Abstract:The runoff coefficient is a critical parameter that quantifies the proportion of rainfall converted into surface runoff and is widely used in water resources management and urban planning. This paper provides a comprehensive review of the concept, historical evolution, determination methods, influencing factors, and research methodologies related to the runoff coefficient. It examines how the runoff coefficient varies under different influencing factors and evaluates the advantages and disadvantages of various research approaches. The study emphasizes the importance of interdisciplinary collaboration in advancing technological innovation, integrating data sources, and balancing cost-effectiveness. In the context of rapid climate change and urbanization, it outlines current challenges and future research directions, highlighting how emerging technologies and methods, such as computer technology, remote sensing, and machine learning, can offer new perspectives for runoff coefficient research and provide scientific support for decision-making in water resources management and urban planning.

Abstract:This paper systematically reviews the research progress on the flow characteristics of bubble plumes from three aspects: theoretical models, behavioral characteristics, and flow field properties. In terms of theoretical models, it reviews the development process from early single-phase plume models to modern integral models that incorporate bubble swarm dynamics, stratified environments, and line-source effects, elucidating key mechanisms such as buoyancy-driven flow, fluid entrainment, and bubble slip. Regarding behavioral characteristics, this paper summarizes experimental and numerical simulation findings on the diffusion laws, oscillation characteristics, and wall-attachment effects of bubble plumes. For flow field properties, it reviews advances in utilizing experimental measurement techniques (e.g., PIV and PTV) and numerical simulations to reveal flow field information, including three-dimensional velocity fields, turbulent structures, and bubble distributions. It is pointed out that future research directions for bubble plumes should include integrating artificial intelligence algorithms, incorporating complex physical processes such as bubble deformation, coalescence, and breakup, deepening the theoretical models for line-source bubble plumes, improving the characterization of three-dimensional flow fields, and enhancing the prediction accuracy of pollutant interception.

Abstract:To prevent the semi-submerged jet in ski-jump stepped spillways, which leads to abnormal pressure distributions, severe water wing phenomena and structural vibrations in the upstream step section, a combination of physical model tests and theoretical analysis was used, and three types of test models were designed to study the influence of installing ventilation shafts and extending the inlet horizontal section on the flow pattern and hydraulic characteristics of the ski-jump section. The results show that installing ventilation shafts and extending the inlet horizontal section can significantly improve the ski-jump flow pattern, effectively mitigate the water wing phenomenon, and successfully eliminate adverse hydraulic conditions such as negative pressure. The maximum operating discharge for the ski-jump stepped spillway and the minimum length of the aeration basin were determined, providing a reference for the structural design and operation of ski-jump stepped spillways.

Abstract:According to the flood discharge characteristics of pumped-storage power plants, such as high head, low discharge, and static reservoir water, a 1∶25-scale physical model of a shaft spillway was established based on the shaft system consisting of a circular guide-pier weir, a horseshoe-shaped stilling shaft and a pressurized sloped section, and the flow characteristics of the circular guide-pier weir and the energy dissipation performance of the shaft system were investigated. The experimental results show that the comprehensive discharge coefficient of the circular guide-pier weir ranges from 0.4 to 0.5, effectively ensuring symmetrical flow entry into the shaft and forming detached-wall jets to eliminate wall cavitation risks and enhance air entrainment. The synergistic operation between the stilling shaft and the pressurized sloped section significantly improves energy dissipation efficiency and flow control performance. The horseshoe-shaped stilling shaft demonstrates superior energy dissipation performance and downstream flow regime stability.The energy dissipation rate of the shaft system exceeds 88%, and increases as the discharge decreases.

Abstract:To address the issue that intense air-water mixing, caused by the violent collision between water falling along the shaft wall of a drop shaft and the water body at the shaft bottom,may compromise the safe operation of the project, hydraulic phenomena were observed through physical model tests, the air-water mixing characteristics in the drop shaft were explored, the venting mechanism was analyzed, a systematic hydraulic optimization design of the shaft venting facilities was carried out, and a high-efficiency combined venting and bubble-reduction scheme, consisting of a semi-annular weir and three intermediate baffles, was proposed. The results show that the semi-annular weir can divert air-entrained flow away from the tunnel inlet.By extending the flow path and increasing the degree and frequency of streamline deflection, the intermediate baffles promote the collision, coalescence, and upward escape of micro-bubbles, thereby improving the efficiency of venting and bubble reduction, ensuring the safe and stable operation of the drop shaft across a wide range of water level fluctuations.

