Train-induced vibration is increasingly attracting people’s concern nowadays. In the coastal areas, many metro tunnels are built in the soft deposits, so the train-induced vibration effect is more serious. Nevertheless, the existing research studies mainly focus on the dynamic responses in the tunnel or on the ground surface while vibration characteristics in the ground are seldom studied. In this paper, a comprehensive field measurement was performed by installing accelerometers in the tunnel and soil layers and on the ground surface to capture the response characteristics of the track-tunnel-ground system. Elastoplastic numerical simulation considering the soil-water coupling was conducted to reveal the responses of acceleration, dynamic displacement, and excess pore water pressure using FE code DBLEAVES. Measurement results indicate that high-frequency contents (>500 Hz) attenuate rapidly in the propagation process; the dominant frequency of the rail concentrates in the middle- and high-frequency bands, about 25–400 Hz and 1000–1500 Hz, while the frequencies of the track bed, soil layers, and ground surface drop to below 400, 200, and 100 Hz, respectively. The vertical ground acceleration decreases like an arc in the transverse direction while there is transverse acceleration amplification phenomenon at a distance from the upper haunch and lower haunch of the tunnel. Overall, the area affected by train vibration in the soft deposits is about 30 m away from the metro tunnel. Numerical simulation based on soil-water coupled analysis is feasible to model the vibration characteristics in the soft deposits and confirms that there is acceleration amplification in the ground. Moreover, numerical results indicate that excess pore water pressure can be accumulated during each train vibration, so the train-induced settlement will be a potential problem in the long term for the metro tunnel.

中文翻译：

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软沉积中地铁隧道列车振动的现场测量和数值模拟

如今，火车引起的振动越来越引起人们的关注。在沿海地区，许多软隧道内都建有地铁隧道，因此列车引起的振动效应更为严重。然而，现有的研究主要集中在隧道或地面上的动力响应，而很少研究地下的振动特性。在本文中，通过在隧道和土壤层以及地面上安装加速度计进行了全面的现场测量，以捕获轨道隧道-地面系统的响应特性。进行了考虑土-水耦合的弹塑性数值模拟，以揭示加速度，动态位移和超孔隙水压力的响应，使用有限元代码DBLEAVES。测量结果表明，高频成分（> 500 Hz）在传播过程中迅速衰减。铁路的主要频率集中在中高频和高频带，分别为25–400 Hz和1000–1500 Hz，而轨道床，土壤层和地表的频率则降至400、200和以下。分别为100 Hz。垂直地面加速度沿横向方向呈弧形减小，而距隧道的上半部和下半部一定距离处存在横向加速度放大现象。总体而言，受软振动中列车振动影响的区域距离地铁隧道约30 m。基于土壤-水耦合分析的数值模拟可以用来对软沉积物的振动特性进行建模，并确认地面加速度的增加。而且，数值结果表明，在每次列车振动过程中都可能积累过多的孔隙水压力，因此从长远来看，列车引起的沉降将是地铁隧道的潜在问题。