Analysis Of Mechanical Characteristics Of Submarine Suspension Pipelines And Research On Treatment Measures

Compared with onshore pipelines,submarine pipelines work in poor environment,have greater operational risks and higher failure probability,and are prone to occur failure accidents.Once occur the failure of an accident,it will result in a huge loss of human,material and financial resources.When a free span of submarine pipeline appears,the load on the pipeline is increased,so the pipeline is easily subjected to damage.Submarine pipelines now in service have many spans,which seriously affect the safe operation of pipelines.Therefore,the analysis of the mechanical properties and treatment measures of free spanning submarine pipeline will have important guiding significance for the design,construction and maintenance of submarine pipelines in China.The main research contents and achievements are as follows:(1)This paper investigated the research status of the mechanical behavior of free spanning submarine pipelines at home and abroad,summarized the achievements and existing problems in the theoretical analysis method,numerical simulation method and experimental research,and summarized the common protective measures for free spanning submarine pipelines.(2)Conducted on the free spanning submarine pipeline,analyzed the force characteristics of the pipeline based on non-linear theory and basic theories of fluid mechanics,summed up the damage mechanism and failure type of the pipeline,and analyzed the possible influencing factors of pipeline damaging.(3)Taking the free spanning submarine pipeline as the research object,the finite element model for the inherent characteristics analysis of free spanning submarine pipeline was established using ANSYS software.The intrinsic characteristics of free spanning submarine pipeline were analyzed,and the effects of the current velocity,free spanning length of pipe,pipe diameter and wall thickness,concrete weight layer thickness,soil elastic modulus and other factors on the inherent characteristics of free spanning submarine pipeline were calculated and analyzed.Based on the simulation results,the correlation analysis of the factors was performed.(4)Taking the free spanning submarine pipeline under the action of the ocean current as the research object.Based on the finite element model of the inherent characteristics analysis,considering the influence of nonlinearity,the finite element model for the mechanical response analysis of free spanning submarine pipeline coupled with pipe and soil was established.Simulated the mechanical response behavior based on pipe and soil coupling,and calculated and analyzed the influences of the current velocity,pipeline internal pressure,elastic modulus of the soil,free span length of the pipeline,pipe material,pipe diameter and wall thickness,and concrete weight layer thickness on the mechanical properties of free spanning submarine pipeline.(5)Analyzed the deficiencies of the stress calculation formula of free spanning submarine pipeline in standard SY/T 7056.Based on the influence rules of pipeline parameters,soil parameters and internal and external flow parameters of pipe on the mechanical response of free spanning submarine pipeline,the calculation formula for the stress of free spanning submarine pipeline was obtained by the multiple regression theory.(6)Established the multi-span submarine pipeline finite element model.The influences of multi-span factors such as the length of supporting soil between two spans,the ratio of adjacent spans,and the characteristics of supporting soil between two spans on the intrinsic characteristics and the mechanical response of the pipeline were studied.The results were compared with the simulation results of the single-span submarine pipeline.(7)The governance process of spanning submarine pipeline was proposed.From the perspective of the application of external forces and the principle of downflow and sedimentation,based on the relevant rules of fite element simulation,this paper summarized the relevant governance measures for spanning submarine pipeline,and proposed vortex-induced vibration suppression method to treatment spanning submarine pipeline.