基于2.5维有限元法和虚拟激励法的地铁交通场地随机振动分析

基于2.5维有限元法和虚拟激励法进行地铁交通场地随机振动特征分析。基于虚拟激励法由轨道不平顺功率谱得到动态轮轨力功率谱,将其作为轨道—隧道—地基土系统2.5维有限元模型的外部激励,计算得到地面随机振动响应,分析车速和轨道不平顺等级对地面随机振动特征的影响。结果表明:地面振动位移受车辆轴重控制,受轨道不平顺随机激励影响较小;地面振动速度和加速度主频随地铁车速的增加显著增大,轨道不平顺等级不改变地面振动响应的频谱分布;轨道不平顺等级降低和地铁车速增大造成地面随机振动响应的离散度和Z振级最大值显著增加;轨道不平顺随机激励下,地面振动速度和加速度上限值以及Z振级最大值在垂直于地铁运行方向的衰减出现明显波动,距轨道中心线60 m外衰减趋势变缓。

Analysis of Ground Random Vibration Induced by Subway Transit Based on 2.5-Dimensional Finite Element and Pseudo Excitation Methods

Based on the 2.5-dimensional finite element method(2.5D FEM)and pseudo excitation method(PEM),the characteristics of ground random vibration caused by subway transit were analyzed.Based on the pseudo excitation method,the dynamic wheel-rail force power spectrum was obtained from the track irregularity power spectrum,which was used as the external excitation of the 2.5-dimensional finite element model of tracktunnel-soil system to obtain the ground random vibration responses.The influence of subway train speed and the level of track irregularity on the characteristics of the ground random vibration was studied.Results show that the ground vibration displacement is controlled by vehicle axle load and is less affected by the random excitation of track irregularity.The dominant frequencies of ground vibration velocity and acceleration increase significantly with the increase of subway train speed,and the level of track irregularity does not change the spectrum distribution of the ground vibration response.The decrease of track irregularity level and the increase of subway train speed cause the significant increase in the dispersion of random vibration response and the maximum value of Z-vibration level.Under the random excitation of track irregularity,the attenuation of the upper limit value of ground vibration velocity and acceleration fluctuate obviously in the direction perpendicular to the running direction of subway train,so does the maximum value of Z-vibration level,and the attenuation trend becomes slower 60 m away from the track center line.