地脉动作用下的岩土动力响应研究

Study on Dynamical Response of Ground Soil to Micro-Tremor

以福建沿海地区 (以福州市区为主 )场地土的动力特性和地脉动频谱结构为研究对象 ,对该地区进行了场地地脉动的测试 ,利用快速傅立叶变换 (FFT)方法对观测到的地脉动信号进行频谱分析。根据实际观测资料研究了地脉动频谱结构特征及场地土对地脉动的频率响应特性。结果表明 ,地脉动的频谱特性与场地覆盖层厚度和地基土刚度的变化密切相关 ;场地土剪切波在覆盖层范围内的传播时间和覆盖层厚度是影响地脉动卓越周期的重要原因 ,其中软土层对地脉动的卓越周期有一定的放大作用 ;可以通过研究场地地脉动的特性来深入了解研究区岩土的动力特性 ;建立场地土覆盖层厚度、场地土剪切波在覆盖层范围内的传播时间与地脉动卓越周期之间的相关关系 。

The ground micro-tremor signals are observed in coastal area of Fujian, mainly in Fuzhou, and the signals are analyzed by fast Fourier transform method (FFT). We not only study the characteristics of the structure of frequency-spectrum and response to ground micro-tremor, but also investigate the function with frequency-dependence and frequency-selection of micro-tremor for different foundation soil strata. The results are as follows: First, it can reflect variation of thickness of covering layer and the duration of propagation time of the shear wave in overburden layer. Second, the duration of propagation time of the shear wave in overburden layer and the thickness of site overburden layer are two of the important reasons that affect the predominant period of the ground micro-tremor. Furthermore, soft soil of the ground enlarges predominant period of the ground micro-tremor in certain degree. Third, through studying the characteristics of the structure of frequency-spectrum, we can estimate the dynamical characteristics of ground soil. Fourth, with the establishment of correlations between the predominant period of the ground micro-tremor and the thickness of overburden layer, and the length of propagation time of shear wave in the overburden layer, it helps reveal and understand the correlation between ground formation and the micro-tremor predominant period, and will also help develop the application of the ground micro-tremor analysis technique.