Regulations for operational safety management of hydropower dams are the basis for practice. This paper systematically sorts through the existing regulations for operational safety management of hydropower dams,as well as clarifies the functions of the regulations and the division of responsibilities in dam operation and safety management.Then it is pointed out that tight supervision is formed in China, namely the power enterprises take the main responsibility,the National Energy Administration and its agencies perform supervision duties and Large Dam Safety Supervision Center supplies technical super- vision services for dam operational safety.

The long-term service as well as safety and stability of concrete dams are closely related to the performance evolution and durability of concrete materials.In this paper,the surface defects and internal defects of long-term service concrete dams are investigated,and the microstructure and performance of concrete are studied using comprehensive thermogravimetric analysis,scanning electron micro- scope and mercury intrusion method.The results show that the leakage and dissolution are main factors cause internal defects,changes in hydration products composition,degradation of microstructure and performance for concrete dams.Dissolution leads to a decrease in the content of Ca(OH)₂in hydration products,and causes damage to growth forms accompanied by appearance of a large number of CaCO₃ particles.At the same time,dissolution will cause further deterioration of the pore structure of concrete and the increase of internal defects such as holes and looseness,which is not conducive to the overall stability of the concrete dam.Special attention should be paid to the effects of cracks,leakage and dissolution during the operation and maintenance of concrete dams.

The seismic safety evaluation of dams must run through the whole life cycle of a dam,including design,construction and operation periods,etc.During the operation period,due to the changes in the internal and external conditions of the dam,it is necessary to timely review and evaluate the earth- quake resistance standards and capacity of the dam to ensure the dam operation safety.Based on the statistical analysis of the seismic safety review of hydropower dams during the operation period,the practical experience of seismic safety evaluation in the regular dam safety inspections is analyzed.Based on the quantitative analysis of the calculation results of seismic safety review of hydropower dams during the operation period,the method for rapid estimation of dam seismic capacity with the variation of seismic parameters is studied.The above-mentioned research results are of reference significance for the continuous seismic safety evaluation of dam structures in the whole life cycle.

Detailed analysis of the geological conditions,scouring model,measured scouring data,and scouring pit depth of Penglatan hydropower station in Meijiang,Guangdong province is carried out.By analyzing the measured data of scouring pits and calculation of the scouring pits depth,it is pointed out that there is a potential risk of further scouring of the downstream riverbed.The development pattern of scouring pits is consistent with design expectations and hydraulic model test results.Currently,the impact of the scouring pit downstream on the gate foundation is still slight,but it is close to the safety threshold for slope control.To prevent further scouring,it is recommended that treatment of the scouring pits at the sluice gate and the guide wall of powerhouse gate should be carried out first.Moreover,on- site monitoring of the dam foundation and downstream riverbed should be strengthened.

Sensors are needed on site to monitor the safety of water conservancy and hydropower projects.As well,cables are laid to monitoring stations to collect data.Specific installation structures are re- quired for monitoring sensors inside the building,and the centralized cables may exert certain impact on the project.This paper introduces the methods for cable connection,laying and protection,explores the layout and management of piezometer tubes for foundation of concrete dams,studies the installation structure of monitoring sensors for shield tunnels,proposes optimization measures,and proposes the use of horizontal and vertical waterproof cables for key parts of pumped storage power stations with ultra- high water pressure which can substantially reduce the potential risks caused by safety monitoring devices to hydraulic structures.The relevant experience has been successfully verified in practice and can be used as a reference for similar projects.

Currently,the automated tasks involved in the online safety monitoring system for hydropower dams include data processing,information pushing,message notification,and system monitoring across multiple modules.The automated tasks in each module are independently maintained,resulting in inconsistencies in execution standards,unstandardized recording and poor management which would lead to low task execution efficiency as well as difficult operations and maintenance.To solve this problem,the PowerJob distributed task scheduling platform is introduced to optimize and reform the automated tasks by taking full advantage of its centralized management,visualization,high reliability,and online log tracking capabilities. PowerJob enables centralized configuration,centralized scheduling,multi-node parallel execution,workflow arrangement and real-time monitoring for the automated tasks.Moreover,it is customized and extended to meet the execution requirements of automated tasks in the dam monitoring system,which improves the execution efficiency and convenience in operation and maintenance of the automated tasks.

