砂土中静压桩沉桩过程试验研究与颗粒流模拟

Experimental and numerical analysis of jacked piles during installation in sand

采用室内模型试验及颗粒流数值模拟研究了密实砂中静压桩沉桩过程,对桩周土体宏细观力学响应进行了分析研究。通过模型试验对浅层土体、桩身周围、桩端处土体的不同位移模式进行了比较分析,揭示了桩周不同位置土体的变位规律,并将孔隙变化场与宏观位移场进行相互印证,发现桩端土体位移模式与压密区基本呈圆孔扩张。对桩体贯入过程中的动端阻力、动侧摩阻力的发展规律以及临界深度等问题作了揭示。以室内模型试验为基础,建立了静压桩沉桩颗粒流模型,将数值结果与试验结果对比分析,通过分析土体细观变化模式揭示沉桩过程中宏观响应的内在机理。研究成果对于进一步明确沉桩挤土效应内在机理和沉桩阻力的发展规律都具有意义。

The experimental and numerical analysis of piles jacked into sands are conducted to study the behaviors of sand surrounding the piles on meso-mechanical characteristics and macro-mechanical response. Comparing and analyzing different displacement modes of soil located at different positions relative to the piles demonstrate the process of soil deformation in the lab tests. It is shown by the displacement and the variation of void ratios of soil that the mode of soil displacement and compaction area around the end of the pile appears as a spherical expansion. The variations of dynamic base resistance and shaft resistance and critical depth are analyzed. On the basis of the lab model tests, PFC^2D method is introduced to simulate the installation process of jacked pile. It is found that the results of numerical simulation are well consistent with those of the model tests. The macro-mechanical response is exposed by analyzing the variation of meso-parameters. The study is expected to contribute to disclose the mechanisms of compaction effects and the development of driven resistance.