负摩阻力作用下的单桩竖向承载性状

Vertical bearing behavior of single pile subject to negative skin friction

对负摩阻力作用下的单桩承载性状、负摩阻力与工作荷载之间的关系进行理论分析,然后建立单桩有限元模型,研究负摩阻力作用下桩基的承载性能、桩基的刚度以及下曳沉降变化规律。研究结果表明:下曳沉降由2部分组成,一是桩顶没有荷载作用时纯粹由负摩阻力引起的桩顶沉降;二是负摩阻力作用下,桩顶荷载下移中性点位置,使得承受桩顶荷载的桩段缩短所引起的沉降。负摩阻力在中性点平面形成的一对平衡力相当于在单桩桩体上施加了预应力,提高桩体本身的轴向刚度。

The vertical bearing behaviors of single pile under negative skin friction and the work load were analyzed. A finite element model of a single pile was set up to study the vertical bearing behavior, the pile stiffness and downdrag. The results indicate that the downdrag includes two parts： the first part is that the settlement of pile head induced only by negative skin friction and another part is the settlement of pile head caused by the work load which has moved down to the neutral plane when negative skin friction is hanging on the pile. The force equilibrium on the neutral plane acts like a prestressed force on pile which increases the pile stiff accordingly.