Dynamic Analysis Of Gas Leakage And Explosion Process In Urban Utility Tunnel

With the development of urbanization,Urban Utility Tunnels have been widely developed and applied in China.Among all kinds of municipal pipelines,the gas pipeline is extremely controversial due to its inherent risks of the fire and explosion accident.However,the mechanism of gas disaster is unknown on account of the lack of theory and experience in the application of utility tunnel.This study takes the gas disaster chain as the research route and carries out the corresponding research including the analysis of gas leakage law,explosion evolution process and response mechanism of the explosion.The details are as follows:1)The research work of gas leakage law is carried out by the Computational Fluid Dynamics method(CFD)and the Gas Explosion Risk Coefficient model is established based on the Gas Explosion Limit theory.Under the no ventilation condition,the results show that the gas mass in the tunnel is distributed in a strip pattern along the roof of the cabin,and the methane concentration decreases modestly from the top to the bottom along the height.When ventilation conditions are regarded,the suggestion for gas accident prevention is taking the internal pressure and leakage hole size into account while making the ventilation strategy.Besides,the gas concentration and the detonation risk coefficient are mapped by the risk coefficient model for the audio-visual reflection of the evolution process of explosive hazardous area.2)Adjusting the spatial characteristics of tunnel and the accumulation law of gas mass,the evolution process of the gas explosion is investigated.The results show that the explosion process of gas is controlled by either chemical reaction or turbulent effect,but the latter plays a leading role.The internal obstacles of cabin have significant turbulent acceleration effect on explosion process.In addition,through the dimensional analysis and CFD calculation,the gas explosion peak pressure calculation model is fitted for explosive consequence prediction.3)The numerical model with soil,tunnel,air and mixed air parts is established by FluidStructure Interaction method(FSI)and the influence mechanism of mixed gas volume,shape and gathering location on structural dynamic response is discussed.According to the results of numerical calculation,when the gas concentration is constant,the volume of mixed gas has a positive correlation with the amplitude of explosion pressure;the cross area of cabin and gas explosion intensity are negative correlated within a certain range.There is a cyclic process in the explosion sphere when the explosion is concentrated on the top of the cabin.The asymmetric load distribution leads to greater stress amplitude in the corner area of the partition wall.Combined with the above results,a series of anti-explosion design suggestions are put forward for the construction of utility tunnels.