Abstract:To investigate the characteristics of flood encounters between the main stream of the lower Yangtze River and Poyang Lake, based on the discharge series (from 1950 to 2023) from important hydrological stations on the lower Yangtze River (Jiujiang Station and Datong Station) and the inflow control station of Poyang Lake (Hukou Station), the ordered clustering analysis method was used to identify the mutation point (2003) of the annual total runoff and annual maximum flood peak discharge in the lower Yangtze River. Using the annual maximum flood peak discharge, annual maximum 7-day flood volume, and annual maximum 15-day flood volume as characteristic parameters of the annual maximum flood, the mixed von Mises distribution and the P-Ⅲ distribution were used to fit the marginal distributions of the annual maximum flood occurrence time and magnitude at the three stations, respectively. A two-dimensional Archimedean Copula function was employed to construct the two-dimensional joint distributions of the annual maximum flood occurrence time and magnitude in the lower Yangtze River. Based on this, the encounter risks and changing characteristics of flood occurrence time and magnitude in the lower Yangtze River before and after the impoundment of the Three Gorges Reservoir were analyzed. The results show that after the impoundment of the Three Gorges Reservoir, the encounter risk of annual maximum flood occurrence time in the lower Yangtze River increased in some aspects and decreased in others. Currently, the encounter risk of flood occurrence time between Hukou Station and the main stream stations (Jiujiang Station and Datong Station) reaches its maximum from early June to early July, while the encounter risk between Jiujiang Station and Datong Station reaches its maximum from late June to late July, which should be paid special attention to. After the impoundment of the Three Gorges Reservoir, the risk rate of encountering a certain magnitude of flood at any two stations decreased. The operation of the Three Gorges Project effectively reduces the risk of encounter in the annual maximum flood magnitude between the main stream of the lower Yangtze River and Poyang Lake, with the greatest risk reduction observed between Jiujiang Station and Datong Station.

Abstract:To investigate the evolution of splitting tensile strength of low-heat cement concrete with varying basalt fiber lengths, contents, and curing ages, splitting tensile tests were conducted on 160 specimens using the control variable method at a loading rate of 0.05 MPa/s. The influence of basalt fiber content and length on the splitting tensile strength at different curing ages was analyzed. The results indicate that under conditions of varying basalt fiber content and length, the fibers enhance the splitting tensile strength at all ages, although the impact patterns differ significantly. When the fiber length was 12 mm, an increase in fiber content led to an initial rise followed by a decline in tensile strength at ages of 3, 5, 7, and 14 days, reaching a peak at a fiber content of 0.2%. When the fiber length was 24 mm, the splitting tensile strength exhibited an initial increase followed by a decrease as fiber content increased. Except for the 14-day curing age, the maximum strengths at all other ages were achieved at a fiber content of 0.2%. The optimal basalt fiber length and content were determined to be 12 mm and 0.2%, respectively.

Abstract:To investigate the deterioration process of concrete in severe cold areas under coupled freeze-thaw and leaching action, an experimental study was conducted using an alternating method of rapid freeze-thaw cycles and immersion in ammonium chloride solution. This study examined the time-dependent evolution laws of the physical and mechanical properties and microstructure of concrete, quantified the coupling effects of freeze-thaw and leaching action, and established a predictive model for the degradation of mechanical properties. The results show that under the coupled freeze-thaw and leaching action, both the leaching depth and the amount of calcium leaching increase linearly with the equivalent service duration, while the compressive strength and splitting tensile strength exhibit a negative exponential decay trend. A significant synergistic effect was observed when freeze-thaw and leaching acted concurrently, with the acceleration factors for strength degradation and mass loss rate reaching 1.2 to 1.5 and 20, respectively. The reasons are that freeze-thaw action leads to an increase in porosity and increases the number and width of micro-cracks, and the leaching of solid-phase calcium promotes smoother and larger pores. Furthermore, the temporal evolution of compressive strength damage under individual freeze-thaw, individual leaching, and coupled conditions consistently follows an inverse S-shaped curve pattern.

Abstract:To investigate the compressive deformation characteristics of saline soil under dissolution, taking sulfite saline soil from a certain area in Xinjiang as the research object, using laboratory seepage dissolution tests, compression tests, and micro-morphological analysis, the influence of dissolution on the compressive properties of sulfite saline soil was analyzed, and the deformation degradation mechanism of saline soil under seepage dissolution effects was revealed. The results show that under dissolution, the surface porosity of the specimen increases with the salt content, and the electrical conductivity of the leachate decreases rapidly initially and then gradually stabilizes with dissolution time. Dissolution significantly increases the compression coefficient of the specimen, which increases linearly with the salt content. Under dissolution, aggregates disintegrate, large flaky particles are transformed into medium and small particles with rounded shapes, and inter-particle pores and interlocked pores are converted into crystalline dissolution pores, thereby leading to more significant macroscopic deformation.

