure at draft tube inlet in the pumped storage power station.

To address the problem of excess pressure in the water supply network system, this paper proposed to add pressure reducing valves with certain opening in the system. With the objective of minimizing the square sum of the difference between the operating water pressure at each node and the minimum service head at the node, the pressure reduction valve optimized pressure leakage control model was constructed by combining the hydraulic balance constraint of the pipe network and the node pressure constraint. The model was solved by using genetic algorithm. Taking the main water supply network of southeast coastal towns as an example, the results show that the proposed model and method are effective and feasible, and it has better optimal effectiveness.

The outlet area of river diversion tunnel in mountainous areas is characterized by large discharge per unit width, high flow velocity, deep riverbed overburden and low anti-scour flow velocity. The river bed at the outlet of the tunnel is severely scoured, and it is difficult to arrange large energy dissipation measures, so it is proposed to arrange small flip bucket at the outlet of the tunnel. On the basis of the physical model test to observe the flow pattern and river bed scouring in the outlet area of the tunnel, the numerical simulation method is used to calculate the flow field in the outlet area of the diversion tunnel, and the internal mechanism of the improvement of river bed scouring is studied. The results show that after adding a small flip bucket at the outlet of the diversion tunnel can increase the lateral diffusion of the high-speed flow out of the tunnel, reduce the unit width discharge, increase the local energy dissipation rate, and thus reduce the velocity of the river bank. The proportion of water body coming out of the tunnel with high flow velocity is obviously reduced, which makes the high-speed water flow unable to directly rush the landslide mass on the right bank, and reduces the flow velocity within the landslide mass. The width of water flow out of the tunnel increases, and the direction of water flow out of the tunnel becomes inclined upward, which weakens the impact on the landslide on the right bank, and significantly weakens the scouring of the outlet area of the diversion tunnel and the downstream river channel. This study can provide reference for engineering practice.

In order to verify and optimize the “dragon-drop-tail” layout plan of the No. 1 flood discharge tunnel in the expansion project of the Chentianhe Reservoir, a numerical calculation model for the discharge was established. The numerical feedback of cavity backwater behind the airfoil flip bucket of indoor experiment was made use of to calculate the rationality of the numerical model. The optimal objective function of the shape of the airfoil flip bucket was identified based on the principle of safety and economy. The feedback model was then used to optimize the layout of aeration devices. The research shows that results of the simulation which adopts the FAVOR and Tru-VOF methods of structured rectangular grids, the RNG κ-ε turbulence model and the numerical model of fine grid are in line with indoor experiment results in terms of cavity shape and length. The optimal values of the bucket angle α and slope rate of the bottom slope behind the airfoil flip bucket θ of the No.1 flood discharge tunnel are 10% and 20%, respectively.

Due to the lack of measured temperature on the channel surface, it is difficult to accurately simulate the channel temperature field. Considering the effect of solar thermal radiation on the temperature of the shady slope, sunny slope and bottom slab of the channel, a calculation model of channel surface temperature increase was established. The finite element software ABAQUS was used to simulate the temperature field change process of the channel and analyze the frost heave of the channel lining under the condition of three times of cooling. The results show that under the influence of solar thermal radiation, the freezing depth of the shady slope of the channel is significantly greater than that of the sunny slope and the bottom slab, the calculated freezing depth and the damage law of the lining are also in good agreement with the actual situation. During the cooling process, the concrete lining of the shady slope is more prone to frost damage than that of the sunny slope and the bottom slab, the same rule applies when calculated according to the multi-year maximum freeze depth utilization specification. The research results can provide new ideas for the temperature control and crack prevention design of channel concrete lining.

For the value of the surrounding rock parameters of the underground construction, a hybrid network approach combining backtracking search optimization algorithm (BSA) and BP neural network (BSA-BP) was proposed for the inversion study of the tunnel surrounding rock parameters. By establishing a tunnel finite element excavation model, the inversion parameters were used to calculate the displacement of the monitoring section and compare with the measured values in the field. Finally, the stability of the surrounding rock was analyzed and predicted. Compared with the GA-BP neural network, the results show that the BP neural network optimized by BSA algorithm has faster inversion speed and computational efficiency. The relative errors between the calculated displacement values and the field measured values obtained by using BSA-BP neural network inversion parameters are within 5%, indicating that the model has high inversion accuracy and is reasonable and feasible. The research results provide a new method for the inversion of underground engineering parameters.

