In HIDA tunnel, there is clayey crush zone and hydrothermal altered zone continuously. So, the phenomenon of trapping TBM, push out a face in NATM method and increase of inside displacement happens at the refuge tunnel. The hydraulic head pressure which is equal to thickness of earthcovering is cofirmed by boring, as the rock pressure is increasing due to high earth covering which is 400-600m. Therefore we selected the most suitable construction of tunnel supports which match excessive high rock pressure and high hydraulic head pressure, and undertook construction.
