加筋路堤下刚性桩复合地基若干有限元建模类型分析

Finite element modelling types for rigid pile composite foundation under geosynthetic-reinforced embankment

基于加筋路堤下CFG桩复合地基现场试验段分别建立单桩、群桩及全断面有限元模型,探讨几何模型、桩土接触等条件对系统变形、应力分布及荷载传递的影响。结果表明:受路堤边界效应影响,全断面模型的沉降及荷载分配完成较快,应力比n、桩的荷载分担效率系数E均在路肩内侧附近达到最大值,且分别高于路中位置15.7%和5.2%。坡脚位置桩顶位移矢量角、桩的水平荷载及弯矩显著。单桩与群桩模型规律较为相近,沉降发展相对迟缓且略低于全断面模型。各有限元模型预测的最终状态的n,E及等沉面高度均正比于其桩土沉降差。统计表明单桩加固范围内实测与理论荷载误差可达-35.1%~58.5%,桩土竖向应力分布并不均匀。设置允许桩土发生相对位移的接触条件将增大沉降量及等沉面高度,并影响浅层桩身受力。桩承式加筋路堤有限元数值计算应优先选择考虑桩土接触条件的全断面模型。

Based on the in-situ test section of CFG pile composite foundation under geosynthetic-reinforced embankment,the finite element models for a single pile,group piles and full section are established,respectively,and the influences of the geometric model,pile-soil contact and other conditions on system deformation,stress distribution and load transfer are discussed.Mostly due to the influences of embankment boundary effect,the settlement and load distribution of the full-section model are both developed in time as the in-situ test results.The stress ratio(n)and the load-sharing efficiency of pile(E)both reach the maximum near the inner side of the embankment shoulder and are 15.7%and 5.2%higher than those in the center of the embankment,respectively.At the toe of the slope,the displacement vector angle of the pile top,the horizontal load and bending moment of the pile are quite significant.Under the surcharge with the same equal thickness,the single-pile model has similar performance with the group-pile model,and the settlement development of both is relatively slow and slightly lower than that of the full-section model.In each model,the predicted results show that n,E and the equal settlement surface height are all directly proportional to the differential settlement of soil-pile on the subsurface at the final computing time.The distribution of non-uniform vertical stress on the subsurface is shown according to the numerical results.According to the statistic results,the deviation between the test load and the theoretical load can be-35.1%to 58.5%within single-pile reinforced area.Setting the contact interaction to enable the relative displacement of pile and soil will increase both the settlement and the height of the equal settlement surface,and also affect the stress of the shallow pile shaft.The full-section finite element model with pile-soil interaction is recommended to investigate the composite foundation under reinforced embankment.