粉质黏土中单桩竖向承载力的离心模型试验研究

桩基础研究的核心问题是桩承载力和桩-土相互作用,包括桩周土的变形和饱和土中孔隙水压力的变化。通过离心模型试验的方法,利用竖向压桩设备把桩压入土体,研究饱和及非饱和粉质黏土中单桩的竖向承载力,以及加载过程中桩周土体的变形和孔隙水压力的变化。粉质黏土饱和后,桩基的承载特性表现出软化的特点,且桩基的承载能力比非饱和粉质黏土中的桩基小,非饱和粉质黏土的压桩试验中桩基没有出现明显的极限承载力。桩基的加载特性与桩周土的变形响应具有显著的相关性,桩的加载过程对桩周土体变形的影响有一定范围,超过这个范围,土体的变形可以忽略不计。饱和粉质黏土中桩基的加载对桩周土体孔压的变化也有一定的影响范围,与桩周土体的变形范围体现出类似的规律。距离桩较近时,桩周土的变形较大;距离桩越远,土体的变形受到桩的影响越小。

Centrifuge model tests on vertical bearing capacity of single pile in silty clay

The essential researches on pile foundations are on bearing capacity of piles and interaction between the pile and subsoil, including deformation of soil and pore pressure change of saturated silty clay around the pile. Centrifuge model testing is used to study vertical bearing capacity of single pile both in saturated and unsaturated silty clay. The pile is pressed into the soil by vertical loading device, and deformation of soil around the pile and pore pressure change during the loading of pile are measured and then analysed. When saturated, the soil around pile results in pile’s softening of bearing characteristics, and the bearing capacity of pile gets smaller than in unsaturated soil. However, an obvious ultimate bearing capacity in the experiment of unsaturated silty clay does not exist. Deformation of subsoil has a significant relevance to the loading of piles. The impact of loading of the pile on the deformation of soil around the pile has a certain limit of distance, out of which the displacement of soil is negligible. The results show that the limit of distance is about 7 times the length of pile section, and a certain limit of distance exists in the impact of loading of the pile on the water pressure changes in saturated silty clay around the pile, which reflects the same rule as the displacement of soil around the pile. Displacement of soil is greater in the places closer to the pile. As the distance from the pile increases, the impact of piles on soil deformation decreases.