Semi-quantitative Risk Assessment For Single Geological Hazard Endangering Pipeline

Geological hazards along the natural gas pipeline seriously affect the safe operation of the pipeline.In this paper,a semi-quantitative risk assessment system suiting for study area is trying to be established to determine the pipeline risk level of geological hazards according to the characteristics of geological hazards and the reality of pipeline.In this paper,collapse and landslide are selected as the types of hazards to be evaluated.By referring to the most widely used semi-quantitative evaluation model,the evaluation system is divided into two parts: the vulnerability of geological hazards and the vulnerability of pipelines.Based on the geological hazards investigation report,the influencing factors of the pipeline geological hazards are collected,analyzed and summarized in the form of historical geological hazards data collection and analysis combined with field investigation.Based on the contribution rate model,factor sensitivity analysis is carried out on the factors of pipeline geological hazards.According to the sensitivity value,the factors are divided into high sensitivity factors,medium sensitivity factors and low sensitivity factors.Factor correlation test is carried out for high and medium sensitivity factors,and factors with obviously low correlation are eliminated,and the others are taken as evaluation indexes for pipeline geological hazards.The Ward system clustering method is used to classify the evaluation indexes,and a classification system of the evaluation indexes is constructed.Through the analytic hierarchy process(AHP),the relative weight values of the indexes in each classification system are calculated,and the final evaluation index system of the pipeline geological hazards is determined to form the semi-quantitative risk evaluation model of the single pipeline geological hazards.Finally,the semi-quantitative risk evaluation model is used to evaluate the risk level of 60 typical geological hazards.The results of the semi-quantitative risk evaluation model are compared with those of the qualitative evaluation in the geological hazards investigation report,and the consistency of the evaluation results is 50%.For the different part of the evaluation results,the proportion of the evaluation results of the semi-quantitative risk evaluation model is85% more serious than the qualitative evaluation results.On the whole,the semiquantitative risk assessment model is more conservative than the qualitative one.In the evaluation of hazards vulnerability,the semi-quantitative risk evaluation model can more intuitively see the impact of index changes on the evaluation results,which provides a theoretical basis for the monitoring and prevention of geological hazards.