Japan Atomic Energy Agency has been excavating three deep shafts through soft sedimentary rock in the Horonobe Underground Research Laboratory. In this paper, the authors discussed change in stress and the stress distribution in a concrete lining and steel arch ribs induced by the 6.5 m diameter shaft sinking. They conducted not only field measurements of stress in support elements at a depth of around 220 m but also three-dimensional numerical analysis which models the shaft excavation procedure such as timing of installation of support elements and setting and removal of a concrete form. As a result, it was clarified that more than 10 MPa difference in circumferential stress occurred in a 2 m high and 400 mm thick concrete lining due to anisotropy of initial stress and three-dimensional effect of an excavation face. It was also found that a concrete lining gradually deformed from an original cylindrical form to a shape of an ellipsis with the long axis pallarel to the direction of the minimum horizontal principal stress after a concrete form was removed.

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 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.

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