Research On The Law And Control Of Natural Gas Leakage And Cable Fire Spread In Integrated Pipeline Gallery

In recent decades,the increasing supply pressure of urban infrastructures like electric power,communication,gas and so on have already appeared with the domestic sustained economic development.Accordingly,repeated excavation in road and mixed pull in cable caused obvious problems,which threats to the lives and property of the people.To solve this,the utility tunnel emerges at the right moment to improve the urban comprehensive carrying capacity.Whereas,once the pipelines or accessory equipment in utility tunnel go wrong,it will result in the dysfunction of cities along the route.If there is no timely response,the production and living will be affected.The gas leakage and cable fire are typical disaster accidents in utility tunnel,measures must be taken timely to control these accidents and mitigate the loss when these accidents accure.To control these accidents,mechanisms of these accidents must be ayalysed firstly.Thus,by theoretical analyses and numerical simulations,the mechanisms of gas leakage diffusion and cable fire in utility tunnel are researched.According to these mechanisms,the risk controlling measures in design stage including the methane sensor setting position,fire-alarm seletion and alarm threshold are presented.Finally,the monitoring and alarm system of the utility tunnel is designed,which realized the risk control in operation stage,with the aim to improve the operation and management level for utility tunnel.Contents mainly includes the following aspects.(1)Rely on the utility tunnel project in Liupanshui city,the gas pipeline leakage numerical model is established and the distribution of gas alarm concentration and velocity at different time under standard operating conditions are obtained,which revels the mechanism of gas leakage and diffusion.(2)About the gas leakage,the influence factors including pipeline pressure,leakage aperture,leakage angle,ventilating speed,ventilating temperature and section type are taken into consideration,and a variety of conditions are set to build corresponding numerical models,and the alarm concentration diffusion height varies with diffusion length at different time and condition is analysed.Consequently,combined with relevant standards,the setting position of methane sensor is determined,based on which,the controlling measure of gas leakage risk in design stage is proposed.(3)Rely on the utility tunnel project in Liupanshui city,the fire numerical model in cable compartment is built by PyroSim,and the cable fire process is carried through numerical simulation.Then the products in the fire including temperature,smoke,CO concentration and O2 concentration in the initial state are studied,and the mechanism of cable fire is investigated.(4)About the cable fire,the fire size,ventilating speed and ventilating temperature are considered and multiple working conditons are designed,then the fire response time of different categories fire-alarms in these conditions in the initial state are researched to determined the category of fire-alarm,with the aim to response the cable fire timely;multiple fire alarm tested thresholds and the relevant fire control response time are set,and the fire experience time at different shresholds when fire controls are taken,then the fire threshold is determined,and the validity of the threshold is validated by analyzing a variety of physical parameters at in the case of fire control.Based on the fire alarm seletion and fire threshold determination,the controlling measure of cable fire risk in design stage is proposed.(5)According to the setting of the methane sensor and the alarm threshold in the cable fire,along with the other settings of other sensors and corresponding thresholds of other parameters in relevant standards,the parameters in utility tunnel are monitored.In the meantime,the monitoring and alarm system consists of environment and equipment monitoring system,security system,communication system,alarm system and GIS geographic information system is constructed,which realizes the risk control in operation stage.