Research On Smoke Control Technique And Attenuation Law Of People’s Athletic Ability In Road Tunnels In High-Altitude Areas

With the development in our country’s traffic system,more and more traffic tunnels have been constructed in western areas where the altitude is higher.With the increase in altitude,the ambient environment featuring low oxygen content,ambient pressure and temperature may influence smoke control and people’s athletic ability,like longitudinal ventilation design parameters,critical condition for plug-holing,and people’s athletic ability,but related research is rare,so it is necessary to explore the effects of altitude on these problems.As a result,data mining,theoretical analysis,numerical simulations,and field tests are adopted to do the technical research and the findings are as follows:(1)Investigating the effects of the altitude on the fire development,it is found that it takes more time to reach the peak heat release rate in high-altitude areas,which is also smaller than that in plain areas;effects of the altitude on fire smoke movement characteristics without ventilation were explored,and it is found that the smoke temperature and velocity increase with the decrease in ambient pressure while the influence of altitude on smoke thickness is negligible.(2)The method to obtain the critical velocity and back-layering length at different altitudes based on previous formulas and experiments in this study is brought out,and it is found that the critical velocity and back-layer length increase with the decrease in ambient pressure when the dimensionless heat release rate is small,but when the dimensionless heat release rate reaches a specific value,the critical velocity and back-layer length remain stable regardless of the ambient pressure;investigating the effects of altitude on the smoke stratification,it is found that smoke is more stable in high-altitude areas due to higher smoke temperature.(3)The longitudinal temperature distribution under the shaft was adopted to determine the occurrence of plug-holing in a tunnel fire with mechanical smoke extraction ventilation,and the variation of vertical temperature distribution and smoke height with smoke extraction velocity varying were investigated,and the Froude numbers under different ambient pressures were obtained;the longitudinal temperature distribution under the shaft was adopted to determine smoke movement pattern in the vertical shaft in a tunnel fire with natural ventilation,and the variation of vertical temperature distribution and smoke height with shaft height varying were investigated,and the Richard numbers under different ambient pressures were obtained.(4)It is found that both tunnel environment and low oxygen content decrease the evacuation speed;two factors which are tunnel correction coefficient and altitude correction coefficient are obtained based on experiment results;tunnel correction coefficient remains stable regardless of altitude while altitude correction coefficient decreases with the increase in the altitude;the reason for smaller walking speed inside the tunnel is the low illumination which hinders people obtaining the road information while other environmental parameters and people’s physiological and psychological reactions are similar to those outside the tunnel;lower speed in high-altitude areas is due to low oxygen content which decreases people’s blood saturation and increases heart rate before and after the exercise and drives people into a state of fatigue according to heart rate variation parameters and fatigue perception questionnaire.