软土地区抗拔桩受力性状的试验研究

通过温州鹿城广场4根抗拔桩静载试验,分析了抗拔桩在不同荷载水平下的受力性状.试验结果表明,抗拔桩在荷载作用下,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,即抗拔桩表现为纯摩擦桩.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.在靠近桩端的桩侧土体中,当桩土发生相对位移时,即使其值很小,桩侧摩阻力也会急剧增加.当荷载（桩土相对位移）增加到一定值后,桩侧摩阻力随着荷载的增加而减小,即出现侧阻软化现象.

Mechanical properties of uplift pile in soft soils

The mechanical properties of uplift pile under different loads were investigated based on the static load tests of four uplift piles of Lucheng square in Wenzhou. The test results indicate that the axial force of uplift pile decreases with the increasing depth, and the axial force near the pile end does not exist throughout the whole test, in other words, the uplift pile is a pure friction pile. Tensile deformation of pile stem is the major part of the uplift displacement of single pile for scree stratum. The degree of developing side resistance is well corresponding to the relative displacement between pile and soil. Though very little relative displacement between pile and soil occurrs, the side resistance of soils which are close to the pile toe will increase sharply. When the load (relative displacement between pile and soil) increases to a certain value, the side resistance will decrease. This phenomenon is side resistance softening．