考虑冲刷效应的黄土沟壑区桥梁桩基极限承载力 计算方法

针对黄土沟谷地形特点和依托工程桩型特征,建立了考虑边坡系数和临坡距以及冲刷深度的桥梁桩基竖向承载力计算模型,利用FLAC3D三维软件分析水流的冲刷深度、边坡土削切对桥梁桩基竖向极限承载能力产生的不良影响; 通过回归方程拟合,建立了考虑局部冲刷效应的黄土沟壑地区计算公式。结果表明:计算桩基承载力的边坡系数与对应坡距耦合关系显著,桥梁桩基侧向摩阻力与对应因素的关联性随其摩阻力降低而增强; 局部冲刷作用和陡坡地形对桥梁桩基端部摩阻力影响较为微弱,对侧摩阻力影响相对较大; 桩基的竖向极限承载力负相关于水流冲刷深度,水流冲刷深度越低,产生的影响越大; 桥梁桩基的竖向承载力公式计算结果与模型试验结果相比影响度偏差较小,该公式具有较好的准确性与实用性,可为同类桩基设计计算提供参考。

Calculation Method of Ultimate Bearing Capacity of Bridge Pile Foundation in Loess Gully Area Considering Scour Effect

According to the topographic characteristics of the loess valley and the pile type characteristics of the supporting project, the vertical bearing capacity calculation model of bridge pile foundation considering the slope coefficient, critical slope distance and scouring depth was established. Based on FLAC3D software, the adverse effects of water erosion and slope soil cutting on the vertical ultimate bearing capacity of pile foundation were analyzed. Regression equation fitting was carried out, and the calculation formula of vertical bearing capacity of pile foundation in loess valley area was established. The results show that the slope coefficient has a significant coupling relationship with the slope distance in pile foundation bearing capacity calculation, and the correlation of the bridge pile foundation side friction to corresponding factor increases with its decrease. The effect of scour and steep slope topography on the pile end friction is weak, but the effect on the pile side friction is large. The vertical ultimate bearing capacity of the pile foundation has a negative correlation with the depth of water scour. The lower the depth value is, the greater the influence of each stage of scour is. Compared with the model test results, the influence degree deviation of the formula is smaller, and the formula has good accuracy and practicability, which can provide reference for the design and calculation of similar pile foundation.