摘要
根据2.5维有限元原理,从横观各向同性土体弹性本构方程出发,推导出横观各向同性土体2.5维有限元弹性波动方程。轨道简化成铺设在横观各向同性地基上的Euler梁。在轨道方向的垂直截面上,将轨道结构和地基进行有限元离散,采用八节点单元,每个节点包含3个自由度,从而使复杂的三维问题转化为平面应变问题,再通过FFT逆变换转换为沿轨道方向三维空间中的时域振动响应。分别基于上海和北京地区的典型土质参数,进行场地动力响应分析。结果表明:列车运行引起的北京地区场地的加速度响应幅值及位移响应幅值均分别大于上海地区场地的加速度响应幅值及位移响应幅值;随着距轨道中心处距离的增加,两地区土体的动力响应频率均衰减到简谐荷载的自振频率周围,反映出横观各向同性土体的滤波作用;应力波在软土层中传播所消耗的能量大于在硬土层中传播;列车运行引起的地面振动衰减曲线会出现反弹增大的现象,其反弹特性及出现的位置与地基土体参数及列车运行速度密切相关。
2.5D finite element equation for elastic waves of transversely isotropic soil is derived from means of 2.5D finite element method（FEM） from elastic constitutive equation of the transversely isotropic soil.The track is simplified as an Euler beam resting on the transversely isotropic ground.Through finite element discretization,the track structure and the foundation in a section perpendicular to track direction are modeled with 8-node elements,in which each node consists of three degrees of freedom.A 3D problem is reduced to a plane strain problem;and the results can be obtained by inverse fast Fourier transformation（FFT）.Dynamic responses of the ground are analyzed based on typical parameters of soil in Shanghai and Beijing areas.The results indicate that the amplitude of acceleration and displacement response amplitude caused by train traveling in Beijing area were higher than that in Shanghai area,respectively.With the distance increase to the track center,dynamic response frequencies of the ground in both areas are declined to the free vibration frequency of simple harmonic vibration;so the filtering of transversely isotropic soil is obvious.Transmission of dynamic wave in soft soil layer costs more energy than hard soil.The rebound phenomenon in the attenuation curve of the ground vibration has the tendency to increase,which is closely relevant to the parameters of the soil and the train speed.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2013年第1期78-87,共10页
Chinese Journal of Rock Mechanics and Engineering
关键词
土力学
横观各向同性地基
2
5维有限元法
地面振动
高速列车
频域-波数域
soil mechanics
transversely isotropic soil
2.5D finite element method
ground vibration
high-speed train
wave number-frequency domain
