Abstract:After briefly describing the historical evolution, hydrological characteristics and storm surge disasters of the Huangpu River, the history and results of the study on the tidal sluice at the Huangpu River Estuary were reviewed, and the main future research interests were proposed. The results of the preliminary study show that the tidal sluice at the Huangpu River Estuary is an important part of the flood control capacity improvement scheme of the Huangpu River, and is an inevitable choice to solve the permanent flood (storm surge) control problems in Shanghai. The basic function of the sluice is to resist storm surge and adapt to navigation, and reasonable regulation of the sluice has a great effect on the extraordinary high level of the river basin caused by the combined action of flood and tide. The defense criterion of the designed tidal level of the sluice is based on the 1 000-year return period at the end of 100-year service. The total net width of the single hole of the sluice is greater than 300 m, which has little impact on flood discharge, navigation and river regime, and the siltation of the barrier chamber can be controlled. Key points of future research should be focused on the impact of the sluice built at the bend on the river regime and navigation, the impact of the closing time and frequency on the effect of storm surge control and navigation, the adaptability of the barrier type to the function, the closing time, the siltation of the river channel, and the impact of the span on the stress. Finally, since the flood control capacity of the middle and upper reaches of the Huangpu River cannot be completely improved by the sluice construction at the estuary, heightening and reinforcing the embankment is suggested simultaneously, and flood control emergency plans must be prepared before the two works completed.

Abstract:The research progress of urban raw water system scheduling was reviewed both domestically and internationally from three aspects, including theoretical research, software development and engineering practice. The differences between raw water scheduling and water resource allocation as well as reservoir group scheduling were discussed, the advantages and disadvantages of simulation scheduling and optimization scheduling were analyzed, and the development of intelligent scheduling technologies and corresponding application in raw water companies were summarized. The characteristics of simulation software and decision support systems in the field of raw water scheduling were introduced and the application approach of decision support system in intelligent scheduling software development was analyzed. Through analyzing engineering cases of urban raw water systems of various scales domestically and internationally, the practical value of raw water scheduling was analyzed in the aspects of rational use of water resources, improving water supply efficiency and responding to emergencies. It is pointed out that future research directions include strengthening theoretical research on intelligent scheduling of urban raw water systems, establishing urban raw water intelligent scheduling systems with wide applicability and strong operability, improving the prediction accuracy and timeliness of scheduling targets for urban raw water systems, establishing a scientific library of emergency scheduling plans for urban raw water systems, and forming an evaluation system for urban raw water system scheduling that meets ecological and development needs.

Abstract:To explore the influencing factors of pressure oscillation induced by the movement of entrapped air pockets in pressure pipelines, and to fully characterize the transient effects of air pockets motion, pressurized air pockets in a more complex experimental piping system were studied, which was different from previous experiments based on the discharge of non-pressurized air pockets at the end of a simple piping system. The law of pressure boost caused by the movement of air pockets under different flow and volume conditions was discussed. The experimental results show that the single influencing factor of system flow rate and air pocket volume on pipeline pressure is not linear, but presents a convex parabola relationship. The maximum pressure boost value is determined by the opening of the end valve, the change of water velocity gradient caused by gas discharge, and the buffering effect of the remaining air pockets.

Abstract:A three-dimensional (3D) two-phase hydrodynamic-pollutant-coupled mathematical model for an open channel confluence of rectangular cross section with equal width was established. The pollutant was considered conservative and the degradation effect was not taken into account.Based on the Reynolds stress model, the geometric characteristics of separation zone and the pollutant transport laws under different junction angles were quantitatively analyzed. The calculation results show that the geometry of the separation zone and pollutant distribution at the confluence have obvious 3D characteristics and are affected by the junction angles. The geometric symmetry of the separation zone is stronger when junction angle is larger. The pollutant distribution is different because of different locations of the secondary flow under different junction angles. The maximum width of the pollution zone and the width of the mixing interface increase with the junction angle.The mixing rate of pollutants upstream of the separation zone increases with junction angles.Downstream of the velocity recovery zone, the mixing rate is not affected by the junction angles, which has an exponential relation with the downstream distance.

