Research on the influence of high-altitude tunnel environment on gas explosion characteristics and explosion limits

Abstract

Gas explosions in tunnels often result in significant casualties and economic losses. As gas tunnels are increasingly being constructed in high-altitude areas, safety concerns are becoming more critical. The environmental parameters in high-altitude regions, such as temperature, oxygen content, and air pressure, differ significantly from those in low-altitude areas. These differences greatly affect the environment, gas explosion characteristics, and explosion limits in tunnels, yet relevant research is limited. This paper presents findings from measurements and theoretical analysis. The results are as follows: (1) The equations for estimating atmospheric pressure and oxygen content were derived through measurement, achieving a high degree of accuracy. (2) For a high-altitude tunnel with a 3 km long flat guide and inclined shaft, the internal air pressure remains constant as the distance from the cave entrance increases. However, the ambient temperature rises by 6–––8 °C, the oxygen content reduces by 1.6 %, and with the continuous excavation of long tunnels, related factors will undergo significant alterations. (3) From 0 to 4 km altitude, the maximum explosion shock wave pressure decreases by up to 26.78 %. Conversely, the maximum flame propagation speed increases by up to 21.04 %. The peak flame temperature effect becomes more pronounced, and the adiabatic flame temperature lowers. Atmospheric pressure and oxygen content significantly impact explosive properties, while ambient temperature has minimal effect. (4) As altitude increases from 0 to 4 km, the lower explosive limit rises, and the upper explosive limit decreases. The explosion limit range narrows from 5 %-16 % to 5.4928 %-14.9448 %, reducing by 16.45 %. The explosion limit effect coefficient based on altitude is proposed, and the minimum gas concentration value of railway and highway tunnel at 4 km is recommended. These findings are crucial for ensuring the safe construction and operation of high-altitude gas tunnels.