The underground powerhouse of Henan Wuyue Pumped Storage Power Station has a complex structure of caverns. The main powerhouse has a maximum span of 26.0 m and a height of 55.1 m, which is a large underground chamber. The rock mass structural planes are developed and the strength is low. The fault F1 runs through the three powerhouse, and the safety problems are prominent. The stability of surrounding rock after excavation should be analyzed. Therefore, FLAC^3D program was used to establish the geological model. The BSA-BP neural network was used to calculate the initial in-situ stress field of the area. And then the excavation of underground powerhouse was simulated. The stress field, displacement field and plastic zone development and distribution law of surrounding rock were analyzed. The results show that the surrounding rock of underground powerhouse caverns group is basically stable. However, local deformation and failure may occur in the fault development area and at both ends of the busbar hole. The research results can provide guidance for the design and construction of the project, and provide some reference for similar projects.

The risk assessment of collapse of tunnel involves many fuzzy factors and the evaluation method is complex, which makes the evaluation system constitute a gray system and the applicability of the evaluation method is not high. It is difficult to accurately assess the risk level of tunnel landslides. Using the basic idea of gray system and vector projection principle, a set of tunnel collapse risk evaluation model based on gray vector projection method is proposed. Based on the comprehensive analysis of the influencing factors of tunnel collapse under complex stratigraphic conditions, the group analytic hierarchy process (GAHP), which takes into account the degree of difference in the views of decision makers, is used to reduce the dimensionality of the pre-selected evaluation index system. Then, according to the comprehensive decision weight coefficient, 13 preferred evaluation indicators that can fully reflect the different, representative and highly differentiated evaluation indicators of the collapse mechanism are selected to establish a tunnel collapse risk optimal evaluation index system. In addition, grey group clustering (GGC) and anti-entropy weight (AEW) are introduced to determine subjective and objective single-level sorting weights, respectively. The improved combination weighting method of game theory (ICWGT) is used to obtain the optimal comprehensive weight distribution coefficient to determine the total ranking weight of the indicator. Finally, according to this model, the risk of collapse of five groups of tunnels was evaluated by the model. The results show that the risk assessment level of tunnel collapse is highly consistent with the actual excavation. The reliability and accuracy of the model are verified.

The mechanical properties of hydraulic concrete are an important influencing factor on the stability of hydraulic engineering facilities. A fine damage intrinsic structure model considering the effect of sulfate corrosion was established using a combination of mechanical experiments and theoretical analysis. The results show that the effect of sulfate corrosion increases the damage degree of concrete after damage. With the increase of corrosion time, the compressive strength and elastic modulus show an exponential decay law, and the damage strain tends to increase. From the experimental results, the shape parameter m and scale parameter ε₀ are calculated. Besides, the mesoscopic damage constitutive model considering the effect of sulfate corrosion is solved. The reasonableness of the theoretical model for predicting the stress-strain relationship was verified by experimental data. The constitutive model proposed in this study can provide scientific reference for the accurate prediction of mechanical behavior of hydraulic concrete.

In stone column composite foundations, the Priebe parameter composite method is commonly used to calculate the equivalent shear strength. Most of the existing studies are based on low stresses in conventional embankments, but few studies have been carried out on the applicability of this method under high stresses. This study focuses on the foundation treatment project for a clay core rock fill dam in Rwanda. The stress-strain behavior, micro-failure mechanism and equivalent shear strength of composite specimens with different area replacement ratio were investigated by simulating large-scale triaxle tests with discrete element numerical methods and compared with the widely used parametric composite method. The results show that the stress-strain characteristics of stone column composite foundations at high stresses differ from those at low stresses, and show a strain hardening trend. Composite specimens show a significant non-linear trend in strength at high stresses. The shear strength parameters calculated by the parameter composite method overestimate the strength of composite foundations, and it is recommended that they be discounted in engineering applications.

