扩底抗拔桩变形的解析计算方法

AN ANALYTICAL CALCULATION METHOD FOR DISPLACEMENT OF UNDER-REAMED TENSION PILES

将扩底桩扩大头简化为荷载传递弹簧,根据扩底桩平衡微分方程,推导得到计算扩底抗拔桩弹性变形的无量纲表达式。为了研究扩底抗拔桩的非线性变形性状,假定桩侧土体荷载传递曲线(t-z曲线)满足理想弹塑性关系,桩侧土体强度随深度成幂函数变化,推导计算扩底抗拔桩轴力和变形的弹塑性解析表达式。将计算结果与模型试验和现场试桩试验结果进行对比,结果表明解析分析方法能较好的预测扩底抗拔桩的变形,理论预测结果与实测结果比较吻合。该方法既能避免繁琐的数值计算又能合理预测扩底抗拔桩的变形,具有较好的工程应用前景。

The belled-out section of under-reamed piles is supposed as spring, and the non-dimension solutions of elastic displacement are deduced according to the equilibrium differential equation of under-reamed piles. The ideal elastic-plastic load-transfer functions for pile shaft are adopted to study the nonlinear deformation of the under-reamed tension piles. The lateral soil strength is regarded as power function, which varies with the depth. On this basis, a series of the closed-form elastic-plastic solutions of displacement and axial load at a certain depth from the ground surface of under-reamed tension pile are deduced. Comparing with the actual responses of the model experiment and in-situ pile test, this proposed method can give reasonable results. The theory solutions not only avoids complex calculation but also predicts the displacement of under-reamed tension piles reasonablely. It can be applied to the actual projects.