Seismic vulnerability assessment of an existing tunnel: a case study from CERN

This study presents a fully coupled dynamic analysis of the TT10 tunnel at CERN, a structure built in the 1970s through red molasse and moraine deposits without specific seismic design criteria or structural reinforcement. Although located in a region of moderate seismicity, the tunnel has exhibited visible lining cracks over time, raising concerns about its seismic vulnerability and the need for retrofitting strategies. Finite element simulations were performed using two constitutive models: a linear visco-elastic law and a visco-elastic-ideal plastic law with a Mohr–Coulomb strength criterion. The effect of lining deterioration on seismic performance was investigated through two scenarios involving a reduction in stiffness. The seismic input was derived from the Gilroy 2 earthquake record scaled to 0.15g to reflect local site conditions. The numerical study provides useful insights for the analysis of existing tunnels affected by lining degradation, enabling the investigation of different scenarios given the limited knowledge of the tunnel lining properties.