Stress Analysis And Influence Research On Weld Area Of Buried Pipeline In Settlement Area

The geology and geomorphology along the long-distance pipeline are intricate and the natural conditions are bad.The buried ground is easily affected by geological disasters and leads to large-span suspension,which will cause pipeline stress concentration,pipeline deformation,and serious failure of the pipeline.Serious hidden danger.According to the investigation of pipeline accidents,most of the pipeline failure locations are in the weld zone of the pipeline,and the existing research on the settlement of suspended pipelines does not consider the girth weld in the modeling,so it is very useful to study the influence of the girth weld on the suspended pipeline,necessary.The research object of this paper is the X80 natural gas pipeline with a diameter of 1219 mm,a wall thickness of 18.14 mm,and an operating pressure of 12 MPa.The effect of girth welds on the safety performance of settlement suspended pipelines was studied by a combination of theoretical analysis and numerical simulation.Firstly,based on the Winkler hypothetical elastic foundation beam theory,the pipe-soil action model of the settlement suspended pipe is determined;secondly,the failure criterion of the settlement suspended pipe is determined through the research on the failure criterion of the pipeline and the stress characteristics of the suspended pipe;Settlement suspended pipeline model with girth welds and finite element analysis of pipe-soil models with different suspension lengths.When girth welds are close to the unearthed end of the suspended pipe,stress concentration will occur,which is farther from the unearthed end of the suspended pipe.The stress concentration of the girth weld is not obvious.The failure point of the settlement suspended pipeline is still located at the two unearthed ends.The safe suspending length and limit suspending length of the settlement suspended pipeline with girth welds are obtained.Analysis of pipeline accidents shows that most of the long-distance pipeline failures occur in the weld zone,mostly due to defects in the weld zone,which leads to the failure of the pipeline under load.Finite element simulation analysis was carried out on the situation of miter defects with girth welds,and the safe suspending length and limit suspending length of sinking suspended pipelines with defects were obtained.When the pipe end of the dangling area contains the wrong edge defect,it has a great influence on the safety of the pipeline and the limit hanging length decreases with the increase of the amount of wrong edge.When the pipe end of the suspended area contains a girth weld defect,it also has a great impact on the failure of the pipeline.By comparing and analyzing the stress,strain and displacement of the pipe under different miter angles,it is found that the limit overhang length also increases with the miter angle decreasing.The results obtained through this paper have a guiding role in evaluating the actual settlement of suspended pipelines,and provide direct theoretical data support for pipeline maintenance operations.