Abstract:Based on the coupled hydro-thermodynamic lattice Boltzmann model, and considering the interaction between the flow field and the temperature field, the growth and collapse processes of the cavitation bubbles in the near wall region were systematically investigated. The influence of the wall-bubble dimensionless distance and initial input temperature on the bubble morphology evolution process and the collapse intensity were analyzed. Furthermore, the differences between the results obtained by the coupled hydro-thermodynamic model and the passive scalar model were proposed. The results indicate that the relationship between the dimensionless distance and the maximum radius represents a power law if the bubble cannot keep its roundness during the growth stage due to the restriction of the wall. It shows a linear relationship if the dimensionless distance is greater than 1.6. A linear relationship exists between the input energy and the maximum radius, while a power law exists between the initial input dimensionless temperature and the maximum radius. The effect of high temperature on the gas-liquid interface is considered in the coupled hydro-thermodynamic method and compared to the passive scalar method, a larger jet volume and more concentrated jets with lower collapse intensity can be obtained during collapse stage.

Abstract:In order to improve the accuracy of dam deformation prediction, a concrete dam deformation prediction model with optimized variational mode decomposition (VMD) and gated recurrent unit (GRU) was proposed based on the idea of decomposition-reconstruction, in which the deformation signal processing technology was used to perform time-frequency decomposition on the measured deformation and the deep learning networks was combined to predict and reconstruct the decomposed signals. Grey wolf optimization (GWO) optimized VMD was used to decompose the raw data into a set of optimal intrinsic mode components (IMF), and GWO optimized GRU network was used to perform rolling prediction on each IMF component. By overlaying the prediction results of each component, displacement sequence prediction results were obtained, solving the problems of poor decomposition effect caused by VMD manual parameter selection and the impact of GRU manual parameter selection on training speed, usage effect, and robustness. The prediction results of engineering examples show that the model has low prediction error and good prediction accuracy and robustness.

Abstract:The evolution of the longitudinal process of tailings dams breaching during overtopping failure was systematically analyzed by three sets of flume breaching tests at different flow rates, and the relationship between erosion rate and shear stress was discussed.The results show that the tailings dam overtopping failure shows a longitudinal pattern of steep canyon erosion with a pivot point rotational erosion pattern.The outburst flow and density both show an upward and then downward trend, but with large fluctuations in water-sand flow density. Different inflow flows affect the erosion rate of the dam at each stage, with the least effect on the erosion rate in the first stage and the greatest effect in the second stage. The maximum erosion rate increases with the increasing upstream inflow, but does not affect the relative change of the erosion rate along the dam bed.The erosion resistance of the soil on the dam is not only recated to the strength of the dam material, but also closely related to the density of the fluid on it.

Abstract:To further improve the accuracy of obtaining material parameters for concrete arch dams, a material parameter inversion model based on multi-output support vector regression (MSVR) and sparrow search algorithm (SSA) was constructed. To quickly simulate the nonlinear relationship between radial displacement of dam body and material parameters, a high-precision MSVR model was established instead of the finite element model calculation, and SSA was used to optimize and invert the required parameters.The verification results of engineering examples show that the constructed inversion model has high calculation accuracy and fast calculation speed, which can quickly invert the material parameters of the dam body and dam foundation, and can be used for the inversion analysis of material parameters in actual engineering.

