SV波斜入射下坡体地形放大效应的研究

Research of slope topographic amplification subjected to obliquely incident SV-waves

基于黏弹性人工边界建立等效地震荷载,通过自编程序实现斜入射地震波在有限元软件中快速准确的添加,并以此对斜入射地震波作用下双面坡的地震响应进行分析,探讨不同入射角和模型尺寸对坡体地形放大效应的影响规律。根据建立的数值模型,首先得出不同卓越频率f0与归一化高度H/λ的关系;然后依据水平峰值加速度放大系数Ah和竖直峰值加速度放大系数Av分析归一化高度H/λ、坡度i和平台宽度L三个参数对坡体地形放大效应的影响;最后根据两侧坡脚、两侧坡顶和坡顶中点的Ah,分析斜入射角度θ对H/λ,i和L的影响。结果表明:通过将数值模型中地震波入射问题程序化和界面化,方便了等效地震荷载在有限元软件中的快速添加;卓越频率f0对坡体地形放大效应的影响只与H/λ有关,而与其他因素无关;H/λ的变化影响右侧坡顶,i的变化影响两侧坡顶,L的变化影响两侧坡顶和坡顶中点;两侧坡顶Ah的最大值Ahmax不一定在地震波垂直入射(θ=0°)时得到,其取值与i和L有关。综上,在有限元中建立了地震波斜入射的完整流程,保证了计算精度并简化了建模难度;地震波入射角度对坡体地形放大效应的影响是显著的。

Incidence angle of seismic waves is an important factor affecting the amplification of topography.However,the oblique incidence of seismic waves is more complicated in numerical models.Therefore,the effect of different incident angles of seismic waves on topographic amplification has not been well solved in the numerical model.In this paper,equivalent seismic load is established based on the viscous-spring artificial boundary.Oblique incidence seismic wave in finite element software is added rapidly and accurately by a self-developed program.Then,the seismic response of double-faced slope under oblique incidence seismic wave is analyzed,and the influence of different incidence angles and model sizes on the amplification effect of slope topography is discussed.According to the numerical model,the relationship between predominant frequency f0 and normalized height H/λis obtained.Then,the influence of normalized height H/λ,slope angle i and platform width Lon the slope topography amplification is analyzed according to the horizontal peak acceleration amplification Ahand the vertical peak acceleration amplification Av.Finally,according to the Ahof slope foot,slope crest and the midpoint of slope surface,the influence of oblique incident angle is analyzed by H/λ,i and L.The results show that:by programming and interfacing the incident wave in numerical models,it is convenient to add the equivalent seismic load quickly in the finite element software.The influence of predominant frequency f0 on the topographic amplification is only related to H/λ.The change of H/λonly influences the amplification of right crest,the change of i influences the amplification of both slope crests and the change of Linfluences the amplification of both slope crests and the midpoint of slope surface.The maximum of horizontal peak acceleration amplification Ahmax on slope crests may not obtain on vertical incidence(θ=0°),the results of Ahmaxare related to different i and L.In summary,a complete process of oblique incidence of seismic waves is established in the finite element method,based on this,the accuracy of calculation is ensured and the difficulty of modeling is simplified.The influence of seismic wave incidence angle on the amplification effect of slope topography is significant and necessary.