Numeric Analysis Of Seismic Response Of Underground Tunnel

With the underground structures been widely used, more and more attention have been paid to the aseismic design and safety evaluation of these structures.In this paper, the typical incidents of tunnels during earthquake and the recent research development on this subject are briefly described, and the behavior of tunnel during earthquake is summarized. Based on soil-structure dynamic interaction theory, the application of dynamic FEM for underground tunnel, the simulation of earthquake excitation, and the selection of boundary condition are investigated. The coupling method of finite element and infinite element has become an effective method for dealing with dynamic responses with infinite field boundary. By applying this method, the influence of the size of finite element field and the position of middle node of infinite element in the coupling model are studied in this paper.A planar coupling model of finite element and infinite element is first built to analyze the seismic response of an underground tunnel on the basis of the proposed theory and method. Then, tunnels with different lining materials are considered and seismic responses of the tunnels under single-dimensional and multi-dimensional earthquake excitations are simulated and compared. Finally, A three-dimensional coupling model of finite element and infinite element is built to analyze a underground tunnel which has inequable transectsSome conclusions are given as follows: (1) The size of finite element field should be 3 times of the core region when using the planar coupling model of finite element and infinite element, while the position of middle node of infinite element equal to the finite element field. (2)The buried structure vibrates in consistent with the surrounding ground and its existence enlarge the amplitude of the ground near by.(3)For the underground tunnel , the inner force of wall is affected by the level earthquake mainly, and the top and bottom plates is affected by the vertical earthquake mainly. (4) The seismic response of underground tunnel is not affected by the lining material. (5) The relative displacement between top plate and bottom plate is influenced little by the span of the tunnel. The stress distribution of the side-wall is affected by its shape.