竖向荷载下超长群桩承载性状的模型试验研究

针对目前超长群桩尚缺乏深入研究的现状，设计并完成了一组软土地基中超长群桩室内模型试验。通过对超长群桩室内模型试验测试结果的分析，研究了竖向荷载下超长群桩的荷载传递机制和承载性状，得到了竖向荷载超长群桩的荷载一沉降曲线，桩身轴力分布规律、桩侧摩阻力分布规律。研究表明，随着桩顶荷载的增加，软土地基中超长群桩的Q—S曲线呈缓变型，未出现显著的转折点或陡降；桩身轴力沿深度逐渐递减，各级桩顶荷载作用下角桩桩身轴力略大于边桩；在整个桩长范围内，角桩的桩侧摩阻力稍大于边桩，两者分别出现了两个峰值，峰值点所在深度基本相同；群桩中角桩、边桩桩端阻力占桩顶轴力的百分比随桩顶荷载的增加均呈现先减小后缓慢增大再达到基本稳定的分布趋势。

Model Test Study on the Bearing Behaviors of Super-long Pile Groups under Vertical load

In view of relevant model test data of super-long pile groups is deficient, model test of super-long pile groups with a cap in soft soils are designed and completed. The the load transfer mechanism and settlement characteristics of the super-long pile, super-long pile with a cap and super-long pile groups are studied through the test data,and the Q-S curve ,body axial force,friction force around pile , the counter force of soil underneath cap and settlement of pile top were obtainned . The results show that the Q-S curve of pile groups belongs tothe the type of gradual descend, and there was not significant turn- ing point or plunged. ;The axial force disiminish pile gradually along the depth, and the body axial force of angle pile is slightly bigger than the edge pile at all levels of pile top load; In the range of whole pile longth, the friction force of angle pile is slightly bigger than the edge pile,and two peak appeared respec- tively, which is basically in the same depth ; As the load increase, the percentage of resistance at the horn of the pile to the the axial force of pile top decreases at first, then it would increase slowly , and reach to the basic stability finally.