砂土中单桩竖向抗压承载机制的离散元分析

将单桩视为平面问题，采用二维离散单元法分析了砂土中单桩竖向抗压承载机制。首先利用离散元模拟地基的形成、挖孔灌注桩的成桩过程以及地基土的双轴压缩试验；然后通过离散元模拟单桩竖向抗压静载试验，分析其承载机制。结果表明：随着桩的沉降增大，桩端阻力一直增大，桩侧摩阻力先增大后达到稳定值；单位桩长侧摩阻力从桩顶到桩端呈非线性增长趋势；当荷载达到桩的极限承载力时，桩端发生刺入破坏，导致桩侧与桩端附近土体的转动场梯度、应力场梯度增大，主应力发生大角度旋转。

Discrete element analysis of bearing mechanism of single pile in sand under vertical load

A study of the bearing mechanism of single pile in sand under vertical load is presented based on two dimensional discrete element method (DEM) by regarding single pile as a plane problem. Firstly, DEM simulations of formations of ground and boring cast-in-place pile are made; as well as the biaxial compression tests on the ground soil are taken. Secondly，DEM simulation of the static load test of single pile is carried out to study its bearing mechanism. The numerical results by DEM show that: the tip resistance increases straight as the settlement of pile increasing; while the shaft resistance inceases at first and then reaches a constant value; the shaft resistance of unit pile length increases unlinearly from top to tip of the pile; when the load reaches the ultimate bearing capacity of the pile, the pile tip penetrates into soil; this penetration leads to high gradients of rotation field and stress field around the pile and the soils near the pile, as well as the large rotation of principal stress.