Study On Stress Analysis And Protection Of Hangzhou Ningbo Gas Transmission Pipeline Under Flood

In recent years,with the vigorous development of natural gas pipeline engineering in China,the guarantee capacity of "clean energy" has been greatly enhanced.However,at the same time,the operation of natural gas pipeline network in China is also facing great challenges.For example,the laying of long distance pipeline always cannot avoid crossing some rivers,and some rivers crossing pipelines are located in the geographical location of flood disasters are more frequent,such as flooding may lead to the exposed hanging or even fracture of the pipeline.The stress analysis and protection research of river crossing pipeline under flood action can provide important guidance for the rescue work and daily protection of river crossing pipeline.In this paper,the stress analysis of the suspended section of the river crossing pipeline under the action of flood was firstly carried out,and then the differential equations of the buried section and the suspended section of the river crossing pipeline were established respectively based on the elastic foundation beam theory.Then the analytical formula derivation and finite element static analysis based on ABAQUS software were successively carried out for the two suspended pipelines A and B.The accuracy of the finite element tube-soil model is verified by the results of analytical method.In order to make the stress analysis result more close to the actual working condition,the fluid-structure coupling analysis method which can reflect the interaction between flood and pipeline is further used to analyze the concentrated distribution law of stress,strain and displacement in the suspended section of A and B pipelines.Then the strain-based failure discrimination method is used for safety discrimination of pipeline A and B.The influence of crossing the river at different angles on the stress and strain distribution of the suspended pipeline is analyzed.Finally,the ultimate hanging lengths of pipelines A and B under the current flood velocity are calculated.In order to study the time when the maximum stress of pipelines occurred during A real flood outbreak at the crossing position of pipelines A and B,A typical flood outbreak and regression process line was selected in this paper to conduct dynamic time history analysis on pipelines A and B.It shows the dynamic change of pipeline force in the process of flood rising and falling.In order to distinguish whether A and B crossing the suspended pipelines have the possibility of resonance with flood,modal analysis and eddy current frequency analysis were carried out on the suspended pipelines A and B respectively,and the natural frequency and eddy current frequency of the pipelines were obtained.The effects of the suspended length and the properties of soil layer on the resonance of the pipeline are studied.According to the results of stress analysis in the third chapter,using the control variable method to further study the pipeline parameters,flood and soil parameters such as the main influence factors on the river through the influence regularities of the variation of the suspended section stress,and find the key influence factors,for both safety and economy of the pipe laying and provide reference for operation.Then,from the perspectives of emergency treatment and daily protection of suspended pipelines,specific flood emergency treatment measures and daily protection measures are proposed for hangyong line A and B crossing pipelines and other river crossing pipelines of Hangyong Line.Based on the above research,develop a flood under the action of gas through the pipeline failure determination and protective Suggestions software,can realize the flood under the action of the fast calculation of pipe stress distribution and rapid calculation of the limit length of dangling,and can carry on the operation state of suspended pipeline preliminary judgement and suggest specific emergency control measures,etc.