Resilience Evaluation of Shallow Circular Tunnels Subjected to Earthquakes Using Fragility Functions

The present work aims to introduce an integrated framework for the resilience evaluation of shallow circular tunnels subjected to earthquakes using fragility and restoration functions. A typical shallow circular tunnel in Shanghai city of China is examined in this work and a corresponding numerical model is established using ABAQUS. Then, a set of ground motions are well chosen to implement large numbers of non-linear numerical analyses so as to determine the lining responses of the tunnel structure with various levels of seismic intensities. According to the above numerical results, fragility functions in terms of the peak ground acceleration (PGA) and peak ground velocity (PGV) at the free-field ground surface are generated, accounting for the main sources of uncertainty, and the direct seismic loss for the examined tunnel is obtained. Moreover, according to the developed fragility functions and the existing empirical tunnel restoration functions, the evolution of the resilience index (Re) with various levels of PGA and PGV for the examined tunnel is derived and quantified. The results indicate that the tunnel resilience will decrease significantly as the earthquake intensity measure (IM), i.e., PGA or PGV herein, increases. The proposed framework is expected to help city managers support adaptations to seismic hazards with the development of preventive or retrofitting measures as part of efforts to provide more resilient metro systems.