The Pollution Control of Urban Elevated Railway Traffic Noise Liu Yunfang South China Institute of Environmental Sciences. MEP, Guangzhou 510600, China. Deng Xi South China Institute of Environmental Sciences. MEP, Guangzhou 510600, China. Dong Lin South China Institute of Environmental Sciences. MEP, Guangzhou 510600, China. Zhang Yuhuan South China Institute of Environmental Sciences. MEP, Guangzhou 510600, China. Qian Donglin South China Institute of Environmental Sciences. MEP, Guangzhou 510600, China. Summary The direct noise and the radiation structure noise of the urban elevated railway bring bad impacts to the residents along .Taking the 14th railway transit of Guangzhou as case ˈ the paper analyses characteristics of railway traffic noise source ˈ emission characteristics ˈ common measures of pollution control and the disadvantage, and advances suggestions. Key words urban elevated railway transit˗noise˗pollution control 1. Introduction Compared with underground line, the elevated line surpasses in construction cost, construction At present, China is facing many problems in duration and operation maintenance. However, the urban traffic such as serious shortage of road latter has been more and more restricted for its capacity, resource consumption and severe traffic vibration and noise pollution due to its exposure to pollution. Urban rail transit (URT) is characterized the environment. For Line 4 of Guangzhou, for by large capacity, fast speed, safety and high example, as the only elevated line in operation reliability, punctuality and comfort, and surpasses where the elevated section of 48.26 km accounts in promoting development of relevant industrial for 69.3% of the total length, all the affected chain, speeding up urban region integration, domiciles within 10 m from the center line of track mitigating energy shortage and urban air pollution, have been relocated against vibration and noise. improving traffic efficiency and safety, etc.Ǐ1ǐ With the complete implementation of According to the statistics of China Association of Construction Plan for Guangzhou Mass Transit in Metros, by the end of 2013, there had been 87 2015, the elevated lines will account for 30% of URT lines constructed and put into operation in 19 the total length, of which the planned Line 14 cities around China, with total operation length of (including branches) will have elevated line of 2539 km. According to Plan for Comprehensive 70.7 km, accounting for 97.1% of the total length. Traffic System over the 12th Five-Year Plan, by Therefore, if vibration and noise problems brought the end of 2015, the constructed length of URT in by such elevated lines are not solved, the China will reach 3000 km.DŽ development and use of land space along the lines In Guangzhou City, six URT lines of 211 km have will be probably restricted, hence further been constructed and put into operation, namely, compromising the application and promotion of Line 1, Line 2, Line 3, Line 4, Line 5 and Line 8. elevated lines. Besides, there are 3 lines under construction, i.e. northern extension line of Line 3, Line 6 and 1.1 Noise Source of Elevated Lines extension lines of Line 2 and Line 8. According to The radiated noise of urban elevated rail transit Construction Plan for Guangzhou Mass Transit in includes wheel/rail noise, noise from vehicle 2015, the total length of URT lines after equipment, noise from vehicle body during completion in Guangzhou will reach 630.4 km. operation, and noise from viaduct structure.Ǐ2ǐ Copyright© (2015) by EAA-NAG-ABAV, ISSN 2226-5147 1683 All rights reserved Y. Liu et al.: The Pollution... EuroNoise 2015 31 May - 3 June, Maastricht (1) Wheel/rail noise especially when the viaduct goes through densely Wheel/rail noise exists in 3 forms: first, squeal populated areas. According to statistics, when the arisen from cutting and friction when the vehicle vehicle travels on a viaduct, the noise will increase travels on a curve or wheel/rail hard bending; by 2~10 dB. Ǐ 5 ǐ It is reported that the viaduct second, clash due to rail joint; third, “rumble” due structure of light rail in London Docklands has to uneven contact between wheel and rail. caused severe radiation of low-frequency noise, (2) Noise from vehicle equipment especially at 63 Hz octave band, which causes Noise from vehicle equipment includes noise of noise nuisance to residents along the line. traction motor, noise of gear box, noise of air compressor, noise of air conditioning and 2.2 Wheel/rail noise refrigeration equipment, brake noise, vehicle Ballastless track structure is commonly used for traction noise, electrical noise, noise of pantograph, elevated lines at present. On monolithic ballastless aerodynamic noise during vehicle operation, track, the steel rail is directly fastened to the track whistling noise and those from untight doors or connected to the viaduct, and since in this case the windows. Among them, traction