The Shiliushubao landslide is one of the giant landslides with complex structure in the Three Gorges Reservoir area. Since the dam was filled with water, the landslide has shown signs of revival, causing loss of life and property to several people around. In order to study the deformation failure mode and response mechanism of Shiliushubao landslide under the fluctuation of reservoir water level, the large-scale physical model test was used to accurately control the fluctuation condition of the experimental reservoir water level, and the displacement sensor, earth pressure sensor and pore water pressure were embedded in the slope. The sensor was used to analyze the experimental phenomenon. The results show that the influence of the reservoir water level fluctuation is mainly concentrated at the foot of the front edge of the landslide, and the rapid decline of the reservoir water level has a significantly greater effect on the landslide deformation than the increase of the reservoir water level; The mechanical response of the slope body has a hysteresis, and the effective soil stress increases when the reservoir water rises, the anti-sliding force of the sliding belt increases, and with the increase of the rising rate, the penetration force directed into the slope is larger, which is conducive to the stability of the landslide; Under the condition of the reservoir water level, the deformation and failure mode of the Shiliushubao landslide is sorted as: original slope → Erosion and erosion expansion at the foot of the slope → formation and expansion of the fissure at the foot of the slope → formation of the fissure on the slope surface → local slump, which is a hydrodynamic pressure landslide. The test revealed the deformation mechanism under the condition of reservoir water level, and provided a reference for the study of similar landslides.

In order to realize the effective utilization of winter idle water resources in kariz of Turpan Basin and recharge the regional groundwater, it is urgent to carry out groundwater recharge project in this area and determine the reasonable construction location and effective recharge mode. Firstly, the suitability evaluation system of groundwater recharge was constructed based on the six indexes of kariz flow, recharge source distance, aquifer permeability coefficient, groundwater depth, electromechanical well density and terrain slope. The suitability zoning of groundwater recharge was carried out by using ArcGIS spatial analysis function. Field tests were carried out in the typical recharge suitable areas to study groundwater recharge methods. The results show that there are abundant recharge water sources and storage space in the middle of Gaochang District, the north basin irrigation area of Shanshan County and the northeast part of Toksun County. The overall permeability coefficient is greater than 15m/d, which is suitable for the recharge of kariz winter leisure water. The effective recharge of groundwater can be realized by using the well irrigation method of the electromechanical well recharge, which is suitable for the recharge of the winter idle water in the study area.

To maximize the cost-effectiveness of green infrastructure (GI) implementation, a pilot project in Guangzhou Tianhe Smart City was selected to conduct the study. Setting runoff volume reduction rate, suspended solids load reduction rate, and life cycle cost of GI as optimization objectives, SPEA2 was coupled with SWMM to obtain a series of GI optimal spatial allocation schemes with land utilization as the constraint condition. The results show that with the increase of the rainfall recurrence period, the integrated reduction rate and the range of the GI optimal spatial allocation scheme set gradually reduce. The sunken lawn (SL) is the most cost-effective GI while the green roof (GR) is the least. When the investment is low, the area of SL can be planned to the maximum before planning other GI. If the integrated reduction rate is high with sufficient funds, GR can be considered based on the large allocation area of other GI. The results can provide theoretical support for the implementation of the sponge city program.

In order to study the influence of high tidal current velocity on the dynamic characteristics of horizontal axis tidal turbine under free wave conditions, STAR-CCM+ was used to establish a numerical calculation method for the hydrodynamic characteristics of tidal energy turbines under sea wave conditions. The law of wave influence on the rotation of tidal energy turbines and the characteristics of wake flow generated during the rotation were obtained. The results show that the amplitude and frequency of the angular acceleration of the tidal energy turbine are affected by the waves, but the fluctuation amplitude is less than the wave amplitude, the variation frequency is higher than the wave frequency. The wake flow produced by the rotation of the hydraulic turbine will make the flow field around the next hydraulic turbine more chaotic, and will have an impact on the blade rotation, turbine shaft load and energy utilization efficiency. Based on the analysis of the changing trend of pressure fluctuation, it is considered that the wake flow has little effect on the fatigue damage of hydraulic turbine.

Based on Hopf bifurcation theory, the stability of pumped storage power station considering asymmetric water passing system is studied. Firstly, the mathematical model of the speed regulation system of the pumping and storage unit of the one-pipe two-machine asymmetric water passing system with the upstream surge chamber is established. On this basis, the Hopf bifurcation analysis is carried out to obtain the theoretical stability region of the speed regulation system, and the dynamic response characteristics of the unit under different control parameters are analyzed to verify its theoretical stability region. Furthermore, the multi-scale oscillation characteristics and its generation mechanism of the dynamic response of a pipe double pump storage unit are revealed. Finally, the influence laws of flow inertia time constant, turbine inertia time constant and surge chamber time constant on system stability are explored. The results show that the Hopf bifurcation of the speed control system of the pumping and storage unit of the one-pipe two-machine asymmetric overflow system with the upstream surge chamber is supercritical, and its stability region is determined by two bifurcation lines; The hydraulic interference between the surge chamber and the units makes the response characteristics of the units show obvious multi-scale oscillation characteristics; Larger flow inertia time constant and smaller turbine inertia time constant are beneficial to system stability, and the influence of surge chamber time constant on system stability presents saturation characteristics. The research results have important guiding significance for the intelligent control of pumping and storage units and the design optimization of water passing system in power stations.