As a new type of monitoring instrument,the array displacement meter has advantages of automatic and real-time acquisition,3D measurement,high precision,convenient transportation and storage,flexible installation and remote monitoring.This paper introduces the operating principle of array displacement meter and its application in monitoring of an earth-rock dam in Xinjiang.The monitoring results show that the array displacement meter has good application effect in settlement deformation monitoring of earth-rock dams,and has broad application prospect.

The uneven settlement of foundation caused by changes in the surrounding working environment during long-term operation of hydropower station has a significant impact on the safety of the hydro- power structures.Taking a hydropower station project as an example,Midas/GTS NX software is used to establish a three-dimensional finite element model.First,based on actual monitoring data,the forced dis- placement method is used to simulate the uneven settlement of the powerhouse building caused by geological collapse.Second,with the existing settlement,the stress changes of the powerhouse structure under different working conditions are simulated and safety assessment of dangerous components is conducted. Lastly,using uneven settlement as a warning indicator,a safety monitoring and control method is proposed. The research results indicate that the three-dimensional finite element model modified by the forced dis- placement method can meet the safety assessment requirements for hydropower stations with uneven settlement,and can provide reference for the safety analysis and monitoring of hydropower structures

Taking the seepage control project of Baihetan hydropower station as an example,the digitalmanagement of seepage control project of high arch dam is explored.This paper proposes the goal,tech-nology and achievement of development of a digital management platform for seepage control project ofhigh arch dam,including developing the parametric modeling tool,utilizing the BIM technology toachieve full process management,refining the design and improving the management level.By develop-ment and application of this platform,the design and management level of seepage control project ofhigh arch dam can be improved,providing reference for similar projects.

After the reinforcement of Longshan reservoir, there is a problem of settlement, which leads to cracks on the dam crest and has unknown impact on the dam operation safety. This study comprehensively uses pit exploration, drilling and geophysical exploration methods to evaluate the dam operation safety, analyze the current situation of dam filling, investigate and analyze the causes of cracks and settlement problems. Meanwhile, the impact of the infiltration line lowering caused by reinforcement is considered to conduct a preliminary evaluation of settlement. The results indicate that the settlement of Longshan reservoir is mainly due to the low filling quality in some areas of dam body and the infiltration line lowering, which leads to the consolidation settlement of filling material. Although the settlement situation still meets requirements, the risk of continued settlement cannot be ruled out. It is necessary to excavate the non- dense soil and rerun the thickening and reinforcement project. The relevant survey methods and analysis can provide reference for similar dam settlement problems.

The major dam shell of Xiaolangdi water conservancy project is filled with rockfill materials containing siltstone, clay rock and other soft rocks. After years of operation, the soft rocks on dam surface have weathered into fragments, and part of soft rocks have been eroded into rockfill voids, which will have a certain impact on the physical and mechanical properties of rockfill materials in the dam shell, such as the permeability coefficient and shear strength, and may also affect the stability of upstream and downstream dam slopes. At the same time, Xiaolangdi dam has large dam height, complex and deep overburden, many kinds of dam materials and complex operating conditions, so it is necessary to study the properties of rockfill materials in dam shell. Through in-situ excavation and sampling, relevant tests of the grading, compactness and permeability of rockfill materials and original rock character and strength are carried out to conduct the experimental study on properties of rockfill materials in the major dam shell. The results show that the main character parameters of rockfill materials in the major dam shell slightly changed, and the weathering degree and compressive strength of rockfill materials have limited influence.

