Taking the upper reaches of the Yangtze River at Guangyang Dam as an example, a physical model was constructed to analyze the changes of water depth and flow field in the corresponding river section before and after the implementation of the continuous pool-riffle type natural habitat restoration technology scheme. And then the effects of the habitat restoration scheme on fish spawning grounds, habitats, overwintering activities and waterways were discussed. The study show that after the implementation of the habitat restoration scheme, the area of the slow flow area in the test reach increased significantly, and a local slow flow was formed between the group of spur-dike, which was conducive to fish spawning and habitat; The implementation of the scheme did not adversely affect the vessel traffic in the channel of the river.

In order to explore the impact of landfall typhoons in China's coastal areas, based on the typhoon data and socioeconomic data from 1949 to 2020, M-K trend analysis, R/S analysis, wind and rain analysis, and disaster quantification and other research methods were used to comprehensively analyze the temporal and spatial changes, wind and rain characteristics and disaster situation of landfall typhoons in China. The research results show that the number of typhoons landing in China is decreasing, and the duration is prolonged. In terms of intensity, there is a situation of "weak decrease and strong increase", and the landfall sites are shifted to the east and north. Both the wind speed and precipitation of the landfall typhoon showed an upward trend. Considering the maximum value, it was found that the wind speed and precipitation showed a significant increase trend. The impact of typhoon has gradually evolved into a disaster pattern that has shifted from the secondary industry to the primary and tertiary industries. The research results can provide data support and scientific basis for reducing the economic losses of typhoon disasters.

In previous researches on intelligent fault diagnosis methods of the hydroelectric generating unit, the subjectivity of the artificial selection of the fault classification characteristics and the limitations of small sample data have important impacts on the accuracy of fault diagnosis results. To solve this problem, a CNN-SVM method for the fault diagnosis of the hydroelectric generating unit was proposed by combining with the feature extraction advantages of convolutional neural network (CNN) and the excellent ability of support vector machine (SVM) in processing small sample. In this method, the time-domain diagram of the vibration signal of the hydroelectric generating unit was used as the model input, and the CNN method was employed to extract the signal features. Then, the extracted feature vector was input to the SVM method to realize the final fault diagnosis of the unit. Finally, the advantages of the diagnosis method proposed in this paper were verified through a specific example analysis.

Currently, the electricity market is undergoing a new round of reform, and deviation assessment mechanisms have been introduced in various places to promote fair competition. In the face of the new market rules, the traditional dispatching model with maximum generation cannot be applied, and hydropower companies need to take market factors into account to control deviations. In order to save hydropower companies from paying costs, a study was conducted on the deviation control rules, and a bi-level optimization model with the objective of maximizing generation capacity and minimizing deviation was established to facilitate trading decisions. Taking the Three Gorges hydropower plant and Hubei province electricity market as examples, the Harmonic Search algorithm was used for analysis. The results show that the deviation rate in each interval is within the deviation control range, and the hydropower plant is exempt from deviation control. Thus, the bi-level optimization model mentioned above is feasible.

As a diversion tunnel, the pressure distribution of the tunnel body, the top and the bottom of the tunnel is very important to avoid cavitation, vibration and other undesirable phenomena. Taking the diversion tunnel of Yebatan Hydropower Station as the research object, this paper simulated the pressure distribution of the diversion tunnel based on the physical model test, as well as the three-dimensional numerical model established by the RNG k-ε turbulence model and the VOF method. The reliability of the three-dimensional numerical simulation was verified by the experimental data. The results show that the main flow of the diversion tunnel, the pressure distribution of the tunnel body at the sudden change of hydraulic boundary such as the inlet chamber section, the turning section and the plug section, as well as the variation trend of the bottom and top pressure along the way were analyzed. The research results show that the pressure distribution along the bottom and top of the diversion tunnel shows a downward trend, but at the sudden change of hydraulic boundary such as the sluice chamber section, the plug section and the turning section, the pressure value will show a large fluctuation of rapid increase or decrease.

