周期性多层排桩低频隔振及衰减域拓宽研究

Study of Low⁃frequency Vibration Isolation and Attenuation Domain Broadening for Periodic Multilayer Pile Barriers

针对10 Hz以下的低频轨道交通振动,提出一种截面带孔软体层多层桩,通过频散曲线研究软体层填充率对带隙的影响;通过频域分析,研究排桩数量影响,并提出带隙中心频率连续的排桩组合方式来拓宽衰减域;最后,通过时域曲线研究组合排桩对宽低频振动的衰减性能。结果表明:降低软体层填充率可以有效降低带隙频率,极易获得10 Hz以下的低频带隙;当软体层填充率大于80%时带隙频率随软体层填充率减小而迅速减小,当软体层填充率小于80%时带隙频率随软体层填充率减小而缓慢减小;中心频段连续时多类排桩组合频率响应曲线和单类排桩类似,可以平稳拓宽衰减域,且桩基类型越多衰减域越宽;组合多层排桩可以对宽低频振动波产生良好阻隔效应,隔振的根本原因是大部分入射波在排桩局域共振作用下转变成了反射波。

Multi layer piles with perforated soft layers were proposed for low-frequency rail transit vibrations below 10 Hz,and the influence of soft layer filling rate on bandgap was studied through dispersion curves.Through frequency domain analysis,the influence of the number of pile rows was studied,and a pile row combination method with continuous bandgap center frequency was proposed to broaden the attenuation domain.Finally,the attenuation performance of composite pile arrangement on wide and low frequency vibration was studied through time-domain curves.The results show that reducing the filling rate of the soft layer can effectively reduce the bandgap frequency and easily obtain low-frequency bandgaps below 10 Hz.When the filling rate of the soft layer is greater than 80%,the bandgap frequency decreases rapidly with the decrease of the filling rate of the soft layer.When the filling rate of the soft layer is less than 80%,the bandgap frequency decreases slowly with the decrease of the filling rate of the soft layer.When the central frequency band is continuous,the frequency response curve of the combination of multiple types of pile rows is similar to that of a single type of pile row,which can smoothly broaden the attenuation domain,and the more types of pile foundations,the wider the attenuation domain.The combination of multi layer piles can produce a good barrier effect on wide and low-frequency vibration waves,and the fundamental reason for isolation is that most of the incident waves transform into reflected waves under the local resonance of the piles.