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

The strong rapid economic growth in China has inspired the construction of new road tunnels since 21st century with a sustainable average growth rate of 20%per year.The safety of road tunnel operation has become the focus of all sectors of society now because that,once a fire occurs in a road tunnel,it is easy to cause catastrophe that imparts serious negative societal impact.Therefore,it is of great significance to study the fire risk of an operating road tunnel and establish the fire risk assessment system and method for road tunnel to reduce the risks of tunnel fires and avoid heavy casualties and property losses.There are many risk factors causing fire in road tunnel.This paper adopts fault tree to identify fire hazards in road tunnel and gets 121 minimum cutsets through Boolean algebra.By structural importance calculation,the importance of basic events in the fault tree are also analyzed.Then a series of large-scale fire tests are carried out in a tunnel testing flatform to study the fuctions of automatical fire protection facilityies as fire extinguishing systems and smoke control system to road tunnel fire suppression.Based on the comparison of heat release rates(HRRs)and temperatures between free combustion and suppressed combustion under fire control systems,it's concluded that automatical fire protection facilityies in tunnels have significant influence on fire risk management.By means of the fire risk factors analysis,questionnaires and data surveys,a fire risk assessment index system for road tunnel operation is established which is composed of three criterion layers,as personnel and management,fire-fighting facilities and equipment,tunnel and environment,and 20 secondary indexes below the criterion layers.Then,the paper utilizes fuzzy analytic hierarchy process(FAHP)to calculate the weights of each index and criterion layer.Using fuzzy comprehensive evaluation method,the fire risk evaluation criterions and risk levels of road tunnel are determined.By combination of fire risk assessment indexed system and evaluation criterions,a fire assessment result can be produced ranking with road tunnel fire risk levels eventually.All the processes above forms a fuzzy comprehensive mode of fire risk assessment for road tunnel operation.Using computer numerical simulation method and empirical formulas,the available safety evacuation time(ASET)and required safety evacuation time(RSET)are calculated and compared to estimate the expected number of casualties according to the exact fire scenario defined by event tree analysis.And the injury degrees of personnel are determined by fuzzy mathematics method to calculate the accumulative compensation limit,which all constitute the comprehensive casualty assessment model for road tunnel fire is built.Combined the fuzzy comprehensive model of fire risk assessment with the comprehensive casualty assessment model,a comprehensive model for fire risk assessment in road tunnel operation is set up to evaluate the fire risk level of road tunnel and to estimate the casualties condition and compensation limit,which can provide a more accurate and careful fire risk assessment method for road tunnel operation.By using the comprehensive fire risk assessment model,this paper puts forward specific measures to control fire risks in road tunnel operation,including taking targeted improvement measures according to risk factors priorities based on the fire risk assessment result and transferring the fire risk to insurance company with pricing the premium rate and fee scientifically and reasonably.Besides,the insurance company could turn the passive underwriting into an active regulation by promptly grasping the fire safety situation of insured tunnel using the comprehensive fire risk assessment model.Furthermore,by adjusting the rate and premium,the risk of road tunnel and insurance company can be continuously reduced,and the benign interaction and cooperation between fire insurance and fire safety management can be realized.The above research provides new ideas and methods for fire risk assessment for road tunnel operation.And it also establishes foundations for scientific evaluation and effective management of road tunnel safety during operation period.