Abstract
Most of binocular tunnels which are composed of two parallel tunnels have been constructed with severe surface condition such as residential areas, shallow overburden and weak ground conditions. According to the data base of the past binocular tunnel works, the predicted final settlement by using field measurements data at first center drift was under estimate than the real one, because of the insufficient analysis considering with the effect of the ground by excavation of the primary section. Therefore, the improvement of the forecasting accuracy become a practical issue for binocular tunnel design. In this study, surface settlements of the binocular tunnel constructed in the shallow overburden was estimated in the every excavation stage. From this result, it is revealed that the scale effect due to the expansion of tunnel width in excavation process and the existence of weak layer of upper ground of tunnel provide that the incremental of surface settlement due to excavation of secondary section is larger than primary section.
