基岩内抗拔桩极限承载力的计算方法

A computational method of ultimate capacity of uplift piles in basement rock

采用极限平衡法,利用幂函数形式的滑移面假设,考虑桩岩界面作用力影响,推导出等截面抗拔桩在单层地基中极限承载力的计算公式。以软岩抗拔桩侧摩阻力试验结果为依据,提出软岩抗拔桩幂函数滑移面参数N=0时破裂面接近实际形状,并将计算结果与试验结果对比,验证了理论计算模型与假设的准确性。以理论模型为基础,提出对于软岩抗拔桩,桩岩界面作用力参数1c、岩石界面摩擦角δ可分别取岩石黏聚力c和内摩擦角?参数的0.7~0.8倍折减,分析了软岩抗拔桩极限承载力与软岩?、c的关系,发现抗拔桩极限承载力随着软岩摩擦角?、软岩黏聚力c增加而增加,软岩黏聚力对抗拔桩极限承载力影响更大。

Considering the interaction between basement rock and pile, a procedure for computing uplift capacity of uplift pile with constant section is deduced according to power function slip surface premise and based on limit equilibrium method. Based on the report of skin friction experiment of pile in soft rock, it is taken that the power function slip surface of pile is close to experiment when the coefficient N = 0. Meanwlile the comparison between theoretical predictions and experimental data indicates the accuracy of the computing formula. According to this computing formula, it is proposed that the coefficient of interaction between soft rock and pile should take 0.7-0.8 discount of coefficient of rock's internal friction angle ? and cohesion c. The relation between the internal friction angle ?, cohesion c and uplift capacity of short uplift pile in soft rock is revealed, where the uplift capacity is enhanced with increasing of the internal friction angle ?, cohesion c of soft rock and cohesion c is more efficient.