桩承式路堤承载特性的颗粒流模拟

现有的土拱效应计算方法中，由于采用的计算模型不同，计算结果差异很大。文中克服传统连续介质力学模型的宏观连续性假设，采用二维颗粒流程序（PFC）建立基于模型试验的细观数值分析模型，对桩承式路堤中土体接触力、应力分布、主应力方向、竖向位移进行分析，并比较计算和实测结果，研究土拱效应的荷载传递机制。同时，对不同桩帽、桩间距、填土高度、颗粒大小、摩擦角的情况进行PFC方法的参数敏感性分析。研究结果表明，桩承式路堤桩顶处局部范围可按弹性核考虑；土拱的分布型式受桩帽型式、桩净距、格栅的影响；实际土拱作用的影响范围主要集中在路堤底面以上约1倍桩净距的区域；土拱内部的竖向应力和水平应力均随深度非线性改变，桩土应力比随着荷载水平、土体内摩擦角、颗粒大小的增大而增加。

Simulation of bearing characteristics of pile-supported embankments by particle flow code

Several methods are available for account the soil aching effect in the pile-supported embankment; but these present methods produce dramatically different results partially due to the different analysis models. To avoid the macro continuity hypothesis of traditional continuum mechanics model, a two-dimensional numerical model using particle flow code(PFC) has been established to simulate soil arching effect of pile-supported embankment. One part of the numerical analysis deals with load transfer mechanisms by investigating the contact stress, stress distribution and vertical displacement. Also the simulated results have been compared with model test results. The other part of numerical analysis consists to a parametrical study investigating the influence of the size of the pile cap, pile spacing, the fill height, particle size and the friction angle of embankment. It is shown that: (1) The local soil on the top of pile can be regarded as elastic nucleus. Soil arch forms were affected by forms of the pile cap, clear spacing of pile cap and geogrid. (2) The soil aching area is located around one time pile cap clear spacing over the bottom of embankment. (3) The vertical stress and lateral stress in the inner arching vary with depth nonlinearly and pile -soil stress ratio increases with the load level , the friction angle and particle size of soil.