Abstract:Taking the Xueshi River in Ancient District of Suzhou City as the research object, this study analyzed the impact of initial rainfall runoff pollution on river water quality under the existing scheduling scheme. A hydrological-hydrodynamic-water quality coupled model was constructed based on the SWMM and MIKE11 models and used to simulate the changes in river water quality under different scheduling schemes. Furthermore, optimal scheduling schemes for improving the water quality of the Xueshi River after rainfall under different rainfall conditions were proposed. The results show that the overall water quality of the Xueshi River is good, but it degrades to Grade Ⅳ during heavy rain and rainstorm events. The initial rainfall runoff pollution has the most significant impact on the river water quality during heavy rain, while its impact lasts the longest during rainstorm. The constructed coupled model achieves good simulation results for water level, flow rate and water quality at each monitoring section. Through the design of working conditions, appropriately increasing the gate flow during heavy rain and rainstorm periods can significantly reduce the peak mass concentration of NH₃-N in the water body, stabilizing the water quality to Grade Ⅲ standard and thus effectively improving the river water quality after rainfall.

Abstract:To address the issues of low accuracy, poor reliability, and difficulties in programmatic implementation associated with traditional methods for identifying outliers in dam deformation, using the Jinping Ⅰ Dam as a case study, a nonlinear statistical model for dam deformation was developed based on trend surface analysis. Using the generated three-dimensional trend surface as a benchmark, an outlier identification envelope was constructed by setting allowable errors, and a program implementation pathway was designed at the computer system level. In response to the causes and data characteristics of outliers, a comprehensive solution for determining the nature of outliers was proposed, integrating remote system recall testing, self-diagnosis of data acquisition equipment status, and Euclidean distance criteria between initial and repeated measurements. The results demonstrate that the proposed method achieves highly accurate dynamic identification of deformation outliers without requiring dynamic computation. The generated three-dimensional trend surface possesses clear physical and mechanical significance, enabling precise evaluation of dam deformation behavior under varying reservoir water levels and ambient temperatures.

Abstract:Aiming at the problem that existing anomaly detection models for seepage monitoring data of earth-rock dams exhibit weak generalization capability and can only identify specific types of abnormal measurements, leading to low detection accuracy and high false-alarm rates, an anomaly detection model for earth-rock dam seepage monitoring data based on the graph attention network (GAT) mechanism and temporal convolutional network (TCN) is proposed. This model utilizes the GAT mechanism to assign weights to environmental factors, employs the TCN to improve the extraction of temporal features, and identifies abnormal data based on the model’s prediction error. Taking a clay-core rockfill dam in northwest China as a case study, six anomalous scenarios were constructed to validate the model. The results show that the proposed model can accurately identify abnormal seepage measurements of earth-rock dams, with average ROC-AUC and PR-AUC values of 0.948 and 0.968, respectively, meeting the requirements of practical engineering applications. Comparative analyses with state-of-the-art anomaly detection models further confirm that the proposed model exhibits superior anomaly detection performance and robustness.

Abstract:In order to establish typical deep deformation and failure modes for slopes in the Paleogene red-bed area of the Yellow River to Xining Diversion Project, and to identify deep failure-type slope deformation masses, based on investigation and analysis results of slope deformation and failure phenomena in the water supply area, the formation mechanism of each discovered deep-failure red-bed landslide mass was analyzed, and a reverse analysis was conducted to determine the geomechanical characteristics of natural slopes before the formation of red-bed landslides. Numerical simulations were performed to analyze the key factors causing deep deformation failure of natural slopes in the Paleogene red-bed area, and typical deep deformation and failure modes for slopes in the Paleogene red-bed area were established. Slope deformation masses with the geological structural characteristics of typical deep deformation and failure modes were identified in the Paleogene red-bed area, and a three-dimensional numerical simulation model was established to analyze the deformation and stability characteristics of these deforming slope under natural, seismic, and rainfall conditions, and identify deep failure-type slope deformation masses. The results show that the deep deformation and failure mode for slopes in the Paleogene red-bed area is related to the stratum rock segments. According to the established typical deep deformation and failure mode for slopes, a potential deformation mass is identified along the No.24 branch line of the water supply project in the Paleogene red-bed area, showing poor stability under rainstorm conditions.

Abstract:To address the complex characteristics of high water content and fine-grained composition in Poyang Lake sediment, composite activation technology and microstructure tests were adopted to explore the feasibility of developing solidified composite materials from Poyang Lake sediment. By incorporating industrial waste materials such as mineral powder, along with activators including Na₂SiO₄, Na₂SO₄, Na₂CO₃, and NaOH, the mechanical properties, water-erosion resistance, and freeze-thaw resistance of the solidified sediment were systematically evaluated. Combined with microstructure analysis, the regulatory mechanism of the composite activators on the performance of the solidified sediment was revealed. The results show that the addition of the composite activators promotes the formation of flocculent cementitious substances, effectively fills the pores, enhances the interparticle bonding, and optimizes the microstructure of the solidified sediment, providing a feasible technical path for the resource utilization of Poyang Lake sediment. In particular, the Na+-OH^- dual-drive network formed by Na₂SiO₄ and NaOH significantly promotes the depolymerization-polycondensation reaction of amorphous SiO₂ and Al₂O₃ in the sediment, generating C-A-S-H, N-A-S-H and other alkali gels. The ordered distribution of hydration products significantly increases the 28-day compressive strength of the solidified sediment to 11.61 MPa, a 69.0% increase over the control group, while simultaneously improving water-erosion resistance and freeze-thaw resistance.

