A numerical case study on the long-term seismic assessment of reinforced concrete tunnels in corrosive environments

Abstract

The paper investigates the long-term seismic behaviour of an underground reinforced concrete (RC) metro tunnel in Santiago, Chile, considering the combined effects of chloride-induced corrosion and cumulative, low-amplitude seismic shaking on the structure's performance. The soil-tunnel response is evaluated with the aid of transient, nonlinear finite element analysis using a two-dimensional (2D) plane strain numerical model that adopts advanced nonlinear models for the simulation of soil and concrete plasticity and the dynamic stiffness behaviour. The effects of corrosion deterioration are demonstrated in terms of time-dependent loss of rebar area and cover concrete stiffness and strength. The study illustrates the influence of ageing and repeated seismic shaking on lining deformation, crack development, and the modal characteristics of the intact and degrading systems. The results indicate that multiple low-amplitude events drive the non-degrading RC tunnel beyond its elastic regime without significant structural response consequences. A noticeable impact of corrosion deterioration on the structure's seismic performance is revealed, increasing with the number and intensity of earthquake events. Two different tunnel embedment depths are comparatively assessed. The analyses demonstrate larger co-seismic section convergence in the case of the deeper tunnel, yet a less pronounced effect of ageing and successive seismic loading compared to the shallow section, which is evident in the RC lining cracks at the end of shaking.

Keywords

• Tunnels
• Reinforcement corrosion
• Ageing
• Earthquakes
• Numerical modelling
• Long-term performance