Research On Analysis Of The Bottom Outlet In High-Head Thin Arch Dam By Finite Element Method

With the market economy developing in china, the demand for energy sources is gradually increasing and many hydropower projects are developing rapidly. Some huge hydropower stations with the characteristics of higher dam and larger reservoir will be built in recent. The capability of generator unit and water turbine has become more and more greatter. Those drainage holes are usually high dams with big holes, high water head and large flood discharge. Orifices in dam body weaken the integrity of structure. For the arch dam has mass flood discharge, opening large orifice for flood discharge has great advantage. But the complex structures, which the thinner structure of dam body, adding the large upstream and downstream cantilevers of orifice and different aspect ratio of intakes and outlets for satisfying hydrodynamic requirement, make the force distribution complex. So the discussion has improved a new schedule for the structure security problem of discharge holes.At first, the finite element submodel method in this paper carried out the verification analysis. The results show that analysis of opening stress with submodel method not only meets calculation accuracy, but also greatly reduces calculation work, saves time and computer memory. So this is the effective method to analyze opening stress. For acquiring the more accurate results of stress near orifices, on the basis of the submodel method, this paper first does the analysis of integral mesh with local mesh encryption, and then removes the orifice part to fine encryption. Furthermore, the precise displacement value from the whole model is applied to the boundary of the submodel, which can obtain more precise result. The paper using this method to calculate the bottom outlet in high-head thin arch dam, analyze opening stress of the pressure section of the bottom outlet and stress state of structure of upstream and downstream cantilevers. The results show that the tensile stress of flow direction of bottom outlet sidewall at the intersection of upstream cantilevers and dam body is large. But traditional plan finite element method thinks that this tensile stress is small when calculating the stress near orifices. This paper finds out the reasons through analysis of multi schemes. According to the results, cantilevers have a great effect on the tensile stress of flow direction of bottom outlet sidewall at the intersection of upstream cantilevers and dam body. Because of the existence of cantilevers, this part tensile stress is increase.In contrst to traditional method, submodeling method can gain more accurate numerical value for the concerning region of model, enhance calculation accuracy, make it possible to compute huge complex hydraulic structure model. This is an effective method to solve huge complex problem.