Risk Assessment On Instability And Soil Liquefaction For Submarine Pipeline

With the rapid development of China's economy,the demand for oil and gas r esources is increasing rapidly,and our country gradually pay attention to the development and utilization of offshore oil and gas resources.Submarine pipeline is the most important approach for the transportation of offshore oil and gas resources,and submarine pipeline is in a complex ocean environment for a long time,these complex environmental loads will destroy the stability of submarine pipeline,causing the submarine pipeline occurred in horizontal or vertical displacement,even lead to pipeline rupture seriously.Therefore,it is necessary to assess the stability of the submarine pipeline,which can ensure the safe operation of the submarine pipeline,and avoid the significant economic loss and environmental pollution caused by the failure of the pipeline.This dissertation mainly focuses on study on the instability risk analysis of submarine pipeline and liquefaction risk,which is a part of the central academy basic research operating expenses special funding supported projects “Methods Studying on Unstable State Evaluation of Submarine Pipelines Under Complicated Conditions”.The following is main research outcome of this paper.(1)Risk assessment of submarine pipeline instabilityThe paper identify the instability risk factors of submarine pipeline,and establish a fish bone figure of submarine pipeline instability,and identify the deep reasons for instability risk of submarine pipeline on the basis of this.The paper establish instability accident cause evaluation index system of submarine pipeline,for providing the basic for submarine pipeline instability risk assessment.developed a suit of pipeline instability risk assessment process.(2)Study on the liquefaction risk of the submarine pipeline seabed soilThe paper analyzed the mechanism of wave induced liquefaction of seabed soil and the method to study the liquefaction of seabed soil so far.Then,the paper summarized three methods of judging the liquefaction of the similar seismic discrimination method.Using the reliability theory and first order second moment,a seabed soil liquefaction probability calculation model is proposed,and to study the relationship between the safety factor and liquefaction probability and reliability index;the paper analysis the coefficients of variation of parameters and correlation on the reliability sensitivity.(3)In the state detection data analysis and safety assessment of submarine pipeline.The paper study the in the state detection date of a submarine pipeline,and get the rules of submarine pipeline of lateral displacement change and vertical displacement change,and it provides basic for establishing the finite element model of submarine pipeline applied suitable displacement load,to make the analysis of finite element model closer to the actual project.Using ANSYS finite element software to establish the bare submarine pipeline and buried submarine pipeline model,and study the two states of submarine pipeline on the instability of the process;The paper safe evaluate the bare submarine pipeline in unstable state under the limit state safety,and study the effects of four factors of submarine pipeline in unstable state quantitatively.(4)Study on instability risk control method of submarine pipelineListed a variety of stability method on submarine pipeline what are widespread used at home and abroad,and comparative the advantages and disadvantages and applications of various measures.The paper establish a subrmarine pipeline instability risk control hierarchical model of optimization slection based on analytic hierarchy process.