Finite Element Analysis Of Bearing Capacity Of The Suction Bucket-helical Anchor Combined Foundation In Saturated Clay

Offshore wind turbines have the advantages of not occupying land,not disturbing people,and high single unit capacity.It has been gradually promoted in China.Due to the randomness of wind and wave load,offshore wind foundation needs to have better ability of resisting pull-out and horizontal load.The helical anchor foundation and the suction bucket foundation are common offshore wind foundations.The helical anchor foundation has good pull-out resistance,but its ability to resist horizontal load is poor.The suction bucket foundation relies on the friction to provide pull-out resistance.Sometimes the suction bucket foundation resist the pull-out load is weak,but the ability to resist horizontal load is strong.This paper proposes a new type of foundation structure,which is composed of the helical anchor foundation and the suction bucket foundation.It has certain significance for the development of offshore wind engineering in China to give full play to the bearing advantages of the helical anchor foundation and the suction bucket foundation.In this paper,the three-dimensional finite element models of the interaction between the combined foundation,the helical anchor foundation and the suction bucket foundation and soil are established on ABAQUS software.By applying displacement load on three kinds of foundation,the ultimate bearing capacity of foundation under the combined load of normal displacement,tangential displacement and moment is obtained,and the correctness of the model is verified.The envelope surface of bearing capacity coefficient of the combined foundation,the helical anchor foundation and the suction bucket foundation is fitted.The factors affecting the bearing performance of the combined foundation are analyzed.The specific research contents of this paper are as follows:1)The finite element model of interaction between the helical anchor foundation and soil,the suction bucket foundation and soil is established.By applying normal displacement and tangential displacement to the helical anchor foundation and the suction bucket foundation respectively,the ultimate bearing capacity coefficient is obtained,which is compared with the analytical solution to verify the correctness of the model.On this basis,a new finite element model of interaction between foundation and soil is established.2)By applying normal displacement,tangential displacement and X-axis rotation angle to the combined foundation,the helical anchor foundation and the suction bucket foundation respectively,the ultimate bearing capacity of different foundations under load is obtained.The results show that the maximum normal,tangential and moment ultimate bearing capacity of the combined foundation is greater than the helical anchor foundation and the suction bucket foundation.The envelope surface of the ultimate bearing coefficient of the three foundations is obtained by applying the combined load to the three foundations.3)The modulus of elasticity of soil will not affect the ultimate bearing capacity coefficient of the helical anchor foundation,the suction bucket foundation and the combined foundation.However,with the increase of elastic modulus,the displacement needed to be applied to reach the ultimate bearing capacity is decreased;with the increase of undrained shear strength of soil,the maximum normal,tangential and moment ultimate bearing capacity of the three foundations are significantly improved.4)The length diameter ratio will affect the bearing capacity of the suction bucket foundation.With the increase of the length diameter ratio,the normal,tangential and moment ultimate bearing capacity of the suction bucket foundation are significantly improved.5)With the increase of the diameter of the anchor plate,the maximum normal ultimate bearing capacity,the maximum tangential ultimate bearing capacity and the maximum moment ultimate bearing capacity of the helical anchor foundation are significantly improved,and the displacement required to reach the ultimate bearing capacity is increasing.