Abstract:The achievements made since the introduction of the river and lake chief system were summarized. The reasons for the success of China’s river and lake chief system were analyzed from the aspects of national and local policy promulgation, regulation formulation, standard implementation, and professional support. The effectiveness of standardized management was proved by the cases of three typical demonstration construction areas in Shaoxing City, Fujian Province, and Jiangsu Province. The deficiencies of standardized management of river and lake chief system in policy innovation, enforcement of laws and regulations, and public participation were further explored, and relevant implementable suggestions were put forward from the three aspects of strengthening top-level design, improving assessment and evaluation, and improving water control ability.

Abstract:To improve the monitoring efficiency of water noise on the operation status of overflow facilities, it is necessary to clarify the formation mechanism of water noise and its relationship with the operating and structural parameters of overflow facilities.The formation mechanism and influencing factors of water noise of common overflow facilities of river channels and hydropower stations were analyzed and summarized. It is concluded that the characteristics of water noise of common overflow facilities are closely related to their operating conditions and channel structure characteristics. The flow velocity and flow rate are positively correlated with the noise level of water flow. The more complex the flow channel structure is, the more intense the flow turbulence is and the more complex the formation mechanism of water noise will be. The water noise level and frequency of overflow facilities change synchronously with the hydrodynamic characteristics and structural boundary characteristics of the passage, which can be used as the state signal source for the operation of overflow facilities. Monitoring the operation state and safety in real time can ensure the safety of overflow facilities.

Abstract:Taking the control basin of the Kenswat hydrological station of the Manas River as the study area, considering the frequency structure characteristics under variation conditions, the joint distribution of flood peaks and flood volumes was established based on Copula function, and the risk probability under the interaction between each flood peak and flood volume was calculated to build the risk assessment model. The results show that the mixed distribution can better reflect the frequency distribution of flood variables under the condition of variation. The flood combination characteristics can be well described by the joint distribution of flood peak and flood volume based on Gumbel Copula function. Under the 500-year flood control design standard of the Manas River flood peak and flood volume, the joint risk and co-occurrence risk both reach the minimum value, and the probability of flood occurrence is low. Therefore, the design standard of flood peak and flood volume with relatively close frequency can not only ensure the low risk rate of flood occurrence, but also meet the actual needs of project hazards.

Abstract:To study the influence of the main tributaries in the lower reaches of the Jinsha River on the water temperature of the main stream, the measured data of flow and water temperature at 16 stations in the lower reaches of the Jinsha River were selected. The discharge proportions of each tributary in the lower reaches of the Jinsha River were statistically analyzed, and the water temperature change regularity of the main stream in the lower reaches of the Minjiang River, Jialing River, Wujiang River and other large tributaries after confluence was discussed. The results show that the Minjiang River, the Jialing River and the Wujiang River accounts for 18.8%, 14.2% and 10.79% of the flow discharge at the Yichang Station respectively. The change rule of water temperature downstream the main stream of Jinsha River is basically consistent with that of the tributaries, and the lag effect is gradually obvious with the increase of distance. The Minjiang River has the largest impact on the water temperature in the main stream, followed by the Jialing River and the Wujiang River. Through the linear function fitting method, the correlation coefficients of the temperature difference between the main stream and tributaries of the Minjiang River, the Jialing River and the Wujiang River and the temperature difference along the upstream and downstream of river confluences are 0.950 2, 0.884 5 and 0.786 3 respectively.

Abstract:In order to solve the problem of large number of factors, multicollinearity between factors and spatial correlation among measuring points in the spatio-temporal monitoring model of super-high arch dams, the kernel independent component analysis (KICA)method was used to extract independent components based on the prototype monitoring data of dam deformation, and the information of multiple measuring points was transformed into a few comprehensive indicators. On this basis, the support vector machine (SVM) model was optimized by using the advantages of grey wolf optimization (GWO) algorithm with good convergence speed and solution accuracy in parameter optimization. The extracted independent components were substituted into the SVM model optimized by GWO algorithm, the regression prediction on the spatial measuring points of the super-high arch dam was performed, and the KICA-GWO-SVM spatio-temporal monitoring model for super-high arch dams was constructed. Analysis of engineering examples shows that, compared with the multiple regression model, BP model and SVM model, the KICA-GWO-SVM spatio-temporal monitoring model has strong nonlinear expression ability and good performance, which can reduce the influence of multicollinearity on dam deformation monitoring, and the fitting and prediction accuracy of the deformation sequence of super-high arch dams is excellent. It can more accurately and comprehensively grasp the overall spatio-temporal deformation behavior of the dam.

