易液化深厚覆盖层地震动放大效应台阵观测与分析

发布时间：2018-06-02 13:41

本文选题：深厚覆盖层 + 地震动　；参考：《岩土工程学报》2017年07期

【摘要】：基于美国加州Caltrans/CDMG的两个井下台阵加速度记录,从时域和频域分析了百米级易液化深厚覆盖层在不同地震下的地震动放大效应,揭示了地震动从基岩向覆盖层传播的4个重要特征:(1)加速度放大效应受土层深度影响,近地表20~30 m以内放大效应突出;(2)地震动三分量的放大效应具有方向性,水平向与竖向地震动放大效应差异显著;(3)基岩加速度呈现"小震放大、大震衰减"的规律;(4)加速度放大规律与频率相关,深厚覆盖层放大频带较宽。初步分析了造成上述放大效应的可能原因。在此基础上,基于平面波动假设提出了考虑层间波阻抗比放大和传播路径衰减的深厚覆盖层加速度放大效应简化函数,改进了1/4波长法的参数取值,并结合自由表面效应,对前述台阵记录的放大效应进行了估算,发现无论时域还是频域,预测结果与实际观测都较接近。本文研究成果可为深厚覆盖层液化判别和抗震设计的加速度选取提供理论依据和简化分析方法。
[Abstract]:Based on the acceleration records of two downhole arrays in Caltrans/CDMG, California, the ground motion amplification effect of 100 meters easy liquefaction deep overburden under different earthquakes is analyzed in time domain and frequency domain. It is revealed that four important characteristics of ground motion propagating from bedrock to overburden layer: 1) acceleration amplification effect is affected by the depth of soil layer, and the amplification effect of three components of ground motion is directional within 20 ~ 30 m near the ground surface. There is a significant difference between horizontal and vertical ground motion amplification effects. (3) the acceleration of the bedrock is characterized by "small earthquake amplification, large earthquake attenuation" (4) the acceleration amplification law is related to the frequency, and the deep overburden has a wide amplification frequency band. The possible causes of these amplification effects are analyzed preliminarily. On this basis, based on the plane wave hypothesis, a simplified function of the acceleration amplification effect of the deep overlay considering the interlaminar impedance ratio amplification and propagation path attenuation is proposed. The parameters of the 1 / 4 wavelength method are improved and the free surface effect is combined. The amplification effects of the aforementioned array records are estimated and it is found that the predicted results are close to the actual observations in both time and frequency domain. The research results in this paper can provide theoretical basis and simplified analysis method for liquefaction discrimination of deep overburden and selection of acceleration in seismic design.
【作者单位】：浙江大学软弱土与环境土工教育部重点实验室;浙江大学岩土工程研究所;成都理工大学地质灾害防治与地质环境保护国家重点实验室;中建三局投资发展有限公司;
【基金】：国家自然科学基金项目(51578501) 浙江省自然科学基金项目(LR15E080001) “国家特支计划”青年拔尖人才项目(2013) 国家重点基础研究发展计划(“973”计划)项目(2014CB047005) 地质灾害防治与地质环境保护国家重点实验室开放基金项目(SKLGP2015K017)
【分类号】：P315.9;TU435

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