# Research on Environmental Vibration Induced by High-Speed Maglev Transportation
## 1 Introduction  
In recent decades, with the increasing pressure of traffic congestion and environmental conservation, it has become necessary to encourage the development of public transportation, and the development of maglev transportation offers a new form of convenient high-speed urban railway transit. The maglev transportation system utilizes magnetic force to provide contactless suspension, guidance, and propulsion. Thus, it reduces most of the mechanical friction and a large number of moving parts in the train [1]. Compared to the traditional forms of rail-wheel transportation, the maglev system has the advantages of lower noise and vibration, better curve negotiation and grade abilities, higher reliability, and lower maintenance costs, giving it potential for high-speed and long-distance transportation or transits across the city. There are two major forms of magnetic levitation, utilizing either the attractive force between iron-core electromagnets and ferromagnetic rails or the repulsive force between superconductivity magnets and induced electric currents in conductive guideway components [2]. The former is known as electromagnetic suspension (EMS), and the latter is called electrodynamic suspension (EDS). EMS is the only form of suspension utilized in commercial maglev lines, such as the Shanghai high-speed maglev demonstration line, theChangsha medium-speed maglev line, and the urban transit maglev (UTM) in the Republic of Korea [3]. In the EMS system, the suspension of a maglev train is maintained by an active, controlled attractive force. To maintain a steady state, levitation relies on the conscious adjustment of the suspension force. Even when a maglev train is suspended statically on the guideway, the train and track still vibrate under the constantly changing force; this kind of coupling vibration is the most significant difference between maglev and traditional wheel-rail transportation, and modeling and controlling the vehicle-track vibration are still key and difficult points in maglev transportation studies. During the running of a maglev train, the vehicle and railway track constantly vibrate and propagate the vibration to the surrounding environment, which affects the surrounding environment and may cause serviceability problems or even vibration pollution. When the vibration in a building is large enough or lasts long enough, people will perceive the vibration and feel annoyed, uncomfortable, or even panicked, eventually causing huge economic losses [4]. The transmission of traffic-induced vibration may have the potential to cause damage to surrounding structures, especially heritage buildings [5] and previously damaged buildings [6]. Even if the vibration is not large enough to cause damage, excessive environmental vibration may also affect instruments' accuracy in nearby laboratories and factories [7], such as at Peking University, where equipment valued at CNY 400 million was affected by the opening of underground line 4. Therefore, it is necessary to study the vibration effects of maglev transportation. In past decades, researchers have studied in detail the vibration effects of wheel-rail transportation. [PERSON] et al. [8] conducted field tests and discovered that surface waves rather than longitudinal or transverse waves occupy the main components of vibration caused by railway traffic; the vibration magnitude under a 2 m depth is only 20-50% of that on the ground surface and reduces to 10-20% at a 4 m depth. [PERSON] et al. [9] conducted an in situ test and an analysis of the environmental vibration induced by urban subway transit and found that the amplitude of the vibration vertical to the ground is higher and attenuates more slowly than horizontally. Moreover, there exists a vibration-amplifying zone at a certain distance from the subway track. The position of the zone is determined by the geological condition, depth of the tunnel, and mechanism of vibration, and an attenuation formula was proposed to predict subway environmental vibration. [PERSON] et al.