Abstract:In this study, the hydrological trend of the Huangjiagang hydro-station downstream of Danjiangkou from 1965 to 2017 was evaluated by RVA method via dividing different influence periods. The results show that the impoundment of the Danjiangkou Dam can increase the discharge in dry seasons while decrease the discharge in flood and normal seasons in the downstream. The decrease of rainfall caused by climate change leads to the decrease of the monthly mean flow and the annual maximum discharge, but the occurrence of low flow pulse is increased. The backwater of the cascade dams increases the monthly mean flow and the annual minimum discharge with earlier occurrence. The Middle Route of the South-to-North Water Transfer Project substantially reduces the monthly mean flow and the annual minimum discharge with an increase of both low and high flow pulse. The hydrological regime fluctuation in the middle and lower reaches of the Hanjiang River is induced by the different influencing periods, which affects the stability of aquatic ecosystems.

Abstract:A simulation model of WEF nexus in Heilongjiang Province was established based on the theory of system dynamics, in which the supply and demand of water resources and the production and consumption of energy and food from 2010 to 2017 were simulated. Four different development patterns were set for exploring the rational allocation pattern of water-energy-food in Heilongjiang Province. The results show that the situation of water security in Heilongjiang Province is severe. Adoption of the strictest planning pattern will lead to a most significant positive effect among the four development patterns. The consumption of energy under the enhanced development pattern is the most obvious, and the energy security of the whole province could not be guaranteed no matter which development pattern is adopted if the energy consumption is not under control. The food security of Heilongjiang Province is relatively stable and not easily affected by external conditions. The ratio of food inventory and food supply-demand balance will get maximum under the conservative saving pattern. The overall security of the water-energy-food system may not be achieved by a single development pattern.

Abstract:Aiming at the problem that the influence range for flood discharge atomization is not easy to be directly modeled by mathematical models, flood discharge from a high dam power station was taken as a study object, in which a three-dimensional mathematical model was used to calculate the hydraulic characteristic values such as the flow velocity and the jet angle into water. The empirical formula of the prototype observation was used to predict the flooding atomization range, and a physical model test was used for verification analysis. The results show that, affected by the scale effect, the influence range of the physical model atomization test is smaller than the calculation range but with a similar variation trend. The fog flow is affected by inertia and water tongue wind, revealing a climbing movement along the water tongue axis, which is consistent with the prototype measurement. Affected by the ski-jump jet at the outlet, the flood discharge atomization effect is concentrated downstream of the water tongue drop point. The upstream and right banks of the plunge pool have a small rainfall intensity with a limited influence range.

Abstract:SST k-ω turbulence model was adopted to simulate the flow characteristics of the axial-flow pump in the following four states, non-cavitation in clean water, non-cavitation in sandy water, critical cavitation in clean water and critical cavitation in sandy water. The influence of sediment concentration and cavitation on the flow characteristics of the pump was analyzed, and the unstable operating area of the axial-flow pump in different working conditions was determined. The results show that on the blade working surface, the axial flow coefficients are distributed around -1 in the non-cavitation and critical cavitation states, and the radial flow coefficients and the absolute flow coefficients are distributed in the non-cavitation state near 0. 6 and 1. 2, respectively. In the critical cavitation state, the radial flow coefficient and the absolute flow coefficient are distributed around 1. The flow coefficients at the inlet and outlet of the back of the blade are the most sensitive. Cavitation on the impeller, which has a great impact on the flow coefficient, can cause fluctuations of flow coefficients in the blade back face especially after adding sediment. Thus, the inlet and outlet on the back face of impeller are unstable due to the impacts of sediment and cavitation. When cavitation does not occur, the flow state in the impeller is basically not changed by the sediment concentration. When cavitation occurs in the pump, a flow separation vortex appears at the tail end of the blade. After adding sediment, the vortex range at the tail end can increase, and the internal flow state of the impeller is thus changed. It shows that both cavitation and sediment are the main factors affecting the flow characteristics in the impeller.

