大直径超长钻孔灌注桩荷载传递特性现场试验研究

通过无锡市地铁1号线高架桥段钻孔灌注桩试桩工程的现场静荷载试验及其桩身应力测试结果,分析层状地基中大直径超长钻孔灌注桩在竖向荷载作用下的荷载传递规律。试验结果表明:大直径超长钻孔灌注桩的荷载-沉降曲线无明显拐点,属缓变型;桩端承载力仅分担了桩顶最大加载值的6.8%,该试桩承载特征为典型的摩擦桩;桩身侧摩阻力与桩端阻力并不是同步发挥的,且两者之间相互影响;桩侧摩阻力呈由上而下逐步发挥的变化趋势;在具有相似物理力学特征的土层中,埋深对桩侧摩阻力的影响较显著,部分土层中桩侧摩阻力的实测值与规范的推荐值有明显差异。

Experimental Study of Load Transmission Property for Large-diameter and Super-long Bored Piles

The load transmission property of large-diameter and super-long bored pile in different soil layers under vertical load is analyzed,based on the measuring data of static load test and the pile stress measurement in a subway viaduct project of Wuxi City.The study indicates that the Q-s curves of large-diameter and super-long bored piles change gradually without obvious failure features.The pile tested shows characteristics of typical friction piles because the load at the tip is only 6.8％ of the total bearing capacity,the skin friction and tip resistance of the pile have mutual influence on each other and display asynchronously;the same situation also exists in side friction in soil layer,which demonstrates a top-down gradual changing trend.Burying depth has significant influence on the side friction of soil layers around the pile which has similar physical mechanical property,and some values about side friction are very different to the recommendation values according to the measured data.