Nonlinear Finite Element Analysis And Reinforcement Measures Of Steel Bifurcation Embedded In Rock

Steel penstocks embedded in rock are being widely used in middle and large-scale hydroelectric projects, whose scales are getting larger and larger. The value of HD exceeds the value set by the Code, and the method suggested by the Code can not embody the real load bearing capability of the materials under the internal water pressure. So it can not meet the need of construction of modern hydroelectric projects.Embedded bifurcation is generally regarded as exposed bifurcation in engineering design for its complex structure. However, this method doesn't reflect on the interaction of steel bifurcation and surrounding rock. Therefore, their real stress can't be rightly judged, and the influence of surrounding rock bearing capacity. In addition, the very complex structure cause stress to high converge, and the large stress exceed the criterion of material.With increasing development of computer science and continuous perfection of the finite element theory, many kinds of excellent universal analysis software are more and more widely used in engineering design and analysis, and even have been valid tools in solving complicated engineering problem.In this paper, with the help of ANSYS and FLAC software, several schemes are carded out for embedded bifurcation in one large-scale hydroelectric projects. In order to reflect the loads-bearing characteristic of the structure as accurate as possible, the author take into account for the elastic and plastic behavior of filled concrete and surrounding rock, consider the effects of initial geostress and secondary geostress caused by excavation and supports, and the bending and shear effects of steel lining subject to internal water pressure. Different element types and material forms are chosen according to steel shell, concrete and rock.To reinforce the bifurcation, the author gives three schemes: thickenning steel,using the steel lined-reinforced concrete,pre-stress anchor pile, and analyze mechanics behaviors of three schemes separately. To thicken steel or use the steel lined-reinforced concrete can meet the need of reinforcing the bifurcation, but the two schemes have shortcomings as well, because they will cost more money and time.The author analyze the sensibility of three schemes to optimize crucial parameters, then get some useful conclusions for the project design.