The Risk Assessment Study On The Environmental Geological Hazards Along The West-East Nature Gas Pipeline

The West-East Pipeline runs through our country from the west to the east, and passes through various areas of geography, topography and humanity. Along the pipe, the geologic conditions are very complicated and geologic hazards are active and occur frequently. Thus the pipeline is under great threats, and severe economic losses may be caused. Moreover, due to the short period of working, a systemic and theoretically sound criterion for disaster estimating and reduction is in need, so confusions are caused in terms of hazard assessing and treatment. For this reason, this thesis attempts to do some useful discussion on risk assessment of pipe environment.The thesis aims at the geologic hazards along the pipeline. The geologic background, economic and humanity conditions are presented on the basis of field investigations and existent data analysis. Types of geologic hazards along the pipe are analyzed, and forming mechanisms, developing and distributing of the hazards are briefly discussed. Main influence factors of the geologic hazards along the pipeline are analyzed and discussed in detail.In the thesis, the most overwhelming hazard types are chosen as cases of risk assessment, such as flood erosion, landslide, mudflow, and excavation subside. Hazards are analyzed in terms of their fatalness and destructive effects, whereas the former is mainly concerned with hazard triggering conditions, such as rainfall, topography and lithology, who estimates the possibility of hazard incidence, while the latter mainly focuses on the bearing conditions of the related objects (the pipe and its surroundings), such as burring depths of pipe, precaution measurements, and pipe locations, who estimates the possibility of damages, and provides a contributing factor(0～1) for each influence factor. An index system as well as a mathematical model for geologic hazards risk assessing are established.Based on various types of risk assessment, the thesis points out the inadequate of other research of assessing methods in geologic hazards. Finite grading hides the importance of influence exerted to the pipe by environmental geologic hazards. The thesis puts forward an application of fuzzy overall judgment method and offers an arrangement analytic procedure to assess quantificationally the risks of the geologic hazards, and makes an assessment at several chosen typical flood erosion sites, where the assessing results are satisfying.In the end, unsolved problems concerning assessment of geologic hazards round long oil and gas pipes are pointed out, and expectations of assessment of geologic hazards around pipes are expressed.