存在软弱下卧层的大直径扩底桩桩端承载力的实用算法

PRACTICAL ALGORITHM FOR THE TIP BEARING CAPACITY OF LARGE DIAMETER BELLED PILE OVER SOFT SUBSTRATUM

基于半无限空间内部点荷载作用下应力分布的Mindlin解答,提出一种确定存在软弱下卧层的大直径扩底桩桩端承载力特征值的实用方法。首先,利用圆形均布荷载作用下的Mindlin解,推求扩底桩桩端底面的附加应力公式。然后根据规范给出的单桩沉降计算公式确定扩底桩的最终沉降计算公式。最后,根据扩底桩沉降的容许值反算桩端底面的附加应力,进而确定扩底桩的端承力。通过工程实例,将计算结果与实测数据进行对比,两者吻合较好。

It is presented a new method to determine the tip bearing capacity characteristic value of large diameter belled pile on soft substratum according to the settlement. Compared to the presented methods, it is a eonverse procedure here. First of all, the additional stress corresponding to the settlements is ealeulated with the settlement formula of single-pile in the code. Then, the tip pressure is obtained by substituting the additional stress into the Mindlin solution for a eireular uniform distributed load. At last, the tip bearing eapaeity is obtained. Those factors, such as the bottom diameter, pile length, thickness and physieal and mechanical properties of the bearing layer and substratum, ete, which effect the tip bearing capacity of large diameter belled pile on soft substratum, were considered in this method.