The phased trend recognition of deformation monitoring sequences for dams can deepen the understanding of the evolution laws of deformation monitoring sequences at different time scales, which is of great significance for the safe operation and management of dams. The heuristic segmentation algorithm (BG algorithm) is adopted to identify the mutation points of deformation monitoring sequences for dams, which can effectively avoid the interference of mutation points in trend recognition. On this basis, the segmented sub-sequences are trend identified using an improved ITA method, which can retain the internal correlation of the sequences and has good applicability. The engineering case analysis shows that the proposed method can effectively identify the mutation points in the deformation monitoring sequences for dams, divide the monitoring sequences into sub-sequences with stable trends, and identify the changing trends of each sub-sequence.

In order to study the characteristics of the hydraulic transition process of accidental pump stoppage before and after the pipeline optimization of pumping station water delivery system, based on the actual project, Bentley Hammer software was used to establish a mathematical model of the pumping station water delivery system with two pumps in parallel units to study the effects of the most unfavorable water hammer parameters such as water hammer pressure and unit speed before and after the pipeline optimization under different two-stage valve shutdown schemes. The results show that the maximum water hammer pressure decreased by 3.76%-8.85%, the minimum water hammer pressure increased by 4.89%-8.85%, and the maximum reversal speed increased by 1.47%-81.35% after pipeline optimization; The fast shutdown time had a significant effect on the most unfavorable water hammer parameters, and the most unfavorable water hammer parameters of the pumping station water delivery system all occurred before than before the optimization after pipeline optimization. It shows that the pipeline optimization effectively improved the water hammer characteristics and the safety of the pumping station water delivery system.

For the pump-stopping water hammer prevention of the floating pumping station water-conveying system, in addition to ensuring the safety of the pump unit and the pipeline, the impact of the water hammer pressure on the movable rocker pipe and the floating boat should be considered to ensure the stability of the floating boat. The numerical simulation of the pump-stopping transient of a floating pumping station water-conveying system under large range variable water source level was conducted. The results show that the lowest inlet water level is the most unfavorable condition for water hammer prevention. Under the condition that the pump outlet valve refuses to close, if the unit’s reverse speed exceeds the standard and the maximum reverse flow is reached within 3 s after the pump-stopping. The axial-flow check valve is recommended for the pump outlet valve considering the valve driving capacity requirements, the unit reverse speed and water hammer pressure. In the water hammer protection scheme of "pump outlet axial-flow check valve + air chamber on shore + intermediate check valve + hammer-prevention air valve", the axial-flow check valve ensures that the pump unit does not reverse, the air chamber and air valve reduce the maximum water hammer pressure and improve the negative pressure condition in the pipeline, and the intermediate check valve reduces the pressure oscillation amplitude and oscillation time in the pump outlet and rocker pipe. Therefore, the water hammer prevention problem in the floating pumping station water-conveying system is effectively solved.

The friction factor of pipeline is a key parameter in the design calculation, operation scheduling optimization and fault diagnosis of water supply system. In order to determine this parameter accurately, an intelligent back-analysis method of pipe section friction factor based on dynamic search fireworks algorithm (dynFWA) coupled with hydraulic calculation model of pipe network was proposed. The partial derivative relationship between node water pressure and friction factor was taken as the node sensitivity. In the improved genetic algorithm, the maximum sum of node maximum sensitivity was taken as the goal to optimize the layout of monitoring points. Based on the optimized water pressure monitoring value at the monitoring point, the dynFWA algorithm was used to inverse the friction factor of each pipe section with the objective of minimizing the average double error between the water pressure monitoring value and the calculated value. In order to verify the inversion performance of dynFWA algorithm, the inversion of friction factor by dynFWA algorithm and particle swarm optimization (PSO) algorithm were compared. The results show that the maximum relative errors of the inverse value of the friction factor are 17.7% and 0.7% before and after the optimization of the monitoring points, which proves the necessity of the monitoring point selection and the superiority of the improved genetic algorithm for the monitoring point selection. Under the condition that the water pressure at the monitoring node is added to noise, the relative errors of the friction factor inversion results based on the dynFWA algorithm and the PSO algorithm are 9.67% and 14.33% respectively, and the maximum relative errors between the actual water pressure value and the simulated water pressure value at the monitoring point are 0.358% and 0.655%, which proves that the dynFWA algorithm has higher accuracy in the parameter inversion problem compared with the PSO algorithm.

