In order to solve the problem that the new hydraulic gate is difficult to manufacture experiment and debug in the real environment, the historical gate operation data was analyzed and transmitted based on the digital twin simulation platform. The designed gate was analyzed through numerical simulation, and the overall stress and deformation changes of the gate with different sub-gate opening degrees under hydrostatic pressure were analyzed. At the same time, the overall vibration frequency changes of the gate under the action of air and fluid-structure interaction were analyzed. The flow state of the fluid domain at the sub-gates with different opening degrees was simulated. The results show that with the increase of the opening of the sub-gate, the stress value of the gate varies from 58 MPa to 67.5 MPa, and the deformation change is not obvious; Compared with the natural vibration frequency of the gate in the air, the fluid-structure coupling effect will appropriate reduce the natural vibration frequency of the gate; Different sub-gate openings will affect the flow state of the fluid domain, and increasing the opening will reduce the water velocity. The results provide some references for its actual operation, maintenance and optimization of gate performance.

The Wangyu River is an important watercourse connecting the Yangtze River and Taihu Lake. Relevant hydrological data shows that the pumping opportunity can account for 25.9% of the total drainage period from the Wangyu River to the Yangtze River, which indicates that the pumping station plays a crucial role in the drainage period of Taihu Basin. The current design lift (2.5 m) of the pumping station is higher than the actual operating lift, and the running time of the pumping station exceeding 20% of the installed designed capacity accounts for 65.9% of the total operation time. According to the design specifications of the pumping station and relevant local standards, combined with the analysis of the hydrological data, it is recommended to adjust the design lift of the pump station to 1.78 m in the subsequent upgrading of the pumping station. The optimized design lift is more compatible with the actual operating environment of the pumping station, and it also reduces the operating costs of the pumping station such as power consumption, and prolongs the service life of equipment, which is of great significance for the overall benefits of the Wangyu River Hydro-junction.

In order to study the shear resistance of the inclined section of steel fiber reinforced concrete beams with BFRP bars, this paper takes the steel fiber reinforced concrete beams with BFRP bars as the research object, and carries out the shear capacity tests of 9 steel fiber reinforced concrete beams with BFRP bars. The effects of failure mode, shear span ratio, BFRP reinforcement ratio, steel fiber volume fraction, and steel fiber range on the shear resistance of steel fiber reinforced concrete beams with BFRP bars are analyzed. The results show that the failure mode of steel fiber reinforced concrete beams reinforced with BFRP is mainly shear failure; The shear capacity of the inclined section decreases with the increase of shear span ratio, and increases with the increase of fiber content and BFRP reinforcement ratio; Setting steel fiber within the shear span of the support can better improve the shear resistance of the inclined section of the concrete beam with BFRP reinforcement. Finally, the formula for calculating the shear capacity of steel fiber reinforced concrete beams with BFRP bars is obtained by fitting test data, and the calculated results of the formula are consistent with the experimental results. The research enriches the design theory of inclined section of FRP reinforced concrete composite structure, and has reference value for the application of FRP reinforced steel fiber concrete composite structure in practical projects.

As an essential influencing factor of permissible pollution bearing capacity, hydrological condition was changed significantly due to hydropower cascade development. According to the water functional division and water quality control target in Panzhihua reach of Jinsha River, the variation of dynamic permissible pollution bearing capacity (COD, NH3-N) with hydropower cascade development were calculated depending on 2-D hydrodynamic and water quality models. Furthermore, response relationship between permissible pollution bearing capacity and hydrological factors was established to evaluate the effect of hydropower cascade. The results show that the dynamic permissible pollution bearing capacity of COD and NH3-N decreased by 5.2%-27.8% and 3.8%-41.2%, respectively, and its decreased range was found to be more evident in dry season. The variation trend of permissible pollution bearing capacity and near-bank discharge was similar for different conditions. Simple coefficients between the variation of near-bank discharge and permissible pollution bearing capacity were calculated. However, a significant correlation was found with permissible pollution bearing capacity of NH3-N only.

Based on the understanding of the concept of happiness river, taking 6 rivers with moderate river scale in Qiqihar Areas as an example, the TOPSIS evaluation model is constructed by combining the proportional scale AHP and AEM to carry out the evaluation on the happiness river, whose goal was divided into 5 guiding layers and 20 indicator layers. The evaluation results show that the overall happiness of the rivers in Qiqihar Areas is grade Ⅲ, which the happiness of Yalu River is grade Ⅳ, the happiness of Alen River, Nuomin River, Yin River and Runjin River is grade Ⅲ, and the happiness of Chaoer River is grade Ⅱ. In addition, the common problems of poor evaluation grade in the results were analyzed and the treatment suggestions were put forward.