Abstract:To reveal the influencing mechanism of curing temperature on the strength properties of solidified dredged silt,the dredged silt was solidified with soda residue, ground granulated blast furnace slag and carbide slag. Unconfined compressive strength (UCS), California bearing ratio (CBR) and triaxial compressive tests were conducted to investigate the strength properties of solidified silt. The microstructural mechanism was discussed based on X-ray diffraction and scanning electron microscopy. The results show that the relationship between the UCS of solidified silt and curing temperature can be described by an exponential function. The UCS of solidified silt increases significantly when the curing temperature increases from 35℃ to 50℃ and the UCS ratio between 50℃ and 20℃ varies from 2.4 to 6.8. The curing temperature and time have more significant influence on the strength of solidified silt with low water content. For the solidified silt with an initial water content of 44%, the increase of CBR with curing time is significant at high curing temperature, and its value meets the minimum CBR requirement for highway and primary road base. When the curing temperature increases from 20℃ to 50℃, the stress-strain curve of the solidified silt changes from strain-softening to strain-hardening. The ratio of cohesion for the solidified silt at 50℃ to 20℃ varies from 3.8 to 8.4, and the friction angle ratio varies from 1.1 to 1.2. With the increase of curing temperature, the hydration products such as calcium chloroaluminate hydrates and calcium silicate hydrate increase, and the particle agglomeration phenomenon is more significant, leading to the strength increase of the solidified dredged silt.

Abstract:To assess the impacts of the Danjiangkou Dam heightening on water temperature in the main stream of the Hanjiang River, the measured water temperature data of the Baihe, Huangjiagang and Xiangyang stations in the mainstream of the Hanjiang River was analyzedand the variation degree of water temperature in the lower reaches of the reservoir was quantitatively evaluated based on the improved evaluation indicator values for river water temperature variation. The results show that the Danjiangkou Reservoir heightening has significantly changed the hydrological regime in the middle of the Hanjiang River. The extreme variation value of water temperature under the dam shows a downward trend, and the degree of homogenization increases year by year. The date of the maximum and minimum water temperature at the Huangjiagang station has been postponed, indicating the phenomenon of cold and warm stagnation. The change degree of water temperature regime is closely related to the distance. The Huangjiagang station is closer to the dam, and its water temperature regime changes obviously, and the water temperature concentration period lags about 23 days compared with that before the dam heightening. The Xiangyang station far away from the dam has little water temperature variation regime.

Abstract:Taking the residential buildings within a small community in Xi’an as the study object, a high-precision urban rain-flood model was constructed. The model’s reliability was validated using measured data from monitoring instances of urban inundation during heavy rainfall. The dynamic flooding process inside the residential buildings under six different major rainfall return period design scenarios was simulated. Considering the housing configuration of middle-income families in Xi’an City as the computational unit, the depth thresholds for the flooding of various indoor properties were analyzed, and the relationship curve between the depth of indoor property flooding and the corresponding loss rate was derived. By combining this curve with the flooding depths of different residential buildings in the study area under various major rainfall return periods, accurate data on property losses due to flooding were obtained. The results indicate that under different rainfall recurrence intervals, the inundation depth of the ground floor of the same residential building increases with the larger recurrence interval. For the same recurrence interval, the flooding process and maximum inundation depth of houses in different residential buildings vary due to differences in elevation.

Abstract:In order to explore the reasonable shape of the Huangchigou overflow bend channel, the influence of shape parameters on the flow was studied by means of orthogonal design and numerical simulation.Different parameter combinations were determined based on orthogonal experimental design for three shape parameters, including width of bend, radius of curvature and longitudinal slope. Nine sets of orthogonal experimental schemes were determined and simulated by the numerical model after validation by the experimental results from hydraulic model tests. The main factors affecting the water level difference in the bend sections and steep slopes were analyzed.The results show that the effect of the three shape parameters from the largest to the smallest is the longitudinal slope, bend width and the radius of curvature.The slope is a significant factor, and the flat slope is the best. The curvature radius and width of the bend have no significant impact. Therefore, a reasonable shape parameter is recommended that the slope is 0, and the original design values should be maintained for curvature radius and width of the bend.

Abstract:To efficiently invert seepage parameters, a multi-factor sensitivity analysis was used to study the sensitivity rank of the materials in the anti-seepage system and surface bedrock based on the seepage control characteristics based on a finite element seepage analysis model of the extra-high core rockfill dam at Changheba Hydropower Station. The results show that the surface bedrock and main anti-seepage curtain have a large impact on the reduced head ratios of the double cut-off walls, with a range of 0.174 and 0.125, respectively. The sensitivity of other anti-seepage structures is weak and the sensitivity ranging from strong to weak is the secondary anti-seepage curtain, the secondary cut-off wall, the main cut-off wall, and the core wall. The error between the inversion and measured values is less than 5%, which meets the engineering application requirements.

