Stress Measurement And Analysis On Natural Gas Pipeline Under Uneven Settlement

Pipeline is the most common way among different natural gas transportation ways.It is easy to destruct these pipelines which have been buried in soft back-fill soil because this soft soil has low bearing capacity and will lead to large deformation under different kinds of loads.In order to ensure the safe operation of natural gas buried pipelines,safety study should be taken on them because natural gas pipelines leakage may lead to fire and explosion accidents due to the inflammable and explosive property of natural gas.The paper comprehensively researches investigations on the stress of natural gas pipelines under uneven settlement mainly in three ways: experiment,theoretical calculation and finite element analysis(FEA).The main contents of this paper were as follows:(1)Stress measurement was conducted on pipelines with strain measurement.It obtained the stress value of every testing points and revealed the figure of stress changes monthly.The increase of axial stress is much higher than the increase of circumferential stress.(2)Based on the structural mechanics and elastic-plastic mechanics,theoretical calculation is undertaken on natural gas pipelines.And it deduced the formulations between the pipelines' axial stress and settlement displacement.The most dangerous area of pipelines under uneven settlement was on elbow between the onground and underground pipelines.(3)ANSYS software was applied to calculate the Von-Mises stress of the pipelines and contour was obtained.Compared with the testing stress in chapter 3,the relative error was lower than 3%.Based on this model,the influence of diameter,wall thickness,soil depth,soil's elasticity modulus and Poisson's ratio on the stress status of pipelines were also investigated.Increasing wall thickness and soil's elasticity modulus and decreasing burial depth and diameter can reduce the maximum Von-Mises stress of pipelines under uneven settlement.The methods and achievements of this study may offer the basis and measures for further research on mechanical characteristics of natural gas pipelines under uneven settlement.