承受竖向荷载桩基的负摩阻力特性研究

分析了在桩顶荷载作用下的负摩阻力特性。分析结果表明，不考虑桩顶荷载的中性点位置是最低的，下拽力是最大的。当有桩顶荷载作用时，中性点的位置明显高于无桩顶荷载时，下拽力也明显小于无桩顶荷载时，而且随着桩顶荷载的增加，中性点上移的趋势明显，下拽力减小的趋势也很明显。较长桩中的中性点位置波动较小，附加沉降也较小。桩顶荷载较小时，负摩阻力对于桩基沉降的影响基本上是线性的。

Studies on Characteristics of Negative Skin Friction of Vertical Loaded Pile

The characteristics of negative skin friction (NSF) with working load on pile top were analyzed. Analysis results show that location of pile neutral point is the lowest and downdrag caused by NSF is maximal if neglecting working load on pile top. The location of neutral point of pile with working load action on top is obviously higher than that without working load and downdrag with working load on pile top is also obviously smaller than that without working load on pile top. Furthermore, the position of neutral point obviously trends to move upwards and downdrag decreases obviously as working load on pile top increasing. There's little fluctuation in the location of neutral point for longer pile, and also fewer additional settlement. The influence of NSF on pile settlement is almost in linear relation while working load on pile top is small.