Water conservancy and hydropower projects have the characteristics of long construction period, complex structure, and being greatly affected by natural factors. An accidental factor in operation may sometimes lead to systematic safety accidents of the whole hydropower station. The author summarizes some typical cases of domestic hydropower station accidents in recent years, and analyzes some risk factors needing attention in the construction and operation management of hydropower stations, to provide reference for design, construction and operation management.

Based on the excavation and disclosure of the downstream slope of the right dam abutment of lower reservoir of Zhouning pumped storage power station in Fujian province, combined with analysis of structure characteristics of slope rock mass as well as the relationship between the structure planes and the excavation surface, traditional stereographic projection software is used to evaluate the stability of excavated slope. Moreover, two-dimensional modeling and analysis is carried out by use of discrete element program UDEC, and together with engineering geological conditions, the stability of excavated slope is comprehensively analyzed and evaluated. Without support, the safety factor of the potential rock composite of the slope under transient working conditions cannot meet the requirements from specifications. After completion of shallow support (including shotcrete, system anchor and anchor piles), the safety factor of the potential rock composite of the slope under transient working conditions can basically meet the requirements from specifications, but the safety margin is not high. The application of system anchor cable support has better control effect on the stability of the rock composite.

To compile the Guide for safety assessment of hydropower dams in operation, the author collected the cause reasons for the typical cases of dam failures and accidents at hydropower stations domestic and abroad. This paper presents 8 cases, for reference.

By comparison the definitions in regulations of the former Soviet Union and China, the term precision, accuracy and trueness are redefined. Different from accuracy and trueness, it can be quantified.

Collimation method is most commonly used in monitoring of horizontal displacement of a dam. With the popularization and application of total station instead of theodolite, the total station is widely used for horizontal displacement monitoring with the collimation line small angle method. To ensure the accuracy, one or more intermediate stations should be added as the maximum length of the collimation line of concrete dam is more than 300 m, while the maximum length of the collimation line of earth dam is more than 500 m. The analysis and practice of segment monitoring shows that it is of high precision provided that the displacement monitoring precision of the intermediate station is well controlled.

Leakage is common for reservoir dams which not only affects the project benefits, but also causes serious hidden risks, can even lead to a dam break. Locating the leakage and its passage is the basis for further treatment which is key to ensure the safe operation of reservoir dams. At present, there are many leakage detection methods with their own applicability and limitations, and are restricted by site condition, environmental condition and geological conditions. Suitable methods should be selected based on method characteristics and site conditions, to achieve better detection effect.

During investigation, design, construction and operation of tunnels, due to constraints and mistakes, failures happen. There are 10 cases at home and abroad presented in this paper, as well as the cause reasons and the lessons learned, for reference.

From the perspective of the role played by reservoir dams, the importance of reservoir dam safety to the realization of national water security strategy and dual carbon goals is emphasized. The safety operation of reservoir dams is always faced with severe situation and risks. By reviewing and summing up the safety supervision of hydropower dams, some suggestions are put forward.

The paper introduces some issues about the compilation of Guide for safety assessment of hydropower dams in operation, including the origin of assignment, aim, principle and the process of the compilation, the data collection and investigation, the relation between this guide and other related regulations as well as the main contents.

Data abstraction and structure design are the foundation of application system construction, which are related to the practicability, scalability and stability of the system. Before the application system is put into service, the necessary work flow is to initialize the system, create an instance of the management objects for the system, and then applications are implemented. This paper, taking dam safety monitoring and management information system - iDam as an example, elaborates its basic data structure design and implementation of initialization, for reference.

Intelligent dam management platform based on online dam safety monitoring and BIM modeling for Xinfengjiang hydropower station has modules such as three-dimensional display of the dam, online dam safety monitoring and controlling, management of dam safety monitoring, intelligent patrol inspection, management of defect and hidden danger, intelligent report compilation, account and document of hydraulic equipment, task management and other functions. By use of the platform, the integration of information from various dam safety businesses is realized and the problems in traditional dam management are solved. This paper introduces the construction principles, development mode, system framework, database design and function modules of the platform, as well as the time node of system construction. Further, the operation of each module of the platform is analyzed.

Due to the advantages of 3D model as describing geographic condition of terrain and landforms, the base maps of geographic information system (GIS) are transforming from traditional 2D maps to 3D models. Oblique photography models are becoming the main elements of 3D GIS, because of its high efficiency of data acquisition and 3D modeling, as well as its good effects. However, the application of oblique models in 3D GIS is limited by the low efficiency of transmission and rendering in the front end caused by its large size. In order to solve this problem, the popular 3D rendering system, Cesium and its data format, 3d tiles are studied in this paper. The data organization, publishing, browsing and interacting of this solution are analyzed and actual data are adopted. The applicability in 3D GIS for small and medium power stations of this solution is proved and could provide references for development of larger 3D GIS system in the relevant fields.

Slope deformation is considered as an important index of reservoir stability. This paper introduces a study of deformation monitoring of most reservoirs in Shenzhen. All the data are collected by the COSMO-SkyMed system during 2013~2016. In the typical analysis on Changlingpi reservoir, a deformation model combined with water level data is built. By use of the model, the total deformation is successfully divided into the one caused by water level and the one caused by dam settlement. As well, a comparison between different components of the deformation is conducted. Compared to traditional technologies, InSAR collects more monitoring points, so it is more comprehensive. In the future, the studies on slope deformation mechanism and stability analysis can be largely enhanced by InSAR data.

Baihetan hydropower station has a huge installed capacity as well as large unit capacity, therefore, the transportation of major parts is one of the important tasks. Combined with the feasibility study of Baihetan hydropower station, the implementation of transportation of the major parts is introduced in this paper, for reference.

In March 2019, affected by extreme freezing rain and drift ice, the Spencer dam in Nebraska burst after overtopping, resulting in one death and damage to some infrastructure. This paper introduces the accident process and emergency measures of Spencer dam, and analyzes the causes of dam break from the aspects of hydro meteorology, dam structure and operation management. The damage to hydraulic structures due to freezing load or freezing disaster has also occurred in cold areas of China. The reflection, experience and lessons of Spencer dam accident are presented here to provide reference for dam safety supervision and operation management in cold areas of China.

The“1·12”water inrush accident of Guanzhou hydropower station reflects the problems that the main responsibility of safety management is not implemented, the procedures of bidding and procurement are chaotic, and the quality of pipe bulkhead is poor. Enterprises in charge of the operation and management of hydropower stations should learn from this accident. In order to eliminate risk factors and ensure the operation safety of power stations, responsibilities of relevant departments should be fulfilled, technical management should be strengthened, and the sensitivity and responsibility of operation management personnel should be improved.

During the expansion of Chitan hydropower station, the blasting may affect the adjacent dam, powerhouse and switching station. In this paper, the important structures' dynamic response to blasting vibration is determined by three-dimensional dynamic finite element calculation. The results show that the safety of existing dam can be ensured by control of blasting parameters and by other protection measures in the process.

The calculation and analysis of dam break flood is an important basic work for dam risk assessment and emergency management. The size of dam break has a great impact on the calculation of dam break flood. At present, most research on the development of dam break is about earth rock dams, while the research on concrete dam break is less. So in the calculation of dam break flood, the geometric size of concrete dam break is usually assumed based on experience. According to the database of historical concrete dam break cases at home and abroad, combined with structural characteristics of concrete dams, the causes and failure modes of concrete dam break are counted and analyzed, and the general principle for estimating the size of concrete dam break is introduced, which provides a reference for determining the parameters of concrete dam break in flood calculation.