This paper provides a systematic summary of the current status and development direction of the standards system, regulatory system, management mode and technology for dam safety of China′s hy⁃ dropower stations. Responsibility shared among power enterprises, government departments and Large Dam Safety Supervision Center is established as the dam safety management mode of China′s hydropow⁃ er stations. China has released 101 effective standards and formulated a system table for dam safety stan⁃ dards. China has established a regulatory system centered around Regulations on the Supervision and Management of Operation Safety of Hydropower Dams. In the future, China will revise regulations, im⁃ prove standards and develop technologies to enhance the emergency response capability, informatiza⁃ tion, intelligence and internationalization level of dam safety, and promote the stable and far- reaching development of dam safety management.

In order to enhance the real-time capability of flood risk analysis and adapt to the dynamic characteristics of flood evolution, a 3D real-time flood risk analysis system based on the B/S architec⁃ ture has been designed. This system employs a coupled approach of the breach flow calculation software BREACH and the 2D hydrodynamic numerical model for dam-break flood calculation and simulation. It integrates WebSocket technology for real-time data transmission and utilizes Cesium 3D visualization platform to display the flood evolution. The core functional modules of this system are scenario manage⁃ ment, real-time calculation and calculation result analysis of dam-break flood, which can support dy⁃ namic management, real-time calculation and result visualization of the dam-break process. The system was validated through the case study of a reservoir. The results showed that the system can effectively re⁃ flect the flood inundation process, obtain reasonable calculation results, and enhance the intuitiveness of flood risk analysis and the decision-support capability through visualization technology

Taking factors affecting the accuracy of static leveling as the starting point, this paper analyz⁃ es the degree of influence of temperature difference and barometric difference in pipeline, pipe diame⁃ ter, etc, and proposes corresponding solutions. Also, this paper analyzes bubbles, liquid corrosion, dew condensation on float surface, contact friction, sensor measurement error and other factors, and proposes corresponding optimization methods. The error propagation rule of the static leveling system is explained and the pipeline test process is described, which can check whether the static leveling system works nor⁃ mally. Through comparison and analysis of artificial leveling observation data and automatic static level⁃ ing data of a typical project, it is concluded that after taking various methods, the measurement accuracy can meet the requirements of specifications.

Based on the digital twin platform, the intelligent engineering safety analysis and early warn⁃ ing system is studied and designed. The mechanism model of engineering safety monitoring is studied by using the data mining, intelligent analysis and diagnosis technology. To obtain early warning indexes for specific project, the evaluation system and criteria are developed, which has realized intelligent safety analysis and early warning. Moreover, it has been applied to a project and resulted in improvement of the accuracy and timeliness of early warning, enhancement of the level of intelligence, and decisionmaking support for the operation management department.

The uplift pressure and seepage volume are the most intuitive reflection of the foundation seepage behavior of concrete gravity dam. To get the general variation of the foundation uplift pressure and seepage volume of the gravity dam during operation period, the monitoring data of the main concrete gravity dams in domestic power industry are analyzed. The results show that it is a common phenomenon that the uplift pressure coefficient of partial foundation of the gravity dam exceeds the design value. However, due to the large safety margin in design, the anti-sliding stability of dam foundation could still meet the specification requirements in review and calculation. Under normal conditions, the foundation seepage volume of gravity dam is not greater than 5.0 L/s. The seepage flow of dam foundation of different projects is closely related to geological conditions, seepage control effect and earthquake, but has a weak correlation with dam height or dam crest length. The study results could provide some reference for monitoring data analysis and seepage safety evaluation of concrete gravity dams.

The purpose of online dam safety monitoring of hydropower stations is to dynamically evalu⁃ ate the dam safety status in real time, which can provide technical support for preventing dam break, overtopping and major structure damage. The online dam safety monitoring system should be practical, effective and useful. It is necessary to develop and approve a practical and effective monitoring plan be⁃ fore system development. Based on the statistics and analysis of the causes of dam failures in the dam en⁃ gineering history worldwide, this paper explains the risk identification and monitoring elements of dam operation safety, and proposes suggestions for the content, items and information organization of online monitoring, to provide reference in the development of online monitoring plan.

