Study On Fire Smoke Laws And Temperature Longitudinal Decay Model In High-altitude Spiral Tunnel

In recent years,with the continuous development of China’s economy,the number and mileage of road tunnels are increasing,and high-altitude spiral road tunnels are constantly emerging.The rise in altitude,the change in tunnel linearity and the increase in longitudinal slope all increase the hazard caused by tunnel fires to varying degrees.Therefore,it is important to study the combustion characteristics,temperature distribution and smoke spread pattern of high-altitude spiral tunnel for disaster prevention and rescue engineering design.This paper adopts research methods combining field tests and numerical simulations,theoretical analysis and practical verifications,and the main research contents and results are as follows:(1)High and low altitude curve tunnel scaling test models and numerical simulation models with tunnel curvature of ρ=0,ρ=1/100 and ρ=1/250 are established respectively.The fire smoke temperature distribution law of different altitudes and curvature tunnels is analyzed.The results of the scale-down model tests and numerical simulations in plain and high-altitude areas are compared,and the simulation results of Pyro Sim software are verified to be correct and reasonableness.(2)Using Pyro Sim simulation software,3D dynamic models of high-altitude spiral road tunnel fires combustion are established for different varying parameters,including different tunnel curvatures(ρ=0,ρ=1/100,ρ=1/250),different altitudes(0m,2000 m,3000m,4000 m,5000m)and different slope(0%,3%,5%,7%).The influence laws of different variables on the longitudinal distribution of the tunnel fire temperature and smoke spread are calculated to provide a basis for the derivation and modification of the longitudinal decay model of fire temperature in high-altitude spiral tunnels.(3)The applicability is verified of the classical smoke layer temperature decay model in the longitudinal direction in fires to high-altitude spiral tunnels.The results show that the classical smoke layer temperature decay model can provide good prediction results for plain and high-altitude straight tunnels,but the results differ significantly from tunnels with curvatures of ρ=1/100 and ρ=1/250,and slopes of 3%,5% and 7%.Therefore,models are developed to predict the smoke layer temperature decay model in the longitudinal direction applicable to spiral and sloped tunnels,taking into account the effect of tunnel curvatures and slopes.