剪切模量沿深度按指数规律增大的场地土的地震放大效应

SEISMIC AMPLIFICATION OF SITES WITH EXPONENTIALLY INCREASING SHEAR MODULUS WITH DEPTH

采用一维波动模型分析基岩上、受竖直向上传播的稳态剪切地震波激振下剪切模量沿深度按指数规律增长的场地土的横向自由振动问题,求得位移的闭合解,并由该解得到反映地震放大效应的场地的放大系数。通过对此类场地土的算例分析,讨论了剪切模量沿深度按指数规律增长的场地土的地震放大效应,并从讨论中总结了场地土土质特性、基岩与场地土底面之间的阻抗比及振动频率对地震放大效应的影响规律,同时验证了广泛使用的场地卓越周期简化估算公式仍可应用于剪切模量沿深度非线性变化的场地土。

For the one-dimensional analysis of sites on a bedrock subjected to the excitation of steady-state and vertically propagating shear seismic waves, closed-form solutions for the displacements are presented for a single layer with exponentially increasing shear modulus with depth. A general form of analytical solution of the seismic amplification is developed. The study of an example shows frequency and the impedance ratio of the half-space and the amplification. The predominant period of a nonlinear site, i.e. the layer, is proved to be a good estimate. that the characteristics of soil sites, the vibration bottom surface of the soil layer affect the seismic four times the total shear wave travel time through