River-crossing pipeline is threatened by flood which could induce pipeline being eroded and exposed, moreover, floating in a large scale. Under the combined effects of dynamic wave, buoyancy, gravity and resistance of bank soil, pipeline presents spatial deformation. A mechanical analysis model is built according to loadings on pipeline and deformation of pipeline. Taking into account nonlinear soil-pipe interaction, axial force, nonlinear material property of pipeline steel and spacial deformation of pipeline, an analytical methodology for evaluating pipeline deformation and stress distribution is developed. Compatibility equation of pipeline physical elongation and geometrical elongation is derived, by which pipeline stress and strain are calculated with iterative method. Based on proposed methodology, a computer program is developed and a series of cases of pipeline in flood are analyzed with it. Compared with finite element analysis, results of proposed methodology are well accepted. Finally, safety assessment method for pipeline in flood is proposed based on limit state theory and the safety of pipeline exposed in mountain torrent are evaluated.

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