Research On The Damage Mechanism Of Gravel Protection Structure Against Anchor Damage To Submarine Pipelines

The rapid development of maritime shipping and fishing has led to the fact that parts of submarine pipelines connecting land areas often cross channel and fishing areas.The anchoring operation of ships in the channel will cause the submarine pipeline to be accidentally hit or hooked by the anchor,causing damage or even failure of the submarine pipeline,which will cause major harm to the safety of oil and gas production and the ecological environment.At present,gravel protection structures are widely used to protect cross-channel submarine pipelines,but there is a lack of accurate and effective design evaluation methods,which often increases construction technical risks and cost investment due to excessive protection.In this thesis,aiming at the anchor damage resistance of submarine pipelines in the cross-channel area under the gravel protection structures,the method of combining model test and numerical simulation is used to carry out the research on the damage mechanism of the submarine pipeline under the gravel protection structure by dropping and dragging anchors.Based on the self-designed test platform,the actual submarine pipeline gravel protection scheme was restored by setting up the gravel layered protection structure,and the anchor drop and drag anchor model tests were carried out respectively.The data were analyzed in detail.Using the smooth particle hydrodynamics-finite element coupling(SPH-FEM)algorithm and the coupled Euler-Lagrangian(CEL)algorithm,the numerical simulations of the anchor dropping and dragging processes were carried out based on the finite element software ABAQUS.The accuracy of the numerical model established in this research is verified by model test data.On this basis,the numerical models of drop anchors and drag anchors under prototype conditions were established,and the load capacity of the gravel protection structure against dropping anchors and dragging anchors was comprehensively evaluated.Through model tests and numerical simulation studies,the influence characteristics of drop anchors and drag anchors on submarine pipelines under the gravel protection structure were mastered,and the influence rules of gravel protection structures on the anchor penetration depth and the dragging trajectory of the anchor were obtained.The research results provide theoretical basis and evaluation guidance for the design of gravel protection layer for submarine pipelines in practical engineering.