Numerical Simulation Of Leakage And Explosion Of Gas Pipeline And Damage To Adjacent Pipeline In Tunnel

Due to the complexity of China's topography,oil and gas pipelines are increasingly laid parallel in the tunnel.And the gas pipeline in the tunnel has the possibility of leakage that could lead to the explosion,which brings threat to the adjacent pipeline.Therefore,it is necessary to study the leakage and diffusion regular of gas pipeline,the impact effect of explosion after the leakage and the damage of the adjacent pipeline in the tunnel.In this paper,the parallel pipelines are taking as the object of the research.Through the research on the diffusion mechanism of gas leakage,the pore leakage model of critical flow is selected as the calculation model of leakage rate of gas pipeline.In addition,by analyzing the formation and characteristics of explosion shock wave,the phenomenon that the shock waves encountered in the inner wall of the tunnel and the wall of the pipeline and other obstacles is emphatically studied.Aiming at the actual situation of the explosion caused by the leakage of the gas pipeline in the tunnel,the explosion caused by chemical reaction is mainly studied,and the TNT equivalent method is applied to estimate the consequences of the explosion caused by the leakage of gas pipeline.FLUENT software is used to simulate the diffusion of the gas pipeline's leakage in the tunnel.After verifying grid independence and proving validation by empirical formulas,the methane concentration distribution of gas pipeline leakage in the tunnel is analyzed.What's more,the effect of diffusion after the leakage on the leakage aperture,the orientation of the leakage and the pressure of gas transmission is studied.In FLUENT software,the UDF program is loaded to calculate the volume and growth rate of explosive gas of each factor at different leakage time.The results show that,compared to the leak orientation and the gas pressure,diameter of leakage hole is the main factor affecting the volume of explosive gas.The multi-material coupling model of surrounding rock,lining,pipeline,air and explosives is established by ANSYS/LS-DYNA software,and the rationality of the model is verified by empirical formula.In the tunnel,the incident,reflecting and flowing phenomena occur.And the shock wave is supplemented to some extent and is dissipated by the air.The closer the source,the greater the dynamic parameter value of the adjacent pipeline,and the most obvious dynamic response of the point of attack.In the analysis of the influence factors of the explosion load of the adjacent pipeline,the equivalent stress of the adjacent pipeline is positively correlated with the leakage aperture and the pressure in the adjacent pipeline,and is negatively correlated with the detonating distance and the wall thickness of the adjacent pipeline.Moreover,the peak vibration velocity of the adjacent pipeline is positively correlated with the leakage aperture,and is negatively correlated with the detonating distance and the wall thickness of the adjacent pipeline,which is almost irrelevant to the pressure in the adjacent pipeline.In addition,the dynamic response of the adjacent pipeline remains unchanged when the distance between the piers and the attack point is 3m-5m.In the analysis of the stress sensitivity of the adjacent pipeline,the sorting of importance of the influencing factors is:the detonating distance,the wall thickness of the adjacent pipe,the diameter of leakage pore and the inner pressure of the adjacent pipe.In the sensitivity analysis of the deformation of the adjacent pipe,the sorting of importance of the influencing factors is:detonation distance,leakage aperture,the inner pressure of the adjacent pipe and the wall thickness of the adjacent pipe.Based on the failure criterion of stress and strain,the damage condition of the adjacent pipeline in different cases are analyzed.Finally,the example is selected,of which the oil and gas pipelines laying in parallel in the Yan Ying tunnel,and the limit parameter value of the adjacent pipeline is studied with 30mm leakage aperture.The results show that the adjacent pipeline is in a safe state in the design of wall thickness and operat:ing pressure.When the distance between the pier and the point of attack is 2.76m-7.24m,and the distance between the center of the explosive and the pipe is reduced to 1.91m,the adjacent pipeline is in the limit state of starting damage.In this paper,the results of the study make the leakage of gas pipeline and the resulting explosion be closely linked in the tunnel,which not only analyze the law of leakage and explosion of the gas pipeline,but also improve the judgment method of the pipeline's damage in the confined space of tunnel.Therefore,the theoretical support is provided for the safety operation and maintance and the steady development of the parallel oil and gas pipelines in the tunnel.