上海世博500kV地下变电站超深抗拔桩的设计与分析
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摘要
上海世博500kV大容量全地下变电站地下建筑直径(外径)为130m,地下结构埋置深度34m,正常使用阶段采用桩端深度达82.3m的钻孔灌注桩作为抗拔基础。与浅埋的地下工程相比,该深埋地下结构抗拔桩设计面临的特殊问题是如何反映如此大体量深层地下开挖卸荷对抗拔桩承载特性的影响,主要表现在:深埋地下结构抗拔桩地面试桩开挖段侧摩阻力的扣除;开挖卸荷后桩周土体围压减小对桩基承载力削弱的影响;开挖卸荷基底隆起对桩产生的预拉力。介绍了上海世博500kV地下变电站工程超深抗拔桩的设计,采用现场试验与有限元方法针对上述深层开挖带来的特殊问题进行初步的研究与探讨。理论分析表明,深层开挖对抗拔桩承载性能产生了显著的影响,承载力发生较大削弱且产生较大的预拉力。该抗拔桩的设计采取了相应的对策。
Shanghai World Exposition 500kV high-capacity underground electric substation has the architectural diameter of 130 meters and buried depth of 34 meters,and during the application stage,the cast-in-place pile with the depth of 82.3 meters is used as the uplift foundation.The key problem of uplift piles in deep buried substructure compared to underground engineering with shallow bury depth is how to reflect the influence of deep excavation off-loading on the uplift piles' bearing characteristic and capacity.The influence mainly includes:deduction of the deep substructure uplift piles' side friction resistance in the ground test piles' excavated segment,unfavorable action of the bearing capacity from the pressure looseness of soil around the pile and the pre-tension axial force of piles from the foundation rebound after the excavation.Based on the project of Shanghai World Exposition 500kV underground substation,it has been researched and discussed the three mentioned key problems of bearing uplift piles characteristic in the projects of deep excavation by the field test and finite element method.
Shanghai World Exposition 500kV high-capacity underground electric substation has the architectural diameter of 130 meters and buried depth of 34 meters,and during the application stage,the cast-in-place pile with the depth of 82.3 meters is used as the uplift foundation.The key problem of uplift piles in deep buried substructure compared to underground engineering with shallow bury depth is how to reflect the influence of deep excavation off-loading on the uplift piles' bearing characteristic and capacity.The influence mainly includes:deduction of the deep substructure uplift piles' side friction resistance in the ground test piles' excavated segment,unfavorable action of the bearing capacity from the pressure looseness of soil around the pile and the pre-tension axial force of piles from the foundation rebound after the excavation.Based on the project of Shanghai World Exposition 500kV underground substation,it has been researched and discussed the three mentioned key problems of bearing uplift piles characteristic in the projects of deep excavation by the field test and finite element method.
引文
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[2]杜广印,黄锋,李广信.抗压桩与抗拔桩侧阻的研究[J].工程地质学报,2000,8(1):91-93.
[3]何思明.抗拔桩破坏特性及承载力研究[J].岩土力学,2001,22(3):308-310.
[4]刘金励等.桩基工程手册[M].中国建筑工业出版社,1995.
[5]张栋墚,张书荃,臧延伟.扩底抗拔桩抗拔作用机理的研究[J].铁道建筑,2006,(6):53-55.
[6]杜成斌,任青文.用于接触面模拟的三维非线性接触单元[J].东南大学学报(自然科学版),2001,31(4):1-5.
[7]徐和,刘云云.桩的抗拔承载力预估[J].同济大学学报,1994,22(3):385-389.
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