motor, gear box attenuation rate of vibration along steel rail is and air compressor are main noise sources. smaller than that in the case of ballast track, the (3) Noise from vehicle body during operation vibration of steel rail is 5~10 dB higher, thus the The noise radiated from vehicle body due to radiated noise of steel rail is also greater. vibration and secondary radiated traction noise Meanwhile, since some special rail fasteners are through vehicle body are of intermediate and low used for elevated lines, rail corrugation and other frequency characteristics. Air acts on the surface serious irregularity defects may arise, resulting in of vehicle body where gas viscosity causes much noise radiated along steel rail of elevated negative pressure change, which produces surface lines than that along steel rail of ground lines. vibration, and generates vortex flow and friction and impact, hence the formation of high-frequency 3. Law of Noise Transmission pneumatic noise. (4) Noise from viaduct structure For traffic noise, within the range of certain Structural noise is generated when a vehicle distance from the vehicle, the vehicle can be traveling on the viaduct structure transfers regarded as a line source. vibration to rail and base structure through / / OJU U / wheel-rail contact, resulting in deck vibration S S hence secondary low-frequency noise. ˄1˅ 2. Characteristics of Noise from Elevated Where, / üsound level produced by the line Lines S source and measured at the prediction point According to the survey, the urban rail transit in (octave band sound pressure level or A-weighted China generally operates at 60~80 km/h, and sound pressure level); wheel/rail noise contributes most to the total sound pressure level with frequency band to which / üsound level at the reference position r0 of human ears are most sensitive. The sound energy S of wheel-rail noise mostly lies in broadband over line source; 250 Hz and usually its peak exits between rüvertical distance between prediction point and 500~1250 Hz. When the vehicle travels at the line source; speed less than 80 km/h, the structural noise will r0üvertical distance between where the reference become the main source of noise. The structural sound pressure is measured and the line source; sound energy lies in the broadband below 250 Hz / üvarious attenuations, including those caused with the peak sound pressure existing between Ǐ3ǐ by air absorption, sound barrier or obstruction, and 40~125 Hz. ground effect. 2.1 Structural noise 4. Vibration-noise Control Technology for 2~10dB Noise of viaduct structure has greater Elevated Rail Transit effect for its low frequency, slow noise attenuation, high elevation of sound source, farther From the analysis on noise sources, we know that transmission distance and broader influence area, the noise of elevated rail transit is closely relevant 1684 EuroNoise 2015 Y. Liu et al.: The Pollution... 31 May - 3 June, Maastricht to vibration. The vibration damping measures for track (4) Main technical parameters structure mainly include elastic fasteners, low Number of Main Double-line vibration track, floating ladder track and floating Lines slab track. The noise reduction measures for Section and station line: 8000 Minimum radius vehicle mainly include resilient wheel, m /4000 m; assistant line: 2000 of vertical curve noise-reduction wheel, composition brake shoe, m regular grinding of wheel tread, timely and Main line: normal: 800 m; adequate application of lubricant to wheel/rail poor case: 550 m; special Minimum radius contact part, installation of lateral elastic coupling case: 300 m of plane curve device between front and rear bogies, sound proof Assistant line: normal: 250 m; apron and so on. The noise reduction measures for poor case: 150 m track mainly include low vibration track, apposite Main line: normal: 30‰; Maximum grinding of rail surface, using seamless heavy-duty poor case: 35ă; assistant line: gradient rail, reasonable setting of support stiffness of rail, 40‰; station: 2‰ application of oil to rail surface, setting of sound (5) Track barrier, etc. Gauge of 1435 mm 5. Examples of Noise Reduction Practice of track First Construction Stage of Guangzhou 60kg/m steel rail for main line, Mass Transit Line 14 (Including Branches) Steel rail entrance/exit depot line and testing line, 50kg/m steel rail for other lines. 5.1 Project overview Fastener Separated elastic fasteners. (1) Profile 60kg/m No. 12 or 60kg/m No. 9 curved point rail switch for main line The first construction stage (Jiahewanggang ~ Switch Jiekou) of Line 14 of Guangzhou mass transit is and assistant line, No. 7 switch for 54.1 km in length with 13 stations, of which other lines. underground line is 15.6 km, and ground line 38.5 Reinforced concrete monolithic km. Knowledge City Branch, with 7 stations and track-bed for main line and assistant full length of 21.8 km including underground line Track line.