Investigation of effects of dynamic loads in metro tunnels during construction and operation on existing buildings

This study focuses on the vibration effects of both metro (subway) tunnel construction and metro-operating traffic on existing buildings. To that end, a four-story reinforced concrete building located between two metro tunnels of Üsküdar–Ümraniye–Çekmeköy Metro Project (UUCMP) was monitored both during the tunneling stages of construction and after the metro traffic started. Acceleration records were gathered from the building during the pass of two tunnel boring machines (TBMs) just below the building. Both magnitudes of the acceleration and the building frequencies were investigated for the active and passive stages of TBMs. The operation of the first TBM caused an obvious increase in the magnitudes of the vibration measured from the building, while the operation of the second TBM did not show any meaningful increase in the vibration magnitudes. These data were evaluated together with the characteristics of the soil between the building and the metro tunnels. After the completion of the construction, the metro lines were put into service. In this stage, acceleration measurements were gathered to reveal the effects of metro traffic on the studied building as well. It was seen that the metro traffic increased the magnitude of the vibration on the building. Firstly, this study underlined the importance of the soil profile between the tunnels and the studied structures for the propagation of TBM-induced vibrations. Secondly, in both tunnels, daily metro traffic caused higher magnitudes of vibration on the studied building compared with those of the TBMs. In conclusion, TBM vibration data can be used for detecting and determining critical structures in order to take precautions during the construction stage before the metro lines are put into service.