In recent years, a large number of pumped storage power stations have been built in China, and the reservoir engineering geological conditions determine the feasibility of the construction. Through on-site geological surveys and tests, the leakage and bank slope stability of the proposed upper reservoir are evaluated. Research has shown that the project is located in an area with prominent leakage problems. It is recommended to deal with the problems of dam foundation leakage and seepage around dam during the anti-seepage of upper reservoir basin. The engineering slope is generally stable. For the broken rock body affected by faults, as well as disadvantage blocks formed by the cutting and combination of faults, interlayer joints and dominant joints, the effective support measures should be taken in time according to the excavation exposing situation.

The underground powerhouse of pumped storage power station is deeply buried, and is affected by many factors such as drainage gallery, water filling of tunnel, complex geological conditions and natural groundwater, so the complex seepage field is often formed. Based on the FEFLOW software, a three-dimensional steady state model of seepage including water transmission tunnel, underground powerhouse, drainage gallery, surrounding rock and fault is established. According to the simulation results, the initial seepage control and drainage scheme is optimized, eliminating unnecessary drainage galleries in the middle horizontal section and lifting drainage galleries in the lower horizontal section to discharge seepage water in the form of natural flow. The total seepage flow of drainage galleries and cavern group in the powerhouse area is 8 048.16 m ³ /d, which provides a greater flexibility for the selection of drainage pumps for underground powerhouse.

Due to the relatively concentrated timing of water distribution periods, in order to meet the needs of water allocation within the year and improve the water supply guarantee rate, the Xinjiwa reservoir is constructed in Zouping city, as supporting works for the first phase of the East Route Project of South-to-North Water Diversion. This project can realize the water supply goal of South-to-North Water Diversion Project and provide support for the regional national economic development. Focusing on the construction of dams for the reservoir, the design schemes are compared and selected from two aspects: reservoir storage depth and dam foundation seepage interception scheme. The selected design scheme can meet the requirements of the reservoir, and can provide reference for reservoir construction in water supply areas along South-to-North Water Diversion Project.

As more and more hydropower projects adopt the extra-deep (more than 100 m) concrete cutoff wall for seepage control treatment at dam foundation, the current estimated budget quota of hydropow⁃ er projects can not meet the demand of unit price calculation of concrete pouring projects. Taking the hidden risk treatment by extra-deep (148 m) concrete cut-off wall in Shiziping hydropower station as ex⁃ ample, the digital image technology is used to measure and analyze the concrete pouring efficiency for a year, and the relationship between average pouring efficiency and depth of extra-deep concrete cut-off wall is obtained. On this basis, combined with the relevant technical specifications, the calculation meth⁃ od and key points for unit price of extra-deep concrete cut-off wall pouring project are put forward.

At present, the external deformation monitoring of hydropower stations is still mainly carried out by traditional manual methods. Research on the testing and application of Beidou high-precision de⁃ formation monitoring technology was conducted in Tianhuangping pumped storage power station. Focus⁃ ing on the specific monitoring scenarios of hydropower dams, starting from improving the receiving equipment and algorithm of the domestic Beidou satellite navigation system for high-precision deforma⁃ tion monitoring, the existing monitoring system has been upgraded and improved. Through the compari⁃ son of dynamic loading displacements, Beidou calculation results and traditional manual observation re⁃ sults, the applicability of the domestic Beidou system in the deformation monitoring of hydropower dams has been verified.

Based on summary of advantages and disadvantages of common safety inspection methods, technology and equipment of underwater safety inspection are studied and some solutions are proposed, such as miniaturized high-power ROV, multi-beam combined ROV and intelligent unmanned ships. These solutions have addressed challenges of underwater inspection in complex environment such as deep-buried large-diameter long diversion tunnel, high-head multi-bend penstock and high-flow open water area. Moreover, these technologies have been successfully applied to cascade hydropower stations in the Yalong river basin, which is worthy of reference for similar projects.

