Research on the Explosion Venting Effect and Influencing Factors of Gas Explosion in Urban Shallow Pipe Trenches

In this study, two groups of gas explosion venting tests were conducted based on a large-scale pipe trench test system (30 m length), and the numerical model of pipe trench was established through the FLACS software, which was verified by the corresponding experimental data, and then the explosion process and load distribution characteristics of the gas explosion in pipe trenches were further analyzed by varying the number, location, and size of the top vent and the size of the end opening. The results showed that the explosion flame and overpressure time-history oscillate significantly without top vents, and the peak impulse decreases while the peak pressure first increases and then decreases axially along the pipe trench, mainly attributed to the relative positions of the precursor and flame wave. The top vents can significantly block the flame propagation and weaken the oscillation phenomenon, but the attenuation of the peak overpressure is mainly limited to the upstream of the vents, so it is necessary to set multiple consecutive top vents to effectively reduce the overall explosive load. The overall peak stress and peak impulse can be attenuated by 12% and 57% respectively with 3 top vents, but the downstream peak stress even tends to increase with only one top vent. In addition, the explosion venting effect of top vents can be ignored with the small size (0.2 m x 0.2 m), the explosion venting effect of the end opening is also limited to a small range (12 m) upstream of it.