Abstract:To address the deficiencies of traditional diffusion models, a mixing length coefficient model was introduced to establish a vertical distribution model of suspended sediment. The effects of different factors on the vertical distribution of suspended sediment were investigated. The results show that when the actual mixing length coefficient is smaller than the commonly assumed value of 0.4, the sediment concentration calculated using the assumed value is overestimated, and vice versa. An increase in sediment concentration intensifies particle interactions, and the vertical distribution of sediment concentration presents a characteristic of “smaller at the upper part and larger at the lower part”. Larger particle size results in greater sediment settling velocity, causing more sediment to accumulate near the bottom and making suspension more difficult. Higher flow velocity enhances vertical turbulence, reducing the sediment concentration gradient between the riverbed and the water surface.

Abstract:Based on the theory and quantitative methods of socio-economic and ecological water use balance, combined with the SWAT model, a research approach for the balance between socio-economic and ecological water use in the Qinhe River Basin was proposed. The socio-economic and ecological water use balance status in the Qinhe River Basin from 2005 to 2020 was analyzed, and the equilibrium points of socio-economic and ecological water use for planning level years (2025, 2030, and 2035) under future climate change scenarios were predicted. The results show that the imbalance indices of socio-economic and ecological water use in the Qinhe River Basin from 2005 to 2020 were all negative, indicating a persistent ecological water deficit in the basin. The imbalance index for the current year exhibits a fluctuating upward trend, and the socio-economic and ecological water use balance status is gradually improved. Under the rainfall frequencies of 95%, 75% and 50%, the predicted balance points of socio-economic and ecological water use in 2025 are 0.76, 0.66 and 0.63, respectively, those in 2030 are 0.67, 0.63 and 0.52, respectively, and those in 2035 are 0.54, 0.43, and 0.41, respectively.

Abstract:To address the problem of sediment accumulation in the lateral inflow forebay of large pumping stations that pumps water from sediment-laden rivers, taking a lateral inflow forebay of the Jingtaichuan Electric Power Irrigation Project in Gansu Province as the research object, FLUENT software was used to numerically simulate water-sediment two-phase flow under sedimentation conditions for different contraction wall configurations of the lateral inflow forebay based on the Realizable k-ε turbulence model coupled with mixture multiphase flow model. The results show that a high-velocity mainstream zone is formed in the center of the inflow forebay, and vortices of varying sizes are generated on both sides of the mainstream zone, forming two low-velocity recirculation zones. Affected by the flow field structure, these recirculation zone on two sides are high-concentration sediment areas, with the relative sediment concentration increasing significantly from the mainstream zone to the recirculation zone. The increase in relative sediment concentration with the water depth in the recirculation zones is more significant than that in the mainstream zone. As the contraction angle of the sidewall of the lateral inflow forebay increases, the area of the recirculation zone outside the mainstream zone decreases significantly, the sediment-carrying capacity of the water flow is enhanced, and the proportion of the high-concentration sediment areas is significantly reduced, effectively improving the sediment deposition situation in the forebay.

Abstract:In order to further understand the bond behavior of FRP-concrete interface in underground gas storage under combined compression and shear conditions, an indoor direct shear test was conducted to study the bond performance of the FRP-concrete interface under varying influencing factors, including normal stress, concrete surface roughness, adhesive thickness and concrete strength. The results show that the FRP-concrete interface is mainly characterized by debonding failure of the concrete surface under the combined compression and shear conditions. A significant nonlinear relationship exists between the interfacial shear stress and displacement. The strength and stiffness of the interface increase with the increase of normal stress, concrete surface roughness, adhesive thickness and concrete strength. The Mohr-Coulomb criterion can be used to describe the yield failure behavior of the interface under compression and shear conditions.

Abstract:To address the issues of local damage and leakage in geomembranes, which can lead to seepage deformation in the geomembrane cushion, a study on acoustic monitoring of seepage deformationof geomembrane cushion is proposed to be carried out based on the excellent sound transmission properties of geomembranes. A laboratory experimental study on the sound transmission properties of geomembranes and the acoustic characteristics of seepage deformation of geomembrane cushion was conducted using a self-designed testing apparatus. The results show that both PVC and PE geomembranes exhibit a certain degree of sound transmission, with better sound transmission effect for low-frequency sound waves than that for high-frequency sound waves. The acoustic energy of the seepage deformation of geomembrane cushion is mainly concentrated in three frequency bands: low (below 250.Hz), medium (500 to 750.Hz), and high (1 000 to 1 250.Hz), with the highest energy in the low-frequency band. The maximum instantaneous sound wave intensity during the seepage deformation of the geomembrane cushion is 119.29.dB, while the stable sound wave intensity can still be maintained at around 90.dB, both of which are greater than the observation results of the underwater background noise in relevant water areas under undisturbed conditions.

