The Mechanics Analysis And Processing Unit Study Of Free Span Submarine Pipeline

Free spanning submarine pipeline is defined as the impending period which not direct contacted between the surface of the submarine pipeline and seabed.Submarine topography geological structure,the scouring action of wave and current,submarine sand waves or dune movement,the change of soil properties,etc,can cause the occurrence of submarine pipeline free span.The emergence of the span changes the load borne by the state and stress of the submarine pipelines,the cyclical vortex-induced vibration is often accompanied,when the water flows through the pipelines.Vortex induced vibration(VIV)is the key to decide to service life of submarine pipeline and lead to the destruction of pipelines.This paper used the theory of potential flow and Morison equation on the analysis of the pipeline span,and described the basic characteristics of vortex-induced vibration.As the research object of free spanning submarine pipeline,the equation of spanning pipe vibration control was deduced,according to the theory of Euler-Bernoulli beam,to solve the natural frequency.Then,the impact of axial force on the free vibration and suspended span length was analyzed.The allowable free span length was derived according to different standards that are the view of state and dynamic state,and its calculation examples were given.Integrating research status of suspended span processing technology domestic and overseas,general scheme for spanning processing unit was designed.Three kinds of schemes of pipeline free spanning process were presented,which included the rock-falls,paving bags and structural supports.The structural support was clear to be the target for this topic research by analysis and research.And the general scheme of main supporting device was provided,including the general mechanical structure and hydraulic control system.The mechanical structure of structural support device in this paper was designed and calculated in details.The strength calibration for the critical components of the device was done by utilizing FEM analysis,and rival claw was analyzed in collision.And the stability of the support device on the ground and seabed was studied through the calculation and simulation.The entire hydraulic control system of support device was designed.According to the synchronizing circuit of swinging double cylinder of support legs,mathematical model was established,and block diagram of control system was deduced too.The synchronizationsimulation of swinging double cylinder of support legs was done by using MATLAB/Simulink software.PID control was introduced to ensure the synchronicity of the hydraulic cylinder.