Abstract:To reduce the water noise induced by flow over broad-crested weirs and provide a basis for engineering optimization, a combined approach integrating physical model experiments and numerical simulations was adopted to investigate the influencing factors and spectral characteristics of the water noise. Physical model experiments were conducted to examine the effects of upstream discharge, downstream water depth, and weir height on the sound pressure level of water noise and the root mean square of fluctuating pressure. Quantitative relationships between the water noise sound pressure level and these influencing factors were established, and the A-weighted spectral characteristics of the water noise were analyzed. Numerical simulations were employed to investigate the effects of droplets and bubble clusters on water noise and reveal the causes of variations in the A-weighted spectrum. The results show that both the sound pressure level of water noise and the root mean square of fluctuating pressure are positively correlated with upstream discharge and weir height, and negatively correlated with downstream water depth. Among these factors, upstream discharge exhibits the most significant influence, followed by downstream water depth and weir height. High-frequency noise generated by bubble bursting leads to the dominant frequency of the A-weighted spectrum of water noise being located in the high-frequency range. Increasing the upstream discharge and weir height raises the high-frequency sound pressure level in the A-weighted spectrum, whereas increasing the downstream water depth reduces the high-frequency sound pressure level.

Abstract:Taking the Qiantang River Estuary as an example, this research employed a two-dimensional horizontal saltwater intrusion model capable of simulating tidal bore phenomena to investigate saltwater intrusion in a strong tidal bore estuary. By modifying the tidal level processes at the model’s seaward boundary to represent variations in offshore tides, the study examined the influence mechanisms of three tidal characteristic parameters, high tidal level, low tidal level, and tidal range, on saltwater intrusion in the estuarine region. The results indicate that offshore tidal changes primarily affect the extent of saltwater intrusion through variations in high tidal levels, while changes in low tidal levels have minimal impact. Therefore, it is inadequate to only use the tidal range index to reflect the influence of offshore tidal variations on estuarine saltwater intrusion. In addition, estuarine saltwater intrusion responds rapidly to offshore tidal changes, with effects persisting for more than three tidal cycles.

Abstract:Based on post-flood remote sensing images, measured cross-section data, and upstream water-sediment data from the Xiaobeiganliu reach of the Yellow River from 2000 to 2020, several characteristic parameters, including the swing width of the main channel, sinuosity coefficient, braiding coefficient, and central bar area ratio, were selected to analyze the evolution characteristics of the river regime in this reach and its main influencing factors. The results show that the swing width of the main channel gradually stabilized, with a multi-year average of 451 m, exhibiting strong variability in the upper section and relative stability in the middle and lower sections. The sinuosity coefficient ranged between 1.0 and 1.3 over the years, still reflecting the wandering nature of the channel. The braiding coefficient and central bar area ratio fluctuated markedly over time, with central bars being scattered and highly dynamic. Upstream inflow volume had a significant influence on river regime changes: both the sinuosity coefficient and braiding coefficient showed negative correlations with the inflow volume and its deviation from the multi-year average. Training works and natural control points worked together to narrow the channel, regularize the main flow, and thereby affect the river regime evolution.

Abstract:To investigate the influence of rainfall and tide superposition on the process of urban waterlogging in coastal cities, the GPU accelerated surface water flow and transport (GAST) model coupled with the storm water management model (SWMM) was used to simulate the characteristics of urban surface water accumulation and the process of pipe network drainage in the central urban area of Haishu District, Ningbo City, under different combination scenarios. The results indicate that the scenario with the largest peak waterlogging area occurred under a 50-year return period, high tidal level, and rainfall peak preceding the tidal peak, where the peak waterlogging area reached 119 800 km², 1.2 times the minimum area. The peak waterlogging area under overlapping rainfall and tidal peaks was consistently smaller than under staggered peaks. Under the same return period, the peak flow rates at typical outlets Ⅰ, Ⅱ, and Ⅲ were significantly higher during high tidal levels compared to typical tidal levels, and the peak flow rates at all three outlets increased with higher return periods, with their peak occurrence times advancing gradually. The overlapping of rainfall and tidal peaks significantly reduced the peak flow rates at the outlets, with the greatest reduction observed under the 50-year return period scenario.

Abstract:To investigate the impact of flood discharge-induced atomized rainfall on the safety and stability of accumulation slopes in dry-hot valley regions, a fully coupled model of flood discharge-induced atomization, surface runoff and seepage of complex slope was established based on the water-air two-phase flow theory. The Eulerian two-fluid model was adopted to describe the motion of water and air during flood discharge, and the coupling relationship between slope seepage and surface runoff was explicitly considered, enabling the numerical solution of the water-air flow process. The results show that the developed coupled model transforms the flux boundary between seepage and runoff into an internal boundary of the model, thereby overcoming the computational challenges caused by inaccurate boundary condition specification. For accumulation slopes, atomized rainfall primarily forms surface runoff, which is characterized by short formation time, high runoff volume, and rapid dissipation. When the influence of surface runoff on slope seepage is taken into account, the rainwater infiltration depth and volume within the slope body generally exhibit an increasing trend.

