深海地基场地地震反应分析的一维化时域算法

发布时间：2018-03-16 09:38

本文选题：流体饱和多孔介质　切入点：理想流体　出处：《北京交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：目前我国大型跨海工程发展迅速,但其抗震研究尚不充分,其中重要的原因是对于海底这一特殊场地的地震动认识不足。本文根据深海地基场地特点,基于流体饱和多孔介质和理想流体介质的波动理论,提出了一种应用于基岩-成层饱和土层-水地基场地系统地震反应分析的一维化时域有限元算法,并结合精确人工边界条件,编制计算机程序求解分析了水深变化对深海地基场地震动的影响。本文的主要工作如下:1.提出了一种深海地基场地地震反应分析的一维化时域有限元算法。该方法以饱和多孔介质和理想流体介质的波动理论为基础,根据Snell定理,推导得到应用于饱和土层和流体层内的一维化动力有限元表达式,结合层间边界条件和已有的精确动力人工边界条件,建立基岩-成层饱和土层-水地基场地系统的整体分析方程,通过中心差分法和Newmark法相结合的时步积分法进行方程求解,并编制相应的Fortran程序。该算法既可用于深海地基场地震动研究,又可为跨海工程地震反应分析提供地震动输入。2.结合经典的波动理论,推导了平面波入射下基岩-成层饱和土层-水地基场地地震反应分析的频域解析解,通过傅里叶逆变换得到时域解。将上述建立的一维化时域有限元解与解析解进行对比,证明了该时域有限元方法的有效性。3.应用本文提出的深海地基场地地震反应分析的一维化时域有限元算法,分析了 P波60°入射时某一深海地基场地随水深变化对深海地基场地地震动的影响。得到的主要结论如下:a)竖向位移峰值随水深的增大先增加后减小,水平向位移峰值随水深的增大先减小后增加。当水深达到一定值时,位移峰值不再受水深的影响。水深一定时,位移峰值沿土层深度整体上是逐渐减小的。b)竖向加速度峰值随水深的变化规律为,随水深增大竖向加速度峰值先增加再减小再增加。土层表面点水平方向加速度峰值随水深的增大先减小再增加。c)土骨架水平向正应力峰值、竖向正应力峰值以及孔隙水压力峰值随水深的变化先增大再逐渐减小。
[Abstract]:At present, the large-scale cross-sea engineering in China is developing rapidly, but its seismic research is not enough, among which the important reason is the lack of understanding of the ground motion of this special site. According to the characteristics of the deep-sea foundation site, Based on the wave theory of fluid-saturated porous media and ideal fluid medium, a one-dimensional time-domain finite element method for seismic response analysis of bedrock, saturated soil layer and water foundation is presented. Combined with precise artificial boundary conditions, The influence of water depth variation on the ground vibration of deep sea ground is analyzed by computer program. The main work of this paper is as follows: 1. A one-dimensional time-domain finite element method for seismic response analysis of deep-sea ground site is presented. The method is based on the wave theory of saturated porous media and ideal fluid medium, According to the Snell theorem, the one-dimensional dynamic finite element expression applied to saturated soil and fluid layer is derived, which combines the interlayer boundary conditions and the existing exact dynamic artificial boundary conditions. The integral analysis equation of bedrock, saturated soil layer and water foundation site system is established and solved by the time step integration method which combines the central difference method and the Newmark method. The corresponding Fortran program is compiled. The algorithm can be used not only to study the ground motion in deep sea foundation, but also to provide seismic response analysis of cross-sea engineering with earthquake motion input .2. combined with classical wave theory, The frequency domain analytical solution for seismic response analysis of bedrock, layered saturated soil layer and water foundation under plane wave incidence is derived. The time-domain solution is obtained by inverse Fourier transform. The one-dimensional time-domain finite element solution is compared with the analytical solution. The validity of the time-domain finite element method is proved. 3. The one-dimensional time-domain finite element method for seismic response analysis of deep-sea ground is proposed in this paper. The influence of the variation of a deep-sea ground site with water depth on the ground motion of deep-sea ground is analyzed when P-wave is incident at 60 掳. The main conclusions are as follows: (1) the peak value of vertical displacement increases at first and then decreases with the increase of water depth. The peak value of horizontal displacement decreases first and then increases with the increase of water depth. When the depth of water reaches a certain value, the peak value of displacement is no longer affected by the depth of water. The peak value of displacement decreases gradually along the depth of soil layer as a whole. B) the variation of the peak value of vertical acceleration with water depth is as follows:. With the increase of water depth, the peak value of vertical acceleration first increases and then decreases, and then increases. The peak value of horizontal acceleration of soil surface decreases first and then increases with the increase of water depth. The peak value of vertical normal stress and pore water pressure increase firstly and then decrease gradually with the change of water depth.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P75;TU435

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