层状地基中单桩-桩帽-土共同作用等效剪切位移法

An Equivalent Shear Displacement Method of Single Capped Pile in Layered Soil

基于单桩-桩帽-土共同作用的特征,推导了桩和桩帽下土体的荷载传递矩阵,提出了层状地基中带帽单桩的等效剪切位移法。当桩与桩帽下土体以及桩帽下土体与桩帽外侧土体交界面处的位移协调时,分别建立桩与桩帽下土体的平衡微分方程;考虑交界面处的相对滑动时,桩与桩帽下土体交界面处的侧摩阻力较大导致非线性,主要表现在桩与桩帽下土体间的相互滑动;当帽桩较小时,桩帽下土体与桩帽外侧土体交界面处的侧摩阻力引起的桩帽外侧土体自由位移场比较小。与有限元法、已有理论分析方法以及模型试验的对比表明桩帽的加入可明显增大带帽桩的整体刚度,并且一定尺寸的桩帽下桩体长径比的增大不会无限增大带帽单桩的整体刚度,桩帽始终贡献一定的荷载分担比例。

Based on the interaction of single pile, cap and soil, the load transfer matrixes of single pile and soil were proposed to establish an equivalent shear displacement method of single capped pile in layered soil. With the compatibility of displacement at the interface between the pile and the soil, equilibrium equations of pile and soil could be derived. With the increase of the total load on the pile cap, the lateral friction at the interface of the pile and the soil becomes so large that the occurrence of the sliding takes place. While there is little sliding at the interface between the soil under cap and the soil outside of the cap because of the less lateral friction, which gives rives to less settlement of the soil outside of the cap. Eventually, the results of the finite element method, existing theoretical method and the model tests were compared with those from the analytical method and were found to be in good agreement. The increase of the ratio of length to diameter does not infinitely enlarge the overall stiffness of the single capped pile, because the pile cap would afford part of the loading all the time.