饱和土中端承桩非完全黏结下的竖向振动特性
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摘要
建立了考虑桩土非完全黏结条件下端承桩在饱和土中竖向振动的模型,将土视为线弹性饱和多孔介质,桩简化为一维弹性杆件。通过引入势函数,采用分离变量法对饱和两相介质动力固结方程解耦,求得桩受任意激振力作用下的桩土耦合系统解析解。计算结果表明,桩土非完全黏结条件下桩振动引起的饱和土中孔压分布略小于完全黏结条件下的,其影响幅度随激振频率的增加而增大,随渗透系数的减小而增加。桩顶的频率和时域响应研究结果表明,桩土接触面条件对桩顶动力响应有显著影响。经分析,增大击发能量使桩土出现非完全黏结状态可以加大有效测桩深度。
The vertical vibration of end bearing piles embedded in saturated soil layer is investigated theoretically.The imperfect contact between pile and soil is considered.The pile is simplified as a 1-D elastic staff and the soil is regarded as a linear saturated isotropic porous medium.By using variable separation method the governing differential equations of saturated soil are decoupled by introducing the potential function.Under the assumption of imperfect contact between pile and soil the dynamic response of pile to arbitrary vertical load is obtained.Numerical analysis shows that the pore pressure caused by pile vibration under slippage condition is bigger than that of perfect contact and this effect increases with the increase of frequency as well as the decrease of permeability.Numerical results obtained from frequency domain and time domain also indicate that the contact condition between pile and soil has significant influence on the dynamic response of pile vertical vibration.It is concluded that to increase the impact energy for facilitating the imperfect contact can increase the effective depth of pile dynamic test.
The vertical vibration of end bearing piles embedded in saturated soil layer is investigated theoretically.The imperfect contact between pile and soil is considered.The pile is simplified as a 1-D elastic staff and the soil is regarded as a linear saturated isotropic porous medium.By using variable separation method the governing differential equations of saturated soil are decoupled by introducing the potential function.Under the assumption of imperfect contact between pile and soil the dynamic response of pile to arbitrary vertical load is obtained.Numerical analysis shows that the pore pressure caused by pile vibration under slippage condition is bigger than that of perfect contact and this effect increases with the increase of frequency as well as the decrease of permeability.Numerical results obtained from frequency domain and time domain also indicate that the contact condition between pile and soil has significant influence on the dynamic response of pile vertical vibration.It is concluded that to increase the impact energy for facilitating the imperfect contact can increase the effective depth of pile dynamic test.
引文
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[2]王建华,陆建飞,沈为平.半空间饱和土在内部简谐垂直力作用下的Green函数[J].水利学报,2001,(3):54-57.
[3]Zeng X,Rajapakse PKND.Dynamic axial load transfer from elastic bar to poroelastic medium[J].J.of Engng.Mech.,1999,125(9):1048-1055.
[4]李强,王奎华,谢康和.饱和土中端承桩纵向振动特性研究[J].力学学报,2004,36(4):435-442.
[5]Nogami T,Konagai K.Time domain axial response of dynamically loaded single piles[J].J.Engng.Mech.,1986,112(11):1241-1252.
[6]Nogami T,Konagai K.Dynamic response of vertically loaded nonlinear pile foundations[J].J.Geotech.Engng.,1986,113(2):147-160.
[7]Meymand P J.Shaking table scale model tests of nonlinear soil_pile_superstructure interaction in soft clay[D].Universityof Californa.Berkeley,1998.
[8]孔德林,栾茂田,杨庆.桩土相互作用分析中的动力Winkler模型研究评述[J].世界地震工程,2005,21(1):12-17.
[9]Nogami T,Ren F Z,Chen J W,et al.Vertical vibration of pile in vibration_induced excess pore pressure field[J].J.Geotech.Geoenv.Engng.,1997,123(5):422-429.
[10]Biot M A.Theory of propagation of elastic waves in a fluid_saturated porous solid I.low_frequency range[J].J.Acoust.Society America,1956,28(2):168-178.
[11]Biot M A.Mechanics of deformation and acoustic propagation in porous media[J].J.Appl.Phys.,1962,33(4):1482-1498.
[12]汪越胜,于桂兰,章梓茂,等.复杂界面(界面层)条件下的弹性波传播问题研究综述[J].力学进展,2000,30(3):378-390.
[13]李强,王奎华,谢康和.饱和土中大直径嵌岩桩纵向振动特性研究[J].振动工程学报,2005,18(4):500-505.
[14]中国工程建设标准化协会建筑振动专业委员会.建筑振动工程手册[M].北京:中国建筑工业出版社,2002.
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