Vibration Characteristics Of Subsea Multi-Span Pipe Considering Pipe-Soil Interaction

Due to irregular seabed,current scouring or artificial construction,there inevitably occur some free spans along subsea pipelines.Compared with isolated single span,multi span pipeline is more common.With finite element method,this article focuses on studying vibration characteristics of multi-span pipe considering pipe-soil interaction,the main research content includes the following several aspects:(1)The research methods are discussed,including empirical calculate methods for pipe-soil interaction,analytic method and semi-analytic method of free span vibration research,methods of calculating vibration characteristics of span in the standards.(2)Basing on the theory and experience methods,three dimensional numerical models are built for multi-span pipe-soil interaction with ABAQUS software.Contact lengths between pipe and soil at the ends are mainly studied,in order to get the correct curves of pipe-soil interaction at the ends and middle of pipe-soil contacting region.Besides that,sensitivity analysis is made to the soil cohesive force,Young's modulus and soil density.(3)To calculate vibration characteristics,numerical models for single span are made,and verified them by comparing with calculating results of standards.In addition,discussions about impact factors,including boundary conditions,span length,axial force and corrosion,are carried out.(4)Vibration characteristics of multi-span pipe are studied by building numerical models on the base of single span models and pipe-soil interaction.This part puts emphasis on discussing the influence of pipe-soil contacting length in the middle and adjacent span length on the vibration characteristics of main span.Results of the research are significant for engineering application.In this paper,three dimensional models for continuous multi-span pipe are closer to the real condition than two-dimension or single span models,and it is certain innovative that consider axial force and static deflection when analyze vibration characteristics of multi-span pipe.