Abstract:To investigate the far-field propagation characteristics of three-dimensional impulse waves generated by subaerial landslide, a three-dimensional landslide-generated wave model was established using FLOW-3D. The process of the landslide mass impact with water splash followed by landslide-induced wave generation and propagation were investigated under the condition of slides with different thickness, width and variable entry speeds. The results show that the landslide wave propagation keeps stable beyond a distance of 7 times of water-depth from the slide entry point. The dimensionless wave height and wave period are determined by the Froude number of landslide mass, the dimensionless motion time and the landslide body size. The energy conservation rate from the landslide to the far-field wave fluctuates from 8.0% to 19.7%.

Abstract:The pressure process line at typical sections of a siphon outlet was measured by physical experiment. Pressure pulsation of the siphoning formation process was obtained by the neighborhood average method, and the statistical characteristics and short-time Fourier transform signal processing method were conducted to systematically analyze the universal change law for time-averaged pressure and pressure pulsation. The results show that the time-averaged pressure on the wall, along the flow direction, first decreases and then increases. The time-averaged pressure on the upper wall of the hump segment changes with the flow rate and is gradually greater than that of the lower wall. The pressure pulsation in the process of siphon formation has a positive skew distribution, and the quadratic mean deviation keeps decreasing along the direction of the flow. The pressure pulsation in the process of siphon formation is composed of the rotation of the pump and the movement of water-air, which has a frequency between 0 and 30.Hz, with the dominant frequency close to the rotation frequency. Compared to the entrainment stage and siphoning flow stage, a significant increase in pressure frequency and amplitude occurs in the purging stage, which is close to the natural frequency of pumping station, leading to structural vibration. Design and operation should be optimized to reduce the duration time of the purging stage.

Abstract:In order to study the effect of mineral admixtures on the compressive properties of steam-cured concrete, the acoustic emission test under uniaxial compression was carried out for concrete with different curing regimes and mix ratios, and the damage evolution characteristics of concrete were explored by using acoustic emission signal parameters and Gaussian mixture model. The research shows that the compressive strength of steam-cured concrete is generally lower than that of standard-cured concrete. The addition of mineral admixtures can compensate for the strength loss caused by steam curing, and the compensation effect of adding fly ash and mineral powder is the best. The tension failure always dominates the whole compression process, while the shear failure proportion increases with the loading time. Among the acoustic emission parameters, the accumulative ringing count, the change range of b value and the proportion of shear failure forms are all negatively correlated with the compressive strength value, which can be used as important parameters to evaluate the compressive performance of concretes.

Abstract:Aiming at the status that the relevant theoretical research of aerated jet flushing to solve the problem of local sediment deposition is not deep enough, the dynamic characteristics and sand flushing effect of aerated jet were studied by flume experiment. In the gas water clear water test, four stages of plume development are proposed. Through the signal-to-noise ratio analysis of orthogonal test, it is found that the air pressure is the main factor affecting the undercut length of the plume, and the local turbulence intensity increases with the increase of air jet pressure, and decays rapidly along the transverse direction. In the pneumatic sand flushing muddy water test, three development stages of sand flushing pit are proposed. Through the signal-to-noise ratio analysis of orthogonal test, the main effect affecting the sand flushing effect is determined. The regression equation of sand flushing effect is established by variance analysis, and the comparison between predicted and measured values shows good prediction results of the regression equation.

Abstract:Aiming at the problem of ice conditions in winter for the Middle Route of the South-to-North Water Diversion Project, taking the Hebei section of the project as the research object, the formula of overall total heat variation of canal sections of the target unit was derived through the theory of heat balance. The single factor local analysis method was used to select the evaluation index. Then, based on the idea of probability theory, the joint density function between evaluation indexes was built, and the probability of meteorological events, change rate of total heat change, the risk level of ice conditions was correlated, so as to carry out the risk assessment of ice conditions in channels. The risk analysis results of ice conditions in Hebei section of the Middle Route of South-to-North Water Diversion Project from January 6th to 8th in 2021 show that, in the whole process of heat exchange, the short-wave radiation, evaporation and convection are the main factors, and the heat loss in the channel at nights is significantly greater than that in the daytime, which increases the risk of sudden ice conditions at nights. In addition, although the risk level of Shahe gate-terminal section is the same as that of other sections, its heat loss per unit area is obviously higher than that of other sections, and it is close to extremely high risk. In practice, real-time monitoring should be strengthened and relevant protection measures should be taken for this section.

