Study On The Damage Of Submarine Pipeline Impacted By Falling Objects

The submarine pipeline is an important part of the connection between offshore oil exploration equipment and onshore oil industry system.Once the pipeline is damaged,it is very likely to cause serious ecological disasters and property losses.In marine engineering,maritime activities are frequent,and cargo may be dropped during crane loading and cargo transportation,especially for the crane on the platform.Anchoring and falling objects are important factor which led irreversible damage of pipelines,threatening the safety of submarine pipelines.Therefore,it is still a key scientific issue for analyzing the pipeline damage mechanism and the dynamic mechanical response of falling objects,pipelines and seabed systems.Therefore,this paper carries out numerical analysis of impact damage of submarine pipelines from both sea falling objects and seabed.The geometric nonlinearity,material nonlinearity and contact form of the pipeline and soil involved in the impact problem are considered in the simulation process.The Abaqus/Explicit module of finite element calculation software was used to study the three-dimensional impact system model of the interaction between falling objects,submarine pipelines and seabed.The correctness of the model was verified by comparison with existing experiments and DNV specifications.The numerical model was used to analyze the influence of falling object shape,velocity,mass and energy,seabed stiffness,undrained shear strength and pipeline embedding depth on pipeline damage.The following research conclusions were obtained:(1)When the seabed is regarded as a rigid bed,there is a one-to-one nonlinear relationship between different shapes of falling object energy and pipeline damage,which means the kinetic energy of the falling object determines the pipeline damage,and has nothing to do with the single factor of mass and speed of the falling object.For the flexible soil seabed supports the pipeline,not only the kinetic energy of the falling object affects the pipeline damage,but also the quality and speed of the falling object will also affect the damage of the pipeline.(2)The shape of the falling object has an influence on the pipeline damage.When the falling object energy and mass are the same,the damage caused by the ball falling object impacts the pipe is the largest,the wedge shape is second,and the square body is the smallest.(3)When the same falling object impacts the pipeline,as the buried depth of the pipeline increases from 0 to 1D,the damage gradually increases.When the buried depth exceeds 1D,the buried depth is increased,and the pipeline damage is reduced.(4)The undrained shear strength of the seabed soil has a great influence on the damage of the falling impact pipe,and the influence of the seabed elastic modulus is weak.