【作者】 秦波；

【导师】 夏禾；

【作者基本信息】 北京交通大学 ， 桥梁与隧道工程， 2011， 硕士

【摘要】 本文从环境振动的影响出发,基于Rayleigh波理论研究了层状地基土模型的频散曲线、截止频率等特性,利用遗传算法对地基土剪切波速进行了反演,进而得到地基土的其它动参数。在均匀弹性水平层状介质的波传播分析中,常常采用传递矩阵的方法,本文分别介绍了直角坐标系下的传递矩阵法、柱面坐标系下的传递矩阵法、快速矢量和快速标量算法,以及有限元集成的薄层刚度法；主要针对快速标量法和薄层刚度法,利用Matlab编程计算了地基土模型的频散曲线和截止频率等基本特性,对比了两种方法的优缺点及适用范围。比较发现,薄层刚度法在低频范围计算效果比较好,但快速标量法计算速度较快,二者在高频范围的计算结果差异不大。本文进而采用薄层刚度法,编程计算并分析了环境振动中常见的几种地基土模型(递增型、软夹层)Rayleigh波的频散曲线、截止频率及相速度和波长关系等。在参数反演方面,本文介绍了阻尼最小二乘法和遗传算法,利用假设的有效相速度-频率频散曲线,通过遗传算法计算了两种典型地基土模型(递增型、软夹层)的剪切波速,利用弹性介质转换关系得到地基土的其它动参数。更多还原

【Abstract】 Considering the influence of environment vibration, and based on the Rayleigh Wave Theory, the frequency dispersion curves, cut-off frequency and some other characteristics of layered soil models are calculated, the shear wave velocities of foundation soil are inverted through genetic algorithm and some other parameters of foundation soil are obtained.The transfer matrix method is often used in the analysis of wave propagation in homogeneously elastic medium with horizontal multilayer. Some analytical methods are introduced, such as transfer matrix method in rectangular coordinate system and fast vector and fast scalar algorithm in cylindrical coordinate, thin-layer method with stiffer matrix and so on.The Rayleigh dispersion curves of multilayered soil are calculated by means of thin-layer method and fast scalar method, respectively, in which two-layered and three-layered soil model are adopted. In addition, the disperse properties of multilayered soil are analyzed, and it is found that the thin layer method is superior to rapid scalar method in low frequency domain, while in the high frequency domain it has little difference between each other. The Rayleigh wave’s properties of four multilayer soil models are compared by means of thin-layer method particularly.In the dynamic parameters inversion of foundation soil, by means of the genetic algorithm, the shear wave velocities for two common soil models are calculated based on the effective phase velocity-frequency dispersion curve, and then other parameters of multilayer foundation soil are acquired by the transformation relationship between the media’s parameters.更多还原