地震作用下岩体结构及岩性对高陡岩质边坡动力响应特征的影响

Influence of the rock mass structure and lithology on the dynamic response characteristics of steep rock slopes during earthquakes

为研究岩体结构及岩性对高陡岩质边坡地震响应特征的影响,该文建立了均质软/硬岩边坡、层状软/硬岩边坡4个数值模型,采用有限元方法进行动力分析。通过分析边坡的动力加速度放大系数(MPGA),研究岩体结构及岩性对坡内波传播特征及其动力放大效应的影响。研究结果表明:岩体结构及岩性对坡内的波传播特征具有影响,软弱夹层使波在地震坡内出现了局部放大效应;相同条件下软岩边坡的动力放大效应大于硬岩边坡,与岩体结构相比岩性对边坡动力响应影响更显著,与均质边坡相比岩性对层状边坡的地震放大效应影响更大,均质软岩与均质硬岩边坡的MPGA比值小于层状软岩与层状硬岩边坡的MPGA比值;软硬岩边坡均表现出一定的高程及趋表放大效应,与均质边坡相比层状边坡的高程放大效应具有明显的非线性变化特征;软弱夹层对边坡的动力放大效应具有影响,层状边坡的动力放大效应大于均质边坡。

Numerical models were used to study the influence of the rock mass structure and lithology on the seismic response characteristics of steep rock slopes for homogeneous soft/hard rock slopes and layered soft/hard rock slopes. The dynamic analyses used the finite element method. The predictions gave the dynamic acceleration amplification coefficient(MPGA) of the slopes that characterized the influence of the rock structure and lithology on the wave propagation characteristics and the amplification effect. The results show that the rock structure and the lithology influence the wave propagation characteristics in the slopes with weak interlayer interactions leading to local amplification of the seismic waves in the slopes. The dynamic amplification effect is greater for soft rock slopes than for hard rock slopes. The lithology has more effect on the dynamic response of the slopes than the rock structure. The lithology also more greatly influences the seismic amplification of layered slopes than homogeneous slopes. The MPGA ratios of homogeneous soft rock and homogeneous hard rock slopes are smaller than those of layered soft rock and layered hard rock slopes. The soft and hard rock slopes also show elevation and trend magnification effects. The elevation amplification effect of the layered slopes does not vary linearly as with homogeneous slopes. The weak interlayer interactions impact the slope amplification effect while the dynamic magnification effect of layered slopes with weak interlayer interactions is larger than for homogeneous slopes.