浅埋圆形隧道对地表加速度影响参数分析’

Parametric analysis of ground motion amplification due the presence of a shallow circular tunnel

隧道的存在会改变地震波的传播路径,继而影响地表地震动。利用有限差分软件FLAC2D对含隧道场地地震动效应进行了研究。以弹性土体中的浅埋圆形隧道为研究对象,选取Ricker小波作为输入时程,分析了不同隧道衬砌厚度、土层剪切波速、衬砌-土层剪切波速比和入射波频率等参数对地表水平向峰值加速度的影响。结果表明,隧道对地表加速度的影响随着λ/D先增加后减小,约在6≤λ/D≤8时放大作用最显著;增大土层剪切波速、减小衬砌厚度和衬砌-土层剪切波速比均会提高衬砌隧道对地表加速度的放大作用;对于无衬砌隧道,当入射波的波长相同时,土层剪切波速的变化不会改变地表峰值加速度的放大倍数。

The presence of the underground structure can affect the propagation of the wave motion thus will has a influence on the surface ground motions. The influence of the circular tunnel on the ground surface horizontal acceleration was investigated using the finite difference code FLAC2 D. The Ricker wavelet with a wide range of frequency was selected as the input motions. The effects of the tunnel lining thickness,shear wave velocity of soil,shear wave velocity ratio of lining and soil were also taken into account. The results show that the medium and short period ground motions was significantly effected than the long period. This was more evident when 6 ≤ λ/D ≤8. Reducing the lining thickness,increasing the soil shear wave velocity and the decreasing of lining-soil shear wave velocity ratio will increase such amplification effect. For the non-lining tunnel,the change of the shear wave velocity did not cause the change of the peak value of the ground surface,if the wave length of the incident wave was same.