高陡边坡段桥梁大直径桩基变形内力传递矩阵解

Matrix transfer solutions for deformation and internal force of bridge piles with large diameter in high steep slope ground

为分析高陡坡段桥梁大直径桩基在土体侧移作用下的受力变形特性,根据桩身所受水平荷载的差异,将桩基划分为自由段、被动段和主动段;引入桩身竖向摩阻抗力矩,基于三参数地基抗力模型和TIMOSHENKO梁理论,建立考虑桩身竖向摩阻与剪切变形影响的桩身侧向响应分析模型,应用矩阵传递法结合Laplace正逆变换推导桩身内力和变形的半解析解。通过现场试验结果和文献数值解结果的对比分析,验证本文计算方法的合理性,并结合工程实例分析桩身被动段竖向摩阻、剪切变形对桩身内力与变形的影响。研究结果表明:对于大直径桥梁桩基,桩身被动段竖向摩阻对桩身内力与变形的影响不可忽视;随着桩身被动段竖向摩阻增大,桩身的水平变形和弯矩减小,桩身最大弯矩逐步向浅层地基方向移动,桩身被动段在桩基受力变形中的荷载承载比提高;随着桩身直径增大,桩身剪切变形对于桩身弯矩的削减作用逐渐明显,荷载深层传递效应逐渐增强。

In order to analyze the load-deformation characteristics of bridge pile with large diameter under the lateral movement of soil in high steep slope ground, according to different horizontal loads of pile, the bridge pile was divided into free segment, passive segment and active segment, the model of vertical friction and impedance torque of pile shaft was introduced, and the lateral response analysis model considering vertical friction and shear effect was established based on tri-parameter model and Timoshenko beam theory. The semi-analytical solution of internal force and deformation of large diameter pile under combined loads was obtained by using matrix transfer method and Laplace inverse transform. The applicability of the proposed solution was verified by field test and analysis of examples, the influence of vertical friction of passive segment and shear effect on pile internal force and deformation was analyzed through an engineering example. The results show that the influence of vertical friction of passive segment on internal force and deformation of large diameter bridge pile can not be ignored.When the vertical resistance coefficient of foundation increases, the horizontal deformation and bending moment of pile will decrease, the maximum bending moment of pile moves towards shallow foundation, and the horizontal bearing characteristics of pile foundation increase. With the increase of pile size, the effect of pile shear on reducing pile bending moment tends to be significant, and the effect of deep load transfer tends to be enhanced.