In order to study the ion flow field problem near the ground of UHV DC transmission lines, the BPA method is applied to solve the ion flow field of bipolar DC transmission lines. The synthetic electric field is solved combined with the nominal electric field calculated by the successive image method. The ion flow field and synthetic electric field problems of ±800 kV DC transmission lines are calculated using the BPA method, and the effects of erection height, interelectrode distance, and sub-conductor radius on the synthetic electric field of UHV DC transmission lines are analyzed. In addition, the power-line method for solving the synthetic electric field strength is compared. The results show that the BPA method is accurate and effective in solving the ion flow field, and the calculation efficiency is greatly improved. Increasing the height of the wire erection and increasing the radius of the split sub-conductor can improve the electromagnetic environment near the ground, while reducing the interelectrode distance can reduce the synthetic electric field intensity near the ground, but the effect is not obvious.

At present, BIM technology has been applied in some majors of water conservancy and hydropower engineering projects, but it has not yet formed the overall collaborative design and systematic digitalization of the whole process. This paper aims at the characteristics of the Jinchuan Hydropower Station project with high positioning, deep covering of the face rockfill dam, complex geological conditions of the diversion power generation system and the actual needs of the project. The whole process of 3D BIM design has been implemented, the standard system has been clarified, and digital surveys have been carried out for all majors and all stages. This research realizes BIM collaborative design, application of 3D design results, dynamic update, and the whole process of lightweight digital handover on web and mobile terminals, establishes a digital achievement management platform, and lays a data foundation for smart engineering and digital power plants. At the same time, the "BIM+" multi-source data management has been carried out to realize the functions of BIM-based geological forecasting, construction progress management, dynamic feedback analysis, and intelligent management of safety monitoring, which provides a platform basis and theoretical guarantee for safety risk control and lean construction management. This research provides a reference for the whole-process, all-professional overall collaborative design and systematic digital application in other hydropower projects in the future.

In order to realize the timing matching and disposing of the main alarm information of the hydropower centralized control platform, a timing matching and disposing model was constructed based on Python data visualization. The model transmitted the fault information of hydropower station equipment to the receiver of hydropower centralized control platform by using communication server, and the fault alarm sequence was generated. After matching the main fault alarm information according to the time sequence matching rules in the domain expert matching rule base, state function and state change function were used to analyze the time sequence characteristics. Then the mapping table was used to describe the timing characteristics of the main alarm information. After analyzing the timing characteristics of the main alarm information, the timing matching and disposal of the main alarm information in the hydropower centralized control platform were realized. Experimental results show that the model has good visualization ability of main alarm information, and the coverage rate of main alarm information crawled by the model is up to 98.99%. The model has higher Pearson correlation coefficient and better ability to deal with the main alarm information.

For the pressurized water supply project of a long distance, large flow and high lift pumping station, the pump trip was simulated. Combined with the characteristics of the engineering terrain, the combined protection method of air-cushion surge chamber and one-way surge tank was proposed. And then the sensitivity analysis of the closing rule of the valve after the pump and the throttle orifice of the surge chamber was carried out according to the requirements of pipeline pressure control. The results show that the air cushion surge chamber could effectively protect the water hammer of the pump trip and the water hammer of valve shutdown caused by the rapid closure of the pump valve. The one-way surge tank solved the problem of local high pressure caused by the continuous water refill of the air cushion surge chamber, and protected the safety of the high point pipe section. The combined protection scheme could significantly reduce the volume of air cushion surge chamber and saved the engineering cost. In addition, the closing rule of the pump valve and the throttle orifice area of the air cushion surge chamber has a great impact on the water hammer pressure of the pipeline. Too fast valve closing or too large throttle orifice area will lead to the positive pressure of the pipeline exceeding the standard. Too slow valve closing or too small throttle orifice area will lead to large negative pressure in the pipeline. The specific project needs to be optimized in combination with transition process simulation. For this project, after simulation and optimization, the diameter of the throttle orifice was 0.8m, and the valve of the pump was closed by 5s straight line, and the results met the requirements of regulation guarantee calculation.

The mechanical properties of hydraulic concrete are an important influencing factor on the stability of hydraulic engineering facilities. A fine damage intrinsic structure model considering the effect of sulfate corrosion was established using a combination of mechanical experiments and theoretical analysis. The results show that the effect of sulfate corrosion increases the damage degree of concrete after damage. With the increase of corrosion time, the compressive strength and elastic modulus show an exponential decay law, and the damage strain tends to increase. From the experimental results, the shape parameter m and scale parameter ε₀ are calculated. Besides, the mesoscopic damage constitutive model considering the effect of sulfate corrosion is solved. The reasonableness of the theoretical model for predicting the stress-strain relationship was verified by experimental data. The constitutive model proposed in this study can provide scientific reference for the accurate prediction of mechanical behavior of hydraulic concrete.

