摘要
为了研究扩径桩受上拔荷载作用时的承载性状、荷载传递规律及桩侧摩阻力的分布特征,通过量测分级荷载作用下桩顶位移及桩身不同截面处的应变,选用宁波砂土开展等径桩、扩底桩和扩径加扩底桩的抗拔静载对比模型试验。试验结果分析表明:扩径桩较等直径桩而言能提高桩基抗拔承载力,在相同荷载下,减小上拔位移。在一定上拔位移范围内,扩径桩能充分利用扩大头上覆土体的承载力,发挥极大的抗拔阻力。在上拔荷载作用下,桩身轴力沿着深度方向逐渐递减,中部扩径处轴力出现突变减小,桩身各部分轴力均随着荷载的增加而增大。由于扩大头处有抗拔阻力存在,同级荷载下扩底桩下部桩身轴力大于等径桩。在桩身上部和中部,扩底桩与等径桩的桩侧摩阻力均沿着深度方向逐渐增加,且桩端附近均表现出侧阻的减小现象。由于扩大头的存在,扩径桩桩侧摩阻力在扩径段上下附近处无法充分发挥,但其抗拔承载能力仍为最强。
In order to study the bearing behavior of the diameter expanded pile,the axial force transmission and the distribution of the friction,the displacement of the pile top and the strain at different sections of the pile were measured under different load levels. The uplift static load model tests have been carried out with equal-diameter pile,expanded-base pile and multi-stage expanded pile. The experimental results show that the uplift bearing capacity of diameter expanded pile can be improved comparing with equal diameter pile,and the displacement of diameter expanded pile is less than equal-diameter pile under the same load. In a certain range of displacement,the enlarged base can take full advantage of the head bearing capacity of the soil,playing a great resistance to pull resistance. Under the uplift loading,the axial forces of piles gradually decrease along the depth direction,axial forces in the middle of expanded diameter decrease suddenly,and the axial force of each part of the pile increases with the increase of the load. Due to the existence of the pull resistance at the enlarged base,the axial force near the end of the pile of expanded-base pile is larger than the equal diameter pile. In the upper and middle part of the pile,the lateral friction of two piles gradually increases along the depth direction,and the phenomenon of the side resistance decreasing is shown near the end of both piles. Because of the existence of enlarged head,the lateral friction of the diameter enlarged pile cannot be fully played near the expansion section,but the ultimate bearing capacity of the pile is still the strongest.
作者
郑言东
郑荣跃
刘干斌
齐昌广
ZHENG Yan-dong;ZHENG Rong-yue;LIU Gan-bin;QI Chang-guang(Institution of geotechnical engineering, Ningbo University, Ningbo 315211, China)
出处
《水道港口》
2018年第2期217-222,共6页
Journal of Waterway and Harbor
基金
国家自然科学基金资助项目(51478228)
关键词
扩径抗拔桩
模型试验
承载特性
桩身轴力
桩侧摩阻力
uplift piles with enlarged diameter
model test
beating behavior
axial force
lateral friction
