Abstract:By systematically reviewing the current research of river regulation, the research situation and development tendency on the issue of hydraulic geometry related to alluvial river adjustment, channel adjustment process under different boundaries and the alluvial river linear theories were comprehensively discussed. The following problems should be focused on in the adjustment of wandering channel in lower reaches of Yellow River under new situation, including the coupling effect of flow and sediment change and limited control boundary on river regulation, the section shape assumption in the mathematical analysis of channel section self-adjustment, and the main channel oscillating amplitude and its frequency on the wandering river under partly controlled boundaries. Further study on these issues is not only helpful to deepen the understanding of wandering river fluvial process, but also has significant theoretical and practical values in prediction of river channel adjustment trend and river regulation.

Abstract:To improve the accuracy of the mediumlong term runoff forecasting of the whole watershed, a combined method integrating information entropy and improved extreme learning machine (ELM) is proposed. Firstly, the comprehensive runoff index is constructed based on the controlling area of different hydrological stations to characterize the abundance and drought in the basin. Secondly, the partial mutual information (PMI) approach is applied to calculate the correlation between multiple factors and the comprehensive runoff index for inputs of the forecasting model. Finally, an improved ELM model by combining Kfold cross validation with improved particle swarm optimization (IPSO) is proposed to optimize parameters of ELM, together denoted as IPSOELM, for mediumlong term forecasting. In a case study of the Yalong River basin, the proposed model was compared with classical forecasting models, i.e., backpropagation neural networks (BPNN), support vector machines (SVM), ELM and PSOELM models. The results shows that the performance evaluation indexes of the proposed model perform much better than the above four datadriven models in terms of Emape, Ermse, Edc, Eqr, and Ere. The five forecasting models demonstrate better results for the D1 dataset compared to that of the D2 dataset.

Abstract:Based on the interval analytic hierarchy(IAHP)method and the extended approximation ideal solution sequencing(TOPSIS)method, a reasonable real-time security risk identification model was established. The proposed model was employed in the risk analysis of a large-scale water diversion project near the urban tunnel section. The multiple-index decisions were made on the number of safety risk intervals at different construction stages. According to the engineering data of the corresponding stage, the safety risk factors are sorted. The feasibility and effectiveness of the real-time security risk identification model was tested.

Abstract:The trigger factors and rules of safety accidents of Russia’s hydraulic structures from 2009 to 2019 were analyzed, and the current situation and main characteristics of safety supervision were also studied. Compared with 2009, the total number of hydraulic engineering constructions and the number of ownerless water resources constructions decreased by 37. 8% and 50%, respectively in 2019. The proportion of water resources constructions in the total number of hydraulic engineering constructions increased from 78. 9% in 2009 to 94. 2% in 2019. The accident occurred sporadically with time. Dam break accidents caused by overtopping and piping accounted for 80% of the total accidents, and the dam break rate was 0. 0143% in 2017. About 40% of the accidents occurred in the Southern Federal District. About 80% of the hydraulic engineering constructions in accidents were small and medium-sized reservoir dams. The main factors leading to the accidents were human unsafe behavior and management loopholes.

Abstract:Systematic indoor physical model experiments of a flat flume system were carried out to explore the influence of inland fresh water discharge on seawater intrusion in coastal reservoirs. The results show that a logarithmic decrease relationship between the invasion length of the lower saltwater wedge and the discharge of inland fresh water exists. The decrement of the invasion length of the lower saltwater wedge decreases with the increasing fresh water discharge. Compared with the groundwater, the surface water has a more significant inhibition effect on seawater intrusion in coastal reservoirs. When the discharge of inland fresh water increases, the salinity decreases at the bottom of coastal reservoirs, and the upper saltwater wedge decreases and disappears earlier than the lower saltwater wedge. Reduction of groundwater exploiting and application of water transfer into the reservoir can suppress saltwater intrusion and relieve watersalinization.

Abstract:In order to accurately evaluate the thixotropy of Zhanjiang Formation clay, based on the fuzzy mathematics theory and according to the influencing factors of clay thixotropy, a fuzzy comprehensive evaluation factor set of clay thixotropy strength was constructed with clay content, pore ratio, plasticity index and sensitivity as indicators. A comprehensive evaluation set of clay thixotropy strength and the grade standard of thixotropy strength evaluation index were established. The membership degree and weight of each index were calculated by using the fuzzy comprehensive evaluation method, and the classification standard for the strength of thixotropy of clay was established. The thixotropy strength of structural clay of Zhanjiang Formation was graded by using this standard. The results show that strong structural clay of Zhanjiang Formation under each sedimentary facies has strong thixotropy, and the thixotropic strength from strong to weak is in the order of Leinan fluvial facies, neritic facies, estuarine facies and Leibei fluvial facies.

Abstract:DEM data and GIS spatial analysis technology were used to construct a flood and inundation analysis module. Polder areas were generalized into a zero-dimensional storage unit to realize elaborate simulation of polder areas. Coupled with the refined hydrological and hydrodynamic model of the Taihu Basin, a reliable flood inundation simulation model was established. The flood event occurred in 2016 was selected for model verification. Comparison of water levels and real flood inundation distribution between the simulation and observation from the Taihu station and other representative stations shows that the constructed model is reliable. The verified model was used to simulate the flood inundation of the Taihu Basin under the scenario of plum rain encountering typhoon rainstorm. The simulation results are scientific and reasonable, which can provide technical support for basin flood risk management.

