一种新型多节旋挖挤扩桩荷载传递机理现场试验研究及在铁路桥基的首次工程应用  

In-situ experimental study on load transfer mechanism of a new type rotary compaction pile with extruding discs and its first application to railway bridge engineering

作　　者：张德华[1] 王梦恕[1,2] 王磊[1] 崔隽[3] 

机构地区：[1]北京交通大学,北京100044 [2]中国中铁隧道集团有限公司,河南洛阳471009 [3]太原理工大学,山西太原030024

出　　处：《土木工程学报》2013年第7期66-73,共8页China Civil Engineering Journal

基　　金：铁道部重点科技项目(2009G010-F)

摘　　要：通过对5根不同长度的新型旋挖挤扩灌注桩与1根直孔桩的承载力及其荷载传递机理的现场静载试验,分析不同桩长单桩单盘、单桩三盘情况下桩侧摩阻力、承力盘阻及桩端阻力共同协调工作的受力特点,确立新型旋挖挤扩成孔工艺下桩基的荷载传递规律。结果表明,当桩身产生不足1.5mm位移时,承力盘阻发挥较大承载力。当桩身承载达到极限时,盘阻承担了45%的总荷载,极大地改善了普通摩擦桩承载力主要依靠侧摩阻力发挥其承载特性的受力特点。此外,同样桩长4m的三盘旋挖挤扩桩承载能力达到144kN,累计沉降值仅为4.27mm,远大于桩长4m的直孔桩承载力,累计沉降变形亦小于直孔桩累计沉降值5.56mm。当两者沉降相同时,旋挖挤扩灌注桩提供承载力为直孔桩的1.78倍。当旋挖挤扩灌注桩和直孔桩具有相同承载力时,前者比直孔桩所需桩长大幅减小,同时控制沉降效果更好。基于试验成果,首次成功将旋挖挤扩灌注桩应用于铁路桥梁桩基——津保铁路京九联左线跨京九铁路特大桥项目,对其中6个墩台36根基桩每桩减短10m桩长,在达到设计要求承载力前提下,沉降值仅5mm,满足铁路桥梁高速行车对沉降的严格要求。同时大大降低超长桩的施工难度,节约了工期,节约成本造价达20%,经济效益十分显著。Based on static load tests of 5 rotary compaction piles with extruding discs and one column pile, the bearing capacity and load transfer mechanism of pile-disc-soil were analyzed. The investigated piles include a 2-meter pile with single disc, a 4-meter pile with 3 discs, and a 4-meter column pile. The mutual coordination characteristics among pile shaft resistance, disc bearing resistance and pile tip resistance were established. The results show that Q-s curve of rotary compaction pile with discs is flatter than that of column pile, and it can provide higher bearing capacity with smaller deformation. With the same deformation, the bearing capacity that rotary compaction pile with extruding discs provides is 1.78 times that provided by column pile. On the other hand, when rotary compaction pile with extruding discs and column pile attain the same bearing capacity, the former＇ s settlement is usually much smaller. Based on test results, rotary compaction pile with extruding discs was applied to a big bridge engineering project, Jingjiulian bridge project of Tianjin-Baoding railway which crosses Beijing--Kowloon railway in left line. Although each pile was shortened by 10 meters, it may satisfy the design requirements of bearing capacity, while its lower settlement is merely 5mm.

关 键 词：旋挖挤扩桩 现场试验 荷载传递 铁路桥基 

分 类 号：U443.1[建筑科学—桥梁与隧道工程]