SH波垂直入射下的斜坡地形放大因子分析  

Amplification factor analysis of slope topography under normal incidence of SH wave

作　　者：李家祥 温瑞智[1] 刘启方 任叶飞[1] 王宏伟[1] LI Jiaxiang;WEN Ruizhi;LIU Qifang;REN Yefei;WANG Hongwei(Key Laboratory of Earthquake Engineering and Engineering Vibration, Institute of Engineering Mechanics, China Earthquake Administration, Harbin 150080, China;Suzhou University of Science and Technology, Key Laboratory of Structure Engineering of Jiangsu Province, Suzhou 215011, China)

机构地区：[1]中国地震局工程力学研究所,中国地震局地震工程与工程振动重点实验室,黑龙江哈尔滨150080 [2]苏州科技大学江苏省结构工程重点实验室,江苏苏州215011

出　　处：《世界地震工程》2021年第1期176-188,共13页World Earthquake Engineering

基　　金：中国地震局工程力学研究所基本科研业务费专项资助项目(2018B03);重点研发项目省级资金资助项目(GX18C011)。

摘　　要：现有大量观测记录表明:斜坡地形对地震波的传播有着非常强烈的影响。为服务于工程抗震设计,基于显式有限元方法,定量分析SH波垂直入射下二维斜坡地形的地震动响应与斜坡角度、土层厚度以及介质阻抗比的关系,总结了位于一维土层基本频率附近斜坡上台面各区域放大因子的变化规律。研究表明:(1)斜坡面对SH波的反射使二维斜坡地形的放大倍数较一维土层存在显著放大,且该现象在缓坡中更加明显。(2)当土层厚度为斜坡高度的1/4,介质阻抗比为0.368,坡度为30°时,放大因子在距坡顶1.67倍斜坡高度处取到最大值1.930。(3)斜坡覆盖土层薄时,放大因子受斜坡角度的影响大,斜坡覆盖土层厚时,阻抗比成为影响放大因子的主要因素。(4)分别考虑土层厚度、斜坡角度、介质阻抗比以及观测点位置对二维斜坡地形地表地震动响应的影响,取1倍斜坡高度作为区域间隔,统计每个区域内各参数对应的放大因子最大值,对比现有规范给出工程抗震设计参考值及放大因子大于1的基频比范围。A large number of observational records show that the slope topography has a very strong influence on the propagation of seismic waves.In order to serve the engineering seismic design,the relationships between the amplification of ground motion and the slope angle,the thickness of soil layer and the impedance ratio between soil and bedrock under inclined SH waves for a slope topographic site are analyzed,and the variation law of the terrain amplification factor of the platform on the two-dimensional slopes with the frequency which near the basic frequency of the one-dimensional soil layer is studied based on explicit finite element method.The study shows that:(1)the reflection of SH waves on the slope makes the amplification factor of two-dimensional slope significantly larger than that of one-dimensional soil layer,and this phenomenon is more obvious when the soil layer thickness is 1/4 of the slope height and the slope angle is 20~60°;(2)When the slope angle is 30°,the soil thickness is 1/4 of the slope height and the impedance ratio is 0.368,the amplification factor reaches a maximum value of 1.930 at 1.67 times the height of the slope from the top of the slope;(3)The slope angle is the main factor affecting the amplification factor for the thin soil layer while the impedance ratio is the main factor affecting the amplification factor for the thick soil;and(4)Considering the influence of soil layer thickness,slope angle,impedance ratio and the position of observation sites on the ground motion response of two-dimensional slope topography,1 time of the slope height was taken as the amplification area interval,and the maximum amplification factors corresponding to each parameter in each area were calculated,the reference value of amplification factors in engineering seismic design and the range of base frequency ratio with amplification factor greater than 1 are given based on the existing specifications.

关 键 词：斜坡地形 二维模型 基本频率 放大因子 放大区域 

分 类 号：P315.9[天文地球—地震学]