By investigating the historical meteorological data, disaster situation data and disaster bearing body information during 1951-2020, this paper establishes a risk survey database to accurately evaluate the hazard of rainstorm disaster in Changsha County of Hunan Province. Comprehensively considering the impact of multiple meteorological disaster causing factors of rainstorm disaster and inducing environment such as geology and drainage network of watershed, this paper carries out the analysis of basic characteristics of rainstorm and risk assessment of disaster, and forms a risk assessment model. Geological disasters in Changsha County mainly occur in the northeast of Changsha County. The urban waterlogging disaster mainly affects the county seat and the surrounding areas with high urbanization. Mountain torrents mainly affect the central and northern areas of Changsha County. The risk of rainstorm disaster in Changsha County tends to weaken from the southeast and northeast to the middle. Generally speaking, the risk of rainstorm in the whole county is not high, only Kaihui Town, Gaoqiao Town and Huanghua town are high-risk, and rainstorm events are easy to cause secondary disasters in these three towns. There are two relatively high value centers in the county, which are located in Huanghua town and Jiangbei town in the southeast and Kaihui town and Gaoqiao Town in the north. The comprehensive risk level of rainstorm in Ansha Town, Guoyuan Town, Chunhua Town and urban area in the middle is low.

In order to better understand the impact of vegetation restoration on hydrological processes, the SWATMODFLOW model and dynamic HRU was coupled, and LU-SWAT-MODFLOW model was developed to accurately simulate the dynamic change of vegetation and groundwater in the lower reaches of the Bayin River Basin. The results revealed that the LAI, ET and groundwater level simulated by LU-SWAT-MODFLOW model are better; After vegetation restoration in the study area, the monthly evapotranspiration of different sub-basins increased by 0-1.5 mm, and the annual evapotranspiration increased by 0-6 mm; The average monthly groundwater recharge increased about 1.27 mm, and the average annual groundwater recharge increased 14.02 mm. The exchange of the surface water and groundwater in the study area have obvious changes in the areas where the vegetation restoration type is low-coverage grassland and bare land converted to forestland.

The underground powerhouse of Henan Wuyue Pumped Storage Power Station has a complex structure of caverns. The main powerhouse has a maximum span of 26.0 m and a height of 55.1 m, which is a large underground chamber. The rock mass structural planes are developed and the strength is low. The fault F1 runs through the three powerhouse, and the safety problems are prominent. The stability of surrounding rock after excavation should be analyzed. Therefore, FLAC^3D program was used to establish the geological model. The BSA-BP neural network was used to calculate the initial in-situ stress field of the area. And then the excavation of underground powerhouse was simulated. The stress field, displacement field and plastic zone development and distribution law of surrounding rock were analyzed. The results show that the surrounding rock of underground powerhouse caverns group is basically stable. However, local deformation and failure may occur in the fault development area and at both ends of the busbar hole. The research results can provide guidance for the design and construction of the project, and provide some reference for similar projects.

The purpose of the paper is to explore connection mechanism between interval time and pressure at draft tube inlet in successive load shedding case. Based on transient flow theory and method of characteristics, numerical simulation calculation of transition process in the successive load shedding case for pumped storage power station with layout of two turbines and one tunnel was carried out. The relationship between flow rate, running track of turbines and minimum pressure at draft tube inlet was analyzed. The result shows that there is a certain most unfavorable interval time making the time-domain asynchronous degree of first wave flow rate in two turbines maximized and the pressure at draft tube inlet is the minimum. At the same time, running track point of the first load shedding turbine is near the upper bending point in the inverse S-region of characteristic curve and running track point of the last one is near the lower bending point. The conclusion can provide a reference for calculation of extreme value of pressure at draft tube inlet in the pumped storage power station.

In order to deeply understand the impact of the alteration of different opening angles of the two stage flap valves on outflow, a two- stage flap valve of a certain pumping station was taken as an example. Choosing four opening angle schemes widely used in practical projects, the three-dimensional flow pattern behind the two stage flap valve under different flow rates was simulated. The influence of flow streamline, velocity uniformity and hydraulic loss in culvert on the flow pattern was analyzed. The results show that the resistance loss coefficient along the outlet culvert is inversely correlated with the opening angle, to be specific the larger the opening angle of the flap valve, the less the hydraulic loss of the water flow in the outlet culvert pipe, and disparity degree becomes more obvious with the increase of the flow rate. When the flow rate is 2 m³/s, the hydraulic loss of the outlet culvert pipe in scheme 4 decreases by 49.6% compared to that of scheme 1; When the flow rate is 16 m³/s, the hydraulic loss of the outlet culvert pipe in scheme 4 decreases by 79.1% compared to that of scheme 1. To conclude, the larger the opening angle of the flap valve, the better the flow pattern in the culvert and when the flap valve is opened to 46°for the upper flap valve and 64°for the lower flap valve in scheme 3, the flow pattern in the culvert has tended to a better state.