上海中心大厦大直径超长灌注桩现场试验研究  

Field loading tests on large-diameter and super-long bored piles of Shanghai Center Tower

作　　者：王卫东[1,2] 李永辉[1] 吴江斌[2] 

机构地区：[1]同济大学地下建筑与工程系,上海200092 [2]华东建筑设计研究院,上海200002

出　　处：《岩土工程学报》2011年第12期1817-1826,共10页Chinese Journal of Geotechnical Engineering

基　　金：住房与城乡建设部项目(2009-K3-5)

摘　　要：中国在建第一高楼上海中心大厦(632 m)采用了直径为1 m、桩端埋深88 m的大直径超长灌注桩,有别于金茂大厦(420 m)、上海环球金融中心(492 m)另两栋超高层建筑所采用的钢管桩。通过现场试桩验证成桩可行性及承载力取值,试桩载荷试验加载至极限,采用分布式光纤量测桩身应变,同时为研究上海软土地区大直径超长灌注桩承载特性及荷载传递机理提供了有价值的数据。试验结果表明:试桩破坏前,Q–s曲线近似为线性,破坏时,桩体发生刺入变形;桩侧桩端联合后注浆桩与桩端后注浆桩在侧摩阻力分布及发挥性状方面存在显著差异;黏性土中桩侧摩阻力充分发挥所需桩土相对位移小于5 mm,砂性土中小于10 mm;桩土相对位移超过极限位移后,埋深较浅的黏性土中由于桩土相对位移大出现明显的软化现象;与规范值相比,有效桩长范围内浅部土层中桩侧摩阻力小于规范取值下限,深部土层中桩侧摩阻力达规范取值上限的2倍以上;试桩端阻比较小,表现出摩擦型桩特性;桩身压缩占桩顶沉降95%左右,桩顶沉降主要由桩身压缩产生。试桩试验为上海软土地区600 m超高层建筑首次采用灌注桩提供指导和技术支持。Large-diameter and super-long bored piles with a diameter of 1000 mm and a length of 88 m are adopted for Shanghai Center Tower,which is the highest building（632 m） under construction in China.This pile type is different from that adopted in the adjacent Jinmao Tower（420 m） and Shanghai World Financial Center（492 m）.As test piles are loaded to failure and measured by distributed optical fiber,the test results are valuable to study the bearing capacity and load transfer mechanism of large-diameter and super-long bored piles in Shanghai soft soils.The results show that the load-movement curves of the piles are almost linear before achieving plunging failure.Distribution and characters of pile shaft friction of shaft and toe post-grouted piles are different from those of only toe post-grouted piles.The ultimate pile-soil relative movements are less than 5 mm and 10 mm to bring pile shaft resistances into full play in clay and sand,respectively.After that,the pile shaft friction in the shallow clay is degraded.The pile shaft friction is lower in the shallow soils and more than 2 times in the deep soils than the empirical value in the local specifications.Since the toe resistance takes a small part of the ultimate load,the piles behave as friction piles.The compression of the piles accounts for about 95% of the pile head movements under the ultimate load.The pile tests provid guidance and technical support for bored piles used for 600 m high-rise buildings in Shanghai soft soils.

关 键 词：大直径超长灌注桩 桩侧注浆 桩端注浆 双层钢套管 现场试验 

分 类 号：TU473.1[建筑科学—结构工程]