Study On Installation And Removal Of Tripod-bucket Jacket Foundation For Offshore Wind Turbines

With the proposal of " action plan for peaking carbon dioxide emissions " and "action plan for carbon neutral ",and the parity of offshore wind in China.At present,the suction foundation is in the ascendant,it is more and more favored by developers,which has the advantages of low cost,simple construction and eco-friendly.As an engineering entity,its realization is inseparable from the construction process.Aiming at the construction technologies of penetration,removal and tilt adjusting,this manuscript is based on the model test method to explore the regular pattern.However,penetration/removal and tilt adjusting are carried out simultaneously.The foundation holder restricts the tripod-bucket jacket foundation to have only vertical degrees of freedom,which can strip the operation of tilt adjusting.In this way,pure penetration and removal can be studied.The water pressure sensor is embedded in the soil to record the seepage changes in the soil.In the penetration test,the same negative pressure loading system is adopted,and the penetration rhythm is controlled by changing the initial applied pump pressure.The test results show that the initial applied pump pressure has an appropriate value.In the removal test,the removal rhythm is controlled by changing the injection medium(air /water)and water injection volume.The test results show that the topographic change by water injection is greater than that by gas injection,and the removal speed is positively correlated with the water injection flow.For the tilt adjusting,this study controls the suction/ positive pressure application,manufacture three penetration/removal extreme tilt modes,in turn,it is named single bucket high mode,single bucket low mode,three buckets all slanting mode.The purpose of making above modes is to find the allowable angle(corresponding to soil failure)and maximum limit angle at different depths.The test results show that there is a positive correlation between the maximum limit angle and depth under penetration,and a negative correlation between the maximum limit angle and depth under recovery condition.Research the tilt adjusting based on the maximum limit angle,to restore the angle which accords within the standard.The elements of the tilt adjusting are the applied medium(water/air),the applied method(extraction/injection),and the applied position(which bucket).For the process of penetration,methods are chosen as following: pump water from high-level bucket;inject water to low-level bucket;pump water from high-level bucket & inject water to low-level bucket;inject air to low-level bucket.For the process of removal,methods are chosen as following: inject water to low-level bucket;inject water to low-level bucket & exhaust air from high-level bucket,the former enables the angle to be roughly adjusted,and the latter enables the angle to be finely adjusted.