摘要
通过广东软土地区大直径超长钻孔灌注桩大吨位静载试验,分析该地区大直径超长钻孔灌注桩承载特性及荷载传递机制,为该地区大直径超长桩的理论研究和工程应用提供宝贵的参考数据。实测结果研究表明:试桩的Q-s曲线呈缓变型,桩端承载力分担总荷载比例均低于15%,表现为摩擦桩特性;随桩顶荷载增加,桩土相对位移沿桩身的递增幅度呈先增大后减小的趋势,淤泥质粉质黏土和淤泥达到极限侧摩阻力所需的桩土相对位移分别为17和6 mm,砂土达到极限侧摩阻力所需桩土相对位移为22~27 mm,桩身上部土层侧摩阻力发生不同程度的软化;桩身上部粉质黏土的桩土相对位移为18~23 mm,在桩土总的相对位移达40 mm时,下部粉质黏土层侧摩阻力达到极限值的87%以上,桩土相对位移继续增大时,侧阻增加趋势较为平缓,并逐渐接近于极限值;风化砂岩侧摩阻力随桩土相对位移的增加而增大,极限荷载下侧摩阻力未完全发挥;桩端阻力随着桩端沉降量的增加呈加工硬化型。
The large tonnage static load tests on 2 large-diameter and super-long bored piles cast in-situ in soft soil area in Guangdong were carried out to investigate mechanism of load transfer. The results show that load carrying curves of the piles vary gradually. The piles tested have the characteristics of friction piles because the loads at the pile tips are less than 15% of the total bearing capacity of the piles. With the increase of load at pile top,the increasing rate of relative displacement between the piles and soil at certain position of pile increased initially and then decreases. When friction resistence limit between the pile and soil is reached,the pile-soil relative displacement in muddy silt clay,silt and sand are 17 mm,6 mm and 22–27 mm respectively. Pile body of silty clay of the relative displacement of piles and soil is 18–23 mm,40 mm in total relative displacement of piles and soil, The shaft resistance in deeper silty clay layers is about more than 87% of ultimate value while pile-soil relative displacement is 40 mm. The increase rate of the shaft resistance descends gently as the increasing of the relative displacement. With the increasing of pile-soil relative displacement,the shaft resistances in weathered sandstone increased and did not reach the limit capacity.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2015年第4期849-855,共7页
Chinese Journal of Rock Mechanics and Engineering
基金
广东省交通运输厅科技计划项目(2012–01–001)
国家自然科学基金资助项目(41202193
41272295)
关键词
桩基础
大直径超长桩
极限承载力
侧摩阻力
软化
桩土相对位移
pile foundations
large-diameter and super-long piles
ultimate bearing capacity
shaft resistance
softening
pile-soil relative displacement
