摘要
某超高层建筑高度230 m,由于其上部结构荷载大,对地基承载力和沉降控制要求高,且场地地层以粉质黏土和粉土为主,夹有粉砂及细砂层,所以采用超长灌注桩基础。先后开展了两组现场试桩试验,A组桩桩径为1 m,以埋深为93 m的细砂层作为桩端持力层,采用桩端和6道桩侧后注浆;B组桩桩径为1 m,以埋深为78 m的粉质黏土层作为桩端持力层,采用桩端和2道桩侧后注浆。现场试桩实测结果显示:A、B组桩均满足承载力及沉降控制要求,但B组桩更加经济合理,且B组桩比A组桩更利于桩端阻力的发挥;埋深23 m以上桩侧摩阻力增强系数小于勘察报告中的建议取值,埋深40~80 m桩侧摩阻力增强系数与勘察报告中的建议取值吻合较好,而A组桩桩端阻力增强系数明显小于勘察报告中的建议取值,B组桩桩端阻力增强系数明显高于勘察报告中的建议取值,超长桩设计中应充分考虑泥皮引起的桩侧摩阻力软化和注浆后的桩侧摩阻力及桩端阻力增强作用。
The building height of a project is 230 m.Large load of superstructure means high requirements for foundation bearing capacity and settlement control.The site stratigraphy is mainly composed of chalky clay and silt,interspersed with layers of chalk and fine sand.It is proposed to adopt super-long bored piles foundation,the design and construction of pile foundations is difficult.Two groups of pile tests were carried out.The pile diameter of pile A was 1 m.The bearing layer was fine sand layer and its burial depth was 93 m.The pile end and 6 pile side grouting were used.The diameter of pile B was 1 m.The bearing layer was silty clay layer and its burial depth was 78 m.The pile end and 2 pile side grouting were used.The field test results show that pile A and B both meet the requirements of bearing capacity and settlement control,but pile B is more economical and reasonable.Pile B is more favourable than pile A for pile end resistance.The enhancement coefficient of lateral friction resistance of piles above 23m depth is less than the recommended value in the investigation report,but the enhancement coefficient of lateral friction resistance of piles with burial depth of 40~80 m is in good agreement with the recommended value in the investigation report.The resistance enhancement factor at the end of pile A is significantly less than that recommended in the investigation report,while the factor of pile B is significantly higher than that recommended in the investigation report.The softening of the pile lateral friction resistance caused by mud skin and the enhancement of the pile lateral friction resistance and end resistance after grouting should be considered in the design of the super-long bored pile.
作者
吴江斌
王阿丹
黄昱挺
魏家斌
WU Jiangbin;WANG Adan;HUANG Yuting;WEI Jiabin(Underground Space&Engineering Design&Research Institute,East China Architecture Design&Research Institute Co.,Ltd,Shanghai 200011,China)
出处
《建筑结构学报》
EI
CAS
CSCD
北大核心
2023年第S02期367-374,共8页
Journal of Building Structures
基金
上海市青年科技启明星计划(22QB1400500)
上海市科学技术委员会科技攻关项目(22DZ1202900)。
关键词
超高层建筑
超长灌注桩
优化设计
试桩试验
后注浆
super high-rise building
super-long bored pile
optimal design
pile test
post grouting
