Seismic Response Analysis And Experimental Study Of Oil And Gas Pipelines In Inhomogeneous Soil

Buried oil and gas pipelines are crucial infrastructure for underground lifelines,and their safety and reliability are important guarantees for national economic development.These pipelines have characteristics such as long working routes and complex site conditions,and the soil properties of different site sections in inhomogeneous soil may be inconsistent.The propagation path and energy distribution of seismic waves are more complex,leading to different seismic responses of oil and gas pipelines at different circumferential soil media,exacerbating the vibration response of pipelines under seismic action.This study focuses on the seismic safety of buried oil and gas pipelines in inhomogeneous soil and investigates the dynamic interaction between buried oil and gas pipelines and the inhomogeneous soil surrounding them.A method for setting the interface element and truncating the boundary condition of the soil model in inhomogeneous soil is proposed,and a finite element model suitable for seismic response analysis of buried oil and gas pipelines in inhomogeneous soil is established.Time history analysis and spectrum analysis were performed on the seismic response of buried oil and gas pipelines in inhomogeneous soil,and the seismic response characteristics and laws of buried oil and gas pipelines and the surrounding soil under consistent/inconsistent seismic excitation were studied.A continuous layered shear test model soil box suitable for seismic response testing of buried oil and gas pipelines in inhomogeneous soil was designed and manufactured.The seismic response variation of pipes and different soils under various working conditions was explored,and the difference in seismic response between homogeneous and inhomogeneous soil buried pipelines in shake table tests was compared and analyzed.The research results show that the proposed nonlinear contact analysis method can better simulate the characteristics of the pipe-soil contact surface and dynamic interaction in inhomogeneous soil.The simulation of the continuity boundary condition of the soil body can be effectively realized by setting the spring stiffness and damper coefficient.The established pipe-soil finite element model can well simulate and analyze the seismic response of buried oil and gas pipelines in inhomogeneous soil.With the increase in loading level,the acceleration peak value of the pipeline under consistent/inconsistent excitation shows differences.Under inconsistent excitation,the acceleration response curve appears multi-peak phenomenon,and the acceleration response of oil and gas pipelines is more significant,and the stress in the middle of the pipeline increases,leading to more severe damage to the pipeline.Under consistent/inconsistent excitation,the displacement and acceleration of inhomogeneous soil increase with the increasing loading level,and the earthquake response of red soil on the left side is slightly larger than that of yellow soil on the right side.The earthquake response magnitude of soil is closely related to its properties,and the impact of inconsistent excitation on inhomogeneous soil is greater.Soil movement is more violent,and soil damage is more severe.The characteristics and laws of seismic response of pipelines and surrounding soil in shake table tests are consistent with the results of finite element model analysis.Compared with the seismic response of pipelines in homogeneous soil,the strain peak value and acceleration peak value of pipelines in inhomogeneous soil are larger,and the seismic response of buried oil and gas pipelines in inhomogeneous soil is more pronounced,with more violent pipeline motion.