Research On Optimal Selection Of Automatic Fire Extinguishing System For Utility Tunnel

At present,China is vigorously promoting the construction of urban utility tunnel.However,the installation of many power cables together in the utility tunnel also increases the probability of fires.Once a fire occurs,it will seriously affect the production and living electricity in large areas.The "Technical code for urban utility tunnel engineering" only requires that an automatic fire extinguishing system should be installed in the power cable compartment.This code and other professional design code do not specify which automatic fire extinguishing system should be adopted,and there is no clear setting form and setting parameters.At present,there is still much controversy among designers about the selection and practice of automatic fire extinguishing system for utility tunnel.The previous research is limited to the level of simple comparative analysis of the performance of each fire extinguishing system.This article studies this issue.This paper takes the urban utility tunnel as the research object,and briefly introduces the definition,composition,classification and characteristics of the utility tunnel.It is clear that compared with other buildings,the utility tunnel has the characteristics of narrow space,many high-voltage cables and large fire load,etc.It can not completely copy the fire extinguishing system practices of other types of buildings and directly apply to the utility tunnel.The fire in the utility tunnel is mainly caused by the cable fire.The fire in the utility tunnel has the characteristics of concealment,rapid spread,difficulty in fighting from the outside and wide influence range.Fire-fighting measures in the utility tunnel include civil fire-fighting measures,electrical fire-fighting measures,ventilation fire-fighting measures and fire-fighting measures,among which fire-fighting measures are the only active fire-fighting measures,which bear the main fire-fighting functions.After analysis,it is pointed out that the main automatic fire extinguishing systems in the utility tunnel are three systems: water spray fire extinguishing system,water mist fire extinguishing system and super fine powder automatic fire extinguishing equipment.Among them,water mist fire extinguishing system has obvious advantages in safety,super fine powder fire extinguishing equipment has obvious advantages in simplicity,and water spray fire extinguishing system has great advantages in economy.These three kinds of automatic fire extinguishing systems have their own advantages and disadvantages.It is impossible to directly determine which one is the comprehensive optimal setting scheme of the utility tunnel automatic fire extinguishing system only from the perspective of performance analysis.On the basis of performance analysis,this paper adopts the analytic hierarchy process to establish the hierarchical structure model of the utility tunnel automatic fire extinguishing system,and uses the data scored by experts to construct the judgment matrix for analysis and calculation.The research in this part shows that:1.Safety factor is the most important factor to be considered in the selection of fire extinguishing system of utility tunnel.2.The success rate of fire extinguishing,the size of pipeline and the initial construction cost account for the largest proportion in the first-level indicators.3.The success rate of fire extinguishing and the size of pipeline are the most important evaluation indicators for selecting the overall scheme,which have the largest combined ranking weight relative to the overall objective.4.According to the calculation of total sequence of layers,the super fine powder fire extinguishing equipment has the highest level of the overall ranking.In the engineering practice,it is suggested to use super fine powder fire extinguishing equipment in the utility tunnel.Finally,this paper puts forward some suggestions for the optimization design of the super fine powder fire extinguishing equipment in the utility tunnel.