Abstract:The distribution characteristics, hydrochemical types, and variation trends of major chemical components in shallow groundwater within the transition zone of the middle-lower Yellow River (Jili-Mengjin reach) were analyzed using mathematical statistics, Piper diagrams and Schoeller diagrams. The controlling factors and primary sources of these components were identified through the Gibbs model, ionic ratio analysis and factor analysis, and the hydrochemical evolutionary patterns of shallow groundwater were verified through the profile method. The results show that there is a close hydraulic connection between shallow groundwater in the transition zone of the middle-lower Yellow River and Yellow River water. The hydrochemical composition of groundwater is predominantly controlled by rock weathering (primarily carbonate rocks), and is also influenced by evaporation and human activities to a certain extent. Cation exchange processes and mineral exploitation activities lead to a dynamic saturation state of carbonate minerals in groundwater within the river valley plain. The hydrochemical types of shallow groundwater in the transition zone of the middle-lower Yellow River are relatively complex, evolving from the HCO₃-Ca·Mg type in the loess hilly area to the HCO₃·SO₄-Ca·Mg and HCO₃·Cl -Ca·Mg types in the Yellow River floodplain area, and further transitioning to the HCO₃·SO₄·Cl-Ca·Na·Mg, HCO₃·Cl -Ca·Mg·Na and HCO₃·Cl·SO₄- Mg·Ca·Na types.

Abstract:In order to solve the issues of noise interference in the prototype monitoring data of concrete dams and the difficulty in optimizing the numerous hyperparameters of intelligent algorithm used for deformation prediction, a concrete dam deformation prediction model is proposed based on the ensemble empirical mode decomposition (EEMD), artificial fish swarm algorithm (AFSA) and convolutional neural network (CNN). This model uses EEMD to decompose the original dam deformation data to obtain the intrinsic mode function (IMF), and utilizes the wavelet threshold denoising method to denoise the noisy IMF components and reconstruct the components. The hyperparameters of the CNN model are optimized using the AFSA, and the reconstructed data is trained with the optimized CNN model. The trained model is subsequently used for prediction. The validation results from a case study of a high arch dam show that, compared with models such as CNN, extreme learning machine (ELM) and back propagation (BP) neural network, the proposed model exhibits higher accuracy and stronger stability in concrete dam deformation prediction.

Abstract:To address the issue of degraded predictive model performance caused by high-dimensional breach features and strong correlations among features, a peak discharge prediction model for earth-rock dam breaches was developed by integrating the Lasso algorithm with the XGBoost model. This model uses the Spearman correlation coefficient method to analyze the correlations between features, utilizes the Lasso algorithm for further feature selection, and obtains an optimal feature subset by eliminating redundant features. The feature subset is input into the XGBoost model to predict the peak breach discharge. Comparative results with support vector regression and ridge regression machine learning models show that the proposed model exhibits strong nonlinear information mining capability, effectively reduces the dimensionality of high-dimensional features, and improves the prediction accuracy while reducing model complexity.

Abstract:Based on the subgrade project of Jiyuan-Xin’an Expressway, a field test of compaction and reinforcement of high-fill loess embankment was designed and conducted, the reinforcement effects and influence depth of two reinforcement schemes, namely dynamic compaction and impact rolling, were discussed, and the finite element method was used to further optimize the construction parameters for the impact rolling scheme with better field reinforcement effect. The results show that the influence depth of dynamic compaction reinforcement ranges from 4 to 6 m, while that of impact rolling reinforcement ranges from 2 to 4 m. Within the influence depth range, the reinforcement effect of soil improves with an increase in dynamic compaction or rolling times, but the increase gradually decreases, indicating an optimal dynamic compaction or rolling time. According to the construction parameters of the in-situ test, impact rolling reinforcement after a 2-m fill height is more effective in improving the compaction degree and uniformity of the subgrade compared to dynamic compaction reinforcement after a 4-m fill height. The influence depth of impact rolling reinforcement increases with the rolling time, reaching up to 3 m after 20 times. Both the compaction effect and influence depth increase with the mass of the impact wheel but first increase and then decrease with an increase in the traveling speed of the impact wheel. The optimal traveling speed of the impact wheel is 3 m/s.

