密实砂土中竖向受压PCC桩端阻力计算方法研究

采用基于可视化摄影测量技术的室内试验和理论分析方法,对密实砂土中竖向受压现浇混凝土大直径管桩(PCC桩)桩端土体变形破坏规律及其端阻力估算方法进行研究。结果表明:PCC桩桩端周围土体在极限荷载阶段形成楔形竖向压缩区和侧向剪切变形区,桩端土体竖向位移在相同深度处始终高于等直径实心桩,呈现冲压破坏特征。在此基础上,利用普朗德尔地基理论,构建了考虑地基滑动面角度变化的PCC桩桩端土体破坏模型,给出了桩端阻力的理论计算方法,并通过承载力系数分析以及理论与试验结果的对比,初步验证了计算方法的合理性,为进一步完善与发展PCC桩设计计算理论提供了科学依据。

The Calculation Method of Tip Resistance of PCC Pile Subjected to Vertical Compressive Load in Dense Sand

Based on the visualization photogrammetry technology,combined with laboratory test and theoretical analysis method,the sand deformation rules and tip resistance estimation method of the cast-in-place concrete large diameter pipe pile(PCC) are studied under vertical compressive load.It is found that the sand around the pile tip forms a cuneate vertical compression zone and a lateral shear deformation zone at the ultimate loading stage.The vertical displacement beneath the pile tip is still higher than that of the single pile at the same depth and presents the characteristics of stamping failure.Based on the Prandtl bearing capacity theory,the tip resistance failure model is established considering the angle variation of the sand sliding plane.The theoretical calculation method of tip resistance is given,and the rationality of the calculation method is preliminarily verified by the analysis of bearing capacity coefficient and the comparison between theoretical and experimental results.The research results provide a scientific basis for further improving and developing the design and calculation theory of PCC pile.