Abstract:Aiming at the severe environmental problems caused by the surge in disposable mask usage due to the epidemics of respiratory diseases such as COVID-19 and H1N1, the feasibility of masks as soil reinforcement materials was explored, triaxial tests and seepage tests were conducted on calcareous sand mixed with different mass fractions of masks, the effects of mask mass fraction on the strength, modulus, volumetric strain, particle breakage rate and permeability coefficient of calcareous sand were studied, and the improvement effect of masks on the mechanical properties of calcareous sand was analyzed. The test results show that with the increase of mask mass fraction, the strength, ductility and internal friction angle of the mask-calcareous sand mixture increase, while the permeability, particle loss and shear dilation are inhibited. The reinforcement effect of masks on soil arises from the high friction at the contact interface between the masks and calcareous sand, and when the soil deforms, the masks improve the overall strength of the mixture by restricting the movement of soil particles. Based on a comprehensive evaluation of the influence of masks on the performance of calcareous sand, the optimal mass fraction of masks is determined to be 0.3%.

Abstract:To investigate the hydraulic characteristics of fish-friendly culverts, a numerical model of a fish-friendly culvert with triangular lateral baffles was developed based on the large eddy simulation method. Three-dimensional numerical simulation of flow within the culvert was conducted under various submergence levels, and the accuracy and reliability of the numerical model were validated through flume experiments. The results indicate that at half the height of the baffle, flow separation occurs along the outer edge of the baffle, and the size of the recirculation zone increases as the submergence level decreases. The intensity of the shear layer and the turbulence around the baffle are negatively correlated with the submergence level. Under shallow flow conditions, vortex shedding becomes more chaotic, with stronger and more numerous vortex structures near the water surface compared to those near the bed.

Abstract:To analyze the status of spawning habitat for the four major Chinese carps in the lower reaches of the Ganjiang River under varying hydrodynamic conditions, a physical habitat model for fish spawning habitat was established by coupling the two-dimensional hydrodynamic model and the habitat suitability model based on the fuzzy logic method. This model was used to simulate the spatial distribution of suitable spawning areas for the four major carps in the lower reaches of the Ganjiang River under different flow rates, to analyze the variation patterns of the weighted usable area (WUA) of spawning habitat, and to determine the appropriate ecological flow required for spawning. The results show that the overall suitability of the main branch was higher than that of the middle branch and the south branch when the flow rate was low. When the flow was high, the overall suitability of the main branch decreased obviously while the suitability of the middle branch and the south branch increased. The WUA of spawning habitat increased initially and then decreased with increasing flow rate. Compared with the low-flow condition, the WUA decreased faster under the high-flow condition. When the flow rate was 4 200 m³/s, the WUA was the largest, accounting for 22.97% of the study area. The suitable ecological flow range of spawning habitat for the four major Chinese carps was between 3 500 and 4 800 m³/s, and the optimum ecological flow was 4 200 m³/s.

Abstract:To ensure navigation safety during the pre-advance construction period of the second-stage cofferdam at the main branch project in the lower reaches of the Ganjiang River, a two-dimensional hydrodynamic numerical simulation method was employed to model and analyze the hydrodynamic processes of the temporary navigation channel under various construction scenarios and working conditions. Threshold navigation flow conditions and corresponding improvement measures were proposed. The results demonstrate that retaining the upstream section of the first-stage cofferdam serves a flow-diversion function, thereby improving local navigation flow conditions. Although the pre-advance construction alters the local flow direction in the river channel and affects lateral flow velocities in certain sections of the temporary channel, its overall impact on navigation flow conditions remains limited. However, retaining the downstream cofferdam of the first stage increases the diversion ratio of the left temporary channel, significantly expanding the range where longitudinal flow velocities exceed 2 m/s, which adversely affects navigation. After implementing adjustments, the numbers of cross-sections in the temporary channel with lateral flow velocities exceeding 0.5 m/s under current conditions, after removal of the existing cofferdam, and during the pre-advance construction of the second-stage cofferdam decreased by 66.7%, 70%, and 66.7%, respectively, compared to pre-adjustment conditions, indicating a notable improvement in navigation conditions.