Study On Multi - Factor Coupling Disaster Mechanism And Disaster Control Of Urban Gas Pipeline Leakage

With the rapid development of urban economy, increasing demand for gas, pipelines as a major tool for urban gas transportation, are more likely to be occurrence of leakage failure affected by the complex urban environment, under the circumanstance of the common disaster factor, the disaster consequences of city gas leakage is more serious, and disaster situation is more complicated. Therefore, the hazards mechanism research of city gas pipeline leak under multivariate coupling based on system science can comprehensively grasp the configuration of gas pipeline leak disaster system, unveil the multi-factor coupling mechanism and disaster evolution precedure, lastely, and provide a theoretical basis for city gas pipeline leak disaster prevention and control. In this paper, some of the key issues concerning the city gas pipeline leak disaster are reseached as following:(1) defines the connotation of city gas pipeline leak disaster, based disaster science and system science, and proposes the gas pipeline leak disaster system framework which containes disaster-environment, hazards, hazard bearing body, disaster, and adopt statistics and scenario analysis to obtain a three-tier index system of disaster. Statistics findes that the city gas pipeline leak disasters feture fires and explosions, there is a correlation conversion phenomenon within the disasters. Separately each of the three-tier indicators was analyzed to mastere the system behaviors influenced by disaster. Disaster system environment, structure and function were analyzed, and finding that the system function is to produce disasters, disaster environment includes social and natural environment. The process of city gas pipeline leak was analyzed, and finding that there exist time effects, spatial effects and coupling effects during the disaster process. A mathematical model is constructed about hazards process based on the disaster- environmental stability, hazard risk, hazard bearing body vulnerability, and describes the loss rate and the loss of the disaster system.(2) using mathematical language to describe the disaster system coupling process, according to the number of coupling factor to classify coupling type and analyze coupling effect, with the concept of chemical functional groups, describes the coupling process of pipeline leak disaster system. System dynamics is adoptted to construct different types of disaster system coupled causal relationship models, and systemic factors coupling paths are presented. Coupling degree model of the city gas pipeline leak disaster is constructed, and entropy method is taken into consideration to modify the model and effectiveness of the coupling degree model is proved by empirical research, the model can be used for coupling degree evaluation of city gas pipeline leak disaster system.(3) Based on graph theory, the dynamic hazard-formation process of city gas pipeline leak is characterized under multivariate coupling conditions, namely in the long-term process of urban construction and development, gradually forming a complex disaster environment, it is together influenced by the social environment and the natural environment, urban hazard bearing body which consists of urban society- economy-environment, is inseparable with disaster environment, they almost occurs simultaneously and firstly coupling. In addition in disaster environment as a gas pipeline leak, it could give rise to fire, explosion, toxic gases and other hazards, and disaster environmental coupling with hazards make hazards more destructive, when disaster environment- hazards- hazard bearing body interact at the same time, the disaster is on occurrence. The process of disaster bearing bodies acting on hazards is the process of disaster relief and disaster controlling.(4) The analysis on feedback effects and delayed effects of the disaster system based on the system dynamics findes that positive feedback accelerate disaster occurrence, the negative feedback stabilize the disaster, delay effects influence disaster information transfer and rescueing speed. System modeling purposes, reference mode, the system boundary are explicit, a block diagram analysis make clear of the disaster information flow direction within the system. The ideas fire hazard subsystem, explosion hazard subsystem, poison gas disaster subsystem modeling are proposed and Vensim is used to construct system dynamics model of the city gas pipeline leak disaster, system static analysis clearly show the subsystem boundaries and major feedback loop.(5) Setting the disaster scene to to carry out empirical analysis, after establishing system equations and inputting parameters and the model has been debugged and tested. Simulation analysis found that the system is better coincide with the reference model, the degree of disaster losses presented "S" growth, the rate of disaster loss is in quadratic parabolic growth, and explosion growth is the fastest, followed by fire, poison gas is slowest. The increase of the coupling degree of disaster subsystem will boost the rate of disaster losses, and the increase of coupling degree between the subsystems will boost the degree of disaster loss, disaster relief capacity reduction will cut down the rate. There is almost no effect on disaster relief when the delay time is less than 0.25 Hour, on the contrary the delay greater than or equal 0.25 Hour, with the delay time increases, and the disasters lose rate speed up.(6) On the basis of research on multi-factor coupling disaster-causing mechanism of city gas pipeline leak, the failure and leak prevention measures is proposed on account of accident causation theoryand disaster control measures is appeal based on the decoupling theory.