扩底楔形桩沉桩施工过程数值模拟分析

摘要

扩底楔形桩是一种可以有效发挥桩侧摩阻力和桩端阻力、降低负摩阻力影响的新型纵向变截面桩；然而针对其沉桩施工过程中的挤土效应、沉桩阻力等研究则相对较少。基于PFC数值分析软件，建立扩底楔形桩和等体积混凝土用量的常规等截面桩的沉桩施工过程模拟数值模型；通过与等截面桩沉桩模型试验和圆孔扩张理论计算结果的对比分析，验证了本文所建立的数值分析模型的准确性和可靠性；对比分析扩底楔形桩和等截面桩沉桩过程中桩周土体位移场、应力场以及沉桩阻力等变化规律。研究结果表明：沉桩过程中桩端阻力值的大小，不仅与横截面面积有关，而且与桩侧界面形式有关；本文数值模型情况下，扩底楔形桩静压沉桩施工桩端阻力、桩侧摩阻力和整体沉桩阻力分别是等截面桩的1．8，1．1和1．5倍。%Belled wedge pile,which can improve the friction of pile shaft and tip resistance,and reduce negative skin friction effect,is one of variable cross-section piles.However,the analysis is seldom investigated concern-ing the pilling effect or pilling resistance characterizes on pile driving process.Based on PFC numerical simula-tion software,numerical models on pile driving process of belled wedge pile and traditional equal section pile with the same concrete usage were built.The accuracy and reliability of variable pile driving numerical models were verified by comparing with equal section pile driving model test results and the ones with cavity expansion theory.Then,the displacement field,stress field,and pile driving resistance were comprehensively discussed and analyzed.The results show that pile driving tip resistance is not only influenced by cross-section areas,but also influenced by form of pile side.The results also demonstrate that the pile driving tip resistance,pile shaft and total resistance of belled wedge pile are equal to 1 .8,1 .1 and 1 .5 times of those with equal section pile,re-spectively.