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Large-diameter shield tunnels for metro systems exhibit greater mass compared to conventional shield tunnels, and their vibration source strength is generally considered lower. Consequently, they are regarded as a potentially effective measure for mitigating environmental vibration induced by metro operations. However, large-diameter shield tunnels have limited applications in existing metro lines, resulting in a lack of measured vibration source data. Moreover, their frequency-dependent source characteristics and influencing factors remain unclear, leaving vibration and noise reduction designs utilizing such tunnels inadequately supported. Field measurements were conducted on large-diameter and conventional shield tunnels along the same metro line to compare their vibration source strength and spectral characteristics. A "tunnel-soil" finite element model was established and validated using the measured data. Subsequently, the effects of geological conditions and lining thickness on the vibration source strength were investigated. The results indicate that, under identical train operating conditions, the source strength of large-diameter shield tunnels is at least 7 dB lower than that of conventional shield tunnels, confirming their efficacy in reducing metro-induced environmental vibration. The vibration source amplitude of large-diameter shield tunnels is lower than that of conventional shield tunnels within the low-frequency range (1-125 Hz) but higher at frequencies above 125 Hz. Stiffer surrounding soils lead to increased vibration source strength and predominant frequencies. Additionally, each 10 cm increase in tunnel lining thickness reduces vibration source strength by approximately 1.5 dB, and each 1 m increase in tunnel diameter reduces the vibration source strength by about 1.9 dB. These findings provide a theoretical basis for evaluating metro environmental vibrations and designing vibration and noise mitigation measures.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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