直立式混凝土落地声屏障振动放大效应

Vibration Amplification Effect and Mechanism of Vertical Concrete Noise Barriers Sitting on Ground

以普速铁路路侧落地安装直立式混凝土声屏障为研究对象,利用原位试验方法研究了列车运行下屏障板水平及竖向加速度时程和频谱特征,结合悬臂板理论模态分析了屏障板相对其基础的振动放大效应及机理。结果表明,钢轨-轨枕-道床-声屏障基础振动递减,屏障板较其基础加速度平均放大2倍,振级平均增大6 dB,道床和基础竖向振动卓越频率为63.5 Hz,水平向放大显著频段为6~8 Hz和40~50 Hz,竖向放大显著频率为63.5 Hz和160 Hz。理论模态分析显示,屏障板水平向前2阶自振频率为7 Hz和46 Hz,竖向1阶自振频率为170 Hz,说明水平放大效应与其前2阶自振频率相关,竖向放大效应与其1阶自振频率和基础激励频率相关。将屏障板振动响应估算简化为地基土-声屏障动力相互作用耦合振动模型,以考虑其受地基激励强迫振动和自由振动双重影响是合理可行的。

For investigating the vibration amplification effect and mechanism of the concrete noise barriers sitting on the roadside of the railway,the time-frequency characteristics of the vertical and horizontal accelerations of the foundation and the barrier plate during train crossing events are analyzed by in-situ vibration testing.The results show that:the vibration of the rail-sleeper-ballast-noise barrier foundation is monotonously attenuated,and the vibration of the barrier plate is amplified compared with the foundation.The vertical vibration of the barrier foundation is less than that of the horizontal direction,but the vertical amplification effect of the barrier plate is greater than that in the horizontal direction,while the average amplification effect of the amplitude is about 2 times,and the average increase effect of the vibration level is about 6 dB.The theoretical modal analysis shows that the first two natural horizontal frequencies of the barrier plate are 7 Hz and 46 Hz respectively,while the first-order frequency in the vertical plane is 170 Hz.The predominant frequency of the vibration input excitation of the ballast bed and the foundation is 63.5 Hz.It is observed that the high-frequency amplification of the vertical vibration is pronounced,with significant amplification occurring at 63.5 Hz and 160 Hz,and the horizontal vibration is amplified significantly at about 6~8 Hz and 40~50 Hz.The two most significant frequency bands of the horizontal vibration amplification of the barrier plate are close to the horizontal natural frequencies of the first two orders,while the two most significant frequency bands of the vertical vibration amplification align closely with the predominant frequency of the input excitation and the first-order vertical natural frequency of the barrier plate.In summary,the vibration amplification of the barrier plate is influenced by both the frequency of input ex-citation forced vibration and its natural frequency of free vibration.The amplification frequency bands predomi-nantly concentrate on the dominant frequency of the forced vibration and the natural frequency of the barrier plate.The vibration analysis of noise barrier under ground motion excitation caused by train operation can be sim-plified as soil-barrier-interaction coupled vibration model.