In order to study the mechanical properties of rocks with prefabricated fissures, rock specimens with intermittent fissures at different angles were prepared. Uniaxial compression test was carried out on the specimens with fissures using uniaxial compression test equipment. It is found that the uniaxial compressive strength of 40° intermittent fissures is the largest, followed by that of 60°and 20°. The PFC2D was used to simulate the test process. The change law of microcrack and stress in the test process was analyzed. It is found that the strength of rock bridge has an important impact on the uniaxial compressive strength of the specimen. Through comparison, the change law of stress-strain curve of numerical simulation is basically consistent with that of physical test.

Based on the SRTM digital elevation DEM model, using the hourly precipitation data of Chongqing from May to September 2017 to 2021, this paper analyzed the temporal and spatial distribution characteristics of short-term heavy precipitation under different terrains in Chongqing, and discussed the relationship between the frequency and intensity of short-term heavy precipitation and topographic factors. The results show that the spatial distribution of short-term heavy precipitation in Chongqing is uneven. The overall average frequency high value area of the previous year and stations ≥ 60mm/h are mainly located near Huaying Mountain in Northwest Chongqing, Daba Mountain in Northeast Chongqing and Wuling Mountain in Southeast Chongqing; For the station average frequency of short-term heavy precipitation in Chongqing, the monthly variation shows a significant single peak type, and the frequency is the most in July; The diurnal variation is bimodal, with the main peak occurring most frequently at 03:00-05:00 and the secondary peak occurring more frequently at 16:00-19:00. The frequencies of the north and west slopes are slightly more than those of the other slopes. The frequency of flat slope and gentle slope is more than that of other slopes. The frequency of 500-1 000 m and > 1500 m is more than that of other altitudes; The fluctuation ≤30 m and 30-200 m are more frequent than other fluctuations; When slope ≤15°, altitude ≤1 000 m, and undulation ≤200 m, stations with precipitation intensity ≥100 mm/h appear, indicating that appropriate mountain topography is conducive to the increase of short-time heavy rainfall intensity. The research results can provide reference for near early warning, disaster prevention and reduction of short-term heavy precipitation in Chongqing.

Aiming at the large-scale backflow problem in the forebay with large forward diffusion angle of the pumping station, based on the CFD software, the RNG κ-ε model was used to simulate the flow state of the forebay of a pumping station. The hydraulic characteristics of the forebay under the original scheme were analyzed. The rectification effect of the figure-eight-shaped diversion piers was explored. The results show that adding figure-eight diversion piers in the forebay could effectively eliminate the large-scale backflow on both sides. The backflow area of the plane flow field disappeared, and the uniformity of the axial flow velocity distribution of the side unit was improved by 11.03% and 11.32% compared with the original scheme. The research results can provide a reference for the rectification of the forward forebay pumping station.

Based on the chloride ion diffusion model and aggregate gradation theory, the mesoscopic model of recycled concrete random polygonal aggregate was constructed using PYTHON and COMSOL. The validity of the model was verified by the existing experimental results. The calculation and analysis of the chloride ion erosion resistance of recycled concrete under different working conditions such as the diffusivity of new and old mortar, the thickness of old mortar and the replacement ratio of recycled aggregate was carried out. And then the diffusion law of chloride ion in recycled concrete and the influence law of critical factors on the chloride ion erosion resistance were studied. The results show that the simulation results are close to the experimental values, and the method can better simulate the diffusion of chloride ions in recycled concrete. The relationship curve between chloride concentration and depth shows discontinuous characteristics. With the increase of diffusion coefficient of new and old mortar, the chloride ion content increases gradually. The chloride ion erosion resistance of recycled concrete decreases with the increase of the thickness of old mortar and the replacement ratio of recycled aggregate.

The structural joints of face rockfill dam are the most important part and the weakest link of the seepage control system of dams. Taking a face rockfill dam as an example, the position, width, length of vertical failure joints and permeability coefficient of cushion area were simulated by finite element method. And then the seepage field law and permeability stability after water stop failure were studied. The results show that in the case of single fracture failure, the position, width, length of fracture and permeability coefficient of cushion are positively correlated with control factors of seepage flow, and the length of vertical fracture and permeability coefficient of cushion are the most significant. When multiple joints fail simultaneously, the seepage flow at cracked panel can be calculated by summing the failure results of single joints, and the results are safety. At the same time, it is suggested that the permeability coefficient of cushion should be 1×10^-5m/s or slightly smaller. The results can provide reference for the design and construction of similar projects.