Acquiring dynamic material parameters of concrete dams is of great significance for verifying their seismic safety performance. At present, a common approach involves identifying the modal parameters of concrete dams from strong motion observation data and then constructing an objective function based on this information to optimize the material′s dynamic parameters. In this paper, modal parameters are identified based on strong motion observation data while simultaneously time-domain indicators from the seismic response sequence are extracted. A joint inversion of material dynamic parameters is conducted by constructing an objective function that combines both time-domain and frequency-domain information. Since the two objective functions differ in units and dimensions, a multi-objective optimization calculation is performed using the fast non-dominated sorting genetic algorithm with elitism strategies to obtain the Pareto optimal solution set for the dynamic material parameters of the concrete
dam. Inversion analysis of a specific engineering case demonstrates that the joint inversion method for concrete dam material dynamic parameters based on time-frequency domain information exhibits strong parameter identification performance and high stability, offering good application prospects in practical projects.

The deformable body of Guobu slope is on the right bank of Laxiwa hydropower station, 0.9~1.7 km upstream the dam. It is an ultra-large granitic rock slope with a volume of 102 million m 3 , affected by various deformation mechanism, mainly toppling deformation, and is classified as Class B Grade I. After the reservoir impoundment in March 2009, obvious deformation of Guobu slope is observed. Hence, scientific research, safety monitoring and risk control measures are carried out, including geological exploration, deformation monitoring, numerical calculations using various methods, and stability analysis. Due to the high deformation rate of Guobu slope in the early stage of reservoir impoundment, the deformable body of Guobu slope was assessed as a major hazard of Grade Ⅱ. In 2018, based on study results, Guobu slope was reclassified as a safety risk of Grade Ⅱ (acceptable risk of Grade Ⅱ). In October 2015, the reservoir water level reached the normal impoundment level of 2 452 m. Long-term monitoring data since then show that the deformation of Guobu slope has slowed down after the reservoir water level stabilized between 2 450 m and 2 452 m. The daily deformation rate by the monitoring point at the maximum deformation decreased to less than 2 mm/d. Currently, the deformable body of Guobu slope is generally stable, and the risk is controllable. This paper introduces the specific measures and achievements in the treatment of the deformable body of Guobu slope of Laxiwa hydropower station, for reference.

Shape accel array is widely used as it′s automatic, precise and reusable. Combined with the application of shape accel array to the deep deformation monitoring of the slope of a hydropower station, this paper introduces the components and application of shape accel array. The practice shows that the monitoring data are reliable and the system is stable, worthy of promotion to similar projects.

A high arch dam is located in an alpine valley with complex hydrogeological conditions. After impoundment, significant seepage has occurred in multiple drainage holes of the drainage tunnel of dam foundation on the left bank, which is a key concern of the project. To identify the cause of the seepage, based on the hydrogeological conditions during impoundment, seepage control and treatment measures, pseudo-random flow field method detection results, monitoring and inspection results, combined with nearly 10-year monitoring data under the 80 m cycle of reservoir water level fluctuation, a comprehensive analysis is conducted on the characteristics of seepage and seepage pressure in the drainage tunnel and behind the curtain, as well as the source of seepage. The results indicate that the curtain in dam foundation of the left bank is effective, the seepage and seepage pressure have decreased year by year and tend to stabilize, and the seepage volume is much smaller than the design pumping and drainage capacity of the dam foundation drainage well. The seepage mainly comes from mountain groundwater and downstream river water, and the seepage is safe and controllable.

To solve the problems that the transient deformation of dam structure is difficult to predict and the accuracy of deformation monitoring is not high, Beidou/global navigation satellite system technology is used to optimize the existing monitoring system, aiming to improve the monitoring accuracy as well as data transmission and processing speed of the system. The comparison results show that the optimized system is significantly better than the former in aspects such as degree of automation, deformation prediction accuracy, communication stability and monitoring accuracy, and the transmission and processing time of the optimized system is shortened by 11.7 s.

Hidden defects such as anthills, cracks, and leakage can adversely affect the safe operation of earth dikes. The use of high-density electricity method to regularly detect hidden defects of dikes and dams is effective. Therefore, understanding the response characteristics of DC electric field of hidden defects inside earth dikes is a prerequisite for the interpretation of geophysical survey results and the identification of hidden defect types, which is of great significance. In this paper, the finite element numerical simulation software is used to establish models of common hidden defects, such as anthills, cracks, and leakage, and the abnormal characteristics of different hidden defects on the high-density electrical inversion profile are studied. Moreover, this result is applied to the hidden defect detection of a reservoir in Henan province, which is proved to be effective.

