Thermodynamic and Mechanical Analysis of Gas Explosions in Underground Vaults

An explosion in an underground vault can pose a significant safety problem. The ignition of a combustible gas mixture in a rigid vault can generate pressures that can cause damage and failure to the structure of the vault, including the manhole cover. If combustion of the gas within the vault releases sufficient energy, the manhole cover can be ejected, creating a safety hazard. This article describes a thermodynamic and mechanical analysis of the explosion process in an underground vault. The mathematical model is formulated into a computer program that can be used as a first-step design tool to modify the existing vault designs so that the explosion hazards can be minimized. The computer model predicts the temperature and pressure rise that results from a gaseous explosion within the vault. The pressure rise calculations are then used to predict the motion of the manhole cover if it is ejected from its normal position. The results of the model can be used to improve the design of the vault and its cover to minimize property damage and personal injury should such an explosion occur.