Personal and property damage caused by water conservancy and hydropower projects, such as flood discharge, has become a common social problem. This paper analyzes various public safety risks in the river channel downstream of a hydropower station and accordingly explores and summarizes various control measures to prevent and resolve these risks in the affected area, for reference.

Sanguozhuang reservoir has been in operation for more than 20 years. The situation of sediment in the reservoir area has changed greatly under the influence of human activities. Thus, it is urgent to analyze the reservoir sediment and its influence on normal operation of the reservoir. In this paper, the sediment yield of Sanguozhuang reservoir basin as well as the sediment in front of the dam after 20-year and 50-year reservoir operation are estimated. Then, sediment distribution is calculated. By comparison between the calculation results and the actual sediment situation, the reliability of calculation results is verified. Accordingly, the influence of sediment on dead water level and normal water level of the reservoir are analyzed, to provide basis for the review of the reservoir scale.

Manwan hydropower dam has been in operation for 30 years. This article reviews the improvement of horizontal control network and the instruments for monitoring of dam horizontal displacement, external slope deformation and dam seepage. As well, the development of automatic monitoring system is introduced. While elaborating on observation methods, data processing and development of automation, the further development direction is also presented, for reference.

Tension wire alignment is commonly used in monitoring of horizontal displacement in the upstream and downstream direction of linear concrete gravity dams. The floating vessel should match with wire diameter and the distance between measuring points, or the size of floating vessels should be specifically designed. Otherwise, deflection and large draught of the floating vessel may cause system error of the tension wire alignment. For the case as the distance between measuring points is 35 m, the forces on the floating vessel are analysed, and accordingly, the vessel size is enlarged. On-site test on the accuracy of the measured values shows that it can meet the error requirements of the specifications.

Xiaojiang fault is an important geological boundary in southwest China, which exerts certain influence on the long-term stability of Baihetan hydropower reservoir. It is necessary to study the influence characteristics of the creep deformation of the active fault. Based on the geodetic monitoring results of Xiaojiang active fault and its adjacent areas, considering the strike-slip and thrust characteristics of the fault, a three-dimensional numerical generalized model is established to simulate and analyze the temporal and spatial evolution characteristics of the stress field around the fault zone under the long-term creep movement of 10 mm/a. The calculation shows that with the long-term creep of Xiaojiang fault, the surrounding geostress field presents an approximate linear and gentle increasing trend. The maximum principal stress increment of the rock mass near the fault zone in 200 years is about 0.35~0.55 MPa, and the stress increment in 1 000 years is about 1.1~3.3 MPa. After the reservoir impoundment, the influence area of reservoir water is limited to the periphery of the valley, and the direct influence on the geostress field in large area is not obvious. The relevant research results can provide certain reference for the long-term stability evaluation of the project.

Based on the the overstressing on rock support system in the excavation of tailwater surge chamber of Yangfanggou hydropower station, combined with on-site geology, support scheme and monitoring scheme, the dynamic feedback analysis model is established. Analysis results show that the main reason for the overstressing on rock support system is, on one hand, local unloading and relaxation caused by the exposure of dominant joints with middle and high angles on the side wall and along the chamber. On the other hand, the construction blasting exerts great influence on the bolt stress as the monitoring instruments are close to the excavation boundary. By analysis and according supplementary support, the deformation and bolt stress of the area tend to converge. The evaluation method can be used to analyze the the overstressing on rock support system.

Hushan reservoir dam is a sand dam with clay core wall located on gravel sand foundation. Over the past 50 years of operation, concentrated seepage was observed downstream of the riverbed section of the dam, which was caused by seepage in the dam foundation. Based on the engineering geology and hydrogeological conditions of dam foundation, finite element and flow network were used to analyze the seepage of the dam foundation and the clay covering. As well, the seepage stability of dam foundation was analyzed. Then the concrete anti-seepage wall scheme and the high-pressure jet grouting scheme were compared for seepage prevention of dam foundation. The results showed that the use of concrete anti-seepage wall to treat dam foundation was suitable, worth reference.

