饱和砂土中打桩效应的有限元分析

Finite element analysis of pile-driving effect in saturated sand soil

运用Crisp程序,对饱和砂土中的打桩效应进行有限元分析.对桩周土采用线弹性、理想弹塑性2种本构关系以及圆柱孔扩张的应力边界条件法、圆柱孔扩张的位移边界条件法2种沉桩过程模拟方式分别进行组合计算,并对其中3种组合计算的超孔隙水压力、径向有效应力增量以及地面隆起等打桩效应的差异进行讨论.结果表明:运用理想弹塑性模型和圆柱孔扩张的位移边界条件法计算出的超孔隙水压力、径向有效应力增量以及地面隆起量等结果更为可靠.

The finite element analysis is performed by use of the Crisp program. Two constitutive relationships for soil around piles, i.e. the linear-elastic model and the ideal elastic-plastic model, and the two simulation modes for pile- driving process, i.e. the stress boundary condition method and displacement boundary condition method for simulation of the expansion of cylindrical cavity are adopted and combined for computation. Some differences in pile-driving effect, including the pore water pressure, increment of radial effective stress and land upheaval in three kinds of combination are discussed. It is concluded that the calculated results are more reliable if the combination of the ideal elastic-plastic model and the displacement boundary condition method is adopted.