Abstract:The two important hydropower development bases in Sichuan, the Yalong River Basin and Dadu River Basin, were taken as examples to construct a comprehensive evaluation system for the degree of hydropower development, in which the spatial cluster analysis method was adopted using the statistical data of water resources and hydropower. The spatial relations between upstream and downstream and the overall level of watershed hydropower development indicators were combined based on watershed segmentation. The impacts of different hydropower development degree on ecological environment were analyzed considering the data of development plans, soil erosion, geological hazards, water quality monitoring and fishery resources. The results show that the spatial heterogeneity and local agglomeration of indicators, such as hydropower development density and hydropower development intensity, are obvious. The hydropower development intensity and the total installed capacity of the basin show a significant correlation with the change of the land use type in the reservoir area. The hydropower development indicators of different grades also show significant differences, indicating the rationality of comprehensive evaluation system for hydropower development.

Abstract:In order to realize the rapid and accurate detection of hydraulic concrete cracks, a semantic segmentation method based on improved Deeplab V3+ network is proposed. In this method, the Mobilenetv2 network is used to replace the original backbone network, and the hole convolution of the hole convolution pyramid pooling module (ASPP) is replaced by the hole depth separable convolution, so as to improve the operation speed, reduce the sampling multiple of deep features and decrease the loss of semantic information. The experimental results show that the frame rate can reach 51.11 frame/s, which is 23.33 frame/s higher than that of the original network, and the reasoning speed is greatly improved. The mean intersection over union and mean pixel accuracy are 89.45 and 95.19, respectively, with high segmentation accuracy. The segmentation effect of typical concrete cracks is also better than the comparison method, indicating a strong generalization ability.

Abstract:In order to solve the problem of low efficiency of traditional manual inspection, artificial intelligence and computer vision technology was combined to propose a pixel-level refined automatic identification and segmentation method for concrete dam cracks under complex backgrounds.To overcome the interference of complex environmental background factors, the concrete dam crack image is preprocessed based on various digital image processing methods to effectively remove environmental noise. Based on the Mask R-CNN instance segmentation model, the model backbone network is optimized to improve the crack feature extraction ability. In the experiment, 500 images of concrete dam cracks, including single crack, multiple cracks, cross cracks, map cracks and other crack forms, were collected for model training and verification. A combination of qualitative analysis and quantitative evaluation was used to evaluate the generalization ability and robustness of the model in multiple dimensions. The test results show that the improved Mask R-CNN model in this paper has a good effect on crack image recognition with various crack features and noise backgrounds. The average accuracy values of the model’s target detection and mask segmentation on the test set are 76.3 and 61.9, respectively, which can meet the requirements of high-precision fine segmentationfor cracks. Compared with benchmark models such as Cascade-Mask R-CNN and Yolact++, the improved Mask R-CNN method has certain advantages in object detection, mask segmentation accuracy and model inference speed.

Abstract:Aiming at the problem that the failure state of concrete is complex and changeable, and the acoustic emission(AE) signal is difficult to be separated from the background noise, the function of complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) method was coupled with the support vector machine (SVM) method to identify and predict the concrete destructive AE signal. Firstly, the CEEMDAN method is used to decompose the acquired AE signal, obtaining a certain number of adaptive characteristic modal components (IMF). The correlation coefficient between each component and the original AE signal is calculated, and the IMF component containing more information about the original AE signal is preferred. Secondly, the energy coefficient and waveform coefficient of each component eigenvalue are calculated and inputted into the SVM respectively to classify and identify different failure states of concrete. The results show that the prediction rate of energy coefficient as eigenvalue is 92.39%, and the prediction rate of waveform coefficient as eigenvalue is 91.30%.

Abstract:The influence of the modulus, dosage of the modifier and curing age on mechanical properties, mineral component, microstructures and hydration products of modified sludge from reservoirs in the Yellow River Basin were investigated using mechanical strength test, XRD, FTIR and SEM technique. The results show that the modulus, dosage and curing age of the modifier have significant impacts on the mechanical properties of the solidified sludge. The compressive strength of the specimen increases with the modifier dosage and curing age, and the maximum value of compressive strength is 7.13 MPa. The results of XRD, FTIR and SEM show that flocculent geopolymer gel can be formed by the reaction of clay minerals and the modifier, and the material structure became more compact and uniform.