基坑开挖对坑底桩基础工作性状影响  

Effect of Pit Excavation on Behavior of Pile Foundation Buried in the Pit

作　　者：王丽[1,2] 杨文彬[2] 郑刚[1] 

机构地区：[1]天津大学建筑工程学院,天津300072 [2]大连交通大学土木与安全工程学院,辽宁大连116028

出　　处：《大连交通大学学报》2016年第5期93-98,共6页Journal of Dalian Jiaotong University

基　　金：国家自然科学基金资助项目(51208071)

摘　　要：逆作法具有对周边环境影响小、不影响地面交通等优点,在大中型城市基坑开挖中被越来越广泛的使用.逆作法施工过程中,坑底工程桩既承担地下室及上部结构的重量,同时又受到开挖卸荷的影响,其工作性状有待进一步研究.通过模型试验及有限元分析方法,研究了逆作法对坑底桩基础工作性状的影响.试验结果表明由于重力二阶效应(P-Δ效应),逆作法基坑开挖引起的桩身弯矩比顺作法基坑开挖的桩身弯矩大很多.有限元计算结果表明:在基坑开挖工程中扩底桩有很好的限制桩顶回弹的作用;通过对坑下土体进行注浆加固可以有效限制墙身侧移,但是注浆加固对限制桩顶回弹的作用不明显;分区开挖要同时安置支护结构,这样才能发挥限制挡土墙侧移的作用;虽然上部结构可以增加结构的空间刚度,但在基坑开挖过程中由于重力二阶效应会增加挡土墙的侧移;将支盘直径增大1.2倍,减小桩顶回弹的作用不明显.Behavior of piles under basal during bottom-up excavation is discussed in detail herein by means of model experiments and finite element analysis. Results from model experiments show that bending moments along pile in bottom-up method are greater than those in top-down method. Results from finite element analyses of single pile show that uplift at the top of pile with enlarged toe is comparatively small during excavation. When soil in the pit is reinforced through jet grouting, lateral displacement of retaining wall decreases apparently, but its effect on uplift at pile top is small. When jump layered excavation is adopted to reduce deflection of retaining wall, the struts must be installed promptly. Although structures above the ground increase the stiffness of the whole structure （the basement and the top structures） , it increases the lateral deformation of retai-ning wall as well because of P -△ effect. For squeezed branch pile, there is no evident change in the uplift at pile top when the diameter of squeezed branch is increased by 1.2 times.

关 键 词：模型试验 有限元 逆作法 桩基础 挡土墙 

分 类 号：TU473.1[建筑科学—结构工程]