Aiming at the shortcomings of low efficiency and time-consuming when using the ANSYS parametric design language (APDL) to carry out the three-dimensional finite element design of the gate structure, this paper proposed a APDL design-analysis program based on VB, and performed nephogram results on a certain project. The results show that the program can improve the design and analysis efficiency of steel arch gate, and programmers can flexibly debug related to practical project cases, so that the designed steel arch gate can meet the needs of project construction.

In order to deeply understand the impact of the alteration of different opening angles of the two stage flap valves on outflow, a two- stage flap valve of a certain pumping station was taken as an example. Choosing four opening angle schemes widely used in practical projects, the three-dimensional flow pattern behind the two stage flap valve under different flow rates was simulated. The influence of flow streamline, velocity uniformity and hydraulic loss in culvert on the flow pattern was analyzed. The results show that the resistance loss coefficient along the outlet culvert is inversely correlated with the opening angle, to be specific the larger the opening angle of the flap valve, the less the hydraulic loss of the water flow in the outlet culvert pipe, and disparity degree becomes more obvious with the increase of the flow rate. When the flow rate is 2 m³/s, the hydraulic loss of the outlet culvert pipe in scheme 4 decreases by 49.6% compared to that of scheme 1; When the flow rate is 16 m³/s, the hydraulic loss of the outlet culvert pipe in scheme 4 decreases by 79.1% compared to that of scheme 1. To conclude, the larger the opening angle of the flap valve, the better the flow pattern in the culvert and when the flap valve is opened to 46°for the upper flap valve and 64°for the lower flap valve in scheme 3, the flow pattern in the culvert has tended to a better state.

The "reinforced concrete shield and riverbed" junction or pre-excavated pits at the end of the apron of a gate dam with supercritical flow connection mode are often damaged by foundation erosion, which not only leaves the apron in a suspended state, but may also cause the flow pattern at the end of the apron to deviate from the designed supercritical flow pattern, or even form a hydraulic jump like large-scale rolling and scouring riverbed, but there are few relevant research results. For the scenario that suspended foundation at the end of apron caused by local generalized scouring, the detailed observation and computational analysis of the flow patterns near the scour pits of different sizes at the end of the apron were carried out using physical model experiments and three-dimensional turbulence numerical modelling methods. Compared to the supercritical flow pattern at the end of the apron when the foundation is not scoured, the results show that the scour pits change the flow pattern significantly, and can be divided into three categories. The first category is the hydraulic jump upstream of the apron, the second category is the mixed flow in the scour pit and the third category is the quasi-periodic flow pattern consisting of the first two categories. The results of the flow evolution study can provide technical support for the analysis of large-scale damage to the retaining structure downstream of the dam apron, which has certain engineering application value.

In order to improve the safety management level of sluice project construction and the traditional manual management mode, this paper proposed the automatic identification process of large-scale sluice project construction hazards based on the database and BIM technology. For solving the low efficiency of construction safety management, database and BIM technology were used to store the large-scale sluice project construction hazards sources. A identification system of large-scale sluice project construction hazard was developed by using computer Technology, which improves the efficiency of sluice project construction safety management and provides reference for information management of construction hazard sources.

The plane gate controls water storage and discharge by opening and closing, and is easily damaged by the pulsating pressure of the water flow during operation. In order to study the interaction process between the opening and closing motion of the gate and the flow through the gate, this paper firstly conducted a three-dimensional numerical simulation of the flow through the gate during the opening and closing process of the gate under different bottom edge forms. And then the Hilbert-Huang transform was used to analyze the flow through the gate, and the time-frequency-amplitude information of the signal. The information analysis and comparison found that the bottom edge of the combined gate with a forward tilt of 45° and a backward tilt of 30° is gently affected by the pulsating pressure at the bottom of the gate, and the change difference of the energy amplitude at the measuring point was the smallest, and the water flow state was relatively stable. This study can provide a reference for the analysis of the pulsating pressure of the water flow through the plane gate.

