不均匀饱和土中变波阻抗桩的纵向振动特性
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摘要
为揭示饱和土中桩的纵向振动特性,文章建立了不均匀饱和土中变波阻抗桩的纵向振动模型。利用Laplace变换,得到了土层平面应变模型下对桩身的动力阻抗,并求得了桩身任意段的动力响应;利用传递矩阵,给出了桩顶复刚度的解析表达式;阐明了单相土模型的不足,并分析了桩身缺陷及饱和土渗透性对桩动力特性的影响。结果表明:采用单相土模型会低估桩顶低频段的动刚度,对动阻尼影响较小,一定程度上说明了土体模型对分析桩动力特性的重要性;桩身存在缺陷会使桩顶的动刚度明显减小,动阻尼增大;饱和土渗透性变差会有效增大缺陷桩的动刚度,减小桩的共振频率,并减缓动阻尼随频率变化的增长速率。
In order to reveal the longitudinal vibration characteristics of piles in saturated soils, the longitudinal vibration model of piles with variable wave impedance in inhomogeneous saturated soils is established. Using the Laplace transform, the dynamic impedance of the pile is obtained with the plane strain model of soils and the dynamic response of the pile is obtained. The analytical expression of the complex stiffness of the pile top is presented by using the transfer matrix. The deficiency of the single-phase model of soil is described, and the influence of the defects of the pile and the permeability of saturated soil on the dynamic characteristics of the pile is analyzed. The results show that if the single-phase model of soil is applied, the dynamic stiffness of the pile top in the low frequency section will be underestimated, while the dynamic damping changes a little, which shows the importance of the soil model to analyze the dynamic characteristics of the pile to some extent; the dynamic stiffness of defective pile can be reduced significantly, but its damping increases; with the decrease of the permeability of saturated soil, the dynamic stiffness of the defective pile becomes large, but the resonance frequency of the pile and the growth rate of dynamic damping with frequency decrease.
In order to reveal the longitudinal vibration characteristics of piles in saturated soils, the longitudinal vibration model of piles with variable wave impedance in inhomogeneous saturated soils is established. Using the Laplace transform, the dynamic impedance of the pile is obtained with the plane strain model of soils and the dynamic response of the pile is obtained. The analytical expression of the complex stiffness of the pile top is presented by using the transfer matrix. The deficiency of the single-phase model of soil is described, and the influence of the defects of the pile and the permeability of saturated soil on the dynamic characteristics of the pile is analyzed. The results show that if the single-phase model of soil is applied, the dynamic stiffness of the pile top in the low frequency section will be underestimated, while the dynamic damping changes a little, which shows the importance of the soil model to analyze the dynamic characteristics of the pile to some extent; the dynamic stiffness of defective pile can be reduced significantly, but its damping increases; with the decrease of the permeability of saturated soil, the dynamic stiffness of the defective pile becomes large, but the resonance frequency of the pile and the growth rate of dynamic damping with frequency decrease.
引文
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[6] 崔春义,张石平,杨刚,等.饱和黏弹性半空间中摩擦桩的竖向振动[J].土木建筑与环境工程,2015,37(2):28-33.
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[9] 杨骁,唐洁.成层饱和土中考虑横向惯性的单桩纵向振动[J].岩土力学,2013,34(6):1560-1566.
[10] 刘东甲.不均匀土中多缺陷桩的轴向动力响应[J].岩土工程学报,2000,22(4):391-395.
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[2] 刘林超,杨骁.基于多孔介质理论的饱和土-桩纵向耦合振动研究[J].土木工程学报,2009,42(9):89-95.
[3] DE BOER,LIU Z F.Plane waves in a semi-infinite fluid saturated porous solid [J].Transport in Porous Media,1994,16(2):147-173.
[4] DE BOER,LIU Z F.Propagation of acceleration waves in incompressible saturated porous solid [J].Transport in Porous Media,1995,21(2):163-173.
[5] 刘林超,杨骁.基于薄层法的饱和土桩纵向振动研究[J].岩土力学,2010,31(1):92-98.
[6] 崔春义,张石平,杨刚,等.饱和黏弹性半空间中摩擦桩的竖向振动[J].土木建筑与环境工程,2015,37(2):28-33.
[7] 李强,王奎华.成层饱和土中桩纵向振动特性研究及应用[J].工程力学,2007,24(10):144-149.
[8] 张智卿.饱和非均质土中桩土耦合扭转振动理论研究[D].杭州:浙江大学,2008.
[9] 杨骁,唐洁.成层饱和土中考虑横向惯性的单桩纵向振动[J].岩土力学,2013,34(6):1560-1566.
[10] 刘东甲.不均匀土中多缺陷桩的轴向动力响应[J].岩土工程学报,2000,22(4):391-395.
[11] 刘东甲,刘煜洲,王杰英.扭转波应用于低应变动力测桩的理论研究[J].岩土工程学报,2003,25(3):283-287.