Stress Analysis Of Ma Huining Crossing Pipeline Under The Influence Of The Flood

The oil and gas pipeline network of China crosses a wide region,including rivers,lakes and other hydrological areas inevitably.If the underwater crossing pipeline encounters flood,it will probably explode,suspended and then break,which is a huge threat for the safety operation of the pipeline.This thesis aims to study the stress analysis of the pipeline under the influence of flood,based on Ma Huining pipeline which frequently encounters flood.Firstly,based on the hydrological conditions along the pipeline,the causes and the levels of flood are analyzed.Then according to the theory of Elastic Foundation Beam based on Winkler's Hypothesis,the simplified mechanics model of the pipeline is established.The Morison equation is chosen to calculate the force of the flood on the pipeline.Analytical method is used for stress analysis,and the ineffectiveness of the pipeline is judged based on the strain criteria.According to the above theoretical analysis,a set of auxiliary programs for the calculation of the force of flood on the pipeline is developed.In order to further analyze the features of the strain of the pipeline under the influence of flood,the finite element software ABAQUS is chosen to simulate real conditions.According to the result of the static force analysis,the distribution of the stress and strain of the pipeline is obtained,and the concentrated area of them is determined.Thus the maximum length and the maximum velocity are obtained,and the relationship between them is discussed.By the analysis of influencing factors,including the sediment concentration of flood,pipeline's pressure,and the diameter-thickness ratio of pipeline,the impact of these parameters are determined.In the dynamic analysis of the pipeline,the pipeline's natural frequency in different suspended length is obtained by Modal analysis.It is judged whether or not vortex-induced vibration will occur,obtaining the dangerous length.Furthermore,considering the flow rate of flood changes over time,the typical fast-moving flood is chosen,the time-history analysis is carried out based on the implicit dynamic analysis method.The results of the dynamic analysis are compared with the static analysis.Finally,based on the above conclusions,putting forward the measures to reduce the stress of the pipeline and improve the pipelines against the flood such as hydraulic protection,casing reinforcement,strain detection,piling reinforcement and so on.The research methods and achievements could provide suggestions for the flood protection and safety operation of Ma Huining pipeline,and also reference for the further study of the crossing pipeline under the influence of the flood.