三维层状地基排桩远场被动隔振分析

THREE-DIMENSIONAL ANALYSIS OF FAR-FIELD PASSIVE VIBRATION ISOLATION FOR ROW OF PILES IN LAYERED FOUNDATION

屏障隔振是治理振动污染一种极为有效的手段,被广泛应用到工程实际中,但目前关于屏障隔振的研究主要基于弹性均质半空间条件,而对更符合实际的层状地基屏障隔振问题则鲜有报道,尤其是层状地基中复杂的三维非连续屏障隔振问题。将三维直角坐标下的二次形函数薄层法基本解答代入弹性动力边界积分方程,得到薄层法半解析边界元法,分析不同桩长和不同桩土剪切模量比对排桩隔振效果的影响。结果表明:(1)上软下硬层状地基中的排桩被动隔振,排桩的有效深度为2.5左右,远大于排桩在均质地基中的有效深度1.0;(2)对于上硬下软层状地基,排桩的有效深度为2.0左右,小于上软下硬地基中排桩的有效深度;(3)当桩与表层土剪切模量比5≤G*≤30时,随G*的增加,排桩隔振效果增加明显。

Wave barrier has been widely employed in engineering as an effective way to harness vibration pollution. Studies on vibration isolation using barrier are mainly based on elastic half-space soil at present, and little attention is paid to the vibration isolation in layered foundation in accordance with reality. The semi- analytical boundary element method（BEM） with the basic solution of thin layered method（TLM） using orthogonal coordinates and the second shape function was employed to investigate the isolation effect of passive wave barriers in layered foundation. The numerical results indicate that： （1） Based on the numerical study of a upper-soft lower-hard foundation, the normalized depth of piles in row as passive vibration isolation is about 2.5 for providing satisfying vibration isolation effect, which is greater than that in homogeneous ground（1.0）; （2） The normalized depth of piles in row is about 2.0 for a upper-hard lower-soft foundation; （3） If the ratio of shear modulus of pile to that of topsoil, G^＊ meets the requirement of5≤G＊≤30, the vibration isolation effect obviously increases with G^＊.