自平衡法试桩转换系数数值试验

采用三维有限元方法对桩顶压桩和桩底托桩承载特性分别进行模拟分析，研究了自平衡静载试验法中的转换系数。分析桩长、土类对荷载传递特性及转换系数的影响。结果表明：无论是在砂土还是在黏土中，随着桩长的增加，转换系数的变化曲线均呈凹形，类似抛物线形状分布；转换系数存在着极小值，不同土类转换系数的极小值不同，在35～55m桩长范围内可能出现托桩的极限承载力大于压桩的极限承载力的情况。

Numerical experiment on conversion coefficient of self-balanced pile test method

By use of 3-D FEM, the bearing capacity of jacking pries and uplift pries was simulated, and the conversion coeficient in serf-balanced static test loading was studied. The analysis of the influences of pile length and soil type on the load transfer performance and conversion ceeffieient demonstrates that, with the increase of pile length, the conversion coeffieient, no matter in sand soil or clay soil, shows a concave-shaped distribution, which is similar to a parabola, that the minimal values of the conversion coefficient exist and vary with the type of soils, and that the beating capacity of uplift piles is higher than that of the jacking piles with the length in the range of 35-55 m.