In the numerical simulation of earth-rock dam, accurate and reliable mechanical parameters of dam material are the important basis for dam deformation prediction and dam safety evaluation. Based on the monitored deformation data of Luding core wall rockfill dam, the rheological parameters of rockfill and core wall materials are inversed in this paper. Combined with the actual filling and impoundment process of the dam, the numerical simulation is carried out, and the stress, deformation and differential settlement of the dam after completion and impoundment are analyzed. The results show that the obtained stress and deformation of the dam based on the inversed parameters are in good agreement with the actual situation, and the settlement and principal stress of the dam at the completion and during the impoundment period are within the allowable range. At the completion, the deformation inclination of the dam crest is less than 1%. During the impoundment period, the deformation inclination of the dam crest area increases due to the wetting deformation of the upstream rockfill material. Moreover, the deformation inclination of the dam crest axis is larger than that of the upstream and downstream sides, and the deformation inclination of the dam crest at the middle of the valley is the largest, but it does not exceed 3%, that means there would be no longitudinal cracks, which is consistent with the actual situation. The research results can well predict the stress, deformation and crack of the dam body, which provides important support for dam safety evaluation.

Taking the reinforcement of Maotan reservoir as study object, this paper introduces the existing safety hazards of the reservoir and the corresponding reinforcement scheme. The trial load method is used to conduct the structural safety calculation and analysis of the dam after reinforcement, and finite element analysis is employed for verification. The results of both methods indicate that the safety issues of the dam structure have been resolved. The paper also analyzes issues such as energy dissipation during discharge and seepage control on the dam surface. It is confirmed that the reinforcement measures for Maotan reservoir is effective, providing valuable reference for similar projects.

Since rehabilitation of Xianghongdian reservoir dam, the flood control level in flood season (from 15 June to 15 September) is set at 125.00 m. To better realize the social and economic benefits of the reservoir, such as flood control, irrigation, water supply and ecology, analysis of measured precipitation, flood and designed flood is carried out. Results show that dynamic control of flood level is feasible. By analysis of the risk and benefit, it is proved that dynamic control of flood level would bring considerable benefit.

To improve the accuracy of fault diagnosis for transformer, a fault diagnosis model for oil immersed transformer based on one-dimensional all convolution neural network is proposed. Firstly, the data of gases dissolved in the transformer oil is standardized and coded. Then the network of the proposed diagnosis model is established. By using the characteristics of all convolutional network and convolution kernel, the network structure can effectively extract fault features from input data and then apply it for classification. Finally, the model is trained and tested. The test result and contrastive analysis show that superior performance is achieved when the model is applied to fault diagnosis of power transformer.

The Jiudianxia water conservancy project is located in the high altitude and cold area. Its dis⁃ charge tunnel on the left bank is easy to freeze due to the low temperature and the wind through tunnel. The durability of lining concrete in the tunnel is seriously damaged by the freeze-thaw cycle, which af⁃ fects the service life of the tunnel. This paper puts forward a design scheme of installing flat insulation gate at the opening of underground tunnel to solve the problems of seepage water freezing and cyclic freeze-thaw damage to the lining concrete.

To ensure the safe operation of the gate dam and to prevent accidents, the permutation entropy (PE) algorithm is used to monitor the operational status of the gate dam. A gate being the research object, and its flow induced vibration data by each measuring point of the gate dam are obtained. Then, the improved variational modal decomposition (IVMD) method is used to denoise the original signals from different measuring points under different operation conditions and extract the effective operational feature information of the structure. Followed, the feature information of each measuring point at the data level are fused by using variance contribution rate and the subsequence entropy values of the fused data are calculated by permutation entropy method. By analysis of the entropy characteristics of different vibration states, online monitoring of structural vibration state is realized. The results show that the permutation entropy method can not only comprehensively extract effective information of the structure, but also present the vibration state of the structure in a relatively intuitive form. Furthermore, the calculation process is simple and efficient, which can provide reference for the safe operation and online monitoring of gate dams.

Starting from the characteristics of emergencies and the requirements for emergency decisionmaking, this study treats dam operation emergencies as a continuous dynamic evolution process, propos⁃ es a scenario quintuple description method for dam operation emergencies, and constructs a Bayesian network model based on the evolution phases of target nodes. This model is applied to scenario develop⁃ ment where flood impacts dam operation safety. The approach reveals the intrinsic patterns and evolu⁃ tionary logic of emergencies, thereby enhancing the scientific rigor and operational feasibility of emer⁃ gency measures.

The practical weir is common discharge control structure of spillway, and its head loss is an important parameter for calculating the spillway discharge capacity and the water surface line, as well as for the design of energy dissipator. The empirical formula for calculating head loss recommended by cur ⁃ rent specifications has low accuracy. Therefore, using the hydraulic boundary layer theory to derive the calculation formula of head loss of practical weir in spillway is of practical significance.