A Study On Puried Pipeline Of Limiting Suspened Length

Along the long distance pipeline, the geology and landforms is disorderly and the natural conditions is bad, so the pipeline is very easy to be suspended under accidental load, such as landslide,collapse,loose soil settlement, the earthquake and water damage. There are seriously dangers to the operation of pipelines. So the study of suspended pipeline is necessary.Firstly, this paper analysis the load and stress when the buried pipeline accident suspended, On the basis of the the basic properties and the constitutive equation of the soil,and makes the model of suspended pipeline which is established based on Winkler hypothesis and elastic foundation beam theory.and analysis the bending moment of middle section and the place which contact with the soil.Secondly, in the range of Mises yield function,this paper determined length of suspended pipeline. Finally, based on the model of soil’s Morhr-coulomb and steel Ramberg-Osgood constitutive equation of the pipeline, using the finite element software ABAQUS, finite element model of structure static analysis is build.The following conclusions:(1)The maximum Von Mises Stress and maximum strain of the unearthed suspended pipelines appear in the upper surface of itself. The maximum displacement appears in the mid-span section of suspended pipeline, where the stress is smaller.As the span length of suspended pipeline be longer, the maximum stress, maximum strain and maximum displacement are increasing. In the elastic stage of the suspended pipeline, the maximum stress is sensitive to the length of pipeline. When suspended pipeline be local yield, the maximum stress changes slowly, where the maximum strain is sensitive to it.(2)Von Mises Stress of end unearth section of suspend pipeline,decrease first and then increased from contour line to down contour.the stress of contour line is maximum.Von Mises Stress of mid-span secction, the trend is the same tress,down contour line is maximum.(3)For X60 pipeline material,Φ508×7.4mm, soil body medium is clay, inernal pressure is 4.3MPa, buride depth within 2m of the gas pipeline, when the hung suspended length of 93 m,the maximum Von Mises stress reach the permissible stress of pipeline material. when the hung suspended length of 180 m, the maximum Von Mises Stress reach the yield strength of pipeline material. At the same condition,the hung suspended length of bured oil pipeline is 50 m, reach the permissible stress;and 73 m reach the yield strength.(4)The pipeline internal pressure of gas suspended pipeline as single variable,with the increase of internal pressure,the length dangling;in the pipewall thickness as single variable, with the increase of wall thickness,the suspended length increase.The result obtained for suspended pipe has actual evaluation guidance and provide direct thoretical data support for the pipe’s repair.