The automatic monitoring system of Manwan hydropower station has been in operation for 11 years. This paper introduced the main problems in operation. Accordingly, some innovation measures were implemented and good effect was achieved.

Multi-point displacement meters are widely used in deformation and displacement monitoring of slope rock mass and cavern rock of water conservancy and hydropower projects, which can realize automatic monitoring and safety warning. The new multi-point displacement meter device introduced in this article is a new structural type different from the old described in DL/T 1272—2013, including an anchor head, a transmission rod (steel pipe) and a plastic protection tube installed with concentric shafts, as well as the orifice mounting base and the matching displacement sensor. Its application range and measurement accuracy are exactly the same as the multi-point displacement meter device, and its technical performance is superior. It has advantages such as high equipment precision, easy installation and high observation accuracy. Moreover, one of its important technical achievements is realization of the dual functions of manual instrument measurement and automatic measurement by displacement sensor, which can be used to verify the automated measurements and realize the continuous observation by use of the manual measurement data during replacement of the displacement sensors.

After years' operation, seepage may occur at earth dams. This paper analysed the types and cause reasons for seepage, and, accordingly, advanced some preferred treatment schemes and issues calling for attention in construction, for reference.

Discussion was made on fitted line parameter of a sensor by different ways, so as to understand the meanings of the linearity in hydraulic monitoring sensor and the effect of different linearity in measurement using sensor or calibration sensor.

This paper focused on the main characteristics and seepage causes of diseased embankment dams. By introduction of the mechanism and effect of some treatment methods, such as grouting and concrete anti-seepage wall, the paper put forward some optimized programs and pointed out the issues that attention should be paid to in construction, for reference.

As the second largest hydropower station in China, Baihetan hydropower station has a total installed capacity of 16 000 MW. It has the characteristics of high water head, large installed capacity and large HD value. To ensure its safe operation, 38 900 tons of steel were used to make penstocks, including 10 100 tons of 800 MPa high-strength steel. This is the first case where thickness of 800 MPa penstock reaches 68 mm in domestic hydropower industry. By studies on 800 MPa high-strength steel and a large number of tests, it is proved that the use of 800 MPa high-strength steel meets the function requirements of large power stations.

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.

Safety detecting refers non-destructive detecting using repetitive and temporary fixed instrument to detect dikes in order to find out perils or danger existing in dikes,so,it is very important for dike safety.At present,field safety detecting has become the weak part in dike has made an investigation and study on specifications and regulations concerned, analysis on technology status at home and abroad.1Moreover,the instruments,methods,and detecting results are introduced,some suggestions on improvement and detecting results are introduced,some suggestions on improvement and reinforcement are brought forward.

Elastic modulus of concrete is akind of imponant performance of concrete, which can reflect the relationship between stress and deformation, and is one of parameters in structure calculating. In order to improve crack resistance of concrete. we often increase tensile strength and ultimate elongation, and decrease elastic modulus and shrinkage of concrete. Decreasing elastic modulus will be beneftt to crack resistance of concrete. In this paper, we present the influencing factors of elastic modulus, and analysis the influence of aggregate and its content on elastic modulus by U.J.Counto model, and show the measures of decreasing elastic modulus of concrete, which will be helpful to averting of concrete crack.

It is the first vast application of low-heat cement in the concrete used for construction of a 300 m super-high double curvature arch dam. Through the research and application of low-heat cement and low-heat cement concrete, the performance characteristics of concrete in the construction process have been comprehensively mastered. By giving full play to the characteristics of low-heat cement such as low hydration heat, high strength and good durability, the overall quality of concrete construction of Baihetan hydropower station has been effectively guaranteed.

This paper collected and reorganized the calculation results of dam-breach flow of some hydropower stations in the power industry, and summarized and analyzed the current status of dam-breach flow calculation from the aspects of calculation methods and breach shape. The results showed that there were some problems in dam-breach flood analysis, such as improper selection of calculation methods and random assumption of dam breach shape. The suggestions provided in this paper could be used as a reference for dam breach analysis and research in similar projects.

This paper analysed the formation and characteristics of100-year return flood occurred in Weigan River basin on23rd July,2002, summarizing the general situation of this flood real-time forecasting and dispatching.?

The diversion tunnels of Jinping Ⅱ hydropower station extend across Jinping mountain, including the areas with high stress and high external water pressure. The tunnel section is huge. In order to ensure the long-term and safe operation of the power station, the maintenance channels are arranged for diversion tunnels. This paper introduces the design and structural calculation of the maintenance shaft of emergency gate in water inlet and the access door of construction adit at the head and end of the diversion tunnel.

A water conservancy project in Xinjiang is located in a cold and arid area. The water retaining structure is a RCC gravity dam with a maximum height of 75.5 m, and the total storage capacity is 294 million m3. The unfavorable climate, namely cold, hot, windy and dry in typical severe cold region and the intermittent construction method have increased the difficulty of temperature control and crack prevention of dam concrete. By taking a series of temperature control measures from design to construction, including pouring temperature control, pipe cooling optimization, permanent thermal insulation of dam surface, temporary thermal insulation in spring and autumn and overwintering thermal insulation of the lift surface and other exposed surfaces, and pouring plan optimization, the cracking risk of dam concrete has been substantially reduced, and the temperature cracks of dam concrete have been effectively controlled.

Based on design review, the typical problems in design of safety monitoring for small reservoirs were systematically summarized, including inadequate capability of design organization, omission of important design content, incomplete design-related basic information, improper utilization of existing safety monitoring equipment, design divorced from engineering practice, confusing set of important and unimportant monitoring items, and et al. It is proposed that the quality management of safety monitoring needs to be enhanced in aspects such as more attention paid to the design, improvement of guidance and training, strengthening of design inspection, special focus on safety monitoring design of reinforced and newly-built small reservoirs.