When upstream and downstream water regime changed in long-distance pressurized water delivery pipeline of cascade pump stations, it is easy to cause the change of water pressure in pipeline and hydraulic parameters such as flow velocity, and results in water hammer. In order to meet the water delivery requirements of the pipeline and ensure its safe operation under various working conditions, one-dimensional characteristics method and 3D VOF coupled methods were used to simulate. The mathematical model for transient process analysis of long-distance water delivery system of cascade pump stations was established to analyze the change and law of pipeline internal pressure and water level in outlet pool during long-distance water delivery system in Chuhe Level Ⅳ station of Simashan River Diversion Project under working conditions, such as suspending period and power losing period. It also shows that the safety of the entire pipeline system can be better guaranteed though the reasonable open-close laws of the terminal gate and side gate.

The downstream surge chamber of a certain pumped storage power station adopts impedance with upper chamber layout. The tailrace tunnel is connected with the connecting pipe through right angle bifurcated pipe and bend. The layout type is special and the water flow conditions are complex. In order to study its hydraulic characteristics, a three-dimensional flow field mathematical model of the connecting pipe at the bottom of the surge chamber was established, and the variation law of hydraulic characteristics under different diversion ratio and confluence ratio was studied. The results show that for the resistance loss of surge chamber with complex bottom flow, the three-dimensional numerical simulation can achieve better simulation effect, and the calculation results are in good agreement with the theoretical analysis results. Because the elbow at the bottom of the surge chamber, the sudden expansion and contraction between the connecting pipe and the big well will cause additional hydraulic losses, its head loss coefficient is greater than that of the conventional impedance surge chamber, and the flow coefficient is smaller than that of the separate impedance hole.

The purpose of the paper is to explore connection mechanism between interval time and pressure at draft tube inlet in successive load shedding case. Based on transient flow theory and method of characteristics, numerical simulation calculation of transition process in the successive load shedding case for pumped storage power station with layout of two turbines and one tunnel was carried out. The relationship between flow rate, running track of turbines and minimum pressure at draft tube inlet was analyzed. The result shows that there is a certain most unfavorable interval time making the time-domain asynchronous degree of first wave flow rate in two turbines maximized and the pressure at draft tube inlet is the minimum. At the same time, running track point of the first load shedding turbine is near the upper bending point in the inverse S-region of characteristic curve and running track point of the last one is near the lower bending point. The conclusion can provide a reference for calculation of extreme value of pressure at draft tube inlet in the pumped storage power station.

To address the problem of excess pressure in the water supply network system, this paper proposed to add pressure reducing valves with certain opening in the system. With the objective of minimizing the square sum of the difference between the operating water pressure at each node and the minimum service head at the node, the pressure reduction valve optimized pressure leakage control model was constructed by combining the hydraulic balance constraint of the pipe network and the node pressure constraint. The model was solved by using genetic algorithm. Taking the main water supply network of southeast coastal towns as an example, the results show that the proposed model and method are effective and feasible, and it has better optimal effectiveness.

The outlet area of river diversion tunnel in mountainous areas is characterized by large discharge per unit width, high flow velocity, deep riverbed overburden and low anti-scour flow velocity. The river bed at the outlet of the tunnel is severely scoured, and it is difficult to arrange large energy dissipation measures, so it is proposed to arrange small flip bucket at the outlet of the tunnel. On the basis of the physical model test to observe the flow pattern and river bed scouring in the outlet area of the tunnel, the numerical simulation method is used to calculate the flow field in the outlet area of the diversion tunnel, and the internal mechanism of the improvement of river bed scouring is studied. The results show that after adding a small flip bucket at the outlet of the diversion tunnel can increase the lateral diffusion of the high-speed flow out of the tunnel, reduce the unit width discharge, increase the local energy dissipation rate, and thus reduce the velocity of the river bank. The proportion of water body coming out of the tunnel with high flow velocity is obviously reduced, which makes the high-speed water flow unable to directly rush the landslide mass on the right bank, and reduces the flow velocity within the landslide mass. The width of water flow out of the tunnel increases, and the direction of water flow out of the tunnel becomes inclined upward, which weakens the impact on the landslide on the right bank, and significantly weakens the scouring of the outlet area of the diversion tunnel and the downstream river channel. This study can provide reference for engineering practice.

