Study On Vibration Characteristics Of Free Spanning Submarine Pipeline Under The Condition Of Pipe Soil Interaction

As an important part of submarine pipeline, the vibration characteristic analysis of free spanning pipeline is an important content of pipeline research under the action of current. Based on the summary of modeling and vibration characteristic analysis, the calculation model on the basis of pipe-soil interaction is established. Factors such as structure nonlinear, span length, soil characteristics, current velocity, support between adjacent pipelines, coupling effect between Cross-Flow and In-Line are considered comprehensively. Single span and multi span pipeline were studied by numerical simulation method.First of all, according to structural modeling analysis, it pointed out that take0.6times the span length for the boundary pipe-soil contact length can meet the precision and efficiency requirement, simulating boundary pipe-soil interaction on the influence of free span reasonablely.Single span analysis show that initial deformation characteristics of pipeline is greatly influenced by the span length and soil boundary, especially for larger span length and smaller of soil elastic modulus and cohesion. Initial deformation is large compared with diameter for long span, geometric nonlinearity should be considered. Natural frequencies of the pipeline decreases with the increase of span length, increases with the increase of soil stiffness and pipeline buried depth, the influence of initial deformation on frequency should not be neglected, especially for long span and fundamental frequency. Dynamic response of the pipeline change periodically, the deformation and stress change obviously with bigger span length, smaller elastic plastic mechanics parameters and larger current velocity.Multi-span interaction analysis shows that with the increase of cross support length of soil in adjacent span, the interaction strength weakening. The interaction phenomenon more obvious with the adjacent span closer. The larger the cohesion of soil, the stronger restraint of adjacent span.Single span and multi-span analysis pointed out that the location of maximum deformation and maximum stress is not fixed, influenced by many factors. It should be determined according to the specific situation in research. Cross-flow and In-Line coupling analysis show that the dynamic responses of the pipeline increase when considering the coupling effect. The cross section trajectory is affected by pipeline span length and number of suspended span, presenting irregular8for single span and ring set of constantly narrowing8in the In-line for multi span.According to specific environmental conditions, when design and maintenance pipelines we can follow the idea "avoid long span, adopt long support and hard soil bearing for multiple span, to the best of short span, manage and eliminate span timely".