Abstract
Due to the limited underground space in the city, it is inevitable that the new subway may undercross the existing subway during the construction process. The current research mainly focuses on the dynamic response of single tunnel or the construction mechanics and ground motion response of tunnels with short-distance, while there is little research on the dynamic characteristics of subway tunnels undercrossing the existing subway with zero-distance. Therefore, in this paper, relying on a subway tunnel closely undercrossing the existing Line 1 with zero distance in Chengdu, using on-site test and numerical calculation, the vehicle-induced dynamic response characteristics of the new subway tunnel is analyzed under the moving train load of the existing Line 1, and the dynamic response differences of the new subway tunnel under different vehicle speeds and operation modes of the existing Line 1 is also discussed. The results show that the relationship between the acceleration of each part of the new subway tunnel is: roof > the middle wall > side wall > floor. For the horizontal acceleration, since the thickness of the side wall is larger than that of the middle wall, and the difference in the boundary constraints between the middle wall and side wall, the acceleration peak value of the middle wall is larger than that of the side wall. The dynamic response of the new subway increases with vehicle speeds, and the increasing rate of the vehicle speed in the range of 40–60 km/h is greater than that of 60–80 km/h. Compared with one-way operation, the two-way meeting has a certain superimposed effect on the acceleration response of the new subway tunnel and has the greatest impact on the acceleration response of the middle wall. The Fourier acceleration spectrum shows the strongest response around 60 Hz and 130 Hz. It is also found the operation of existing subway has adverse impact on the new subway, and certain vibration reduction measures should be taken to ensure the stability of new subway.
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