饱和土体中排桩对移动荷载的被动隔振效果分析

Analysis of passive isolation of vibration due to moving loads using pile rows embedded in a poroelastic half space

利用Muki和Sternberg的虚拟桩法,研究了饱和土体地基中排桩对移动荷载引起振动的被动隔振效果。隔振桩作为一维杆,饱和土体满足Biot理论。利用已有的移动荷载作用下的饱和土体的自由波场解及饱和土体内部受竖向圆形分布荷载作用下的基本解,建立了频域内土-桩的第2类Fredholm积分方程。通过Fourier逆变换得到时间域内评价隔振效果的振幅比。与已知文献结果相比较,验证了方法的正确性。数值结果表明,荷载速度对排桩的隔振效果有一定影响,即在相同隔振系统情况下,单排桩对低速荷载引起振动的隔振效果比高速移动荷载效果好。同时,较高速时的最佳桩长比低速时要短。

Following Muki and Sternberg＇s method, the passive isolation of vibration due to moving loads using pile rows embedded in a poroelastic half space is investigated. The responses of the poroelastic half space is governed by Biot＇s theory, while the pile is described by the 1D bar vibration theory. Using the free field solution for a moving load applied on the surface of a poroelastic half space and the fundamental solution for a harmonic circular patch load applied to the poroelastic half space, the second kind of Fredholm integral equations in the frequency domain describing the dynamic interaction between pile rows and the poroelastic half space is developed. The time domain responses for the pile-soil system can be obtained by using IFFT arithmetic, then, the isolation vertical vibration effectiveness is obtained. Comparison of our results with some known results shows that our results are in a good agreement with existing ones. Numerical results of this study show that velocity of moving loads has an important impact on the vibration isolation effect of pile rows. The same pile row has a better vibration isolation effect for the lower speed moving loads than for the higher speed ones. Also, the optimal length of piles for higher speed moving loads is shorter than that for lower speed moving loads.