水平循环荷载下砂土中斜单桩累积变形特性

Accumulated response of single batter pile under lateral cyclic loading in sand

研究斜单桩在风、浪、洋流等循环荷载作用下的累积特性.通过用户开发子程序将砂土刚度衰减模型嵌入桩-土体系有限元模型中,实现了单桩循环受荷特性的数值分析,研究不同循环幅值及循环次数下斜单桩的变形累积规律.研究结果表明,当桩身倾斜角由−25°逐渐过渡到25°时,在相同的静力荷载作用下,斜单桩桩顶位移及桩身相同位置处弯矩会不断增加,但在循环荷载作用下,桩顶位移与桩身最大弯矩的累积速度会逐渐下降.当循环荷载幅值较大时,负斜桩的桩顶位移和桩身位移段深度均小于竖直桩,正斜桩的桩顶位移和桩身位移段深度均最大.基于数值计算结果,对不同循环幅值和循环次数下的斜单桩桩顶累积位移和桩身最大弯矩进行拟合分析,提出适用于斜单桩的累积变形特性预测方法.

The accumulated responses of single batter pile under cyclic loadings(e.g.,winds,waves and ocean current)were analyzed.The degradation stiffness model of sand was incorporated into the pile-soil finite element model through the user subroutine.The numerical analysis of cyclic loading characteristics of single pile was realized.Then the accumulated response of single batter pile under various load levels and cycle numbers was analyzed.Results show that the displacement at pile head and the bending moment of pile are gradually increased under lateral static loads when the batter angle changes from−25°to 25°.The accumulated speeds of the displacement at pile head and the maximum bending moment of pile are decreased under lateral cyclic loads.When the amplitude of the cyclic load is relatively large,the displacement at pile head and the depth of deformation region of the negative batter pile are both smaller than these of the vertical pile,while these of the positive batter pile are the greatest.Fitting analysis of the accumulated displacement at pile head and the maximum bending moment of single batter pile was conducted based on the numerical simulation results.The corresponding methods for predicting the accumulated responses of single batter piles were proposed.