Study On The Law Of Fire Spread In Cable Shaft And The Improvement Method Of Fire Blocking

In recent years,the threat of electrical fires to people’s lives and property has been increasing.However,due to the "chimney effect",once a fire breaks out in a shaft,flames and smoke will spread rapidly in the vertical direction,causing great harm to the cables and even the building.In this paper,we have conducted a study on the spread of fires in cable shafts and the methods of fire protection and blocking.We have constructed a fire model for cable shafts,analysed the effects of fire sources,ventilation,ageing of fire protection materials,process defects and multi-layer blocking on fires,conducted a comparative study on different blocking materials and fire stopping package processes,and verified the effectiveness of the simulation model through tests.The fire protection advantages and disadvantages of different blocking layer structures are finally analysed based on the tests.The main aspects include the following:(1)Firstly,the theoretical basis of cable shaft fires is introduced,a simulation model of cable shaft fires is constructed using FDS,results are analysed for physical quantities such as temperature,smoke concentration and heat radiation intensity,and the development trend of cable shaft fires is explored,which leads to subsequent research work.(2)From the perspective of the fire spread law,a control variable method was used to analyse the effects of the fire source,ventilation,ageing of fire protection materials,process defects and multi-layer blocking,and the physical quantities such as smoke concentration,temperature and HRR(heat release rate)inside the model during the fire were used as characteristic quantities to investigate the spread law of cable shaft fires under different influencing factors.The simulation results show that there are significant differences in the effects of these factors on the spread of fire and the temperature distribution within the shaft.(3)From the perspective of fireproof sealing,different methods of improving the sealing layer are proposed.Firstly,the fireproofing and pyrolysis resistance of two different materials are investigated;then,the three methods of fireproofing are compared and analysed: fireproofing without firestopper,half firestopper and full firestopper,and the effectiveness of fireproofing and thermal insulation of firestopper and the correctness of the simulation method are verified through tests.Finally,in the test,the same fire test conditions were established,and the two methods with different blocking layer structures were constructed,and the advantages and disadvantages of the two methods were analysed in terms of heat insulation and smoke tightness.Based on the simulation and test,this paper obtains the influence law of different factors on the spread of fire in cable shafts of high-rise buildings,and the proposed method of improving fireproof sealing can provide effective reference for the design of cable shaft arrangement and fireproof sealing.