Abstract:To study the change rule of water hammer pressure produced by pressure pipes after rock plug blasting in a water intake project, based on the method of characteristics, the one-dimensional transient flow theory and the working principle of actual blasting, a mathematical model of rock plug blasting in a water intake for water conservancy projects is established combined with the requirements of pipeline safety control. The results of numerical simulation show that the pressure in the pressure pipeline fluctuates greatly after blasting, and the negative pressure is easy to cause water hammer of cavities collapsing accidents under the vaporization pressure. Therefore, additional water hammer protection measures are needed to ensure the pipeline safety. Increasing the area of the shaft can reduce the extreme value of the water hammer pressure, and the larger the area of the ventilation shaft, the smaller the pipe pressure. When the shaft diameter increases to 10. 0 m, the negative pressure value can meet the requirements.

Abstract:To study the real-time monitoring of the piping process of embankment by acoustic emission, a sand tank model test under the action of variable water head was carried out. By comparing the seepage flow, average hydraulic gradient and acoustic emission characteristics of the piping process, it is found that the hydraulic parameters and acoustic emission parameters have the same distribution law during the piping process. The b-value calculation method and the G-P algorithm are introduced to calculate the b values and the fractal dimension value D in the AE signal waveforms. The results show that the piping process can be discriminated from the magnitude and distribution of the b-value and the fractal dimension D. The damage can be reduced by in time prediction of the embankment piping damage.

Abstract:Aiming at the key technical problems of unmanned aerial vehicle(UAV)image calibration and registration, a surface flow field measurement method based on UAV self-calibration is proposed, which is based on structure from motion(SFM)3D reconstruction technology to complete the UAV image self-calibration and speed-up robust features(SURF)method for UAV image registration. The method was applied to measure the surface flow field downstream of the Sancha River Estuary Sluice in Nanjing City. The results show that the accuracy of the 3D reconstruction based on SFM can meet the requirements of self-calibration, and there is no need to set ground control points to calibrate the UAV images, which simplifies the UAV calibration process. SURF method can effectively eliminate the influence of UAV position drift on the surface flow field measurement results.

Abstract:To improve the prediction accuracy in foundation pit deformation, an improved supply-demand-based optimization(ISDO)algorithm-exponential power product(EPP)foundation pit deformation prediction model was proposed. The optimization ability of the ISDO algorithm was verified through six standard test functions and three application examples, and the results were compared with the basic supply-demand optimization(SDO)algorithm, whale optimization algorithm(WOA), gray wolf optimization(GWO)algorithm, moth swarm algorithm(MSA), and particle swarm optimization(PSO)algorithm. Taking the three foundation pit settlement predictions as examples, the autocorrelation function method and the false nearest neighbor were used to determine the delay time and embedding dimension of each instance and, construct input and output vectors to train and predict each model. The results show that the search capability of the ISDO algorithm is superior to the five other algorithms such as SDO, and it has higher search accuracy, global search capability and robust performance. The absolute value of the average relative errors predicted by the ISDO-EPP model for the three examples were 0. 73%, 3. 36% and 1. 33%, respectively, which were smaller than the ISDO-SVM and ISDO-BP model, indicating that the ISDO algorithm can effectively optimize the parameters of the EPP model and the ISDO-EPP model is feasible and effective for deformation prediction.

Abstract:Rubber particles of different sizes were used to replace sand in the concrete which was exposed to workability test, uniaxial compression test, water permeability test, chloride penetration resistance test and freeze-thaw test. The results demonstrate that the fluidity of the crumb rubber concrete is minimized at the rubber particle sizes from 0. 63 to 1. 25 mm. The compressive strength of the concrete degrades as the rubber particle size decreases, while the introduction of small rubber particles has a positive effect on the concrete integrity. There exists an optimized particle size in the range from 0. 165 to 0. 315 mm, in which the electric flux, seepage height, mass loss rate and relative dynamic elastic modulus loss rate are 53. 15%, 52. 35%, 16. 35% and 51. 79% respectively of those for conventional concrete. Additionally, the prepared simply supported beam of crumb rubber concrete according to the ratio for optimized durability has a crack initiation load higher than that of a simply supported beam made of conventional reinforced concrete, but its ultimate load is 6. 10% lower than that of the latter.

