Analysis on the disaster chain evolution from gas leak to explosion in urban utility tunnels

Gas leakage and explosion are the main disasters associated with utility tunnels. The ongoing challenge is to establish a precise and efficient disaster chain model to describe the process from the gas leakage to explosion in the utility tunnel, which are regarded as the initial and final status during the disaster, respectively. In this paper, a disaster chain model is proposed to analyze the evolution process from gas leak to explosion in a concurrent way. The risk area of the gas ex-plosion, which could change with gas leakage dynamically, was calculated by the proposed model. The evolution analyses of the gas leakage and explosion were systematically studied. Results showed that the CH4 mass fraction was stratified and focused on the top of the utility tunnel during gas leakage, which provides initial conditions for the gas explosion. The explosion reaction considering the gas cloud location and stratification effect is insufficient and unstable since the gas concentration is out of the optimal explosion concentration. Additionally, the propagation velocity and temperature were decreased since the explosion intensity was weakened.