Three-Dimensional Numerical Simulation Method And Its Application To Seismic Response Of Large Shield Tunnel

Economic development is inseparable from transport. With China's rapid economic development, a large number of constructions of tunnels and other underground structures have become an important mean to solve our traffic problems.To ensure their seismic safety has important social and economic significance. Currently, the seismic research of underground structures has become an important issue in the international. There have been many numerical simulation studies on the seismic response of underground structures, how to truly reflect the dynamic response of large shield tunnel under seismic excitation, and to improve accuracy of numerical simulation and computational efficiency has got more and more attention.In this paper, a numerical simulation method for simulating dynamic response of large shield tunnel is proposed. The three-dimensional finite element model of Shanghai Yangtze River Tunnel and its surrounding soil is created. And the complex dynamic response of large tunnel structure under different seismic excitation is simulated by Dawning 5000A high-performance computing platform. Finally, the seismic performance of the tunnel structure is analyzed, and a reference for the seismic design of tunnel structure is provided. The main study includes:The basic numerical simulation theory and method of the dynamic response of large shield tunnel is studied. Because of the large number of all elements, the explicit integration algorithm is used in the calculation process, which does not require iterative solution. The creation of dynamic contact model can reflect contact and sliding of contact surfaces better, than the coordination of nodal displacement and deformation. For the solutuion of large and complex engineering problem, parallel computing technology has become a necessity. Through using domain decomposition method, the size of large engineering problem can be reduced, and parallel computing can be realized.The modeling method of Shanghai Yangtze River Tunnel and its surrounding soil is studied. The full-size three-dimensional finite element model of Yangtze River Tunnel is created, which can reduce the error caused by simplification of structure.Taking into account the different dynamic properties of different layers, soil model is stratified based on the relevant information. To ensure the effective cooperation of tunnel and soil is very important. The contact is realized by creating three-dimensional dynamic contact model. The overall number of the final model elements is large, so it is simulated by using parallel computing method. Whether parallel computing can improve computational efficiency is also studied.The response of tunnel structure under initial condition is studied. Through loading gravity step by step, the tunnel excavation process is simulated and the initial soil stress is obtained. And finally, import the initial stress and hydrostatic pressure of the tunnel surface into the initial finite element model. By numerical simulation, the deformation and stress of control sections-including common sections and connection channels-under initial conditions is studied. The dangerous position and dangerous section which can lead to damage to tunnel are analyzed. And which is also a basis for the study of seismic response if taking into account gravity.The dynamic response of tunnel under seismic conditions is studied. Through loading the acceleration time-history curves of bedrock in the bottom of the overall model, the dynamic response of Yangtze River Tunnel under the horizontal and vertical seismic excitation is simulated. For reducing the impact of the finite domain boundary conditions, the viscoelastic artificial boundary is added around overall model. And damping is also considered in the structural dynamic analysis. By numerical simulation, the deformation and stress of the control sections under seismic excitation is studied. The dangerous position, section and condition are also analyzed, which provides a useful reference for the seismic design and analysis of tunnel or other underground structures.The seismic response of the tunnel structure considering the initial condition is studied. Through loading step by step, the effect of gravity for seismic response is considered for the first time, which makes the numerical simulation result closer to the actual response of the tunnel. The basic method is as follows. Firstly, import the initial state of soil and tunnel under gravity into calculation file, and then load gravity and seismic excitation for the overall simulation model. By numerical simulation, better simulation result is obtained through this method, and the deformation and stress of control sections under seismic excitation when considering the gravity is studied.