Study On Typical Vibration Reduction Measures And Vibration Reduction Effect Of Nanjing Metro

The rapid development of Nanjing metro has brought great convenience to citizens’ travel.However,since most subways are built in densely populated urban centers,the track direction and buried depth design are difficult to avoid some sensitive points.With the enhancement of people’s awareness of environmental protection,vibration problems that were ignored in the past are causing more and more strong reactions,and vibration complaints are increasing day by day.In order to improve the vibration of the subway network,Nanjing Metro Line 4 is actively explored.This paper takes Nanjing Metro Line 4 as an example,puts forward three typical vibration reduction measures,namely the application of vibration reduction equipment,the limitation of speed and the improvement of track unsmoothness,and carries out a study on the typical vibration reduction measures and their effects,so as to provide reference and basis for the development of the vibration reduction work of Nanjing subway network.The main work content is as follows:(1)Research on the principle of vibration reduction and key points of implementation of three typical vibration reduction measures: Vibration damping fastener and floating plate ballast are the most widely used vibration damping equipment.Shear fastener and compression fastener respectively use the shear deformation and compression deformation of rubber plate to play the vibration damping effect,while floating plate ballast can isolate and attenuate vibration through the inertial motion of the ballast bed on the elastic body.The construction preparation,construction sequence,inspection and acceptance of the installation of damping fastener and floating plate ballast are emphasized.The vibration reduction principle of decelerating speed is analyzed from three aspects: reducing the vertical dynamic stiffness of fastener system,reducing the acceleration in the process of changing speed and reducing the external excitation,and the implementation process of the "speed limiting multi-vehicle" operation mode is introduced.Track geometry roughness and rail wave wear are two kinds of track roughness that have been paid more attention.The geometric roughness is checked by the way of combining static and dynamic,and improved by "lifting",while rail wave wear is improved by using the wave wear detector and its analysis system for data acquisition and analysis,and by milling operation.(2)The INV3060 A intelligent data acquisition system and DASP-V11 analysis system are used to conduct field measurement and data analysis on the damping fasteners and floating plate ballast section.First of all,three key indicators that affect the test results,such as train selection,analysis frequency and vibration reduction evaluation quantity,are clarified.On this basis,the actual vibration reduction quantity and vibration reduction characteristics in different frequency bands of the damping fastener and the floating plate ballast bed are obtained: Shear fastener belongs to primary vibration reduction products,nested fastener and compression fastener belong to intermediate vibration reduction products,solid damping steel spring floating plate ballast bed and vibration cushion floating plate ballast bed belong to advanced vibration reduction products,liquid damping floating plate ballast bed belongs to special vibration reduction products.In the 4-200 Hz frequency band,the overall vibration damping performance of the floating plate ballast is better than that of the damping fastener.The floating plate ballast can be used to reduce vibration in the whole frequency band,while the damping fastener can amplify vibration in part of the frequency band.(3)By studying the vibration of the damping fastener and the section of the floating plate ballast in the frequency band of 1-2000 Hz at the rail,ballast and tunnel wall,the influence of the damping fastener and the floating plate ballast on the vibration of track equipment and the attenuation process of vibration energy are obtained: Damping fastener has little influence on rail vibration,but can significantly reduce the vibration at the track bed,and then reduce the tunnel wall vibration.The vibration energy is mainly attenuated in the process of transferring from the rail to the track bed.The influence of floating plate ballast on rail vibration is also small,but the vibration at the ballast is significantly intensified,and the vibration at the tunnel wall is significantly reduced.The vibration energy is mainly attenuated in the process of transfer from the ballast to the tunnel wall.(4)Based on multi-body dynamics software SIMPACK and finite element software ABAQUS,a rigid-flexible coupling model of vehicle-track-tunnel-soil was established.The process of creating vehicle-track model and track-tunnel-soil coupling model are introduced respectively.The operation methods of key steps such as creating six trains and applying track excitation in SIMPACK,setting infinite boundary,ground stress balance and applying load in ABAQUS are described.The couplers’ support force output from the rail-rail coupling model was used as the input excitation of the track-tunnel-soil model.The structure and material parameters of the vehicle,track,tunnel and soil of Line 4 were set to simulate the actual running state.The correctness of the model was verified by comparing the simulated values with the measured values.(5)The vehicle-track-tunnel-soil model is used to study the influence of train speed and track irregularity on the vibration response of track and tunnel wall: In addition,the change of speed will cause the local peak frequency of the reaction of the fastener to offset.By reducing the speed of the fastener,the damping quantity of the primary vibration reduction product can be achieved.It is suitable for the section with high operating speed and concentrated vibration frequency at 4-80 Hz.Rail wave grinding can significantly increase the reaction amplitude and change amplitude and rate of fastener reaction.For the area with severe wave grinding,grinding and milling can play a significant damping effect.At the same time,the influence of rail wave grinding on vibration in different frequency bands is related to its own rail roughness level.To control it in a low level,especially 100-300 mm wave grinding needs to pay close attention to the development speed,timely treatment.