Dynamic Response And Reliability Assessment Of Submarine Buried Pipeline Under Earthquake Load

Subsea oil and gas pipeline is the main component of offshore oilfield exploitation and production system,act as the fastest,safest and most economical way to transport large amount of oil and gas continuously,which has been widely used in offshore oilfield exploitation.In the design of submarine pipelines,earthquake is a design factor that must be considered for lifeline engineering.Due to the complexity of seismic factors and seafloor conditions and the limitation of finite element software,the dynamic response of submarine pipelines under earthquake and the reliability of seismic research have not formed a unified understanding.Therefore,it is urgent to explore the practical method that the dynamic response and reliability evaluation of submarine pipelines under seismic action.Based on the large-scale finite element analysis program ABAQUS software,X65 steel is selected as the pipeline steel and Ramberg-Osgood model as the constitutive model,and the non-linear equivalent boundary beam element model of submarine pipeline is established.In the finite element model,the three-dimensional soil spring is used to simulate the pipe-soil interaction and the equivalent boundary spring is used to simulate the boundary condition.The reasonableness of the setting of soil spring and equivalent boundary spring is verified by model self-consistency,and the rationality of the model is verified by comparison with theoretical calculation.The response of submarine pipeline under different pipeline factors,depth and geological conditions are studied by beam element model,and the stress and strain regularity of submarine pipeline under seismic action are summarized.The results show that it is an effective way to improve the anti-seismic ability of submarine pipelines by increasing the pipe diameter and wall thickness and lowering the embedding depth.The pipeline is embedded in the hard soil layer as far as possible.Based on the basic strength theory formula and the allowable compressive strain in the specification,the structural reliability function of pipeline seismic dynamic reliability is established by using the method of dynamic reliability analysis.In view of the empirical formula of seismic damage rate,the failure probability of pipeline under different earthquake intensity is calculated.The research results will be valuable to study the seismic failure mechanism and seismic design of submarine pipelines.