In order to verify and optimize the “dragon-drop-tail” layout plan of the No. 1 flood discharge tunnel in the expansion project of the Chentianhe Reservoir, a numerical calculation model for the discharge was established. The numerical feedback of cavity backwater behind the airfoil flip bucket of indoor experiment was made use of to calculate the rationality of the numerical model. The optimal objective function of the shape of the airfoil flip bucket was identified based on the principle of safety and economy. The feedback model was then used to optimize the layout of aeration devices. The research shows that results of the simulation which adopts the FAVOR and Tru-VOF methods of structured rectangular grids, the RNG κ-ε turbulence model and the numerical model of fine grid are in line with indoor experiment results in terms of cavity shape and length. The optimal values of the bucket angle α and slope rate of the bottom slope behind the airfoil flip bucket θ of the No.1 flood discharge tunnel are 10% and 20%, respectively.

Due to the lack of measured temperature on the channel surface, it is difficult to accurately simulate the channel temperature field. Considering the effect of solar thermal radiation on the temperature of the shady slope, sunny slope and bottom slab of the channel, a calculation model of channel surface temperature increase was established. The finite element software ABAQUS was used to simulate the temperature field change process of the channel and analyze the frost heave of the channel lining under the condition of three times of cooling. The results show that under the influence of solar thermal radiation, the freezing depth of the shady slope of the channel is significantly greater than that of the sunny slope and the bottom slab, the calculated freezing depth and the damage law of the lining are also in good agreement with the actual situation. During the cooling process, the concrete lining of the shady slope is more prone to frost damage than that of the sunny slope and the bottom slab, the same rule applies when calculated according to the multi-year maximum freeze depth utilization specification. The research results can provide new ideas for the temperature control and crack prevention design of channel concrete lining.

For the value of the surrounding rock parameters of the underground construction, a hybrid network approach combining backtracking search optimization algorithm (BSA) and BP neural network (BSA-BP) was proposed for the inversion study of the tunnel surrounding rock parameters. By establishing a tunnel finite element excavation model, the inversion parameters were used to calculate the displacement of the monitoring section and compare with the measured values in the field. Finally, the stability of the surrounding rock was analyzed and predicted. Compared with the GA-BP neural network, the results show that the BP neural network optimized by BSA algorithm has faster inversion speed and computational efficiency. The relative errors between the calculated displacement values and the field measured values obtained by using BSA-BP neural network inversion parameters are within 5%, indicating that the model has high inversion accuracy and is reasonable and feasible. The research results provide a new method for the inversion of underground engineering parameters.

The underground powerhouse of Henan Wuyue Pumped Storage Power Station has a complex structure of caverns. The main powerhouse has a maximum span of 26.0 m and a height of 55.1 m, which is a large underground chamber. The rock mass structural planes are developed and the strength is low. The fault F1 runs through the three powerhouse, and the safety problems are prominent. The stability of surrounding rock after excavation should be analyzed. Therefore, FLAC^3D program was used to establish the geological model. The BSA-BP neural network was used to calculate the initial in-situ stress field of the area. And then the excavation of underground powerhouse was simulated. The stress field, displacement field and plastic zone development and distribution law of surrounding rock were analyzed. The results show that the surrounding rock of underground powerhouse caverns group is basically stable. However, local deformation and failure may occur in the fault development area and at both ends of the busbar hole. The research results can provide guidance for the design and construction of the project, and provide some reference for similar projects.

The risk assessment of collapse of tunnel involves many fuzzy factors and the evaluation method is complex, which makes the evaluation system constitute a gray system and the applicability of the evaluation method is not high. It is difficult to accurately assess the risk level of tunnel landslides. Using the basic idea of gray system and vector projection principle, a set of tunnel collapse risk evaluation model based on gray vector projection method is proposed. Based on the comprehensive analysis of the influencing factors of tunnel collapse under complex stratigraphic conditions, the group analytic hierarchy process (GAHP), which takes into account the degree of difference in the views of decision makers, is used to reduce the dimensionality of the pre-selected evaluation index system. Then, according to the comprehensive decision weight coefficient, 13 preferred evaluation indicators that can fully reflect the different, representative and highly differentiated evaluation indicators of the collapse mechanism are selected to establish a tunnel collapse risk optimal evaluation index system. In addition, grey group clustering (GGC) and anti-entropy weight (AEW) are introduced to determine subjective and objective single-level sorting weights, respectively. The improved combination weighting method of game theory (ICWGT) is used to obtain the optimal comprehensive weight distribution coefficient to determine the total ranking weight of the indicator. Finally, according to this model, the risk of collapse of five groups of tunnels was evaluated by the model. The results show that the risk assessment level of tunnel collapse is highly consistent with the actual excavation. The reliability and accuracy of the model are verified.