Research On Design Of Pile Plug For Offshore Wind Turbine Steel Pile And Its Key Mechanical Problems

The offshore wind turbine steel pile foundation is the most commonly used foundation form in offshore wind farm construction.The traditional transportation method of steel piles is barge transportation.Floating towing transportation has been studied and applied in the transportation of various marine structures.The floating towing transportation of the offshore wind turbine steel pile needs to realize the sealing of the two ends of the steel pile through the pile plugs,so that the steel pile can float on the sea surface.The pile plug used for the floating dragging of offshore wind turbine steel piles has been researched and applied abroad,but the technology is still in a blank state in China.In order to realize the floating towing transportation of offshore wind turbine steel piles and reduce the cost during the construction of offshore wind farms,the pile plug is independently designed and studied.On the basis of clarifying the relevant parameters of the offshore wind turbine steel pile and the design requirements of the pile plug,three conceptual design schemes including Radial compression sealing,Axial compression sealing,and Axial compression,radial sealing are proposed and compared.Finally,the concept design of Axial compression,radial sealing is adopted.The overall scheme design of the pile plug is proposed.Under the condition of meeting the design requirements,the overall structure and sealing system are preliminary designed.And the monitoring system scheme is proposedBased on the nonlinear theory of contact analysis and the superelastic theory of rubber materials,the performance of the rubber sealing ring of the pile plug is analyzed.Build a finite element simulation analysis model of the rubber sealing ring of the pile plug in Abaqus.Based on the control variable method,the effects of material hardness,contact surface friction factor,compression rate and contact surface ovality on the performance of the rubber sealing ring is studied;Based on the orthogonal test method,the influence of the geometric parameters of the cross-section on the rubber sealing ring is studied.The results show that: The increase of material hardness and compression rate will improve the sealing performance of the rubber seal ring.And the increase of the friction factor of the contact surface will not improve the sealing performance of the rubber seal ring;The order of the influence of the geometric parameters of the cross-section on the performance of the rubber sealing ring of the pile plug is: width of D-shaped section(thickness of rubber sealing ring),contact surface ovality,and length of Dshaped section.The force of the pile plug is analyzed.The strength of the main structure of the pile is analyzed by finite element simulation.And the rigidity of the metal washer is analyzed by theoretical calculation and finite element simulation.The preliminary design related parameters meet the requirements of the strength of the main structure and the rigidity of the metal washer.The main structure is optimized in structural form.And the optimized design reduces the quality of the pile plug.Related problems in the engineering application of pile plug are studied.And the specific processes of the pile plug application are described,including the installation of the pile plug,the towing and straightening of the steel pile,the disassembly and recovery process of the pile plug.The towing resistance during the towing of the steel pile is analyzed and estimated.The towing resistance of the steel pile is far less than the maximum static friction between the rubber sealing ring of the plug and the inner wall of the steel pile.The influencing factors of the steel pile towing process is analyzed.Considering the safety of the pile plug application,the lower towing speed,the minimum towline length within the allowable range of the relevant specifications,and the minimum immersion depth that the steel pile can reach should be selected.