Aiming at the problem that the traditional water quality prediction method is difficult to capture the spatial and temporal characteristics of the sample, this paper proposes to establish a CNN-EA-ConvLSTM based water quality prediction model. The convolutional neural network (CNN) was used to reduce the dimensionality of the data and extract the sample features. Then the hidden information among samples was explored by the external attention mechanism. The convolutional long and short-term memory network (ConvLSTM) was further used to capture the spatial characteristics of the data. To achieve optimal results of the model, a genetic algorithm was used to optimize the parameters of the model. The water quality test data of Qinghai Province was used as a sample to simulate and validate the model. The results show that the mean absolute error (M_MAE) of the model is 0.063, the root mean square error (R_RMSE) is 0.012, and the mean absolute percentage error is 2.6%, which are respectively reduced by 18% and 24%, 14% and 25%, 16% and 21% compared with the CNN-EA model and CNN-LSTM model. Therefore, the model can effectively obtain the spatial and temporal characteristics of water quality, attenuate the influence of different samples, and achieve the ideal prediction effect.

In view of the serious problem of scouring under the sluice gate of the Tidal River, taking the Shanghai area as an example, from the perspective of operation and maintenance management, the scouring mechanism under the sluice and the optimization method of operation and maintenance management were explored. Through the flow state analysis and hydraulic jump formula derivation, the variation law among the water level, the critical water depth of the outer river and Froude number in front of hydraulic jump was revealed. The water level solution formula suitable for the operation and maintenance management of the tidal estuary gate was proposed. The results show that the water level of the outer river fluctuates greatly because the tidal estuary sluice is affected by tidal action; When the water level of the outer river is lower than the critical water depth, it should be prohibited to open the gate; When the Froude number in front of the hydraulic jump section of the outer river level is between 4.5 and 9.0, the drainage of the gate can be effectively exerted, and the erosion under the gate can be effectively reduced. The results can provide a reference for the operation and maintenance management of similar tidal estuarine gates.

To determine the appropriate ecological flow for small watershed assessment, taking Qingshui River in Pearl River Basin as an example, the monthly ecological flow was calculated by using six hydrological methods such as Tennant method, Texas method and frequency curve method. Furthermore, combined with hydrological rhythm and ecological flow guarantee rate, the advantages and disadvantages of the six methods were compared and analyzed in the dry and flood periods, and the most suitable ecological flow calculation method for small watershed was obtained to determine the ecological flow. The results show that the ecological flow of Hongqi Reservoir section is between 0.12-1.52 m³/s, and the ecological flow of Puzhehei section is between 0.30-4.95 m³/s. The fitting coefficients of hydrological rhythm are 0.993 and 0.998, respectively. The ecological flow guarantee rate is at a good level, and the ecological flow selection result is reasonable. The results can provide a reference for similar national small watersheds to select appropriate calculation method to determine the ecological flow.

The three-dimensional seepage analysis and control of underground plants and complex tunnels are related to the long-term seepage safety of underground spaces, which is one of the key technical issues facing the construction of pumped storage power stations by abandoned coal mines. Considering the reinforcement schemes for different surrounding rocks of the lower reservoir, the spatial location of the upper reservoir, the main powerhouse and the coal mine extraction area, a refined three-dimensional finite element model for seepage analysis of complex underground space in Longdong coal mine was established. Three-dimensional seepage field analysis was carried out for typical working conditions during the construction and operation periods. Important design parameters such as external water pressure and seepage volume of the underground tunnels during the construction and operation periods were obtained. Refined simulation of the numerous drainage holes in pumped storage power stations was implemented. By calculations of the seepage field under various unfavourable conditions, the optimal spacing of the drainage holes was determined. The research results are of great significance in the evaluation of seepage safety and the design of underground roadway protection schemes for the construction of pumped storage power stations by abandoned coal mines.

The common deformation and failure mechanism of retaining wall at foot of earth-rock dam is mainly caused by insufficient bearing capacity of foundation, uneven settlement of foundation, temperature effect or insufficient anti-sliding stability. For a certain project, the retaining wall deformation characteristics are not consistent with the above causes after the drainage of the embankment foot of the earth-rock dam is changed to the retaining wall. The deformation is only visible at the expansion joints of the retaining wall, and the expansion joints are open, closed or misplaced. Through calculation and analysis, it is found that the expansion joint deformation is caused by the retaining wall horizontal displacement caused by the consolidation settlement of the dam, and the size of the deformation is related to the horizontal displacement difference between adjacent retaining walls. The larger the displacement difference is, the more serious the deformation is. At the same time, the horizontal displacement of retaining wall is related to the height of dam section, hydrogeologic conditions of dam foundation. Based on this, it is proposed that after the prism drainage of the downstream earth-rock dam is changed into gravity retaining wall, in addition to the design and calculation according to the standard requirements, the horizontal displacement difference between retaining walls should also be calculated, and the damage of retaining wall displacement and poor drainage to the downstream drainage system of the dam body should be considered. The research results have a good reference value for the correct analysis of deformation mechanism and anti-slip design of retaining wall at dam foot.