软土地区抗拔桩承载特性现场试验研究

Experimental Research of Field Tests on Uplift Behavior of Piles in Soft Soil Area

在工程实践中,抗拔桩基础已经得到广泛应用,但对于抗拔桩工作机理却研究较少。通过现场足尺试验,分析了抗拔桩的承载特性和变形特性,包括抗拔桩桩顶与桩底位移、桩身轴力分布、侧摩阻力分布以及侧摩阻力和桩土相对位移的关系等,试验结果表明:抗拔桩在受到上部荷载作用时,桩顶和桩底同时产生位移;随着上部荷载的增加,桩体下部侧面摩阻力逐次发挥作用,同时由于荷载在向下传递时不断减小,下部桩身所受轴力较小,桩土之间的相对位移也较小,桩侧摩阻力不易全部发挥出来。桩周各土层土的侧摩阻力达到最大所需的相对位移也可以利用桩土相对位移与侧摩阻力的关系曲线推算得出。试验结果对工程设计计算及相关研究提供了一定参考。

The uplift pile has been widely used in engineering projects ,but its bearing mechanism is not well known up to now .To study the uplift behavior and deformation characteristics of the piles ,the full-scale field tests on single uplift pile with uniform cross-section were performed .The tests included the displacement of top and bottom of the uplift pile , distribution of axial force of the pile ,distribution of side friction as well as the relationship between friction and relative displacement between the pile and soil .The result showed that displacement occurred at the top and bottom of the uplift pile under the upper load ,the side friction resistance of lower part of the pile body gradually came into play with the in-creasing of the upper load ;but due to the gradual decrease of the load in the transfer process ,the axial force of lower part of the pile body as well as the pile-soil relative displacement were small ,which prevented the side friction of pile from performing its full potential .Meanwhile ,the required relative displacement for the maximum side friction resistance of the soil surrounding the pile could be deduced from the curves of pile-soil relative displacement and side friction resistance . The tests results are advantageous to the engineering design and relative research of similar projects .