Study On The Burning Characteristics Of High-altitude Railway Tunnel Fires And The Key Rescue Technology

With the implementation of China’s "strong transportation" strategy,the construction of mountain railway transportation has been rapidly developed,and the scale of construction of railway tunnels has also advanced by leaps and bounds.Among the many tunnel safety incidents,tunnel fires are at the top of the list in terms of frequency and danger.At present,scholars at home and abroad have conducted a large number of studies on tunnel fires and the safe evacuation of people,but most of them focus on plain areas,and there are relatively few results that combine the two in a comprehensive analysis,while relevant research proves that there is indeed a close link between the two.Therefore,the problems related to fire evacuation in railway tunnels have become a hot topic of recent research,especially the evacuation of fires in tunnels at high-altitudes,which is of important theoretical and practical value for safeguarding the health and safety of people.This paper takes the Ganqing Tunnel of the Xining-Chengdu Railway(located at the junction of Gansu and Qinghai at an altitude of 2930m)as an example to explore the best smoke control solution for railway tunnel rescue stations in high-altitude areas,and to verify whether the designed smoke control solution meets the safety requirements for evacuation of personnel,and then to make corresponding recommendations.That is,taking the actual Ganqing tunnel rescue station project as a starting point,based on the factors that cause tunnel fires,the Fire Dynamics Simulator(FDS)software was used to change the direction and magnitude of the longitudinal wind speed and to investigate the effect of the longitudinal wind speed on the thermal radiation and the temperature,CO concentration and visibility at the characteristic height in the Ganqing tunnel rescue station,in order to provide a scientific basis for the optimal design of disaster prevention and rescue.At the same time,based on the personnel evacuation simulation software Pathfinder,three unfavourable stopping positions are used as independent variables to verify whether the safety evacuation guidelines are met under unfavourable positions,to investigate the personnel evacuation plan and technical parameters,and to analyse and evaluate the smoke control plan.The main research results are as follows:(1)Through theoretical analysis,combined with the current situation of domestic and international research and relevant codes to determine the influencing factors of tunnel fires,based on the FDS software,five sets of tunnel rescue station fire simulations were carried out under different longitudinal wind speed magnitudes and directions,and one set of plain conditions under the most unfavourable ventilation conditions were added to analyse the development of fires in the tunnel rescue station and the contributing factors,also to explore the characteristics of fire sources at different altitudes.The results show that visibility has the greatest impact on the evacuation environment of the rescue station,followed by thermal radiation and temperature at characteristic heights,and that appropriate smoke control measures should be taken during the operational phase to reduce the impact on personnel evacuation and provide a good evacuation environment for personnel.(2)Based on the results of the FDS software simulations,the heat radiation and the characteristic height of the temperature,the CO concentration,the visibility range,the available safe evacuation time and the optimal smoke control solution were obtained for the six operating conditions in the rescue station.The results show that the higher the longitudinal wind speed,the more obvious the suppression of temperature and CO concentration at the characteristic height near the fire point,and the effect of the longitudinal wind from the downhill section is better than the longitudinal wind from the uphill section under the same conditions.(3)The Pathfinder evacuation simulation software was used to analyse the necessary evacuation times of people in three unfavourable stopping positions of the fire compartment,to compare the differences in the necessary evacuation times of people in different stopping positions,and to verify the safety and rationality of the smoke control scheme,if the safety criteria are met in all unfavourable positions,then the rest of the stopping situations are equally safe.The results show that in three unfavourable stopping positions,the time spent in the direction of the train running with the rear of the carriage facing the crossing is in turn greater than the time spent in the middle and front of the carriage facing the crossing;the consideration of the crossing capacity should be strengthened in the design process.(4)The best smoke control solution for this project is to apply a 3m/s longitudinal wind at the downhill section,which provides the longest available safe evacuation time for personnel and meets the guidelines for safe evacuation of personnel at all three unfavourable stopping positions.