Research On Sinking And Leveling Control Technology Of Multi-bucket Foundation For Offshore Wind Turbine In Sand

With the transformation of energy structure under the goal of“Carbon peak and Carbon neutral,offshore wind energy as a clean energy has undergone a new stage of development,gradually towards deeper sea areas with larger capacity units.Facing the reality of reducing cost to increase benefit with offshore wind energy exploitation under grid parity circumstances,development of offshore wind energy encounters new challenges,which need to be solved through structural and technological innovations.Multi-bucket jacket foundation has the advantages of high bearing capacity,low current load,fast construction speed,and low cost in the installation of far-reaching sea wind power,but facing the risks of seepage failure and buckling while sinking and leveling in sand foundation.In this paper,a series of model tests,theoretical calculations and numerical simulation were carried out based on sinking process of three-bucket jacket foundation.The reasonable suction range and the best leveling strategy of multi-bucket jacket foundation were investigated,and an automatic leveling control system for multi-bucket foundation was developed.The main contents and conclusions are as follows:（1）Considering the effect of subsidence resistance,seepage failure and buckling,the reasonable suction range of multi-bucket foundation sinking in sand was proposed.Firstly,the sinking test of multi-bucket foundation in sand was carried out to explore the sinking characteristics of multi-bucket foundation.The suction value derived from API penetration resistance is used as the lower limit of suction to achieve the penetration of multi-bucket foundation.Secondly,based on the analysis method of formula and test verification,the optimal calculation method and the value range of permeability coefficient k_fc in sand of multi-bucket foundation were recommended after comparison from the mechanism of seepage failure at different depths of multi-bucket foundation.Finally,combined with the standard algorithm and numerical simulation,the critical suction calculation method suitable for buckling of multi-bucket foundation was recommended after comparation.（2）Leveling tests of multi-bucket foundation were carried out based on multiple control standards such as seepage failure,buckling and tilt angle.The performances of levelling strategies based on“flow rate control”,“valve control”and“micro jacking and re-sinking control”separately were investigated.Various control indexes and optimal control strategy in the process of sinking of multi-bucket foundation in sand were proposed.（3）The theoretical framework of multi-bucket foundation sinking and leveling control based on pump valve and pipeline system was constructed,and operation and principle of the control system were clarified.The automatic sinking and leveling control and pipeline system of multi-bucket foundation based on multiple control indexes in the perspective of seepage failure,buckling and leveling angle were developed,and the feasibility of the system was verified through tests.