不同直径单桩静压贯入力学特性模型试验研究

为探讨不同桩径静力压入单桩的贯入力学特性,设计了不同桩径的模型桩,基于光纤光栅(Fiber Bragg Grating,简称FBG)传感技术,开展了黏性土中静压贯入两种不同直径单桩的模型试验研究。结果表明:试桩的压桩力基本呈线性增加趋势,桩径越大,压桩力越大;桩径不同会影响单桩的荷载传递性能,由于桩径越大挤土效应越明显,沿深度方向的桩身轴力传递性能优于小桩径桩;桩身单位侧摩阻力随深度增大而增大,桩径越大,对土体的侧向挤压力越大,桩身单位侧摩阻力越大;同一深度,两种不同直径单桩桩身单位侧摩阻力都出现"侧阻退化"现象,"侧阻退化"现象随着贯入深度的增加越明显,且桩径越大,桩身单位侧摩阻力退化越显著;均质黏性土地层静压沉桩阻力主要为桩端阻力,沉桩结束时,试桩桩端阻力占沉桩阻力的比例分别为59.5%和66.2%,不同的桩身直径既影响桩端阻力,又影响桩侧阻力。确定静压贯入沉桩阻力时,考虑基于黏性土的侧阻退化后实际值更为合理。

Model test study on single piles with different diameters subjected to penetration mechanical characteristics of jacked pile

Model tests are carried out on the jacked single piles of different diameters under model pile of different diameters in clayey soil, which aims to investigate the penetration mechanical mechanism. The results show that pile driving pressure of test pile shows linear increase. The load transfer performance of test piles will be affected by different diameters, and the axial force transfer capability of large diameter in the depth direction is better than that of small diameter since the compacting effect is more obvious. Unit skin friction of pile increases gradually as the depth increases, which is larger due to the lateral extrusion force increases as the diameter increases. At the same depth, unit skin friction of two different diameters pile demonstrates "friction fatigue", which also decreases obviously as the depth increases. At the same time, the "friction fatigue" is more obvious as the pile diameter increases. In homogeneous clays, the piling resistance mainly includes the end resistance. The end resistance of test pile accounts for 59.5% and 66.2% of the piling resistance when sinking pile ends. The end resistance and the shaft resistance are influenced by the pile diameter. For the confirmation of the jacked piling resistance, it is more rational to consider the actual value with the friction fatigue of clayey soil.