紧邻地铁车站地下空间楼层振动效应测试评价

地铁列车运行引发车站临近地下空间楼层振动,对其理论完善有赖于现场实测及数据分析。本文以紧邻地铁车站的某大型地下空间为例,基于Imote2无线传感器网络平台,对地铁列车进站-停靠-出站阶段地下空间楼层振动效应进行了实测。分别获得了加速度时程谱与频谱,计算出楼层测区内的Z振级分布,并对三分之一倍频程各中心频率的分频振级分布特征进行了分析。结果表明:楼层钢筋混凝土楼板在弹性波传播方向上存在阻尼作用,但对于不同频率的弹性波,其阻尼耗散程度不同;弹性波在楼层内传播过程中,不仅存在振幅随传播距离增大而衰减的现象,还存在复杂的波动干涉行为,并导致振动效应放大区的出现;测区楼板被激发出的前两阶固有频率分别为1.60 Hz与3.15 Hz,二者的分频振级均小于60 dB,对人体健康造成的潜在不利影响较小;为降低楼层振动效应对建筑体及附属设施的不利影响,可考虑采取进站提前减速、出站推迟加速的方法,亦可考虑在局部地铁道床采取减、隔振等措施,集中耗散高频振动能量。

Measurement and Evaluation on Vibration Effects of Underground Space Adjoining the Subway Station

The operation of subway trains induces vibrations in the floors of adjoining underground space, and the improvement of the theory about it depends on both the on-site measurement and data analysis. Based on the Imote2 wireless sensor network platform, we researched the vibration effects in the floor of one underground space during the arrival-stop-departure period of the subway train. The acceleration data in both time and frequency domains were obtained for the calculation of the distribution of Z vibration levels within the measurement zone in the floor area. Moreover, the distribution characteristics of frequency vibration level on all of 1/3-octave center frequencies were characterized. Investigation results show that, first, along the direction of elastic wave propagation, the reinforced concrete floor yields a damping effect, but the dissipative degrees differ for the elastic waves with different frequencies. Second, during the process of elastic wave propagation, not only the phenomenon of vibration amplitude attenuating along the propagation distance occurs, but also complex wave interference behaviors are exhibited, generating the occurrence of vibration amplifying zone. Thirdly, the first two natural frequencies of the floor in measurement zone, excited by the subway vibration source, are 1.60 Hz and 3.15 Hz, respectively, and the frequency vibration level are all less than 60 dB, yielding a potential minor negative influence on the human body. Finally, in order to reduce the negative influences of the floor vibration effect on both facilities and accessories, the methods of early deceleration when arriving and late acceleration when departing may be considered to be used; also, the high frequency vibration energy can be considered to be intensively dissipated using attenuation or isolation devices under local subway ballast beds.