超长灌注桩桩身压缩综合系数反分析  

Back analysis of composition coefficient of shaft compression for overlenqth cast-in-place bored piles

作　　者：蒋建平[1] 

机构地区：[1]上海海事大学海洋环境与工程学院,上海200135

出　　处：《岩土力学》2008年第9期2469-2475,共7页Rock and Soil Mechanics

基　　金：上海市教委交通运输与规划重点学科项目(No.J50601);上海市教委科研项目(No.05FZ03)资助

摘　　要：基于超长桩现场试验和数值模拟资料,通过反分析得出了桩身压缩的综合系数,进而对综合系数与其他参数的关系曲线特点、综合系数的影响因素、综合系数的回归预测等进行了研究。结果表明:(1)极限状态下超长灌注桩的综合系数的变化范围为0.278 5～0.988,规范法中取定值0.5或1.0的做法是不合理的。(2)综合系数总体上随桩顶荷载、桩身压缩、桩身总位移、桩身刚体位移的增大而增大,但关系曲线型式存在多样化。(3)超长桩综合系数与长径比的相关关系不明显,但总体来说,综合系数随长径比的增加而降低。对超长嵌岩桩,不同场地桩的综合系数与长径比相关关系较好;对超长非嵌岩,不同场地桩的综合系数与长径比相关关系不明显,但对某场地5根桩,综合系数与长径比的指数相关关系达到0.990 1。(4)总的来说,持力层与上覆土层弹性模量比小的桩的综合系数-桩顶荷载曲线在弹性模量比大的上方。(5)建立的6个场地多根桩的综合系数与桩顶荷载关系的回归曲线的相关系数平均为0.977 6,可为该场地及类似场地桩的桩身压缩综合系数的预测和计算提供参考。Based on tests and numerical simulation data of overlength cast-in-place piles, the composition coefficient of pile shaft compression is obtained through back analysis; and a study on curve characteristics between composition coefficient and other parameters, the influence factors of composition coefficient, and the forecast of composition coefficient is carried out. The following conclusions can be drawn. Firstly, under ultimate bearing capacity, the change range of composition coefficient of overlength cast-in-place bored piles is 0.278 5--0.988. So, it is not rational to adopt 0.5 or 1.0 for composition coefficient. Secondly, the composition coefficient increases with the increase of load on the pile top, pile shaft compression, total pile shaft displacement and pile shaft rigid body displacement. The shape of composition coefficient versus load on the pile top curve is various. Thirdly, the correlation between composition coefficient and length-diameter ratio is not obvious. But in generally, the composition coefficient decreases with the increase of length-diameter ratio. For overlength rock-socketed piles in different sits, there are good correlation between composition coefficient and length-diameter ratio, while for overlength non-rock-socketed piles in different sits, the correlation is not obvious except for five piles whose correlation coefficient is 0.9901 in a site. Fourthly, the composition coefficient versus load curves whose Ej Ect are smaller are larger than the curves whose Eat/Ect are bigger. Fifthly, the average correlation coefficient between composition coefficient and load on the pile top for many piles in six sites is 0.9776. So, these regression curves can be taken as important reference for the forecast of composition coefficient for these sites and similar sites.

关 键 词：桩身压缩综合系数 超长灌注桩 反分析 现场试验资料 

分 类 号：TU473[建筑科学—结构工程]