黄土高填方场地地震动参数特性分析

Characteristics of Ground Motion Parameters of Loess-high Filling Sites

削山造地后形成的黄土高填方场地对地震动参数特性影响较大。以实际工程项目为研究对象,构造不同填土高度的计算剖面,采用一维等效线性化方法计算土层地震动参数,分析基岩地震动输入参数和填土高度对场地地表放大效应的影响。研究表明:场地地震放大系数随填土层的高度增加呈递减趋势。在多遇地震动和基本地震动作用下,场地地震放大系数递减速度比罕遇地震动和极罕遇地震动作用下要大。当填土高度达到一定程度后放大效应趋于平稳;填土高度的变化,会改变地表加速度反应谱的形状。填土高度越大,地表反应谱长周期的频谱成分越显著,反应谱曲线向后移,反应谱峰值点均明显向长周期移动,并出现多个峰值点,反应谱特征周期值变大;下伏基岩的刚度越大,地表峰值加速度的放大效应越大。地表加速度反应谱特征值相比变小。当填土高度增大到一定程度时,下伏基岩的种类对地表地震动特性影响则不明显。该研究成果对高填方场地的地震安全评价和结构抗震设计提供参考。

Loess-high filling sites formed by cutting off hilltops exert a large influence on the characteristics of the ground motion parameters.Based on an actual project,calculation sections with different filling heights were constructed,and the one-dimensional equivalent linearization method was used to calculate the ground motion parameters of soil layers to analyze the influences of bedrock ground motions and height of the filling soil on the ground surface amplification effect.The seismic amplification coefficient of the site decreased with increasing filled height.In addition,the seismic amplification coefficient of the site decreased faster under the action of frequent and basic earthquakes than under the action of rare and extremely rare earthquakes.When the filled height reaches a certain level,the amplification effect stabilizes;variations in filled height change the shape of the surface acceleration response spectrum.At a certain filled height,the bedrock type shows no obvious influence on the surface ground motion characteristics.This research provides a reference for seismic safety evaluation and structural seismic design of loess-high filling sites.