基于文克勒模型的饱和土中单桩对瑞利波动力响应研究
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摘要
基于Boit饱和多孔介质理论,采用文克勒地基梁模型,研究了表面透水的饱和土介质中顶部固接的桩对瑞利波的横向响应。分别计算了软土和硬土两种情况下不同深度桩的响应、饱和土的孔隙率对桩响应的影响、土介质相对刚度对桩响应的影响、fc-z空间桩响应的分布、桩顶约束条件的影响,并与桩顶自由的结果进行了比较。结果表明,饱和土介质中桩对瑞利波的横向响应受波的频率、土介质性质、桩土刚度比、桩顶约束条件等因素的影响。整体来看,瑞利波对桩的横向影响自上而下大致呈衰减趋势,在地表处影响最大;瑞利波对桩的影响深度随频率的降低而扩大;桩、土之间的水平相对位移幅度与土的孔隙率、相对刚度比均呈正相关关系;同频率下,相对软土地基来说硬土地基中桩受瑞利波的影响较深;顶部固接比顶部自由的桩对瑞利波的响应小。计算结果对工程抗震设计具有参考价值。
Based on Boit's theory of saturated porous medium,the pile lateral responses under Rayleigh wave are studied.The Winkler foundation beam model is adopted and the pile top is fixed in non-watertight saturated soil on surface.The following cases are studied:①pile responses in soft and hard soil in different depth;② pile responses influenced by saturated soil porosity;③pile responses influenced by relative rigidity of soil medium;④pile responses distribution in fc～z space,⑤the effects of constrain conditions,and the results are compared to the results of top free pile.The Results indicate that:the pile lateral responses under Rayleigh wave are affected by frequency,characters of soil medium,pile-soil rigidity ratio and constrain conditions of pile top.Generally,the influence of Rayleigh wave to pile lateral movement appears a descend tendency from top to bottom,and the maximum value appears on the surface;the influencing depth of Rayleigh wave to pile extends when frequency decrease;the relative lateral displacement between pile and soil assumes positive correlativity with porosity and relativity rigidity ratio;under the same frequency,the Rayleigh wave influence on pile in the hard soil is deeper than that in soft soil.;the responses are smaller when the top is consolidated than that is free.The results are useful to engineering anti-seismic design.
Based on Boit's theory of saturated porous medium,the pile lateral responses under Rayleigh wave are studied.The Winkler foundation beam model is adopted and the pile top is fixed in non-watertight saturated soil on surface.The following cases are studied:①pile responses in soft and hard soil in different depth;② pile responses influenced by saturated soil porosity;③pile responses influenced by relative rigidity of soil medium;④pile responses distribution in fc～z space,⑤the effects of constrain conditions,and the results are compared to the results of top free pile.The Results indicate that:the pile lateral responses under Rayleigh wave are affected by frequency,characters of soil medium,pile-soil rigidity ratio and constrain conditions of pile top.Generally,the influence of Rayleigh wave to pile lateral movement appears a descend tendency from top to bottom,and the maximum value appears on the surface;the influencing depth of Rayleigh wave to pile extends when frequency decrease;the relative lateral displacement between pile and soil assumes positive correlativity with porosity and relativity rigidity ratio;under the same frequency,the Rayleigh wave influence on pile in the hard soil is deeper than that in soft soil.;the responses are smaller when the top is consolidated than that is free.The results are useful to engineering anti-seismic design.
引文
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[11]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.
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[13]王立忠,冯永正,柯翰,等.瑞利波作用下成层地基中单桩横向振动分析[J].振动工程学报,2001,14(2):205-210.
[14]蒋东旗,王立忠,陈云敏.远场地震引起的单桩横向位移和内力[J].岩土工程学报,2003,25(2):174-178.
[15]Gazetas G,Dobry R.Single radiation damping model for pile and footings[J].Mech.ASCE,1984,110:937-956.
[16]卢世深.桩基础的计算和分析[M].北京:人民交通出版社,1987.
[17]沈聚敏.抗震工程学[M].北京:中国建筑工业出版社.
[2]Mylonakis G,Gazetas G.Kinematic pile response to vertical P-wave seismic excitation[J].Geotech Geoenv Engng,2002,128(10):860-867.
[3]Militano G,Rajapakse R K N D.Dynamic response of a pile in a multi-layered soil to transient torsional and axial loading[J].Geotechnique,1999,49(1):91-109.
[4]胡昌斌,王奎华,谢康和.考虑桩土耦合作用时弹性支承桩纵向振动特性分析及应用[J].工程力学,2003,20(2):146-154.
[5]Biot M A.Theory of propagation of elastic waves in a fluid-saturated porous solid:I low-frequency range[J].Acoust Society America,1956,28(2):168-178.
[6]Biot M A.Mechanics of deformation and acoustic propagation in porous mediua[J].Appl Phys,1962,33(4):1482-1498.
[7]吴世明.土介质中的波[M].北京:科学出版社,1997:102-104.
[8]胡亚元,王立忠,张忠苗.横观各向同性饱和土中实用波动方程[J].振动工程学报,1998,11(2):170-176.
[9]胡亚元,王立忠,张忠苗.横观各向同性饱和土的Lamb问题[J].浙江大学学报,1997,7(4):357-362.
[10]Zeng X,Rajapakse R K N D.Dynamic axial load transfer from elastic bar to poroelastic medium[J].Journal of Engng Mech,1999,125(9):1048-1055.
[11]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.
[12]Makris N.Soil-pile interaction during the passage of Rayleigh waves:an analytical solution[J].Earthquake Eng Struct Dyn,1994,23:153-163.
[13]王立忠,冯永正,柯翰,等.瑞利波作用下成层地基中单桩横向振动分析[J].振动工程学报,2001,14(2):205-210.
[14]蒋东旗,王立忠,陈云敏.远场地震引起的单桩横向位移和内力[J].岩土工程学报,2003,25(2):174-178.
[15]Gazetas G,Dobry R.Single radiation damping model for pile and footings[J].Mech.ASCE,1984,110:937-956.
[16]卢世深.桩基础的计算和分析[M].北京:人民交通出版社,1987.
[17]沈聚敏.抗震工程学[M].北京:中国建筑工业出版社.
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