不同桩长扩底抗拔桩极限承载力的统一计算模式

Unified approach to estimate ultimate bearing capacity of uplift piles with enlarged base

基于有限元数值模拟分析以及相关文献成果,提出了一个适用于不同桩长扩底抗拔桩极限承载力的统一计算模式。在极限状态下,扩大头处形成椭圆状局部破坏;而等截面段形成幂函数形式的曲线破裂面,幂函数曲线破裂面形状取决于土层及桩型参数。提出扩大头影响高度H1的概念,由扩底抗拔桩足尺试验数据,拟合出一个适合上海等软土地区扩底抗拔桩扩大头影响高度H1的计算公式。计算结果与工程实测结果的比较,验证了统一计算模式的正确性。另外,该方法也可退化为等截面抗拔桩极限承载力的计算。

Based on numerical analysis and previous study results,a unified analysis model is established to estimate the ultimate bearing capacity of uplift piles with enlarged base.Under the limit state,it is supposed to form an elliptic local failure mode on the enlarged base,while in the straight shaft,a power function of slip surface is assumed.The failure curve is related to the soil properties and the pile sizes.A concept of H1 is presented,which is the height influenced by the enlarged base.It is an important part in the present method.Then,a formula applicable to the soft soil region such as Shanghai area is proposed to estimate H1.The calculated results are in good accordance with the field ones,proving that the present method is feasible.Moreover,it is also practical in calculating the ultimate bearing capacity of straight-shaft uplift piles.