层状地基静压桩贯入过程机理试验

通过在多层软粘土地基中静力压入单桩的室内模型试验，对模型桩在整个沉桩过程中压桩力、桩动端阻力及桩动侧阻力随桩贯入深度的变化情况进行了研究，获得了桩在贯入不同土层分界面时阻力的变化规律以及桩周土体应力的分布特征。并对开口管桩和闭口管桩贯入试验情况进行了比较分析，揭示了不同桩端形式桩在贯入过程中桩动侧摩阻力的发展规律，以及分层土体中开口管桩贯入过程中土塞的变化情况。试验结果表明：在粘性土中沉桩时，压桩阻力主要来自桩端向下穿越土体产生的端阻力，而侧摩阻力较小；由于桩侧水平应力的释放使得同一深度点上的动摩阻力随着桩的下沉表现出不同程度的降低，出现摩擦疲劳。

Model Test Research on Penetration Process of Jacked Pile in Layered Soil

The authors describe results from an experimental program in which instrumented model piles were jacked into layered soils in a test chamber. The pile sinking mechanism of jacked pile was discussed. A number of pile installations were carried out to study the change of penetration resistance，end resistance and side resistance with penetration depth of pile . The behaviors of different resistances crossing different soil interfaces during the process of pressing pile and soil pressure are obtained. Moreover, the test series was designed using both open and closed end to investigate the effect of different pile ending forms on the side resistance of pile, and the change of soil plug of open-ended pile during the penetration process are discussed. The experimental results indicate that the end resistance plays important role during penetration in clay soil; because of the pile side horizontal stress release, the side resistance decreases with the depth at the same elevation, appearing “friction fatigue”.