Abstract:Using the realizable k-ε turbulence model and the water-gas two-phase flow mixing model, the flow in a curve-floor stepped tunnel with pre-sudden lateral enlargement and bottom drop aerator under different flow rates was numerically simulated, and the distribution rule of aeration concentration in the side wall, bottom plate and flow of the curve-floor stepped tunnel was obtained. The results show that the cavity created by the pre-sudden lateral enlargement and bottom drop aerator is consistent with the test results. The calculated value of the aeration concentration at the measurement point is greater than the test value, but however, the calculated and measured values both increase with the discharge. When the discharge per unit width is greater than 28 m²/s, stable side and bottom cavities through sudden lateral enlargement and bottom drop aerator can be formed. During the flow passing through the step, the aeration effect gradually develops from the surroundings to the inside, and finally a uniform aeration water flow is formed. The joint effect of the sudden lateral enlargement and bottom drop aerator and stairs in the connection section can effectively increase the aeration concentration of the water flow at the bottom and side walls. When the discharge per unit width is 54 m²/s, the aeration concentration of the aeration uniform water flow at the end of the connection section can reach 20%. The provision of pre-sudden lateral enlargement and bottom drop aerator can effectively increase the aeration concentration of the ladder energy dissipator under large discharge per unit width, and can reduce the risk of cavitation damage in flood discharge structures.

Abstract:Based on the CFX solver, aiming to improve the negative flow patterns in the sumps of a small sluicelateral pumping station with navigation function, numerical orthogonal simulation tests of the airfoil deflectors were carried out. The results show that if there are no rectifying measures, the flow pattern in the sumps is disordered with large recirculation zones from the No.1 to the No.3 sump. The velocity distribution is not uniformandthe axial velocity distribution uniformity is only 76.84%. By arranging four airfoil deflectors with elevation angles of 25° at 1D away from the entrance of the sump, the recirculation zones basically disappear. The velocity distribution is modified and the axial velocity distribution uniformity is 90.2%, increased by 13.36%, with a more uniform and symmetric flow pattern. The airfoil deflectors can eliminate the recirculation in the sump so that the stream is forced to flow along its pressure and suction surface, and the uniformity of the velocity distribution is improved.

Abstract:According to the related concepts of cloud model and the limited interval theory, the comprehensive evaluation method based on combination weight and improved cloud model is adopted to solve the problems of single result of benefit evaluation, randomness and fuzziness of index evaluation of the Eastern Route of South-to-North Water TransferProject. The method combines the weight obtained by G1 and improved CRITIC weight method with the index membership degree obtained by the improved trapezoidal cloud model to realize the comprehensive evaluation of the project benefits. Taking the first phase of the Eastern Route of South-to-North Water Transfer Project in Jiangsu as an example, the influencing factors of project benefit evaluation were classified from cost analysis and benefit analysis, and the engineering benefit evaluation index system was constructed, including six aspects of fixed investment, annual operation cost, working capital, economic benefit, social benefit and ecological benefit, containing a total of 20 indexes with determined hierarchical standards. The effectiveness and applicability of the proposed evaluation system and method for the Eastern Route of South-to-North Water Transfer ProjectinJiangsu were verified.

Abstract:The rock mass alteration zone developed in the high sidewall and rock wall crane beam of the Yangfanggou large underground powerhouse seriously affects the stability of surrounding rocks and structures. Firstly, the macrogeological conditions, monitoring deformation characteristics, acoustic wave detection data and rock mechanics tests of the surrounding rock affected by the alteration rock were analyzed, and a method of rock mass quality zoning and comprehensive evaluation of rock mass mechanical parameters based on the rock Pwave velocity was proposed. Simultaneously, the spatial division and evolution characteristics of the unfavorable geological body were also identified, which can combine the detection results with numerical simulation technology quickly, dynamically and quantitatively. Then, by constructing a reliable numerical model, quantitative analysis and evaluation of the adverse effects of the rock alteration zone were carried out, and the safety warning standard during construction was proposed. The results provide support for reasonable construction plans and active protection and reinforcement measures.

Abstract:The fracture mechanics theory was used to analyze the actual energy release rate at the tip of cracks in the material considering creep deformation. The strain energy accumulation law of microcracks in concrete under continuous loading was investigated and it is concluded that the microcrack extension evolution state is the same under long-term continuous loading and uniaxial loading with the same strain energy accumulation. This model is in good agreement with the results of non-linear creep tests on concrete of different strength classes. The coupling mechanism between concrete damage and creep can be reflected.

Abstract:Associated research involving river sand mining management wassorted out and reviewed from the perspectives of river sand ownership definition, sand mining planning and permit selection, sand mining trading methods exploration, solutions to illegal sand mining behavior and informational sand mining management construction. Comprehensive analysis indicates that unclear representation of ownership subject exercises the absence of sand mining management responsible body. The lack of internal mechanism between sand mining impacts and sand mining planning restricts the scientific decision-making of sand mining planning schemes. Understanding about applicable conditions of different sand mining trading methods in existing research is deficient. At the same time, new generation of information technology owns great potential for use in sand mining management. Based on above, the following problems can be tried to be studied in the future, including sand mining management system after institutional reform, comprehensive evaluation and decision-making of sand mining planning schemes, innovative design of sand mining trading methods, and construction of a whole process oriented digital intelligent platform for sand mining management.

Abstract:The research status associated with landslide time prediction was comprehensively reviewed. The current approach employed in the time of slope failure prediction were generalized as regression models based on empirical formula and mathematical theory respectively. In addition, the applicability of each model and method as well as the relevant prediction criterion and warning threshold were briefly analyzed. In order to acquire more accurate results, it is indispensable to establish an approach that can describe the evolution process of landslide and the mechanism of failure on the basis of in-depth study of landslide types, geological characteristics, and deformation characteristics combined with appropriate criteria and early warning threshold.