层状地基空沟被动隔振分析

Analysis of Passive Vibration Isolation Using Open Trench in Layered Ground

摘要:

基于薄层法在研究层状介质中波的传播问题的高效性，边界单元法处理无限域问题的精确性，结合两者提出层状地基二次形函数薄层法基本解答，建立了基于层状半空间薄层法位移基本解答的半解析动力边界元法，可以有效的分析多层场地的动力问题，解决土一结构动力相互作用问题。同时对上软下硬的典型层状地基中的空沟被动隔振效果进行了详细的分析。研究表明：对于上软下硬地基中空沟被动隔振，为取得与匀质弹性半空间中连续屏障隔振同样的效果，需要更深的深度，同时振幅衰减曲线会出现明显的振荡现象；为使隔振效果满足Richart要求，当表层土归一化深度H〈1．0时，空沟归一化深度T应大于1．3，而1．0≤H≤2．0时，T应当大于1．8。

Abstract:

Thin layered method （TLM） is very efficient to study the wave propagation in layered media, and boundary element method （BEM） is very precise to solve infinite domain problems. After combining the advantages of two methods, the semi-analytical BEM model is erected by TLM based on the second shape function, on which the Green function is as fundamental solution of stratified half-space. This model can be effectively used to analyze the dynamic soil-structure interactions in layered ground. The effectiveness of passive vibration isolation by open trench in upper soft-layer and lower stiff-layer visco-elastic foundations is analyzed in detail. The results show that （1） in layered soils the deeper trenches are required to obtain the same effectiveness with screening isolation in homogeneous soils （soft-layer and lower stiff-layer in half-plane）, and the amplitude reduction curve is obviously vibrated, （2） if the normalized depth of topsoil is less than 1.0, the normalized depth of open trenches should be greater than 1.3 in order to provide satisfactory screening effectiveness, （3） if normalized depth of topsoil is greater than or equal to 1.0 and less than or equal to 2.0, the normalized depth of open trenches should be greater than 1.8.