Abstract:The commonly used C25 concrete was selected as the research object and the water absorption kinetic method was employed to investigate the absorption characteristics of concrete to the water-soluble infiltration capillary/crystalline waterproof (WCCW) material. Moreover, the influences of absorption saturation degree and curing period on water absorption rate and water absorption kinetic parameters were examined. The results reveal that absorption process of concrete to WCCW material conforms to the water absorption law, in which the absorption saturation degree increases rapidly during the initial 2.h, and it can reach 94% after immersion for 8.h. With the rising of absorption saturation degree and elapse of curing periods, the saturated water absorption rate decreases, while the water adsorption kinetics parameter α reduces and λ increases. Power law relationship exists between absorption saturation degree of WCCW material and water absorption kinetic parameters or the curing period. The economical absorption saturation degree after optimization is 60%. Concrete needs to be cured after absorbing WCCW material for 8.h. A more reasonable curing period is 7.d and shorter curing period is doubtful to the final quality.

Abstract:A series of triaxial shear tests were carried out on improved low liquid limit clay with different amounts of calcium lignosulfonate (Ca-LS) and different curing time. The law of the stress-strain curve, peak deviator stress and shear strength parameters were analyzed. The internal mechanism of the improved soil was analyzed with the scanning electron microscope. The test results show that Ca-LS can significantly improve the shear strength of clay. With the increase of Ca-LS content, the shear strength of improved soil first increases and then decreases, and the optimal content is 8%. With the increase of curing time, the shear strength of the improved soil becomes stronger, but the strengthening speed gradually slows down. After 7.d of curing, the peak deviator stress of the improved soil containing 8% of Ca-LS is 2 017.23.kPa, which is 236.25% higher than the pure clay that cured for the same time. The cohesion force of the improved soil first increases and then decreases with the Ca-LS content, and the internal friction angle of the improved soil first increases and then remains stable. The internal mechanism of the modified soil strength improvement can be summarized as filling pores, ion exchange, adsorption of wrapped soil particles and cemented soil particle aggregates.

Abstract:To further explore the expansion and shrinkage mechanism of expansive soil of the canal slope in the first phase of Northern Xinjiang Water Supply Project, the free expansion rate, loaded expansive soil rate and shrinkage test of the expansive soil under three different circulation modes were carried out. The law of expansion and shrinkage characteristics was analyzed from a macro perspective, and the physical mechanism was revealed from a micro perspective by scanning electron microscope test.The results show that the expansion deformation of expansive soil can be divided into three stages, including rapid, uniform and stable expansion with the time increase. The expansion change is mainly concentrated in the rapid expansion stage. The larger the overburden load, the smaller the loaded expansion rate. The overburden pressure inhibits the water absorption and expansion of expansive soil. With the increase of the cycles, the unloaded expansion rate, the loaded expansion rate and the linear shrinkage rate all show a decreasing trend, and gradually tends to a stable value after the fifth cycle. Among them, the dry-wet-freeze-thaw cycle decreases the most, followed by the dry-wet cycle, and the freeze-thaw cycle is the smallest.In terms of the microscopic mechanism, after the sample is cycled, the porosity and the total number of particles in the soil increase gradually, while micro indexes such as the total area of particles decrease gradually.The size and content of clay particles are the main factors affecting the expansion and shrinkage. The cycle effect affects the changes of the size, content and arrangement of clay particles. Among them, the total area of dry-wet-freeze-thaw cycles has the greatest change, and the expansion and shrinkage of expansive soil samples have the greatest change. The freeze-thaw cycle has the least influence on the microstructure, and the expansion and shrinkage of expansive soil samples have the least change.