Abstract:Aiming at the problem of reliable evaluation and real-time dynamic control of compaction effect of roller compacted concrete(RCC)dam on site, a new evaluation method for compaction degree of RCC thermal layer based on Rayleigh wave velocity detection is proposed. Relying on Chebyshev type I high-pass filtering combined with wavelet threshold signal denoising method, a regression prediction model for compactness of grid surface unit sample points is established, and the entire construction area visualization evaluation of compaction quality is performed by Kriging space interpolation method. Combined with an engineering field application example, the results show that the joint denoising method can effectively suppress the interference noise at the construction site, and the calculated wave velocity value is evenly distributed. In terms of goodness of fit and prediction accuracy, the multivariate nonlinear regression model based on Rayleigh wave velocity and moisture content performs better than other comparison models. The Kriging space interpolation method is used to perform regional optimization assignments to achieve real-time dynamic control of the quality defects for the entire construction area.

Abstract:Aiming at the problem of sliding instability along slope surface during rainfall for 3D mesh flexible protection structure with reinforcement and anchorage, a stability analysis model of slope protection structure under rainfall condition was established based on limit equilibrium theory, considering the splash of rainwater and the scouring effect of flow on the slope surface. Case study was performed and the effects of slope inclination, rainfall intensity, protective layer thickness, distance between anchors and anchorage length on the stability were discussed. The results show that under rainfall conditions, the sliding force of the slope protective structure increases, the anti-sliding force decreases, and the stability of the protective structure decreases obviously. Under the same design parameters for the protective structure, the stability of protective structure decreases with the increase of slope inclination. When runoff forms on the slope surface, the influence of rainfall intensity is relatively small. Under the same slope condition, the stability coefficient of the protective structure decreases with the increase of the distance between anchors and the thickness of the structural layer, and increases with the increase of anchorage length. The distance between anchors and anchorage length have the most significant influence on the stability of protective structure. The distance between anchors should be reasonably determined by the stability analysis model proposed in this paper, and the anchorage length should not be less than 0. 5 m.

Abstract:Aiming at the complicated calculation of the double-row steel sheet pile cofferdam structure in deep silt foundation, the calculation formula of safety and stability was obtained from the aspects of anti-shear deformation stability, bottom heave-resistant stability, overall anti-sliding stability, anti-overturning stability and overall sliding stability under operating conditions based on the soil mechanics theory. In addition the minimum penetration depth of the steel sheet pile was given with mathematical theory. Taking a double-row steel sheet pile cofferdam project in Zhejiang Province as an example, according to the calculation formula proposed in the present paper, the recommended value of the minimum penetration depth is 17. 01m, which is basically consistent with the actual design value of 18. 50 m. Numerical simulation based on FEM was also performed and the calculated data of the double-row steel sheet pile was closer to the measured value. Comparison with actual horizontal displacement data shows that the double-row steel sheet pile cofferdam structure design is reasonable and reliable, providing reference for related engineering applications.

Abstract:Based on the themes of World Water Day and China Water Week over the years and their changing hot spots, the development and changes of water resources in the natural environment and human social life were summarized. The role of water resources in the sustainable development of modern society was analyzed and the scientific development of water resources was shown. The current global water resources management and protection measures was discussed. The themes of World Water Day shows a trend changing from humans start to the harmonious coexistence between humans and nature, and the themes of China Water Week are always related to government macro water resources policy. During the development of World Water Day and China Water Week, the ecological idea of harmonious coexistence between human and water resource is displayed gradually, and it shows that the idea of living in harmony with nature around the world enjoys popular support.

Abstract:The research progress of seepage stability of rainfall-induced accumulation landslide both at home and abroad is reviewed from the aspects of unsaturated rainfall infiltration characteristics, evaluation methods of stability for accumulation landslide and instability mechanism of rainfall-induced accumulation landslide. In view of the deficiency in the study of seepage stability of rainfall-induced accumulation landslide, it is pointed out that the geological structure characteristics should be clarified. The coupling mechanism of seepage and runoff and the interaction mechanism of seepage-geological structure-mechanical parameters should be further investigated. The study of the dynamic disaster mechanism for rainfall-induced accumulation landslide should be strengthened and the safety evaluation method of rainfall-induced accumulation landslide should be improved in the future.