Seismic Fragility Analysis of Shallow Tunnels

With rapid pace urbanization, the shortage of above-ground space has necessitated the development of underground tunnels, particularly for transportation and storage in the form of roadway tunnels, railway tunnels, storage of petroleum products, defense ammunition, etc. However, seismic vulnerability remains a key concern for these subterranean structures. The present study attempts to investigate the impact of earthquakes on a section of the tunnel of the Delhi Metro Rail Corporation, New Delhi, India. The analysis focuses on critical parameters such as maximum forces in the reinforced concrete liner, displacements, induced acceleration, and stress distribution of the soil-tunnel system. A comparative study was performed using existing closed-form solutions to verify the results of the current finite element analysis. Following this, a parametric analysis was carried out to investigate the impacts of overburden depth, the interface between the soil and the tunnel liner, the thickness of reinforced concrete liners, and peak ground acceleration (PGA). Subsequently, seismic fragility analysis of the tunnel model have been performed. The results of the present study is expected to provide deeper insights into its seismic performance and structural resilience that may be helpful for tunnel design.