基于位移的PHC管桩-土相互作用计算方法

在预应力高强混凝土（PHC）管桩-土相互作用低周往复荷载拟静力试验的基础上，研究桩身水平变形和桩侧土压力分布规律和计算方法，提出基于位移的桩-土相互作用计算方法，并与常用的M法和土压力（p）-桩身位移（y）曲线法等进行了比较。研究结果表明：应变换算法、M法以及p-y曲线法在计算桩身水平变形时存在较大误差；桩侧土压力分布规律为沿桩深度方向先增加后减小并在一定深度内反向；同时，随着位移荷载的增加，较浅层土压力增加较快，最大接近极限被动土压力，而较深层土压力增加相对缓慢；采用M法计算得到的桩身内力与变形呈线性变化，会高估桩身的承载能力，给抗震设计与计算带来不利影响，偏于不安全；p-y曲线法计算得到的桩身内力与变形关系没有明显的破坏与下降段，高估了桩-土体系的延性，偏于不安全，也与试验结果相差较大；提出的基于位移的桩-土相互作用简便计算方法能较好地计算静载或周期性荷载作用下桩基的内力、变形以及桩周土压力，可为有关规范的制定提供参考与借鉴。

Displacement-based Simplified Calculation on Soil-pile Interaction of PHC Pipe-piles

On the basis of the reciprocating low-cycle pseudo-static test on pile-soil interaction of prestress high concrete (PHC), the regularities of distribution as well as calculating methods of pile-soil pressure and lateral displacement were investigated. The calculating methods of displacement-based pile-soil interaction under the shear equilibrium were presented and compared with the traditional M method and p-y curve method, etc. The results show that there exists a large error in the results of lateral displacement of embedded pile calculated by the strain transform method, M method and p-y curve method. The pile-soil pressure along the pile depth increases at first and then decreases. Meanwhile, pile-soil pressure reverses under the certain depth. With the increase of displacement load, the pressure of shallower soil dramatically increases, nearly reaching up to passive earth pressure. However, the deeper soil slightly increases with the increase of displacement load. The internal force and the lateral displacement calculated by M method demonstrate the linear correlation. Unfortunately, the M method overestimates the capacity of piles and lowers the safety in the seismic design and calculation. The internal force and lateral displacement calculated by p-y curve method tend not to show the significant damage or descent trajectory. The p-y curve method overestimates the ductility of pile-soil system and lowers the safety in the seismic design and calculation. Furthermore, the values calculated by dint of p-y curve method are different from experimental results. The displacement-based interaction of pile-soil simplified calculating method is applicable to the calculation of internal forces, lateral displacement and pile-soil pressure. The proposed method provides a reference for the relevant specification.