桩承土工格栅加筋垫层复合地基力学变形特性三维数值分析

桩承土工格栅加筋垫层复合地基作用机理复杂，设计计算主要以经验为主，给设计与施工带来盲目性。采用有限元分析软件Ansys，建立群桩三维模型，对其力学变形特性进行了分析，结合工程实例，将数值模拟结果与现场监测结果进行比较分析，两者较为吻合。结果表明：桩与桩端土均具有最优弹性模量；桩土最大应力比在桩顶下某一深度，桩身最大轴向应力在桩顶下中性点，由于应力集中，在桩端处两者均突然减小；桩端土刚度在离桩底某一深度范围对桩土应力比产生影响；加筋垫层刚度仅在其下某一深度范围内对桩间土应力产生影响，刚度较小时对应力比的调节作用更明显；加筋垫层尺寸对桩身轴向应力和桩侧摩阻力都产生显著影响，桩顶下0.3倍桩长处最显著。

3D Numerical Analysis on Mechanical Deformation Characteristics of Geogrid-reinforced and Pile-supported Composite Foundation

The mechanism of geogrid-reinforced and pile-supported earth platform composite foundation is very complex, when based on the experience for the design and calculation, some blindness in the design and construction will be produced. Three-dimensional model for pile group is established by Finite Element analysis software Ansys, and mechanical deformation characteristics of geogrid-reinforced and pile-supported earth platform composite foundation are analyzed. Base on an engineering example, the results between numerical simulation and field monitoring are compared, and both are more consistent. The results are as followed: both pile and pile end soil have optimal modulus of elasticity; the maximum pile-soil stress ratio is present to a certain depth on the top of the pile, and the maximum pile axial stress is present to the neutral point on the top of the pile, the pile-soil stress ratio and the pile axial stress decrease suddenly due to the stress concentration is produced at pile end; The stiffness of pile end soil has some influence on pile-soil stress in a certain depth from the bottom of pile; The stiffness of geogrid reinforced cushion has some influence on soil stress between piles under a certain depth on the bottom of cushion, the regulatory role for pile-soil stress ratio is more significant when the low stiffness. The size of geogrid reinforced cushion has some significant influence on pile axial stress and pile side frication stress, the most significant influence is present to 0.3 times pile length on the top of pile.