Prediction Of Environment Vibrations Induced By Metro Trains And Mitigation Measures Analysis

With the rapid development of the urban rail transit system and the constructing of buildings, it is of common occurrence that metro lines are near the buildings where installed sensitive instruments. Accordingly, it is unable to avoid the vibration effects on sensitive instruments induced by metro trains, which needs special researches.Based on Beijing Metro Line 4 passing through under the Peking University science tests, the characteristics of vibration resource, ground-surface vibration propagation regular, performance of SSFST, and vibration prediction have been researched roundly in this paper. The research methods include in situ measurement, numerical simulation, model test, theoretical analysis etc. The conclusions are universal, which can supply references to the related researches. The main work and the achievement are as follows:The present states of vibration mitigation design and application in Beijing metro line were summarized roundly, and the technical parameters of mitigation measures for more and the most sensitive areas of new metro lines in Beijing were obtained, including length ratios, investment ratios, the application of SSFST and so on.The in situ measurements were carried out inside and outside the Physical Laboratory, on the ground surface and in the running tunnel between Dongdan station and Jianguomen station, and in the running tunnel between Dongdan station and Dengshikou station. According to the measured data, the background vibrations of the Physical Laboratory and the existing metro line were evaluated; the ground-surface vibration response characteristics induced by metro trains, by road traffic and by their combined action were analyzed; and the vibration resource characteristics of the unisolated track and SSFST were obtained, with which the train loads were simulated.The vibration characteristics of the stratum, the tunnel structure and the tunnel-soil system were researched, and some issues were analyzed in detail, including the differences of vibration performance between the discrete numerical model and the continuous media, the damping treatment, the integral step determination and the choice of artificial boundary. Besides, the simulated train loads were transformed for using in the finite element model. Finally, a dynamic finite element model corrected by the measured data was established to simulate the ground-surface vibration induced by metro trains between Dongdan station and Jianguomen station, and the compared results between the calculated and measured data proved that the treatment of relative parameters, the boundary and the train load were credible.The 1:1 scale model vibration tests were carried out for the case of the unisolated and the isolated track in the UTEL of Beijing Jiaotong University. Based on the test data, some major parameters of SSFST were analyzed, such as the working frequency, the frequency characteristic of vibration mitigation, and the attenuation regular. Besides, the transfer coefficient and the vibration decrement of key point in the transmission path were given, which were in the range of 5Hz and 15Hz.On the assumption that Line 4 were operating, the environment vibrations of the Peking University were predicted for the case of the unisolated and the isolated track. By analyzing the mass effects on the ground-surface vibration of the track and the tunnel, the comprehensive proposal for the metro tunnel north of Chengfulu station were presented, including type of the running tunnel and the track, and other mitigation technologies.