隧道对地表地震动放大作用的研究

Effects of a Tunnel on Ground Motion Amplification

场地条件对地震波传播有较大的影响,浅埋隧道改变了近地表的场地条件,势必会对地面地震动产生一定的影响,进而影响临近地面结构的地震响应。文章选取Ricker小波作为输入动力时程,利用数值方法研究了均匀弹性场地中圆形隧道对地表水平向峰值加速度的影响,分析了不同隧道埋深和入射波频率时地表水平向加速度的变化规律。结果表明,随着隧道埋深的增大,其对地表加速度峰值的影响变小,但影响范围近似线性增大,主要集中在5倍的隧道半径范围内;无量纲周期λ/D在6~8左右时,隧道对地表PGA的放大作用最为显著;λ/D>10时,隧道对地表地震动的影响基本可以忽略。

Site conditions have significant effect on seismic wave propagation,and the presence of a shallow-buried tunnel will change the site conditions of subsurface and has certain impact on ground motion,affecting seismic response of adjacent ground structure.By taking the Ricker wavelet as input motion,it studied the impact of a circular tunnel in the uniform elastic site on horizontal peak acceleration of subsurface by numerical method,analyzed the variation law of horizontal subsurface acceleration under different tunnel buried depths and frequencies of incident wave.The results show that the effect on peak subsurface acceleration decreases with an increase of tunnel overburden,the scope of influence increases linearly and it is mainly within the range of five times of tunnel radius;the amplification effect of tunnel on subsurface PGA is most significant when the dimensionless period λ/D is around 6-8 while the effect of tunnel on subsurface motion can be ignored when λ/D is more than 10.