Abstract:Aiming at the problem of the significant decline in source-load synchronization of a hydro-photovoltaic complementary system under the penetration of a high percentage of photovoltaic power generation, a nested scheduling model that couples long-term water storage regulation in the outer layer with short-term power complementary in the inner layer is constructed. The model identifies the characteristics of photovoltaic output and load curve in the outer layer, while in the inner layer, based on the source-load matching mechanism, it divides the transmission channel into multiple target spaces according to the characteristics of water, light and load. The model employs the coupling linkage mechanism of intra-layer target classification and inter-layer global search to solve the power allocation of the transmission channel and obtain the power distribution in each target space. The results of the case study of the hydro-photovoltaic complementary system in the Xizang section of the Lancang River show that the constructed model can effectively guide the operating conditions of the system to approach the target preference region, and the formulated scheduling scheme can meet the requirements of short-term power curtailment, fluctuation risk control and power peak regulation, verifying the rationality of the model.

Abstract:In response to issues such as ambiguous drainage paths, unclear system division of responsibilities, and low implementation efficiency in urban road drainage systems when handling rainfall in China, the operational mechanisms of the urban road drainage system, as well as the discharge pathways of runoff, were thoroughly analyzed. The capacity thresholds for Beijing’s urban road drainage system to manage rainfall in terms of preventing wet shoes , preventing waterlogging , and preventing flooding , are established. In conjunction with the monitoring and early warning systems, as well as emergency rescue measures, construction guidelines for enhancing the system’s out-of-control prevention capacity are proposed. Improvement strategies for urban road drainage systems are proposed from three perspectives: top-level planning and design of the system, enhancement of comprehensive drainage capacity, and construction of emergency management.

Abstract:To reasonably activate the semi-restoration polder (SRP) and detention and retention area (DRA) and effectively reduce the water level of Poyang Lake, a two-dimensional hydrodynamic model of Poyang Lake and the downstream sections of its five tributaries was established using MIKE21. The extreme flood event was simulated by amplifying the 2020 Poyang Lake flood using the same-frequency method. Nine combination schemes were formulated by setting different activation water levels for SRP and DRA, and the flood diversion processes were simulated. The optimal scheme and its associated economic losses were further analyzed. The results indicate that the optimal flood diversion effect is achieved when the SRPs are activated at water levels of 21.50 m (for protection areas under 10 000 mu) and 22.30 m (for protection areas above 10 000 mu) and the DRAs are activated at water level of 22.50 m. Under this scheme, the flood diversion volumes for the SRPs and DRAs are 2.617 billion m³ and 2.569 billion m³, respectively, with maximum 24-hour water level reductions of 0.37 m and 0.25 m, respectively. After 48 hours of activation, the direct agricultural economic loss for the SRPs is 209 million yuan, while the loss for DRAs is 417 million yuan, of which the loss for the Kangshan DRA is 154 million yuan.

Abstract:Based on the monthly water quality and quantity synchronous monitoring data of Yangcheng West Lake from 2007 to 2019, the spatiotemporal variation characteristics of pollutant flux into Yangcheng West Lake and the retention rate of pollutant flux in the lake were quantitatively analyzed. The results show that the pollutant flux into Yangcheng West Lake is unevenly distributed throughout the year, and it is more easily affected by water volume when the water volume difference is large. Over the years, the pollutant fluxes into the lake showed an overall downward trend, with the largest to smallest reduction rates observed for ammonia nitrogen, total phosphorus, total nitrogen, and permanganate index. Among the eight main inflow rivers, the contribution rate of pollutants entering the lake in the Baidang River was the largest, followed by the Litang River and Jiejing River. In spatial distribution, the pollutant flux into the lake was the largest in the southern part of Yangcheng West Lake, followed by the northern and central parts. In 2019, the retention rates of pollutants in Yangcheng West Lake ranked from highest to lowest as ammonia nitrogen, total phosphorus, total nitrogen and permanganate index, and more than half of the pollutants entering the lake continued to flow into the middle lake. It is suggested to focus on the main pollutant inflow areas of the Baidang and Litang rivers, and strengthen the pollution source control and comprehensive treatment in surrounding areas.

