轴向荷载作用下柔性桩沉降的解析算法

Analytical Method for Settlement of Flexible Piles under Axial Load

针对桩基设计中的沉降问题,将土体视为半空间无限体,桩简化为杆单元集合体,假设桩的每个节点存在虚拟荷载Pj。利用已有的工程数据,通过MATLAB拟合曲线计算得到非线性破坏准则的土层参数;再根据弹性半空间无限体的Mindlin剪应力解,得到桩体的虚拟荷载Pj。在极坐标下,根据每节点虚拟荷载求得桩的垂直应力系数Kzz,最后求出轴向荷载作用下引起的桩沉降值;对比分析了不同土体参数泊松比μ(0.1、0.3)和长径比L/d(10,20,30,40,50和60)情况下柔性桩沉降变化。结果表明:桩的沉降值均与桩径比、泊松比呈正相关;桩沉降值在泊松比μ=0.3时计算得到的沉降与本文所提出的方法更为接近,与规范法取桩1/3处开始计算所得沉降相差较大。

In the design of the pile foundation, the settlement of the pileisone of the controlling factors.The soilis regarded as a semi infinite body , and the pile is simplified as arodelement aggregate,assuming that eachnode of the pile has a virtual load Pj .Thesoil parameters of nonlinear failure criterion were fitted by MATLAB based o n the existing engineering data. According to Mindlin shear stress solutions of the elastic semi infinite space, a pile of virtual load Pjwas obtained. In polar coordinates, the vertical stress coefficient of the pile was obtained according to the virtual load of each nodeand finally the pile settlement value was also obtained under axial load. Comparative analysis of the single pile settlement was madeun der the conditions of different poisson ratio Kzz=of soil parameter （0.1 and 0.3） and length to diameter ratio L / D （10, 20, 30, 40, 50 and 60）. The results s howed that the settlement of the flexible pile is positively correlated with diameter ratio and poissons ratio whether the skin friction is taken as a nonlinear or linear variation. The calculated settlement value was more similar to the approach proposed in this study when poissons ratio μ was 0.3, and greatly different from the one obtained by the normal approach when the settlement value begins to be calculated at one third of the pile.