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.
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.
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.
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.
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 kW∙h,respectively.This indicates that adjusting the power generation and water supply processes can effectively improve the rationality of the scheduling plan.
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.
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.
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.
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 119800 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.
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.
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.
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.
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.
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.
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.
By early 2025,the number of completed and under-construction rock-filled concrete(RFC)dams had reached 200.Among them,the Zhouyuan RFC gravity dam with a height of 100 m had commenced construction.Concurrently,the Code for Design of Rock-Filled Concrete Dams(NB/T 10077-2024)was issued.These events indicate that RFC dam construction technology has achieved maturity after more than 20 years of development.The development process of RFC dam construction technology from its initial invention to gradual maturity was reviewed and divided into four key stages,the main technical problems and research achievements obtained in different stages were introduced,the main progress on fundamental research related to RFC was summarized,and the construction status of typical RFC dams as well as the continuous development and improvement process of the technical standard system for RFC dams were presented,so as to help readers better understand the evolution of RFC dams,point out the direction for future development,and promote the progress of RFC dam technology.
To elucidate the coupling evolution mechanism of argillization and permeability in fault fracture zone filling materials driven by reservoir water seepage pressure,research progress on geological characteristics,experimental methods,and degradation mechanisms was systematically reviewed.Under in-situ high tectonic stress constraints,compressible faults exhibit a"fault core-failure zone"zonal structure.The low-permeability barrier within the core,which is rich in clay minerals,is susceptible to mineral softening and argillization under prolonged seepage pressure,resulting in an increase in permeability by three to five orders of magnitude.In-situ high-pressure water injection tests can capture the inhibitive effect of tectonic stress on fracture closure.In contrast,traditional laboratory tests often fail to accurately simulate realistic seepage pathways due to weakened cementation effects and stress release-induced distortions.The argillization of clay minerals leads to pore reconstruction,while fine particle content significantly increases the initiation pressure gradient through mechanisms such as flocculation cementation and"water film"effects.Seepage pressure-driven degradation follows a pattern wherein water seepage pressure promotes the penetration of seepage channels by propagating original fractures and accelerating particle migration and loss,ultimately leading to a notable reduction in the critical hydraulic gradient.
From the perspective of risk transmission process of basin water resources security,this paper systematically analyzes fundamental concepts,including the water resources security system,water resources security risk system,and water resources security risk assessment.The conceptual framework for water resources security risk assessment is proposed,which is characterized by an Aristotelian syllogistic relational structure and encompasses five elements:the hazard of risk-inducing factors,the vulnerability of risk-bearing bodies,the risk-inducing potential of hazardous environment,the risk-resistance capacity of mitigation measures,and the water resources security loss risk.This paper reveals the transmission mechanism of water resources security risk elements,where under specific risk-incubating and risk-resisting conditions in a watershed,the hazard of risk-inducing factors serves as the system input,the vulnerability of risk-bearing bodies as the system transition,and the water resources security loss risk as the system output.This paper elaborates on methodology for water resources security risk assessment,consisting of water resources security risk assessment objects,evaluation indicators,evaluation indicator measurement methods,methods for quantifying qualitative indicators,single-indicator evaluation methods,methods for determining indicator weights,and methods for determining comprehensive evaluation indicators.The theoretical framework composed of the conceptual system,risk transmission mechanism,and risk assessment methodology forms a preliminary theoretical foundation for water resources security risk assessment.This theoretical framework also holds significant application value for risk assessment in other resources and environmental systems.
Through a systematic review of research progress on mechanical test equipment for soil-structure interfaces,key influencing factors,numerical simulation methods,and constitutive models,the engineering applicability and technical limitations of current test equipment were analyzed,the response laws of interface mechanical properties under the influence of multiple factors were clarified,the key technologies and theoretical limitations in existing numerical simulations were summarized,and the applicable ranges and boundary conditions of commonly used constitutive models were classified.In light of the actual engineering needs and technological development trends,future research should focus on developing intelligent testing systems with integrated stress-seepage-temperature multi-field coupling functions,revealing the time-varying laws of interface mechanical properties under long-term complex environments and multi-field coupling,improving the numerical simulation method system based on the thin-layer element theory,and constructing intelligent constitutive models integrating machine learning algorithms and multi-source engineering data to enhance the accuracy and adaptability of interface mechanical behavior prediction under complex conditions.
Weakly mixed land-dominated estuaries are susceptible to the combined influences of fluvial water-sediment fluxes,marine dynamics,and anthropogenic activities,resulting in complex dynamic changes in hydrological connectivity.However,a systematic synthesis of hydrological connectivity in such estuaries is still lacking.Therefore,taking the Yellow River Delta,a representative weakly mixed land-dominated estuary in China,as an example,based on the classification of structural connectivity and functional connectivity,the spatiotemporal patterns,evolutionary trends,and driving factors of hydrological connectivity in tidal flat wetlands were analyzed,and the bidirectional feedback mechanisms between the hydrological connectivity and water-sediment dynamics were emphatically explored.It is pointed out that future research should focus on three directions,including integrating rivers,tidal creeks,and surface-groundwater systems to establish a multi-scale hydrological connectivity framework for entire tidal flat wetlands,enhancing synergistic analysis of field monitoring and numerical models to systematically analyze the feedback mechanisms between hydrological connectivity and water-sediment dynamics in weakly mixed estuaries,exploring nature-based and society-based solutions to improve hydrological connectivity,and establishing synergistic optimization strategies that concurrently enhance hydrological connectivity and restore wetland ecological function,thereby providing practical paradigms for integrated estuary management.
