轨道交通地表振动局部放大现象成因分析

ANALYSIS ON THE REASONS OF GROUND VIBRATION AMPLIFICATION INDUCED BY RAILWAY TRAFFIC

为研究轨道交通振动产生地表局部放大现象原因,利用地表落锤试验和半空间位移格林函数解析解,分析了振源位于地面和地下两种情况下单频振动的地表响应传播规律。结果表明:1)当振源位于地面时,单一频率的地表振动响应幅值随距离呈现波浪形衰减,波动间隔与其自身频率相关。地表体波和瑞利波衰减速度不同而引起的振动叠加效应是造成上述现象的主要原因。2)当振源埋置于地下时,单一频率的地表振动响应将在距振源与埋深大致相当的近场处产生一个明显的波峰或波谷,在远场衰减规律与振源位于地面的情况近似。

To study the reasons which cause the ground vibration amplification induced by railway traffic,the propagation laws of ground vibration responses for each frequency are analyzed with the help of both the drop-weight test and analytical solution of a displacement Green’s function in a halfspace.The conditions include that the vibration source are on the surface and underground.Results show that： 1） when the vibration source applies on the surface,the ground vibration of each frequency attenuates with a fluctuation.There is an interval of fluctuation,which has the relationship with its frequency.Due to the difference of attenuation speeds of body wave and Rayleigh wave,the superposition of the two kinds of the waves mainly induce the phenomenon of fluctuant attenuation.2） When the vibration source applies underground,there is an obvious wave crest or trough in an adjacent field,whose location is related to the embedded depth of source.In a far field,the similar fluctuant attenuation with the first condition can be found.