Analysis Of Free Span And Treatment For Subsea Pipeline Based On The Pipe-Soil Coupling

At present,submarine pipelines serving in Zhoushan show different degrees of suspension,which seriously affects the production progress at sea.Therefore,the analysis of the mechanical properties,allowable length and treatment measures of free spanning pipelines will have practical value for the application of the pipeline engineering.In this paper,the submarine gas pipe is taking as the research object,and the numerical simulation is carried out based on the theory of pipe-soil coupling and finite element analysis method.Firstly,taking the pipe-soil interaction as the research focus,the ABAQUS software is used to establish the pipe-soil coupling model under two dimensions,and the displacement penetration method is used to analyze the sensitivity of different soil parameters on the force-displacement curves,which shows the variation law of soil stiffness.Secondly,the horizontal and vertical forces are obtained by the Java language programming.Based on this,the axial characteristics of the pipelines are analyzed,and the effects of different span lengths,diameter-thickness ratios,internal pressure values and current velocities on the stress of the pipeline are simulated.Then,the dynamic analysis interface of static intensity and vortex-induced vibration method is programmed by Java language,and the fatigue analysis is carried out by dynamic software OrcaFlex,above which verify the allowable length of the free spanning pipelines from three different perspectives.After that,the dynamic effects of the corresponding parameter conditions on the stress and displacement of single and double spans are analyzed.Finally,the research on the suspension treatment of the actual sea conditions in Zhoushan is carried out,and the support structure of the steel frame is optimized,obtaining a reasonable structural size.Simultaneously,the numerical simulation study on the sandbag coverage scheme shows that the sandbag coverage is more economical,but the stability is poor when the flow velocity is large.When the sandbags are stacked into a rectangle,the treatment effect is slightly better than the trapezoid,but the economy of trapezoid is better.