戈壁地基扩底掏挖基础抗拔试验及其位移计算

在甘肃和新疆7个戈壁碎石土场地完成了46个扩底掏挖基础抗拔现场试验，分析了基础抗拔荷载-位移曲线的阶段特征，应用L1-L2方法确定了所有基础抗拔承载力和位移。采用归一化荷载-位移双曲线模型对实测荷载-位移曲线进行拟合，得到了各试验基础归一化荷载-位移双曲线模型拟合参数取值及其统计规律，给出了同时考虑抗拔基础极限承载力计算理论模型误差和归一化荷载-位移双曲线模型不确定性时基础荷载和位移的计算方法。结果表明：戈壁碎石土扩底掏挖基础抗拔荷载-位移曲线呈初始弹性直线段、弹塑性曲线过渡段和直线破坏的3阶段变化规律，归一化荷载-位移双曲线模型可较好拟合基础实测荷载-位移曲线，归一化荷载-位移双曲线模型不确定性可转化为该双曲线模型拟合参数的不确定性，基于强度和变形统一的工程设计更有利于工程安全。

Uplift field tests and displacement prediction on belled piers in gobi

The field tests of 46 uplift-loaded belled piers were carried out at 7 gobi gravel sites in Gansu and Xinjiang, respectively. Based on the characteristics of the measured load-displacement curves, the L1-L2 method was used to obtain the ultimate bearing capacities and corresponding displacements. In addition, a normalized hyperbolic equation was applied to fit the measured load-displacement data. Accordingly, the fitting parameters of hyperbolic curve were provided and analyzed. A method was suggested for determining the allowable displacement and corresponding load by considering the uncertainties in the ultimate capacity model and the normalized load-displacement hyperbolic model. The uplift load-displacement curves of belled piers in gobi could be simplified to a generic load-displacement curve with three distinct stages: an initial linear stage, a nonlinear transition stage, and a final linear failure stage. The normalized load-displacement hyperbolic equation could be used effectively to fit the measured load-displacement data. The uncertainty in the normalized load-displacement hyperbolic curve could be studied by the corresponding fitting parameters of hyperbolic curve. The method to determine the allowable displacement and corresponding load would be more safety by considering capacity and displacement together.