Evaluation of Aseismic Design Parameter of Buried Pipeline during Liquefaction

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Objects of this study are to clarify the non-linearly behavior characteristics of buried pipeline subjected to large ground deformations and to evaliate the important parameters such as soil spring or joint spring for the effective aseismic design model. Particularly we focussed on the large ground deformations induced by soil liquefaction during strong ground motion and performmed laboratory test for the soil springs and build up the analytical method for seismic response of buried pipeline including its joints. Liquefaction tests using the the model pipeline in sand box on shaking table are performed. From the results of shear strains, pore pressures and accelerations the non-linearly characteristics of restorning forces of pipeline-ground system during soil liquefaction are investigated. Experiment for the lateral flow induced by soil liquefaction is also performed. Analytical method which simulates the ground improving method against liquefaction as dynamic compacting method is also developed for evaluating the effects of the countermeasure against liquefaction.Numerical analysis programs for soil liquefaction and lateral flow induced by it are developed on 2 dimensional FEM.Accuracy of these methods is confirmed by comparing the analytical results with experimental or measured results. Behavior of pipeline in soil liquefaction environment is analyzed, which is based on a beam on an elastic foundation. Using modified transfer matrix method as analytical tool, numerical computations are performed for displacements and internal forces of pipeline and joints, and important parameters for aseismic of pipeline are evaluated.