桩承式加筋路堤有限元几何建模方法及边坡效应研究

Geometrical modelling with finite element method and slope effect of geosynthetic reinforced and pile-supported embankments

桩承式加筋路堤常用的有限元几何建模方法包括单桩模型(含轴对称模型和单桩3D模型)、平面应变模型和3D断面模型,这些模型各具特点且前提假设各不相同,但却缺乏对比研究。使用非线性有限元软件ABAQUS结合现场试验结果进行了几何建模,对比分析了基于大面积堆载假定的模型与带边坡3D断面模型应力分布及变形的差异与原因。计算表明:3D断面模型最能反映桩承式加筋路堤真实工况,而单桩模型及大面积3D断面模型均低估了沉降量。边坡效应引起的水平位移及坡外隆起使得桩土沉降差、平均桩土应力比、桩顶荷载分担系数及土工加筋横向拉应力均在路肩区域达到极大值,且在路面范围内均大于大面积堆载工况。

The finite element geometric modeling methods commonly used for the geosynthetic reinforced and pilesupported embankments include the single pile model(including axisymmetric model and single pile three-dimensional(3D)model),the plane strain model and the full 3D piled embankments model.These models have different characteristics and assumptions,however,few studies have been carried out to focus on the comparison.The geometric modeling analysis is carried out by using the nonlinear finite element software ABAQUS combined with the field testing results.The differences and causes of stress distribution and deformation between the models with hypothesis of large-area surcharge filling and the full 3D piled embankments model with slope are compared and analyzed.The results of numerical model calculation show that the full 3D piled embankments model can best fit the real performance,while both the single pile model and the large-area surcharged full 3D piled embankments model underestimate the settlement.Due to the horizontal displacement and uplift swelling caused by embankment slope,the settlement difference,average stress ratio between pile and soil,the load sharing coefficient of the pile and lateral tensile stress of the geogrid all reach the maximum values under the shoulder region of the embankment.Meanwhile,under the pavement area,all the four parameters of the full 3D model with slope are larger than those of the full 3D piled embankments model with large-area surcharge filling.The numerical simulation results given by this paper can provide a meaningful reference for the geometrical numerical modelling of composite foundation under embankments and the analysis of the three-dimensional slope effect of embankments.