The effect of internal structure on dynamic response of road-metro tunnels under train vibration loads: An experimental study

Abstract

The environmental vibration caused by train induced vibration loads has received considerable research attention. However, the dynamic response characteristics of tunnels with large diameter and complex internal structures, such as road-metro tunnels, remains unknown. In this study, physical model tests have been carried out to study the dynamic response characteristics of road-metro tunnels under train vibration loads and the effect of internal structure on the dynamic response of the tunnel linings and surrounding soils. A road-metro tunnel model (RTM) and a simple tunnel model (STM) were tested under train vibration loads and sweep frequency loads applied to the tunnel invert of each model. The dynamic response of tunnel linings and surrounding soils at different positions were measured by accelerometers and analyzed in both time and frequency domains. The experimental results show that the internal structure can significantly reduce the dynamic response of tunnel linings and surrounding soils. The maximum ratio of the peak particle acceleration (PPA) of the tunnel linings in the two tunnel models is about 275%, while the ratio of PPA of soils in the two tunnel models is greater than 90%. The vertical acceleration level (VAL) of tunnel linings in STM test is always greater than that in RTM test at the near field, whereas for the tunnel linings at the far field, the VAL in STM test is clearly larger than that in RTM test in the frequency range of 80–250 Hz. The difference between the VAL of surrounding soils in these two models is not obvious at lower frequencies (<63 Hz). The obvious dynamic response on the upper lane decks was also studied. The study demonstrates that failure to consider the internal structure of road-metro tunnels can lead to an overestimate of the dynamic response of tunnel linings and surrounding soils and that special attention should be paid to the obvious dynamic response of lane decks.