Study On Vibration Response And Vibration Reduction Of Subway Train Under Moving Load

With the city rail transit network increasing intensively,environmental vibration causes more and more prominent.Owing to the high density and long duration,vibration caused by rail traffic has had a significant influence on the building structure,protected ancient buildings and cultural relics units nearby,which also bring about incalculable losses to all kinds of precision instruments,especially the vibration at frequencies from 0 Hz to 80 Hz can destroy the human body.Therefore vibration propagation and control problems of railway train under moving loads has become an important research direction.In this paper,taking the vibration section of the south section of the Shenzhen Metro Line 5 as an example,the vibration response analysis of the tunnel-formation under the load of the subway train is studied by means of the combination of theory and numerical analysis,and the measures to set setting the damping layer.The damping effect of three kinds of damping layer of foam concrete,asphalt and rubber was analyzed,and obtained the following results:(1)Based on the establishment of the subway vehicle-track vertical coupling model and the engineering parameters,the vibration load time course of the trains can be calculated and can be loaded into the numerical model as a vibration source.(2)According to the idea of load-structure method,the tunnel-soil numerical model is established with reference to the engineering example,and the vibration response of the tunnel lining structure,strata and ground is analyzed.When the vibration is propagated along the longitudinal direction of the tunnel,the vibration peak above the tunnel is gradually increased.The vibration peak below is gradually reduced.The whole process of vibration to the lateral transmission of the tunnel is in the overall attenuation,the vibration response is amplified when the track is 20 m away from the vibration source,and the vibration response is amplified when the ground is 20 m and 40 m away from the vibration source.(3)The damping effect of foam concrete,asphalt and rubber layer was studied by adding the vibration layer between the initial lining and the second lining of the tunnel.The results show that the three can effectively reduce the peak vibration response of the formation and the ground.For the maximum Z-level of the ground,after the addition of foam concrete damping layer,the vibration was reduced from 74.3 dB to 67 dB,down by 9.5%;after the addition of asphalt damping layer,the vibration was reduced by 7.9%;after the addition of Rubber damping layer,the vibration was reduced by 7.6%.after vibration are in line with environmental vibration standard limits.All the vibration are in line with environmental vibration standard limits.For the tunnel top and side wall structure,the addition of foam concrete damping layer reduces the acceleration peak,while the setting of asphalt layer or rubber layer enlarges the vibration acceleration peak,and the more soft material,the more obvious amplification effect.In conclusion,the foam concrete layer has the best damping effect,and the vibration amplified area on the ground is 20 m and 40 m away from the vibration source.Ground structures in this range should take further measures to reduce vibration.