The Finite Element Analysis For Mechanical Response Of Buried Pipeline In Liquefied Soil

Urban underground lifeline engineering is widely used in heating, water, and oil transportation. It is an important part of urban infrastructure. Seismic destruction and disaster of underground pipeline become more serious under strong earthquake striking. Destruction of underground pipelines will threaten urban safety, which results in huge losses of life and property. Therefore, the study of urban buried pipeline damage is of great value for city construction projects in disaster prevention and reduction.An analytic model of pipe soil contact-soil spring for the mechanical response of buried straight pipeline in liquefied soil is established by using finite element analytical software ADINA. The floatation displacement and axial stress curves of the buried pipeline caused by floatation response are analyzed. The larger the diameter of pipe, density of liquefied soil, length of liquefied area,amplitude of earthquake acceleration and the smaller the depth of pipe buried,thinner wall of pipe are, the easier the pipe deformation is and the more seriously the pipe damages.An analytic model of pipe soil contact-soil spring for the mechanical response of buried bending pipeline in liquefied soil is established. It is found that the bending section will be the most serious part of the whole pipe net when it exists in the liquefied soil. And it is found that there is an optimum position which makes the effective stress of elbow minimum and the bigger the wall thickness of elbow, radius of curvature are, the more difficult the deformation and damage of pipe are.An analytic model of fluid-structure interaction of buried pipeline in liquefied soil is established. It is found that fluid-structure interaction should never be ignored according to the comparison of several models. And it is the most dangerous situation when the pipe is empty. The maximum floatation displacement and stress versus the velocity and density of fluid are analyzed. The larger the velocity and the smaller the density of fluid are, the more serious the floatation of pipe is.Based on some results and conclusions above, some advices are proposed for the protection of buried pipelines in engineering. Also, theoretical evidences for design, construction and protection of buried pipeline under liquefied field are provided.