桩–土动力相互作用问题中桩身刚度的影响效应研究

 通过开展2类刚度差异较大的桩基础的离心机动力模型试验，系统地讨论柔性桩和刚性桩的地震反应差异，以及周围土体对桩体的不同作用效应。对于柔性桩，周围土体的作用主要体现在对桩的约束效应上；然而对于刚性桩，土体更大程度上对桩体施加附加惯性力的作用，以致桩筏基础的周期明显高于无土时的周期；针对柔性桩和刚性桩显著的地震反应差异，巧妙地提出用桩筏结构自振频率 界定两者的行为，可为今后类似研究提供参考。

EFFECT STUDY OF PILE STIFFNESS ON PILE-SOIL DYNAMIC INTERACTION PROBLEM

By conducting the centrifuge dynamic tests coverage to two kinds of piles with great stiffness difference，This paper investigated that there exist some quite different characteristics between behavior of flexible and stiff piles during earthquake shakings. For the flexible piles，the bending moment drops to a very small value below the changeover point. This is similar to the bending moment distribution curves for laterally loaded piles，and suggests that，for flexible piles，the clay beneath a certain depth is able to provide lateral support for the pile. On the other hand，for the stiff piles，the bending moment changes over at a much larger depth indicating that lateral support is not effective until much deeper. There is also much larger reverse moment below the changeover depth. This is quite different from the typical moment distribution of laterally loaded piles，the surrounding clay effect on the pile mainly focus on the providing additional inertia forces. Finally，a skillful parameter of pile-raft native frequency was presented herein to quantify pile flexibility.