Abstract:To evaluate the effectiveness of conservation tillage in mitigating soil erosion at a regional scale in the black soil zone of Northeast China, a SWAT model was developed for the Hulan River Basin in Heilongjiang Province. Eight simulation scenarios were designed to investigate the effects of none/reduced tillage seeding, straw returning, subsoiling and their combinations on rainfed cropland soil erosion. The results indicate that the SWAT model performs well in simulating runoff and sediment yield during both the calibration and validation periods. The Nash-Sutcliffe efficiency (NSE) values for runoff were 0.90 and 0.97, with percentage bias (PBIAS) values of 9.59% and -12.63% during the calibration and validation periods, respectively. The NSE values for sediment yield were 0.75 and 0.64, with PBIAS values of -0.63% and -15.43% during the calibration and validation periods, respectively. During the crop growing season from May to September, the soil erosion in rainfed cropland first increased and then decreased, with higher erosion in July and August and lower erosion in May. In terms of erosion control effectiveness, straw returning showed the best performance, followed by none/reduced tillage seeding, whereas subsoiling was less effective and even intensified soil erosion in April, May and September. Therefore, straw returning is recommended as the priority conservation tillage practice, followed by none/reduced tillage seeding. When multiple practices are integrated, the combination of straw returning and none/reduced tillage seeding is recommended.

Abstract:To elucidate the local scour characteristics and evolutionary patterns of bridge piers under ice cover, a series of flume tests were conducted to investigate the combined effects of ice, water, and sand interactions around piers under ice-covered conditions on local scouring. The dominant factors influencing scour morphology were thereby identified. The test results show that the scouring of the local scour hole of the pier under the rough ice cover condition was the most significant, followed by the smooth ice cover condition, indicating that the influence of ice cover roughness on the scouring depth and range should not be neglected. The Reynolds number of the water flow has a predominant effect on the local depth of the scour hole, and plays a dominant role in controlling the development of the scour hole. The scour hole was slightly larger in the longitudinal range than in the transverse range, resulting in an elliptical shape, indicating that the scour hole development in the transverse direction lags behind the development in the longitudinal direction. The low-frequency pulsations in instantaneous velocity time series originate from large-scale vortices, while the high-frequency pulsations are determined by small-scale vortices.

Abstract:To investigate the evolution characteristics of the interface strength of geosynthetics, a large-scale ultraviolet (UV) aging model test chamber was used to conduct aging tests on geomembrane (GMX) and geotextile (GT) for up to 80 days and 40 days, respectively. Periodically collected aged specimens were utilized to perform temperature-controlled direct shear tests on GMX-sand, GT-sand, and GMX-GT interfaces. The influence of UV aging on the shear strength of these three interfaces was quantitatively analyzed. The results show that UV aging has a stronger effect on the shear strength of the GMX interface than on the GT interface. Furthermore, the shear strength of the aged GMX-GT interface exhibits a trend of initial increase followed by a decrease with prolonged UV aging time.

Abstract:To address the lack of effective methods for evaluating the operation status of pump stations, as well as the high uncertainty and result distortion associated with traditional weighting and evaluation approaches, an evaluation method for pump station operation status based on improved combined weighting method and cloud model is proposed. An evaluation indicator system is constructed, consisting of three criteria: safety status monitoring, technical performance, and operational economy. The subjective weights are determined using the fuzzy AHP-DEMATEL method, while the objective weights are obtained through the CRITIC method based on historical operation data of the pump station. The combined weights are then derived by integrating the subjective and objective weights, and the operation status of the pump station is finally evaluated through the cloud model. Application examples verify that the proposed method can effectively handle uncertainty and fuzziness in the evaluation process. It can be applied to digital twin pump station systems, enabling integrated management of monitoring, evaluation, and early warning.

Abstract:Aiming at the mismatch problem in the operation process existing in reservoir scheduling plan management, a reservoir optimal operation model based on scheduling plans was proposed. This model takes the objective functions of minimizing water shortage for water users and minimizing deviation from power generation plans. The particle swarm optimization algorithm was used to optimize the power generation plan. The model was used to analyze the matching degree between the water supply and power generation processes, the change of reservoir storage capacity, and the monthly benefit transfer relationship of power generation capacity of the Dalong Reservoir in Sanya City. On the premise of ensuring the water supply plan, the deviation of the optimized power generation plan at 50%, 75%, and 90% inflow frequencies decreased from 0.144, 1.961, and 3.033 to 0.131, 0.566, and 1.404, respectively. The power generation increased by 0.02 million, 5.6 million, and 4.7 million kWh, respectively. This indicates that adjusting the power generation and water supply processes can effectively improve the rationality of the scheduling plan.

Abstract:A study on the compressibility of high-water-content mud treated by the physicochemical composite method under different initial conditions was conducted through one-dimensional compression tests. The effects of the total duration of step loading, curing time, dosage of solidifying agent, and dosage of flocculant on the compression curve, compression index, and yield stress of the mud were investigated. The concept of the intrinsic compression curve was introduced to normalize the compression data, enabling further analysis of the compressibility of the mud under different initial conditions. The results show that the compression curve of the mud treated by the physicochemical composite method exhibits a distinct two-stage characteristic, with the post-yield compression index being approximately 20 times that of the pre-yield compression index. The yield stress of the mud increases linearly with the increase in solidifying agent dosage and the decrease in the total duration of step loading. The yield stress of the mud follows a logarithmic growth pattern with prolonged curing time. There exists an optimal dosage of flocculant that maximizes dewatering efficiency and enhances structural strength.