ABSTRACT
This paper presents the results of study on the application of a large TBM (dia.12.84m) to Hida tunnel, which is the second longest highway tunnel (10.75km long) in Japan. The improved open type TBM, which combines advantages of open type TBMs’ rapid excavation abilities in good rocks and shielded type TBMs’ stable progress and safety work conditions in weak rocks, has been developed in order to suit the geological conditions of the tunnel. The new ventilation system, which uses the lower half section of the bored tunnel for ventilation ducts instead of the shaft, has also been developed for the first time in the world.
