Dynamic Response Analysis Of Collision Damage Process In Shallow Sea Gas Pipelines

With the development of offshore oil and gas,the submarine pipelines have been used more and more widely.Compared to the onshore pipelines,it is more difficult to repair for submarine pipelines in the event of an accident.As an important part of the submarine oil and gas pipelines,the neritic gas pipelines are mainly laid in the coastal waters where there are many fishing grounds and channels.It is probably that the pipelines are damaged by the collision of dropped objects from third party activities.In order to seek reasonable protection measures to ensure the safe operation of the pipelines,it is necessary to analyze the dynamic response of the pipelines caused by dropped objects.Firstly,researches are analyzed and summarized,which are about structural damage caused by collision damage of the dropped objects.The dynamic response is analyzed by the simplified analytical method and numerical simulation method.The impact force of dropped objects is calculated by non-perfect elastic collision theory and momentum conservation law.According to the transmission analysis of impact load in the soil and concrete layer,the internal force is calculated.Then the failure judgment of the neritic gas pipeline is carried out.According to simplified analytical method,the dynamic response of the neritic gas pipeline is analyzed.Considering the special structure of the neritic gas pipeline and the nonlinear factors of geometric nonlinearity,material nonlinearity and nonlinear contact in the process of collision damage,Workbench LS-DYNA software is used to simulate the dynamic response process of pipeline under the dropped objects collision.A nonlinear damage analysis model for the neritic gas pipeline is established.According to the time curves obtained by simulation,the dynamic response law of the dropped objects collision damage in the neritic gas pipeline is revealed.Based on the analysis results from numerical analysis method,the collision damage influence on pipelines is discussed about impact energy(velocity and mass),wall thickness,steel grade,the internal pressure,dropped objects shape,the buried depth and the thickness of concrete protective layer.The effectiveness of the protective measures is compared with the influence on the dent depth of different factors.Multi factor sensitivity analysis is carried out by orthogonal test and the critical values of the major factors are analyzed.Finally,combining the conclusions of the numerical simulation analysis and the theory of structural reliability analysis,the application of the dynamic response analysis in the reliability analysis is discussed.Based on the reliability analysis of a neritic gas pipeline,the corresponding protective measures are put forward to provide theoretical basis for solving the practical engineering problems such as damaged pipeline safety assessment.