桩–土动力相互作用问题中桩身刚度的影响效应研究
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摘要
通过开展2类刚度差异较大的桩基础的离心机动力模型试验,系统地讨论柔性桩和刚性桩的地震反应差异,以及周围土体对桩体的不同作用效应。对于柔性桩,周围土体的作用主要体现在对桩的约束效应上;然而对于刚性桩,土体更大程度上对桩体施加附加惯性力的作用,以致桩筏基础的周期明显高于无土时的周期;针对柔性桩和刚性桩显著的地震反应差异,巧妙地提出用桩筏结构自振频率wp r界定两者的行为,可为今后类似研究提供参考。
By conducting the centrifuge dynamic tests coverage to two kinds of piles with great stiffness difference,This paper investigated that there exist some quite different characteristics between behavior of flexible and stiff piles during earthquake shakings.For the flexible piles,the bending moment drops to a very small value below the changeover point.This is similar to the bending moment distribution curves for laterally loaded piles,and suggests that,for flexible piles,the clay beneath a certain depth is able to provide lateral support for the pile.On the other hand,for the stiff piles,the bending moment changes over at a much larger depth indicating that lateral support is not effective until much deeper.There is also much larger reverse moment below the changeover depth.This is quite different from the typical moment distribution of laterally loaded piles,the surrounding clay effect on the pile mainly focus on the providing additional inertia forces.Finally,a skillful parameter of pile-raft native frequency was presented herein to quantify pile flexibility.
By conducting the centrifuge dynamic tests coverage to two kinds of piles with great stiffness difference,This paper investigated that there exist some quite different characteristics between behavior of flexible and stiff piles during earthquake shakings.For the flexible piles,the bending moment drops to a very small value below the changeover point.This is similar to the bending moment distribution curves for laterally loaded piles,and suggests that,for flexible piles,the clay beneath a certain depth is able to provide lateral support for the pile.On the other hand,for the stiff piles,the bending moment changes over at a much larger depth indicating that lateral support is not effective until much deeper.There is also much larger reverse moment below the changeover depth.This is quite different from the typical moment distribution of laterally loaded piles,the surrounding clay effect on the pile mainly focus on the providing additional inertia forces.Finally,a skillful parameter of pile-raft native frequency was presented herein to quantify pile flexibility.
引文
[1]马亢.地震条件下桩筏基础与土的动力相互作用机制研究[博士学位论文][D].成都:四川大学,2010.(MA Kang.Dynamic pile-raft-soil interaction in soft clay condition during earthquakes[Ph.D.Thesis][D].Chengdu:Sichuan University,2010.(in Chinese))
[2]BANERJEE S,GOH S H,LEE F H.Response of soft clay strata and clay-pile-raft systems to seismic shaking[J].Journal of Earthquake and Tsunami,2007,1(3):233–255.
[3]POULOS H G,DAVIS E H.Pile foundation analysis and design[M].[S.l.]:John Wiley and Sons,1980:455–481.
[4]GAZETAS G.Seismic response of end-bearing single piles[J].Soil Dynamics and Earthquake Engineering,1984,3(2):82–93.
[5]NIKOLAOU S,MYLONAKIS G,GAZETAS G,et al.Kinematic pile bending during earthquakes:analysis and field measurements[J].Geotechnique,2001,51(5):425–440.
[6]BROMS B B.Lateral resistance of piles in cohesive soils[J].Journal of Soil Mechanics and Foundation Division,1964,90(3):123–156.
[7]BUDHU M,DAVIES T.Nonlinear analysis of laterally loaded piles in cohesionless soils[J].Canadian Geotechnical Journal,1987,24(2):289–296.
[8]BIERSCHWALE M,COYLE H,BARTOWKEWITZ R.Lateral load tests on drilled shafts founded in clay[C]//Proceedings of a Session at the ASCE National Convention:Drilled Piers and Caissons Held Oct..[S.l.]:[s.n.],1981:98–113.
[9]POULOS H,HULL T.The role of analytical geomechanics in foundation engineering[C]//Proceedings of the 1989 Foundation Engineering Conference.[S.l.]:[s.n.],1989:1 578–1 606.
[10]CARTER J,KULHAWY F.Analysis and design of drilled shaft foundations socked into rock[R].New York:Cornell University Press,1988.
[11]《桩基工程手册》编写委员会.桩基工程手册[M].北京:中国建筑工业出版社,1995:225–235.(Pile Foundation Engineering Handbook Committee.Pile foundation engineering handbook[M].Beijing:China Building Industry Press,1995:225–235.(in Chinese))
[2]BANERJEE S,GOH S H,LEE F H.Response of soft clay strata and clay-pile-raft systems to seismic shaking[J].Journal of Earthquake and Tsunami,2007,1(3):233–255.
[3]POULOS H G,DAVIS E H.Pile foundation analysis and design[M].[S.l.]:John Wiley and Sons,1980:455–481.
[4]GAZETAS G.Seismic response of end-bearing single piles[J].Soil Dynamics and Earthquake Engineering,1984,3(2):82–93.
[5]NIKOLAOU S,MYLONAKIS G,GAZETAS G,et al.Kinematic pile bending during earthquakes:analysis and field measurements[J].Geotechnique,2001,51(5):425–440.
[6]BROMS B B.Lateral resistance of piles in cohesive soils[J].Journal of Soil Mechanics and Foundation Division,1964,90(3):123–156.
[7]BUDHU M,DAVIES T.Nonlinear analysis of laterally loaded piles in cohesionless soils[J].Canadian Geotechnical Journal,1987,24(2):289–296.
[8]BIERSCHWALE M,COYLE H,BARTOWKEWITZ R.Lateral load tests on drilled shafts founded in clay[C]//Proceedings of a Session at the ASCE National Convention:Drilled Piers and Caissons Held Oct..[S.l.]:[s.n.],1981:98–113.
[9]POULOS H,HULL T.The role of analytical geomechanics in foundation engineering[C]//Proceedings of the 1989 Foundation Engineering Conference.[S.l.]:[s.n.],1989:1 578–1 606.
[10]CARTER J,KULHAWY F.Analysis and design of drilled shaft foundations socked into rock[R].New York:Cornell University Press,1988.
[11]《桩基工程手册》编写委员会.桩基工程手册[M].北京:中国建筑工业出版社,1995:225–235.(Pile Foundation Engineering Handbook Committee.Pile foundation engineering handbook[M].Beijing:China Building Industry Press,1995:225–235.(in Chinese))
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