Aiming at the problems such as unstable design quality, long design cycle and large repetitive workload in the current gate design, based on the whole process three-dimensional parametric design concept, and according to the design specifications and manuals, a three-dimensional parametric design method for the whole process of gate is proposed, that is, the three-dimensional parametric geometric modeling, spatial structural analysis and engineering drawing of plane gate structure are realized on the same platform by writing corresponding programs. This method can make the gate structure transition from plane design to space design, make the design process more intuitive, improve the quality and efficiency of the design, reduce the repetitive workload caused by design changes in design process.

In order to realize the timing matching and disposing of the main alarm information of the hydropower centralized control platform, a timing matching and disposing model was constructed based on Python data visualization. The model transmitted the fault information of hydropower station equipment to the receiver of hydropower centralized control platform by using communication server, and the fault alarm sequence was generated. After matching the main fault alarm information according to the time sequence matching rules in the domain expert matching rule base, state function and state change function were used to analyze the time sequence characteristics. Then the mapping table was used to describe the timing characteristics of the main alarm information. After analyzing the timing characteristics of the main alarm information, the timing matching and disposal of the main alarm information in the hydropower centralized control platform were realized. Experimental results show that the model has good visualization ability of main alarm information, and the coverage rate of main alarm information crawled by the model is up to 98.99%. The model has higher Pearson correlation coefficient and better ability to deal with the main alarm information.

At present, BIM technology has been applied in some majors of water conservancy and hydropower engineering projects, but it has not yet formed the overall collaborative design and systematic digitalization of the whole process. This paper aims at the characteristics of the Jinchuan Hydropower Station project with high positioning, deep covering of the face rockfill dam, complex geological conditions of the diversion power generation system and the actual needs of the project. The whole process of 3D BIM design has been implemented, the standard system has been clarified, and digital surveys have been carried out for all majors and all stages. This research realizes BIM collaborative design, application of 3D design results, dynamic update, and the whole process of lightweight digital handover on web and mobile terminals, establishes a digital achievement management platform, and lays a data foundation for smart engineering and digital power plants. At the same time, the "BIM+" multi-source data management has been carried out to realize the functions of BIM-based geological forecasting, construction progress management, dynamic feedback analysis, and intelligent management of safety monitoring, which provides a platform basis and theoretical guarantee for safety risk control and lean construction management. This research provides a reference for the whole-process, all-professional overall collaborative design and systematic digital application in other hydropower projects in the future.

UHV DC wall bushing is the neck-jamming technology of China’s power grid. At present, not only its core design and manufacturing technology still have many difficulties to be overcome, but also the state monitoring technology of its equipment operation is also a hot issue. This paper explores the application of an on-line monitoring technology based on vibration signals in UHV DC wall bushings. On the basis of analyzing the structure and common faults of UHV DC wall bushings, theoretical simulation research is carried out. It is found that when the outdoor insulation or inner insulation of the UHV DC wall bushing is damaged, the fundamental characteristic frequency of the bushing changes significantly. Afterwards, this paper carried out fault simulation and vibration tests on the cracking of capacitor core and the rupture of silicone rubber shed of the 800 kV UHV DC wall bushing. The results show that the fundamental characteristic frequencies of the bushing under different fault conditions are quite different. Therefore, the use of vibration monitoring technology can effectively identify the faults of UHV DC wall bushings, which can provide technical reference for UHV engineering construction and operation and maintenance personnel.

In order to study the ion flow field problem near the ground of UHV DC transmission lines, the BPA method is applied to solve the ion flow field of bipolar DC transmission lines. The synthetic electric field is solved combined with the nominal electric field calculated by the successive image method. The ion flow field and synthetic electric field problems of ±800 kV DC transmission lines are calculated using the BPA method, and the effects of erection height, interelectrode distance, and sub-conductor radius on the synthetic electric field of UHV DC transmission lines are analyzed. In addition, the power-line method for solving the synthetic electric field strength is compared. The results show that the BPA method is accurate and effective in solving the ion flow field, and the calculation efficiency is greatly improved. Increasing the height of the wire erection and increasing the radius of the split sub-conductor can improve the electromagnetic environment near the ground, while reducing the interelectrode distance can reduce the synthetic electric field intensity near the ground, but the effect is not obvious.

