Theoretical And Experimental Analysis Of The Vibration Transmission Properties Of Conventional Metro Track Structure

Metro lines often operated at populous district, the vibration and noise caused by its operation cannot be ignored, which become an important issue in some design and construction departments. Vibration and noise control at the source is the most efficient way, one of which is applying variable vibration damping track structures. However, the vibration isolation effect is not as good as nominal value, in the meantime, it is found that there will be some problems like corrugation in some metro lines with vibration damping track. Therefore, it is necessary to find out the vibration transmission properties of some popular track structure. In this thesis, based on review large amount of vibration control theory and test research, finite element models of normal track, GJ-Ⅲ fastener track, rubber damping pad floating slab track and steel spring floating slab track were built for theory analysis, also some hammer tests and train running tests were conducted on metro line field, then, the vibration transmission properties and vibration isolation effects were compared between these different tracks. Main research details and conclusions are as follows:(1)For the same track structure, totally, the vertical vibration had an attenuation through the order rail-ballast bed-tunnel wall, there was a peak value at160Hz for the rail located at GJ-Ⅲ damping fasteners, and it was245Hz for rail located at single toe elastic fastener, which was related with fastening structures and parameters. The vibration difference of ballast bed and tunnel wall in the rubber damping pad floating slab track and steel spring floating slab track was larger than that in normal track, which indicated the vibration damping pad and steel spring had an effect of vibration isolation. However, the vibration of ballast bed in rubber damping pad floating slab track and steel spring floating slab track was larger than that in normal track or GJ-Ⅲ fastener track.(2)With the train running, the field measurement results showed that, the maximum acceleration value is less than30g at vertical and lateral direction. Compared with other tracks, the rail vibration in GJ-Ⅲ damping fasteners track was larger, at the frequency range of0-200Hz, the rail vibration in GJ-Ⅲ damping fasteners track was larger than that in normal track.(3)From theory analyses, hammer tests and train running tests, it was found that arranged in descending order of vibration isolation effects, these were steel spring floating slab track, rubber damping pad floating slab track, GJ-III fastener track. In turn, which can be observed from the vibration damping quantity of these three tracks, it was12.6dB、4.2dB and0.8dB respectively. From the measured data analyses, it was presented the results were not consistent by using vibration damping quantity and Z-weighting evaluate, thus, when evaluating the effects of different tracks, it was important to demonstrate the evaluation index and frequency range.Theory and test analyses were carried out in this thesis for vibration transmission properties, the analyses methods and some conclusions were of valuable reference for choosing track types reasonably and preventing the harm caused by vibration.