Research On Noise Induced By Subway On Viaduct Rail Of Chengdu Metro Line 2

With the expansion of urban scale,urban rail transit is developing rapidly and becomes one of the most important public transport for people’s daily travel in recent years because of its high speed,large transport capacity,comfort and safety,high space utilization,less environmental pollution and other advantages.Urban rail transit makes daily travel more convenient,but it also makes the noise and vibration problems more and more obvious,which affects people’s work and life seriously.Elevated rail transit account for a large proportion of urban rail transit,and its noise influence on the surrounding environment is concerned by more and more people.In this paper,the environmental noise induced by subway on viaduct rail of Chengdu metro line 2 is studied by the means of theoretical analysis,software prediction and field measurement.On the basis of existed studies of domestic and international railway and urban rail transit noise,the field test data of environmental noise induced by subway on viaduct rail of Chengdu metro line 2 was used to verify the applicability of noise prediction software Cadna/A.The propagation law of environmental noise in test section was analyzed.The characteristics of environmental noise and structure-borne noise near the viaduct rail were discussed.The main conclusions of this paper are as follows:1.LAeq of each measuring point is calculated according to the measured noise signal data,the radiation attenuation formula in the horizontal direction of the environmental noise induced by subway on viaduct rail of Chengdu metro line 2 is fitted.These results can be used to simulate environmental noise in similar situations.2.Cadna/A was used to simulate the environmental noise of the measured scene,and the environmental noise induced by subway on viaduct rail of Chengdu metro line 2 is measured.The predicted results are compared with the measured results and the results showed that the prediction effect of Cadna/A is not good and the applicability is not strong within 20m from the centerline of the near track below the rail surface,the predictive value of the software is accurate and the prediction results are reliable beyond 20m from the centerline of the near track below the rail surface.3.In subway transit time,the sound pressure amplitude of environmental noise and structure-borne noise at each measuring point have the same change rule.In the vertical direction,the sound pressure amplitude at the point of 7.5m away from the center line of the track decreases with the decrease of the vertical height.In the horizontal direction,the sound pressure amplitude decreases with the increase of horizontal distance.4.The main frequency range of the environmental noise at measuring point is below 1000Hz when the train passes,and the optimal frequency distribution is concentrated.The sound pressure level of the environmental noise at measuring point reached the maximum value at 800Hz.The main frequency range of structure-borne noise at measuring point is 50～120Hz,and the optimal frequency distribution is concentrated.The sound pressure level of the structure-borne noise at measuring point reached the maximum value at 80Hz or 100Hz.5.The beam of viaduct affects the radiation of sound source,and the spread of noise is greatly affected near the viaduct.The distribution of noise near the beam is more complicated because of the shielding effect of beam on direct sound and the structure-borne noise of viaduct.But at a distance far away from the bridge,the environmental noise is less disturbed by the beam.