Reaserch On Diffussion Model And Risk Estimation For Leakage Of Toxic Gas Road Transportation By Tank Cars

As the fuel, raw material and the manufactory producing auxiliary material, the gas hazardous goods are widely applied in the numerous professions and the people’s daily life. Its road transportation safety receives attention from all circles day by day because of some marked feature such as its great variety, the complex nature, the high risk. Besides the flammable and combustible feature, the toxic action of toxic gases is the biggest threat to the public and the ecological environment. Once the toxic gas leaks out in the transportation process, it will cause serious consequences to resident’s health of life and safety of property along the route. What’s the worse, it’s difficult to evaluate the destruction and the long-term effect to the peripheral environment. Tank cars are the main tool to transport the liquid and the gas hazardous goods. The related investigation indicates that tank cars hold high proportion in the vehicles which transport hazardous goods in our country, and nearly80percents of the accidents about transportation of road hazardous goods involve them. So it is a risky activity that tank car transport of gas hazardous goods. To mak sure its security and reliability has special significance to ensure safety of people’s life and property and social stability. At present, there are some weak links in the related domestic and foreign research. And some key problems still remain to be explored and resolved. Therefore, the main study context for this thesis is as follows:①The thesis carried on systematic research to the risk analysis of the domestic and foreign transportation of hazardous goods on road, the study present situation, the trend of development and the main existing problems of the leakage and diffusion model based on the toxic gas.886accident cases about the road hazardous goods transported by tank car in our country are sorted out through the investigation on the spot, referring data, using kinds of data systems for accident. Accidental rule of the road hazardous goods transported by tank car in our country was explored, using methods such as statistical analysis and contrastive analysis, and the important statistical features such as temporal distribution, dimensional distribution, reason, type, consequence and leakage probability.②On the base of accidental features for the road ransportation of hazardous goods by tank car, taking system theory, cybernetics, safety engineering as basis, this thesis analysed the accidental mechanism about road ransportation of hazardous goods by tank car thoroughly; The analytical model for the reliability of road ransportation of hazardous goods by tank car was established, based on improved GRA (Generalized Reliability Analysis) method,which provides the theory basis of preventing accident and slowing down risk.③Because the probability of accident about road tranmportation of hazardous goods in our country is calculated depends on overseas data, the overseas data was corrected reasonably and the computational method conforming to China conditions for the probability of accident about road transportation of hazardous goods was proposed, on the base of the research to domestic accidental feature and the method of multi non-liner regression. ④On the base of the research to accidental severity of the toxic gas leakage, considering the demographic and the environmental factor fully, the concept and quantificational method for the medium density of population, the time-varing density of population and the sensitivity of road environment were proposed, in order to establish the risk evaluation model applied to different object.⑤Considering the accident probability and consequence, the risk evaluation model for the research to the leakage of toxic gas was established; Because the leakage of toxic gas is a potential threat to the people along road, environment, public facilities and so on, the evaluation model for the social risk based on the BP neural network was established; Because the leakage of toxic gas is a potential threat to safety of people’s life and property along road, the computational model for personal risk based on Monte Carlo method was established.⑥Based on physics-mathematic method and fact of cargo road transportation in China, dispersion equation for leakage accident of road transportation for toxic gases by tank car was derivated; problems such as diffusion parameter choosing, boundary condition setting, initial source strength calculating, source strength and location controlling were solved, and diffusion model fits for continuous leakage for fixed point source, instantaneous leakage for fixed point source and continuous leakage for moving point source were established.⑦Modern solving theory and tools were utilized to simulate the typical accident scene, such as continuous leakage for fixed point source, instantaneous leakage for fixed point source and continuous leakage for moving point source, which proved rationality and validity of the diffusion model; on the other hand, real-time spatial distribution of concentration and dangerous area in different accident scene were achieved, which can be used as the basis for counter plan making and risk analysis.At last, the established risk evaluating model was used to analysis the social and individual risk of example road section, and the risk for units and colony on sides of road were achieved; on the other hand, the established diffuse model was used to simulate an accident scene, and the counter plan, scheme for evacuation and succor according to time were put forward. It is indicated, that the established risk evaluation model for road transportation of toxic gases by tank car can reflect the risk level of road section objectively; and the diffuse model for tank car leakage accidents can describe the three-dimensional diffusion of toxic gases exactly and is closer to the fact of road transportation.