Dynamic Response Analysis Of Buried Pipelines With Corrosion Defects Under Impact Of Falling Rocks

The destruction of buried pipelines caused by the rockfall disaster greatly affects the safe operation of the long distance pipeline,and these disasters are difficult to predict and prevent and control in advance.Analyzing and correctly understanding the impact of rockfall on buried pipelines and establishing the limit state equation of reliability can provide suggestions for the treatment and protection of rockfall.Therefore,by analyzing the mechanical analysis model of buried pipelines under rockfall impact,the dynamic response of buried gas pipeline under rockfall impact is studied,and the main factors causing pipeline failure are found out.It can not only objectively and correctly evaluate the safety of the buried gas pipeline,but also provide the basis for the management planning of the collapse and rockfall,and improve the efficiency of the management.In this paper,ANSYS/LS-DYNA dynamic finite element software is used to analyze the dynamic response of buried pipeline and corrosion defect pipeline under the impact of rockfall.The research content and some research results obtained:(1)After reading and analyzing many related documents,the following conclusions are summarized:the response of soil and structure under the impact of rockfall,the dynamic response of buried pipelines,the reliability of buried pipelines,and the corrosion research of oil and gas pipelines.Through comparison and analysis,the research of this paper is drawn up,and the related mechanics model and theoretical foundation are also obtained.(2)By summarizing the previous research on rockfall impact,according to the material characteristics of rockfall,soil and underground pipelines carefully consider unit selection,parameter determination,constitutive relation and the definition of material between the contact and boundary condition,right by ANSYS/LS-DYNA dynamic finite element software through repeated calculation and comparative analysis and prove the model then,the finite element model of rockfall impact of buried pipelines.(3)The dynamic response of buried pipeline under the impact of rockfall under different working conditions is analyzed.It is concluded that the impact of rockfall on the impact process of buried pipeline is very short,and it is a transient stress process.The influence of pipe falling parameters,including rockfall velocity and rockfall volume,on the dynamic response of buried gas transmission pipeline,including pipe diameter and wall thickness,is analyzed.It is concluded that the change of rockfall parameters has the greatest influence on the dynamic response of buried pipeline,and the change of pipe parameters affects the dynamic response of buried pipeline.(4)The complex corrosion shape defects are simplified into a simple rectangle and the local thinning model of corrosion defects is established.Analysis of thin depth C length A,width B,anti corrosion change,the dynamic response of buried pipeline and the ultimate bearing capacity of rock,as well as the different diameter thickness ratio D/t and diameter to thickness ratio of the same pipe diameter changes,research pipeline mechanical effect and ultimate bearing capacity of rock.It is concluded that with the increase of corrosion size,the thinning depth of the corrosion defect parameters has the greatest influence on the bearing capacity of buried pipeline.With the decrease of diameter to thickness ratio,the peak stress peak gradually decreases with the decrease of diameter to thickness ratio.The stress peak of pipeline with the same diameter to thickness ratio and different diameters increases with the increase of defect depth,and decreases with the increase of pipe diameter,and increases with the increase of rockfall speed.(5)According to the reliability theory,determine the relevant function and the random variables,and according to the analysis of the dynamic response,the five kinds of diameter to thickness ratio of pipeline in different speed under the maximum von Mises pipeline of rockfall impact stress changes and different rockfall impact velocity in different corrosion depth representative value of pipeline C in case of von Mises stress change.The equation of the limit state of the pipeline under the above conditions is fitted.