3D Finite Element Analysis For The Temperature And Stress Fields Of The Diversion Type Pressure Tunnel

In the design of hydraulic tunnel,pr essure tunnel is encountered the problem of stress calculation under the interaction of loads of temperature and uniform internal water pressure frequently.Especially in recent years,development of pumped-storage power station and diversion type power st ation,the hole diameter is often larger,complex geological conditions,buried deep,therefore temperature stress calculation problem become more prominent ? Although many domestic and international scholars pay more attention to studying the temperature-stress of mass concrete projects,the tunnel concrete lining of the thin-walled structure temperature stress study is less,also did not get enough attention,and the specification for the present nor the calculation method of concrete temperature stress is presented.However,in practical engineering,we found that many concrete lining temperature cracks appeared.The hydraulic tunnel will raise the total stres s level of lining,especially the joint action of temperature stress and the internal pressure caused by the stack,so the calculation of pressure diversion tunnel of temperature stress should be given attention.This article mainly uses the finite elemen t method to stress analysis for complicated engineering geological conditions,the low level of surrounding rock,the larger diameter of pressure diversion tunnel,and analyzes the influence of temperature stress produced by temperature field to the extrem e value of lining stress during construction and normal operation periods in detail.Firstly,analyzing engineering data to determine the initial conditions and boundary conditions;then using the finite element software ANSYS to calculate the stress distr ibution of lining under the influence of concrete hydration heat and the temperature of hole during the construction and the stress distribution under the influence of different temperature conditions during normal operation;Finally using elastic deflecti on humorous method to calculate the extreme value of temperature stress and obtain relative conclusion by contrasting several groups of working condition.(1)Under the condition of no internal water pressure during construction period,large effect on the overall deformation of temperature stress of concrete lining,temperature stress makes the extreme value of horizontal displacement and vertical displacement of the lining increase accordingly.Considering the internal pressure,temperature stress has little impact on the overall deformation of lining and reduces the horizontal displacement of the lining,increases the vertical displacement of the lining during the normal operating period.(2)Lining stress extreme values are according with the strength of concrete during the construction,normal operating period to increase the internal pressure make the extreme value of pull stress of lining exceed the tensile strength of concrete,so we know that the pressure tunnel with high head fails of tensile strength only with concrete lining,we should draw the corresponding stress extreme value by calculating to determine the type of lining.(3)The temperature field of tunnel generated by the intera ction of concrete heat of hydration and the temperature of hole has great temperature stress which main form is tensile stress on the lining during construction.In normal operating period,after the concrete heat of hydration stabilizes basically,the cha nge in temperature regards as the first condition of temperature stress,water temperature produces radial tensile stress mainly and the tensile stress generated by high temperature is larger than low temperature during the operating period of tunnel.(4)Under the condition of considering the temperature stress,the mutual influence among the lining of internal stress distribution,lining and surrounding rock is extremely complex.The stress value calculated by elastic theory method is larger than finite element method.Because the elastic theory method take insufficient account of the interaction of load and the mutual effect between surrounding rock and the material properties of the lining;the finite element method can comprehensively consider the effect of various factors as much as possible,establish a more practical calculation model,can make up for a lack of corresponding traditional methods,so the finite element method is more suitable for the calculation of diversion type pressure tunnel of l ining under the complicated geological conditions.