Study On Urban Gas Pipeline Network Construction Environmental Risk And Countermeasures

In this paper,the newly built urban gas pipeline netwoek was taken on as the research object.Combined with regional characteristics of Liangjiang New Area and Changshou District of Chongqing,features of pipeline construction were described. Urban gas pipeline construction environmental risk accidents fault tree and processes fault trees including design failure, construction failure, operational failure were built.Factors may causing the pipe network environmental risk through the whole process(design, construction and operation process) of pipeline construction and their potential hazards were identified with the use of fault tree analysis.In order to determine evaluation index from those fators,we consulted experts based on scientific,data availability and any other principles.Then,urban gas pipeline network construction environmental risk assessment index system were established,which consisted of one first-level indicator, fourteen secondary-level indicators and 42 third-level indicators.Based on the above-established evaluation index system, the three fuzzy comprehensive evaluation model was constructed by the method of fuzzy comprehensive evaluation.Using 1-9 scale method proposed by Professor Saaty,seventeen judgment matrixs were built according to experts rating.Then,using the analytic hierarchy process(yaahp V7.5 software),the index weight was determined and index weighting matrix A was obtained.Combined with the division of various levels of risk and their acceptable levels in Environmental Risk Assessment and Practical Techniques and Methods,environmental risk grades of the city gas pipeline network construction were classified into five review grades,including very great(10-3 orders of magnitude), great(10-4), medium(10-5), small(10-6)and very small(10-7 to 10-9). Use the established three fuzzy comprehensive evaluation model to research the new pipe network built in Chongqing Liangjiang New Area and Changshou District,respectively.The investigated experts commented each factor’s risk level with very great,great,medium,small and very small.Then,the single factor evaluation rating matrix R was gotten, namely the membership of factors with different grades. According to the obtained single factor evaluation rating matrix R, in conjunction with the factor weighting matrix A, the multi-level fuzzy comprehensive evaluation,B = A · R,was concalculated layer by layer up.The comprehensive evaluation results of the new pipeline project in Chongqing Liangjiang New Area and the Changshou District were separately B=AgR=0.0196 0.1009 0.3463 0.3310 0.2021 and B=AgR=0.0238 0.1237 0.3652 0.2964 0.1908. According to the maximum membership principle, the final results showed that the two new pipeline project environmental risk assessment rating are both "medium", that measures need to be taken to improve the security. The environmental risk rating of siting and line selection,the crossing project and external damage of the new pipeline network in Liangjiang New Area was higher,samely safe distance, the crossing project, ground recovery and external damage of pipe in the Changshou District.At last,corresponding countermeasures and environmental risk contingency plans were put forward contrary to the above-identified factors which should be focused on, providing references for operating units to make contingency plans and offering a theoretical basis to protect the safe operation of the urban gas pipeline network.