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针对桩－土体系有限元数值分析模型中桩端尺寸效应的模拟问题进行了讨论。利用桩端节点位移的主－从关系建立了桩端－土体界面节点位移的约束条件。如果在有限元数值分析中将柱体模拟成梁杆单元集合体并在桩端施加这个约束条件，则可考虑桩端尺寸效应，特别是扩底桩桩端尺寸效应。为了显示桩端尺寸效应的影响进行了数值对比研究。数值结果表明：随着桩端尺寸的增大，桩端土体的塑性区分布及发展有很大的不同，桩的Ｐ－ｓ沉降曲线的差异很大，因此该效应对用数值法计算扩底桩的承载力是不容忽视的。
The simulation of pile tip size effect in the finite element analysis of pile-soil system is discussed. By using the principal-subordinate relationship between the displacement of pile-end nodes, the constraint conditions of the displacement of pile-soil interface are established. If the cylinder is modeled as an aggregate of beam elements and impose this constraint on the pile end in the finite element numerical analysis, then the size effect of the pile end can be considered, especially the pile end size effect of the expanded end pile. In order to show the effect of pile tip size effect, a numerical comparison study was carried out. Numerical results show that with the increase of pile tip size, the plastic zone distribution and development of pile-end soil are very different. P-s settlement curve of pile is very different, so the effect of numerical calculation Bottom pile bearing capacity can not be ignored.