软土地区抗拔桩受力性状的现场试验研究

Field test study on behavior of uplift pile in soft soil area

通过温州软土地区3根抗拔桩的静载试验研究了抗拔桩的受力性状。试验结果表明,抗拔桩桩身轴力随着深度的增加而减小,在桩端处桩身轴力始终为零,即抗拔桩始终表现为纯摩擦桩性状。对于持力层是卵石层的抗拔桩,桩身拉伸量是桩顶上拔量的主要组成部分。桩侧摩阻力的发挥程度和桩土相对位移有着很好的对应关系。当桩土相对位移较小时,桩长范围内土层的侧摩阻力均未达到极限状态,且随着桩土相对位移的增大而增大。当桩土相对位移增加到一定值后,桩侧摩阻力完全发挥且随着荷载的增加而减小,即出现侧阻软化现象。

Static load tests on 3 uplift piles were conducted to investigate the behavior of the uplift pile in Wenzhou soft soil area.The test results show that the axial force of the uplift pile decreases with increasing depth,and the measured tip resistance in uplift case is near zero during the whole loading cycle.This suggests that the uplift pile behaves as a pure friction pile.It also can be concluded that the pile shaft tensile deformation is the major part of the uplift displacement of single pile rested on gravel layer.Furthermore,the mobilization of the skin friction is related to the relative displacement between pile and soil.When the relative displacement between pile and soil is small,the skin friction increases with an increase in the relative pile-soil displacement up to the limiting state of the shaft resistance.However,when the skin friction is fully developed,the skin friction softening is existed and accompanied with a reduction in skin friction.