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

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.