In response to the challenges posed by high complexity, technical difficulties, high safety risks, management difficulties, information silos and inefficient communication and coordination in the construction process of large-scale hydropower stations, digital, automated, and intelligent approaches are adopted. By leveraging advanced technologies such as the Internet of Things (IoT), cloud computing and big data, a comprehensive, all-encompassing, and end-to-end intelligent control system for construction is established. As well, data collaboration and sharing technology serving various units and specialties in hydropower station construction, intelligent monitoring and early warning technology for construction and operation safety, and intelligent archiving management technology for electronic documents during construction and operation are developed. These achievements have realized intelligent management of the whole lifecycle of hydropower stations, from design and construction to operational management, which can significantly enhance the safety, quality and efficiency of large-scale hydropower station construction.

This paper analyzes the technical difficulties in underwater installation of steel pipes in the water intake project of Jinshuitan water-cooling green data center. To avoid significant impact from reservoir water level change on engineering during pipe sinking, and to ensure stability of underwater bank slope during the operation of water intake steel pipes, the immersed tube construction technology for complex conditions is proposed. Furthermore, the technology is successfully applied, worth promoting under similar conditions.

Pumped storage power stations have relatively complex structures and the construction period is longer. Prefabricated modular pieces, which are standardized production in factory and assembled on site with high efficiency, is environmentally friendly. Based on the prefabricated modular construction applied to Yongtai pumped storage power station in Fujian province, this paper expounds on the structural characteristics of the pumped storage power stations and the prefabricated modular construction. Practice shows that application of prefabricated modular construction to construction of pumped storage power stations can help achieve green, efficient, environmental friendly and safe construction.

A hydropower dam is located in the canyon reach and the terrain on both sides is steep. To reduce project investment, the main room for cable crane is set underground. By use of upper guide pulley and through the shaft, the hauling system and hoisting system are transported into the underground room to provide power and cableway. This scheme not only can solve technical problems such as excavation and support of high slope, environmental protection and conservation of water and soil, but also can reduce investment and work amount, which is worthy of reference.

Based on the basic equations of hydraulics and the conservation of the sum of pressure and momentum on the section of conjugate water depth of the closed pipe when hydraulic jump occurs which exerts pressure on the pipe, the cause reasons of serious cavitation damage of gate shaped culvert pipe of a small reservoir operating with normal water level are calculated and analyzed. Results show that it is because of the cavitation and erosion caused by unfavourable flow regime in the pipe. Accordingly, prevention measures are put forward, for reference.

Since the impoundment of Qiyan reservoir, the seepage behind the dam increased gradually as the water level rose. On April 30, 2015, when the water level reached the elevation 1 218 m, the seepage hit 12 L/s, which was far beyond the designed allowable range and seriously affected the dam safety and stability. After analysis of the investigation results of dam foundation, the previous investigation results and the geological data during construction period, the curtain grouting by high-pressure jet grouting was adopted to control the seepage and the current operation showed that it was effective. This paper introduces the treatment technology, to provide reference for similar projects.

This paper introduces the structure and function of high pressure oil jacking device at a hydropower station, and analyzes the residual pressure in the main oil inlet ring pipe and main oil inlet pipe. Infrared thermal imagers are utilized to efficiently locate the faulty check throttles. Then, the causes for the residual pressure in the main oil inlet ring pipe and main oil inlet pipe are analyzed. Accordingly, prevention measures are proposed.

This paper introduces the fundamental principles of chemical anchoring technology, and in combination with case studies, outlines the key aspects of underwater chemical anchoring construction, to promote the application of this technology in the removal of blocked concrete and rock in parts such as sluice slots of hydraulic structures and to provide a new method of risk mitigation for hydraulic and hydroelectric projects.

