Field Measurement and Research on Environmental Vibration due to Subway Systems: A Case Study in Eastern China

Abstract

With the rapid development of subway systems, the negative environmental impacts of vibration induced by subways has gradually become a research hotspot. For the purpose of developing predictive models of vibration and designing effective vibration mitigation systems, continuous field dynamic measurements were conducted simultaneously in a subway tunnel, ground, and building in eastern China, the most prosperous region in China. The characteristics of vibration transmission and attenuation induced by subway were analyzed by statistical analysis of large amounts of measurement data. The results showed that most prominent and visible attenuation of vibration is from the track to the ballast bed in the tunnel, where the ground-borne vibration would quickly decrease exponentially with distance. The results also showed that the measured attenuation value of indoor vibration was approximate 0.76 dB on average between each floor. Moreover, the decay ratio of the vibration increased with the increase in the frequency range. Based on these findings, construction gauge of 20-25 m outside of the tunnel is recommended. In addition, reducing the vibration source excitation intensity is the most effective vibration isolation method, especially by track structural transformation. Sustainability 2019, 11, 6835 2 of 12The subway vibration effect on the surrounding environment is not only related to the tunnel structure, stratigraphic characteristics, and building structure, but also to the track and train [9]. Therefore, unlike vibration induced by other sources, such as airplanes, ground traffic or industrial machinery, vibration induced by subway has certain distinctive characteristics, such as low frequency, persistence, and longevity. Thus, more theoretic analysis and field measurements of the vibration induced by subway are also needed to determine causes, characteristics, and its effects.Among the various research methods, the numerical simulation is widely used to predict the environmental influence of vibration induced by subway [10]. Unfortunately, all the simplifying assumptions used in numerical models of ground vibration induced by subway could result in maximum errors of ±10 dB in predictions [11]. Although field measurement involves a lot of data collection and analysis, it is the most direct and reliable method in studying subway vibration propagation. Field measurement is also the only way of verifying the accuracy of other methods, especially when it comes to locally applicable ones [12][13][14].Although there have been many studies on subway vibration worldwide [8], further field measurement studies, specific to vehicle-track excitation source and vibration propagation, are still required. In this study, in order to ascertain the characteristics of vibration transmission and attenuation induced by subway, and to predict the environmental influence of subway train-induced vibration on ground and inside over-track buildings, the continuous dynamic measurement was conducted simultaneously in the subway tunnel, grou...

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