基于真实地形的山谷场地三维地震响应特征研究

Study on 3D seismic response characteristics of valley site based on real terrain

摘要:

为探讨典型山谷场地的地震响应特征，以北天山地区典型山谷场地为背景，基于真实地貌建立了三维动力有限元数值分析模型，分析了脉冲及非脉冲型地震作用下的场地位移、加速度和谱加速度响应特征。研究表明:场地地震动力响应受地形特征影响显著，地表位移和加速度响应均随地势升高而整体放大，狭窄山谷区的位移响应强于宽阔山谷区但加速度响应弱于宽阔山谷区；局部突起的山嘴地形会造成局部位移响应放大，非脉冲型地震作用下局部加速度响应放大现象显著，而脉冲型地震作用下局部加速度响应放大现象不明显；随着地层深度减小，地层位移和加速度响应均放大，浅层岩体的位移响应放大效应减弱但加速度响应放大效应增强；两种类型地震作用下地表位移响应差异显著而加速度响应差异相对较小，随着输入地震动PGA增加位移和加速度响应均近线性增大；山峰等高地势区域的短周期谱加速度明显高于山谷等低地势区域，山谷低地势区域的长周期谱加速度则高于山峰区域，狭窄山谷区的长周期谱加速度明显高于宽阔山谷区，在山谷场地开展工程建设时应根据建筑结构自身特点进行合理规划和布置。

Abstract:

In order to explore the seismic response characteristics of typical valley sites, a three-dimensional finite element numerical model was established based on the real geomorphology of a typical valley site in the North Tien Shan region as a background, and the response characteristics of the site displacements, accelerations, and spectral accelerations were analyzed under impulsive and non-pulsive seismic effects. The study shows that: the dynamic response of the site is significantly affected by the topographic features, the surface displacement and acceleration are amplified with the rise of the ground level, and the displacement response of the narrow valley area is stronger than that of the wide valley area, but the acceleration response is weaker than that of the wide valley area; the topography of the local protruding nozzle causes the amplification of the local displacement, and the phenomenon of local acceleration amplification is remarkable under the non-pulsed seismic effect, while the phenomenon of local amplification under the pulsed seismic effect is not obvious. With the decrease of depth, the displacement and acceleration are amplified, and the amplification effect of shallow rock body on displacement is weakened, but the amplification effect on acceleration is strengthened; the difference of surface displacement and acceleration under the two types of earthquakes is significant, but the difference of acceleration is relatively small, and the displacement and acceleration increase nearly linearly with the increase of PGA; the short-period spectral acceleration in the high relief area of mountain peaks and other high terrain areas is significantly higher than that in the low relief area of valleys, while the long-period spectral acceleration in the low relief area of valleys is significantly higher than that in the low relief area of valleys. The short-period spectral acceleration of high relief areas such as mountain peaks is obviously higher than that of low relief areas in valleys, while the long-period spectral acceleration of low relief areas in valleys is higher than that of mountain peaks, and the long-period spectral acceleration of narrow valleys is obviously higher than that of broad valleys.