Study On The Evolution And Risk Assessment Of Urban Gas Pipeline Network Leakage Disasters

Nowadays the demand for gas in cities is increasing exponentially,and gas has become one of the main energy sources for urban production and living.As the gas transport engineering facilities,the gas pipeline network is an important part of the city lifeline system.Leakages of gas pipeline network occur frequently as China’s urban gas pipeline network has entered the stage of accidents prone.The leakage accident is easy to evolve into a series of secondary disasters and derivative disasters,and it will cause huge losses.Therefore,it is especially necessary to study the evolution of gas pipeline network leakage disasters and disasters risk assessment.Through the review,it is found that there is a lack of research on the evolution of urban gas pipeline network leakage disasters,and the risk assessment method is less concerned with the effects of disaster factors.Therefore,the gas pipeline network leakage disasters evolution chain was constructed,the leakage disasters evolution Bayesian network model was established,the evolution process and evolution mechanism of leakage disasters were analyzed,and the fuzzy mixed level risk assessment method was proposed.It can provide new perspectives and research methods for the research on the evolution and risk assessment of urban gas pipeline network leakage disasters.The main research contents and conclusions are as follows:(1)The main cause factors of pipeline leakage and the key factors of leakage disasters were analyzed based on the statistical analysis of urban gas pipeline network leakage disasters.The evolution process of leakage disasters was analyzed by studying the leakage disaster evolution chains of the storage station,the regulator station,the main pipe and the client pipe of the urban gas pipeline network.The result shows that the main cause factors of pipeline leakage are the pipeline operation factors,the external damage factors,the facility defect factors,the corrosion factors,the natural factors and the safety management defect factor.The key factors of leakage disasters are the ignition source,the gas concentration and the confined space.A series of secondary and derivative disaster consequences were evolved by the fire and explosion disasters caused by the leakage disaster,and the main disaster victims are residents’ lives,buildings,urban lifeline facilities and the environment,etc.The disaster evolution process is the result of the multi-level positive coupling between the disaster environmental factors,the disaster causal factors and the disaster victim factors.The leakage disasters evolution has the characteristics of the energy mobility,the loss expansion,the uncontrollability and controllability.(2)The disaster variables and its range were obtained by analyzing the leakage disaster evolution chains,and the disaster evolution network structure was constructed by establishing the variables impact database.The evolution mechanism of leakage disasters were analyzed through building the Bayesian network model.The result shows that the disaster evolution process involves the input variables such as the ignition source,the gas concentration and the confined space,and the 21 evolutionary variables such as the explosion disaster,the fire disaster,the building damage,etc.It also involves the output variables such as the casualties,the property damage and the environmental damage.The gas pipeline network leakage disasters can cause damage to urban buildings,city lifelines and public infrastructures,and it will bring about the gas supply interruption,the power supply interruption,the water supply interruption,etc.That will cause the enterprise production stoppage and the barriers to residents’ lives,which may lead to the adverse public opinion and the public safety incidents.The leakage disasters evolution will increase the disasters damage,and it will cause the residents’ casualties by the disasters such the fire disaster,the explosion disaster and the poisoning disaster.The environmental damage will be caused by the disasters such the fire disaster and the explosion disaster.The property loss will be caused by the disasters such the fire disaster,the explosion disaster,the building damage,etc.The critical path of leakage disaster evolution are the power supply interruption to the property loss,the power supply interruption to the adverse public opinion,the water supply interruption to the adverse public opinion and the gas supply interruption to the property loss.The key nodes of leakage disaster evolution are the gas leakage,the gas concentration,the fire disaster,the explosion disaster and the damage of city lifelines,which have an important influence on the disaster evolution process and the disaster loss.(3)The risk assessment indicator system and the fuzzy mixed hierarchy risk assessment model for leakage disasters were built in order to assess the risk level of urban gas pipeline network leakage disasters.The result shows that the risk assessment indicators system includes 28 leakage risk indicators,7 disaster causal indicators,8 disaster consequence indicators and 5 disaster evolution indicators.And there are 11 influence relationships between the different indicators,such as the overpressure and the leakage concentration,the social resilience and the social vulnerability,the buildings’intensity and the urban function dependence,etc.The procedures of the fuzzy mixed hierarchy risk assessment model are set up the mixed hierarchy model;build the subjection comparison matrix,the influence comparison matrix,and the weight mixing matrix;build the fuzzy judgment matrix between the factors set and the comment set and evaluate the risk of leakage disasters.The fuzzy mixed hierarchical risk assessment can make up for the shortcomings of previous common risk assessment methods,and this method is simpler and more accurate.(4)The vulnerability of city lifelines,the urban function dependence,the vulnerability of social,the leakage concentration and the social resilience are the key points to the risk control of leakage disasters.And some countermeasures are proposed for the purpose of risk control based on these key points.