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In order to improve the scientific nature of urban rail transit environmental management, the Environmental Engineering Assessment Center of the Ministry of Ecology and Environment has, since 2021, jointly conducted research on the noise and vibration source intensity and the effectiveness of vibration and noise reduction measures of urban rail transit under different boundary conditions in cities such as Fuzhou, Hangzhou, Suzhou, Guangzhou, Nanchang, Jinan, Nanjing, Shenzhen, Wuhan, and Shanghai in cooperation with a number of design units. The research results are now sorted out for reference by relevant units across the country in related work.
1. Recommendations for selecting noise source intensity values for urban rail transit elevated lines
Tests were conducted on approximately 50 elevated line noise source intensity points, and a total of approximately 500 measured data points were obtained. Recommendations on the noise source intensity values of urban rail transit elevated lines were given for different vehicle types and speeds. See Table 1 for details.
The study found that in addition to the influencing factors suggested in the "Technical Guidelines for Environmental Impact Assessment of Urban Rail Transit" (HJ453-2018), the noise source intensity of elevated lines is also related to factors such as bridge structure, bridge quality, and the noise reduction ability of the vehicle body itself. The selection of source intensity needs to be combined with the actual project.
2. Recommendations on the Value of Vibration Source Intensity for Urban Rail Transit Underground Lines
Tests were conducted on approximately 180 underground line vibration source intensity points, and a total of approximately 16,000 measured data points were obtained. Recommendations on the value of vibration source intensity for urban rail transit underground lines were given for different geological conditions, vehicle types, and vehicle speeds. See Table 2 for details.
The study found that the vibration source strength of underground lines is related to factors such as geological conditions, tunnel structure and form, construction method (shield method, open-cut method, mining method), shield diameter and segment quality. The selection of source strength needs to be combined with the actual project.
3. Recommendations on the noise reduction effect of sound barriers on elevated urban rail transit lines
The effectiveness of a sound barrier can be assessed by comparing noise levels in the barrier's shadow zone (receiving point monitoring values) with those at source-strength locations without a sound barrier, or in the barrier's illuminated zone (reference point monitoring values). Due to practical testing conditions, the noise reduction effectiveness tests conducted in 10 cities, including Fuzhou, primarily focused on monitoring the shadow zone at a location 7.5 meters from the centerline of the outer rail and at the same height as the rail surface, i.e., the receiving point shown in Figure 1. For vertical sound barriers, the reference point is typically set at least 1 meter above the barrier. In practice, monitoring points at varying distances from the centerline of the outer rail and at different vertical heights can be selected based on research needs to analyze the actual noise reduction effectiveness of the sound barrier on sensitive targets at varying distances and heights along the line.
An analysis of approximately 900 data points from more than 60 groups of measured sections of sound barriers was conducted, and recommendations on the noise reduction effects of sound barriers were given. See Table 3 for details.
In addition to being affected by the type of sound barrier, the noise reduction effect of the sound barrier is also related to factors such as the sound barrier material and the quality of the sound barrier construction. When selecting the noise reduction effect value of the sound barrier, it should be further combined with the actual project.
IV. Recommendations on the effectiveness of vibration reduction measures for urban rail transit underground lines
The effectiveness of vibration reduction measures for urban rail transit is evaluated by comparing the difference between the same basic reference points or analog reference points under tunnel wall vibration reduction and non-vibration reduction conditions. The evaluation quantity should be the maximum Z vibration level VLZmax during the train passing period, and the relative insertion loss △VLZmax of the Z vibration level of the vibration reduction measure should be given.
The track conditions (including geological conditions, wheel-rail conditions, track irregularities, track surface condition, tunnel type, etc.), vehicles, and operating conditions of the treatment and control sections should be identical or similar. The distance between the treatment and control sections should be greater than one train length. The distance between the treatment section and the boundary of the treatment should be greater than half a train length. If these conditions are not met, the midpoint of the vibration reduction measure for that section of track should be selected.
The measurement point location of the basic reference point or analog reference point should comply with the relevant requirements of HJ 453-2018 for the selection of vibration source intensity measurement points. At the same time, measurement points should be arranged on the rails and roadbed as a reference.
Drawing on recent experience in urban rail transit environmental management, the research team categorized vibration reduction measures such as double-layer nonlinear damping fasteners and Lord fasteners as medium-level vibration reduction measures; trapezoidal sleepers and rubber floating slab trackbeds as advanced-level vibration reduction measures; and steel spring floating slab trackbeds as special-level vibration reduction measures. An analysis of approximately 33,000 data points from nearly 190 sets of measured sections of various vibration reduction measures resulted in recommended values for vibration reduction effectiveness at different levels of vibration reduction measures, as detailed in Table 4.
In addition to being related to the level of measures, vibration reduction measures for underground lines are also related to many factors such as geological conditions, track joint treatment, turnout conditions, project implementation quality, the health of tracks and vibration reduction measures, etc. When selecting the effectiveness value of vibration reduction measures, it should be further combined with actual conditions.
Source: Environmental Engineering Assessment Center of the Ministry of Ecology and Environment. If there is any infringement, please contact us to delete it!