Numerical Simulation Of Strength Of Buried Polyethylene Pipes With Defects Under Typical Complex Loading

With the increasing consumption of natural gas,the proportion of PE pipeline in the gas network is increasing annually.Accidents of PE pipeline are of great harm,which has imposed tremendous threats on people's life and property.With the progress of urbanization,problems such as surface subsidence,surfacce load are increasingly worsening.These problems have made the geological environment of PE pipeline become more complicate and it is of greater significance to ensure it work safely.Whether the exported pipeline or the PE pipeline made in China,there must be defects due to various reasons.However,there are few researches on the mechanical performance of PE pipeline in the complicated underground environment.This thesis focuses on the simulating researches on the mechanical performance of the underground PE pipeline on the complicated condition of surface subsidence and surface load.The jobs it has done are the following,(1)It has selected two loading conditions of surface subsidence and surface load and studied the defected pipeline through PPDC data as well as statistic analysis of the PE pipeline out of operation and fully considering the probability and influence degree of such accidents.(2)It has selected Suleiman Hyperbolic constitutive model to carry on Uniaxial tensile tests of different strain rates so as to obtain the constitutive model and the failure criterion of PE pipeline.(3)Through ABAQUS finite element analysis software,it has established the analysis model of defected PE pipeline on the condition of surface subsidence and surface load and studied the influence and regulation of the parameters of surface subsidence and surface load as well as the parameters of defected pipeline on the mechanical performance of PE pipeline.And it has concluded,1)The pressure imposed by surface subsidence and movement has been the main cause of the bend of pipelines.When PE pipeline is bended,the max mises stress will be created in the inside pipeline's springing line.Surface subsidence and movement as well as the relatively defected degree have been the main factor of the max stress,the increase of surface subsidence,movement and the defected degree will arouse the increase of the max stress.2)The surface load of pipeline has been the main cause of the pipelines' yield.The surface load and the relative defected degree of pipeline have obvious influence on the max stress.