The Method Of Equivalent Modeling Of Shield Tunnel And Its Researth Of The Seismic Response

With China's rapid economic development and rapid population growth, ground transportation can not meet the need of economic development and the residents. So tunnels and other underground construction have become an inevitable choice to solve our traffic problems.But China lies two major seismic zones in the world --circum-Pacific seismic belt and seismic zone between Europe and Asia by the Pacific Plate, Indian Plate and the Philippine Sea plate extrusion, earthquake fault zones are well developed. Since the 20th century, China had occurred nearly 800 times of 6 and above level earthquakes, all provinces except Guizhou, Zhejiang and other provinces and Hong Kong.So underground construction seismic research has become an important issue.This paper relies on the project commissioned by Shanghai Tunnel Engineering Rail Transit Design and Research Institute, "Three-dimensional simulation of large shield tunneling and seismic analysis." Large shield tunneling method of numerical simulation of dynamic response of the earthquake is presented in this paper.The three-dimensional finite element models of the Shanghai Yangtze River Tunnel, working wells and the soil are created in this paper. And the dynamic response of the tunnel structure is studied in the initial condition, uniform excitation and non- uniform excitation. The displacement, deformation and stress of the key section of the tunnel structure are researched in the above conditions, which makes a comprehensive evaluation of the tunnel structure and provides technical support of the seismic design for the tunnel. The main study includes:The method of the dynamic response of large shield tunnel is studied. In this paper, the method of the dynamic finite element numerical is used to solve the seismic dynamic response of the shield tunnel. In order to solve the equations of motion more effectively, the central difference method is used. The central difference method is significant in nonlinear analysis, because the stiffness matrix of each incremental step is modified in non-linear analysis and the matrix inversion operation is avoided.The benefit of the calculation is obvious.The modeling method of the assembly tunnel model and equivalent model is studyed. And groups of experiments to determine the stiffness reduction coefficient of the equivalent model is setted. In order to replace the equivalent model of this assembly model, the modified routine method is used to design horizontal and vertical equivalent tests, horizontal and vertical stiffness reduction coefficient of the equivalent model is calculated. By determining a reasonable stiffness reduction coefficient, the equivalent model can replace complex assembly model. Modeling is simplifed and the computation time is reduced.The dynamic response of West Yangtze River Tunnel in the initial conditions is studyed. First, in this paper, the West Yangtze River Road tunnel and surrounding soil modeling is studyed.And in order to better simulate tunnel excavation process, step-loading method is used. So the initial stress of the soil under the gravity is achieved, then the initial stress of the soil and the water pressure is imported into the soil-tunnel coupled finite element model. Boundary condition is setted and the tunnel deformation and stress of the tunnel is calculated in the initial conditions.The tunnel dynamic response of the uniform earthquake excitation in the initial condition is studyed. The impact of the gravity field is taken into account in this condition.In order to reduce the impact of the finite domain boundary conditions, viscoelastic artificial boundary of the overall model is added in this paper.And the damping in the structural dynamic analysis is considered. The displacement, deformation and stress of the key section of the tunnel structure are researched in the condition, which makes a comprehensive evaluation of the tunnel structure and provides technical support of the seismic design for the tunnel.The tunnel dynamic response of the non-uniform earthquake excitation in the initial condition is studyed. Traveling wave method is used to load the non-uniform seismic excitation. Traveling-wave method can consider the phase change of all points. For rock foundation built on more evenly on a large-span structure, the traveling wave method is simple and realistic. Compared to the uniform excitation input method, traveling wave method is more realistic and the results are more realistic.