Research On Mechanical Performance Of Buried Steel Gas Transmission Pipeline Crossing Strike-slip Fault

As one of the main reasons for the failure of buried pipelines crossing strike-slip faults,the fault displacement caused by earthquake may cause huge compression,tension and bending strains in the pipeline,leading to local buckling,tensile fracture and ovalization failure,and seriously threatening the safe operation of the pipeline.In this paper,the finite element model of buried pipeline across strike-slip fault based on equivalent boundary is established by ABAQUS finite element software,and the mechanical performance of buried pipeline across strike-slip fault is studied.Considering the two cases of bare steel pipe and steel pipe wrapped with insulation layer,the main contents of this paper are as follows:(1)This part reviews the research status of buried pipelines across faults from three aspects of theoretical research,experimental research and numerical simulation,and points out the limitations and deficiencies of the current research.(2)Research on finite element model of buried pipeline crossing strike-slip fault.Through the pull-out test simulation,the unit length friction between pipe and soil is determined,and the equivalent boundary spring at both ends of the pipe is further determined to improve the efficiency of numerical simulation.Nonlinear contact is adopted between pipe and soil,penalty contact is adopted in tangential direction and hard contact is adopted in normal direction.Ramberg-Osgood model is adopted for pipes and ideal elastic-plastic MohrCoulomb model is adopted for soil.Through the sensitivity analysis of finite element mesh,the finite element mesh density is determined in this paper.(3)Research on the basic laws of mechanical performance of buried pipelines crossing strike-slip faults.This paper mainly studies the evolution laws of axial tensile and compressive strain and elliptical deformation of pipeline with the development of displacement.Meanwhile,the critical fault displacement of each performance standard of insulated pipeline and non insulated pipeline is analyzed,so as to judge the fault dislocation resistance of the two kinds of pipelines.Secondly,the difference of the maximum tensile strain of the pipeline obtained by the numerical simulation method and the standard method is compared,and the possible causes of the difference are given.It is suggested that numerical simulation should be used in the design of anti strike-slip fault pipelines.(4)Research on influencing parameters of buried steel pipeline under strike-slip faults.The effects of pipe diameter thickness ratio,intersection angle of pipeline crossing fault,operating internal pressure and friction coefficient on axial tensile and compressive strain and ovalization of two kinds of pipelines are studied.The development law of the critical fault horizon when the pipeline has tensile failure,buckling failure and elliptical failure under different parameters is studied,and the critical failure fault displacement under each performance standard of two kinds of pipelines under the same working conditions is compared.According to the analysis results,the corresponding seismic suggestions are put forward.Based on the finite element model of buried pipeline crossing strike slip fault with equivalent boundary springs at both ends,this paper studies the basic laws of mechanical properties and the influence of various parameters of buried pipeline crossing strike slip fault,and gives design suggestions combined with the research results,so as to provide reference for pipeline earthquake prevention and disaster reduction.