大直径扩底人工挖孔桩承载力预测与数值验证

Prediction and numerical verification of bearing capacity of large diameter belled artificial hole digging pile

由于大直径扩底人工挖孔桩承载力较高,难以通过常规的静载试验得到其极限承载力。通过岩基载荷试验得到不同荷载作用下的岩基变形模量,基于荷载传递法,桩侧采用双曲线传递函数、桩端采用考虑变模量的非线性传递函数,提出了一种更能反映桩土体系受力性状的大直径扩底人工挖孔桩极限承载力预测模型,并结合有限元软件ABAQUS验证了该预测模型的可靠性。基于此预测模型对大直径扩底桩相关参数展开分析,结果表明,南宁软岩互层地基桩基表现出摩擦端承桩的特性,桩径和扩底直径相比桩长对桩基承载力影响更为显著;其中扩底直径为5. 6m的扩底桩相比同桩径等直桩承载力提高53%,且能有效减少混凝土用量,在工程地质条件容许的情况下应当尽可能使用扩底短桩。

Due to the high bearing capacity of large diameter belled artificial hole digging pile,it is difficult to obtain the ultimate bearing capacity through the conventional static load test.Based on the load transfer method,the hyperbolic transfer function is adopted on the pile side and the nonlinear transfer function considering the modulus at the pile end is proposed by a rockbased load test.This paper presents a prediction model to better reflect bearing character of pile soil system and to calculate ultimate bearing capacity of the large diameter belled artificial hole digging pile,and combined with the finite element software ABAQUS to verify the reliability of the prediction model.Based on this prediction model,the relevant parameters of large diameter belled pile are analyzed.The results show that the pile foundation of the soft rock interbed in Nanning exhibits the characteristics of friction end bearing piles,and thebearing capacity of the pile diameter and belled diameter are greater than the length of the pile.The belled diameter of 5.6m has a 53% increase in bearing capacity compared to the equal diameter pile,and can effectively reduce the dosage of concrete.Under similar engineering geological condition,belled short pile should be used as far as possible.