Curved metro lines currently account for a significant proportion of total route mileage. However, the existing prediction model of environmental vibration only considered the vibration induced by trains running in a straight tunnel. In the present study, a numerical model was proposed to predict the environmental vibration induced by trains running in a curved tunnel. The model was divided into two parts: a train–track coupled model and a tunnel–soil–building finite element model. In the first part, a novel three-dimensional train–curved track coupled model was established and solved in the frequency domain based on the periodic theory. Both vertical and horizontal train loads were calculated by this model. Then, an in situ measurement was performed in the curved tunnel of an operating metro line, and the tunnel vibration responses were obtained and used to calibrate the train–track model. Finally, a case study was selected from Beijing metro line 16, where it is needed to predict and evaluate the environmental impact of vibration from a curved metro line being planned for construction beneath an office building. A three-dimensional tunnel–soil–building finite element model was built, and the building vibrations in vertical and horizontal directions were predicted. The results show that the floor vibrations have peak values of approximately 5.29 and 27.8 Hz, which are exacerbated by the building local mode and the spacing of the rail supports. Below the third floor, the vertical vibration response exceeded the vibration control limit recommended by Chinese national standards. Track solutions for vibration control must be implemented to mitigate the environmental vibrations.

Laboratories with sensitive instruments need a low-vibration environment. It is a challenge to control the train-induced vibration impact on these instruments when a newly planned metro line is adjacent to a laboratory building. An alternative method of mitigating train-induced ground vibrations involves installing measures along the transmission path. Recent research has highlighted the potential of periodic pile barriers with specifically designed band gaps for controlling environmental vibrations. This study performed in-situ measurements of ambient vibrations inside and outside a laboratory containing various types of sensitive instruments and located adjacent to a newly designed metro line. The vibration transfer function of the laboratory was then obtained. To help design and optimize the band gaps of periodic piles, a novel band gap performance evaluation function was proposed. Finally, numerical analysis was conducted to validate the mitigation effect of the designed periodic piles. The results showed that the band gap performance evaluation function can be used to optimize the mitigation effect of periodic piles. The proposed periodic piles clearly attenuated vibrations between 52.4 and 74.3 Hz, especially those at 63 Hz. A comparison of general vibration criteria (VC) curves revealed that vibration attenuation of one level can be obtained by the designed periodic piles.

In railway turnout areas, vertical and horizontal structure irregularities, including geometry and stiffness, result in vibration amplification during the passage of trains. These vibrations can then spread to the surrounding environment. A steel spring floating slab track may be used to control such vibrations, especially in metro-type urban railways. An experimental study was conducted to investigate the vibration-mitigating effects of the floating slab track in turnout areas, and the results were compared with the performance of a regular slab track. Four test cases (consisting of six test sections) were selected: a floating slab track in the turnout zone (consisting of a switch rail section and a nose rail section), a floating slab track in the plain line, a slab track in the turnout zone (consisting of a switch rail section and a nose rail section), and a slab track in the plain line. The vibration characteristics of the floating slab track in the plain line and in the turnout were calculated to explain the test results. The test results indicate that when trains pass across the floating slab track in the turnout zone, the vertical vibration response is close to the horizontal response on the switch rail sections. The use of floating slab track can effectively reduce this vertical vibration. However, the vertical vibration response is much larger than the horizontal response on the nose rail sections of the turnout zone. When the floating slab track is used in these turnout zones, the vertical vibration of the rail decreases while the horizontal vibration increases. Compared to sections using the regular slab track in the turnout zone, the vibration of the floating slab track segments in the turnout zone is shown to be exacerbated, although the vibration level at the adjacent tunnel wall is effectively reduced.