Channel engineering stability with underground goafs is a complex three-dimensional problem, especially when considering channel leakage, and is influenced by a number of processes, such as seepage, fluid structure interaction (FSI), modeling, and selection of geological mechanical parameters. In this study, stability finite element analysis by one-way FSI was performed by establishing an integrated 3D engineering geological model. The extended Fourier amplitude sensitivity test was used to quantitatively assess the first-order and total sensitivities of the engineering model to critical geological mechanical parameters. Results illustrate that the channel engineering deformation is under a reasonable range and the elastic modulus is the highest total sensitivity parameter for the channel tilt and curvature at 0.7395 and 0.7525, respectively. Moreover, the most observable coupling effects for the curvature and horizontal strain are cohesion (0.1933) and density (0.7410), respectively.

Previous studies at home and abroad have mainly focused on single dam-break, and little attention has been paid so far to the dam-break of cascade reservoirs. Multi-source flooding, which can lead to three-dimensional turbulent phenomena and superposition effects, is the main difference between the dam-break of cascade and single reservoirs. Detailed descriptions of the coupled numerical simulation of multi-source flooding have little been reported, and the initial wet riverbed is rarely considered in current models. Therefore, in this paper, a method based on the three-dimensional \(k - \varepsilon\) turbulence model coupled with the volume-of-fluid method is proposed to simulate the dam-break flooding of cascade reservoirs. The upstream river, reservoir, and downstream river are connected by the internal boundary method, and the initial conditions, including river flow and reservoir water, are determined according to the results of the numerical simulation. Coupled numerical simulation of different dam-break flooding is then achieved. The present work solves the challenges presented by the enhancement and superposition of natural river flow, upstream flooding, and downstream flooding. This paper provides a theoretical basis for future studies on the dam-break flood routing of cascade reservoirs.

Nonpoint storm runoff remains a major threat to surface water quality in China. As a paddy matures, numerous fertilizers are needed, especially in the rainy seasons; the concentration of nitrogen and phosphorus in rainfall runoff from farmland is much higher than at other times, and this poses a great threat to water bodies and is the main reason for water eutrophication, especially in high concentration drainages. To date, most studies regarding the characteristics of pollutants in rainfall runoff have mainly been concentrated on urban runoff and watershed runoff; therefore, it is particularly important to investigate the characteristics of nitrogen and phosphorus loss in rainfall runoff from paddy fields. To study the characteristics of nitrogen and phosphorus loss and whether the first flush effect exists, continuous monitoring of the rainfall runoff process of six rainfall events was conducted in 2013, of which four rainfall events during storm, high, middle, and low intensity rainfalls were analyzed, and runoff and quality parameters, such as suspended solids (SS), total nitrogen (TN), ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), total phosphorus (TP), and phosphate (PO43−-P), were analyzed to determine the relationship between runoff and water quality. The paddy field is located north of Wuxi Lake Basin along the Hejia River upstream in Zhoutie town, Yixing city. An analysis of the load distribution during rainfall runoff was conducted. Event mean concentration (EMC) was used to evaluate the pollution situation of the paddy field’s rainfall runoff. A curve of the dimensionless normalized cumulative load (L) vs. normalized cumulative flow (F) (L-F curve), the probability of the mass first flush (MFFn), and the pollutants carried by the initial 25% of runoff (FF25) were used to analyze the first flush effect of the paddy field runoff, and different contaminants show different results: the concentration of nitrogen and phosphorus fluctuate and follow a similar trend as runoff changes, NO3−-N concentration is lower in the early part of runoff and higher in the later, and TP mainly occurs in the particle state in storm runoff and mainly in the dissolved state when the rainfall intensity is smaller. Nitrogen and phosphorus losses from paddy fields are closely related to the average rainfall intensity and the max rainfall intensity, and the runoff loss of nitrogen and phosphorus is more severe when the rainfall intensity is large. Based on an analysis of multiple methodologies, TN and NH4+-N show a certain degree of a first flush effect, whereas the first flush effect of TP is not obvious. The first flush effect of SS is obvious in larger intensity rainfall and shows a slight secondary flush effect in smaller rainfall events.

•A porosity- and reliability- based compaction quality evaluation method is developed.•Data rely on the real-time monitoring system for construction quality and spot tests accumulated during construction.•An artificial neural network based on elitist genetic algorithm for porosity prediction is established.•Reliability can reflect variability in the compaction system and the impact of variability on compaction quality evaluation.•The proposed method considers the material source parameters and their variation.Compaction quality evaluation of concrete-faced rockfill dams (CFRDs) is a complex nonlinear process. Conventional evaluation methods depend on random spot tests, and porosity is considered as the main evaluation index. However, reliability of results is neglected in existing studies. Considering compaction parameters, material properties and their variability characteristics, an evaluation approach of CFRD compaction quality based on porosity and reliability is proposed. Reliability analysis is introduced to measure the variability in highly variable factors and calculate the porosity- and reliability-based index. Porosities of the entire work area are predicted using an elitist genetic algorithm-based artificial neural network, which are consistent with the measured values with an error < 5%. Data used in this study are based on the results from the real-time monitoring system for construction quality and spot tests accumulated during construction. The applicability of the proposed approach is demonstrated by an illustrative case study in China.

