Numerical Simulation Of Damage Of Buried PE Gas Pipeline Under The Synergistic Effect Of Environmental And Load Factors

Due to their advantages of environmental protection,light weight,low cost,long service life,and good seismic performance,polyethylene(PE)pipelines are widely used in urban gas pipelines.However,the performance and service life of urban buried PE gas pipelines are closely related to the complex load environment they face during their service process.Pipeline damage and failure exacerbates for the synergistic effect of multiple loads(internal pressure,ground settlement,ground occupation,temperature influence,etc.),which seriously threatens the safe use of the pipeline.In the present paper,in order to ensure the safe and stable operation of buried PE pipelines,numerical simulation research on the mechanical characteristics change of pipelines under the synergistic effect of environment and load was conducted.The main work is as following:(1)Research on the mechanical properties of PE pipes at different temperatures was conducted.PE material is a viscoelastic material.Considering the temperature sensitivity and rate correlation of PE pipe,the mechanical properties of PE pipe at different temperatures and strain rates were tested in an environmental box.The tensile test data were fitted based on the Suleiman hyperbola model,and the constitutive model of the pipe affected by temperature that changes with the strain rate and the yield failure criteria were derived.(2)Simulation study on ground occupied pressure PE pipe damage considering temperature influence.Based on the obtained constitutive model of pipes,a finite element analysis model for buried PE pipes under complex ground pressure loads was established,considering the influence of temperature.The strength and deformation of PE pipes were calculated and analyzed,and the dangerous points of PE pipes were identified.The effects of different temperatures,burial depths,PE pipe parameters(thickness to diameter ratio SDR,internal pressure),and pressure parameters(pressure load,pressure zone length,and pressure zone width)on the development of pipeline damage were studied.(3)Simulation study on the joint influence of service temperature and ground subsidence on the damage of PE pipes.Based on the obtained constitutive model of pipes,a finite element analysis model for buried PE pipe damage was established,which combines the influence of service temperature and complex ground subsidence loads.The strength and deformation of PE pipes were calculated and analyzed,and the dangerous points of PE pipes were identified.The effects of different temperatures,burial depths,PE pipe parameters(thickness to diameter ratio SDR,internal pressure),and subsidence parameters(subsidence depth,subsidence area length,subsidence area width)on the development of pipeline damage were studied.(4)Simulation study on PE pipe damage under the synergistic effect of multiple factors.Based on the obtained constitutive model of pipes,a multi factor synergistic damage finite element analysis model of buried PE pipes was established.And the finite element calculation of buried PE pipes under the multi factor synergistic effect(such as internal pressure load+temperature load+pressure load+settlement load)was carried out.The corresponding results were analyzed mechanically to determine the location of dangerous points of pipes.The degree of influence of various factors on pipe stress was studied through orthogonal design.The main control factors for pipeline damage under the synergistic effect of multiple factors was obtained.Finally,the relationship between the ultimate bearing capacity of the pipeline and the depth of soil settlement was analyzed.