Strain Analysis Of Buried Pipeline In Soil Liquefaction Area

The soil liquefaction is one of seismic geological disasters in pipeline engineering,which has potential threats to pipeline.In this dissertation,mechanical models are built to investigate mechanical behavior of buried pipelines subjected to liquefaction buoyancy and liquefaction-induced transverse large ground displacement.Analytical methodologies are derived to evaluate pipeline deformation and strain,and some measures for paving buried pipeline in liquefied are proposed as well.The purpose of this research is to provide effective methods and references for design,construction and maintenance of buried pipelines subjected to seismic soil liquefaction.A finite element model of pipeline subjected to liquefaction buoyancy is built,the distribution of pipeline displacement and strain,and the influences of liquefaction area size are investigated.An analytical methodology is developed to investigate deformation and strain distribution of pipeline located in liquefaction soil,in which deformation coordination equation and deflection differential equation of pipeline are derived.Proposed methodology gives a new way to investigate pipeline in soil liquefaction area.Pipeline deformation and strain distribution are investigated through a series of examples,and the results are close to that of finite element method.Taking into pipe-soil interaction,finite element models of pipelines subjected to transverse large ground displacement are developed with the loading condition of ground deformation regarded as a cosine curve,the soil maximum displacement predicted by experience prediction method.Pipeline transverse deformation are consistent to ground deformation when the soil maximum displacement is less than the critical value.Axial friction between pipeline and surrounding soil induces pipeline axial force.Hereby,the basic equation of pipeline physical elongation is derived according to pipe-soil interaction in longitudinal direction,by which pipeline strain are calculated with iterative solving method based on displacement coordination equation.Taking into account the non-linear stress-strain relation of pipeline material,operating pressure and temperature,the effects of pipeline diameter,pipeline thickness,the soil maximum displacement and transverse ground displacement width on pipeline strain are analyzed as well.Several prevention and control measures for buried pipeline damage in soil liquefaction area are described.According to strain-based design method,an engineering application software is developed by which improves analysis efficiency.