Research On The Influence Of Silt Sediment On The Hydraulic Automatic Flap Gate

Hydraulic automatic flap gates are economic, automatic and manageable, which structures are simple. They can open and close steady. The silt sediment in front of hydraulic automatic flap gates can easily flow through them. Hydraulic automatic flap gates are widely used in all kinds of small water conservancy projects. Especially in low-head gate dams in the mountains which are fast-flowing and unmanageable, they have a wide application foreground.Sediment accumulation is one of the main problems in sandy rivers in the mountains.Researching on the influence of silt sediment on the hydraulic automatic flap gate will perfect the theory of the flap gate and improve the hydrodynamic structure. In order to provide the basis for its design, the influence of silt sediment on the hydraulic automatic flap gate is studied by model test and numerical simulation, which object is a flap gate with connecting levers and rolling wheels. The main conclusions are as follows:(1) The shortage of the existing research results which is lack of the study of sedimentation was pointed out, by analyzing the research results of the flap gate at home and abroad.(2) In order to estimate the effect of silt sediment on the water level of a hydraulic automatic flap gate with silt sediments in front of the gate, the horizontal pressure, vertical pressure and adhesion of silt were taken into account. A calculation formula of water level was deduced by analyzing its forces balance before the flap gate opened.(3) In order to study the effect of silt sediment on the opening process of the hydraulic automatic flap gate, the water levels and the gate angles under different heights of silt had been measured by calculating and model test. The results show that the influence of silt sediment on the opening process of the hydraulic automatic flap gate is not obvious. The upstream water level increases with the increasing of the silt height. The calculated values of the upstream water level with silt sediment in front of the gate increased by 0.3%~0.3%. The increase accounts for 10.5%~62.3% of the level above the gate. The mesured values of the upstream water level with silt sediment in front of the gate increased by 1.4%~5.6%. The increase accounts for 19.9%~48.3% of the level above the gate. The measured results were compared with the calculation ones, which relative error was 2.9%~4.0%. It was shown that the calculation formula is reliable when it is used to calculate the water level of the test model with silt in front of it. In addition, a fitting formula of water level was developed for the sakeof simple calculation.(4) In order to study the effect of silt sediment and the rise of opening water level on the structure of the hydraulic automatic flap gate, the stress and deformation of the flap gate had been simulated by ANSYS. The results show that the maximum and the average value of the equivalent stress, the major principal stress and the deformation increase with the increasing of silt height and the opening water level.The maximum equivalent stress of condition 2 and 3increased by 5% and 11.8%, compared with the condition 1. The maximum major principal stress of condition 2 and 3 increased by 3.0% and 5.8%, compared with the condition 1. The maximum deformation of condition 2 and 3 increased by 3.6% and 7.0%, compared with the condition 1.(5) Combining with the results of the paper, some suggestions were put forward on the study of silt sedimentation in front of the flap gate.