楔形桩极限承载力提高机理研究

为研究楔形桩相对等截面桩极限承载力提高机理及楔形桩承载力特性,根据楔形桩承载机理,将楔形桩承载过程分为弹性变形及挤土塑性破坏两个阶段.假定桩侧土体发生破坏时应力状态服从Mohr-Coulomb强度准则,建立了楔形桩承载力分析模型并提出了楔形桩极限承载力增大系数.通过与已有模型试验分析对比验证了本文解答的合理性.在此基础上,分析了承载力增大系数随桩-土界面摩擦系数、楔形角、静止土压力系数等的变化规律.结果表明:本文理论方法能够较为合理地预测楔形桩的极限承载力;楔形桩承载力增大系数随着土体内摩擦角增大而增大,但随着静止土压力系数和桩-土界面摩擦系数增大而减小,同时存在特定的楔形角使得承载力增大系数最大.

Study on enhancement mechanism of ultimate bearing capacity of tapered friction pile

To evaluate the enhancement mechanism of ultimate bearing capacity and the bearing capacity properties, considering the loading process of tapered pile, two stages were adopted in the proposed approach: the elastic stage and the soil-squeezing plastic stage. Based on these two stages, a simplified analytical expression for the ultimate carrying capacity was deduced. The bearing capacity augmentation factor was introduced to calculate the enhancement of the ultimate bearing capacity for the tapered pile. Then the effects of the friction coefficient on the pile-soil surface, the taper angle and the coefficient of earth pressure at rest on the bearing capacity were analyzed. Finally, the bearing capacity predicted by the proposed expression was compared with the data from the available model test. The results demonstrate the validity of the augmentation factor adopted in the prediction. The bearing capacity augmentation factors increase with the increase of the coefficient of earth pressure at rest and friction coefficient between pile and soil, while decrease with the increase of the soil friction angle. The augmentation factors reach the maximum values with a specific taper angle.