考虑边坡效应的桥梁桩基受力分析

Mechanics Analysis of Bridge Pile Foundation Considering Slope Effect

基于边坡上桥梁桩基的受力特点,考虑边坡对桩基的土推力和土抗力效应,依据桩段的静力平衡条件,建立考虑边坡效应的桩基础静力微分方程,采用有限差分法,建立考虑边坡效应的桩基础变形和内力的计算公式。结合某铁路桥梁桩基,分析边坡效应对桩基位移、弯矩、剪力和桩侧土压力的影响规律。结果表明:边坡效应使边坡上桩基的受力更为不利,与不考虑边坡效应的平地桩计算结果相比,考虑边坡效应后桩顶最大位移可增大78%,桩侧最大土压力可增大135%,并改变了潜在滑动面附近区域的弯矩和剪力分布;设计荷载下边坡上桩基的位移、弯矩、剪力和桩侧土压力的包络图将不再如平地桩那样以桩轴左右对称分布,而是桩基靠近边坡外侧的数值更大;在进行桩基设计和钢筋配置时不仅需要考虑边坡效应引起的变形和内力的增大,还应考虑不同荷载方向引起的力学性能在边坡内外侧的差异。

Based on the mechanical characteristics of bridge pile foundation on slope,and considering the earth thrust and soil resistance effects of slope on pile foundation,the static differential equation of pile foundation considering slope effect was established in accordance with the static equilibrium condition of pile section.With finite difference method,the calculation formula for the deformation and internal force of pile foundation considering slope effect was established.The influence law of slope effect on the displacement,bending moment,shear force and pile side soil pressure of certain railway bridge pile foundation was analyzed.The results show that the slope effect makes the force of pile foundation on the slope more disadvantageous.Compared to the calculation results of the pile on flat ground with no slope effect,the maximum displacement of pile top can be increased by 78%and the maximum pile side soil pressure can be increased by 135% with the consideration of slope effect.Moreover,the distribution of bending moment and shear force in the area near the potential sliding surface has been changed.The envelope diagram of the displacement,bending moment,shear force and pile side soil pressure of pile foundation on the slope under design load will be no longer symmetrically distributed along pile axis as flat ground pile,and the value near the outer side of slope is larger.In the design of pile foundation and the arrangement of reinforcement,not only the increase in the deformation and internal force induced by slope effect need to be considered,but also the difference in the mechanical properties of inside and outside the slope caused by different load directions should be considered.