ABSTRACTThe evaluation of the seismic behaviour of underground structures represents one of the most actual seismic geotechnical and structural engineering research topics about the study of the complex phenomena of soil-structural interaction. In the last decades, different types of simplified and numerical approaches have been developed for the correct analysis of the seismic vulnerability of these important infrastructures and a series of laboratory tests for the seismic behaviour characterization of the soils (resonant column test, etc.) and of the coupled soil-structure system (centrifuge test, etc.) have been conducted, especially after the recent strong earthquakes where the underground structures have been subjected to significant damages. In the same way, in the last few years, the International Codes are beginning to pay attention to the concepts of the seismic design of these structures.Despite the significant development of knowledge, described above, still remain open several uncertainties of the correct reproduction of the underground structures behaviour under seismic load. In this paper, the evaluation of the seismic behaviour of Mercato Santa Anida metro station was conducted through the application of two different seismic input, considering the soil-structure interaction effects. The results of the nonlinear Time History analysis are analysed in terms of bending moment acting on the concrete retaining walls of two different significant sections of the metro station.KeywordsUnderground structures; Soil-structure interaction; Finite element analysis; Earthquake; Seismic vulnerability. INTRODUCTIONUnderground structures can be grouped into three broad categories , each having distinct design features and construction methods: bored or mined tunnels, cut and cover tunnels and immersed tube tunnels (Figure 1).Unlike surface constructions, underground structures were considered, for a long period, practically invulnerable to earthquakes. This consideration about underground structures safety, however, has been changed after some of them suffered serious damages caused by earthquakes, including the 1995 Kobe (Japan), the 1999 Chi-Chi (Taiwan) and the 1999 Kocaeli (Turkey) earthquakes .Damaging effects of earthquakes on underground structures can be classified into two main groups:damages caused by vibratory motion (shaking) of the ground;damages due to ground failures.This study has the purpose of determining the most important aspects of the soil-structure interaction effects on underground structures subjected to seismic loads, taking as case study the new Lima Metro line 2 project.