The baffle-drop shaft structure is usually applied in deep tunnel drainage systems to transfer shallow storm water to underground tunnels. At present, the definition of the maximum operational capacity of baffle-drop shafts is lack of scientific and reasonable analysis, and the researches on hydraulic and energy dissipation characteristics have been insufficient. In this paper, a 1:25 scale hydraulic model test was conducted to observe the flow phenomena during the discharge process, analyze the relationship between the maximum inflow discharge and the baffle parameters, and calculate the energy dissipation rate of the shaft under different flow conditions. The results demonstrated that three kinds of flow regimes were presented in the discharge process: wall-impact confined flow, critical flow, and free-drop flow. The impact wave majorly brought about the energy dissipation of water on the baffle. The impingement and breakup of the inflow at the bottom of the drop shaft, as well as the reverse flow, resulted in the final energy loss. The time-averaged pressure value of the upper baffle was 1.5–3 times that of the central and lower baffles. The baffle with a design angle could effectively reduce the time-averaged pressure of the water flow acting on the baffle. The energy dissipation rate of the drop shaft decreased with the increase in the inflow discharge, and the energy dissipation rate was found to range from about 63.14% to 96.40%. The optimal size of the baffle-drop shaft with the maximum energy dissipation rate was d/B = 0.485 and θ = 10° (d, B, and θ are the baffle spacing, width, and angle, respectively).
The geyser phenomenon seriously threatens the safe operation of deep tunnel drainage systems and drop shaft structural safety. To simulate the geyser process in a baffle-drop shaft, a 1:50 scale model test system was used to research the response relationship between the geyser mechanism and test parameters such as water depth, inlet pressure, and inlet volume. The results show that the pressure in a baffle-drop shaft fluctuates sharply during the geyser process. This is caused by the release of a high-pressure air mass, and high-speed movement of the air–water mixture causes a local pressure imbalance in the drop shaft. A prediction formula for the maximum geyser height of a baffle-drop shaft was established by a multiple linear regression model. Geyser occurrence conditions for the baffle-drop shaft were proposed combined with the response relationship between different influence variables and geyser intensity. Except for the inlet pressure, submerged state of the baffles, and measured location, the hydrodynamic load on the bottom of the baffles is also related to the randomness of the air–water mixture jetted on the baffle bottom. The maximum hydrodynamic load on the baffle bottom during the geyser is 10 times the hydrodynamic load on the baffle surface under normal discharge conditions. This research provides a theoretical reference for the structural design and safe operation of baffle-drop shafts.
The possibility of servicing lifelines such as highways, railways, pipelines, and tunnels is of great social importance. The characteristic that separates the buried pipeline from other structures is that its dimensions are very long compared to its other dimensions. Ground vibrations caused by earthquakes, construction activities, traffic, explosions, and machinery can damage these structures. Lifeline integrity can be compromised in two ways: (1) direct damage due to excessive dynamic loading of the lifeline, and (2) indirect damage due to soil failures such as liquefaction, slope instability, and differential settlements. 3D printing (also known as additive manufacturing) is an advanced manufacturing process that can automatically produce complex geometric shapes from a 3D computer-aided design model without tools, molds, or fixtures. This automated manufacturing process has been applied in diverse industries today because it can revolutionize the construction industry with expected benefits. This research study on the performance of buried pipelines under static loads to the structure's safety against the possible development of progressive failure. This research study includes a numerical study, where it was studied many parameters to value the performance of the pipeline. The parameters are (a) the material of the pipeline (steel, traditional concrete, and 3D concrete printed), (b) the thickness of the pipeline (20, 30, and 40 mm), and (c) soil type (moist sandy soil, saturated sandy soil, moist cohesive soil, and saturated cohesive soil). Different results were obtained depending on the type of soil where all pipelines materials' behavior was similar in the case of moist soil. Doi: 10.28991/CEJ-2022-08-01-01 Full Text: PDF
The flow field distribution around the suspended pipeline is closely related to the mechanical characteristics and local scour characteristics of the underwater crossing pipelines. To fully investigate the velocity distribution and wake structure characteristics around the suspended pipeline under oblique flows, a flume model test and a numerical simulation based on the LES (Large Eddy Simulation) method were performed. The results showed that the velocity distribution near the suspended pipeline under oblique flows had obvious three-dimensional characteristics. The influence range of pipeline on velocity is 1 d before to 6 d behind the pipeline (d is pipeline diameter). The smaller the flow angle, the more disordered the velocity distribution is. The larger the flow angle, the greater the variation degree of the velocity at each section at the same section is, as well as the higher the velocity deficit value is. In addition, the larger the angle of pipe flow, the more violent the wake structure changes with the flow velocity, and the stronger the regularity of vortex street shedding. This research provides a theoretical reference for the scour prevention design and safe operation of crossing pipelines.
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