摘要
通过2根试桩的现场预浸水再加载试验,研究湿陷性黄土地基中人工挖孔扩底灌注桩在预浸水过程及其之后的加载过程中桩身摩阻力、桩端反力及桩身中性点深度的发展变化规律,并与我国现行规范进行比较。结果表明:(1)桩周土浸水过程中,桩身负摩阻力、正摩阻力及桩端反力均逐渐增大,桩身中性点位置逐渐下移。浸水结束时,中性点深度比为0.54～0.61,远小于桩基规范的推荐值;(2)在桩顶施加竖向荷载过程中,桩身负摩阻力逐渐减小,而正摩阻力及桩端反力继续增大,桩身中性点位置逐渐上移。桩顶竖向荷载P=11 000 kN时,中性点深度比为0.15～0.61,也远小于桩基规范的推荐值;(3)在桩顶设计荷载作用下,实测的桩身负摩阻力大小、分布范围及分布形式与桩基规范及黄土规范的规定有较大的差异;(4)黄土地基中桩身负摩阻力及中性点深度随着桩周土浸水、桩顶荷载处于一个动态变化过程中,负摩阻力的大小也受到桩径的影响。
Field tests were conducted to investigate the behavior of negative skin friction, positive skin friction, pile end reaction and neutral plane depth for man-made cast-in-situ belled piles in loess under pre-immersing and loading condition. The test results were also compared with the regulations of the technical code for building pile foundation of China. The results show that： （1） With the pre-immersing, negative skin friction, positive skin friction and pile end reaction are induced and increase with further immersing and the neutral plane gradually descend. The neutral plane depth ratio reaches 0.54 - 0.61 at the end of pre-immersing process, which is far smaller than that introduced in the technical code for building pile foundation of China. （2） When vertical load is applied on the pile head, negative skin friction decrease accompanied by the increasing of positive skin friction and pile end reaction as well as the ascending of the neutral plane. The neutral plane depth ratio reaches about 0.15 - 0.61 when P = 11 000 kN, which is also far smaller than that introduced in the technical code for building pile foundation of China. （3） The measured negative skin friction and its distribution dramatically differ from the ones calculated according to the technical code for building pile foundation of China. （4） The negative skin friction and the neutral plane depth are in a dynamic process with the immersing and the loading as well as the pile shaft diameter.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2012年第A01期3167-3173,共7页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(51078308)
陕西省教育厅科学研究计划资助项目(2010JK623)
关键词
桩基础
黄土
人工挖孔扩底灌注桩
试验研究
负摩阻力
中性点
pile foundations
loess soil
man-made cast-in-situ belled pile
experimental study： negative skinfriction
neutral plane
