Fragility assessment of shallow buried tunnels under explosive hazards

The surge in terrorist attacks and regional conflicts in recent years underscores the compelling necessity to acknowledge the potential threat of bomb attacks on subway tunnels. Consequently, a meticulous assessment of the fragility of subway tunnels in the context of a bombing disaster becomes imperative. In pursuit of this objective, this study endeavors to introduce a comprehensive fragility assessment framework designed to evaluate the probability of damage to subway tunnels in the face of explosion hazards. First, we quantify the uncertainty in bomb explosion positions across three distinct guidance accuracies: Laser-guided, GPS-guided, and INS-guided. This quantitative analysis uses the rigorous Latin Hypercube Sampling ( LHS ) method. Subsequently, a sophisticated three-dimensional finite element model is formulated, considering the interaction between shockwaves and tunnel structure. Following this, a fragility function for tunnel explosions is meticulously developed, forming a logarithmic regression model that establishes a robust relationship between explosion intensity measures ( IM ) and tunnel damage measures ( DM ). Finally, this study employs tunnel explosion fragility functions to precisely quantify the probability of tunnel damage across various states of destruction. Additionally, a comprehensive analysis is conducted to discern the specific influence of distinct bomb guidance accuracies and weight of TNT ( WTNT ) on tunnel fragility. This research enhances the design and management of tunnels and underground transportation networks by incorporating an in-depth understanding of explosion risk.