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The secant piled-bucket foundation (SPBF) is innovatively proposed to suit the large-capacity mainstream, which is optimized from a traditional foundation and consists of an upper pile cap and a lower bucket skirt. Compared with the pile foundation, the SPBF has great advantages and deserves further study. In this research, the bearing mode, bearing capacity and failure mode under various loads of SPBF in saturated clay have been fully studied. First, the small-scale model test in saturated clay is carried out to verify the finite element (FE) method; the deviation between the FE results and the test results under vertical load and horizontal–moment load is 10.65% and 10.25%, respectively. Next, the bearing mode of SPBF in engineering scales is investigated via FE method, the results indicating that the bearing mode of SPBF is similar to that of a prestressed tubular foundation. Finally, the bearing capacity and failure mode of SPBF are studied and the findings show that the vertical bearing capacity and horizontal–moment bearing capacity of SPBF is 96.53 MN and 1.62 MN, and the weak parts of SPBF are concrete of the pile cap and the anchor bolts, respectively. This paper provides support for design and further optimization in the future.

High-Frequency Pressure Fluctuation (HFPF) is an extensively observed hydraulic phenomenon in pumped-storage power stations and water conveyance projects. The investigation of the propagation characteristics of the pressure perturbation is of great significance for the safe operation of hydraulic facilities. In this study, a one-dimensional (1D)–three-dimensional (3D) coupling model is established based on the combination of the Method of Characteristics (MOC) and Computational Fluid Dynamics (CFD) and implanted in the open source software OpenFOAM. The established model in this study implants the dynamic mesh module into the original OpenFOAM solver sonicLiquidFoam and presents the complete solution procedure of the CFD model with the dynamic mesh considered. The vibration of the pipe walls modeled by the mesh motion is employed to numerically generate the HFPF in the hydraulic system, which could not be implemented in the traditional MOC model. The independence of the pressure perturbation in the pipeline system is validated by the time-domain pressure variation. The graphical method is applied to describe the multiple reflection and superposition characteristics of the traveling wave in a simplified hydraulic system. Based on this, the mechanism of the superimposed characteristic of the traveling and standing pressure waves in the hydraulic system are analyzed, and the theoretical superimposed time-domain processes and the variations of the pressure oscillation magnitude are analyzed and presented. The 1D–3D coupling method and the theoretical analysis method could be referenced by other complex hydraulic systems.

The construction of reservoir dams has changed the environment and natural properties of the river course, and deep-water reservoirs present an obvious phenomenon of thermal stratification. Low-temperature outflow water in spring and summer will have a negative impact on the downstream ecological environment. Therefore, it is necessary to take selective withdrawal measures to regulate low-temperature outflow water. The temperature-control curtain project has the advantages of low cost, convenient construction and wide application. Based on the topographic data, a laboratory test model for regulating outflow temperature by a temperature-control curtain is established. A high-power electric heating system is adopted to form a nonlinear thermal stratification. The accuracy of the test data is verified by the prototype observed water temperature. The main parameters affecting the outflow temperature are investigated, including thermal stratification, flow height above the temperature-control curtain, water level, and discharge flow. The results show the following: firstly, the outflow temperature mainly depends on the thermal stratification, decreases with the increase of water level, and increases with the increase of discharge flow; secondly, the effect of a temperature-control curtain on improving the outflow temperature is directly related to the thermal stratification in different months, and the improvement effect is better in spring and summer; finally, the improvement effect increases with the decrease of flow height above the temperature-control curtain, increases with the increase of water level, and decreases with the increase of discharge flow.

Low-temperature discharged water from thermally-stratified reservoirs in spring and summer will have a negative environmental impact on fish breeding and agricultural irrigation downstream. The temperature-control curtain (TCC) is a selective withdrawal structure that can effectively change the discharged water temperature. Compared with a traditional selective withdrawal project, a TCC project has the advantages of low cost and simple construction and can even be added to operating reservoirs without impacting power generation. Analysis of the load characteristics is the key to the application of TCC engineering. This paper establishes a three-dimensional numerical model simulation and verifies it with physical model experimental results. The crucial parameters affecting the load characteristics of TCC are investigated, including the water blocking rate, area ratio, inclination ratio, inflow velocity, and water temperature stratification ratio. The results show that: (1) This numerical simulation approach can be used to predict the drag coefficient and the load of a TCC; (2) the water blocking rate has the greatest influence on the drag coefficient, and it is the most critical indicator of the TCC load; and (3) the drag coefficient exponentially increases with an increasing water blocking rate, quadratically increases with an increasing area ratio, linearly increases with an increasing inclination ratio, and linearly increases with an increasing water temperature stratification ratio.

In order to investigate the force transmission mechanism of offshore high pile cap foundation under large bending moment loads from wind turbine units and complex marine environmental loads, we use a step-by-step loading method in a numerical model to stimulate the mechanical characteristics of the foundation under different load magnitudes. We obtain the key bearing parts of the high pile cap structure, and analyze the mechanical characteristics of the concrete cap and oblique steel pipe pile. The results show that as the wind turbine loads and environmental loads increase, the bearing mode of the concrete cap shifts from axial compression to bias compression. The contact area between the top of the steel pipe pile and the concrete cap is identified as the critical part for load bearing and transmission, where tensile damage of the concrete first occurs. With increasing loads, the maximum stress of the steel pipe pile shifts from the wave flow load application point to the mud surface. This research clarifies the load transfer law and key parts of the high pile cap foundation, providing guidance for the safety design of foundation structures.