Study On Risk Evaluation Of Tunnel Gas Disaster

Gas disasters often happen in the process of gas tunnel construction, such as gas poisoning, gas burning and explosion, coal and gas outburst and so on. As a consequence, casualties and damage of equipments are caused, construction period will be delayed, and project construction cost increases. Then, it is very necessary to do the comprehensive evaluation of gas disaster risk.On the basis of gas and geology theory, several evaluation methods were used to do the research on gas disaster prevention in the process of gas tunnel construction. The main research contents are shown as follows:(1) By analyzing the occurrence mechanism of main gas disasters and its influence factors, the gas disaster risk evaluation system of tunnel was set up.(2) In the survey stage, the Fisher discriminant method was adopted to predict the gas tunnel grade, in order to provide guidance for tunnel design and construction.(3) In the construction stage, the attribute recognition theory was used to divide the grade of gas work area in tunnel, combined with the site survey material.(4) In the cutting through coal seam stage, the extension evaluation method was used to predict the grade of gas outburst risk, in order to provide decision-making basis for accident prevention.(5) The hazard identification theory was used to analyse the reason of tunnel gas explosion, then the accident tree was build, in order to get the accident prevention ways and measures.By researching the contents above, the main results were made as follows:(1) The evaluation results of FDA model show that the return discriminant accuracy of34training samples is100%and the prediction accuracy of36prediction samples reaches94.4%, which just meet the need of engineering application well.(2) Taking the right line of Zipingpu tunnel as an example, its26gas work areas are classified by the attribute recognition evaluation model, the results of which are in agreement with the practical verification.(3) According to the hierarchical evaluation indices system of gas outburst risk of tunnel face, the gas outburst grades of three coal samples and their relative size are concluded with the two level extension evaluation method, which is compared with the result of the single level extension evaluation method. The conclusion matches with the practical situation well.(4) The fault tree of gas explosion is established, and then the196ways to happen and3ways to prevent of the gas explosion accident are analyzed to provide some suggestions for the accident prevention in the process of gas tunnel construction.