In the Tokyo metropolitan area, long tunnels are being constructed to make a ring road network. These long tunnels need a ramp tunnel which connects the main tunnel located deep underground to ground level. However, ramp tunnels have a complicated structure and their seismic behavior cannot accurately be evaluated by 2D analysis, therefore a precise examination by 3D analysis is required. In the present study we make a detailed model of the soil-structure system of the ramp tunnel and conduct large-scale numerical computation for the 3D seismic response analysis using a dynamic elastic FEM. The major findings are as follows: i) deformation of the ramp tunnel is not accurately estimated by the standard 2D analysis; ii) the seismic response of the main tunnel is small in a hard soil layer and can be evaluated by the standard 2D analysis; and iii) the 3D seismic response of the ramp tunnel significantly changes depending on the characteristics of the input earthquake ground motion.
underground structure large-scale computation FEM seismic response analysis
H. Dobashi T. Hatsuku T. Ichimura M. Hori T. Yamada N. Ohbo M. Moriguchi H. Itami
Construction Management Division, Metropolitan Expressway Co., Ltd., Tokyo, Japan Tokyo Construction Bureau, Metropolitan Expressway Co., Ltd., Tokyo, Japan Department of Civil and Environmental Engineering, Tokyo Institute of Technology, Tokyo, Japan Earthquake Research Institute, University of Tokyo, Tokyo, Japan Chief Senior Research Engineer , Kajima Technical Research Institute, Kajima Corp., Tokyo, Japan Construction Office, Tokyo Construction Branch, Kajima Corp., Tokyo, Japan