层状半空间中洞室对平面SH波的放大作用

Amplification of plane SH waves by a cavity in layered half-space

利用间接边界元法,求解了弹性层状半空间中洞室对入射平面SH波的放大作用问题,并以基岩上单一土层中洞室对入射平面SH波的放大作用为例进行了数值计算分析。本文模型的特点之一是考虑了层状场地的动力特性,因而更接近于实际工程;特点之二是计算精度非常高。研究表明,层状半空间中洞室对波的放大作用与均匀半空间中情况有着本质的差别;层状半空间中洞室附近地表动力响应由土层动力特性和洞室对波的散射二者共同决定。土层动力特性不仅影响洞室附近地表位移的幅值,还会影响地表位移的频谱。在土层的前几阶共振频率附近,随着基岩与土层剪切波速比的增大,土层的影响随之增大,而随着土层厚度的增加,土层的影响随之减小,并逐渐趋于均匀半空间情况。

This paper presents the amplification of plane SH waves by a cavity in layered half-space by using indirect boundary element method（IBEM）.Numerical results are obtained by taking a cavity in single layer over half-space as an example.One advantage of the model is that it includes dynamic characteristics of the layered half-space,and the second is its very high precision.Studies show that due to the dynamic characteristics of soil layer,there are distinct differences between the amplification of plane SH waves by a cavity in single layer over half-space and that in homogeneous half-space.The surface dynamic response near the cavity depends both on dynamic characteristics of the soil layer and wave diffraction around the cavity.Dynamic characteristics of the soil layer affect not only the surface displacement amplitudes near the cavity,but also their frequency spectra.Around resonant frequencies,the effect of the soil layer becomes larger as the shear velocity ratio of the bedrock to the soil layer increases,and the effect of the soil layer becomes smaller as the thickness of the soil layer increases,and the model will tend to the case of homogeneous half-space.