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.
