Behaviour of coupled tunnel-soil-aboveground building systems in seismic conditions evaluated by means of parametric analyses

In seismic areas, the realization of underground structures requires careful studies of dynamic interaction with the surrounding soil and with the existing aboveground buildings. Up to now, analyses involving at the same time tunnels-soil-aboveground buildings (full-coupled analyses) are still very rare. This paper reports the results of a series of parametric analyses by means of 2D FEM modeling, starting from a real case-history regarding the Catania (Italy) underground network. Different types of soils and different recorded accelerograms have been adopted, in order to investigate their effects on the response of the soil and of the tunnel. Equivalent linear visco-elastic constitutive models have been adopted for the soil, the tunnel and the structure. In order to take into the soil non-linearity, degraded shear moduli (G) and increased soil damping ratios (D) have been evaluated according to EC8 (2003). The models have been investigated in the time and frequency domains.