Abstract:In order to explore the impact of the project of returning polders to lakes on the water environment, taking Luoma Lake as an example, based on the measured data, a two-dimensional unsteady water environment model was established for Luoma Lake before and after the implementation of returning polders to lakes. Combining the hydrodynamic model, Lagrangian particle tracking and water quality model, the impacts of the project of returning polders to lakes on hydrodynamics, water age and water quality were predicted. The results show that after the implementation of returning polders to lakes, under the conditions of easterly and northerly winds with a speed of 3 m/s, the average water level of the lake decreases by 0.36 m, and the average flow velocity increases by 12% at four monitoring sites. Under the condition of a northerly wind with a speed of 5 m/s, the water age near the polder area is reduced by 55%. The average improvement rates of COD, ammonia nitrogen, total nitrogen and total phosphorus can reach 3.3%, 3.1%, 2.3% and 2.2%, respectively. Therefore, it is concluded that the implementation of returning polders to lakes has a positive influence on the water environment of Luoma Lake.

Abstract:In order to explore the effectiveness of electrical resistance tomography (ERT) technology in testing the concrete placement uniformity of large-diameter bored piles, numerical simulation was conducted to optimize the key parameters of ERT sensors. A physical model test was carried out using a sensor with a diameter of 1 000 mm as an example. The signal-to-noise ratio, sensitivity uniformity, and sensitivity matrix condition number, as well as the error, relative error and correlation coefficient of spatial images were used to evaluate the performance and effect of the sensor. The results show that the sensor height has a limited effect on the sensor performance, while the conductivity of electrode material has no impact on the sensor performance. There exists a complex nonlinear relationship between the electrode length, width, and sensor performance. When the height of ERT sensor is 0.8 times the diameter, the electrode is copper, and the length and width of the electrode are 1/16 and 1/32 of the circumference of the cylinder, respectively, the ERT sensor demonstrates good performance in testing the concrete placement uniformity of large-diameter bored piles.

Abstract:To solve the problems of low efficiency, strong subjectivity, and prone to missed inspection in quality and safety hazards inspection during the construction of the Yangtze River protection water conservancy projects, the specific scenarios of various quality and safety hazards were identified by analyzing the requirements of multi-scenario quality and safety inspection of the projects. The YOLOv5 algorithm was used for image enhancement and optimization, and an intelligent recognition algorithm framework was established. Through on-site photography, web crawling technology, and internal data resources of the project department, thousands of high-quality photos were collected and organized to obtain a comprehensive dataset. On this basis, by integrating the regional inspection functions, the quality and safety inspection system can accurately monitor only the designated work areas. This effectively avoids false inspection and improves inspection efficiency and accuracy.

Abstract:Aiming at the problems of complex procedures and low computational efficiency of traditional inversion methods of concrete thermal parameters, an inversion method based on physics-informed neural networks (PINN) is proposed. In this method, the learning rate for optimizing the concrete thermal parameters to be inverted is determined according to the accuracy requirements of the parameters to be inverted. Based on the PINN inversion method, the thermal parameters of concrete without and with water pipe cooling were inverted through simulation tests, and the errors of the inversion results were analyzed. The PINN inversion method was compared with the inversion method of traditional finite element calculation combined with genetic algorithm. The results show that the PINN-based method for inversion of concrete thermal parameters has high accuracy, robustness and generalization ability. Using the improved method to determine the learning rate based on the accuracy requirements of the parameters to be inverted can effectively improve the calculation efficiency while ensuring the inversion accuracy. Compared with the traditional inversion method, the PINN inversion method has advantages in terms of a simpler computational framework and higher computational efficiency.

Abstract:In order to overcome the locality defects in the reliability analysis of dam structural systems and account for the variation of influencing factors in the entire failure domain, a global correlation coefficient was constructed to replace the approximate linear correlation coefficient based on the global importance assessment of stochastic influencing factors in dam structure reliability. A global measurement method for the correlation between different failure modes was proposed, and the TIS-MCS method was employed to achieve the quantitative analysis of global correlation. Through an engineering case study, the system reliability of a dam structure under multiple failure modes obtained using the global correlation measurement method was compared with results from other methods. The results indicate that the system reliability obtained using the global correlation measurement method is more reasonable, providing a new approach for the reliability analysis of dam structural systems.

Abstract:To address the issues of high fitting difficulty and frequent underfitting of the temperature component in traditional dam displacement monitoring models when applied to high-altitude concrete dams. The effects of air temperature, radiation, reservoir water temperature, and insulation layers on the boundary temperature of the dam body were analyzed. Additionally, considering the lag effect of dam displacement caused by the transmission of external temperature within the dam body, a lag function was constructed using the Rayleigh distribution. The particle swarm optimization algorithm was employed to optimize the lag days, resulting in an improved displacement monitoring model for high-altitude concrete dams with improved temperature components. The improved model was validated using data from two monitoring points at different locations on a high-altitude concrete gravity dam. The results demonstrate that, compared to the traditional model, the improved model exhibits higher fitting accuracy and better predictive performance, making it suitable for application in high-altitude concrete dams.