桩顶荷载对负摩阻力性状影响的三维数值分析

利用ADINA非线性有限元软件, 考虑桩土相互作用,建立了单桩三维数值模型,分析了桩侧堆载作用下负摩阻力的形成过程,研究了桩项荷载作用下桩身荷载传递、桩侧摩阻力分布、中性点位置、桩顶附加沉降的变化规律以及桩顶荷载和堆载的施加顺序对桩侧负摩阻力的影响。分析结果表明:随着桩顶荷载增大, 桩侧负摩阻力逐渐减小,中性点明显上移,由桩侧负摩阻力产生的下拽力增加的速率变小,而桩顶附加沉降速率呈现逐渐增长的趋势;桩侧负摩阻力的大小受桩顶荷载和堆载施加顺序的影响,桩顶荷载先于堆载施加则产生的负摩阻力最大,而采用相反的加载顺序,产生的负摩阻力最小,甚至消失。所得结论对工程设计过程中负摩阻力的计算提供参考。

3-D FEM Analysis of Influences of Working Load of Pile on Negative Skin Friction Behaviors

Based on the finite element program ADINA, with considering the pile-soil interaction, a 3-D element model is used to study forming process of negative skin friction, and the load transmission and skin friction distribution of pile were analyzed as well as the variation law of neutral point position and additional settlement of pile, and the influences of working load and loading sequence on negative skin friction. It is shown that with the increase of working load, the rate of increase of dragload induced by negative skin friction becomes smaller, and additional settlement rate of pile becomes larger; and negative skin friction becomes smaller and position of neutral point in pile moves up while working load increases; the order of imposed working load and fill load also influences distinctly the negative skin friction, application of the fill load and then application of the working load can cause minimal negative skin friction. The results obtained provide useful knowledge to calculate negative skin friction in process of engineering design.