Analysis Of Mechanical Properties For Urban Gas Polyethylene Pipeline Under Typical Working Conditions

With the implementation of major projects such as "west to East Gas Transmission Project" and "Sichuan to East Gas Transmission Project" and the rapid development of the city,polyethylene pipeline has become the first choice for medium and low pressure gas transmission pipeline because of its corrosion resistance,long service life,environmental protection and low cost.However,in recent years,geological disasters,illegal construction of occupied pipelines and violent construction have occurred frequently,making the buried polyethylene pipeline face a very complex geological environment,and its safety is not optimistic.At present,the research on the mechanical properties of gas polyethylene pipes under complex loads is not mature,and the existing research results for steel pipes are not applicable to polyethylene pipes;In order to improve the safety of gas polyethylene pipeline,it is very necessary to carry out research on Gas Polyethylene Pipeline under complex load conditions,so as to provide technical support for the corresponding safety evaluation methods.Therefore,this paper conducts numerical simulation research on the strength of buried polyethylene pipes under three typical complex loads: ground settlement,ground occupation and excavation damage.The main work is as follows:(1)Analysis of mechanical properties of gas polyethylene pipe.After the tensile test of gas polyethylene pipe under different strain rates,the mechanical characteristic parameters of gas polyethylene pipe are obtained,and the six order Sherwood frost model is established.Then the six order Sherwood frost constitutive model is used to simulate the tensile process of polyethylene pipe,and the correctness of the established constitutive model of polyethylene pipe is verified.(2)Analysis of mechanical properties of gas polyethylene pipeline under the action of land subsidence.According to the characteristics of land subsidence,large strain rate is selected as the research premise of gas polyethylene pipeline under the action of land subsidence.The finite element model of gas polyethylene pipeline under the action of land subsidence is established,and the Sherwood frost constitutive model is used to simulate and analyze the process of land subsidence with ABAQUS.The mechanical response laws of gas polyethylene pipeline under different land subsidence angles,different transition lengths and different land subsidence displacements are revealed.(3)Analysis of mechanical properties of gas polyethylene pipeline under ground pressure.According to the characteristics of illegal construction around buried pipelines,the mechanical parameters of polyethylene pipes under small strain rate are selected as the simulation basis of pipelines under ground pressure.The finite element model of gas polyethylene pipeline under ground pressure is established,the influence of different pressure load and pressure load offset on the mechanical properties of the pipeline is simulated and analyzed,and the ultimate bearing capacity of gas polyethylene pipeline under different ground pressure conditions is determined.(4)Analysis of mechanical properties of gas polyethylene pipeline under excavation.On the basis of Sherwood frost constitutive model,the damage of gas polyethylene pipeline caused by excavation is comprehensively considered.By establishing the bucket pipe soil three body finite element model of buried gas polyethylene pipeline,the damage of buried gas polyethylene pipeline under different excavation forms and excavation speeds is calculated and analyzed,and four safety protection strategies for reducing the damage of buried gas polyethylene pipeline are qualitatively proposed.There are 82 figures,10 tables and 58 references.