单向循环荷载作用下开口管桩动力响应数值模拟

Numerical simulation of dynamic response of open pipe pile under unidirectional cyclic load

海上风力发电机的基础承受着结构自重及风、波浪、水流等多种循环荷载,而风力发电机组运行对基础的承载力和变形有严格要求.针对近海风机开口管桩单桩基础,通过PFC2D数值模拟研究了水平单向循环荷载对单桩基础受力变形的影响.结果表明:水平单向循环荷载作用下,桩顶累积位移随着循环荷载谷值与峰值的比值ζc的增大前期增加速率较快,而后期较慢,但并未改变桩体转动中心的位置,约为0.85倍的桩体埋深;ζc值越大,桩基初期卸载刚度越大,但稳定后卸载刚度的终值相近,约为6.70 kN/mm;随ζc值的增大,桩顶主动区局部土体扰动程度增大,但影响范围大致相同,严重扰动区为2~3倍桩径;桩侧摩阻力降低幅度随ζc值增加而增大,且前期侧摩阻力降低速率增加,后期侧摩阻力均趋于稳定状态.

The foundation of the offshore wind turbine bears structural self-weight and many cyclic loads such as wind,wave and water flow,while the operation of wind turbines has strict requirements on the bearing capacity and deformation of the foundation.Aiming at the single pile foundation of offshore wind turbine open pipe pile,PFC2D numerical simulation was carried out to study the influence of horizontal unidirectional cyclic load on the deformation of single pile foundation.The results show that,under the horizontal unidirectional cyclic load,the cumulative displacement of pile top increases rapidly in the early stage with the increase ofζc,the valley-to-peak ratio of cyclic load,but decreases in the later stage.However,the position of the rotating center of pile body is not changed,which is about 0.85 times of the buried depth of pile body.The larger the value ofζc is,the greater the unloading stiffness of pile foundation at the initial stage will be,but the final value of unloading stiffness after stabilization is similar,which is about 6.70 kN/mm.With the increase ofζc value,the disturbance degree of local soil mass in the active area of pile top increases,but the influence range is roughly the same.The serious disturbance area is 2~3 times the diameter of pile.The reduction amplitude of pile lateral friction increases with the increase ofζc value,and the reduction rate of lateral friction increases in the early stage,and the lateral friction tends to be stable in the later stage.