Stability Analysis Of Submarine Pipeline Under The Impact Of Trawl Gear

The rapid growth in energy demand has driven the rapid development of subsea pipeline projects around the world.Submarine pipelines play a key role in the production and transportation of oil gas.Submarine pipelines will often pass through the fishing grounds,the undersea trawl equipment,in the event of an impact and drag on the subsea pipeline,can also cause gripping in special circumstances,increasing the risk of damaging the submarine pipeline and seriously endangering the safe production of the sea.Although the relevant standards of the DNV give the empirical formula of the interaction between the trawl and the pipeline,some practical factors are neglected and the calculation results are very conservative,resulting in wasteful design.Therefore,it is necessary to analyze the response of the pipeline after impact,and to establish a more realistic evaluation model to provide a reference for the risk assessment,engineering design and disaster prevention of submarine pipelines.In this paper,the basic knowledge of trawl gear and the computational theory of collision response are introduced,which lays the foundation for the numerical simulation analysis.The impact of the seabed and concrete weighting layers on the impact is not taken into account in the relevant standards of DNV.Therefore,the mechanical behavior of geometric nonlinearity,material nonlinearity and contact interface nonlinear is considered in the numerical simulation,and the damage behavior of the submarine pipeline is further studied by ABAQUS,a finite element structural analysis program.The finite element software ABAQUS was used to establish the numerical model of trawl board-subsea pipeline-seabed.The coupling effect of pipe and soil and the protective action of concrete layer were considered in the model,and the empirical formula was compared with the numerical results for verifying the rationality.Based on the model,the time history of the collision process between trawl and submarine pipeline is analyzed for summarizing the variation rule of the submarine pipeline.The basic model was compared with the trawl board-subsea pipeline model and the trawl board-bare pipeline-seabed model respectively so that analyze the damage characteristics of the submarine pipeline by concrete weighting layer and seabed.In this paper,the main sensitivity factors are determined by single sensitive analysis method,combined with the empirical formula of DNV-RP-F111 and the results of finite element model.The results include trawl board quality and velocity,pipe thickness and diameter.By adjusting the basic model,the influence of the sensitivity factors is analyzed so as to accurately predict the damage law of the submarine pipeline after the impact for facilitating the engineering design and extending the service life of submarine pipeline.