The phenomenon of mixed free-surface-pressure flow exists in the process of water level variation in the lower reservoir (roadway group) of mine-type pumped storage power station, which directly affects the operation stability of the system and the hydraulic safety of the roadway group. Based on 3D numerical simulation technology of hydraulic system, considering the three controlling cases including lower reservoir water filling, load rejection and pumping power failure, the characteristics of the transition process of water flow in roadway group and the evolution law of related hydraulic parameters were analyzed, and its influence on the hydraulic safety of roadway group was evaluated. The research shows that there is no obvious unfavorable flow pattern in the initial water filling process of the lower reservoir (roadway group); For load rejection with dead water level of the lower reservoir, the water level of the regulating pool decreases by less than 0.4 m, and for pumping power failure with the normal water level of the lower reservoir, the water level of the regulating pool increases by less than 10.0 m; The roadway group can enter and exhaust normally during the transition process, and the hydraulic transitions in the roadway section is smooth including the possible free-surface-pressure flow; The regulating pool and the ventilation channel meet the requirements of hydraulic optimization to ensure the hydraulic safety of the roadway group.

Based on the spillway tunnel of Kangsu Reservoir Project, the RNG turbulence model and VOF model in FLOW 3D software was used to study the flow characteristics of the spillway tunnel. The flow velocity and relative energy dissipation rate under different conditions of the original design scheme was analyzed, and compared with the model test. The reliability of the numerical simulation was verified. In view of the problems in the original design scheme, such as the water-wing in the upstream transition section of the spillway tunnel, the far drive hydraulic jump in the stilling basin, and the downstream gully flow not returning to the channel, the modified scheme was proposed. The results show that the modified scheme can effectively reduce the water wing phenomenon, and can effectively reduce the downstream gully flow velocity and the riverbed scouring by adding multi-level energy dissipation, which can provide a reference for the design.

With the completion of a large number of major water conservancy projects with the characteristics of "high water head, large flow, and complex geological conditions", the environmental problems caused by flood discharge atomization have become increasingly prominent, and it is urgent to carry out research on mitigation technology of flood discharge atomization. The types of flip bucket have a direct impact on flood discharge atomization. Based on the methods of physical model test and numerical simulation calculation, the influence of flip bucket types on flood discharge atomization is studied. The results show that: under the same test conditions, the distribution of the nappe wind velocity of the continuous bucket is symmetrical along the two sides of the downstream axis, showing a unimodal distribution; and the distribution of the nappe wind velocity of the contraction bucket and the expansion bucket is approximately symmetrical bimodal distribution. The distribution of flood discharge rainfall is closely related to the type of the flip bucket. Compared with the continuous bucket, the number of the splashed water droplets of contraction bucket and expansion bucket is greatly increased. In the actual project, the purpose of reducing the influence of flood discharge atomization can be achieved by reasonably optimizing the types of flip bucket.

On the non-uniform sand river bed, the armor layer at the bottom of the bridge pier local scour pit will affect the maximum local scour depth of the bridge pier. Through a flume model experiment, the sediment gradation, relative coarseness, and non-uniformity of the armor layer at the bottom of the local scour pit on the bridge pier were studied. The results indicate that the median particle size of the sediment in the armor layer at the bottom of the local scour pit on the bridge pier increases with the increase of the local scour depth on the bridge pier, and its relative coarsening degree increases with the increase of the Froude number, while the degree of non-uniformity decreases with the increase of the Froude number. A formula for calculating sediment particle grading in the armor layer at the bottom of the local scour pit on the bridge pier has been proposed. The applicability and reliability of the proposed formula is verifies by the measured data.

In order to study the dynamic response of pipe-piercing dike under seismic load, taking a dike-crossing project in Guangdong Province as the research object, considering the interaction between pipeline and soil, a three-dimensional numerical simulation model of pipeline-dike was established. The simulation of foundation boundary spring-damper was realized through secondary development. The results show that under the action of 0.1g seismic acceleration, the vertical displacement of the dike increases with the increase of the height of the dike and decreases along the axis of the dike. The maximum displacement at the top of the pipeline is greater than that at the left and right ends. The stress distribution law of the pipeline is consistent with displacement, and the maximum stress of the pipeline is proportional to the thickness of the soil cover layer. The Mises stress at each point of the midpoint section of the pipeline through the dike is the largest, and the seismic capacity of the middle section of the dike is relatively weak. The stress and displacement near the midpoint section of the pipeline in the dike should be monitored in the seismic design of the subsequent dike project. This study has important practical significance to ensure the safe and stable operation of the dike-crossing project.

A study was performed on the stress characteristics of the urban emergency flood-control box—a new equipment made of polymer material. The finite element analysis method was used to study the stress, strain and deformation characteristics of the flood control box under different water retaining heights. The results show that the stress concentration area of the box is mainly appeared at the water retaining surface and the two sides; With the increase of the water retaining height, the difference of water level between inside and outside of box as well as the maximum stress and the deformation are gradually smaller. Compared with the ABS, LLDPE, HDPE and PP materials, the deformation of the flood control box with ABS material is relatively smaller under the same conditions. An optimization study was carried out on the scheme of the flood-control box. And the stress, strain and deformation of the optimization scheme under the same conditions are greatly improved. The maximum stress decreases from 16.09 MPa in the original form to 7.31 MPa in the optimized form, and the maximum deformation decreases from 0.78 cm to 0.13 cm. The mechanical characteristics of the box structure are obviously improved.