周期性排桩设计频段隔振原理性试验研究

针对目前基于带隙理论开展的周期性隔振排桩性能研究偏重于解析理论分析和数值仿真计算的现状，采用原理性试验的方法，验证了周期性隔振排桩的衰减域特性。试验设计了4种工况：分别考虑了空心钢管桩和填土钢管桩两种排桩类型，以及六角晶格和正方晶格两种周期性布置方式。激振采用脉冲荷载激励，将隔振工况与无桩基本工况进行比较，对周期性排桩的振动衰减域进行了测试和分析，并与带隙理论计算的频率带隙结果进行对比。研究表明：在理论计算带隙范围内，各工况下实测衰减水平均在50%以上，最高达到98%。表明了周期排桩对特定频带的振动阻隔实际效果明显，隔振表现突出，证实了理论分析的有效性。周期排桩对水平方向的振动衰减优于竖直方向；从趋势上看，在其他条件相同时，六角晶格布置的周期排桩，其振动衰减水平优于正方晶格布置；桩内填土可有效增加六角晶格布置钢管桩的首阶带隙及衰减域宽度，有效降低正方晶格布置钢管桩的首阶带隙及衰减域起始频率。对应于试验的工程实际尺寸在0～80 Hz频段内出现多条带隙，并且最低可达20 Hz以下，这表明，基于带隙理论进行周期隔振排桩设计，在地铁列车振动环境影响的特征频段隔离或衰减中，具有广泛的应用前景。

Elementary experimental investigation of the periodic piles for vibration isolation of design frequency range

The current research on the periodic piles for vibration isolation based on the method of band gap mainly focused on theoretical and numerical analysis. In this paper, the method of principle experiment was adopted to validate the characteristics of attenuation zone of the periodic piles for vibration isolation. Four experimental cases were designed to consider two types of periodic piles (i.e., hollow steel piles and periodic hollow steel piles filled with soil) and two types of periodic layout (i.e., a hexagonal configuration and a square configuration). With the excitation of impulsive loads, the experimental cases with vibration isolation measures were compared to those without vibration isolation measures. Vibration attenuations of the periodic piles in various experimental cases were measured, analyzed and compared with theoretical band gaps. The measured vibration response in various experimental cases was greatly attenuated within the band gaps of theoretical calculations. The levels of attenuation were above 50% and the highest one was up to 98%. Both the attenuation effect and vibration isolation performance were greatly achieved, and thus the effectiveness of theoretical analysis is verified. The horizontal level of vibration attenuation of the periodic piles is better than the vertical. From this trend, with the same conditions, the vibration attenuation level of periodic piles in a hexagonal configuration was better than those in a square configuration. Moreover, soil-filling could effectively increase the width of the initial band gap and the attenuation zone of periodic steel pipe piles arranged in a hexagonal configuration, but reduce the lower bound frequency of the initial band gap and the attenuation zone of periodic steel pipe piles arranged in a square configuration. By analysing the band gap of periodic piles that were approximate to actual engineering dimensions corresponding to the periodic piles in the experimental cases, it is found that there are several band gaps appearing in the frequency range of 0-80 Hz which can be lower than 20 Hz. This study further illustrates that an objective frequency range can be designed to be isolated by periodic piles, and the periodic piles based on band gap theory can have a broad application prospect in the vibration isolation induced by metro train.