| With the development of offshore wind power,wind turbines are developing into deep sea areas,and their basic forms gradually are facing to upgrade and update.In the traditional wind power foundation,monopile foundation is the most commonly used form,but facing the complex marine environment,it can no longer meet the demand of bearing capacity,while composite pile foundation is widely concerned because of its better bearing capacity.Monopile-friction wheel foundation is a new type of composite pile foundation,which is an upgrade of monopile foundation and has better bearing performance.Therefore,it is of great significance to perfect the calculation theory and practical application of monopile-friction wheel foundation to study the bearing capacity of monopile-friction wheel foundation and clarify its mechanical deformation mechanism.Taking a wind farm in a sea area of East China Sea as an example,ABAQUS finite element simulation software was used to establish a numerical calculation model of monopile-friction wheel foundation in sandy soil,and then the bearing characteristics of monopile-friction wheel foundation were analyzed.Firstly,the superiority of bearing capacity of monopile-friction wheel foundation was compared with that of monopile foundation.Secondly,the bearing capacity of offshore composite pile foundation under single horizontal,single vertical and combined loads and the change of bearing capacity of composite pile under different influencing factors were studied.Finally,the bearing capacity of composite pile foundation under combined load was studied,and the influence of pile foundation bearing capacity,horizontal load and vertical load under different load angles was analyzed.The conclusions are as follows:(1)Compared with traditional monopile foundation,the bearing capacity of monopile-friction wheel foundation was improved to some extent due to the existence of friction wheel.(2)In the analysis of factors affecting the horizontal bearing capacity of monopile-friction wheel foundation,the principle of the influence caused by changing the height of friction wheel was similar to that caused by changing the diameter of friction wheel.Both increased the pile-soil action area.With the increase of the diameter of friction wheel and the height of friction wheel,the horizontal bearing capacity of pile foundation increased,but the increase amplitude decreased.Changed the thickness of friction wheel did not change the size of pile foundation and the area of pile-soil interaction,so it had little influence on the bearing capacity of pile foundation.However,decreased the thickness of friction wheel reduced the rigidity of friction wheel and the horizontal bearing capacity of composite pile.(3)In the analysis of factors affected the horizontal bearing capacity of monopile-friction wheel foundation,the principle of the influence caused by changing the height of friction wheel was similar to that caused by changing the diameter of friction wheel.Both increased the pile-soil action area.With the increase of the diameter of friction wheel and the height of friction wheel,the horizontal bearing capacity of pile foundation increased,but the increase amplitude decreased.Changed the thickness of friction wheel did not change the size of pile foundation and the area of pile-soil interaction,so it had little influence on the bearing capacity of pile foundation.However,decreased the thickness of friction wheel reduced the rigidity of friction wheel and the horizontal bearing capacity of composite pile.(4)The envelope surface of bearing capacity of monopile-friction wheel foundation is consistent with the envelope surface of theoretical value of pile foundation.The critical angle is when the inclination angle is 10.When the inclination angle of load is less than 10,the bearing characteristic is mainly vertical load capacity.When the inclination angle of load is greater than 10,the bearing characteristic is mainly horizontal load capacity.(5)Due to the existence of horizontal load,the pile body of monopile-friction wheel foundation was flexurally deformed,and part of the vertical load was borne by the pile foundation itself,so the vertical displacement at the top of the pile was reduced,at the same time,the pile body would generate bending moment,changed the stress characteristics of the pile body.Therefore,although the vertical displacement of the pile body was reduced,the horizontal load adversely affected the vertical bearing capacity.(6)In the presence of vertical load,the lateral displacement of monopile-friction wheel foundation under horizontal load gradually decreases,and with the increase of vertical load,its decreasing trend becomes slower,while the shear force and bending moment of pile body have no obvious change.That is,the existence of vertical load can effectively reduce the lateral displacement of the pile and has no adverse effect on its mechanical deformation characteristics.The existence of vertical load has a certain promotion effect on the horizontal bearing capacity of single pile-friction wheel foundation.(7)With the increase of the load inclination angle,the displacement of the pile side gradually increased.The zero point of the displacement of the pile body was within the range of 3.6D-4.6D,and the bending moment of the pile body also gradually increased.The maximum bending moment displacement was within the range of 0.6D-1.6D,in which the horizontal displacement and the bending moment of the pile body were mainly affected by the horizontal component.With the increase of the load inclination angle,due to the strong squeezing effect of pile and soil in the passive area,the soil resistance also increased gradually.The pile and soil in the active area were gradually released,and the soil resistance in the upper part decreased gradually,partially to zero.The larger the load inclination angle,the deeper the range of the soil resistance to zero,and the upper part of the pile side friction pile increased gradually and the lower part decreased gradually. |
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