Study On Dynamic Comprehensive Model For Fire Risk Assessment In Sloping Road Tunnel Operation

In recent years,the number of complex long tunnels and tunnel groups is increasing year by year,the tunnel slope is more complex,and the tunnel operation fire risk is also increasing.Therefore,it is of great significance to master the dynamic change of fire risk during highway tunnel operation.In this paper,theoretical analysis,numerical simulation,field test and other research methods are used to systematically study characteristics of fire disaster factors and the spread characteristics of fire smoke in highway tunnels with slope.The main achievements are as follows:(1)By FDS numerical simulation,the asymmetric V-shaped tunnels’ the three-stage spread characteristics of fire smoke,which are flow field remodeling,a positive dynamic cycle forming,and finally stability maintaining,were proposed for the first time according the dynamic mechanism with different slope combinations.The influence of slope combination on the spread characteristics was explored.The results showed: The maximum backflow length and stable backflow length of flue gas in the low-slope side tunnel,as well as their corresponding moments,are affected by the slope difference and slope of both sides of the tunnel.There is also a critical slope difference.When the slope difference is greater than it,the fire smoke spread characteristics will no longer be affected.In addition,with the increase of the slope difference on both sides of the tunnel,the evacuation time of the tunnel with high slope decreases,and the casualties of the tunnel will be more severe;while the tunnel with low slope increases,and the casualties of the tunnel will be reduced.(2)The fault tree model is used to construct the map of fire disaster factors.Based on the multi-frequency monitoring data of tunnel’s multi-sensors,the evaluation indexes were selected from static,quasi-dynamic and dynamic time frequencies.Using LC method,the index system of tunnel fire occurrence probability and tunnel fire consequence severity were constructed respectively.Then,the Analytic Hierarchy Process is used to design the weight of the evaluation index,and the fuzzy mathematical calculation method is used to construct the fuzzy evaluation index set,the comment set,the single factor characteristic criterion,the fuzzy membership rule base with multiple index factors,as well as the corresponding fire risk event perception system.The real-time dynamic fire occurrence probability level,the fire consequence severity level,the comprehensive assessment level and event information are obtained by comprehensive evaluation.A dynamic comprehensive assessment model of highway tunnel fire risk with slope is constructed and visualization of risk perception events are achieved.(3)Taking suburban low-flow highway tunnel and highway high-flow tunnel as examples,namely,Ninghai Huashan Tunnel and Pingshui Tunnel(Taizhou direction)in Zhejiang Province,the effectiveness of the model under different types of tunnel daily operation was verified.At the same time,the model was applied to the engineering platform "Long Tunnel Fire Wisdom Emergency Platform",and full-scale fire test was carried out in Wangzhai Tunnel to verify the effectiveness of risk assessment.The verification results show that the model can effectively evaluate the fire risk of highway tunnel which has very important practical significance and application value to solve the problem of fire safety prevention and control in tunnel.