Abstract: This study is to explore the applicability of the response displacement method to the seismic analysis of underground utility tunnels as well as the determination and modeling of foundation spring stiffness. SAP2000 software for finite element structural analysis was adopted to analyze the seismic response of underground structures and probe into the influence of different calculation methods of modulus of subgrade reaction and shear stress of soil on the seismic response of structures. The results were compared with those derived from dynamic time-history analysis in PLAXIS. According to the research, the response displacement method is clearly preferable in the preliminary seismic calculation of underground utility tunnels. In the calculation of foundation spring stiffness, the Japanese empirical formula and the conventional static finite element methods are advisable; meanwhile, the layering of soil should be considered as much as possible, because the obsessive equivalent linearization may result in a larger shear modulus of soil, and the deviation of the internal force of the structure can reach -400%—-250% compared with the results of the dynamic time history method. When applying foundation springs to the seismic response calculation model, it is recommended that two-node compression-only gap elements in SAP2000 be adopted to simulate normal foundation springs by combining distally fixed hinge supports, and the conventional soil spring elements be adopted to simulate tangential foundation elements.

Key words: earthquake engineering, underground utility tunnel, seismic analysis, seismic response, response deformation method