特殊浮置板轨道隔振效果的三维数值研究

针对城市轨道交通可能引发的低频振动,采用特殊浮置板轨道进行室内激振试验.运用MIDAS/GTS程序,建立"轨道-隧道-地层"三维耦合模型,选取不同弹簧刚度和支承间距的4种组合,计算简谐荷载作用下的加速度响应,分析浮置板上、隧道底板上和地表的竖向、水平加速度级和不同位置的加速度级损失.结果表明:①在浮置板和隧道底板上,竖向加速度级量值比水平加速度级大;距隧道中线20 m处地表,水平比竖向加速度级大;②在支承间距不变的情况下,轨道的基频与弹簧刚度成正比;弹簧刚度不变时,轨道的基频与支承间距成反比;③弹簧刚度的降低和支承间距的增大,可提高隔离低频竖向振动的效果,加速度级损失可达47dB以上;④弹簧刚度越小、支承间距越大,则对于基频以上频段,隔离低频水平振动效果越好,对于基频以下频段,隔振效果越差.

3-D Numerical Study on Vibration Isolation Performance of Special Floating Slab Track in Lab

A kind of special floating slab track is utilized to conduct an experiment in laboratory in order to control potential low-frequency vibration from urban mass transit. Considering dynamic track-tunnel-soil interaction in MIDAS/GTS,a three-dimensional numerical model is established,in which harmonic loads are applied in four cases made of different stiffness and spacing of steel springs. The acceleration responses are acquired,and the vertical and horizontal vibration acceleration level on the slab,tunnel invert and at ground surface which is 20m away from the tunnel centerline are analyzed,at the same time,losses of the vibration acceleration level at different positions are analyzed. The analysis results indicate as follows: ① The vertical vibration acceleration level is greater than the horizontal level on the slab and tunnel invert,but,contrariwise,the vertical level is less than the horizontal level at ground surface 20 m away from the centre line of the tunnel; ② when the spacing of steel springs is constant,the relationship between the basic frequency of the track and stiffness of steel springs is in direct ratio; and when the stiffness is constant,the relationship between the basic frequency and spacing is in inverse ratio; ③ with the decrease of stiffness and the increase of spacing of steel springs,vertical vibration isolation performance is better,and the vertical vibration acceleration level is reduced in excess of 47dB; ④ the smaller the stiffness of steel springs and the longer the spacing of steel springs,the better the horizontal vibration isolation performance for a frequency range beyond the basic frequency of the track,but,contrariwise,the poor the horizontal vibration isolation performance for a frequency range below the basic frequency of the track.