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.

Earthquakes, especially strong earthquakes, may easily cause dam accidents. The actual damage of the dam is determined by the earthquake intensity, which is related to the earthquake magnitude, hypocenter depth, geological structure and the distance between the dam and the hypocenter. To realize the graded warning for dams under the condition of earthquake, it is necessary to use the statistical model to quickly calculate the earthquake magnitude at the dam site and compare it with the design standard. By computer programming, the above-mentioned functions can be realized, which can quickly locate the dam that may be damaged by the earthquake and realize rapid early warning for the dam.

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.

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.

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.

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.

Among large and medium-sized hydropower stations in China, some of the older hydropower units that have been in operation for a long time have experienced a decline in performance and an increase in failure rates. It is of significance to take necessary technical measures to increase the capacity of the old units. Therefore, investigations and studies on the issue of hydropower unit capacity upgrading and renovation are carried out. Based on the survey, the existing problems and difficulties in the current implementation of hydropower unit capacity upgrading and renovation are analyzed and summarized, and suggestions are given for reference.

Combined with the operation management of reservoir dams, this paper first analyses the main contents of current research on engineering ethics in the field of hydraulic engineering. And then, based on social and natural dimensions, from the aspects of reservoir resettlement, reservoir degradation and decommision, public education, reservoir big data, reservoir management scope, reservoir aquaculture, biodiversity of reservoir area, etc., this paper discusses how engineers should correctly handle the interpersonal relationship as well as the relationship between mankind and nature in accordance with the code of engineering ethics.

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.

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 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.

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.

To eliminate the malfunction of the air-release valve in the gate chamber not being able to close or close early when filling the tail water unit section of Changlongshan pumped storage power station, this article briefly analyzes the structure and weight of the floating bucket, as well as calculates the release area and the average release speed of key parts in the valve. By doing so, a transformation method is proposed under existing conditions, which is to increase the diameter of the floating bucket and release hole, and cancel the floating bucket counterweight. After multiple on-site tests, the optimized parameters of the air-release valve have been obtained. Since then, the water filling and air release process of the tailrace gate chamber have become safe and reliable.

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.

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.

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.

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.