In the present study, considering the transport and transformation processes of variables, a three-dimensional water quality model for the river system was established, which coupled the volume of fluid (VOF) method with the k-ε turbulence mathematical model. Then, the water hydrodynamic characteristics and transport processes for BOD5, NH3-N and TP were analyzed. The results showed that the water surface of convex bank was a little lower than that of concave bank due to the centrifugal force near the bend, and most concentrations were inferior to the type V standard indexes of surface water environmental quality. The model validation indicated that the errors between the simulated and monitored values were comparatively small, satisfying the application demands and providing scientific basis and decision support for the restoration and protection of water quality.

The optimal evacuation scheme is studied based on the dam-break flood numerical simulation. A three-dimensional dam-break mathematical model combined with the volume of fluid (VOF) method is adopted. According to the hydraulic information obtained from numerical simulation and selecting principles of evacuation emergency scheme, evacuation route analysis model is proposed, which consists of the road right model and random degree model. The road right model is used to calculate the consumption time in roads, and the random degree model is used to judge whether the roads are blocked. Then the shortest evacuation route is obtained based on Dijstra algorithm. Gongming Reservoir located in Shenzhen is taken as a case to study. The results show that industrial area I is flooded at 2 500 s, and after 5 500 s, most of industrial area II is submerged. The Hushan, Loucun Forest and Chaishan are not flooded around industrial area I and II. Based on the above analysis, the optimal evacuation scheme is determined.

The lack of knowledge on water flow and particle behavior of sandstone wastewater in sedimentation tanks of hydropower stations is a significant challenge for the design of these processes. In this study, the Euler−Lagrange two-phase model was applied to study the flow, sedimentation, and particle trajectories in a two-stage rectangular tank that is divided into two sections with different hydraulic retention times. The interfacial momentum transfer, buoyant force, and the collision force were considered, and the Lagrange approach was employed to determine the particle trajectories of the particles. The flow patterns, removal efficiency of the particles, and particle trajectories along the tank were investigated. The experimental and numerical results revealed that the two-stage rectangular tank is efficient in dealing with high turbidity sandstone wastewater. In addition, the simulated removal efficiencies were in good agreement with the experimental results. Last, the sensitivity of particle behavior to the collision force was studied, and the effect of the baffle length on particle settling in the rectangular sedimentation tank was evaluated.

Under forced ventilation, the dust diffusion of underground powerhouse construction is investigated using a 3D high Reynolds number k-ɛ model. The interfacial momentum transfers and the wall roughness in the wall function are considered. Ventilation in the third layer of underground powerhouse of Xiangjiaba hydropower station is used as a case. The geometric structure has a decisive effect on the airflow distribution. It is concluded that the dust concentration decreases gradually with the increase of the ventilation time. However, iso-concentration curves have the same tendency after 1 800 s. The dust concentration meets the ventilation and dust-prevention health standard after 2 300 s. The prediction by the present model is confirmed by the experimental measurement by Nakayama.

Ice in diversion channels can cause adverse effects that jeopardize the operational safety of diversion hydropower stations in the cold regions of northwest China. Previous studies have relied on experimental studies and one-dimensional or two-dimensional numerical simulations. In this paper, a three-dimensional Eulerian two-phase flow model is presented. The influence of the liquid–solid interaction, which includes the inter-phase drag force, lift force, virtual mass force, buoyancy force and the volume fraction of ice, was taken into consideration in the model. The simulated results showed that the surface flow and the frazil ice in the bend channel tended toward the concave bank. Additionally, the optimum scheme was obtained by comparing the layout pattern and structure modification. The simulated results were in good agreement with the experimental study done by Blanckaert and Graf (2001), and the intake flow was validated with an empirical value.Highlights► CFD simulation of ice sluice in diversion water channel was made. ► A 3-D Eulerian two-phase flow model simulated the bend-type ice sluice. ► Comprehensive influence among ice removal quantity, and interaction between ice and water were considered. ► Optimum scheme was obtained by comparing layout pattern and structure modification.

In this study, a fuzzy stochastic two-stage programming (FSTP) approach is developed for water resources management under uncertainty. The concept of fuzzy random variable expressed as parameters’ uncertainties with both stochastic and fuzzy characteristics was used in the method. FSTP has advantages in uncertainty reflection and policy analysis. FSTP integrates the fuzzy robust programming, chance-constrained programming and two-stage stochastic programming (TSP) within a general optimization framework. FSTP can incorporate pre-regulated water resources management policies directly into its optimization process. Thus, various policy scenarios with different economic penalties (when the promised amounts are not delivered) can be analyzed. FSTP is applied to a water resources management system with three users. The results indicate that reasonable solutions were generated, thus a number of decision alternatives can be generated under different levels of stream flows, α-cut levels and different levels of constraint-violation probability. The developed FSTP was also compared with TSP to exhibit its advantages in dealing with multiple forms of uncertainties.