加载次序引起的负摩阻力桩摩阻力分布的变化

Changes of friction distribution in negative skin friction pile induced by loading sequence

简要分析了加载次序对于负摩阻力桩基桩土相互作用影响的机理。采用有限元方法计算比较了这种差异。计算结果表明,加载次序的变化会引起桩身摩阻力分布、中性点位置和下拉力的变化。桩身摩阻力的分布差异主要是桩身上部负摩阻力的大小,负摩阻力先出现时的负摩阻力值较小。这种状况在各级桩顶荷载下不会改变。负摩阻力先出现时,中性点的位置比较低,两者的差距随着桩顶荷载的增大而变得加大。负摩阻力先出现时下拽力小于桩顶荷载先施加的情况。这对于负摩阻力桩基检测的研究和应用是有益的。

Influence mechanisms of loading sequence on pile-soil interaction of negative skin friction (NSF) are simply analysed. Finite element method is used to calculate the differences.Analysis results show that changes of loading sequence would induce the changes of friction distribution in pile,neutral point position and the downdrag caused by NSE Differences of friction distribution is mainly amount of negative skin friction in upper part of pile,negative skin friction is smaller when negative skin friction appears first; and it does not change with load of pile.Position of neutral point is lower,when negative skin friction appears trust;the differences increase as vertical load of pile increase.When negative skin friction appears first,downdrag is smaller than that of pile load applied firstly;the difference increases as load of pile increase.The results will be useful to the research and application for checking negative skin friction.