成层土中倾斜荷载作用下桩承载力有限元分析

Finite element analysis of bearing capacity of pile under inclined load in layered soil

利用有限元方法对现场单桩水平载荷试验进行模拟,在此基础上,分析了成层土中桩在倾斜荷载作用下其竖向分量的有利作用和横向土抗力分布特点。计算结果表明,在地面下一定范围内,倾斜荷载作用下的桩侧摩阻力比水平荷载作用下的桩侧摩阻力大。在土层分界处土抗力分布有明显的跳跃。达到一定深度后,横向土抗力主要是静止土压力,而由荷载引起的横向土抗力很小。承台能有效减小土体及桩的水平位移。模拟的灌注桩和钢管桩桩顶在地面以上的自由长度较小,竖向分量由于桩身挠曲变形而产生的P-Δ效应较小,所以就算例中的灌注桩和钢管桩而言,荷载倾斜度不大时,荷载竖向分量提高了桩的侧阻并由此增大桩侧土竖向应力,对桩水平承载力总体上起到了有利的作用。

Tests of single pile under lateral load are modeled with FEM. The favorable effect of vertical load and the distribution of lateral soil resistance along pile under inclined load in layered soil are analyzed. The shaft resistance along pile under inclined load is greater than that of pile under lateral load within a certain depth below ground surface. Significant changes of lateral soil resistance at the surfaces of different soil layers along piles are observed. To a certain depth below ground surface, lateral soil resistance is nearly equal to the static soil pressure. Pile cap can reduce lateral displacement of pile efficiently. The free length of pile above the ground surface discussed herein is rather small, thus the P-A effect caused by vertical component of inclined load is small. The larger the shaft resistance along pile under inclined load, the bigger the vertical stress in the soil surrounding the pile. The vertical component of inclined load will increase the lateral bearing capacity of pile.