With the continuous development of basin-level clean energy bases, integrated regulation of hydro-wind-solar power has become an important direction for the development of existing hydropower stations, which presents challenges for the traditional regulation of cascade hydropower centralized con⁃ trol centers, and the introduction of systematic and integrated regulation theory and methods is required. In response to this, a multi-time scale sequential nested regulation architecture for integrated hydrowind-solar system is constructed based on the actual needs of the lower reach of Jinsha river basin. The core business model is analyzed, and an integrated regulation process is established to provide a system⁃ atic solution for promoting the new energy consumption and ensuring the safe and efficient operation of hydropower stations in the clean energy bases.

The safety management for hydropower dam is a work that emphasizes both management and technology, and is an important part of implementing the main responsibility of power enterprises. This study provides an overview of the content and key points of safety management for hydropower dam, in⁃ cluding the implementation of laws and regulations, establishment and improvement of institutional mechanisms, talent cultivation and daily work, which can provide reference for the daily management of power enterprises.

With the construction and operation of a large number of hydropower stations, incidents such as personal injury and property damage caused by the gate opening and flood discharge have occurred from time to time. Through a comprehensive and systematic analysis of the safety hazards and risks in the flood prevention and emergency rescue work of Dahua hydropower station, the causes of problems are identified. Taking "responsibility defined by information" as the core idea, a systematic, routinized, standardized and regulated control mode is formed by constructing a prevention and control management platform, clarifying the responsible parties, formulating work standards and implementing accountability mechanisms. The practice shows that the flood prevention and emergency rescue work of the hydropower station has achieved the effect of clear responsibility, timely warning, efficient linkage and precise dis⁃ posal, whichhas resulted in good social and economic benefits.

This study puts forward a vehicle for the inspection of penstocks in hydropower stations, which has been successfully applied to the safety inspection of the penstocks of Unit 4 in Manwan hydro⁃ power station, to ensure the safe operation of penstocks.

To ensure the stability and reliability of gate opening and closing, a dual hydraulic cylinder configuration is typically used to drive the gate. Synchronizing the two cylinders becomes a critical fac⁃ tor when equipping the emergency actuator for the hoist. In this project, the method is applied that multi⁃ ple hydraulic hoists are able to share a single hydraulic emergency actuator for polling display of open⁃ ing during emergency operation. The emergency actuator is movable and once connected to the hydrau⁃ lic lines and cables, it can automatically identify the hoist number. The synchronized operation of two cylinders to open or close the gate is realized through relay interlocking protection, opening collection signal splitting and other mechanisms. The feasibility of using a single emergency actuator to alternately control three hoists is validated through on-site installation, testing and operation, which meets the ex⁃ pected performance and can offer reference for the emergency operation of similar hydraulic hoists in hy⁃ dropower stations.

Face-slab crack is considered as an influence factor of dam seepage to propose the seepage safety monitoring statistical model and RBFNN model. Combined with the specific project, the seepage monitoring statistical model and RBFNN model of a concrete face-slab rockfill dam are established, and the seepage flow is predicted. The prediction results are close to the actual monitoring values. At the same time, the weight of each influence factor of seepage flow calculated by RBFNN is not significantly different from the results calculated by traditional statistical methods, which shows that the model pro⁃ posed in this study is effective and applicable. The research results are of guiding significance for treat⁃ ment of the abnormal seepage flow mornitoring values of concrete face-slab rockfill dam with cracks.

The static leveling system for dam foundation of Daheiting reservoir has been in operation for nearly 20 years. During operation, abnormal values were detected at measuring points. Through the mon⁃ itoring system test, on- site and monitoring data inspection, and manual observation data comparison and analysis, comprehensive analysis and study of the abnormal conditions existing in operation are con⁃ ducted to find out the cause reasons, and it is determined that the vertical displacement of dam founda⁃ tion is normal and the dam body is operating stably, which can be used for reference to similar projects.