To address the challenges in oil leakage image recognition of peak regulation power equipment, a new method is proposed by introducing logical rule discrimination strategy into the task of image recognition. The technology of histogram equalization is adopted to improve original image. Then Mask RCNN network is introduced to obtain the preliminary location and contour information of storage device, ground and suspected oil area. Based on the above information, positional relationships between objects are judged, and logical expressions are adopted to determine the oil leakage area. Example analysis is conducted based on filed images of peak regulation power equipment. The results indicate that the proposed framework solves the problems in oil leakage area recognition, largely boosting model performance.

For the task of condition evaluation of peaking power equipment, the monitoring indicators are defined as a set of time series, among which the complex coupling relationships need to be considered. Besides, requirements on processing time are introduced by the real-time systems. A new framework is proposed to address these problems via the technology of parallel feature extraction as well as data fusion. The time series are statistically analyzed in parallel where multiple hypothesis testing is used to select the important features. Using a defined hierarchical graph convolutional network, the related information is integrated for the final condition evaluation task. Compared with the existing models, experiments indicate that the proposed method with stronger transferability and shorter processing time has a much higher predication accuracy.

In the weak current network, due to the large impedance characteristics of the power grid, the impedance parameters in the line change the key parameters of the rectifier control, affecting the overall performance of the rectifier, which may lead to the unstable output of the rectifier, and the output presents the characteristics of sub-synchronous oscillation. On the basis of not increasing the hardware compensation system, this paper proposes a control strategy that can effectively suppress the sub-synchronous oscillation. Based on the mathematical model, the AC current component of the sub-synchronous oscillation is extracted through the low-frequency filter. After d/q transformation, the d/q current component of the sub-synchronous oscillation is PI closed-loop controlled. The output value of the PI regulator of the subsynchronous oscillation component is decoupled and compensated, and then multiplied by the compensation coefficient to obtain the d/q compensation component of the voltage. The output of the original current inner loop is compensated. A simulation and test results show that the control strategy is effective and feasible, which can suppress sub-synchronous components.

In order to ensure that the conductor length of multiple parallel coils of power transformer is consistent and the current density is balanced, the structure transposition is usually carried out in the winding process. The actual operation shows that the insulation at the conductor transposition is easy to damage and leads to inter-turn short circuit fault. Aiming at the problems that the fault point is difficult to set and the electrical quantity cannot be directly detected in the actual test, this paper uses the 'field-circuit' coupling principle to take the distribution transformer with the model of S13-M-200/10, the low voltage winding is wound by two flat copper wires and the transposition point is in the middle of the winding as an example. Based on the finite element simulation software, the simulation analysis model with the same size as the physical structure is established. Through the comparison of the actual test value and the simulation analysis value of the performance parameters, on the basis of verifying the correctness of the model, the electrical characteristics and electrodynamics of the low voltage winding of the power transformer are studied when the single inter-turn short circuit occurs at the conductor transposition. The results show that when a single inter-turn short circuit occurs in the low voltage winding of the transformer, the loop current of dozens of times the rated current flows inside the short circuit ring, the fault phase current decreases slightly, and the active power loss increases sharply. Conductor transposition causes uneven distribution of axial force and radial force of the coil, and the winding is prone to instability and deformation. It is necessary to take mechanical and insulation strengthening measures at the conductor transposition.

After a high proportion of new energy is connected to the grid, the grid security and stability are significantly increased by multiple uncertainties. In order to quickly form a power adjustment plan to maintain the source-gridload dynamic balance under the scenario of power gap caused by large fluctuations of new energy, it is urgent to quantitatively evaluate the maximum power supply capacity of the grid. In this paper, the maximum power supply capacity and the minimum section margin of important sections are taken as the optimization objective functions, and the maximum power supply capacity assessment scenario of provincial power grids is modeled with power balance, slice reserve capacity, and section margin as the constraints, and the multi-stage constrained multi-objective evolution (CMOEA-MS) algorithm and the fast non-dominated ranking genetic algorithm NSGA-Ⅱ with elite strategy are used to solve the model, respectively. The quality of the solution sets of the two algorithms is evaluated in term of three indexes of convergence, uniformity and extensiveness of the solution sets. The simulation results of example show that the CMOEA-MS model has larger super volume values and better performance in solving the model, and can effectively improve the maximum power supply capacity of the provincial grid.